[AlliumPorrum]

I already have another discussion about my DIY bass plans, but since there are quite many questions and issues on the same thread, I decided to start another thread concerning just driver options. If you don't mind 

So, my question is; what 12" - 18" drivers would be the best options for this kind of setup:
- OB dipole bass unit, playing from 20hz to about 200hz
- upper range with Maggie 2.5R's
- since I want to have a good punch and dynamics, I think I'm going to use 4 drivers per channel
- fully active setup with DEQX's digital crossovers and driver/room correction

Few options I know are:
- GR Research 12" servo: http://gr-research.com/sw-12-16fr.aspx. But, for the best punch and dynamics, I think 15" would be a better option. And on the other hand; when using 8 drivers, the movement of the drivers will be quite minimal, so is there really much benefit from servo?
- Peerless SLS: http://www.madisoundspeakerstore.com/approx-12-woofers/peerless-sls-830669-12-woofer-coated-paper-cone/. Quite commonly used, reasonably priced option, and there also is a 15" model. Maybe not the best possible choice from the sound quality point of view?
- AE Speaker's Dipole15: http://www.aespeakers.com/drivers.php?driver_id=32. Good reviews all around, should go fine down to the 20hz. Quite expensive anyway, is it really worth the money??
- BMS's: http://www.bmspro.info/. Lots of different models, have a good reputation for OB driver.  What would be a best option for this setup, are they really worth the quite high price?

So, what would be the best option, both from the pure sound quality point of view, and also compared to the price?

All comments are highly appreciated!

[Rclark]

This guy used the Dipole 15's in his project but quickly switched

"I am going to substitute the Dipole 15 for a B & C 15NDL76."


"Why did you take the Dipole 15's out, they're great"

"Dipole 15 are out because even though they played very low with minimal EQ, I was not pleased with above 50hz performance.  Maybe it was just me, but I could never get them to sound pitch defined in their uper register.  I don't know if the high Q of the driver gives this effect or not.  Swapping in the low Q, B&C driver along with adding the Rythmik servos is giving me the best bass I have ever heard.  Besides, bringing the sealed driver in for the lowest octave adds back a sense of slam and visceral movement that is not possible without MANY MANY open baffle woofers"

http://www.audiocircle.com/index.php?topic=85662.80

[Rocket_Ronny]

The B&C driver is not a servo driver so how does work with a servo amp?

Rocket_Ronny

[richidoo]

Each of those drivers would be used differently. The Peerless and BMS or any standard low/mid Q driver intended for a box will need EQ to boost the output at low frequencies. Transient response and dynamics is good depending on driver, amp and wiring.

Drivers like AE Dipole series and Hawthorne Augie are designed for flat response in OB without EQ. They have high Qts like .7 to allow exaggerated cone excursion (floppy cones.) The extension and SPL are there, but the transient response is poor, so you lose detail.

The servo solves most of the problems. You get the LF extension, details, dynamics. I think you only need a pair per side, where the Peerless dynamics might benefit from 4, but 2 might be enough if you EQ it well.

Since you are planning active amp with digital EQ anyway, then you can eliminate the high Q drivers. If you want to spend the money on high end drivers and amps and wires for your bass drivers then you might be able to outperform the servos which use feedback to make medium quality parts perform like high end.

Push pull arrangement of any of these driver types will give lower 2nd harmonic distortion than all forward.

[Rclark]

The B&C driver is not a servo driver so how does work with a servo amp?

Rocket_Ronny

He uses sealed Rythmiks, seperate sealed subs, and the B&C's are in his speakers as dipoles.

[JohnR]

  AlliumPorrum, you said you didn't want to start more threads, yet here's another one asking the same question?? Anyway...

So, what would be the best option, both from the pure sound quality point of view, and also compared to the price?

Well, more is usually better, if you can fit them into your room. If you're talking about 4 drivers per side, you probably don't have a lot to worry about. I'd worry more about resonances (if using e.g. an H-frame), baffle stability and vibration, and placement. Where you do the crossover to the Maggies will make a big difference to these, so I'd suggest doing some measurements on those first to get a better idea of what you need to do.

Drivers like AE Dipole series and Hawthorne Augie are designed for flat response in OB without EQ. They have high Qts like .7 to allow exaggerated cone excursion (floppy cones.)

Rich, they aren't designed for flat response without EQ, Q of 0.7 just means they will be flat in an infinite baffle, in a small (i.e. typical) baffle they will still roll off at 6dB/octave below the dipole peak. Depending on listener distance the rolloff will stop at some frequency, but that is nothing to do with the driver per se. Drivers that (supposedly) don't need compensating EQ have much higher Q, like 3. A Q of 0.7 is your typical sealed box alignment, I've never heard anyone say that a Q of 0.7 is "floppy."

[Lazz]

Hi JohnR. I don't know the dipole 15, but doesn't the q of the driver go up when placed on the baffle. So if the dipole 15 has already a q of .7 perhaps thats why the bass is slightly ill defined. Not sure just thinking out loud. Regards.

[sfdoddsy]

You're going to have trouble using the DEQX to provide dipole correction in the bass. It doesn't provide enough boost.

My bass drivers (2 x Acoustic Elegance IB12s in an H-Frame) require 22db of boost. Drivers with a lower Qts such as those used in an Orion will need even more.

The GR Research servos would solve this problem because they have their own amps which provide the required EQ.

Alternatively you will need a separate EQ like a MiniDSP to do the EQ, or if you need an amp anyway, a Crown CDi or XTi series amp has built-in DSP and can do it.

I wouldn't bother with the Dipole 15 if you are only going up 200Hz. The AE IB12 or 15 will be just fine. Alternatively I'd look at the Dayton RS HO series, or the Titanics.

[lowtech]

You're going to have trouble using the DEQX to provide dipole correction in the bass. It doesn't provide enough boost.

Actually Steve, I had no such problem using my DEQX with a set of W-Frame dipole subs.  It would easily correct for the dipole loss down to 18Hz.  The drivers were SCC300.  YMMV.

[JohnR]

Hi JohnR. I don't know the dipole 15, but doesn't the q of the driver go up when placed on the baffle. So if the dipole 15 has already a q of .7 perhaps thats why the bass is slightly ill defined. Not sure just thinking out loud. Regards.

I think you are thinking of placing a driver in a box. I was referring to Rich's comment about Q=0.7, the Dipole 12 has about that and the 15 has about 1 IIRC. With regard to "bass is slightly ill defined" I think you need to re-read the quote above again. Cheers

[Lazz]

My apologies. I sort of accidentaly cross referenced it with Richidoo's post.

{Drivers like AE Dipole series and Hawthorne Augie are designed for flat response in OB without EQ. They have high Qts like .7 to allow exaggerated cone excursion (floppy cones.) The extension and SPL are there, but the transient response is poor, so you lose detail.}

But I have read that the actual q does go higher when placed on a open baffle. I have never tried open so I cant speak from personal experience. Regards.

[JohnR]

But I have read that the actual q does go higher when placed on a open baffle.

Hm. Well, I'd appreciate a link, or further info, if you have it.

[studiotech]

Chiming in here.  The system described is mine.  I started with AE Dipole 15 and when I wanted MORE output down low than a single per baffle could provide, I decided to try a different plan of attack.  I was curious to try a high sensitivity, Low Q driver(like the B&C) for bass on the baffle augmented by the sealed servos below 50-60Hz or however low I could safely EQ the new low Q woofer.  Turns out that I liked that sound better than that of the Dipole alone.  The high sensitivity is nice too because rather than having to boost a lot at the low end of the woofer and possibly run out of headroom, some subtractive EQ can be applied to the top range of the driver to balance things out.

In no expert, so maybe there are other explanations, but the tightness and pitch definition in the bass that I get with the lower Q woofer is certainly better than that of the AE.  I did not think that a higher Q with such a low FS would affect the over 60Hz region, but it seems to have. I even tried the L-pad across the second coil of the Dipole 15 for an adjustable Q and it changed the measured response by a few dB and sounded a little clearer, but not as good as what I ended up with.  Now, one has to be careful with these type of comparisons because to many people, less real low end response can be interpreted as sounding more defined and tighter.  So take whatever I say with a grain of salt, but I did spend a lot of time experimenting, measuring and evaluating all possible options with the AE Dipole.  I really wanted to keep it, I mean damn that thing is sexy looking and I like to support the little guy making great products.  If I had the money, i would have used the AE TD15M in place of the B&C, but with the discount I get at PE, the price difference was not in AE's favor and AE delivery times can be very uncertain.

Greg

[sfdoddsy]

Actually Steve, I had no such problem using my DEQX with a set of W-Frame dipole subs.  It would easily correct for the dipole loss down to 18Hz.  The drivers were SCC300.  YMMV.

I may have been misinformed. Happens a lot to me these days.

[Davey]

Hm. Well, I'd appreciate a link, or further info, if you have it.

Maybe he's referring to a Ripol configuration.....or similar?

http://www.lautsprechershop.de/index_hifi_en.htm?http://www.lautsprechershop.de/hifi/ripol_en.htm

The only way to cause an increase in Q is to mount in a box or an open-baffle configuration/construction that creates some sort of appreciable air loading.

Cheers,

Dave.

[JohnR]

The only way to cause an increase in Q is to mount in a box or an open-baffle configuration/construction that creates some sort of appreciable air loading.

Oh OK, thanks. Another thing I've been meaning to try ...

[sfdoddsy]

I'm giving this a try. Apparently has a similar effect.

http://www.enjoythemusic.com/diy/0911/slot_loaded_open_baffle_speaker.htm

[fdandrews]

I heard Mr. Pass' system with the slot loaded woofer at this years Burning Amp. I am planning to build my own version. The bass sounded good even in a room obviously not intended for hi-fi, and by putting the slot next to the floor and the driver behind the open baffle it is less visually intrusive.

[JohnR]

In no expert, so maybe there are other explanations, but the tightness and pitch definition in the bass that I get with the lower Q woofer is certainly better than that of the AE.  I did not think that a higher Q with such a low FS would affect the over 60Hz region, but it seems to have. I even tried the L-pad across the second coil of the Dipole 15 for an adjustable Q and it changed the measured response by a few dB and sounded a little clearer, but not as good as what I ended up with.  Now, one has to be careful with these type of comparisons because to many people, less real low end response can be interpreted as sounding more defined and tighter.  So take whatever I say with a grain of salt, but I did spend a lot of time experimenting, measuring and evaluating all possible options with the AE Dipole.

G'day Greg, I had sort of lost touch with your project so this is interesting. Just curious whether you tried highpassing the Dipole15 to cross to the sealed sub at any point?

[sfdoddsy]

I heard Mr. Pass' system with the slot loaded woofer at this years Burning Amp. I am planning to build my own version. The bass sounded good even in a room obviously not intended for hi-fi, and by putting the slot next to the floor and the driver behind the open baffle it is less visually intrusive.

Mine is going to be clear perspex, so probably not less intrusive. But the size and force cancellation have appeal.