McKinney
I didn't know he's been gone going on 3 yrs now and the first 'In Memoriam' forum 'member'. I only recently started getting updates and haven't gotten around to going through it, but just now found three separate ones, starting at #1, so why is it broken up?
Anyway, yes, high quality driver designs with prosound specs are in a class of their own, but I wonder about all these consumer oriented PE, MCM/Newark?, etc, especially when used in multiples.
For sure, the inexpensive super low efficiency mobile audio drivers sound horrible to start with, but then the clientele in my locale would never notice any added distortion based on what emanates from them as they cruise along or use as lawn party speakers with all doors/whatever wide open.
GM
I didn't know he's been gone going on 3 yrs now and the first 'In Memoriam' forum 'member'. I only recently started getting updates and haven't gotten around to going through it, but just now found three separate ones, starting at #1, so why is it broken up?
Anyway, yes, high quality driver designs with prosound specs are in a class of their own, but I wonder about all these consumer oriented PE, MCM/Newark?, etc, especially when used in multiples.
For sure, the inexpensive super low efficiency mobile audio drivers sound horrible to start with, but then the clientele in my locale would never notice any added distortion based on what emanates from them as they cruise along or use as lawn party speakers with all doors/whatever wide open.
GM
Back in '98? I built a mini-Servodrive Contrabass while waiting for the two real Contrabass kits Tom offered the basslist.
Anyway, it had Avatar Adire 'basslist' 12" Shivas and 15" PRs tuned to 14 Hz in a square, somewhat tall [4 ft?], 10 ft^3 out of 3/4" Marine grade no void plywood [spec'd ~ the same as more current 19 mm BB and apple ply].
It cancelled out pretty good, but needed mass loading, so its 'finished' top was some custom cut, rebar reinforced concrete slabs held on with industrial velcro. The other thing was after break in I had to add a bit of weight [used tire lead weights] to one 12" to better match their Fs when the depth charges got loud enough to clip a MC500.
It was impressive for the day, but not surprisingly was no match for the 'real deal', which performance wise is little more than an expensive toy by today's standards.
GM
Here is a quote from XRK that is relevant from this thread: https://www.diyaudio.com/forums/solid-state/344540-alpha-nirvana-39w-8ohm-class-amp.html#post5958331
Push-pull will move the woofers from this pleasing distortion profile to a less pleasing one, just the characteristic Hugh is trying to not have in his amps.
dave
The World's Most Accurate Subwoofer? - YouTube
Apparently the worlds most accurate sub is a push pull!
How do we model a push pull design?
Apparently the worlds most accurate sub is a push pull!
How do we model a push pull design?
It is just 2 woofers in a box. The push-push part is completely executed with mechanical cleverness.
The best is likely a push-push as the active cancelation of the driver’s reactive energy tdramatically reduces the load on the bx (90%?). Carefully designed it largely takes the box walls out of the equation. As well, some benefit comes from the opposing woofers creating a more uniform omnidirectional dispersion patttern taking away the asymmetry of drivers only on one side, where th ebox creates a bit of a shadow.
I have the woofers and amps to recreate the stereo pair of push-push SDX10 subwoofers. They performed very well.
dave
The best is likely a push-push as the active cancelation of the driver’s reactive energy tdramatically reduces the load on the bx (90%?). Carefully designed it largely takes the box walls out of the equation. As well, some benefit comes from the opposing woofers creating a more uniform omnidirectional dispersion patttern taking away the asymmetry of drivers only on one side, where th ebox creates a bit of a shadow.
I have the woofers and amps to recreate the stereo pair of push-push SDX10 subwoofers. They performed very well.
dave
This was a slot loaded band pass sub - but push-push. It made some nice clean bass with a pair of 5.25in Tang Band 16ohm sub drivers in parallel.
Light as Air Slot Loaded Band Pass Sub
Light as Air Slot Loaded Band Pass Sub
The video was far to long to watch, but at one point they were talking about the quality of modern woofers getting to the point that servo wa snot really worthwhile. Such a woofer would get zero benefit from push-pull.
dave
X,
Jusy looking aat that it looks clear that the openin gis too large for it to be a bandpass. And the push-push requires the cabinet to create the coupling. Looks like thick foam-core, hardly stiff enuff to create sufficient coupling to get significant reactive enerrgy cancelation.
That does not mean that it doesn’t sound good, but that the descriptor is not accurate. Neither the band pass or the push-push.
dave
Jusy looking aat that it looks clear that the openin gis too large for it to be a bandpass. And the push-push requires the cabinet to create the coupling. Looks like thick foam-core, hardly stiff enuff to create sufficient coupling to get significant reactive enerrgy cancelation.
That does not mean that it doesn’t sound good, but that the descriptor is not accurate. Neither the band pass or the push-push.
dave
Push-pull designs reverse the mounting direction and polarity of one of the two drivers, which cancels out even order harmonic distortion, though leaves the odd orders unaffected.
Drivers without suspension and motor forward/backward non-linearities don't exhibit reduced even order harmonic distortion from the reversal.
Both push-pull or push-push designs model identically to any other using the same enclosed volume.
Push-pull or push-push slot loaded designs can be modeled in Hornresp, with the slot (plenum, shared chamber) modeled as a small "horn".
The plenum volume required for large woofers works as an acoustic band-pass, reducing upper harmonic distortion, regardless of the driver orientation.
Art
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The Akabak sim seems to show that it’s a 6th order alignment (which is a band pass). Just because the slot is on the larger side doesn’t mean that the sound wave there doesn’t interact with the cone. The 1in thick XPS is quite stiff - the drivers are coupled through a rigid thick XPS frame. Their opposing motion helps to cancel vibration. On the push push the forces go to the two 1 in thick sidewalls - the force that XPS panels can resist is quite strong. It’s not just like thick foam core as XPS insulation is stiff due to large moment of inertia and can support some weight.