Vifa TC11MG MTM design trouble - diyAudio
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Old 2nd February 2005, 03:13 PM   #1
eddog is offline eddog  United States
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Default Vifa TC11MG MTM design trouble

I recently finished my first speaker project using two of the vifa TC11MG's in series with an older 1 inch dome tweet from radio shack that I had laying around MTM arrangement (cheap was the keyword). The crossover was designed as a LR 2nd order at 3500. Well it sounded so good (6.5 liter box ported at 95hz) that instead of using them as boombox speakers I used them as front L/R of my home stereo(with passive Klipsch sub xo at 145Hz). They sounded great until the radio shack tweets started to show their past abuses from being used in a very crude pickup stereo setup.
I would appreciate anyone's opinions about a good replacement tweet around or less than 20 bucks a piece that you think would work well with those vifa drivers. If it means changing crossover parameters I am willing to do that also. This speaker building has become addictive, my wife thinks I'm nuts, but I can hear some honking in the tweeter response and I must deal with it or it will drive me nuts.
The old tweets were rated at 8 ohms.

I now see the value of building a well designed kit before under taking a design of my own
I will be using tried and true designs for the next project.
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Old 2nd February 2005, 03:52 PM   #2
GM is offline GM  United States
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At a glance, and not knowing anything about the one it will replace: http://www.partsexpress.com/pe/pshow...=264-524&DID=7

GM
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Old 4th February 2005, 01:32 PM   #3
eddog is offline eddog  United States
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Thanks GM, I see that that tweeter is rated as 6 ohms where the Radio shack tweet was 8 ohms. Can you explain what will happen to the crossover point(currently designed for 3500Hz @8 ohm load) if I add that tweeter without changing component values in the x-over. Aslo if I have two drivers spl( @88db/1w) in series does that mean I now have a spl of 91db/1w. So a tweeter rated at 91db wouldn't need to be padded?
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Old 4th February 2005, 03:51 PM   #4
GM is offline GM  United States
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You're welcome!

I imagine it will shift the XO point/slope enough to be audible, so a new HF XO design may be required.

It's easier for me to consider multiple driver pairings, level matching, etc., issues from a voltage POV, so using a calc'd eff. from some measured specs:

88.76dB/W = V = SQRT (1*8) = 88.76dB/~2.83V, but these are nominally 4 ohms, so 10*log10(8/4) = ~3.01 + 88.76 = ~91.77dB/~2.83V, then two in series would = +3dB for doubling of acoustic pressure and 10*log10(8/8) = 0dB for a net ~91.77dB/2.83V.

Since the tweeter is rated 93.5dB/2.83V, it will need padding.

GM
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Old 4th February 2005, 04:08 PM   #5
eddog is offline eddog  United States
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I knew I should have paid closer attention in Trig/Calc class! I'm with you until the logrithmic function. I better dig out the old books because I want to know the reasons behind the calculations. Thanks again, I am really enjoying this learning process!
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