Implementing the SW-12-16FR servo open baffle subwoofer driver

Snegrah · « **Reply #60 on:** 14 Jun 2008, 06:14 pm »

Danny:
I just built the OB5's and am having a good time with them. Can this sub set work with the OB5s? One or a pair of them? Right now there is a resonance or a "favored" frequency that is in the upper bass (don't know the hz.) and wonder if adding a sub will accentuate it. It's definitely the room. Regardless, I want to put in a sub!!!!!
Thanks,
Tom

Danny Richie · « **Reply #61 on:** 14 Jun 2008, 10:27 pm »

The free air sub will match well with the OB-5's but it isn't going to solve a room related issue.

It will be worth your time to solve the room issue. Then you'll enjoy everything all the more.

kyrill · « **Reply #62 on:** 15 Jun 2008, 10:15 am »

hi Danny

have you tried other dipole designs?

i am thinking ( as you suggested) to use the SW-12 for 100z and lower
. So if i put 2 in an OB like the Em. Physics CS2 what possible dimensions
are possible ( with some EQ?)

rythmik · « **Reply #63 on:** 15 Jun 2008, 04:17 pm »

I was in the Danny's room last weekend and took a few measurements on the sealed sub vs OB sub. I don't have biased towards one vs another. However, I would say the adjustment in OB sub and sealed sub is very different. A room has a natural boost below 20hz because of room reflection. For that reason, the best sound from a sealed box is obtained with a high damping on our plate amp so that it does not add any additional ringing to the one already created by the room. And one should try 28hz, 20hz, and 14hz extension setting so that it blends well with the room. I would not try to fight these reflections because 1) the wall reflections is the one gives the clue that we are in a room (such as music hall) vs in an outdoor open space, and 2) no sound absorbing material is effective at that low frequencies. On the other hand, the OB sub has a front and back cancellation and this cancellation happen within one cycles time at low end and a Q=0.5 would sound too dry at the bottom end. Therefore I recommend at least try mid damping setting on the plate amp or even try low damping, and preferrably 20hz/14hz. I would imagine OB sub is particularly suitable for rooms with lower ceilings and/or limited width. The front and rear walls presents the same problem to both sealed sub and OB sub.

richidoo · « **Reply #64 on:** 16 Jun 2008, 10:21 pm »

Brian and Danny,
I'm very interested in trying the subs in OB. But I'm still wondering how they will work with my external crossover. If I send a -12dB slope at 250Hz to the sub, it will be steepened by the crossover filter in the sub. I want to defeat the plate amps crossover completely. Can this be done? And if not, can you please explain why it is not advisable? If it's not possible, can you characterize what the rolloff is at highest freq and lowest slope settings?
Thanks
Rich

rythmik · « **Reply #65 on:** 17 Jun 2008, 03:13 pm »

Quote from: richidoo on 16 Jun 2008, 10:21 pm

Brian and Danny,
I'm very interested in trying the subs in OB. But I'm still wondering how they will work with my external crossover. If I send a -12dB slope at 250Hz to the sub, it will be steepened by the crossover filter in the sub. I want to defeat the plate amps crossover completely. Can this be done? And if not, can you please explain why it is not advisable? If it's not possible, can you characterize what the rolloff is at highest freq and lowest slope settings?
Thanks
Rich

The most robust xover is LR (typo here, Linkwitz-Riley) with 24db/24db slope, completely phase align that gives the main lobes directed front and back. Now if I want to deviate from R-L, which should I give up first, 24db/24db or phase alignment? In my opinion, it is 24db/24db, that is not as important as phase alignment. I would recommend xover at 200hz but not any higer because there will be some cavity resonance from a W frame,

To overcome that, we need 1) sound absorbing material on the cavity to reduce it, and 2) keep the xover lower so that the subwoofer won't excite that. And a steeper slope will definitely help, not hurt. I know some advocate less is better (including me), but in this xover business, it is the ears that really count. As for xover 250hz, you can do that with our shelving circuit installed. Danny is currently using that.

[EDIT] Danny, thanks I corrected my typo.

Danny Richie · « **Reply #66 on:** 17 Jun 2008, 03:55 pm »

Quote

I would recommend xover at 200hz but not any lower because there will be some cavity resonance from a W frame,

I think Brian meant that the crossover can be set at 200Hz but not any HIGHER. With the current W frame design the woofers don't play up high enough to excite or create a cavity resonance. Playing them higher would push them into a range to where a cavity resonance is possible.

richidoo · « **Reply #67 on:** 17 Jun 2008, 04:30 pm »

That makes sense. I think I can make 200Hz work fine, based on the FR plotted above. Then adjust xover and cabinet damping as necessary by ear.

One more question, I want to try them as OB of course, but is the 16ohm driver and plate amp able to be used in a sealed or reflex cabinet also? I would like to be able to experiment with different designs using the subs.
Thanks much guys
Rich

Tmantn · « **Reply #68 on:** 17 Jun 2008, 10:33 pm »

Danny,

What's on top of your OB Sub's? Would it be the OB array you have been alluding to in earlier threads?

Wil we see it at RMAF? aa aa aa

Danny Richie · « **Reply #69 on:** 17 Jun 2008, 10:54 pm »

Well, it is not an array, but it is all open baffle.

If all goes well you'll see some really cool stuff at RMAF this year from GR Research.

I went real overboard last year with LS-6's and LS-9's plus all of the one off, custom electronics from Dodd Audio and all that stuff. But this year I intend to top all of that.

HAL · « **Reply #70 on:** 18 Jun 2008, 02:31 am »

kyrill · « **Reply #71 on:** 18 Jun 2008, 10:06 am »

Quote from: kyrill on 15 Jun 2008, 10:15 am

hi Danny and or others

have you tried other dipole designs than the W?

i am thinking ( as you suggested) to use the SW-12 for 100z and lower
. So if i put 2 in an OB like the Em. Physics CS2 what possible dimensions
would you advise?( with some EQ?)

I ask these questions as yr drivers will be my first OB experience
kyrill

Danny Richie · « **Reply #72 on:** 18 Jun 2008, 05:03 pm »

I have not tried these in other OB baffle configurations yet.

I highly recommend the W frame design as it works really well and supports itself very well. Most flat baffle designs can have a support problem. If you want clean and tight bass response then it is very important that the movement of the box or baffle doesn't counter the movement of the woofers.

richidoo · « **Reply #73 on:** 18 Jun 2008, 05:09 pm »

Is there a difference if the woofers in the W baffle point up or down?

Danny Richie · « **Reply #74 on:** 18 Jun 2008, 06:12 pm »

Up or down? Are you asking about which way they face? If so then it really doesn't matter.

richidoo · « **Reply #75 on:** 18 Jun 2008, 07:21 pm »

Yes, thanks

rythmik · « **Reply #76 on:** 18 Jun 2008, 11:59 pm »

Someone reminds me a typo in my above post. The most reliable xover is L-R (or Linkwitz-Riley). It is a filter with two cascaded second order filters of Q=0.7 on both high pass and low pass filters. One can do a google to read more. It has two special characteristics: 1) It has completely flat response when implemented in circuit (that is assuming all speakers behave as ideal as circuit components), and 2) it maintain complete phase alignment between both sides of xover in both passband and in xover region. That means it can tolerate same amount of phase deviation in both positive and negative direction. The main contribution is 2). I really care less about 1) as that is only of theoretical interests for speakers. For instance, some company still use first order between sub and front (you know who), the phase difference at the xover point is 90 degrees. That means when there is additional 90 degree phase difference, it will make them completely out of phase between front speakers and sub. On the other hand, it takes -270 degree phase difference to make it out of phase. Without proper equipments to verify, it is easily to get +/- 90 degrees phase deviation from what we intend to achieve which means it is more difficult to tune in reality.

TRADERXFAN · « **Reply #77 on:** 19 Jun 2008, 01:12 pm »

Quote from: Danny on 14 Jun 2008, 04:56 pm

W frame cabinet plans have been posted.

http://www.gr-research.com/pdf/obsub.pdf

The guys that build these are going to be really pleased with just how well it sounds. This sub is really, REALLY, good.

Does this plan call for 3/4" mdf?

Also, are those 11" diameter holes?

Thanks
Tony

Danny Richie · « **Reply #78 on:** 19 Jun 2008, 02:29 pm »

Quote

Does this plan call for 3/4" mdf?

Also, are those 11" diameter holes?

Yes, and yes.

FlorianO · « **Reply #79 on:** 19 Jun 2008, 09:01 pm »

Quote from: rythmik on 17 Jun 2008, 03:13 pm

The most robust xover is LR (typo here, Linkwitz-Riley) with 24db/24db slope, completely phase align that gives the main lobes directed front and back. Now if I want to deviate from R-L, which should I give up first, 24db/24db or phase alignment? In my opinion, it is 24db/24db, that is not as important as phase alignment. I would recommend xover at 200hz but not any higer because there will be some cavity resonance from a W frame,

Brian,

In your originall A370PEQ pate amp post you showed the plate amp with XO freq of max 120Hz. You also subseq recommended an XO point not higher than -6dB @ 150 cycles (fair enough).

So, the question is: Is this a another plate amp, or a new version, or I am simply mixing things up?

An W OB bass unit with Direct Servo, EQable and good up to 200Hz (i.e. LR 12 or 24db XO @ _max_ 200Hz)... Now _that_ I would like to hear. And eventually use.