Can a 8ohm driver be mated with 4ohm tweeter? - diyAudio
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Old 1st October 2007, 02:40 PM   #1
Nordic is offline Nordic  South Africa
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Default Can a 8ohm driver be mated with 4ohm tweeter?

Well as the thread title asks... Can a 8ohm driver be mated with 4ohm tweeter?

Do I need to take any precautions?
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Old 1st October 2007, 02:56 PM   #2
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no problem!
A sensible crossover would be needed anyway.
Regards
Jürgen
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Old 1st October 2007, 04:40 PM   #3
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Default a little more detail please?

I was just thinking about this very thing.

For example: if I've got an 8ohm woofer, 4ohm tweeter, x-over at 3000 Hz, 2nd order Butterworth I get --

Ct = 9.38 uF
Lt = 0.3 mH
Cw = 4.69 uF
Lw = 0.6 mH

will that take care of it, or do I need a 4ohm resistor in series with the tweeter in addition to any L-pad?

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Old 1st October 2007, 05:25 PM   #4
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It's important to match sound levels.
dB-SPL is a good start.
Speaker impedence is not really 4 or 8 ohms.
That's just a guideline.
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Old 1st October 2007, 08:29 PM   #5
tinitus is offline tinitus  Europe
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Make your xo accessable so it will be easy to try different values and make other changes ... components joints should only be solder fore the same reason
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Old 1st October 2007, 08:36 PM   #6
Nordic is offline Nordic  South Africa
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Assuming the tweeters are alot more efficient... say tweeters are 94db/w and the driver 86db.

The current mix of driver and tweeter I have is a nice step up fro mthe sound of the original driver that was in there...
Yep, I committed the sacriledge of replaceing the drivers with similar speced ones, with no other changes... and this once, it worked out...

Now I have 20 of the Peerles groupbuy tweeters and would be interested in implementing the next step up, as the tweeters currently in use are getting very old now...

I would not be opposed to even building a box and crossover from scratch if someone would be willing to look at the datasheets for the driver and tweeter and make an educated guess as to suitable crossover components and box dimensions. I'm not averse to something slightly larger than average, and have a good supply of the relatively low cost driver... (BTW, these sound VERY good after some running in, very convinceing, crisp low bass.)I would not have been able to guess that from the impendance graph.

At least as you can see it is a very easy to drive woofer, if not supper efficient.

Maybe a multiple woofer design? I guess the only way to beat that impendance peak is a 3 way... or is there some kind of notch filter one could use to flatten it out?

http://www.tvm-valmez.cz/index.php?i...102&l=2&catg=1

http://www.tymphany.com/datasheet/pd...C25SC15-04.pdf

http://www.speakercity.com/Merchant2...ry_Code=VifaCL
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Old 1st October 2007, 10:03 PM   #7
00600 is offline 00600  United States
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I'd say 4Khz-6Khz.

Or take advantage of the woofer's peak @3.5Khz and crossover there, Due to the Fletcher-Munson curves it should sound pretty flat.
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Old 2nd October 2007, 06:20 AM   #8
Svante is offline Svante  Sweden
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Quote:
Originally posted by 00600
I'd say 4Khz-6Khz.

Or take advantage of the woofer's peak @3.5Khz and crossover there, Due to the Fletcher-Munson curves it should sound pretty flat.
I disagree, I'd put the crossover frequency at 2-3 kHz. The peak at 3.5 kHz should be avoided as far as possible, since it is almost certainly associated with increased distortion, and the directivity there is probably also high.

The drivers have sort of a small overlap; the tweeter has fs at ~1,5 kHz and the woofer should not be used above 3 kHz. This is a pity, and calls for steep filters. This in turn is not easy to accomplish with passive filters.

Fletcher-Munson curves are not relevant here.

The 4 ohm impedance is not a problem, a series resistance will be needed anyway to reduce the sensitivity of the tweeter.
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Old 2nd October 2007, 09:48 AM   #9
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Quote:
Originally posted by Nordic
[B]Assuming the tweeters are alot more efficient... say tweeters are 94db/w and the driver 86db.
Actually the tweeter is 91db/w/m and the woofer is 86db/w/m. That's because the sensitivity is listen at 2.82V which effectively gives 2W into 4Ohm. Always assume the woofer looses around 0.5 db in a box.

So you need to dampen the tweeter 5.5 db, that's gives a 3.9Ohm series resistance. Placed between the filter and the tweeter you effectively have an 8Ohm tweeter. Problem solved (actually two problems solved ).
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Old 2nd October 2007, 11:05 AM   #10
Nordic is offline Nordic  South Africa
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Schweet guys!

Do you think useing 2 drivers would make the SPL gap smaller?

I have seen a number of 3way designs around this woofer, useing it as the larger driver... but I don't want to go this route yet.....
one example... 2 4ohm version of the driver used in series.

Click the image to open in full size.

Here is a 2-way design I saw, any comments on this one as a suitable crossover to mate my 2 components, would be welcomed, big time. One problem I see is the 8ohm tweeter.

Click the image to open in full size.

There was no cabinet suggestion I could find.... my knowledge of eastern european languages is shockingly little...

I did see one cabinet which seems to fall in my skills and tools category, 1200x300x340 mm

Click the image to open in full size.
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