subwoofers with dual opposed drivers

[gnarly]

Still, my main questions stand:
Can this be done in a Vented Design?
Are design parameters treated as any other dual driver configuration?

Yes, i have done it with two drivers in a single vented box. And two separately enclosed sealed drivers.

Dual opposed is simply about having motor forces cancel each other to reduce (nearly eliminate) induced cabinet vibrations.
Doesn't matter whatever the sub type is....

Only way to fly (or should i say sub) imo

 

[ryanosaur]

FWIW the M&K and Perlisten Push-Pulls show a shared inner cabinet (Sealed), not separate compartments for each Driver.

Thank you both!

 

[Chromatischism]

Yes, i have done it with two drivers in a single vented box. And two separately enclosed sealed drivers.

Dual opposed is simply about having motor forces cancel each other to reduce (nearly eliminate) induced cabinet vibrations.
Doesn't matter whatever the sub type is....

Only way to fly (or should i say sub) imo

It depends on your goals. For home theater or theatrical-type music it is not the kind of sub I would use unless I had no choice but to keep things under control for roommates/neighbors.

Dual opposed vented is an interesting idea that I haven't seen done commercially yet.

 

[gnarly]

It depends on your goals. For home theater or theatrical-type music it is not the kind of sub I would use unless I had no choice but to keep things under control for roommates/neighbors.

Curious why you wouldn't use it for HT etc. ???

Seems to me it's a pure gain, no loss, type design.....even for regular hi-fi.
Although that said, if the sub isn't making much SPL, i can see that vibration reduction probably isn't much of an issue.

Dual opposed vented is an interesting idea that I haven't seen done commercially yet.

Here's one of mine....pict from testing stage, before paint and grill. (Sub on right is a JTR Orbitshifter)

Opposed vented sub designs have been around in the pro world for ages. For obvious vibrational reasons i guess...
The old EV MT4 being a prime example.

Oh, and Danley's announced Hyperion for home use, is dual opposed vented.

 

[Chromatischism]

Curious why you wouldn't use it for HT etc. ???

Seems to me it's a pure gain, no loss, type design.....even for regular hi-fi.

I tried dual opposed and decided it wasn't for me because I lost too much of the feel.

 

[gnarly]

I tried dual opposed and decided it wasn't for me because I lost too much of the feel.

Interesting. I may have experienced a bit of the same.

My dual opposed vented sub (PPSL), is basically two single vented boxes I had built, put into opposition in a single box.
The single vented boxes were a home run, so i duped them in the PPSL by doubling internal box volume and port size.

The leading attack edge of strong bass transients seemed a wee bit less with the PPSL than two stacked singles.

I dunno if that has to do with the nature of the wavefront emanating from the PPSL slot, or perhaps a potential reduction in distortion from the PPSL design.

PPSL stands for either push-push slot loaded, or push-pull slot loaded. Push-push is with the drivers facing each other clam shell, and push-pull is with the motor of one hanging in the slot, facing the cone of the other. (You probably know all that, but for others reading along, thought i should explain.)

Supposedly, push-pull helps cancel out non-linearities and reduce distortion (in addition to the dramatic overall vibration reduction).
So I measured the PPSL both ways, push-push and push-pull. Didn't see any significant distortion difference, but i did hear more motor noise with push-pull with a motor hanging in the slot.

So I've stuck with push-push.
Anyway, getting back to tactile feel.....
Again, i don't know what to think about the leading attack edge of strong bass transients.
I know from a lot of multi-way measurements and listening, that much of what i think is subwoofer transient response, is really full-range response combined with the sub.
And I know that harmonics from a sub are part of the full-range response...giving sub transients some bite, some attack.

The distortion plots of the PPSL were nicely low. Here's plots with processing in place.

SPL was a bit over 125 dB at 1m !

Maybe the cleanliness of the PPSL is reducing some pseudo transient behavior..... i simply dunno.
Never managed to test the single vented boxes for distortion at the same SPL level...hope to someday.

Hey, my favorite tactile feel track is AWOL Nation's "Sail"....that tune rattles nearly every body part when cranked Lol.
Personally, i think bass without tactile feel is not bass......

Oh, one last throw in....the MT-4 pro sound sub i posted a pict of......AC/DC's go-to subs

 

[lewdish]

It is both and it can be up to 50/50 depending on your room construction and whether you are using any isolation materials.

For example:

I had 2 Rythmik F12's for a number of years. The two were capable of shaking the room.

I changed to G22's which were not able to shake the room, despite having double the power.

The reason why is self-evident when sitting by the subs and playing a sweep starting in the 15-25 Hz range. The smaller, lighter, single-driver subs rock back and forth whereas the dual-driver G22 was almost completely inert.

I'm currently debating between the G25 & G22, have you tested the rumble filter on the G22 to achieve the room vibration? The G22 is cheaper and my room is large so I'm wondering which one I should go w/ esp since the G25 is about $1K more than the G22.

 

[jhaider]

Really dug most of this thread, guys. Thank you.
With the talk of dual opposed, I am curious to open the can-of-worms (possibly) and ask about the Push-Pull style from MK and being used by Perlisten.
Can this be employed in a Ported Cabinet, or only Sealed?
Does it matter in which direction the drivers are mounted? (Same baffle, opposite baffles (effectively dual opposed but with one driver motor in, the other motor out), etc...)
Do you need 2x Vas when designing?
Any other tidbits that can be shared?

Many thanks!

I’m not a fan of that configuration. It wastes a lot of space that could be usable cabinet volume, and while you do get the push-pull even order distortion benefit you don’t get the dual-opposed stability benefit.

Sealed vs vented really doesn’t matter here. You could also use passive radiators. You can use DO woofers and massively loaded up DO passive radiators, and stack a pallet full of Riedel’s finest on top without worrying about the sub shaking them to pieces.

As for modeling, yes model as 2 drivers, 1 box.

 

[ryanosaur]

I’m not a fan of that configuration. It wastes a lot of space that could be usable cabinet volume, and while you do get the push-pull even order distortion benefit you don’t get the dual-opposed stability benefit.

Sealed vs vented really doesn’t matter here. You could also use passive radiators. You can use DO woofers and massively loaded up DO passive radiators, and stack a pallet full of Riedel’s finest on top without worrying about the sub shaking them to pieces.

As for modeling, yes model as 2 drivers, 1 box.

I appreciate the input! Thank you.

 

[Chromatischism]

I'm currently debating between the G25 & G22, have you tested the rumble filter on the G22 to achieve the room vibration? The G22 is cheaper and my room is large so I'm wondering which one I should go w/ esp since the G25 is about $1K more than the G22.

Unless you have a mandate to reduce rumbles and vibrations and/or you have very specific space requirements, I would steer you away from dual-opposed subs in general. In my experience, those are the two problems they solve. If you don't have those problems, and if your room is large, you would be best served by a low-tuned ported sub.

 

[ivanj]

As far as live classical music goes:
1. Went to a performance of Beethoven's Missa Solemnus at London's Royal Albert Hall. When lowest notes on the organ 'kicked in', it made the air taught. I felt these frequencies in my body. I noticed no rattling of the building frame, chairs, other solid objects of the venue.
2, I had the same experience at an E.Power Biggs concert at Harvard in Cambridge, Massachusetts.
3. Finally, there is no rattling, rumbling of, eg., pews in St. Patrick's Cathedral in NYC when the organ accompanied services even at the lowest stops. Again, I felt it in my body.

My conclusion is that for my taste in music multiple (stereo) single driver subwoofers or the multiple dual drivers setup with the LPF set to 30-40 Hz and the electrostatics run full range would fit the bill. Comments?

I have the TV in another room for movies and stuff.

 

[Chromatischism]

My conclusion is that for my taste in music multiple (stereo) single driver subwoofers

Most music has the bass mixed in mono. This gives more powerful bass as two speakers can work together, in phase. If you were to set up a system that took bass not from a bass-managed output but from each speaker channel, and tuned the subs to individually work best at your seat, they would produce interference (peaks/dips) with each other when bass hits both of them. Because bass waves are greater than the distance between the subs, and even longer than the dimensions of the room, the solution to uneven bass is mono bass, along with delays + EQ to best align the subs together as one acoustic source.

or the multiple dual drivers setup with the LPF set to 30-40 Hz and the electrostatics run full range would fit the bill. Comments?

For the same reasons above, you don't want overlapping bass producers in the room that aren't integrated. I don't know what ES speakers you have (40 Hz, really?) but take the load off of them and cross them over at 60-80 Hz.

 

[Willem]

If you are combining subs with dipole speakers like electrostats it is more important than ever to deal with room modes, since the dipoles excite fewer of them, and hence the contrast with the subwoofers could be unattractively obvious. So I would always advice a combination of multiple mono subs and dsp room eq. I use Quad 2805 electrostats with a high pass filter around 80 Hz to give them a bit more headroom in a large listening space.

 

[DanielT]

As far as live classical music goes:
1. Went to a performance of Beethoven's Missa Solemnus at London's Royal Albert Hall. When lowest notes on the organ 'kicked in', it made the air taught. I felt these frequencies in my body. I noticed no rattling of the building frame, chairs, other solid objects of the venue.
2, I had the same experience at an E.Power Biggs concert at Harvard in Cambridge, Massachusetts.
3. Finally, there is no rattling, rumbling of, eg., pews in St. Patrick's Cathedral in NYC when the organ accompanied services even at the lowest stops. Again, I felt it in my body.

My conclusion is that for my taste in music multiple (stereo) single driver subwoofers or the multiple dual drivers setup with the LPF set to 30-40 Hz and the electrostatics run full range would fit the bill. Comments?

I have the TV in another room for movies and stuff.

Benefit several subwoofers, for example, reduce the problems with room modes. Not automatically,but it can facilitate solving those problems. Then sub must be integrated with the speakers in a way that makes sense, sounds good. A challenge in itself. Can be quite a challenge.

Several subwoofers, each one does not have to work so hard. Reduced audible sub-bass distortion. But that depends on the quality of the subwoofer. Not sure that is the case.Depends..

Below 80 Hz, you cannot locate where the sound is coming from. If you do, it's because the LP filter isn't steep enough (at least 24 dB is usually recommended) . Alternatively, a bit far-fetched, things at your subwoofer are vibrating and those are the sounds you're locating.

Subwoofer + EQ fix to FR=Good marriage.

Room modes - Wikipedia

en.wikipedia.org

 

[misterdog]

I don't know what ES speakers you have (40 Hz, really?)

My Quad 989's easily go there, especially after I mounted all the panels in solid steel (filled box section) frames, and reduced the signal distortion to 0.00025 %.
SMSL M400 >Topping Pre90 >Benchmark AHB2.
The panels are run naked with no dust covers or protective grilles (usual safety precautions disclaimer).

My 2 x 12" subs are powered by a MiniDSP plate amp, I can turn the subs off most of the time with no audible loss, only deep Synth bass and organ pipes go down below there.

One of my subs is an open baffle dipole to mirror the dipole ESL's.
Rear wave cancellation is an overrated worry IMO.

I also rebuilt the room to avoid any bass boom/rattle.

Frequency Response	37Hz - 21kHz (-6dB)
	33Hz - 23kHz (useable)
Distortion (100dB at 1m)	Above 1000Hz 0.15%
	Above 100Hz 0.5%
	Above 50Hz 1.0%

I strongly believe that my Quads have less distortion after my mods.

 

[sarumbear]

My Quad 989's easily go there, especially after I mounted all the panels in solid steel (filled box section) frames, and reduced the signal distortion to 0.00025 %.
SMSL M400 >Topping Pre90 >Benchmark AHB2.
The panels are run naked with no dust covers or protective grilles (usual safety precautions disclaimer).

My 2 x 12" subs are powered by a MiniDSP plate amp, I can turn the subs off most of the time with no audible loss, only deep Synth bass and organ pipes go down below there.

One of my subs is an open baffle dipole to mirror the dipole ESL's.
Rear wave cancellation is an overrated worry IMO.

I also rebuilt the room to avoid any bass boom/rattle.

Frequency Response	37Hz - 21kHz (-6dB)
	33Hz - 23kHz (useable)
Distortion (100dB at 1m)	Above 1000Hz 0.15%
	Above 100Hz 0.5%
	Above 50Hz 1.0%

I strongly believe that my Quads have less distortion after my mods.

Even the standard 989 can reproduce 40Hz as it has a bass boost around 50Hz. You may not hear it as boomy due to lack of a box but nevertheless the response is not even.

Quad ESL-989 electrostatic loudspeaker Measurements | Stereophile.com

Sidebar 3: Measurements Although the different kind of interaction between a panel speaker and the room can make it sound louder than its measured sensitivity would suggest, the Quad ESL-989 is still on the low side, at an estimated 83dB(B)/2.83V/m. Given its strict 100W power handling, this...

www.stereophile.com

 

[misterdog]

Even the standard 989 can reproduce 40Hz as it has a bass boost around 50Hz. You may not hear it as boomy due to lack of a box but nevertheless the response is not even.

I never claimed my system was perfect, though it is more perfect than most.

Call round for a listen.

 

[sarumbear]

I never claimed my system was perfect, though it is more perfect than most.

Call round for a listen.

I’m sure they sound nice. I used own a pair of 63.

 

[thewas]

Even the standard 989 can reproduce 40Hz as it has a bass boost around 50Hz. You may not hear it as boomy due to lack of a box but nevertheless the response is not even.

It should be kept in mind also that the nearfield bass measurements of Stereophile don't really say much about the bass response of such a dipole in a typical room as also JA correctly comments on the same page:

Second, my usual nearfield measurement of the low frequencies will not show the effect of the dipole cancellation, as the antiphase backwave increasingly wraps around to cancel the speaker's direct output with decreasing frequency. The peaked-up bass shown in fig.2 will therefore tend to be more flat in the farfield than it appears in this graph, with useful extension reaching below 40Hz, as LG found in his auditioning.

 

[Thomas_A]

Push-pull cancel out even order distortion. Don't know if that is good or not since odd-order is still there.

Push Pull vs Normal Distortion Compared

Having never seen an actual comparison of the same cabinet used as a push pull (PP) compared to a normal forward facing pair, decided to do it myself. Since comparative push-pull and push-push distortion measurements are hard to locate, thought it would be good to reference Mark100's more...

www.diyaudio.com