[bellicon]

In my 14 ft x 19 room I have a cloned pair of Gary Dahl’s two-way mains: Aurzahorns/Radian 745 Neo/Be drivers atop sealed GPA Altec 416-8B midwoofers.  http://i190.photobucket.com/albums/z179/paukenspieler/IMG_3087_zpse3b0ffd5.jpg

The Altecs go down to 70Hz, below which my pair of Rythmik 12" sealed servo subs take over. http://www.rythmikaudio.com/F12.html However, studies done by Todd Welti show conclusively that using 3 to 4 subs even in small rooms will better quell room modes  and thereby yield much smoother bass response throughout much of the listening area. See Figs 47 thru 53 bare out the results, and especially Figs. 40 and 41. https://www.harman.com/sites/default/files/white-paper/12/11/2015%20-%2006%3A12/files/multsubs.pdf

There’s also a large thread on the subject where Earl Geddes discusses his slightly different approach to multi-sub solutions for achieving much the same goals.
http://www.whatsbestforum.com/showthread.php?1005-Multiple-Subwoofer-Placement

Based on Welti’s conclusions to reduce room modes, I was then going to order the second pair of Rythmik 12" sealed subs for above system. Both pairs of subs can be daisy chained as all subs would have the Rythmik A370-XLR2 plate amp.  http://www.rythmikaudio.com/download/XLR2_sealed_quickguide.pdf

However, I also want to install another system in the same room placed along the short wall opposite my other system. The mains for that system would be a pair of ESLs, probably Quad 57s. http://dave-mills.yolasite.com/resources/a_a_esl57_mod_3_komprimiert.jpg However, even raising the Quads 15 to 20” (on Arcaci stands) and placed six feet from the rear wall, the Quads will only do down to 45Hz, ergo subs for that at last lower octave. But as ESLs, like open baffle speakers, are dipoles, I presume that a pair of dipole rather than sealed subs would sound best for the Quads. And I found a thread about Danny Richie’s dual 12” woofers in OB cabinets servo controlled by Brian Ding’s Rythmik plate amps fitted with a shelving filter.   http://www.rythmikaudio.com/GRci_OB.html http://www.rythmikaudio.com/GR_drivers.html

These dipole servo subs appear to be in use by one Quad 57 owner.  http://www.audiocircle.com/index.php?topic=139335.0

Questions:

1.) Even if with two pairs of subs, would my two way hybrid horn/sealed Altec midwoofer (monopole) speakers prefer all Rythmik 12" servo sealed box subs? Or would they sound equally fine if one pair were dual 12” Rythmik servo dipole subs?

And would the pair of dipole subs and pair of sealed box subs still reduce room modes as effectively as would two pairs of sealed box subs?

2.) Even if with two pairs of subs, would the Quad ESL (dipole) speakers prefer all dual 12” Rythmik servo dipole subs? Or would they sound equally fine if one pair were Rythmik 12" servo sealed box subs?

And would the sealed pair and the dipole pair of subs still reduce room modes as effectively as would two pairs of dipole subs?

3.) Assuming the answer to all the above is yes, there’s the matter of setting the crossover frequency for both pairs of subs, when using either pair of mains.

My Altec midwoofers play down to 70Hz. And the Quads, if placed 6 ft or so from the rear wall-and if raised 14 to 20” on (Arcaci) stands-should do down to between 45 and 40Hz.

Accordingly, I would initially set the sealed subs and the dipole subs plate amps to cross and be in phase with the Altec midwoofers and Quad ESLs, respectively, and confirm that each pair of subs works nicely with alone with its own mains. I would need to note these settings for each subwoofer pair to supply bass to its own mains, as the Rythmik plate amps have no memory for storing multiple groups of subwoofer settings.

Next, when using the pair of monopole mains I would then have to readjust the dipole subs to properly cross with and be in phase with mains.

Alternately, when using the pair of dipole mains I would then have to readjust the monopole subs to properly cross with and be in phase with those mains.

Now the question is, whether I use the pair of monopole or pair of dipole mains, regardless of well would you expect these two pair of daisy-chained dipole and monopole servo subs to sound together when both pairs (properly crossed and phase adjusted) are supplying bass for either pair mains?
 
And at the same time, regardless of which mains I’m playing, will a pair of dual 12” Rythmik servo controlled dipole subs work well with my pair of Rythmik 12" servo sealed subs to minimize room modes?

Last but not least, while deciding which part of which forum to place my post I found some unexpected controversy on the very notion of open baffle subs. A “stupid idea”?
http://www.diyaudio.com/forums/subwoofers/295060-open-baffle-subwoofer-design-4.html I’m probably not expert enough to even enter into a debate on this. However, in order to avoid making a bad investment and/or overcomplicating my subwoofer scheme, I am reaching out for experienced and impartial feedback on dipole subs, dual 12" Rythmik servo dipole subs in particular and using them simultaneously with Rythmik 12" sealed servo subs. Thank you. 


 

[Jonathon Janusz]

I won't even venture a guess about running all the subs on a single mono signal and getting them all to integrate perfectly with both systems simultaneously without moving them around depending on which system is playing, but the short answer to your main question is yes, dipole and monopole subs work very well together. 

As you brought up Danny, check out all of his most recent audio show setups as example of how it can work.  His setups ran dipoles in the front of the room with the main speakers, with sealed boxed subs in the rear of the room firing to the front.  If I remember correctly, the back subs were run 180 degrees phase and with the levels way down from the main subs, their job specifically to do what you are looking to get out of them and add just a little more foundation at the very bottom of the frequency range.  The dipole subs alone work very well, but there is clearly an improvement with the sealed subs in the back running along with them.

[bellicon]

This looks promising. Thanks. But for my room size and for using OB servo subs with Quad 57s or OBs like this http://stereotimes.com/post/pure-audio-project-trio10-mundorfamt-loudspeakers/ which dual 12" GR Research woofers do i use? And which of these OB enclosures would be best for my application for either of those mains and to work with the Rythmik sealed subs? http://www.hifizine.com/2012/12/subwoofer-origami/

[WC]

I don't have any subs yet, but have been doing quite a lot of research on which way to go. Here is what I understand to be the differences:

Dipole or OB subs provide a different sort of bass than sealed subs. Sealed subs provide bass which pressurizes a room to provide for bass and is typically run in a summed mono signal less than 80 Hz so as to make the bass non-localizable. They can be run as stereo subs at a higher frequency cutoff, but they would need to be located near your main speakers which is not always the best location for subs to provide even bass throughout the room. If you want the subs to work with home theater get the sealed subs, because they will provide the slam and impact that you won't get from OB subs.

If you are running OB speakers or similar speakers, OB subs will provide for the bass from those speakers run in stereo. They can be run up to 200 to 300 Hz if they are run in stereo. They do need space to work well like 3 ft from the nearest front or rear surface.

Do you have any room treatments?

 

[Jonathon Janusz]

This looks promising. Thanks. But for my room size and for using OB servo subs with Quad 57s or OBs like this http://stereotimes.com/post/pure-audio-project-trio10-mundorfamt-loudspeakers/ which dual 12" GR Research woofers do i use? And which of these OB enclosures would be best for my application for either of those mains and to work with the Rythmik sealed subs? http://www.hifizine.com/2012/12/subwoofer-origami/

If you are doing duals, go with a pair of these per side: http://gr-research.com/sw-12-08fr.aspx
With one of these per pair of drivers: http://gr-research.com/a370peq.aspx
In H frame enclosures like this: http://www.gr-research.com/pdf/H-frame%202.pdf

and you'll have what most people are using with the GR woofers to play flat to 20Hz with plenty of output into the teens.  If you adjust the box plans slightly, there seems to be some chatter in Danny's circle about some folks being happier with the results with both drivers facing front rather than opposing, but I'll leave you to read the threads on it to decide for yourself.

You could go with the 16-ohm versions of the drivers if you think you may ever do more than two per side (the A370 amp can handle three 16-ohm drivers per amp) in the future, and two pairs would still work great in the meantime.  Danny fairly recently added in the 8-ohm version of the OB drivers to get a little more output from dual driver setups than the 16-ohm version run as duals, as that seems to be what most people are doing with them.

The 8" versions of the drivers are good, but the general consensus is that 2 of the 12" drivers outperforms 3 of the 8" per side; the 8" theoretically have a slight advantage at the top of their frequency range, while the 12" are stronger below 20Hz.

[bellicon]

Dipole or OB subs provide a different sort of bass than sealed subs. Sealed subs provide bass which pressurizes a room to provide for bass and is typically run in a summed mono signal less than 80 Hz so as to make the bass non-localizable. They can be run as stereo subs at a higher frequency cutoff, but they would need to be located near your main speakers which is not always the best location for subs to provide even bass throughout the room. If you want the subs to work with home theater get the sealed subs, because they will provide the slam and impact that you won't get from OB subs.

If you are running OB speakers or similar speakers, OB subs will provide for the bass from those speakers run in stereo. They can be run up to 200 to 300 Hz if they are run in stereo. They do need space to work well like 3 ft from the nearest front or rear surface. Do you have any room treatments?

I will have two separate two-channel main speakers with their own DAC and amplifier. Both systems will be in the same 14 ft x 19 x 8 room. One pair will be a two way horn/midwoofer; the other pair either Quad ESLs or PAP OBs. Subs will be my pair of 12” sealed Rythmiks. And I will choose either another pair of same or a pair of dipole subs.

Both systems are for music only, no HT. However, I would want bass that provides whatever robustness and weight may exist in the CD track or 24 bit download. Presumably, this would be achieved using Jonathan’s suggestion. That is, again (?) assuming that dipole subs would be the better sounding (“master”) subs for the ESLs, as they too are dipoles, they share similar radiating patterns. Thus, the OB subs would be crossed with the ESLs to begin playing from perhaps 80Hz down to 40Hz, while the sealed (“slave”) subs would handle the last half octave or so.

As each pair of subs is asked to handle only a limited frequency range, wouldn’t the system and the room benefit from less IM distortion and less room modes by using two pairs of subs?     

Speaking of room modes, after the mains systems and subs are installed, I will be working with someone like Auralex to evaluate my room and install the appropriate materials, within my budget.   http://www.auralex.com/praf/

But why can’t the OB subs and/or sealed subs (if used together or not), below whichever pair of my main speakers-be used to play stereo bass, regardless of where I cross them with the main speakers?

Furthermore, has it actually been proven in listening tests that ESLs and OB mains sound better with (servoed) dipole subs than with (servoed) sealed subs? I don’t know anyone locally who’s done such listening tests.

 

[bellicon]

If you are doing duals, go with a pair of these per side: http://gr-research.com/sw-12-08fr.aspx With one of these per pair of drivers: http://gr-research.com/a370peq.aspx In H frame enclosures like this: http://www.gr-research.com/pdf/H-frame%202.pdf and you'll have what most people are using with the GR woofers to play flat to 20Hz with plenty of output into the teens. 

If you adjust the box plans slightly, there seems to be some chatter in Danny's circle about some folks being happier with the results with both drivers facing front rather than opposing, but I'll leave you to read the threads on it to decide for yourself.

You could go with the 16-ohm versions of the drivers if you think you may ever do more than two per side (the A370 amp can handle three 16-ohm drivers per amp) in the future, and two pairs would still work great in the meantime.  Danny fairly recently added in the 8-ohm version of the OB drivers to get a little more output from dual driver setups than the 16-ohm version run as duals, as that seems to be what most people are doing with them.

The 8" versions of the drivers are good, but the general consensus is that 2 of the 12" drivers outperforms 3 of the 8" per side; the 8" theoretically have a slight advantage at the top of their frequency range, while the 12" are stronger below 20Hz.

bdp24, who seems to be everywhere on the web, praises the Richie/ Ding OB servo sub-though providing little, if any, actual details about how well they actually sound with his Quad 57s-said that two pairs of those 12” drivers and a pair of the servo plate amps (with shelving filter) can be had for ~ $1500. A reasonable price.

I don’t have lots of time to experiment, much less for risking mistakes, as I’m way behind schedule with the entire system build. But what should there be any arguing over the two 12" drivers being front and back or front only mounted in an H-frame?

Also, please explain why H frame and not W frame-or Z frame sub that I heard about someone using-may be the preferred type of OB sub enclosure. 

You said that OB and sealed subs will work “very well together”. But according to Greebster at diyaudio.com, using them together won’t produce a cardioid bass pattern in the room, which apparently yields cancellation of modal events in the room.

If this is true, and since I already have one pair of Rythmik 12" sealed servo subs, does it make sense to get another pair of those subs and forget about OB servo subs? But how much will that matter to the ESL (dipole) speakers if both master and slave pairs of subs are monopoles?