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Old 19th January 2006, 03:00 PM   #1
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Join Date: Nov 2004
Default linkwitz transform

Can anyone generalize anything about the nature of this beast?
I've read the Linkwitz papers. I've looked into a few variants on
the idea. I've watched the threads here to see what sort of diy
options are in the works.

I'm getting a pretty clear of just what it is, but am still confused as to exactly where it is. I even read somewhere that the circuit, or some variant thereby, is already utilized in more "off the shelf" sub amps
than we realize. True? Just how proprietary is the design and why, if licencees are evidently able to incorporate it relatively inexpensively (rythmikaudio for one), is its appearance not more widespread? I would have expected Partsexpress to have LT versions of their house brand sub amps or at least add-on modules for its customers.

While I'm on the topic generally, why don't any parts suppliers (partsexpress, madisound, etc) offer the crossover circuitry and
controls (bass eq, phase reversal, auto on/off, low pass crossover, level control, etc) that is commonly found on sub plate amps, as a stand alone circuit to be used with whatever high powered amp the customer happens to have on hand? I realize you can use a Behringer crossover, but then you get a lot of box and circuits and op amps that you may never use or even want. Or you can spend 500 dollars at Marchand for something that is a little higher cost and quality than you feel you need (ok, than I feel I need).
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Old 19th January 2006, 05:24 PM   #2
sreten is offline sreten  United Kingdom
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Location: Brighton UK
http://www.bkelec.com/Modules/asbf.htm

/sreten.
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Old 29th January 2006, 08:42 PM   #3
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"bump" just sounds so rude. I spent a few minutes and came up with six separate rolling-tumbleweed gifs to stick in here but reconsidered. I don't see too much animation on this board so I didn't want to compound rudeness with abuse of bandwidth.
Anyway, I hope you get the point. Is this not a reasonable question?
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Old 30th January 2006, 09:23 PM   #4
herm is offline herm  United States
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Join Date: Mar 2002
Location: Pasadena, CA USA
I typed Linkwitz transform into google, and here are the
first couple of results:

http://sound.westhost.com/linkwitz-transform.htm

http://www.trueaudio.com/st_lkxfm.htm

http://www.pvconsultants.com/audio/eq/linktran.htm

Here is Elliots PCB:

http://sound.westhost.com/project71.htm
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Old 31st January 2006, 01:13 AM   #5
pjpoes is offline pjpoes  United States
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if you are asking about the disadvantages, they do exist. First, look at what it takes to impliment it on Rythmics sight. Notice that, if you dont use their woofer, you have to calculate certain values. Notice on Elliots sight, and is thoughts compared with other versions of the circuit which are more easily implimented. Not that its really hard, but it requires some calculations for each speaker.

Then you have the issue of its effect on the systems efficiency, and maximum output. Basically, it extends the response of the woofer, at the expense of efficiency. A lot of power is wasted basically to allow that lower output, and the cone is forced to move more that it may have been designed for. Generally woofers best suited to this have very long excursion. I found, atleast with modeling them, that using it with many woofers would cause it to reach maximum excursion at pretty low levels.

One sub I actually made was the TB 8" woofer with I believe 12mm of xmax. Not bad I think, definatly in the longer excursion range, maybe no 25 or 32, but still pretty good. Using a LT with this woofer caused it to reach maximum excursion at about 89 decibles max output. Without, it would reach more like 95-96 decibles. It a ported box, it had similar response, and even more output.
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