I guess you've seen Bert Doppenbergs reference subwoofer? In the Origami-valley I guess. Anyway: PP-loading would give cleaner and more precise bass. I was a bit surpriced of the effect, and now I wouldn't even consider another loading principple. And it doesn't have to be with crappy drivers for effect only. My JBL 2226Hs just sounded more right than ever. The nice thing is that you choose box or no-box as you please.
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"My JBL 2226Hs just sounded more right than ever."
The aluminum shorting ring really reduces distortion in the midrange, but not in the bottom octaves, P-P loading takes care of that.
I assume most of you will have read the NP article on SL (slot-loaded) OB drivers?
The Slot Loaded Open Baffle Project Article By Nelson Pass
A natural progression would be to move to P-P loading, turning it into a PPSL. NP was able to show a 2.78dB gain from the 3:1 SL, the reduction in distortion from P-P would be like icing on the cake.
The aluminum shorting ring really reduces distortion in the midrange, but not in the bottom octaves, P-P loading takes care of that.
I assume most of you will have read the NP article on SL (slot-loaded) OB drivers?
The Slot Loaded Open Baffle Project Article By Nelson Pass
A natural progression would be to move to P-P loading, turning it into a PPSL. NP was able to show a 2.78dB gain from the 3:1 SL, the reduction in distortion from P-P would be like icing on the cake.
I did Push-Pull loading with my H-baffles as well. I measured about 90% reduction in 3rd harmonic distortion, and that's audible! 😛
I believe the reduction in 3rd harmonic is a function of the low-pass behavior of the slot cavity.
There is also an audible reduction in frequency modulation distortion as the cone is moving sideways rather than towards and away from you.
I experimented with trying to make an ESS Transar woofer with small cone drivers in the mid 70s, but didn't quite get it right. In the mid 80s I came up with my first dual 15 PPSL design, and never looked back.
The ESS Transar
There is also an audible reduction in frequency modulation distortion as the cone is moving sideways rather than towards and away from you.
I experimented with trying to make an ESS Transar woofer with small cone drivers in the mid 70s, but didn't quite get it right. In the mid 80s I came up with my first dual 15 PPSL design, and never looked back.
The ESS Transar
An externally hosted image should be here but it was not working when we last tested it.
"Is it possible to achieve adequate slot loading with a push pull config? "
My first PPSL had a 82.5 sq in exit slot driven by 270 sq in of cone area, a 3.27:1 ratio. The slot was only 5" wide and the magnet of the reversed driver was very close to the cone of the other driver. My designs are mostly 6th order vented (B6), intended for home theater and PA. Les Hudson has used them up to around 400hz for hi-fi, mated to large horns.
I am looking to an OB design with suitable 6 or 8 inch drivers for midrange use, hoping for 800hz on the upper end, probably like this:
http://i56.photobucket.com/albums/g196/dkleitsch/PPSLslanted6.gif
My first PPSL had a 82.5 sq in exit slot driven by 270 sq in of cone area, a 3.27:1 ratio. The slot was only 5" wide and the magnet of the reversed driver was very close to the cone of the other driver. My designs are mostly 6th order vented (B6), intended for home theater and PA. Les Hudson has used them up to around 400hz for hi-fi, mated to large horns.
I am looking to an OB design with suitable 6 or 8 inch drivers for midrange use, hoping for 800hz on the upper end, probably like this:
http://i56.photobucket.com/albums/g196/dkleitsch/PPSLslanted6.gif
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That is quite a lot of drivers (ref. your picture). Is it a stage system, lurking under the scene?
"Why would you slant the speaker-elements like this?"
It's something I wanted to try after Electro-Voice did this with one pair of 15s in a PA speaker.
I talked with an EV engineer at a trade show after I developed my original PPSL. Shortly afterward they came out with a PA speaker that had a slanted plenum. I never got a chance to hear one, but they did cross it at 800hz to a horn and compression driver. I assume the slant was done to try and improve the upper bandwidth as the depth of the cavity controls this. My thought when I made the thumbnail sketch above was to see how high I could push some surplus Aurasound 6s that are on the surplus market (I have not done this).
Madisound Speaker Store
Six of these in series-parallel would be about 100dB/2.83V/1M and about $8 each in that quantity.
It's something I wanted to try after Electro-Voice did this with one pair of 15s in a PA speaker.
I talked with an EV engineer at a trade show after I developed my original PPSL. Shortly afterward they came out with a PA speaker that had a slanted plenum. I never got a chance to hear one, but they did cross it at 800hz to a horn and compression driver. I assume the slant was done to try and improve the upper bandwidth as the depth of the cavity controls this. My thought when I made the thumbnail sketch above was to see how high I could push some surplus Aurasound 6s that are on the surplus market (I have not done this).
Madisound Speaker Store
Six of these in series-parallel would be about 100dB/2.83V/1M and about $8 each in that quantity.
The cavity looks just as deep as the other set up. The only difference I see is the upper speakers of the pairs have a lot more off axis response. If you compare the FR of the uppers at 45 degree versus 90 for the others, you'll see the uppers go higher.
Why don't you try that with 15" and let us know?
Why don't you try that with 15" and let us know?
Thanks. That is his personal system it seems. He tell that he plugged the opening of his horn-sub with this array. The reason was that he wanted better time-alignment between sub-bass and the rest. Not a problem in the digital domain, but he didn't want that.
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