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Old 1st April 2009, 03:28 PM   #11
GM is offline GM  United States
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Greets!

You're welcome!

Right, and now that you have a grasp of series resistance and since this is a 'FR' driver app, what you'll probably need to tonally balance the driver over the widest practical BW is some form of baffle step compensation filter (BSC): http://www.quarter-wave.com/General/..._Articles.html

GM
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Old 1st April 2009, 04:09 PM   #12
IG81 is offline IG81  Canada
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Quote:
Originally posted by GM
Greets!

You're welcome!

Right, and now that you have a grasp of series resistance and since this is a 'FR' driver app, what you'll probably need to tonally balance the driver over the widest practical BW is some form of baffle step compensation filter (BSC): http://www.quarter-wave.com/General/..._Articles.html

GM

I might consider BSC, but since I almost always use graphic equalizers **dodges rocks** and the speakers may move from room to room or to other houses, I might leave it alone.
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Old 1st April 2009, 04:22 PM   #13
GM is offline GM  United States
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Just so long as it's not a cheap, low res, noisy one......... I switched to them in the early '80s when dbx came out with one that was ~transparent in a ~112 dB efficient (in-room) horn system.

GM
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Old 2nd April 2009, 01:45 PM   #14
IG81 is offline IG81  Canada
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Hi GM,

Thanks again for all the info. I'm now all done measuring my driver's parameters.

I finished last night by building a 5.25" I.D. cubic box to measure Vas. To find the volume of air trapped by the driver alone, I filled my driver's cone with rice and found the volume in ml with a measuring cup. I concluded that was the most accurate method I could easily use, what with the cone having a curved taper, whizzer cone...

Except for Qes, and incidentally Qts, which were 0.86 and 0.71 on manufacturer's sheets, all T/S parameters ended up being very close.

Fs = 70Hz
Re = 6.8ohm
Qms = 4.04
Qes = 0.49
Qts = 0.44
Vas = 8.72
n0 = 0.60%
SPL = 89.8dB

Thanks for the n0 and SPL formulas, they are not something I ever came accross searching the web and forums. I'll be hanging on to all that valuable info. This is my first speaker project, but probably won't be the last!

Cheers!
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Old 2nd April 2009, 07:07 PM   #15
GM is offline GM  United States
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Greets!

You're welcome!

Thanks for sharing, can't have too many measured specs, especially of 'as built' designs (hint, hint).

GM

(PS: I use sugar as it helps to 'sweeten' the sound. Do it on a Deep South summer day and it gets downright 'syrupy'. )
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Old 2nd April 2009, 08:07 PM   #16
IG81 is offline IG81  Canada
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Quote:
(PS: I use sugar as it helps to 'sweeten' the sound. Do it on a Deep South summer day and it gets downright 'syrupy'. ) [/B]
Hehe...

Rice isn't the best at taking a consistent ammount of space and at packing in a predictable manner, but it looks like it did close enough.

I'm reconsidering the BSC circuit, having just remembered of Rod Elliott's (ESP) design for line level, adjustable, passive (or active) BSC circuit. It will do away with the gripe I had with a fixed correction level and give me a good excuse to get one of these nice little Hammond aluminium project enclosures!

Oh, and 4.7ohm will do just fine to get my Qts up ~0.69 and still give me ~87.5dB @1m @1W.
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