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A Thread for those interested in PPSL enclosures
A Thread for those interested in PPSL enclosures
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Old Yesterday, 02:20 AM   #801
weltersys is offline weltersys  United States
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Quote:
Originally Posted by Cableaddict View Post
A) I still can't figure if, for a Band / small DJ system like mine, PPSL has any benefits over a "simple" P-P. Again, I'm referring to something like this:
EAW FR250z
If I am going to LPF the subs at, say 120 Hz, would changing that EAW sub to PPSL, and keeping the internal volume the same , have any sonic benefit?

B)Dennis at Radian suggests I might solve me "anemic sound in the low mids" problem not by using more tops' cone area, but by raising my subs' LPF an octave or two. This goes against EVERYTHING I've ever believed or read, but I have to consider it.

I think it's safe to add three important points, on top of that very impressive measurement he (Mark100 did.
1: While that test showed a surprisingly large change, it might be less significant with certain high-end drivers, which have been designed to minimize such non linearities. Of course, it will still help.
2: Evidently, some folks actually LIKE the sound of even order harmonic distortion. I don't get it, at all, but it's a fact. It certainly does sound "louder," so, well, there's that, I guess.
3: As I've been "discussing" earlier in this thread, you can get "about" the same reduction of even order distortion with a simple P-P design. Art has implied that PPSL might be slightly better, but it's a mind-numbing thing to understand. The main point is that there are other possible benefits, to using an actual slot-loading. Which brings us back to all of my recent questions.
A) If the drivers used have a lot of even order distortion, a "simple" P-P will reduce that distortion. Unfortunately, drivers with lots of even order distortion also generally have lots of odd order distortion also, so THD may not be reduced by much at all.
PP drivers mounted in a plenum will increase the upper bass output, "every little bit helps", especially if suffering from anemic low mids ;^).
B) Because most Band / small DJ system's subs are not elevated from the floor, running them higher than 100 Hz will make them sound "muddy" when the meat bags stand in front of them. Much higher than 100 Hz and you will hear lower vocal range and instruments "walking" between the floor mounted and raised tops.
If the bass cabinets are elevated above head level, and the drivers are run within their linear range, nothing wrong with running to 200, 500, or even 800 Hz.
As an example, Clair Brothers (and Audio Analyst's) S4 cabinets used for major concerts from the 1970's through around 2000 (of the thousands built, many are still in use) crossed at 200 Hz between 2 x18" and 4 x10", with most tours using no additional ground plane "subs".
By today's standards, many would consider that proportion of LF/LM to be "anemic", but if you happened to attend concerts last century, you may consider the current LF "haystack" to be LM (low-mid) "anemic".
Times and program material change.. The program material, the subs potential output and sound quality compared to the low mid output and sound quality really determines the optimum crossover frequency, but if you are not going to co-locate the LF with the top cabinets, best to keep the crossover around 100 Hz.
1) Mark 100's distortion tests had no "large changes", distortion was quite low for either push-push or push-pull. I certainly would not be able to tell them apart at the levels he tested at.
2)Rock, funk, hip-hop, and every form of pop music popular for the last six decades or so is reliant on distortion as part of "the sound". Tube amps and the usual stage speakers have heaping helpings of harmonic distortion, and sound engineers often add even more in when they find the level too low.
That said, I'd prefer to use clean speakers than distorted speakers for sound reinforcement, there is generally more than enough to go around without adding more to the mix.
3)My tests with a "simple" P-P" using LAB12 drivers showed a reduction of even order distortion with that driver, but no reduction in THD when overdriven. Either way was acceptable up to around Xmax, though I preferred the sound of "normal" over PP above Xmax.

I have also explained that I find the upper gain provided by a "slot", or "plenum" or "V-load" to be useful in a mind-numbing number of posts ;^).

Art
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Old Yesterday, 03:53 AM   #802
Cableaddict is offline Cableaddict
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Thanks, Art. Very good point about the subs being on the floor.

But of course, that then completely contradicts this:

Quote:
Originally Posted by weltersys View Post
A)
PP drivers mounted in a plenum will increase the upper bass output, "every little bit helps", especially if suffering from anemic low mids ;^).
And as much as you THINK you've explained that business, you have not. You have STATED it, and you've posted some numbers (and some graphs that are too small or too fuzzy to actually read) that somehow relate to it which I'm sure were very helpful to anyone who ALREADY understands what's going on, but I guarantee you there is not "explanation. Nowhere in the entire thread. Well except the part were you say it minimizes harmonics and then later say that it doesn't.

And every time I ask it, hoping once again that SOMEONE ELSE might just give me the simple answer, you derail this endeavor by stating that it's already been explained. With all due respect, THIS IS GETTING OLD.
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Old Yesterday, 03:58 AM   #803
Cableaddict is offline Cableaddict
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Quote:
Originally Posted by weltersys View Post

3)My tests with a "simple" P-P" using LAB12 drivers showed a reduction of even order distortion with that driver, but no reduction in THD when overdriven. Either way was acceptable up to around Xmax, though I preferred the sound of "normal" over PP above Xmax.
And as I've stated before (perhaps you have forgotten) I don't give a rat's patootie what happens above Xmax. Why is that even part of the discussion?

And what's acceptable to you evidently isn't to me. As I've ALSO stated several times before. (perhaps you've forgotten?) I've done my own tests, with simple P-P and the difference was jaw-dropping. Granted, using only mid-level drivers, but I'm not going further with this as I'd be repeating myself.


And I STILL don't have a clue what a plenum will do for my P-P subs, in my particular setup. I fear I never will.
But I'm glad some folks around here feel really good about themselves.
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Old Yesterday, 04:23 AM   #804
weltersys is offline weltersys  United States
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Quote:
Originally Posted by Cableaddict View Post
1)And as I've stated before (perhaps you have forgotten) I don't give a rat's patootie what happens above Xmax. Why is that even part of the discussion?

2)I've done my own tests, with simple P-P and the difference was jaw-dropping. Granted, using only mid-level drivers, but I'm not going further with this as I'd be repeating myself.
1)Most "mid-level drivers" exceed Xmax at a fraction of their rated power level, so when you approach amp clipping, Xmax is often exceeded by a good margin, so it's part of a discussion regarding distortion, which you seem to be very concerned about.
2) Please do share what a "jaw dropping" difference looks like with some distortion charts.
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Old Yesterday, 10:39 AM   #805
Lunchietey is offline Lunchietey  Australia
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The above few posts all kind of say the same thing.

PP is probably a sound idea for getting better performance from mid level drivers.

Beyond xmax is a contentious issue. It all depends on whether you push your drivers to their limits. If you've designed and plotted your cabs and use appropriate limiting and filtering you should not have an issue.

It IS However interesting that IF you do hit a cone travel limit for whatever reason, they will both equally sound as unhappy as each other.

@weltersys I've built a dual 12" bass bin years ago (drivers stacked vertically, ports on the bottom) crossed to a very small sealed back mid array at 500hz and it was surprisingly good for mobile DJ work, not one single mention of it apart from positive comments or that the tops were ridiculously small for their volume level! Would absolutely not do this with a single 18 though.

Last edited by Lunchietey; Yesterday at 10:44 AM.
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