[Graham Maynard]

Hi painkiller,

That's NEAT !

Cheers ...... Graham.

[painkiller]

Thats fantastic! Its funny the alpha looks a bit pissy next to the tt, how does the tt sound.I thought you had b200 and if you did how do they compare?
                                 cheers  fergs

by the way where is the tweeter brought in at and what is the tt good up too?

The Tone Tubby is massive compared to the Alpha 15A. I like it a lot. Really dynamic and powerful. I've never heard the B200, so I can't compare them. They are quite different on paper though. The superboy is a 15", 99dB, Qts=0.3 driver. Not an obvious choice for OB. I guess the Visaton has a higher Q value, and a bit lower efficiency? It should be a lot easier to implement than my 15". The other TT drivers would also be easier. Especially the 10" Alnico should be a breeze to implement with a single 15A and the T-bass.

The tweeter is brought in at 4kHz with a 4,7uF cap. The 15" is actually good up to 5kHz, with a smooth roll off and little cone breakup. No beaming. I tried to cross the tweeter higher with a smaller cap, but I found that it reduced overall SPL at higher frequencies. That's why I need a more efficient tweeter.

[scorpion]

Painkiller,

Really great, nice indeed.

graham,

I don't really question your circuit. But I think that the same effect can be achieved in other ways. I would say that the Behringer unit is both able and very versatile. But you can really run it one- or two-channel just taking advantage of its tone shaping abilities not caring about crossovers. I suppose that the Transformers you are recommending easily will be priced around 100 US$ now each so advantages are certainly diminishing with growing copper price.

/Erling

[Graham Maynard]

Hi Erling,

My point all along has been that once properly set up, the same kind of response cannot be generated using any line signal method.

Cheers ....... Graham.

[-Richard-]

Hi Painkiller ~

I love your Open Baffle design... Form Follows Function... I believe that dictum came directly from the Bauhaus. I also back-mount my drivers... and the slanting rim of your driver holes adds a subtle wave-guide... an excellent choice!!!

Thanks for posting your lastest creative exploration... I am getting tempted to add a tweeter to my baffles for "air"... the upper frequencies are satisfying... but I am aware of a lack of "air"... perhaps a back-firing unobtrusive sounding tweeter might be desirable... however I am not certain where to even begin.

Since your set-up uses the TT which hands over upper-frequency duties to your tweeter at around 4kHz, it is perhaps not quite applicable to my use of the B200 with Alpha arrangement.

I am keenly waiting to see if someone with the Alpha/B200 arrangement experiments with a tweeter for the subtle sensation of "air"... or upper frequency "presence"... the problem of course is that it can become spotlighted or hot... or perhaps it might re-balance the all-over frequency perspective so that the current illusion of having adequate bass disappears... necessitating some form of augmentation to bring that out further.

Designing ones own OB's is deeply satisfying... but it does require some experimentation as one understands better, through careful listening, what is missing or what can be added to better balance the all-over tonal presentation. Of course one' amplification and digital source also plays into this... alchemy or integration is the key here. The most interesting part for me... besides the incredible sound reproduction which is entirely magical... is that instead of throwing large amounts of money at the speaker solution... one merely does a bit of experimentation with drivers.

For curious readers who might be interested in experimenting with their own OB's: experimenting with OB's will disengage you from the "conditioned" idea that money thrown at speakers equals great sound... or that there is an "elite" community of owners of expensive speakers that "uniquely" enjoy great sound... while those who can only afford cheap speakers must "settle" for a less pleasurable experience. Most expensive commercial speakers are quite less satisfying to listen to than what is possible with a modestly well-executed Open Baffle design. The lust-factor ends with ones own OB's... and the enjoyment factor takes off to an entirely new dimension in listening.

Please keep us informed, painkiller, of your unfolding insights.

Warmest Regards ~ Richard 

[jeffac]

Hi Graham,

You and other learned folk here at AC are certainly pathing the way ahead in OB, well done all and thank kindly for sharing many fantastic ideas. And your enthusiasm has prompted me to have a go at DIY speakers with associated homework. So where am I at? I've been running B200s for 18 mths or so now since getting entrapped in the gravity of the dark star thread. They're modified with a magnet-attached phase plugs and sit on simple winged baffles powered by a T-amp. Lots to like but.... to address deficiencies I now have 4 x Alpha-15As plus some Aurum Cantus G2Si ribbon tweeters and some scrap plywood for test baffles. The plan is to biamp, with the Alphas in parallel and the B200s and G2Sis in parallel. The latter are both nominally 6 ohms, and the GS2is will be high passed with a ~4uf cap and fired backwards. My intention is to also use a small (~0.1uf) good quality film cap as PLLXO before the T-amp driving the B200/tweeter, to remove LFs. Initially, I have a second T-amp that will be tested with the Alphas, but my guess is more power will be needed for bass weight and control. And of course, I am very keen to use your T-bass circuit to push out LF extension of the Alphas on a simple baffle.

So that's the plan, but help and advice will be welcomed. For the T-bass transformer, I can get 300VA ones locally that are reasonably priced with 18V, 24V or higher or lower V secondaries. Be nice to get this close to right first up, it being central to the circuit. Your pick?

cheers.. Jeffac

And Richard,

To a large degree it was you're eloquent prose and infectious enthusiasm for what you were hearing with your B200s way back in the Dark Star days that made me want to experience the same ... a more life-like presentation that OB can bring... thank you sincerely. Upward on onward now to improving the bass and taming some of the bite of the B200s, which I hope the 15As will help with from your experiences of running them higher up into their useful frequency range.

[painkiller]

Thanks for all the positive feedback. I'm pretty happy with the result, but I wish I had used russian birch plywood in the first place. I can't stand the thought of starting all over with the baffle, so I guess I'm stuck with the MDF. When the speaker is "complete" I'm planning on doing a piano finish. aa

Richard,
the B200 frequency response rolls off beyond 10kHz. If you cross a high SPL tweeter using a 1,5-2uF cap you can add some extra air without doing much harm. I never found that the response beyond 10kHz contributes to the impression of lack of bass. It can create sibilance and a tiring sound, but not affect bass performance. I find that the right HF level is important for achieving a relaxed sound though. A forward midrange (relative to bass and tweeter) is much worse. But that's me.

[Graham Maynard]

Hi Jeffac,

Re your B200 based system.  I saw you intend to use the G2Si ribbon - then I had to re-read to check because I know you could not get these to match a B200 with circa 4uF. 
Aha;  you stated rear mounted.  Good intention there ! 
This to increase the HF 'air' without attempting to crossover with the B200 which would modify reproduction instead of augment it.
(Maybe with an adjustable level control and with this rear tweeter angled so that it indirectly diffracts over the upper/outer baffle edge as well.)

Transformer ?  Parallel connected Alphas will increase current loading upon any amplifier so component choice depends upon intended amplifier drive.
Your Alphas have to match the B200 for output above 1kHz which means they will need good drive.  The 2x 24V component will give you protection against saturation in case someone has a rock-party, whilst the winding resistance will still be low enough for parallel connected drivers.  This would be my choice.

Cheers ........ Graham.

PS.  The DarkStar thread influenced my choice for the B200, but this driver needs help at LF.  I tried other options as per enclosured LF, EQ, Linkwitz, John K, MJK etc. but none of these blended in to provide a correctly timed integration like that of the B200 on its own.  This transformer based circuit came out of deliberate modification of driver Qes using series components, and from the very first moment heard it became a wanted solution.

I cannot ever forsee going back to boxy bass again;  that sets up too many room modes.  Also 'flat panel' LSs which introduce little LF colouration and can easily be moved out of the way in towards a corner wall when not being used, are far easier to live with than a heavy enclosure or subs which often need to be decoupled from the floor and which introduce aspects of disparate timing.

Look at this for a simple 'panel'.  Bet it rocks !  (Post#119)
http://www.diyaudio.com/forums/showthread.php?postid=1594426#post1594426

[jeffac]

Morning Graham,

For someone who doesn't fully comprehend the mechanics of how your T-bass circuit does its job, much appreciated advice to get me started, Ta.

And time now to stop procrastinating about design and cut holes in timber. It might go a bit slowly but I shall report on progress.

cheers.. Jeffac

[Vix]

Hi Graham,

During this weekend I have tried the T-bass circuit. I have used 2x18v transformer, 6.6 mH choke (3.3+3.3 in series) and 1100 uF elco capacitor (two 2200 uF connected in series at their negative terminals). While I can say that it does its job, and there is some LF boost, I was a bit concerned about the ability of my Sony amp to drive them. So, after one day experimentation, I have disconnected it and went back to my initial setting, 80Hz 12 db/oct both high and low pass. Why?

I again tried running Eminence Beta 15 s with a first order crossover, and, even with T-bass circiut in place, I was not happy. Not because of the T-circuit, but because I can't stand that midrange mush-mash coming out of Betas when running on a single choke, with or without Zobel, with or without T-bass. Actually, I find that I need at least a second order crossover on Betas, and the max frequency that I could stand, is around 100 Hz. Above that, the blurred lower midrange starts being heard from Betas, and it sounds absolutely disgusting. This makes me wonder how others can run 15 inchers via first order crossover, or even 2nd order and that at just 200 Hz,  as Martin did with Alpha 15's. On the other hand, perhaps Alpha 15 sounds different enough from Beta 15 so people don't experience with Alphas what I experience with Betas. Richard was quite pleased even when he run Alphas fullrange 

Or, maybe it's just a matter of taste...

Thanks a lot,

Vix

[-Richard-]

Hi Vix ~

I am currently using a simple coiled inductor value of .8, which gives the Alpha 15A's a cut-off of around 1200Hz... which sounds quite fantastic!

I choose this cut-off point based on Martin's frequency response chart which shows a spike after that.

Honestly... I do not hear any distortion as you so colorfully indicate: "I can't stand that midrange mush-mash... the blurred lower midrange starts being heard from Betas, and it sounds absolutely disgusting."

What Deborah and I hear is startling clear, tonally and texturally rich, detailed, spacious, viscerally "present" instrumental and voice reproduction with all the ambient space of the recording venue intact.

Can amplification or source be partly responsible for what I am hearing? or what you are hearing? I don't know. I am currently using Vinnie Rossi's Signature 70.2 monoblocks with Lloyd Peppard's triode tube preamplifier and a cheap "universal" Pioneer CD player.

I personally stay away from too much crossover intricacies... out of ignorance... and perhaps laziness.

Perhaps you might be a good candidate for using an active EQ device... like the Berhinger or Martin's dBx Driverack PA digital crossover... that way you can dial-in any number of crossover configurations to hear what sounds compatible with your Eminence Beta 15's.

Warmest Regards ~ Richard

[Graham Maynard]

Hi Vix,

All drivers are different.  On a baffle the Alpha generates greater SPL below 100Hz than the Beta, but lower output above, so a simple crossover will work.

If you would care to try the T-bass again I would suggest;-

do not put any resistor in series with the chokes (6.6mH)
use a one ohm resistor in series with 470uF for the capacitor
insert another choke of between 2 and 4mH in series with the driver
connect 4.7 ohms in series with 10uF across this choke
place a Zobel of 4.7 ohms in series with 220uF across the driver

If this does not fully tame the Beta then you could mount it on the baffle facing rearwards into a soft cushion to absorb 'mush' without introducing additional phase lag as would another section of electrical crossover.

Hope this helps because I cannot see an ordinary crossover being as good in this situation.

Actually my 15" Beymas have more output above 100Hz with respect to 50Hz than a Beta, it is just a question of getting the component values right.  EQ can be useful but will still introduce additional phase differential at the acoustic crossover.

Cheers ....... Graham.

[Vix]

Hi Richard and Graham,

Thank you for the replies. Richard, it is strange how we had so different experience. It would be nice if I had Alphas, or if you could try Betas. Only then we'd be able to tell how much of the experience can be attributed to the speaker, or to our taste. I am sure that amp have influence as well, but in my case, I have tried both amps, Pass Zen V9 and a Sony TA-N 511, and, even though Zen is a better amp, there was not much difference in "muddiness" of Beta. Preamp is a 6922 tube buffer. Source is a Denon DCD-800 CD player.

Only the first order crossover was passive. I have tried several inductor values, starting from 0.68 mH air core to maybe 10mH (?- I used a 50 w 12 v ac transformer winding as a choke, just for a test), and none of these sounded good. I use to notice this on certain frequencies, and often a male voice sounds as if had put the speaker into a big plastic can. 

Otherwise, I run it active, with the Zen amp driving the Visatons, and Sony the Betas, via DIY active crossovers at 12 db/oct. By replacing resistors I could change and try different frequencies, from 50 Hz to around 300 Hz. 50 Hz was too low, and anything more than 100-120 Hz or so started to sound bad.

Graham, thank you for the support. Most probably next weekend I will try your suggestion. By the way, congratulations for the new Spirit! Impressive, Even tough there are not less than 5 drivers on the baffle, I like that it is tall and slim. Wide baffles may sound better, but WAF falls rapidly.

Thanks a lot,

Vix

[painkiller]

I really think that the problem with a crossoverless or a 1st order crossed bass driver is that you get an unpleasant lower midrange hump in the response unless the drivers are high Q and you have a wide baffle. A low Q driver must be crossed low, or they will sound boomy and "muddy" up the midrange. All in all I think your problem is the frequency response and not the driver in itself.

On the other hand I was not pleased with the Alphas on their own, with a 1st order crossover. They needed a 2nd order around 100Hz to sound ok. But not with the T-bass. It's way better than digital EQ.

I use to notice this on certain frequencies, and often a male voice sounds as if had put the speaker into a big plastic can. 

That sounds bad, but I'm not quite sure what you mean. It sounds more like an upper midrange problem.   

[Graham Maynard]

Hi painkiller,

I agree with your comments, and I'm keeping fingers crossed that Vix will have some success with my suggested values for taming response at and above 100Hz.

I don't keep notes of everyone's systems, but if a Visaton B200 has a C+L crossover this too can induce a muddying peak due to Q induced phase change.  A series C of about 47uF (or equivalent C value at line input level) would probably be best with this driver until something starts to sound as if it is coming together.

Cheers ...... Graham.

[Martin G]

I'm still trying to get my brain around this circuit and it's components.
Would something like this work?

http://www.apexjr.com/images/AdireToroid.JPG

If it will work, can I use just one for both left and right woofers since it has dual secondaries or would I have to have one for each channel?

Thanks,

Martin.

[Graham Maynard]

Hi Martin,

Yes that transformer with an 8 ohm loudspeaker would be suitable to test whether you will like the circuit or not.

You will need one transformer per channel.

It is possible to separately drive dual voice coils with L and R output, so that a single woofer produces mono bass.
However, bass is recorded in stereo too, and mono-ing it will not only remove any differential energisation aspects of LF reproduction, but also reduce the level of LF experienced within the playback room.

(Indeed, mono-ing the LF is a good way of reducing room induced LF feedback for vinyl playback.)

Cheers ........ Graham.

[jeffac]

Hi Graham,

Whilst patiently waiting for my transformers to arrive, I've put a test baffle together and got carried away with cutting holes. Inspiration from your Spirit design, its 150 cm x 46 cm with

Saba 20 cm Alnico greencone wideband
Saba 10 cm Alnico greencone, open back tweeter, offset to one side to keep the Saba 20 and B200 close
B200
Alpha 15
Alpha 15

I've had the Saba's for a while and had other plans for them but in the spirit of playing, I thought I'd give this a go, however overambitious, over my head and complex due to driver number. Only have basic parameters for the Sabas but sensitivity from what I've read will be high and close to the B200s. Am I off the planet or it might this work. 

I'm thinking that the Saba 20 cm would be used to support the dropping B200 LF response as you've done and liked, and maybe even if sympathetic sonically with the B200, it might be interesting to run it even higher up. There is also the possibility of filling out the sub 1 kHz drop-off of the B200 with help from the top Alpha 15 as Richard has found to be very satisfying. So options a plenty here.  I think I'll leave the tweeter out of the equation initially but there would be potential to use it to 'augment' the B200 HF response if the phase plugs are removed and the coil former filled with foam, again as Richard is using presently based on your experimentation. Maybe the addition of this paper coned tweeter could add missing HF sparkle sympathetically whilst also providing some additional air, it being open backed.

TBH this is somewhat a grab bag of lots of your and others ideas, forgive me for this, but I am keen to play.

A question on the paralleled Alphas and your T-bass circuit.  I gather with a largish inductor of ~6 mH, that it will restrict them playing up into the 1 kHz territory employed by Richard. Yes/no? If yes, then I guess the solution would be to use it with the lower Alpha 15 only, with a small inductor used on the upper Alpha 15.

Thanks for any advice. If interested, below are links to frequency responses of Saba greencones, mine have Dortmund magnets but are manufactured slightly differently to these, circa 1955, but still in great nick. Hopefully they'll sound as good as they look. 

http://home.arcor.de/pfaue/klangkue/gruenwunder/galerie/saba_r_20_03/saba_r_20_03.htm
http://home.arcor.de/pfaue/klangkue/gruenwunder/galerie/saba_ht_01/saba_ht_01.htm

cheers.. Jeffac

just uploaded this pic of the 'in progress' test baffle minus the B200 still in use whilst I wait for parts

http://s337.photobucket.com/albums/n390/jeffc_pics/?action=view&current=p9040812.jpg

[Graham Maynard]

Looking good Jeffac.

Of course you can use the transformer circuit for just one driver, but it will be easy to try both in parallel to see which you prefer.

The Alpha mid phase response has potential to be better when using the circuit; also maximum displacement of both cones is better for LF.
With the Alphas in parallel a single 1 to 3mH series inductance would do between T-bass circuit and drivers.  May be tuned more afterwards.

I see there is a 1kHz peak on the Saba tweeter, so I suggest you wire an 8 to 10 ohm resistor in parallel with the voice coil to damp this.

Hope you will be enjoying the music soon.

Cheers ......... Graham.

[jeffac]

Hi Graham,

Thanks kindly for guidance on T-bass implementation using dual Alpha 15s, and on potential tweeter implementation too.  I'll try the Alphas as suggested with the B200 first, without the Sabas, to keep it simple and to try and get these working well together as Richard and others have done.

cheers.. Jeffac