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Old 3rd April 2010, 12:44 AM   #1
Pashley is offline Pashley  Canada
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Default Aperiodic loading for sub?

As long as you have the space and don't have to move them, transmission line subs look very good. I am wondering if an aperiodic enclosure might give some of the same benefits.

For example, Perfectionist Audio claim their TL "coffin" sub gives under 1% THD and +-1 Db response from 10 Hz-240Hz, and 95 Db SPL for 1W/1 meter. 64 watts would then give 113 Db, which should be more than enough. Construction looks simple enough. Too good to be true?
Perfectionist Audio Subwoofer

In theory, aperiodic loading looks good. Decades back, I had Dynaco A25s that used that; they were awfully good for their era and price point. Done right, it looks as though this could achieve something like the smooth extension of a transmission line design in a far smaller box. However, doing it right does not look easy. There do not seem to be readily available modelling tools as there are for other enclosures; it seems to be largely a build then tune process.

Any one tried this sort of design? Anyone know of good tools for modelling an aperiodic enclosure?
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Old 3rd April 2010, 06:51 AM   #2
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If someone would get Martin a set of valid data for the effects of stuffing densities above 1 pound/ft^3, i'm sure his worksheets would do a good job. Other than that it is guess, cut & try & tune.

I have built a number of quite successful aperiodic subs in situations where i couldn't live with the box volume really needed.

As to the Perfectionist, i came up with a (VERY) similar design that predates it, so am very familiar -- both these are based on the work done by Bud Fried for the Model H. The sensitivity of the B139 is 96 dB with 11 VRMS in, so 95 dB 1w is VERY optimistic... more like 95 dB 15 watts...

dave
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Old 6th April 2010, 01:38 AM   #3
FE3T is offline FE3T  Norway
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Quote:
Originally Posted by planet10 View Post
I have built a number of quite successful aperiodic subs in situations where i couldn't live with the box volume really needed.
How about utilising an aperiodic membrane to use Low Q woofers in an IB like prosject?

I have a number of 15" subwoofers with a QTS of 0,35 wich i have considered using in my loft playing down trougth openings in my ceiling.
The orginal idea was too use sealed boxes, but maybe with aperiodic membranes i could either place them in front the woofercones or with small boxes place the membranes behind the woofers

Click the image to open in full size.

Illustration are from car use, but just imagine loft instead of trunk
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Old 6th April 2010, 03:05 AM   #4
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I've not built the 2nd kind of aperiodic box. It is how the Dynaco A35/A50, and at least one of the NAIM speakers were loaded. Downside is a bigger box.

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Old 7th April 2010, 06:38 AM   #5
Pashley is offline Pashley  Canada
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Quote:
Originally Posted by planet10 View Post
I've not built the 2nd kind of aperiodic box. It is how the Dynaco A35/A50, and at least one of the NAIM speakers were loaded. Downside is a bigger box.
My understanding was that one advantage was smaller box than needed for the usual sealed or vented alignments. See for example:
Aperiodic Speaker Enclosure Design
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Old 7th April 2010, 06:47 AM   #6
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In the case of the 3 speakers mentioned they are creating their own outside world for the aperiodic port instead of using the outside world (the latter allowing for a smaller box)

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