C/E/X PA Flat to 30 (FT30) PA TH Awesomeness

[djk]

It seemed pretty straight forward to me (too) when I came up with the idea in the late 80s.

Stack height for my system adds up to 102" (optimum), or 92" (alternate).

Optimum:

http://i56.photobucket.com/albums/g1...CoePA-2009.jpg

Alternate:

http://i56.photobucket.com/albums/g1...ch/COE08-3.jpg

Another issue is set-up. The alternate can be done by one man, the optimum requires something to stand on, or extra help.

[weltersys]

Originally Posted by jwmbro

Does that mean a 109dB/2.83V/8Ω compression driver is 50% efficient? Will hornloading the compression driver increase the sensitivity and efficiency even further? Sorry for going off topic.

A rating of 109dB/2.83V/8Ω is probably measured on a horn of some type. Horns limit the dispersion to a smaller radiated area, raising the on axis sensitivity.

As a woofer array size increases it becomes a virtual 1/4 space radiation instead of half space.

Arrays of woofers that are large compared to the wavelength create directivity, increasing on axis level while reducing off axis level.
The efficiency remains the same, but where the sound goes has changed.

[CRESCENDO]

Originally Posted by djk

Their PUKK-218 is within an inch or so in every dimension of my original dual 15 PPSL.

Is there any other advantage (aside from the additional 2 or so dB @ 30Hz) with using the ~$400 BMS drivers? Tonality differences?

Also, might you be able to guess any major differences with your 151269 PPSL vs. my 15LF-2 PPSL, sound/output/SQ-wise?

[CRESCENDO]

djk:

From what many others say and love about THs, they bloom @ war volume. How are PPSL at war volume?

[Djim]

Originally Posted by Pasi

No idea who designed HGW-10.

What comes to "copying DJK's design" that is always open for discussion. Yes, since he came up with that design long long time ago it can of course be considered as copying. But let's see what you guys can come up with same criterias what i was given and how different result you will end up with, just for fun.

1. Width needs to bee exactly 700mm to allow stacking and flying with Ersa Major array which was allready designed before starting sub design.

2. 2x 18" Reflex sub in push-pull configuration.
and
3. When ground stacking, 2 subs need to give right height (Ersa Major horns above average listening plane) for tops without anything extra added to stack. With or without groundstacking frame. Stack cannot be higher than 2350 mm with 2 subs and 2 tops.

Best regards,
Pasi

Sorry Pasi, it wasn’t meant as a personal accusation. I do understand your designing limits that made the outcome very similar. But my remark was meant cynical towards Ohm as a company. The fact is when a commercial company, like Ohm, releases a loudspeaker which shows many similarities to what have been discussed and shared over internet for years (with explanations, diagrams and pictures) it is asking for at least some cynicism. And I appreciate your willingness to open your cards...

[djk]

"From what many others say and love about THs, they bloom @ war volume. How are PPSL at war volume? "

Interesting that you ask.

The actual driver seen in my photos is the Eminence 15711, a custom design. The Martin #1844 is a driver that is available and fits my design quite well, even though the box wasn't designed for it.

With the 15711 the box is actually mis-tuned at lower volume levels, the Qts is a bit too low. What I found when you want to 'jam' an alignment you can pretend the Qts is a bit higher than it really is (because the motor is more powerful than what you need), but no more than about 15%~20%. When you start to pound it then the BL starts to drop off, the Qts goes up, and the cabinet comes into alignment. I guess you could call that 'blooming', it picks up more bass. The PP loading also seems to clean up a lot of the muddy sounds you get from a more conventional layout that is overdriven. PPSL sounds much cleaner all the way up to clipping.

[Pasi]

Originally Posted by Djim

Sorry Pasi, it wasn’t meant as a personal accusation. I do understand your designing limits that made the outcome very similar. But my remark was meant cynical towards Ohm as a company. The fact is when a commercial company, like Ohm, releases a loudspeaker which shows many similarities to what have been discussed and shared over internet for years (with explanations, diagrams and pictures) it is asking for at least some cynicism. And I appreciate your willingness to open your cards...

No worries and no reason for apologies. I understand your point of view and i'm also interested to know how that 10" sub ended up to our product range as i wasn't working with Ohm back then. At the moment it looks like it came from one of our customer but i'll keep you posted when i find out more.

In my opinion in general, it is bit dangerous to start saying that someone copied some other especially at these days as most new cabinets are just bit different versions from decade old designs and principles. There is limited amount of ways of doing for example 2x18" direct radiating sub. Or for example Danley Sound Labs and Renkus-Heinz using same idea of common horn. Danley knows it as Synergy horn and Renkus-Heinz as Co-Entrant horn. Same idea, bit different approaches. Most of these "modern" inventions have been discovered before 1970s anyway.

I found this out with these PUKK subs as i tought that i'm creating bit different and original looking box, but then got cold shower which pulled me back to earth when i found out that DJK has used this same idea more than 20 years ago. But was he the first...? I've now found out that quite many companies use this same design in their subs.

[Djim]

Originally Posted by Pasi

In my opinion in general, it is bit dangerous to start saying that someone copied some other especially at these days as most new cabinets are just bit different versions from decade old designs and principles. There is limited amount of ways of doing for example 2x18" direct radiating sub. Or for example Danley Sound Labs and Renkus-Heinz using same idea of common horn. Danley knows it as Synergy horn and Renkus-Heinz as Co-Entrant horn. Same idea, bit different approaches. Most of these "modern" inventions have been discovered before 1970s anyway.

I know, I do have some books/magazines (50ties/60ties) with ‘old’ designs that now and then see daylight again. About the origin of PP I have no clue. To me it was EV Voice MTS-1 for PA and in Hifi it was (don’t fall of your chair) Jamo. They released some PP’s during the eighties in their “PP” series (how original).



Crescendo, about war volume... use PP's in a TH concept and control their Xmax with old MFB techniques from Philips and you have everything you want: Low, loud, less THD and fully auto control of their mechanical limits...

[djk]

"To me it was EV Voice MTS-1 for PA "

Which they built after I talked with Tom Gallagher of Electro-Voice at a trade show. My original thought was to make something like the MTS-1, but with a horn-loaded 10 or 12. I decided that as a one-box system it was too heavy to hoist up in the air for good coverage. The MTS-1 tried to crossover at 800hz to a compression driver, I don't think that was the best thing to do. It was kind of funny that Tom was sending people over to talk to me at that show when they wanted plans to build MTL subwoofers.

The first PP system I saw was the 70s vintage Audio Pro design (see previous photo link), but it was co-planar and less than optimum in my opinion. The 80s vintage KEF 104.2 with its coupled cavity (BP4) design was PP, but also less than optimum in my opinion.

http://www.froerup.dk/jan/stereo/diverse/kef_104_2..jpg

[djk]

To get a bit more on topic:

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