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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 14th April 2018, 09:58 PM   #791
weltersys is offline weltersys  United States
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Quote:
Originally Posted by Cableaddict View Post
I'm still confused.

1)Unless you want some extension above 120 Hz, I STILL don't understand the reason to build a PPSL, as opposed to a simple push-pull, especially if the box is going to be simple vented.
2)(I also don't understand why anyone would want to run a sub over 120Hz, but that's a different issue.)
3)Having read this entire thread seventeen thousand times, and every other thread I could Google on PPSL, (there aren't many) it still sounds like maybe the slot minimizes some "even higher" frequencies & so MAYBE lessens some higher odd-order harmonics, but Art is adamant that this is not the case.
4)So can someone explain this in a simple way?
5)Forget the choices of sealed, BR, or Horn. In fact, just assume the box will be vented, as the bulk of this thread shows / talks about.
6)For someone like me, running the boxes at maybe 40 - 100 Hz, does PPSL have some advantage over my NON-slot loaded push-pull experiment?
7)With my 2X12" experiment, the sound becomes cleaner, but it still doesn't have the punch I currently associate with a horn. (especially at higher volumes) Does the slot somehow help with that? I don't see how, since that "horn loaded" punch & clarity (AFAIK) comes from having less cone excursion.
1)Notice that the rather large plenum needed for push pull 18" results in almost +4dB gain at 100 Hz as opposed to a simple push-pullas can be seen in the first screen shot in post #786.
2)Lifting lightweight small top boxes that are not capable of LF output that would keep up with the bass speakers is one reason anybody that has lifted heavy cabinets understands.
3) Push-pull will cancel even order harmonics due to suspension and magnetic differences in the driver's forward and backward stroke, the large series of "suck-outs" the plenum causes will reduce upper harmonics in those frequency ranges.
Perhaps you'll get the second part of the above on the 17,001 reading, but I won't hold my breath ;^).
4)Deep nulls=less harmonics.
5) The bulk of this thread refers to cabinets with a plenum, the plenum is a peaky upper bass horn, don't forget that choice. The bulk of the thread deals with 12" and 15" cabinets, resulting in upper peaks that are higher and more narrow than the 10" x 18" plenum Mark 100 introduced recently.
7)See item 1. Re-read post #786. Look at the crap screen prints again, the fuzzy pictures contains the information that you seem to overlook.
Note that a standard BR upper response in the 100 Hz region is the same as sealed, but the addition of a plenum changes the upper response.
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Old 14th April 2018, 10:04 PM   #792
Cableaddict is offline Cableaddict
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Quote:
Originally Posted by weltersys View Post
1)Notice that the rather large plenum needed for push pull 18" results in almost +4dB gain at 100 Hz as opposed to a simple push-pullas can be seen in the first screen shot in post #786.
2)Lifting lightweight small top boxes that are not capable of LF output that would keep up with the bass speakers is one reason anybody that has lifted heavy cabinets understands.
3) Push-pull will cancel even order harmonics due to suspension and magnetic differences in the driver's forward and backward stroke, the large series of "suck-outs" the plenum causes will reduce upper harmonics in those frequency ranges.
Perhaps you'll get the second part of the above on the 17,001 reading, but I won't hold my breath ;^).
4)Deep nulls=less harmonics.
5) The bulk of this thread refers to cabinets with a plenum, the plenum is a peaky upper bass horn, don't forget that choice. The bulk of the thread deals with 12" and 15" cabinets, resulting in upper peaks that are higher and more narrow than the 10" x 18" plenum Mark 100 introduced recently.
7)See item 1. Re-read post #786. Look at the crap screen prints again, the fuzzy pictures contains the information that you seem to overlook.
Note that a standard BR upper response in the 100 Hz region is the same as sealed, but the addition of a plenum changes the upper response.
And once again, why would I care about response above 100Hz?
Do you not understand my question?

If I'm crossing to my tops at 100Hz, I want my subs to be 3dB DOWN at 100Hz. Why the heck would I choose a design that boost this are, then just have to sculpt it back out with EQ? (Possibly screwing up the sound of my tops in the process?)

As for HARMONIC distortion, a "simple P-P design already minimizes a lot, so is the plenum even "betterer," somehow?

My questions still have not been answered, and no, not in those other posts, either.


And again, (Do I really have to repeat this?) How is a PPSL bass reflex design "The best sub I've ever heard" according to some very knowledgable guys, if horns are so much better in so many ways? (except LF extension.)

Last edited by Cableaddict; 14th April 2018 at 10:09 PM.
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Old 14th April 2018, 11:14 PM   #793
weltersys is offline weltersys  United States
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Quote:
Originally Posted by Cableaddict View Post
1)I also don't understand why anyone would want to run a sub over 120Hz...why would I care about response above 100Hz?
2)If I'm crossing to my tops at 100Hz, I want my subs to be 3dB DOWN at 100Hz. Why the heck would I choose a design that boost this are, then just have to sculpt it back out with EQ? (Possibly screwing up the sound of my tops in the process?)
3)As for HARMONIC distortion, a "simple P-P design already minimizes a lot, so is the plenum even "betterer," somehow?
4)My questions still have not been answered, and no, not in those other posts, either.
5)How is a PPSL bass reflex design "The best sub I've ever heard" according to some very knowledgable guys, if horns are so much better in so many ways? (except LF extension.)
1)Response does not "end" at the crossover point, so care should not either.
2) Look at the response of the vast majority of pop music produced over the last 5 decades and you will see a great rise in average and peak demands of kick, snare and bass in the 80-160 Hz region. Having the upper potential, and equalizing it down by 3dB (or more) allows that much more headroom for most music, without power compression.
I prefer to EQ any sub "flat" to it's F3, but have found a rising upper response fits the dynamics of most of the music I work with.
It is best if the raw response of the sub fits the average envelope of the music, so what works "best" for rock may not for some forms of EDM that require most energy a few octaves lower.
3)Yes, as explained before- the series of deep "suck-outs" AKA acoustic band pass filters the plenum causes above 100 Hz also reduces upper harmonics (and harmonic distortion) in those frequency ranges by the same amount as the dip.
4)They have been answered, but not understood- I understand that I'm not the best communicator, but you get what you pay for :^).
5)The last sub one builds is usually "The best sub I've ever heard" ;^).
For most home systems, PPSL certainly would be better in regards to LF extension than a vastly undersized FLH. In small rooms, the upper "punch" of an undersized FLH seldom is appreciated, as there is often too much low mid to begin with with 8 foot ceilings.

There are a large variety of PA cabinets that have found the upper gain of various plenum mountings useful, that subset is less than "standard" BR, but exceeds FLH by a good margin in recent decades.
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Old 17th April 2018, 01:51 AM   #794
Cableaddict is offline Cableaddict
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Quote:
Originally Posted by weltersys View Post
1)
5)The last sub one builds is usually "The best sub I've ever heard" ;^).
Is that a serious answer? It was a serious question.

Quote:
Originally Posted by weltersys View Post
1)
3)Yes, as explained before- the series of deep "suck-outs" AKA acoustic band pass filters the plenum causes above 100 Hz also reduces upper harmonics (and harmonic distortion) in those frequency ranges by the same amount as the dip.
and yet, when I have stated, for verification (based on all my reading here and elsewhere) that one apparent advantage of the PPSL design is a reduction in harmonic distortion, you have practically jumped all over me, saying this isn't so. This has happened TWICE, after which I decided you must be right and I'd forget about slot loading since it thus has no apparent benefit to me.

I am once again befuddled.


Quote:
Originally Posted by weltersys View Post
1)
4)They have been answered, but not understood- I understand that I'm not the best communicator, but you get what you pay for :^).
With respect, Art, they have not. Your a great guy, but a typical response from you goes like this: First, you tell me what I already know, (Making me feel even more clueless than I already am) then you answer a question I didn't actually ask. Then you stop, and no one else answers my question because they see a long response from you & figure it's over & done with.

For an obvious example, see below:

Quote:
Originally Posted by weltersys View Post
1)
5)....For most home systems, PPSL certainly would be better in regards to LF extension than a vastly undersized FLH
I am not asking about PPSL vs horns. I don't know how to possibly be more clear. I'm asking about PPSL versus a non- slot loaded P-P design.

If the slot DOES further reduce some distortion artifacts (I no longer have any idea, since if I say it does, you'll say it doesn't, and it I say it doesn't, you'll say it does...) but if it DOES, then:

It begs the question, how much reduction is enough, given other trade-offs?
A simple P-P already can reduce harmonic distortion by rather incredible amounts, and given that some folks actually PREFER the sound of that distortion, one would think this is then enough.

If, on the other hand, the slot reduces ALL distortions because it's a filter (something others have claimed, I have repeated for verification, & then you have adamantly told me is not the case) then the slot loading would of course be preferable to a simple P-P, even when the sub is used from 40 - 100 Hz.

But getting a simple, clear answer seems impossible. I'm right at the point where I don't care any longer and will just live with the garbage I already own.....
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Old 17th April 2018, 02:03 AM   #795
Cableaddict is offline Cableaddict
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Art, Let's try it this way:

you wrote:

"Push-pull will cancel even order harmonics due to suspension and magnetic differences in the driver's forward and backward stroke."

Which of course I already know.

then you continued with:

".... the large series of "suck-outs" the plenum causes will reduce upper harmonics in those frequency ranges."

And I have no idea what that means. In WHAT frequency ranges? Reduced upper harmonics in the upper harmonics? Huh?

If you just mean that the plenum reduces various groups of upper frequencies, well then YEAH, that's what I've been saying all along, and why I thought it made sense when other folks wrote that the slot reduces some odd-order harmonics, whereas regular p-p only reduces even order. But again, you have twice, very clearly told me this is not so.

PLEASE clarify.

Surely you're not suggesting that only even order harmonics (from the 40-100Hz fundamentals) fall into those "suck-outs?' Or are you?
I would find that very hard to believe.

Last edited by Cableaddict; 17th April 2018 at 02:06 AM.
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Old 17th April 2018, 06:00 AM   #796
weltersys is offline weltersys  United States
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Quote:
Originally Posted by Cableaddict View Post

".... the large series of "suck-outs" the plenum causes will reduce upper harmonics in those frequency ranges."

If you just mean that the plenum reduces various groups of upper frequencies, well then YEAH, that's what I've been saying all along, and why I thought it made sense when other folks wrote that the slot reduces some odd-order harmonics, whereas regular p-p only reduces even order.
PLEASE clarify.

Surely you're not suggesting that only even order harmonics (from the 40-100Hz fundamentals) fall into those "suck-outs?' Or are you?

If the slot DOES further reduce some distortion artifacts... how much reduction is enough, given other trade-offs?
No, not suggesting an acoustic band pass would apply to only even order harmonics.
An acoustic band pass will equally reduce even or odd order harmonics that happen to "fall in the hole".

That said, sorry if I gave the impression that the acoustic band pass "suck outs" from the plenum slot would greatly reduce distortion generated in the usual <100 Hz "sub" range.
From the limited distortion testing of PPSL I have seen, can't say the slot is a big deal, at least not with decent drivers, other than the increased upper sensitivity it provides.

In the simulation example below, the acoustic band pass dip extends from around 300 to 600 Hz.
Maximum excursion occurs around 50 Hz, and maximum distortion will also be generated from around that 1/3 octave range.
The plenum dip would only reduce 6th order and up from that range. Decent drivers don't have much distortion past third order, though there are plenty of PPSL using less than decent drivers being used much higher than 100 Hz..
Attached Images
File Type: png Shoehorn PPSL.png (148.3 KB, 36 views)

Last edited by weltersys; 17th April 2018 at 06:02 AM.
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