[MJK]

TerryO,

Those are beautiful looking cabinets. Definitely high quality workmanship.

Martin

[DaveC113]

I don't think I've seen a comparable piece of bird's eye maple to the cabinet on the home page.

I also enjoy the effect of top mounted or bipolar drivers... 

[TerryO]

Martin & Dave,
I don't know if your eyes or monitor are superior to mine (if they aren't, more's the pity :^), but I can assure you that the picture I get from accessing the website doesn't remotely do justice to that veneer and finish. These are just pure eye-candy, that also happens to be a very nice sounding speaker.

I happen to favor the muted tones of blue, green, gray, and red in a variegated patina of aged bondo with a satin clearcoat
Nothing says DIY like Bondo!

Best Regards,
TerryO

[rajacat]

Rajacat,

I just picked up a Behringer DEQ2496 and mike in the hopes of tweaking the room response, but primarily to replace the baffle step and zobel circuit (in the digital realm when I get a DAC).  As you say, it has bugged me that my chip (not digital BTW) based monoblocks don't quite have a direct connection to the single drivers with the baffle step/zobel circuit in the path. 

I probably won't get to it for a while as work is a bit hectic, we're in the middle of some landscaping work, and I'm running Dad one or two days a week to doctor's appointments.  Plus I need balanced to RCA adapters and to study how to use this thing.

JLM,

I'm not really sure if my Omega Hemp Dipoles need baffle step correction. If I want to experiment I might try the Inguz plug-in for the SB and do the correction in the digital realm therefore eliminating one more device and interconnects. I've been rolling gear recently and now I have biamped the Omegas with some stock Trends 10.1 and they sound great and I'm sure that my planned mods to the Trends will yield further improvements. I'm expecting delivery of a new battery supply soon which will eliminate most of the extraneous noise and smooth the SQ. BTW the detail I'm hearing from this setup is awesome.

--Raj

[TerryO]

JLM,

I'm not really sure if my Omega Hemp Dipoles need baffle step correction. If I want to experiment I might try the Inguz plug-in for the SB and do the correction in the digital realm therefore eliminating one more device and interconnects. I've been rolling gear recently and now I have biamped the Omegas with some stock Trends 10.1 and they sound great and I'm sure that my planned mods to the Trends will yield further improvements. I'm expecting delivery of a new battery supply soon which will eliminate most of the extraneous noise and smooth the SQ. BTW the detail I'm hearing from this setup is awesome.

--Raj

Raj,
I went to the Omega website but couldn't find any dipole speakers.
If you meant Bi-pole, and a lot of people use the two terms interchangeably, then the answer is that you don't need to utilize a BSC circuit. The BSC is merely a means to mitigate the drop in SPL levels as a speaker attempts to go from front firing the higher frequencies that have wavelengths shorter than the width of the baffle to the loss of level experienced when the longer wavelength of the lower frequencies have to wrap around the sides of the baffle as well as off the front. This is what "baffle step" is. The frequency of the onset of baffle step is just a relationship to the edges of a baffle. The worst baffle shape is a circle with the driver located in the exact center, which in our hypothetically perfect world results in a full 6dB of attenuation at the wavelength that exceeds the baffle width.

Now, as Dave (Planet 10) and Tim Foreman (a gifted Seattle speakerbuilder) have demonstrated in the past, and they're fully supported by theory, a Bi-pole (with the 2nd driver on the back) cancels baffle step by supplying the boost needed. It's actually very simple, works like a charm and you don't get any nasty side effects.

So unless you feel the need to have a really poor sounding speaker, you can rest assured that Louis has already solved the baffle step problem

Best Regards,
TerryO

[opnly bafld]

Raj,
I went to the Omega website but couldn't find any dipole speakers.
If you meant Bi-pole, and a lot of people use the two terms interchangeably, then the answer is that you don't need to utilize a BSC circuit.

Best Regards,
TerryO

He means dipole, the front and rear drivers have separate binding posts so they can be used in phase or out of phase. I believe many prefer them dipole.

Lin

[rajacat]

Yeah, I mean dipole although these speakers can also be wired to play bipole. I switch them around sometimes. They are very versatile. Can be hooked up in either 4, 8 or 16 ohm. Monopole, bipole, dipole, single driver, 1-1/2 way.I need to experiment more but I'm enjoying them as they are and biamped.

-Raj

[TerryO]

Raj,
I went to the Omega website but couldn't find any dipole speakers.
If you meant Bi-pole, and a lot of people use the two terms interchangeably, then the answer is that you don't need to utilize a BSC circuit.

Best Regards,
TerryO

He means dipole, the front and rear drivers have separate binding posts so they can be used in phase or out of phase. I believe many prefer them dipole.

Lin

Lin,
As soon as I read your post I remembered that Louis had provided for that option in some of his designs in the past. Dipole is an entirely different animal that has it's own set of positive (and negative)attributes. A classic dipole depends on the null created at the side of the baffle to cancel most of the energy that would otherwise be generated at 90 degrees from the surface of the baffle. This allows a great deal of attenuation in room reflection from the side walls with the confusing arrival time/phase inconsistencies. To overcome this, one would either need to reduce the frequencies above the bafflestep frequencies or to equalize (boost) the lower frequencies. With 4.5 inch drivers this isn't an enviable position to be in, as the difference in levels tend to be extreme. I would be very careful in going about this as it will be very easy to exceed the limits of the driver. I would strongly suggest contacting Louis about this before going ahead. If a subwoofer with a decent upper frequency reach is available then that may work, but in any case I would be very cautious.

Best Regards,
TerryO

[JLM]

rajacat,

As recently discussed elsewhere on Audio Circle, perfectly flat frequency response is almost never the ideal.  Fortunately I'm in a near ideal room, nearfield setup, and have absorption panels at front/side wall first reflection points as well as front corners.  My speakers are rated in-room flat to 30 Hz.  So I've got no compliant with the sound, mostly would like to gain a more direct amp to speaker connection.  (I'm big on the advantages of active speaker design.)

Eventually I'll have the DEQ2496 in the digital realm, but need to pick up a DAC first.  Not being able to use software (or a Squeeze Box) is one of the penalites I pay for being a computer dunce.  I tried the SB (fully modded Red Wine Audio) when it first came out (with a RWA Clarity amp) and couldn't tell the difference between A/C and battery (but I've got nearly ideal A/C here).  So I'm back on the grid and off RWA stuff.  I'm not discounting the importance of clean power, especially for digital circuits.

For better or worse I'm not alone.  Several Audio Circle members (mostly by PM) have mentioned computer/SB related glitches and not being able to hear a difference with batteries.  IMO the power issues are very dependent on how clean your A/C is to start with and much less dependent on your ears or system's resolution abilities.  The computer savy folks can quickly fix the glitches, but the rest of us struggle for days each time one pops up.  I used to be computer "friendly" in the 70s when computing was a science, but nowadays its mostly an educated excerise in trial and error.  Guess I would have made a lousy lab rat if I had to run the maze to find the cheese.

OTOH I'm less dependent on technology with a transport/DAC.  It's also more portable (into other systems).  And I can listen to a CD without ripping.  Plus it gets me off my lazy butt once an hour.

[Duke]

Hello TerryO,

I agree with your positive assessment of Lew Hardy's polydirectional Vivaldis as well as of Louis Chochos' Omegas, be they of the monopole or bipole or dipole variety. 

Having worked with bipoles somewhat myself (my first commercial effort was a bipole), I'd like to toss out a few comments.  You are correct that a bipole very elegantly solves the baffle-step issue; however, the bipolar configuration is not without a potentially detrimental side-effect that needs to be addressed at the design stage. 

The problem you get with a bipole is this:  There will be a frequency at which the wrap-around energy from the rear-facing driver will arrive at the listening position exactly 1/2 wavelength later than the energy from the front-facing driver.  At that frequency, a cancellation notch will occur.  Actually this is an oversimplification; the wrap-around effect is sort of smeared out across a frequency range because the wrap-around path length isn't the same for each path that the sound waves take around the cabinet.   So in practice the actual effect is a fairly broad dip instead of a narrow notch.

Over the years designers of bipole system have taken several different approaches to this issue.  Mirage notched the rear-facing woofer's frequency response on their landmark M-1, and many of their subsequent bipolar models simply didn't have a rear-facing woofer operating down in the wrap-around notch region.   Definitive Technology patented their side-firing-woofer bipolar array, whose side-firing woofer is active to up above what would have been the wrap-around notch frequency.  Louis Chochos uses cabinet geometry to minimize the severity of the wrap-around notch, making his cabinets considerably wider than they are deep so that less energy is actually wrapping around in that wraparound-notch frequency region.   

Finally, in practice, the wraparound notch is primarily an on-axis, first-arrival-sound anomaly and disappears in the power respose of a loudspeaker system.  So it is not nearly as audible as its alarming impact on an anechoic frequency response curve would suggest - but imho it's still worthwhile to take steps to minimize it.

Duke

[MJK]

The problem you get with a bipole is this:  There will be a frequency at which the wrap-around energy from the rear-facing driver will arrive at the listening position exactly 1/2 wavelength later than the energy from the front-facing driver.  At that frequency, a cancellation notch will occur.  Actually this is an oversimplification; the wrap-around effect is sort of smeared out across a frequency range because the wrap-around path length isn't the same for each path that the sound waves take around the cabinet.   So in practice the actual effect is a fairly broad dip instead of a narrow notch.

I agree, but a potential bigger impact will be the reflection of the direct response from the rear driver off of the rear wall coming back at the listener. This can cause a deeper and sharper dip in the SPL response. To help with the "wrap-around" effect and the rear wall reflection, there is probably a real advantage to rolling off the rear driver at or just below the baffle step frequency and returning to monopole operation. You can see an example of this type of design in the Ported Box Bipole Box worksheet pdf file on my site. By balancing/optimizing the enclosure depth, width, and the filter for the rear driver a better SPL response solution can be generated.

You can simulate a bipole response with a simple front firing speaker by backing it up flush against the rear wall. The "wrap-around" from the front driver will be reflected and simulate having a rear driver at twice the depth of the cabinet. This is why people place speakers closer to the rear wall to try and help mitigate the BSC problem that they hear with the speaker placed further out into the room.

One other disadvantage of the bipole is the increased volume requirement for the enclosure, using two drivers will require double the enclosure volume to maintain the same bass tuning. If done correctly the bipole speaker should be able to get away without a significant BSC filter requirement.

Martin

[rajacat]

Raj,
I went to the Omega website but couldn't find any dipole speakers.
If you meant Bi-pole, and a lot of people use the two terms interchangeably, then the answer is that you don't need to utilize a BSC circuit.

Best Regards,
TerryO

He means dipole, the front and rear drivers have separate binding posts so they can be used in phase or out of phase. I believe many prefer them dipole.

Lin

Lin,
As soon as I read your post I remembered that Louis had provided for that option in some of his designs in the past. Dipole is an entirely different animal that has it's own set of positive (and negative)attributes. A classic dipole depends on the null created at the side of the baffle to cancel most of the energy that would otherwise be generated at 90 degrees from the surface of the baffle. This allows a great deal of attenuation in room reflection from the side walls with the confusing arrival time/phase inconsistencies. To overcome this, one would either need to reduce the frequencies above the bafflestep frequencies or to equalize (boost) the lower frequencies. With 4.5 inch drivers this isn't an enviable position to be in, as the difference in levels tend to be extreme. I would be very careful in going about this as it will be very easy to exceed the limits of the driver. I would strongly suggest contacting Louis about this before going ahead. If a subwoofer with a decent upper frequency reach is available then that may work, but in any case I would be very cautious.

Best Regards,
TerryO

Why not design the cabinet to boost the lower frequencies to compensate for the baffle step attenuation? BTW if you read closely Louis states the various hookup options for the Bi/dipoles. ZLS has an exclusively dipole version of the Bi/dipole that Louis built custom for him using larger boxes, I believe about the size of two Super 3 XRS boxes back-to-back. Also the new 4-1/2" hemp driver has a large excursion that enables it to go a lot lower than the Fostex 127 it replaced. Hemp fibers are very strong so maybe there can be new vistas in small driver design to explore.

- Raj

[MJK]

Why not design the cabinet to boost the lower frequencies to compensate for the baffle step attenuation? BTW if you read closely Louis states the various hookup options for the Bi/dipoles. ZLS has an exclusively dipole version of the Bi/dipole that Louis built custom for him using larger boxes, I believe about the size of two Super 3 XRS boxes back-to-back. Also the new 4-1/2" hemp driver has a large excursion that enables it to go a lot lower than the Fostex 127 it replaced. Hemp fibers are very strong so maybe there can be new vistas in small driver design to explore.

- Raj

What type of design would you recommend?

A bass reflex or classic TL style of enclosure will not do it. The only option seems to be a form of BLH/TL hybrid which gets big fast if you want low frequencies. Designing and building one of these is not so easy.

Martin

[rajacat]

Like I said in my previous post, Zack, aka ZLS, has a custom design by Louis of Omega Speaker Systems that attempts to address these design issues. PM Zack for more info. http://www.audiocircle.com/index.php?topic=41682.0

-Raj

[TerryO]

There are many ways to address the BSC question, I mentioned the bipole as the Omega speaker was brought up and it is easily configured to address this "on the cheap." Martin mentions rolling off the rear driver at the Baffle Step frequency to alleviate any nulls and that is certainly a viable alternative. For the Omegas, all that would be necessary is an outboard inductor in series with the rear driver, no surgery needed and it's removable. It is certain that if new cabinets are contemplated or being built, then the doors are opened wide for many solutions. It is common for multiway speakers to be designed with BSC in mind and one such configuration is to roll in a second woofer at the baffle step frequency. This what is being addressed in 2.5 and 3.5 way speakers. There is no reason that a 1.5 speaker can't be built with 2 front firing drivers, with the second one rolling in with a first order crossover at the frequency dictated by the baffle. One advantage to this is maintaining efficiency, as passive BSC components can only shelve the upper frequencies to achieve this, much to the consternation of the Hi-Eff people using low powered amplifiers. This is similar to Martin's solution and, in my mind, perhaps a bit less complex. The arrival time shouldn't vary, introducing any phase inconsistencies as such and the World is a happier place.
These are just some thoughts to be considered.

Best Regards,
TerryO

[Ed Schilling]

Damn Martin. We are in agreement for the most part.

Rajacat, (this is not all directed at you!)
Contrary to popular relief "more excursion" in a single driver speaker is not always (usually) a good thing. If you do a little math you'll find it takes a "lot" of excursion to reach a "little" lower. In addition, printed specs have little (usually) to do with actual sound. Not that they can't but whose to say whose "measurement" of "x-max" is correct? There are at least 2 ways of measuring it.....are both parties being "honest" in their interpretation of their findings?

There is so much "misinformation" as to what makes a single driver "work" it makes my head spin. While some of it is "correct" on "paper" in reality things are quite different. On paper my turbo Volvo will hit 105 on my dirt road. Unless you are ready to die you'll not try it.

Similarly, to have the single driver produce the least distortion over it's range, the cone will be need to be doing the least amount of excursion. That's just the way it is. The trick is then to figure out how to achieve a balanced sound down to an acceptable cutoff while maintaining the least amount of excursion. A "high" excursion 4 inch driver when driven to high excursion will simply sound bad. A design that does not address this will not be able to play at very high SPL's. Oh it may have (shitty) bass but overall it'll just sound dead and lifeless. There are practical ways of lowering the excursion and cutoff but thinking a particular (single driver) design could be "improved" by increasing the excursion of the driver is the wrong direction to go. UNLESS the driver is running out of excursion.

I have played my speakers in my 17 X 18 room with a Pass X 150 and recorded the SPL at >115 Db PEAKS on the drum solo on Stereophile Test CD 2. This is plenty. And there was not a hint of compression/distortion.

Increasing the excursion or lowering the cutoff of my speaker (which I guess I could do if I wanted) would ONLY decrease the SPL at the expense of a couple extra hertz. The increase in the excursion would cause the sound to sound "muffled" at that 115. Increasing the bass through excursion in a single driver speaker will severely limit the overall output due in part to "modulation distortion" of the midrange. Whether it can be measured or not you'll hear it.

There is a lot to building a successful single driver speaker...by that I mean one that goes low enough to "git 'er done" and one that is efficient enough to play AC/DC at live (>100Db) in the listening room. A good speaker must be able to play both soft and loud.

As we all know there are trade offs to be made in any design. but there are a couple basic rules........excursion in a single driver speaker is your worst enemy.....the end result is what counts, not the driver, not the box.....high efficency is your best friend, it's better to have the ability to play loud and clean and supplement the bottom than to play low and deep but only at sedate levels, and there can not be both from a single driver. A single driver speaker can be "rated at 95 db efficient" and not be able to play actual music at 95 db because of excessive excursion at low freqs.

And about BSC.....who cares? Why in the world does that even come up. When a fellow designs a speaker I figure he makes a target and achieves the goal....you know....."x" cutoff...."x" freq. response......"x" power handling and efficiency". I always thought the goal was simply to achieve as flat in room response and as high efficiency as possible. The BS was just part of the  WHOLE design.......it never occurred to me to think of the effect as "special"....it is just "what happens".

Cone material is another one....who cares? If a driver sounds good it could be made of bird shit. And if it sounds good it probably will have more to do with the whole design rather than the bird shit cone. All of this rant is my opinion......and I have used these opinions to do what I do. It seems to work for me but they might not be right in some peoples eyes. But they do work for me.

Duke, don't you get tired of saying the same stuff, too? You are very good at making the complex understandable but sometimes don't you just want to suggest that people should do like you and I did....read all the old books and journals and build a million "boxes".

It seems people think they can learn it all on the internet by simply reading about it but no one thinks for a minute that anyone could do their job or profession by reading forums in their spare time. I would encourage anyone interested in speaker design to read all the "old" books on speaker design. The simple principles will help a lot and then Duke might not need to explain BS so often and I won't have to point out that statements like "the extra xmax will allow it to go lower" are absolutely true but meaningless and even harmful in the case of a single driver speaker (but not a sub woofer).

"Designing" a loudspeaker is very easy. Making one that actually sounds good is much more difficult. And by that same token...."copying a speaker is easy, copying the sound of a speaker is almost impossible, everything matters ( from Mr. Cat).

In an effort to stay on target....the best single driver unit I have heard are the Bandor. But they will not do AC/DC in a large room so that always kept me from using them most of the time. The do sound beautiful in a very small box for anything but R&R. Of course this applies to most single driver speakers I guess.

There. I feel better now.

Ed

[rajacat]

It would be great if Louis would chime in to defend his designs. He would be much better than me at explaining the technical issues. One thing that I do know is that, with good quality material, I can play my Omegas at very high volume (for my hearing) without noticeable distortion. It seems that driver technology can advance over time and new cone materials will surely be developed that will enable larger cone excursion without more distortion. Of course, I'm running 2 identical drivers each with their own box within a single cabinet per side in concert with each other, out of phase and facing in opposite directions instead of the usual 1 driver in most "single driver" designs. Therefore higher efficiency, less excursion and less distortion for a given SPL would seem to naturally follow. I'm not sure how all this interacts with the room in technical terms but it sounds fine to my ears.

-Raj

[MJK]

And about BSC.....who cares?

Most people care. If you are going to use a single driver in a ported box, a TL, or a seal box you have to address the baffle step loss of bass output in some manner. Using EQ, tone controls, baffle step correction filter, subwoofer, or whatever; if you don't do something you are going to have a thin sounding speaker. I think that most of the hand wringing over single driver speaker performance is centered around this one issue. Just read the various HE or full range driver forums, most of the discussions revolve around dissatisfaction with bass performance.

[Ed Schilling]

Martin, Again. We agree. You have to address it. So that is what you do. I was implying I don't think of this as a separate issue. It is simply one problem. And when you address it in those enclosures you inevitably increase excursion....which limits out put (due to the excursion distortion you can tolerate)....and there we go. Which is exactly why I found 20 years ago that TL single driver speakers were "not for me". I did have to address it in the sealed and TL's. I never built a ported SD system because I don't like them. The correction networks or altering the speaker or both always resulted in an unacceptable (to me) loss of overall "real world efficiency". In other words while not thin they did not have a prayer of doing justice to Metallica or INXS. And some people listen to that type music as well as Nora. or  Wagner.

The whole "not loud enough" problem in spite of the inherently good things about single drivers which I'd loved for over 10 years is what caused me to look in another "direction". The BLH......and I got lucky....almost 8 years ago now.

But you hit the nail on the head....it is important but not anymore so than other aspects of different design problems. It is what it is and it is just a little worse to deal with than in a multi way. The solution using altered drivers or comp networks is not a good solution in a single driver speaker. And all the talk in the world about them and how to deal with it will not fix it. Those pesky laws and the amount of what I'll call "excursion distortion" that any single driver will have can not be overcome. Larger drivers will not help, and have other problems.

Just my opinion. But nice to see we agree in principle about the need to fix it even though we may not agree on how or whether it is a separate problem. I think not. All narrow speakers suffer the effect, I think and most designers simply assume it part of the over all design.


Ed

[Duke]

Hello Martin,

Thanks for responding to my post.

I model bipoles in LinearX's "Enclosure Shop", which unfortunately doesn't do tapered quarter-wave tubes.  

I would think that backing a speaker up against the front wall only simulates the baffle-step-region-and-below behavior of a bipole; it doesn't accurately simulate the relative intensities and arrival times of the direct versus reverberant energy.

Regarding that rear wall reflection - James M. Kates in his article entitled "A Perceptual Criterion for Loudspeaker Evaluation" (supported by other articles since then) showns that the ear's sensitivity to tonal coloration from a reflection peaks at about 2 milliseconds delay and has tapered off significantly by 5 milliseconds, so if the rear wall reflection arrives much later than that its detrimental effects should be minimal.  With dipoles (which I sell), I shoot for a delay of at least 10 milliseconds - which isn't always feasible, in which case I try to diffuse or (as a last resort) absorb the backwave.  My understanding is that with enough path-length-related time delay, reflected energy is classified by the ear/brain system as "ambient energy", rather than fusing with and distorting the direct sound.

Even after optimizing the bipole, the big question would still be:  Can $X spread among all the drivers and complexity required for a bipolar system sound as good as that same $X spent on a more conventional system?  The answer may vary from one person to the next.

Duke