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Old 25th January 2013, 08:23 PM   #21
epa is offline epa  Netherlands
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you are answering my question with a question.

i'm not pro or con a ppsl.
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Old 25th January 2013, 08:59 PM   #22
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Originally Posted by weltersys
If they are "push pull" (which cancels even order harmonic distortion, leaving the non-musical odd order distortion)
Quote:
Originally Posted by Inductor View Post
It's that a problem of the push-pull isobarics? Can you link to some notes or paper on that issue (isobaric distortions types). Regards.
I don't regard reducing even order harmonic distortion as a "problem", but when pushed hard, (as in the case of many professional applications) the result can be less musical sounding than if the even order distortion was there to mask the odd sounding odd order harmonics.
In general I am not a fan of isobaric loading, though it can be useful if space is limited and budget is not.

My opinions on PP in more detail are here:
Push Pull vs Normal Distortion Compared

Art
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Old 25th January 2013, 09:22 PM   #23
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Quote:
Originally Posted by sreten View Post
Hi,

Show me a design where whatever volume you use
for the slot is not best used internally, or any good
sub design where a slot would have any useful effect.

rgds, sreten.
Sreten,

A plenum can actually reduce the cabinet volume given up by the baffle and grille depth needed when front mounting long throw speakers.

My old L4 design from 1987 and L2 from 1992 used a large "V" plenum slot.
Kicked like it was horn loaded, but had the extension BR gave.

After the success of the L4, I noticed over the years that slot load designs became increasingly popular.
The difference between a plenum, slot, or a stubby horn is semantic, but there are dozens of commercial designs and hundreds of DIY using various slots, these are just a few popular current commercial examples:

Adamson T-21
Community's VLF218
D&B B2
EAWs SB1000 and SP 2001,
Fulcrum Acoustic's 2x15" 2x18" 2 x21"
Renkus-Heinz PN21SUB

All of the designers decided that the use of the plenum outweighed the internal volume displaced.

One primary advantage of a plenum slot is it allows the driver front panel to be smaller than front loading would allow.

The plenum creates an acoustic bandpass, reducing all harmonic distortion.

If one subscribes to a desire for reducing even order harmonic distortion, mounting the pair of speakers "push pull" in a plenum is more effective to that end than front mounting the speakers.

The plenum provides some mass loading, responsible for a subjective increase in "punch".

Opposing speakers cancel vibrational forces, subs using plenums won't "walk" like front loaded speakers do.

There are probably many other positive attributes for using plenum mounts, all of which need to be weighed against the amount (if any) of cabinet internal volume loss.

Art Welter
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Old 25th January 2013, 09:33 PM   #24
sreten is offline sreten  United Kingdom
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Hi,

As far as I'm concerned it has nothing to do with domestic AV subwoofers.

Any technical argument that says it does I'll contest as long as said
argument is one, not this device has one, is used for AV, so must work.

rgds, sreten.
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Old 25th January 2013, 10:36 PM   #25
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Quote:
Originally Posted by sreten View Post
Hi,

As far as I'm concerned it has nothing to do with domestic AV subwoofers.

Any technical argument that says it does I'll contest as long as said
argument is one, not this device has one, is used for AV, so must work.

rgds, sreten.
Sreten,

One can argue that "subs" with very high rate of sales (Bose) also have nothing to do with with domestic AV subwoofers, but that is a different argument.

I gave 6 technical points describing why plenums can be useful both in some domestic and large scale applications.

Care to contest them one by one, or are you more happy just dismissing them wholesale ?

Art
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