[Early B.]

What you are describing isn't exclusive to Servo dipole bass.  Some of us have been using dipole woofers for more than a decade and what you describe is what I've been hearing for a very long time.  Welcome to the club, albeit a little late.

That's great for you. However, I'm referring to servo subs, not merely dipole woofers. Servo technology has made significant improvements in the past decade.

[Rclark]

As an outside observer, it seems that non-servo OB subs and non-servo OB woofer drivers have also become quite advanced. Just sayin. Case in point is StudioTech's famous thread with his famous speaker build. He has B&C 15's in his frame, not GR servo 12's. He does have Rythmik sealed subs as low low end backup though, but that just emphasises that there are alternatives, and that you don't have to have servo's to have the best of the best. Must be a fabulous system.

Again, as an outsider. If OB servo's were the best possible, it seems he would have put those in the frame.

[lowtech]

That's great for you. However, I'm referring to servo subs, not merely dipole woofers. Servo technology has made significant improvements in the past decade.

It's good to believe in stuff.  That said, I don't believe in the tooth fairy even if the emperor does.  Just saying so... doesn't make it so.

[Davey]

Servo systems can't increase physical capabilities of a driver.  For bass duties with all other things being equal, I'll take two 12" non-servo drivers over two 10" servo-corrected drivers any day.

Closed-loop systems make more sense....IMO....in the traditional, boxed sub-woofer role rather than dipole configurations, since that's a much tougher environment for a driver to operate.

Another interesting thing I've noticed is that some servo-woofer advocates are not proponents of negative-feedback usage in electronics.  I find that rather funny.


Danny,

Deceleration is acceleration...with a negative magnitude.  Motor strength has a role to play in stopping cone movement too.

Cheers,

Dave.

[stevenkelby]

For bass duties with all other things being equal, I'll take two 12" non-servo drivers over two 10" servo-corrected drivers any day.

Would you take Max SPL over sound quality? Or am I missing something?

Thanks,

Steve.

[Davey]

Steve,

Well, you're assuming sound quality is better with the servo configuration.  That may or not be the case.    Remember the 12" drivers will be working less hard to create the same SPL and thus producing less distortion.  (Actually about 2.5db less hard....which may not seem like much, but it's decent amount.)

Remember also that the higher the quality of the driver used, the less error correction should be required.  So, in effect, poorer performing drivers have more potential benefit from servo correction than quality drivers.

Cheers,

Dave.

[stevenkelby]

I see your point now, thanks

[sfdoddsy]

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.

Danny is being disingenuous here.

A decent dipole sub can easily hit 105db somewhere in the bass. At high enough frequencies they will output more than a monopole. Mine (2 x AE IB12s) will theoretically do 113 db at 71Hz and 104 at 50Hz. However they will only do around 80db at 20Hz.

So while his GR subs can probably hit 105db, and can also probably play flat to 20Hz, they can't do both at the same time.

In spite of this being pointed out numerous times, he persists in fudging in the manner above.

Frankly, his (and his acolytes) constant hyping of everything he makes and consequent slagging off of every other manufacturer is rather tiresome and why on some respected forums mention of his products is specifically (and uniquely) banned.

It makes many people dismiss all of his products as nothing but hot air.

I recommended his servo subs in the OP's other thread, but I did so grudgingly for the reasons above.

[JohnR]

OK, gotcha. I just want to add that an OB servo sub is gonna sound very different from the same woofer/servo amp if it's built in a box.

Well... right. Box subs and OB subs sound different. I can see the reasons why a boxed sub would benefit from servo as there's nothing you can do in designing the driver to remove the compression of the air in the box. With a driver in free air, though, it's different... This thread has pretty much convinced me that servos for OB are basically a gimmick. (Not that I was about to buy any any time soon anyway, I have enough OB drivers to last me a while...)

[Rclark]

Another thing that has me "baffled" as I just thought of it.. Does the bass in music have a "braking" and "accelerating" phase? I think, logically, I'd prefer a driver that could just follow the signal as closely as possible.

[JohnR]

That is super light weight for a 12" woofer if that is correct. It must have a really small motor structure to hit those T/S parameters with that light weight moving mass.

It's an underhung motor. Hello.

So you get less stored energy, but less electrical control too.

Your driver has a Qes of 1 and Qts of 0.748. The Lambda-designed Dipole12 has Qes of 0.73 and Qts of 0.68. I wonder how you define "less electrical control" exactly.

You can't even compare the specs. It is a complete system.

Well, you were the one blathering on about mms.

And the inductance of the voice coil is not really relevant

The paper by Wiggins says that it is. Your claim now is that none of the T/S parameters are relevant either, if I understand correctly.

[stevenkelby]

So while his GR subs can probably hit 105db, and can also probably play flat to 20Hz, they can't do both at the same time.

In spite of this being pointed out numerous times, he persists in fudging in the manner above.

I'm not exactly impartial, as I own his servo subs in a Super V, but I would never claim that they had the best bass in the world unless I had compared them myself to all of the competition, and I haven't.

I don't want to defend Danny or attacking anyone else, but I am very curious and would like to understand peoples viewpoints.

Saying that, I've never felt it implied that they will play flat to 20Hz at 105db (at the listening position btw, not at 1m like most dB measurements are taken. Danny says they will hit 105dB, and they will also hit 105dB. He never said it will do both at the same time and it's never seemed to me that he has implied it. That's just me though.

Frankly, his (and his acolytes) constant hyping of everything he makes and consequent slagging off of every other manufacturer is rather tiresome and why on some respected forums mention of his products is specifically (and uniquely) banned.

It makes many people dismiss all of his products as nothing but hot air.

This is the first I'm hearing of it. Who are his acolytes? Maybe his product is "hyped" because it is "the best"? Is that possible in your eyes? How are people including Danny supposed to respond when someone asks for a direct comparison?

On which forums is mention of his product banned?

It makes many people dismiss all of his products as nothing but hot air.

Maybe many people are missing out

This thread has pretty much convinced me that servos for OB are basically a gimmick.

That's pretty small minded for someone with your experience. What specifically convinced you that servos in OB are a gimmick? Don't believe everything you read on the internet...

Best regards,

Steve.

[Rclark]

Danny is being disingenuous here.

A decent dipole sub can easily hit 105db somewhere in the bass. At high enough frequencies they will output more than a monopole. Mine (2 x AE IB12s) will theoretically do 113 db at 71Hz and 104 at 50Hz. However they will only do around 80db at 20Hz.

So while his GR subs can probably hit 105db, and can also probably play flat to 20Hz, they can't do both at the same time.

In spite of this being pointed out numerous times, he persists in fudging in the manner above.

Frankly, his (and his acolytes) constant hyping of everything he makes and consequent slagging off of every other manufacturer is rather tiresome and why on some respected forums mention of his products is specifically (and uniquely) banned.

It makes many people dismiss all of his products as nothing but hot air.

I recommended his servo subs in the OP's other thread, but I did so grudgingly for the reasons above.

There is a gentleman called StigErik on diyaudio.com who has an OB subwoofer array, I want to get this right, but I believe it's sixteen either 18 or 21 inch drivers, and he can't get much lower than 20 hz. Mind you this is a room full of subs.

[JohnR]

Another thing that has me "baffled" as I just thought of it.. Does the bass in music have a "braking" and "accelerating" phase? I think, logically, I'd prefer a driver that could just follow the signal as closely as possible.

You're thinking intuitively, not logically. Put a lowpass filter on any driver and its impulse response goes to pot.

[JohnR]

That's pretty small minded for someone with your experience. What specifically convinced you that servos in OB are a gimmick? Don't believe everything you read on the internet...

Steven, I said why, right in the post that you quoted (although you left that part out). Did you read what I wrote?

[Rclark]

You're thinking intuitively, not logically. Put a lowpass filter on any driver and its impulse response goes to pot.

got it. Makes sense.

[JohnR]

There is a gentleman called StigErik on diyaudio.com who has an OB subwoofer array, I want to get this right, but I believe it's sixteen either 18 or 21 inch drivers, and he can't get much lower than 20 hz. Mind you this is a room full of subs.

IIRC there are four columns, it's not really the same as a "room full of subs." But if you want high output into the teens, don't expect to get there with OB, everything is working against you. I found 30 to be pretty much the sweet spot... as they say, YMMV........

[Rclark]

I wanted to say wall of subs instead, either way it is a massive and imposing, room dominating setup. And not that <20hz bass truly matters that much anyway, it's just that his system is proof that with OB, low bass is effectively the impossible dream. I'm sure everything above 20hz is capable of being quite ridiculously loud though, with his setup.

Danny has suggested in the past that with his (Danny's GR) OB setup you get to have your cake and eat it too, but StigErik nailed that coffin shut in my book.

Hell, going back to StudioTech, even he has a couple sealed subs for impact...

[JohnR]

Hell, going back to StudioTech, even he has a couple sealed subs for impact...

I don't think that's what he said. "Impact" is not in the 20-30 Hz region.

[Rclark]

You are correct. He has them there for low bass extension.