[Danny Richie]

    Davey,

You didn't want the Behringer speaker to participate in the subjective comparison. You wanted them so that you could measure each network and prove that they were different, but they were not, as you discovered. And thanks again for fixing that shipping damage. 

Lowtech,  I didn't post incorrect technical information about the DEQX.

[Danny Richie]

Oh ok, I did not know that they are "your" products. I surely understand your point.

So, let's not compare them to any other option, but just solve few issues I don't understand yet:

- Many have said (also on this forum) that 2 GR's per side would be more than enough in dipole setup. On the other hand, it is also often said that due the acoustic realities, even 4 x 12" is not gonna give very strong bass in dipole and at least 15's or 18's should be used to get real punch on dynamic music. What's your comment on this? Can GR's really give so much more punch that you can use half less of them? If, why?
- If I would use 4 GR's per side, the movement of drivers with normal listening levels should be quite minimal. And of course, that is a good thing from sound quality point of view. But doesn't this make servo functionality quite useless, compared to "normal" 1 driver subwoofer setup where driver moves a lot?

Okay, Let me put it this way. I used a pair of SW-12-16FR servo controlled woofers in an open baffle speaker at RMAF as the lower drivers in a pair of speakers that I was demonstrating there. We measured them hitting 105db peaks in our listening room during the replay of a recording drum track. It was a high quality SPL meter that was sitting on my leg while I was seated in the listening area. They also played flat to 20Hz and were -3db down in the teens. 

And the stopping power and control of the servo system is quite evident even at lower volumes. Differences in resolution are not subtle regardless of volume.

[AlliumPorrum]

Danny, I have heard what you just said about RMAF, I just would like to understand the reasons for such performance? I mean; how come 2 of your drivers could give more output than 4 "normal" bass drivers in dipole setup? It is very hard to believe that 2 x 12" GR could match any setup with 4 x 15" or such.


EDIT: and Danny, previous questions about DEQX experiences were directed to you, not Davey as I first wroted...

[Danny Richie]

Danny, I have heard what you just said about RMAF, I just would like to understand the reasons for such performance? I mean; how come 2 of your drivers could give more output than 4 "normal" bass drivers in dipole setup? It is very hard to believe that 2 x 12" GR could match any setup with 4 x 15" or such.


EDIT: and Danny, previous questions about DEQX experiences were directed to you, not Davey as I first wroted...

Output at a given frequency can be simply calculated back to surface area and sweep volume (or X-Max). The lower you go the more air you have to move to maintain the same SPL level.

The problem you get into with most woofers in an open baffle is loss of low frequency extension. They need a transform circuit or a lot of added gain from somewhere to increase power in an area where they are already down in output. And I don't know of too many plate amps out there with built in transform circuits. You can use something like a DEQX to EQ the lower end, but look at the expense of that. Plus it still isn't something that you want in the signal path to your main speakers.

The real key is not which woofer will hit the loudest SPL level at 20Hz. If that was the goal then no need for open baffle bass. We could just start horn loading woofers tuned to 20Hz and use lots of them. If the goal is sound quality then the real key is about the control factor. It's how fast can the woofer recover from a loud SPL peak at a given frequency. Getting away from cabinet panel resonances and room resonances is also a big deal. That's why everyone likes open baffle bass.

As far is DEQX and similar systems, I just don't feel the quality is there yet with any of those devices. I am involved in a effort to release a product that does what devices like the DEQX can do, but on a performance scale comparable to the top level DAC's. It is a work in progress and does involve some of my 8" servo controlled subs. You can read about it here: http://www.audiocircle.com/index.php?topic=111297.0  My involvement is not on the development end and it is not going to be a GR Research product.

[Davey]

I was interested in both measured accuracy of the alternate network and subjective differences.  I evaluated both.
Actually, the networks did measure slightly different.....but not enough to explain a subjective preference for one or the other.

Well off topic now.  Back to dipole bass drivers for Maggies. 
I don't see any reason why the GR Research drivers wouldn't work very well for this application.  Personally, I wouldn't utilize the companion servo amplifiers, and would prefer to build my own equalization network and amplifiers.  But either way should work fine.

I think the DEQX is a silly gadget.....but not for the same reasons Danny does.  The DEQX wouldn't be of interest to me because I think the concept of room "correction" via altering speaker system response is flawed.  And it wouldn't give me enough manual control of equalization requirements.  As far as the linear-phase crossover capability and other features not related to room correction and equalization, I believe it's probably an excellent unit.

Cheers,

Dave.

[Danny Richie]

I think the DEQX is a silly gadget.....but not for the same reasons Danny does.  The DEQX wouldn't be of interest to me because I think the concept of room "correction" via altering speaker system response is flawed.

Davey, I am totally with you on that aspect as well. Trying to correct for room related peaks and dips by altering the speakers output does not work. For one, all corrections are placement sensitive. So if one were to move the mic over a few inches then it will throw off all the corrections. Secondly, room reflections are a delayed arrival, and changing the amplitude of the output in a given area does not change the fact that there is a time delay involved in the reflection. 

[JohnR]

Davey, I am totally with you on that aspect as well. Trying to correct for room related peaks and dips by altering the speakers output does not work.

You've missed the point of the DEQX completely. If what the DEQX is doing is so bad, why are collaborating with HAL on doing the same thing?

[JohnR]

Two have high moving mass that hinders acceleration

The MMS of your SW12-16-FR is 104.9g. The Mms of the AE Dipole12 is 55g.

What's the Le of your driver?

[Danny Richie]

You've missed the point of the DEQX completely. If what the DEQX is doing is so bad, why are collaborating with HAL on doing the same thing?

It is not what it does that is bad. It is how it does it, and the quality of the parts and devices that are used in that unit that degrade the signal or interject noise. You have to look at the unit as a whole. It's all the overlooked little things like how in handles the A/C in the power supply etc.

I would love to see a product with the functionality of the DEQX using the best parts and latest DAC processes. That is what HAL is working on.

[JohnR]

It is not what it does that is bad. It is how it does it, and the quality of the parts and devices that are used in that unit that degrade the signal or interject noise. You have to look at the unit as a whole. It's all the overlooked little things like how in handles the A/C in the power supply etc.

I would love to see a product with the functionality of the DEQX using the best parts and latest DAC processes. That is what HAL is working on.

Based on my listening experiences, I don't agree with your continued dismissal of its quality. In fact, I don't think you've ever heard it used properly and are just speculating/badmouthing it in order to help you hype your supposed "best sounding but we've not even built it yet" product. That aside, can you be specific about the "how it does it" comment? What is it about "how it does it" that is "bad"?

[Danny Richie]

The MMS of your SW12-16-FR is 104.9g. The Mms of the AE Dipole12 is 55g.

Yeah, I have a tough time believing that a 12" woofer with an Fs of 25Hz is going to only have 55 grams of moving mass. That is close to the same weight as my 8" servo sub.

Most 12" subs have a moving mass in the 180 to 250 gram range if the Fs is that low.

Anyone independently measure the T/S parameters on those woofers?

[Danny Richie]

Based on my listening experiences, I don't agree with your continued dismissal of its quality. In fact, I don't think you've ever heard it used properly and are just speculating/badmouthing it in order to help you hype your supposed "best sounding but we've not even built it yet" product. That aside, can you be specific about the "how it does it" comment? What is it about "how it does it" that is "bad"?

John, It could be that our reference is different. To me they have all sounded bad. The DEQX is the best of the group so far though. And the group of people that I know and trust that have also given considerations to these products have also had the same opinions of them. It's not just me. To the guys with top level systems it's just a backwards step.

And I have not liked any of those digital crossover devices ever. They sound bad every time I listen to them. And I have listened to them ever since TacT started it ten or more years ago.

Before that I helped an engineer from Apple develope his own digital crossover back in 1999. He brought the whole system to my shop so that I could measure the speakers in my anechoic chamber. He wrote code and made corrections after each measurement. His system had limitations back then as well. I even let the guy demo it at a DIY get together that I hosted back in 2001. So a lot of people heard it.

So I guess you can say that for the last 14 years I haven't been that impressed with any digital correction system that I have heard, and I have been vocal about it for a long time. HAL just started his new project, BTW. So trust me, I am not bad mouthing something to hype something else. That's not me. And my past impression or expression of those products have NOTHING to do with me helping HAL in his new project.

[Davey]

Moving mass has nothing to do with acceleration.

Actually, when I perform a cross calculation using AE's published spec's for the Dipole-12 driver, the calculated Mms is 57.34 grams.  So, pretty close.  A smaller motor on those drivers so Mms that low doesn't seem unexpected.

Dave.

[lowtech]

Yeah, I have a tough time believing that a 12" woofer with an Fs of 25Hz is going to only have 55 grams of moving mass. That is close to the same weight as my 8" servo sub.

Most 12" subs have a moving mass in the 180 to 250 gram range if the Fs is that low.

Anyone independently measure the T/S parameters on those woofers?

I'm surprised you haven't measured them yourself since you seem to know so much about the details of every other competing product on the market and how nothing measures up to anything you peddle.

Btw, AE has been supplying woofers for over a decade.  Are you inferring that they are being deceptive about their published specifications or that they don't know how to measure the moving mass of them?

[Danny Richie]

Moving mass has nothing to do with acceleration.

Davey, if that were true then my woofers would be tweeters. But that is not a true statement.

The faster a driver can accelerate the higher it will play. That is why drivers with heaver moving masses will not play very high.

Try this little trick. Measure a small woofer and note its frequency response. Now add a little mass to it with clay or something then measure it again. Guess what? It doesn't play as high. Why? Too much moving mass, and too slow.

[Danny Richie]

Do you have an axe to grind or something Mike?

[Davey]

Try this little trick. Measure a small woofer and note its frequency response. Now add a little mass to it with clay or something then measure it again. Guess what? It doesn't play as high. Why? Too much moving mass, and too slow.

Danny,

Obviously.....because the motor is the same.

Sorry.  My point is that F=ma.

If you have a mass that is 50% larger you simply need a 50% larger motor to accelerate it.

Or conversely...as you allude to...a tweeter has a much lower moving mass than a woofer and thus the motor can be much weaker.  Theoretically, woofers could become tweeters.    In fact, not so theoretical.  The whole concept of (some) "full-range" drivers is about woofers acting as tweeters also, isn't it?

Cheers,

Dave.

[Rclark]

I remember reading a paper Dan Wiggins wrote for Adire Audio, and he said that moving mass had nothing to do with the speed of the woofer, I believe he said it was the woofer's inductance or something like that.

[Davey]

Rclark,

Exactly correct. 

In fact, I have that paper....along with some others....somewhere here on my computer.  If I can find them I'll post 'em.

http://www.diy-audio.narod.ru/litr/WooferSpeed.pdf

Dave.

[JohnR]

Actually, when I perform a cross calculation using AE's published spec's for the Dipole-12 driver, the calculated Mms is 57.34 grams.  So, pretty close.  A smaller motor on those drivers so Mms that low doesn't seem unexpected.

The specs are all consistent, as far as I can tell, so it's certainly possible. The sensitivity is much higher too, at 90 vs 84.7.