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-   -   TB W4-657SB Measures (http://www.diyaudio.com/forums/full-range/69637-tb-w4-657sb-measures.html)

DDF 13th December 2005 12:54 AM

TB W4-657SB Measures
 
Thought this might be of interest.

Fired up MLSSA yesterday and took some frequency response measures of the TB W4-675SB. Baffle was 6.5"x10", 0.5" roundovers, and woofer center was 3.5" up from baffle bottom.

Due to the rectangular FFT window used, response is good down to about 250 Hz.

To compensate for its primary break up mode, I'd go with a 5 dB notch centered at 7 kHz. Any more and you'll have no high end, any less and you'll still keep that aggressive sound. I'll measure impedance tonight and come up with something.

You really need to be right on axis with this, even 15 degrees off and it drops like a stone above 8 kHz.

It's also plagued by a 5 dB hole an octave wide, centered on 4kHz. As a result, intelligibility with dialog suffers.

Hoped to be able to use this full range but plan is to cross at about 3 kHz to an Aura NSW2. Woofer will have 8 kHz notch + one inductor. Aura will probably be low Q second order, but we'll see what the measures say.

Not shown is low end response; its 3.3L sealed for fb=99Hz and Q = 0.61. It'll be high passed with a second order active, Q=0.9. Will give a nice cross at 100Hz to a 4th order low pass on a sub. Its xmax in this config gives an honest 105dB.

Graph of
response:
http://www3.sympatico.ca/dalfarra/W4657SB.gif

Excel file of responses:
http://www3.sympatico.ca/dalfarra/W4657.xls

DDF

DDF 13th December 2005 05:29 AM

Took the impedance tonight at 3 drive levels (small, med and large signal, all within the published xmax). Results graphically at:
http://www3.sympatico.ca/dalfarra/W4657SBZ.gif

and the excel file's been updated with the impedance data, at the link posted earlier.

Itís pretty apparent that this is a fairly basic motor. Large inductance, no copper. As input power increases, so does inductance. This isn't too big an issue as a load for a trap cct, but it betrays that the distortion in the high end will be a bit heavier than average due to inductance modulation. Given that the inductance modulation is minimal below 3 kHz, thatís where the first stab at the crossover will be. The damping at resonance also shifts, even with moderate input power. This means the suspension is either non linear or the published xmax is hugely optimistic. Finally, an impedance anomaly tracks the break up at 6.8kHz.

One nice outcome was that fs was within 1% of Unibox's prediction. The prediction assumed "heavy stuffing" (which it was) meaning that Unibox looks to assume a realistic Ql for stuffing.

DDF

jarrettl 27th March 2006 07:12 PM

I was wondering if anyone else had any comments on these drivers. I just purchased a pair and was hoping to use them in an open baffle setup crossed over at about 90hz to an accompanying subwoofer.

Tenson 27th March 2006 07:45 PM

Nice work! But my main reason for posting... what is that motorbike? :D

DDF 27th March 2006 10:58 PM

Crossed mine over to a sub last night at 90 Hz. Mated really well listening to the Cream live DVD. Note: high end isn't that clean but its very good for dialog and typical DVD fair.

BTW, the bike is the world's fastest chainsaw. I'm guessing Huskevarnas. :)

leadbelly 27th March 2006 11:10 PM

Quote:

Originally posted by DDF
BTW, the bike is the world's fastest chainsaw. I'm guessing Huskevarnas. :)
Really? How fast is the 0-60 board/feet? :D

DDF 27th March 2006 11:22 PM

LOL! You could always measure the speed in knots... :)

phoneisbusy 1st April 2006 08:39 AM

I have a pair of 657s and 871s from a swap meet that I never got around to using. Thanks DDF for the measurements! :D

I'm thinking of using the w4-657 and w3-871 in a 2-way with the 871 crossed over around 700 hz. I'm leaning this way for a few reasons:

First project after reading up on speaker building for the past months.

700 hz appears to be the approx. range where bsc needs to be applied. Hopefully, I can avoid the bsc and just pad down the 871s?

I'm trying to avoid too many components in the crossover (i.e. trying to stay away from the 8khz breakup and the 4khz dip.

Need to use these drivers up before I can justify purchasing more.

If I get ambitious, I might try the drivers in a transmission line.
I\'m hoping that these drivers will work well as rear surround speakers.

Thanks again for the measurements and comments.

regards

Dave

tcpip 31st May 2006 12:49 PM

Very interesting
 
I was thinking of using these drivers in a 3-way like you have. My comments were posted here. I now guess that these drivers don't deserve too much money spent on good accompanying components... I'll try to get an inexpensive tweeter and woofer to tie up with these things.

Your box dimensions too are useful.... I can use them ready-made for my purpose. Do you have the T/S parameters handy, specially the Vas?

DDF 1st June 2006 01:22 AM

Hi,
TS Params for my two drivers here:
http://www3.sympatico.ca/dalfarra/W4657TS.xls

They tend to get gritty up top. I plan to cross them to D26NCs. Very linear tweeter, should be nice, and it has a small faceplate so it should make for a really nice and smooth off axis response.

Low frequency end depends on what you want to do with it. The real sweet spot for these drivers is in a small box against wall delivering good bass up to 105 dB. If you want to use as a mid for a big room system, don't spend too much money on the woofer, the mids aren't worth it in that application. Sensitivity is about 85 dB SPL without BDC, so go with a moderately low sensitivity woofer.

I'd look at woofers with a 2 pi sensitivity of 85 dB. Dayton/Silver flute maybe, cross em about 300 Hz in a manner to minimize floor contribution.

Dave


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