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In Reply to: RE: Push-Pull Double 15 Subwoofer Pic posted by Les Hudson on August 06, 2010 at 13:18:10
with respect to the simultaneous action of both the woofers upon the enclosed air mass.
Good job. Is this for PA , music or HT. What are the efficiency and frequency response specs ?
Follow Ups:
At the moment my friend is casting aside his $10,000.00 subwoofer in his theater room for this push-pull double 15. Frequency range 32hz - 400hz. I have to guess on sensitivity about 104db. Les Hudson
it should be called a woofer/lower midrange...true subwoofers go down to 20 Hz or lower and don't go above 50 to 80 Hz.
Brian Walsh
Remember, Central Fest is on Saturday, Sept. 4th, and you're invited! Email me for details.
I'm sure that everyone has a different definition as to what a true subwoofer is. My definition is one that covers as low as all of the source material being played and up to just before it becomes directional. I usually actively cross this sub over at about 75 hz and I have maybe 10,000 songs with no information below 32hz. This subwoofer has the ability to play from 20hz. - 400 hz. but I don't require that. Les Hudson
I disagree. Recorded music may not contain anything below 32 Hz except in rare cases, but low bass (below that) is present on many recordings in the form of venue information . An orchestra may not play a single note below 30 or 35 Hz, but the concert hall often conveys more.
One of my clients has electrostatic subwoofers that are flat to 20 Hz, I think 3 dB down at 14 Hz, with usable response to 8 Hz. Another client is considering a pair of Bruce Thigpen's unique rotary subwoofers ( http://www.rotarywoofer.com ) which are effectively flat to DC. Thigpen's product rolls off substantially above 30 Hz. That is a sub woofer, and for its performance is something of a bargain, in my opinion.
Brian Walsh
Remember, Central Fest is on Saturday, Sept. 4th, and you're invited! Email me for details.
If you want to reproduce hall rumble, just run the PPSL boxes sealed and EQ the low end (like BagEnd).
Edits: 08/12/10
Why not:
- Much lower sensitivity due to EQ
- I'm a purist. The less stuff in the chain the better. EQ is a lot of stuff. Lots more to be said.
- It does not address LF response, or more correctly the lack thereof, at low volumes.
Brian Walsh
Remember, Central Fest is on Saturday, Sept. 4th, and you're invited! Email me for details.
"Much lower sensitivity due to EQ"EQ does not affect sensitivity, box size does.
It makes no sense to build a huge box to have high sensitivity at 8~10hz.
It makes sense to build a medium sized box with high sensitivity above 40hz and EQ it to have output at 8~10hz. Hall effects (room rumble), may be low in frequency, but they are not particularly loud.
"It does not address LF response, or more correctly the lack thereof, at low volumes."
So you want loudness compensation?
"I'm a purist"
OK, if you say so.
"EQ is a lot of stuff"
EQ may be designed into an existing circuit, frequently without needing extra active stages.
Edits: 08/12/10 08/12/10 08/13/10
"It should be called a "Push-Push" subwoofer with respect to the simultaneous action of both the woofers upon the enclosed air mass."But that would also describe a system where both driver faced into the plenum (Linear BassVent), or both drivers faced out of the plenum (EV MTL2).
The term Push-Pull Slot-Loaded (PPSL) was coined to describe the design and differentiate it from other designs that use some of the same ideas. One driver's cone 'pushes' out of its frame, while the other driver's cone 'pulls' into its frame, thus 'push-pull'. The slot loaded describes the mounting of the drivers, to differentiate from 'clam-shell' push pull, drivers on different sides of the box (M&K), or drivers on one side of the box (TAD, EAW, Peavey, etc).
"Good job. Is this for PA , music or HT. What are the efficiency and frequency response specs ? "
I have built PPSL for all the functions you list, and car stereo too. Efficiency and frequency response are a function of the drivers selected, and the box size. PPSL may also be used on sealed, 4th order vented (mine have all been 6th order vented), IB, or dipole (after Linkwitz). Recently, Danley has used some push pull driver mountings in some of his newer tapped horn designs, and Wayne Parham has built a push pull version of a LAB 12 type design.
LF response is controlled by the T/S parameters of the drivers used, and the box size chosen. Upper response is controlled by the plenum response, mainly the depth of the cavity.
Edits: 08/08/10
Is there an advantage to having the drivers opposed rather than both facing into the cavity?
Thanks, Kyle.
yes, big difference. with a push-pull config. the drivers eliminate each others harmonics. Les Hudson
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