AudioCircle
Other Stuff => Archived Manufacturer Circles => AudioKinesis Loudspeakers => Topic started by: Duke on 22 Sep 2007, 05:47 am
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Have you ever wondered why someone doesn't make a speaker with a particular combination of characteristics?
Suppose you could bend the ear of a speaker designer - what would you tell him the audio world (or at least your corner of it) stands in need of?
Greater tube-friendliness? Deeper bass in a smaller package? More bang-for-the-buck? More artistic styling? Different sonic emphasis? What isn't being done that you think ought to be?
I don't know where this thread will go, but maybe it will be a useful dialogue between designers and enthusiasts. And since it's on an open forum, this won't be my own secret market research - anybody can read or participate, and potentially benefit from the discussion.
If we end up with a fairly well-defined concept that I think I can build, and if there's interest, I'll at least take it to the prototype stage and discuss it with ya'll as I go along, getting your input.
So... tell me whatcha want!
Duke
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Grand idea for a thread topic :thumb:
What do you guys think of this?
The challenge: High end sound, extreme minimalism. No cables, no boxes, no entertainment units or shelving. Nothing but two beautiful speakers. Two towers, two clean wires out the back you plug in the wall. That's it
Built into each speaker would be a squeezebox, the amps, etc. The squeezebox display would be tastefully integrated into the front of each speaker so you could see what's playing. Absolute minimalism, deadly clean. Zero clutter.
They'd sell. I know Bang & Olufsen get close to this idea, but they don't really nail it.
To us, hifi rigs are beautiful, but to many, it's an ugly room of cables and boxes and it looks dreadful. Two towers, two wires, amazing sound. Design and architectural magazines would be all over them.
/A
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Hello Duke....
Good idea for a thread... :thumb:
Having heard a few speakers, I'm listening first for a solid foundation...bass wise.
If the sound is thin...then it doesn't appeal to me....guess my personal taste.
Thats not to mean "bloated bass"....solid bass...clear.
Also....a higher-efficiency is better....more amps to choose from when looking for power.
And....sound stage....wide/open sounding....not a closed in sound.
Those are a few things that I would enjoy.... :wink:
Chris
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Hi AdamM,
Thanks for the vote of encouragement.
Great concept! You're thinking ahead of the rest of the industry.
In addition to the AC power cords, wouldn't we need an umbilical connecting one speaker to the other? Otherwise, assuming the program material is being played in the right speaker, how does the left channel signal get to the left speaker? Or, am I missing something?
Unfortunately for me, what you describe is beyond my technical ability - but it's probably the wave of the future. Geeze - I hope Boze doesn't read this thread before some serious audio company does!
Duke
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Hello LoneWolf,
Again, thanks for the thumbs-up.
"Having heard a few speakers..." No kidding??
Seriously, thanks for your input on getting the foundation right. Yup, there are a lot of speakers out there that have really good "icing" but the "cake" isn't right.
If you get a chance to stop by my room at RMAF (room 1100), I might have something new that does a pretty good job in the "openness" department as well. I haven't gone public with it 'cause it's not finished yet, but the workshop prototype was promising.
Duke
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wouldn't we need an umbilical connecting one speaker to the other?
While a little 'wasteful' - you could use two squeezeboxes and just employ the one output for each side. An unused channel on each one, sure, but now there's zero wires between them.
I'm not certain you can even use two squeezeboxes simultaneously like that... but i'm sure it's figurable outable
Oh i hope Bose doesn't do it first :)
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"Having heard a few speakers..." No kidding??
I thought you'd like that.... :jester:
See you in room 1100 Duke..... :thumb:
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Very timely post Duke....as far as I'm concerned :)
I was just thinking about the speakers that would use a wide range driver (Fostex...) to cover the 100-5,000Hz range, no crossover, than woofer for below 100Hz (just an inductor in the crossover) and supertweeter for above 5 or maybe 7 or 8kHz (with only a capacitor in series). The frequencies are pretty arbitrary but a good designer can easily determine exact numbers. Maybe there is a speaker like that, I'm just not aware.
My guess is that below 100Hz and above 5kHz phase shift may not matter that much and the Fostex (or others) are covering the range where the ear is most sensitive. Also "beaming" could be avoided by having supertweeter.
Would that make sense? :scratch:
Boris
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I'd like to see more products that incorporate battery power into their design. I am a huge fan of Vinnie's products and the batteries have a large part to do with that, it is very nice to not worry about AC issues or power cords and it just seems to be a simpler and cheaper way to power a system. Obviously there are power limits when using batteries, but with sensitive speakers which I use this isn't an issue.
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Grand idea for a thread topic :thumb:
What do you guys think of this?
The challenge: High end sound, extreme minimalism. No cables, no boxes, no entertainment units or shelving. Nothing but two beautiful speakers. Two towers, two clean wires out the back you plug in the wall. That's it
Built into each speaker would be a squeezebox, the amps, etc. The squeezebox display would be tastefully integrated into the front of each speaker so you could see what's playing. Absolute minimalism, deadly clean. Zero clutter.
They'd sell. I know Bang & Olufsen get close to this idea, but they don't really nail it.
To us, hifi rigs are beautiful, but to many, it's an ugly room of cables and boxes and it looks dreadful. Two towers, two wires, amazing sound. Design and architectural magazines would be all over them.
/A
Im going to get pretty close to that in my living room with a Meridian 808 and a pair of their 7200 active speakers.
Not much clutter at all and great sound!
No one will ever put a squeezebox inside speakers, because when one thing goes you will be without the whole system, but its a great thought!
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On the speaker side, I'm with Lonewolf, slightly higher sensitivity, minimalist design.
Like Chris I've heard lots of speakers. Many that claim to be tube friendly really aren't. Sure they have a Zobel in it to show a flatter impedance to the tube amp but every Zobel I've heard sucks the life right out of the sound.
If I had a research budget and loads of time to experiment I would construct a speaker like this;
First and foremost, use a 1st order XO. A simple cap and coil, no more, no less (unless you want to do the Zu and Infinity trick letting the woofer run wide open then cap a tweeter into the -6db point). If the designer does a good job of picking a driver that rolls off evenly and doesn't exhibit nasties at cone breakup on the upper frequency extremes, there is no reason you can't use a simple 1st order XO on the woofer (assuming it sounds good above 2.5k or so). The tweeter is less of a concern. Just push the XO frequency up a bit to handle the -6db slope and you'll have a decently flat XO point. Next, I'd position the drivers or construct the cabinet so that you have a minimal issue with baffle step compensation. Again, taking a notch filter out of the signal chain will keep from sucking up precious tube (and SS) power.
Sensitivity isn't crucial but I think its important. Something around 92 would be a good baseline for starters. You could always go with an MTM or an MMT design to increase the output assuming the tweeter is up to it (lobing issues aside). Reason I say this is that the majority of tube amps out there are 20+ watts. With 92+db and assuming you have decent output iron on the amp, you will drive them to very comfortable listening levels in a moderately sized room.
When it comes to cabinet design, I've recently listened to some very good sealed cabinet designs. They go deep enough that many people wouldn't require a sub. The plus side of this issue is that it should help in reducing the impedance peaks and phasing issues in a ported cabinet. As part of the overall design, the speaker needs to maintain less than (about) a 50ohm impedance peak. This will present a much easier load for the tube amp thus making it completely unnecessary to install the life sucking Zobel. The sealed cabinet isn't absolutely necessary, if you can extend the bass an octave or two without causing too many negative issues with the tube amp, all is well. A transmission line is an option too.
Think absolutely old school here. Designs and manufacturers like Dynaco, Advent, KLH and others didn't over design their speakers. They used common sense to produce speakers that worked well with tube amps. Sure, some of them used 2nd order XO's which aren't horrible but it does add a tremendous expense to the speaker (if you use quality parts) plus it does suck just a bit more life out of your speaker (more parts=less life). Granted, the speakers and passives of the day didn't sound all that terrific but any amp of the day would drive them without a problem.
Even though speaker technology has advanced, not many 'designers' have figured out all they have to do is look to the past to come up with a good sounding speaker. They all want to come up with some new fangled approach to crossover design that they can tout as 'inventive' or 'novel' and use as ad copy to sell their product. I know, I know, I just made a wide sweeping statement that doesn't hold true in every instance.
The KISS principal is all you need to succeed, honest. It will take work. Nowadays, it seems that speaker designers and manufacturers are far less concerned about a speakers interaction with a tube amp because they know if they put enough bandaids in the filter circuit, they can get it to measure flat.
Oh, when you test your tube friendly speaker designs, don't use some monster 150wpc tube amp. Try a simple push pull EL84 design with reasonable output iron and very little NFB. If it works with this amp, it will work with nearly anything.
....sorry for the (sort of) mini-rant against conventional speaker designers. sure, if you are using solid state, you have no issues because it can handle the extra load seen by the speaker but so few actually design speakers specifically for tube amps. if they really understood the interactions, there would be a wider selection of truly tube friendly transducers out there.....but then again, I just ranted some more........sorry :oops:
..just my $.02 from a grumpy minimalist :green:
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I'd like a line array that doesn't need a sub.
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Somewhat along the lines of Scott's post....
1) smooth impedence; ( 8 ohm min.)...low reactance
2) acoustic suspension design
3) no larger than 1 cu. ft
4) can actually be used with a grill cloth attached :o
(We probably don't see many acoustic suspension speakers anymore because most 'off-the-shelf drivers' have the wrong T&S 'specs' to be used that way; and because people have become accustomed to the sound of a reflex loaded speaker.)
Easier said than done, right?
WEEZ
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Somewhat along the lines of Scott's post....
1) smooth impedence; ( 8 ohm min.)...low reactance
2) acoustic suspension design
3) no larger than 1 cu. ft
4) can actually be used with a grill cloth attached :o
(We probably don't see many acoustic suspension speakers anymore because most 'off-the-shelf drivers' have the wrong T&S 'specs' to be used that way; and because people have become accustomed to the sound of a reflex loaded speaker.)
Easier said than done, right?
WEEZ
Yea... a true 92db/1W/1M type of loudspeaker in a sealed box design of that size would get you to about 180Hz f3. ;-) Those laws of physics are a real bitch.
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Except, Kevin, I don't care about 92db sensitivity...I was carefull not to mention that :)
WEEZ
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I'm just being PIA. If you don't care about how sensitive it is you can pick an F3 & box size and back calculate the driver parameters needed. You also have to consider if your going to use some sort of baffle step compensation which eats another 3-4db of output below the baffle step. Other than that the T/S parameters are very accurate for low frequency output of a sealed box system.
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Wow, what a great collection of replies! Thank you all so much! This may take me a while (have lots to do today), but I want to respond to each of you.
First, to Boris/Audiovista:
I think your idea is great! Using a "fullrange" driver but providing subwoofer and supertweter is a very appealing concept. Actually, my first commercial loudspeaker was exactly that, and while it was hardly a screaming success in the marketplace I may well revisit the concept some day.
My first commercial speaker used two 8" Fostex drivers in a sealed bipole configuration (much better power handling than using one in dipole), along with a built-in powered woofer section to handle the bass below 140 Hz or so. The high frequencies actually held up pretty well on-axis, so I added a rear-firing supertweeter to augment the high frequency balance in the reverberant field. A front-firing supertweeter that kicked in a little north of 10kHz was an option.
The Fostex driver had a peak around 6 kHz, and I used a notch filter to smooth it out. Notch filters are controversial, but I think I've found a way to keep them from sucking the life out of the sound. One of the three components is especially critical when it comes to sound quality.
Because I was "cheating" by using a powered woofer section and a bunch of rear-firing drivers, I called my speaker the "Cheetah". Here's a link to a little write-up:
http://www.sonicflare.com/archives/vtv-expo-audiokinesis.php
And, a comment from someone who heard 'em (near the middle of this post):
http://www.audioasylum.com/audio/general/messages/410442.html
Okay, that was the good news. Now here is the bad news about the format:
If you crank the volume level up and/or hit the speaker with complex orchestral or choral passages, the midrange clarity and articulation isn't very good. Possible reasons for this are small linear x-max on the Fostex driver (1.5 mm, and I think that's one-way); dynamic flux modulation in the motor; intermodulation distortion of the higher frequencies; and diffraction or break-up associated with the wizzer cone.
So I had a speaker that sounded great at low volume levels, great with most music at medium volume levels, and pretty much sucked at high volume levels. I tried raising the crossover point to make life easier on the Fostex drivers, but that didn't make much difference. Finally the woofer I was using was discontinued, calling for a major redesign. The result was a speaker that was bigger and more expensive than the origial, but was outclassed in dynamic capability by most of its competition.
Now all of that being said, I may revisit the concept in a simpler, less expensive package if I can figure out a way around the problem of congestion in the midrange as the music becomes demanding. I suspect that flux modulation is the main culprit, as I've heard very similar coloration with another woofer, and the coloration disappeared when the motor was changed to a version with a Farady ring. Unfortunately I don't know of any low-priced fullrange drivers with low-flux-modulation motors, and fullrange is the applicaion in which flux modulation is most likely to be audible.
I still have a pair of the revised version, which uses a single 12" sealed-box woofer, in case you'd like to try 'em out. If you might, shoot me an e-mail or message.
Thanks for your suggestion, and let me know if you have any questions or follow-up ideas.
Duke
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Hi IronLion,
I take it you're referring to an active speaker that runs off of a rechargeable battery? Hmmm.... if you had let's say two sets of quick-charge lithim batteries, I can see how that could work - assuming one set could charge up quicker than you could run the other set down.
This is beyond the scope of what I do, but I think it could be done by a company with sufficient resources.
Thanks for your suggestion!
Duke
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Hello Jeff/Tonepub,
Thanks for your input! Yeah I shoulda thought of Meridian - and hopefully if AdamM's ultraroomfriendly format goes into production it'll be Meridian and not Boze that does it.
It has been a long, long time since I really sat down and listened to a Meridian system. They made one of the best little speakers of its era - the active M2, from the early 80's. Boy those little suckers could punch and image.
Hey I have always enjoyed your stops by my room at audio shows - great to see how well your magazine is doing!
Best wishes,
Duke
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Hey there Duke:
Good to see you out here, it's a nice group!
I won't be at RMAF this year, due to some family issues, but definitely
at CES...
How is your speaker coming along....
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Hi Scott F.,
Wow, what an in-depth post! Thank you so much for taking the time and sharing your speaker vision with us. I suspected that there were some closet speaker designers out there with some excellent ideas.
I have built speakers with and without impedance compensation circuitry, and my experience doesn't entirely parallel yours. Note that you can't just slap a Zobel into a circuit - the circuit has to be designed as a whole (without cutting corners), then measured, then refined, then measured, then refined... and then listened to with fresh ears. And if it's not right, find out why and start from there. Adding a Zobel will indeed suck the life out of the sound if the whole circuit isn't re-designed taking everything into account.
Now it's pretty easy to build a speaker optimized for a given tube amp with a high output impedance, but unless that speaker's impedance curve is quite smooth the tonal balance will be wrong with a different amplifier. I found this out the hard way. Designing a speaker that retains the same tonal balance with a wide variety of amps is not easy. If a multi-way speaker is going to work well with a wide variety of amplification, I think that some sort of impedance compensation will probably be called for - even it it's just in the component values chosen rather than in an obvious Zobel.
For the record, my 92 dB "tube-friendly" speakers are being used with a zero negative feedback 2a3 SET amp by one of my customers, and he's coming from hotrodded Klipsch LaScallas. I showed with a very low feedback, 30-watt OTL amp in one room and a 5-watt zero-feedback SET in another at last year's RMAF. In the latter room we did manage to clip on very loud solo piano passages, but other than that no problems. So I think impedance smoothing can be overall beneficial if done right.
I have built several speakers with first order crossovers, and here is one hurdle they present that is seldom mentioned: It's difficult to get a smooth power response and a smooth on-axis response at the same time with a first order crossover. Personally, I place the higher priority on the power response.
Here's the problem: Assume we have a driver that's behaving as a piston. Above the frequency where the driver's diameter is equal to about 1/3 of a wavelength, the driver's power response begins falling at 6 dB per octave (assuming flat on-axis response). Now if we only used drivers below the frequency where their diameter was equal to 1/3 wavelength, hmmmm.... I think there might be a window of opportunity here.
One possible issue is this: With a first-order crossover, the drivers will have output way above the crossover point, so any narrowing of radiation pattern up there will still have an effect on the power response. Still, I think this approach has promise.
Regarding enclosure design, I have nothing against sealed boxes but the woofers whose midrange performance I like tend to be woofers that work best in vented boxes. Also, with a vented box it's possible to tailor the shape of the low-end esponse curve to take into account the speaker's acoustic environment. For example, I incorporate variable port length into my designs, and as a result the bass tuning can be optimized for a very wide variety of acoustic conditions. Personally, I prefer tuning well on the low side, trading off some extension for a more natural sound with better pitch definition. Offhand I don't know of any 92 dB efficient woofers that will give you decent bass extension in a sealed box, though there are probably some out there.
I would rather not use multiple drivers over the same frequency range as it causes the power response to start falling sooner because the drivers increasingly cancel one another as we go up in frequency. I also dislike the lobing.
It will be much easier (and much less expensive) to do what you are talking about in a 90 dB speaker rather than in a 92 dB speaker. But I'll see if I can find 92 dB drivers that would work.
This is project is, in my opinion, a definite possibility if you can live with a vented box. If not, then we'll have to juggle a harsher set of tradeoffs as far as efficiency, bass extension and box size goes. Briefly, expect to at least double your box size requirement when going from vented to sealed, while at the same time losing some optimizing flexibility.
Duke
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Hello Hmen,
Interesting idea you have - a line array that doesn't need a subwoofer. I can think of three ways to do it.
One way would be to equalize the midwoofers (or fullrange drivers). IDS uses equalized fullrange drivers in their line array speakers: http://www.ids25.com/
Another way would be to find small woofers that can go deep, and just build a big enough cabinet that they actually do go deep.
Finally, we could use a built-in powered subwoofer section - perhaps a rear-facing line array of small high-excursion woofers.
What do you think about these approaches? Are you comfortable with equalization or a built-in subwoofer section, or would you prefer the simpler approach even if it calls for a bigger box and/or lower efficiency?
Duke
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Hey Duke,
Great reply :thumb: Good to know you are using amps that are extremely sensitive to speaker selection in your designs.
I know exactly where you are coming from. The battle is going to be finding the appropriate speakers that behave well. It's not going to be easy at all. As you well know, even though the specs on a driver look like they might work for a design, when you listen to them, they just don't cut the mustard. It's been a while since I scoured the countryside for drivers for this type of design but about 4 or 5 years ago, there weren't many to be found. In turn I gave up and started using vintage and true high efficiency drivers. If prototyping drivers and minimum speaker orders weren't so expensive, that would be the way to do it. Then you could custom design the driver so it would behave (mostly) the way you wanted it to.
When it comes to off axis and power response, like you, I'd sacrifice off axis response. The way we listen really is a singular experience. Sure we have people over and listen but then the music often becomes a background rather than a focus. Most of our hard core listening time is done alone. Just us and the stereo. A narrower sweet spot then becomes far less critical IMO. Oh, and the ported enclosure works just fine. Like you, I like the ability to 'tune' a port to a room. I usually use a bit of foam in the port to dial them in for the room.
Hey (not to take us off topic but), I see you handle JoLida. Have you listened to Mike's factory mods yet? In particular, I've got the modified 102b here and it is simply marvelous for the price. He only adds another $100 for upgraded coupling caps and resistors. At $750, this thing is an absolute steal.
Back on topic. It will be interesting to see if you can find suitable, off the shelf drivers for a project like this. Most of the manufacturers and drivers I've seen really won't fit the bill for one reason or another. Shame too, there could be a nice sized market just for that type of speaker. Especially if by using different drivers you could voice the different offerings to be front row or mid hall. Then you would have most everyones personal preferences covered (and sell more speakers :D )
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An "aside" comment before I go back to responding to your posts...
I got an e-mail from someone who was afraid that my starting this thread indicated I'm discontinuing my Jazz Module loudspeakers. Nope, they're very much still the headliner in my line-up, and I'll probably bring a pair to the Rocky Mountain Audio Fest next month. I'm presently working on a larger, somewhat more ambitious project that hopefully will be ready in time for the show - so I might have two pairs of speakers in the room. And I'm working on several prototype stand-mount speakers, as I'd like to offer something in that category that's not another "me too" speaker with a 6.5" woofer plus 1" dome tweeter, like a hundred others out there (some of which are very good, but there's no point in my essentially duplicating what's already being done).
Another project is a small-room-optimized loudspeaker, but I have to do more research and prototyping to figure out what characteristics a speaker should have to really work well in a small room. This thread has been so productive, I might start another thread on that subject some time just to get other people's ideas and experiences. Most of my experience has been in medium sized rooms, so I'm sure there are a lot of AudioCircle members who know more about what works well in a small room than I do.
Duke
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Hello WEEZ,
"Easier said than done" is right indeed!
Meeting the impedance requirements you mention (8-ohms minimum and non-reactive) probably quadruples the design effort required. My current designs do have impedance peaks in the bass region so they don't really meet your non-reactive criterion. Now I could significantly reduce or even eliminate those bass impedance peaks by filling the box with a lot of acoustic stuffing, but I use those peaks as my ticket to a free lunch.
You see, a high output impedance tube amp will behave sort of like a current source, and will deliver greater wattage into a higher impedance load. Take for instance the Atma-Sphere S-30 OTL amlifier. It's a 30-watt amp into the 8-to-12 ohm load my Jazz Modules present across most of the spectrum, but into the 50-ohm twin bass peaks the amp is putting out closer to 60 watts! So what I do is tune the cabinet much lower than normal, and use that 60 watts to get a "free lunch" - a +3 dB bass boost which (with the low tuning) gives me bass extension quite a bit lower than I should be getting. A low-feedback SET tube amp will often have similar characteristics.
With a solid state or push-pull tube amp I don't get the same free lunch, so in that case I shorten the port and thereby tune the speaker a bit higher.
I have nothing against acoustic suspension, but recognize that a 1 cubic foot acoustic suspension box will probably need a subwoofer (unless the speaker's efficiency is pretty low). Now the plate amp on most subwoofers has a 12 dB per octave low-pass filter, and theoretically at least this will give a better transition with an acoustic suspension speaker than with a vented speaker.
One of the speakers I'd really like to build is a one cubic foot, 90 dB efficient, tube-friendly stand-mount speaker. I've done a lot of modelling and some prototyping, but probably won't get back to it until after RMAF. I guess you can tell that I lean towards vented boxes, because user-adjustable tuning really expands their horizons imho. Unfortunately... I really dislike grilles! I know they are sometimes necessary, but stilll...
I'm curious about the main reason behind the grille cloth requirement - is it for cosmetics alone, or do you want something that will protect the speaker from exploring little fingers?
I don't like grille cloth filtering the highs, and grille frames can also have a significantly detrimental effect. Let me show you: Cup your hands around your mouth and talk. Hear that coloration? That's what a grille frame does (though to a lesser extent - grille frames are smaller than your hands and farther from the driver). Now let me show you the solution: Move your hands 1/2 inch out from your mouth so they are no longer touching your face, and talk. See - the coloration is almost completely gone! So the principle for grilles is, if at all possible, you want them to sit out away from the baffle a half inch or more. Whether or not this gives adequate protection to the drivers is another question.
Thanks for your suggestions. I'll try to get over my aversion to grilles.
Duke
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To Kevin Haskings,
Are you still plagued by those bitchy laws of physics? What you need my friend is a Marketing Department!
A Marketing Department does not fall under the jurisdiction of those so-called "laws of physics". You want 20 Hz bass in a 100 dB, one-cubic foot box? Easily done with but a few keystrokes!!
Pumping your hand in my plaid suit and checkered bow-tie, fin on my back and a toothsome grin,
Duke
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Hi Jeff/TONEPUB,
Hope things work out well with your family, and of course you'll be missed at RMAF.
I'm still building Jazz Modules and Stormbringers, but have discontinued the Cheetah that I think you saw a couple of years ago. I hope to show a new (larger and more ambitious) speaker at RMAF. I'm also working on a couple of smaller designs, but nothing that will be ready for RMAF.
I'm not planning on exhibiting in Las Vegas next January, as I'm not recruiting dealers - which is the main focus of that fairly expensive show. I'll probably go to gawk and schmooze, though.
Duke
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This thread turned out to be very illuminating. :idea:
Duke,
Are you a step closer to the new product definition now? Any open questions?
It would be so cool to see a new product specification being developed through this exchange of ideas. 8)
Boris
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Hi Scott F.,
Thanks for writing back.
Driver specs are usually in the ballpark, but published curves are often over-optimistic. So part of the process would be buying and testing drivers.
Just for the record, the actual on-axis acoustic rolloff is imho what we're talking about when we say "first order crossover". There may be no actual filter element, or the filter may be more complex than a single cap or coil. And depending on the driver and crossover frequency, the power response of a given driver with a "first order crossover" may roll off at 6 dB per octave, 12 dB per octave, or not at all (what's happening to the driver's radiation pattern has an exaggerated effect on system power response with first order crossovers). Also in my opinon, getting a first order rolloff for one octave on either side of the crossover frequency would have to be "good enough" - it's just not practical to expect to consistently maintain a true first order rolloff beyond that.
One thing I would not be able to do is use the simple crossover topology that you suggest. Unless we address driver resonance, we'd have audible peaking at resonance and power handling would be a joke. So I'd have to use resonant peak filters (which would not be in the signal path). I don't think this spoils the purity of the concept, but it does make for a crossover that's several times more complicated. Also, it looks to me like setting sights on 92 dB rather than 90 dB would more than double the driver cost.
Yes I'm a JoLida dealer, but I haven't tried the factory-modded JoLida 102b yet, though I bet it's sweet. I have a stock unit that's out on loan right now, and it improved significantly with higher quality output tubes. I appreciate your comments on the unit - soon as I sell my demo unit, I'll have to get one.
Just curious - you mentioned zero feedback amplifiers, and I'm under the impression that the 102b has about 7 dB of global negative feedback. I could be mistaken though, and maybe that's one of the factory mods. Do you have any information on that?
It is still too early for me to say whether I can find a set of drivers that will be suitable for an all-first-order speaker. I've already eliminated quite a few based on specifications, but the search continues. You may be right in that it would take custom drivers to actually pull it off.
Duke
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Hi Duke,
Well, the grill cloth comment was mostly due to spouse approval....most wives don't like to look at speakers :?. For me, it matters not a wit :).
I thought I read somewhere that a SS 8535 would achieve 45 (F3) in a 20L sealed box. Assuming that's true; along with the more gradual roll-off of acoustic suspension loading...wouldn't you have 'usable' bass to the low 30's? :dunno:
Anyway, I just 'muse' sometimes; longing for a more modern, 'up-to-date' version of a speaker like the Large Advent... with a friendly impedence to use with tubes.
I missed your room at RMAF last year. I'll be sure to stop by this year....
WEEZ
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Hi Boris,
Thanks for your words of encouragement!
Yup, what I'd like to see is a loudspeaker project that evolves from ideas proposed here. It might end up as a commercial product and it might not, but if there's interest in the process I'll at least take it up to the prototype stage.
At this point I see four separate ideas that might be within my capabilities: Your augmented "fullrange" driver idea; Scott's tube-friendly first-order speaker; Hman's line array that doesn't need a sub; and Weez's tube-friendly small sealed-box speaker.
At this point I've been focusing on the feasibility of Scott F.'s tube-friendly first-order loudspeaker concept.
Earlier today I thought I had a set of drivers that would work with first order filters, but when I looked closer (at driver x-max requirements) it turned out that x-max would be exceeded at some frequencies at about five watts input. Rats. Unfortunately, x-max figures are hard to find for many dome drivers - so there may be some promising units out there that I don't know about yet. I could push crossover frequencies higher, but that compromises the acoustic performance. It'll probably end up being a juggling of tradeoffs - so what's new.
Even assuming I come up with drivers that look promising, I won't really know what the impedance curve is doing until I built a prototype and measure it. So it could go bust at that stage as well, if I can't keep the impedance curve friendly while using first-order crossovers.
I have ideas on how to solve some of the problems my earlier augmented fullrange speaker had, if the problem wasn't flux modulation.
I haven't looked into Hmen's line array yet; hoping he'll write back with his thoughts on the three possible approaches I described. I haven't looked into Weez's speaker yet either.
One thing I'm definitely seeing - a trend towards tube-friendly speakers. Three of the four explicitly or implicitly intended for tube amps, and the fourth (Hmen's line array) might as well be if that's what I end up going with.
Far as I'm concerned, there's still room on the table for more ideas, if anybody wants to make some suggestions.
Duke
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Duke,
You are running into the same problem I was when I was trying to do the same thing a few years back. When you start looking at the frequency response curves (forgetting power for the moment), it seems that most of the divers go into a heavy cone breakup just after they start to roll on the high side. This really forces everybody's hand in using steep(er) XO slopes if you are going to push a medium efficiency driver to its upper FR limits. There were one or two of the old Focal line that looked interesting but unfortunately, they pulled the best drivers from us DIY'ers.
One of these days, I need to sit down and read about driver design. I've picked up some info from the Cookbook but I'm sure there are some more in depth papers and books out there. I'd be interested in learning more when I can find some extra time.
On the modified JoLida 102b, I may have not been overly clear on that one. Yes, it does use feedback. I thought it was 6db but 7 is close enough :green:
I sure hope you can find some suitable drivers. Trouble is you may not. Of if you do, it may only be one or two which will really limit voicing of the speaker. Good luck in your searches :thumb:
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Hi WEEZ,
Wow, thank you! You didn't wait for me - you found a driver that will do almost everything you're asking for! That's great!
I modelled the Scan-Speak and it's an honest 86.3 dB woofer, and in a 1 cubic foot sealed box will give us an f3 of 48 Hz and an f6 of 36 Hz. That is pretty good. It won't be all things to all people, but then we both knew that going in.
Here comes the possible fly in the soup: The DC resistance is only 5.8 ohms. According to the published impedance curve the impedance minimum is about 7 ohms around 200 Hz. I can't promise that a crossover wouldn't drop that lower - hopefully not, though. So if you can live with a minimum impedance around or maybe a bit under 7 ohms instead of at least 8 ohms, we're still in the game.
You mentioned the Large Advent. Well, I think there's room for improvement, and what I'd like to do if we go with this project is build it as a three-way. Here's my angle: I place a very high priority on the reverberant sound, and if we build it as a two-way with a 1" dome tweeter, there would be a large discontinuity in the reverberant energy in the crossover region because we'd be going from a beaming 7" woofer to an ultrawide pattern 1" tweeter.
Also, once upon a time I was a dealer for a company called Cliffhanger, and they made a lovely-sounding little speaker called the Bulldog. It was a 6.5" three-way, and used the LPG 2" aluminum hybrid dome tweeter. It was the midrange naturalness of this speaker that won me over - I had no intention at the time of becoming a dealer for a stand-mount speaker but this little beast was really something special.
Nominal cone diameter for that 7" Scan-Speak woofer is about 5.5 inches, so either a 2" or a 3" dome midrange should work well. The Morel 2" soft dome comes to mind, as does the LPG 2" unit from the Bulldog; Madisound is presently listing it as "sold out" and I hope that doesn't mean it's been discontinued. Then for the top end I'd go with a .75" tweeter instead of a 1" tweeter, and there Hiquphon comes to mind.
Here are links so that you can take a look at these drivers:
http://www.madisound.com/catalog/PDF/morel/mdm%2055.pdf
http://www.madisound.com/catalog/product_info.php?manufacturers_id=138&products_id=547
http://www.hiquphon.dk/page13.html#Technical%20data%20OW%20I%20(D2094-8708-03)
Let me know what your thoughts are so far.
Duke
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Anyway, I just 'muse' sometimes; longing for a more modern, 'up-to-date' version of a speaker like the Large Advent... with a friendly impedance to use with tubes.
WEEZ
Jeez, WEEZ, that's pretty much my impression of the Jazz Module, it's even a similar price, once you adjust for inflation. Sounds like Duke has factored tubes into the design, too.
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Hi Russell,
Thanks for the plug!
Actually, it was probably the original stand-mount Stormbringer that came closer to the Large Advent in size - though mine probably weighed around twice as much (90 pounds each). The Jazz Modules on the other hand are 42 inch tall floorstanders.
One lesson I learned is, big stand-mount speakers are hard to sell. So my next stand-mounts will be quite a bit smaller.
Duke
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Russell,
As Duke said, actually it's the Stormbringer that's similar in size. But it's ported :). (Also, the SpeakerArt SuperClef.....)
Duke,
Far be it for me to suggest what to do about speaker design...I only listen to 'em...not design 'em. (which is a good thing....) :lol: All I know is, that an acoustic suspension 2-way is a rare thing nowadays. But there have been some good ones......and I liked most of them.
WEEZ
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Weez and Duke, what I meant was the Jazz Modules relate to other speakers of this time as the Advent did to the other speakers of its time, not that the size was similar.
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Hi WEEZ,
Yeah, I have rather unorthodox ideas about speaker design. I build two-ways with big woofers and relatively high crossovers, but when it comes to a small woofer I want to build a three-way. What I'm trying to do is keep the radiation pattern as uniform as is practical over as much of the spectrum as I can.
I hope you don't mind if I rattle on a bit about sealed and vented boxes. I recently learned something that I'm still excited about (it's not really earth-shaking, but it is interesting to me at least).
Earlier this year I did some testing of sealed vs vented enclosures. I built two identical enclosures, which were about the right size for a sealed box with that woofer. Each enclosure got the exact same drivers and crossover. The ported enclosure was ported to the rear (that's my standard practice for a variety of reasons), and tuned very low. What I wanted to compare was midrange only.
My expectation was that the sealed enclosure would have the cleaner sounding midrange, because if nothing else some distorted midrange energy would emerge from the port (imagine talking through a cardboard tube). I conducted a series of blind tests - the listener didn't know which box was which, and in fact didn't even know what the difference was until all the tests were completed. I played vocals with and without light acoustic instruments, and instructed the listener to only listen to the midrange. In every trial, the listener chose the ported enclosure has having cleaner midrange. I changed stuffing, I used different types of damping material, I did everything I could to help the sealed box (I wanted it to "win" because I was working on a design that called for a sealed sub-enclosure for the midbass driver). The ported box won every time.
Now maybe if the port had been on the front of the box, the outcome would have been different. But as I conducted the tests I could clearly hear it too - there was a slight "wooliness" or "boxiness" to the sealed box that the ported box didn't have. Even when I constrained-layer-damped both enclosures (I had to do both or it wouldn't have been a fair test), the difference was still audible. I switched drivers and crossovers in case there was a defective driver or miswired crossover.
All I can say is that I don't know how to build a sealed box that sounds better in the midrange than a comparable rear-ported reflex box. Maybe there are secrets that I just don't know.
Irving Fried championed the transmission line as sounding natural in part because it was a "low-pressure enclosure" - that is, it didn't put much backpressure on the cone of the woofer. He characterized the acoustic suspension box as the worst in this respect, and vented boxes as being better than sealed ones. Of course at the port tuning frequency the vented box puts enough backpressure on the cone to virtually halt its movement - but maybe that doesn't have much effect up in the midrange region.
Now as far as bass goes, yes I definitely would prefer the gentler rolloff of the sealed box. If we accept the paradigm that the frequency response curve is a reliable predictor of subjective bass quality (I think I read an AES paper that came to this conclusion but I'd have to look for it), then one interesting possibility is a ported box that has a second order bass rolloff for about an octave or so - theoretically mimicing the bass tightness of a sealed box.
So anyway I still like your basic idea for a speaker built around that Scan-Speak sealed-box woofer. If we went with a 1.5 cubic foot low-tuned reflex enclosure (tuned to say 24 Hz), we'd be -3 dB at 35 Hz and -6 dB at 27 Hz, with a second-order rolloff down to 20 Hz. [edit - I haven't checked the power handling on this so can't say for sure that it's practical at this point]. And, if my little series of tests described above is reliable, we'd have cleaner midrange as well. So... would you consider it blasphemy for the speaker to be sealed-box-mimicing rear-ported reflex enclosure?
Duke
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Hi Russell,
Wow, to say my speakers relate to others of our day as the Large Advent did to others of its day is quite a compliment. Thank you. Now I only wish I had some big bucks to spend on advertising!
Naw - I'm not practical enough to do that. If I had the money, I'd most likey spend it working on new designs.
Duke
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Duke,
Glad you wrote about experiments with sealed vs. vented boxes. As a kid I used to make sealed speakers only, at that time have never heard vented box that would satisfy me in the bass region (too muddy, no real control) and I liked to build big boxes. Now that I grew up....out of 7 or 8 pairs of speakers that I have, only one is sealed, but I still had the impression of sealed box superiority. Turns out that the only sealed speakers I have are also the smallest ones and present the most difficult load...how easily we deceive ourselves.... :scratch:
Boris
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Hi Audiovista/Boris,
I hope I didn't come across as proclaiming "this is the Last Word on the sealed vs vented" debate. I certainly don't expect anyone else to just take my word - but since what I describe was my personal experience it carries a lot of weight with me.
I think that vented boxes quickly earned a poor reputation due to manufacturers desiging them to either play the numbers game or impress with a boom-and-tizz presentation that becomes tiring over any audition longer than the ten minutes it takes the salesman to close the sale. Vented boxes were strictly against my religion for many years, and even today I'm more likely to enjoy an average sealed box speaker than an average vented box speaker. There are far more ways to do a vented box wrong than there are to do it right, but done right imho it's a front-runner.
Duke
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Hi Audiovista/Boris,
I hope I didn't come across as proclaiming "this is the Last Word on the sealed vs vented" debate.
NO, NOT AT ALL!!!
I actually appreciate that your post got me thinking about subject that I did not seriously consider for the last 15-20 years. And I just reconciled the current state of affairs at my home, versus what I had a long time ago. As I said, my impression of sealed box superiority was based on what I heard and thought at some point in the distant past. Even though, in time, I acquired almost exclusively vented speakers, that impression stayed with me for a simple reason of not actually thinking about it.
There are far more ways to do a vented box wrong than there are to do it right, but done right imho it's a front-runner.
Absoultely agreed! :thumb: Sealed box is a safer bet - and it was even more so when vented boxes were not that well designed/simulated/measured and used almost exclusively to cut costs by enabling small size speakers to output deeper bass, no matter how poor it was.
Tha fact that you are not exclusive regarding the box type (as I once was) gives you a lot of credibility in my eyes. :D Not to mention trying to come up with a perfect tube-friendly design. aa
Best,
Boris
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Hi Boris,
Thanks for writing back.
I just checked out your website; frankly I had no idea who I was talking to. Let me now tip my hat to you on your obviously very well thought-out and engineered tube amplifier designs.
I really like your running that EL84 amp in Class A mode up to 8 watts! I'd be inclined to think of it as an 8-watt pure Class A amp with an extra 3 dB of dynamic headroom.
Perhaps the one that fascinates me the most is the little i82MkII. Under $400 for a single-ended Class A 5-watt integrated amplifier. Wow!
Okay, back to the topic of this thread...
I think we're at the point where it makes sense for me to start another thread, offering some further comment on the four within-Duke's-capability proposals that have come up so far, and narrowing it down to the two that I think would be the most promising and practical as far as pushing into interesting and relatively untrodden loudspeaker territory.
Duke
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Perhaps the one that fascinates me the most is the little i82MkII. Under $400 for a single-ended Class A 5-watt integrated amplifier. Wow!
The Paul Klipsch mantra was as follows: "What this country needs is a good 5 watt amplifier"
Sounds like this little guy would be just the thing for a pair of Klipschorns :wink:
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1. A loudspeaker that can be placed against the wall or corners of a room and sound good (think against the wall omnidirectional or polydirectional loudpseaker).
2. A behind the couch loudspeaker.
3. An above the kitchen cabinet loudspeaker pair that doesn't have a hole in the middle sound due to the large distance (12-15 feet) between the speakers.
These are probably not the types of loudspeakers you want to build but it's what I really really want.
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1. A loudspeaker that can be placed against the wall or corners of a room and sound good (think against the wall omnidirectional or polydirectional loudpseaker).
2. A behind the couch loudspeaker.
3. An above the kitchen cabinet loudspeaker pair that doesn't have a hole in the middle sound due to the large distance (12-15 feet) between the speakers.
These are probably not the types of loudspeakers you want to build but it's what I really really want.
Well, Klipschorns are designed to go into corners, and can sound very good with the right amplification.
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Hello Freo-1,
Yeah that little 5-watt amp has got my wheels a-turnin'. If I was going to do a reasonably-priced speaker to go with that amp - guess what, first thing I'd look at would be exactly the format that Boris suggested: An augmented wide-band driver.
This might make a great little bedroom or smallroom system. And then when $ and/or space allows, upgrade to those Klipschorns.
Duke
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Hello Doublej,
Thanks for joining in, and for telling us about not one... but THREE speakers that you'd really really want to see.
I'll come back to the wall-and/or-corner friendly speaker in a few paragraphs - I'll have a lot to say about that one.
The behind-the-couch speaker is a totally new concept to me. I've never thought about that placement option before. I take it you have in mind the couch being a few inches out from the wall, and the speakers are between the couch and the wall? If so, I'm envisioning a wide, shallow box with probably most of the drivers facing up (maybe a woofer down lower that's too wide to fit on the shallow top of the enclosure). We'd need to pack a lot of output into a format that's just a few inches deep. On-axis response would be pretty much irrelevant, as we'd be listening to the speakers' reverberant energy only since we wouldn't have line-of-sight to the drivers. But the power response (summed omnidirectional response) would matter a great deal. Then there's the effect of the couch itself - if it's a cloth couch it would be highly absorptive, but if it's leather it would be reflective at mid and high frequencies and absorptive at low frequencies. We'd probably want to protect the drivers from stuff falling onto them off the back of the couch, so grilles of some type would more than likely make sense. But I don't see any insurmountable obstacles - only some interesting challenges.
Next is the kitchen cabinet loudspeaker pair that doesn't give you a hole-in-the-middle even though they're 12-15 feet apart. Okay, first let's look what I'd do to avoid a hole-in-the-middle. Two words: Toe-in. (Or, is that one word??) The way to avoid hole-in-the-middle with two widely-spaced speakers is to toe them in severely. And in my opinion such speakers should be designed from the outset to be toed in. This means they should have a radiation pattern that is as uniform as is practical across a wide horizontal arc. If you don't mind building a kit, Madisound has already designed this speaker. It's called the "Loki", and uses a Seas coaxial driver. The coaxial format gives very good pattern uniformity over a wide horizontal arc (something like 110 degrees in this case, if I recall correctly). Like any speaker they'll have more output on-axis than off-axis, but the output falls off fairly smoothly as you move off-axis so these speakers are very good candidates for an application like this. Toe 'em in a good 45 to 60 degrees or so. I currently use the Seas coaxials in speakers of my own design in my home theater system. This is a product I'm not planning to market mainly because I can't begin to compete with Madisound's kit price; they hadn't come out with the kit yet when I designed mine, so at the time I had high hopes.
Here's the Loki: http://www.madisound.com/catalog/product_info.php?cPath=35_40_275&products_id=1688
Just for fun, here's a link to a picture of my Seas-coaxial-based speaker, which I showed alongside the big Jazz Modules at the Lone Star Audio Fest in Dallas last May.
http://www.positive-feedback.com/Issue31/lonestar.htm scroll down about 1/4 of the way
I call my little coaxial speaker the "Leela". If you're not a Futurama fan, click on this link to understand why:
http://ng.netgate.net/~mette/fandom/costumes/leela/LeelaOrig2.jpg
Finally, let's look at the wall-and/or-corner friendly speaker. In my opinion, a design that is going to reflect midrange or treble energy off of a very nearby wall or corner is a mistake (bass energy usually can't help but be reflected off nearby room boundaries). Research has consistently shown that early-arriving reflections are detrimental to perceived sound quality (this was even shown in research published by the designer of an omnidirectional system). However - and this is where omnis and bipolars and other polydirectionals shine - an abundance of late-arriving reverberant energy is usually perceived as timbral richness and lushness. So a polydirectional located some distance from the walls works very well.
In my experience (and I've just recently completed some experiments in this regard), polydirectionals aren't the best choice for a speaker that's going to go up against the wall or in a corner, unless geometrically there won't be additional early-arriving reflected energy.
Corner placement is even more demanding. Energy that normally would have gone wide to the sides is now funnelled early into the listening area via the intersecting walls, and this tends to color the sound in undesirable ways. The answer in my opinion is a speaker whose radiation pattern is no more than 90 degrees wide, down to as low a frequency as the speaker's physical dimensions will allow (directional control requires larger and larger size as we go down lower and lower in frequency - this is why bass horns are huge while treble horns are small).
In my opinion there's a speaker on the market that's a significant upgrade over the Klipschorn. It's called the Seven Pi, and uses a much simpler but very effective bass system along with higher quality parts than the Klipsch uses. It's available in several versions; more information can be found at www.pispeakers.com.
Now if you're looking for a speaker that is either wall-or-corner friendly, then it's got to have the controlled radiation pattern that corner placement calls for along with a bass system whose tuning can be changed dramatically so that instead of becoming boomy with corner placement, it just goes deeper. I'm already producing that speaker - actually, two of them. Both my Jazz Modules and my floorstanding version of Stormbringer (which uses essentially the same enclosure) have bass systems that can be tuned from 37 Hz all the way down to 21 Hz by changing the length of the port, and the speaker is -9 dB at 21 Hz with the latter tuning. Corner loading gives a theoretical +9 dB boost. I haven't had the opportunity to test the theory because I don't have a room with two usable corners, but it ought to work. I know they can work well very near corners, tuned to the mid 20's.
Another speaker that works well with corner loading is the Audio Note An-E series. In fact, I stole my rear-porting configuration directly from them; I just added the user-variable tuning feature (mine uses a modular flared port that can be removed and the port length changed).
Of course, maybe for one reason or another (looks, size, cost) my speakers wouldn't work for somone who's looking for a wall-and/or corner friendly speaker. Perhaps I should make a downscaled version?
So anyway out of your three suggestions, I see two that I can add to the list of what would be feasible: The behind-the-couch speaker, and a scaled-down version of what I'm already doing in my current speakers. The kitchen-cabinet speaker, imho, is already being offered in a Madisound kit, or if you don't want to do a kit, then look into a coaxial by KEF or Tannoy or Gradient.
Once again, thanks for your rich suggestions, Doublej!
Duke
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Duke....
I think Boris is going to RMAF this year...so you guys can compare notes there. Boris does have some nice amps....I've heard them at our NY Rave meetings.
Interesting discussion so far.... 8)
Chris
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Thanks for letting me know, Chris! Yup, I'll definitely want to connect with Boris at RMAF.
Boris, I couldn't find what room you're in from the exhibitor's list. Please let me know. I'll be in room 1100, in "The Tower".
Duke
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Hi Boris,
....I just checked out your website; frankly I had no idea who I was talking to. Let me now tip my hat to you on your obviously very well thought-out and engineered tube amplifier designs.....I really like your running that EL84 amp in Class A mode up to 8 watts! I'd be inclined to think of it as an 8-watt pure Class A amp with an extra 3 dB of dynamic headroom.
Duke, thanks, you're way too kind. I like your def of i84 as 8W+3dB Cool! :thumb:
The Paul Klipsch mantra was as follows: "What this country needs is a good 5 watt amplifier"
Yup, when the Big Guy says so, who am I to disagree :notworthy: .... But, MF might think that's less than 1% of what you really need (http://www.musicalfidelity.com/products/supercharger/index.html).
2. A behind the couch loudspeaker.
I need one too - but subwoofer only, 6-8" deep and it can fire on the narrow end(s) or the wide side toward the wall (or couch, to shake it little during movies... :bomb:).
This one (http://www.partsexpress.com/projectshowcase/boogieman/index.html) is intriguing, what's your take?
I think Boris is going to RMAF this year...
Only as a visitor, new products released too late to make all the arrangements :cry:. But I'll make sure to come to room 1100 and introduce myself.
Boris
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Hello Freo-1,
Yeah that little 5-watt amp has got my wheels a-turnin'. If I was going to do a reasonably-priced speaker to go with that amp - guess what, first thing I'd look at would be exactly the format that Boris suggested: An augmented wide-band driver.
This might make a great little bedroom or smallroom system. And then when $ and/or space allows, upgrade to those Klipschorns.
Duke
Sounds like an excellent plan to me :D
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Grand idea for a thread topic :thumb:
What do you guys think of this?
The challenge: High end sound, extreme minimalism. No cables, no boxes, no entertainment units or shelving. Nothing but two beautiful speakers. Two towers, two clean wires out the back you plug in the wall. That's it
Built into each speaker would be a squeezebox, the amps, etc. The squeezebox display would be tastefully integrated into the front of each speaker so you could see what's playing. Absolute minimalism, deadly clean. Zero clutter.
They'd sell. I know Bang & Olufsen get close to this idea, but they don't really nail it.
To us, hifi rigs are beautiful, but to many, it's an ugly room of cables and boxes and it looks dreadful. Two towers, two wires, amazing sound. Design and architectural magazines would be all over them.
/A
It might not be a sound idea to mount the electronics inside, atop or too close to the speakers but it may depend upon whether or not you believe isolation devices are a waste of money. If you believe in them you might need to put your Squeezebox and amp atop a vibraplane shelf mounted in a hollowed out section of the speaker.
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I've been busy with show preparations, but wanted to take a moment to rcatch up here.
As I see it, we have six speaker projects proposed that are feasible for me to undertake (obviously sometime after the Denver show):
1. Boris's augmented fullrange driver speaker - basically a fullrange driver augmented by a woofer and/or supertweeter. I'd like to keep this speaker under a grand a pair but that's probably not possible; 1.5 grand may be more realistic. I'd try to do something that would work well with Boris's 5-watt single-ended tube amp.
2. Scott's tube-friendly first order crossover speaker. This would be a challenging project, and if successful might be really good. It would call for some very expensive drivers to do it right. This speaker would probably end up around 5 or 6 grand a pair with power handling limitations, and around 7-8 grand a pair with very good power handling. One drawback is the out-of-pocket I'd have to invest in this project; either twice or three times as much as any other, depending on which version we went with. Also, this would probably have the longest development time.
3. Hman's line source speaker that doesn't need a subwoofer. There doesn't seem to be much interest in this project, so I'm not planning to pursue it.
4. WEEZ's tube-friendly small sealed-box speaker. I'd like to investigate a low-tuned vented-box variation before committing to a sealed version, for reasons described elsewhere in this thread. Also, I personally like higher efficiency not only for amplifier matching but also for reduced thermal compression (greater dynamic contrast). I haven't talked much about that topic in this thread, but I think it matters. This would probably be a 2 grand ballpark loudspeaker.
5. Double-j's behind-the-couch speaker. Interesting idea, but frankly I think the market is pretty darn small. This is more of a lifestyle product, and I really don't count those types of customers among my normal customer-base. So this project would be less attractive to me because I don't think I'd sell enough for it to be worth developing and promoting.
6. Double-j's wall-and-corner friendly speaker. Okay, this one interests me a lot. As mentioned I do a couple of large speakers that fit this description, but a small one might be a very interesting product. I could make it tube-friendly (seems that's a priority to many people), and it would have to incorporate a highly adjustable bass system (which can be done several different ways). Not sure of the price range yet, but probably 2.5 grand ballpark.
Any of these prices go up if we use solid wood instead of veneered MDF. Let's assume solid wood adds 20% to any of these prices. Is it worthwhile in your opinion?
Now let me look at these with my industry goggles on. I have my philosophy about speaker characteristics and priorities, and I have some open slots in my line-up. The two proposals that are most consitent with my philosophy and would fit best into my present line-up (and future plans) are the augmented fullrange driver and the wall-and-corner friendly speaker. So in my mind these two are the front-runners. Some of the other projects are very interesting (in particular the high power handling version of Scott's idea), but I think these two would make the most sense from my perspective.
Any thoughts? I'm not dead-set here, and you can sway me.
Duke
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I'm back from RMAF now, where I had the immense pleasure of meeting Boris, aka Audiovista. Thanks for taking the time to come by my room, Boris!
Okay, a rather challenging loudspeaker suggestion was made over in another thread, entitled "What do you like to see next to be developed by a hifi manufacturer?":
Spud wrote: "How about a speaker which is full range 20Hz-20,000Hz and sells for less than $3500."
I did some modellng and think I can do that, and keep it tube-friendly as well. Maximum linear output would be around 102 dB (I'm assuming some boundary reinforcement in the deep bass), so this system wouldn't have quite the dynamic headroom of some others. Above 102 dB and we start exceeding the linear excursion capability of the drivers. I could make this speaker wall-and-corner friendly, but then wouldn't be able to hit the 20 kHz top end (we'd probably only get up to about 18k or so because a wall-and-corner friendly speaker would have to have good radiation pattern control, which narrows my choice of high frequency drivers quite a bit). In my opinion, the advantages of radiation pattern control outweigh the loss of the top 1/5 octave of high treble, which I can't hear anyway.
This speaker would be compatible with Boris's amplifiers, but would be priced higher than what most of his customers are probably looking for. It would be a floorstander.
Duke