MTM project using 7" vifa drivers

[audio_moksha]

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.

[Inductor]

(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)

[Thawach]

moksha if u choose sealed box to build. Please you build two sealed boxs. if the vent box u can build like madisound link.

[audio_moksha]

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.

[sreten]

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.

[audio_moksha]

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.

[sreten]

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 :

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.

[Andy G]

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.

[Inductor]

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

[audio_moksha]

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:

Looking at the stereophile article the treble electrical filter is ~

I do have a test jig setup for speaker workshop. Many thanks once again.

[sreten]

Originally posted by audio_moksha

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?

Hi,

I estimate the electrical high pass to be ~ 4Khz, but could be wrong.
Acoustically the crossover point is 2KHz see fig 3.

/sreten.

[audio_moksha]

any specific suggestions sreten? I was thinking of starting off somwhwere with a low order butterworth for the tweets and maybe a LR for the midrange. However if the tweeter is phase inverted shouldn't the crossover be a 4th orfer L-R? Once again thans for all your expertise and suggestions.

[Inductor]

Vifa midrange is a MG25 7"

Was there an "Vifa MG25 Yellow Glass Fiber cone"? I didn't find it... for the specs.

[sreten]

Originally posted by audio_moksha
any specific suggestions sreten? I was thinking of starting off somwhwere with a low order butterworth for the tweets and maybe a LR for the midrange. However if the tweeter is phase inverted shouldn't the crossover be a 4th orfer L-R? Once again thans for all your expertise and suggestions.

Hi,

For the low pass your first issue is baffle step compensation.

A symmetric driver aligned 4th order L/R acoustic response has
the two drivers connected in phase, 2nd order L/R out of phase.

Checkout Zaph's crossovers here : http://www.zaphaudio.com/

Note that most of the crossovers are slightly assymetric to make
up the phase difference betwwen the drivers, except the ZD5
which has a treble delay ladder, they are all acoustic targets.
Specifying an electrical target is fairly meaningless.

Also note the lipinski does not have symmetrical acoustic slopes
at all, but nevertheless seems to work very well in practise.

If you can get your head round SW then the following should not be too bad :

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

/sreten.

[Inductor]

...or is it a 2xVIFA MG18WK/SK09-08 8ohms connected in parallel(?!)
http://www.tymphany.com/archives/10

Another Xreference
http://www.shine7.com/audio/speaker.htm

[rob3262]

Originally posted by sreten

Specifying an electrical target is fairly meaningless.

/sreten.

Sreten, could you please expand on this?

I don't have a fundamental understanding of accoustic vs electrical orders.
Thanks
- Rob

[sreten]

Originally posted by rob3262


Sreten, could you please expand on this?

I don't have a fundamental understanding of accoustic vs electrical orders.
Thanks
- Rob

Specifying an electrical target is fairly meaningless.
/sreten.


Hi,

for an example see http://www.zaphaudio.com/audio-speaker16.html

The acoustic target is 4th order L/R at 1.7khz.

The actual crossover is 2nd order electrical combined with the drivers
responses in box - this response includes baffle step and there is
no compensation of driver inductances or the tweeters impedance
peak at its Fs as this is not necessary. (as its a ferrofluid model).
(not the case for the XT25 see http://www.zaphaudio.com/ZD5.html )

The components in the crossover do not conform to any electrical
filter (e.g. Bessel, L/R, Butterworth etc), what counts is the total
acoustic result taking all factors into consideration.

See all of Zaph's other designs where this principle is applied.

/sreten.

[audio_moksha]

...or is it a 2xVIFA MG18WK/SK09-08 8ohms connected in parallel(?!)

Yes this is the driver I had in mind; seems like what Lipinski uses.And sreten, thanks so much for all the information.

[Inductor]

Originally posted by audio_moksha

Yes this is the driver I had in mind; seems like what Lipinski uses.And sreten, thanks so much for all the information.

I hope you can find it because it was discontinued.

http://www.tymphany.com/mg18sk09-08

[Inductor]

You have here a good base to work on...

[Inductor]

and Parts List.

note: try to get resistors for R2 on the attenuation circuit of 20/25W for each 100W of Amplifier power with speaker power (XT25TG) ~55W.

[audio_moksha]

Thanks for all this Inductor! Where did you get these plans from? Looks like something I would like to implement especially since I will be biwiring. I got the Vifa midrange drivers from a friend who had 4 extras. Also I suspect that the XT25 will need impedance compensation as sreten suggested.

[Inductor]

Originally posted by audio_moksha
Thanks for all this Inductor! Where did you get these plans from? Looks like something I would like to implement especially since I will be biwiring. I got the Vifa midrange drivers from a friend who had 4 extras. Also I suspect that the XT25 will need impedance compensation as sreten suggested.

"As is". You are free to experiment... I don't think it will need one. Why do you suspect? You can always change it if you don't like. It's also padded by the L-pad.

Accoustic xover ~2K0.

[sreten]

Originally posted by audio_moksha
Thanks for all this Inductor! Where did you get these plans from? Looks like something I would like to implement especially since I will be biwiring. I got the Vifa midrange drivers from a friend who had 4 extras. Also I suspect that the XT25 will need impedance compensation as sreten suggested.

Hi,

Impedance compensation would more of an issue if the c/o had
significant attenuation (therefore high source impedance), as it
is attenuation is minimal and the impedance peak is "buffered"
somwhat by the 15R resistor.

see ZD5, for accurate low Q slopes the tweeter needs a LCR.

Inductor's c/o values seem to be in the right ballpark but
it would be interesting to know how they are derived.

The bass mid driver wiggle at 1kHz would be an issue for me,
as would the amount of baffle step compensation, the tweeter
level indicates to me not enough BSC.

/sreten.

[Inductor]

Originally posted by sreten

... as would the amount of baffle step compensation, the tweeter
level indicates to me not enough BSC.

Check again with two speakers (2xMG18). You can adjust on the compensantion/attenuation circuit of the tweeter if you don't like the desired computed attenuation (~3dB).

audio_moksha, take special care on the inductor L1, at full operational use you should get a double power inductor for the pair of two speakers, or double the diametre of cable in it (inductor). Also choose a low loss or internal resistence inductor like the Tritecs Ferrobars or similar.