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Old 6th April 2008, 02:53 AM   #1
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Default MTM project using 7" vifa drivers

I would like to build a pair of sealed box MTM D'Appolito style speakers using 7" vifa woofers and tweeters much like th Lipinski studio monitors. Do I need to section off each section of drivers or do I simply mount them in one sealed box? This idea is still brewing so any suggestions are welcome. Also where can I find more information about the D'Appolito configuration? Thanks in advance.
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Old 7th April 2008, 12:48 AM   #2
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(I don't know for short, but) You can read D'Appolito white papers (Google it) on the net.
Do you have this document yet?

Lipinski studio monitors - Stereophile L-707 Review
http://lipinskisound.com/Reviews/Ste...7%20Review.pdf

Also look for Solist MTM Kit using Scan-speak drivers from Madisound,
http://www.madisound.com/solist.html

and Westlakes pro Westlake Audio BBSM-5F with dual 5".
http://images.google.com/images?hl=e...-8&sa=N&tab=wi

(http://www.westlakeaudio.com/Speakers/speakers.html)
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Old 7th April 2008, 02:44 AM   #3
Thawach is offline Thawach  Thailand
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moksha if u choose sealed box to build. Please you build two sealed boxs. if the vent box u can build like madisound link.
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Old 7th April 2008, 03:04 AM   #4
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thanks for the responses. Do you folks know what material Lipinski used for the tweeter surrounds? The website states that its Belgian foam. I know its for reducing the edge effect so would acoustical and/or non-acoustical foam work?

So far I have the 7" Vifa woofers and the Vifa 25mm xt tweeters. I'ts going to be sealed boxed with a first or second order butterworth with inductance compensation.
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Old 7th April 2008, 10:12 AM   #5
sreten is offline sreten  United Kingdom
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Quote:
Originally posted by audio_moksha
I'ts going to be sealed boxed with a first or second order butterworth with inductance compensation.

Hi,

That will turn out completely wrong.

You could do a lot worse that following the schema here :

http://www.zaphaudio.com/audio-speaker16.html

http://www.rjbaudio.com/Audiofiles/FRDtools.html
http://www.geocities.com/woove99/Spkrbldg/

/sreten.
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Old 7th April 2008, 06:46 PM   #6
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sreten, could you explain why you think that the sealed box low order butterworth combination is a bad idea? It seems like the Lipinski monitors implement something like that.
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Old 8th April 2008, 11:04 AM   #7
sreten is offline sreten  United Kingdom
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Hi,

Lowish order acoustic alignments are not the same as low order
electrical filters. You likely would exploit the bass drivers inductance
for baffle step compensation.

Looking at the stereophile article the treble electrical filter is ~
at 4 or 5KHz for a low order alignment and the bass filter
due to baffle step will far lower than 2KHz due to BSC.
The net result is lowish order acoustic, with the bass mid reinforcing
the treble above the c/o point (2Khz) to a degree, you can only
arrive at this by measured and / or good simulation.

With low order acoustic slopes tweeter excursion is an issue,
one that the XT25 is not particularly good at, quoting Zaph :


Quote:
Vifa XT25 ($54) - Smoothest and most extended response curve in
the group, and resulting CSD is excellent. Good tall order HD above
2kHx, but average 2nd order HD. Poor HD levels of all types below
2kHz, even considering the extended low end. It may have a 500 Hz
Fs, but don't think about crossing it below 2kHz LR4 or 2.5kHz LR2.
noting these are acoustic slopes.

/sreten.
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Old 8th April 2008, 12:26 PM   #8
Andy G is offline Andy G  Australia
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Do not use the XT25 with a low order crossover unless above say 4500Hz. !!

For the tweeter in a 7" MTM you need a Seas 27TDFC or something similar with plenty of grunt.

Which 7" Vifa woofer are you considering? If you are considering the P17WJ sealed and asking it to do bass and mids you will seriously muddy its mids and you would really need to make the tweeter do a LOT of the upper mid work.

I would not recommend this approach.
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Old 8th April 2008, 02:31 PM   #9
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Default Reference

Quote:
Originally posted by audio_moksha

So far I have the 7" Vifa woofers and the Vifa 25mm xt tweeters.

PE "Nebula" with:
Vifa XT25TG30-04 Ring Radiator Tweeter
Vifa PL18WO-09-08 7" Woofer
http://www.partsexpress.com/projects...la/nebula.html
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Old 8th April 2008, 02:51 PM   #10
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thanks for the input folks. The Vifa midrange is a MG25 7" glass fiber woofer and the tweeter is the XT25. My goal was to clone the lipinski monitors with the time aligned stepped baffle (I figure by aligning the acousitical centers). I was thinking about using some material like whispermat for the stepped tweeter baffle.

So sreten, you say that the Lipinskis are electronically crossed at 4k? I read the article and it said somewhere that it was crossed at 2k? I could be wrong. Anyway my goal as I said earlier was to clone the lipinskis so some low order crossover is in order. steten how would you reccomend I do the crossover?

Once I get the drivers I will test the actual impedance in free air as well as in the cabinet using speaker workshop. I'm also having the tweeter baffle adjustible so that I can adjust for best phase response. The lipinskis also have the tweeter out of phase which leads me to suspect that it uses a 2nd order L-R crossover.

Also streten, and others any suggestions for achieving this:
Quote:
Looking at the stereophile article the treble electrical filter is ~
I do have a test jig setup for speaker workshop. Many thanks once again.
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