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Old 7th January 2004, 04:18 PM   #1
gjeff80 is offline gjeff80  United States
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Default Determining T/S Specs

Hi everyone, I was wondering if anyone could help me out here. I have some old Cervin Vega 189E woofers, and I've had them reconed, so even if I could get the original specs, they would probably be different now. I was wondering if anyone has any tips on measuring the T/S specs of the woofer. I first tried using speaker workshop, I made the impedence jig, but couldn't get it to work correctly, plus I think I needed to us an amplifier to drive the jig and couldn't find good directions on how to do that.

So then I found a couple of sites that tell you how to manually measure them, I did everything correctly, and did the measurements both methods, but they didn't come up the same.

( http://sound.westhost.com/tsp.htm , http://www.epanorama.net/documents/a...arameters.html , and http://www.diysubwoofers.org/measure.htm )
Here are the results using method 1, and method 2.

Method 1 Method 2
Voice Coil Re 4.76
Fs 38.23
Qms 8.5 7.28
Qes 1.4 1.29
Qts 1.21 1.09

Are those close enough to each other to be accurate? I was just expecting to get the same value using the two different methods. But anyways, the only value left to find is the VAS, which seems like it might be a little difficult, does anyone have any tips on figuring out this value? The only empty un insulated enclosure i have right now is the chamber of an 18 inch W-bin, would this work if I know the volume of the chamber? But the instructions say to mount the speaker reverse so the speaker is facing ino the enclosure, plus it says "use a good solid enclosure of known volume that's about a cube of the nominal speaker size"

What exactly does that mean, what would be the nominal size of an 18 inch woofer??

Thanks in advance!

Glenn
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Old 7th January 2004, 07:49 PM   #2
OMNIFEX is offline OMNIFEX  Jamaica
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The Cerwin Vega will work in your W Bin.

As a matter of fact, Cerwin Vega's 18's, were designed
around the folded horn concept.

Despite what Cerwin Vega says, reconers stock only
two versions, the 300 watt, and, 500 watt.

The 189 Woofer, is ruffly around 20 years old!

The VAS is 244 - 280 liters. Pending if its a JE or SC
Why don't you ask the reconer the TS Specs??


This is how the speaker is mounted......

Click the image to open in full size.
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Old 7th January 2004, 09:31 PM   #3
claudio is offline claudio  Italy
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Default SW

Hi Glen,
about SW you don't need an amplifier to measure T/S parameters, if your sound card is able to output 1 V, as most do. T/S parameters are for small signal. If you want to keep trying with SW, check my HP, there's a complete tutorial.

regards

Claudio
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Old 8th January 2004, 12:31 AM   #4
gjeff80 is offline gjeff80  United States
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claudio, thanks for the info on SW, my only concern was that it says you need to mount the speaker with clamps or something because it will move. Do you use the line up of your sound card? I'm using a Sound Blaster AWE 32, and it has a line out and a speaker out on it. But when I tried using the Speaker out, software wouldn't calibrate the speaker jig. I'll check out your homepage to see if I can figure it out any better.

Omnifex,

Thanks for the illustration, that is cool, where did you get that from? The label on the back of the 189 just says Model: 189 E. I know it's an old woofer, and probably not the best one around, but I have them sitting here, and instead of buying new ones, I might as well use them and if the blow up I'll try finding something else.

Thanks
Glenn
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Old 8th January 2004, 02:50 AM   #5
OMNIFEX is offline OMNIFEX  Jamaica
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Actually, using those Vega's in the W Bin would be a very wise choice!

There aren't many manufacters that design 18's to work
in a horn loaded enclosure today. Everything is Bass Reflex or Sealed Designs.

The 189 E is perfect for a W Bin, J Bin, or e bin.

If you ever get the oppertunity, look into Precision Devices
PD 1850. An exceptional driver designed for Folded Horns.


Oh,

The illustration came from google's image search.
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Old 8th January 2004, 01:41 PM   #6
claudio is offline claudio  Italy
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Glen,
using the Line Out should be fine, if you are able to get the 15-18k reading in the SW Vumeter. I remember there was an issue with the SB 16-64 (and therefore 32 too) about using 48 k Sample Rate: just use 44K and it will bw ok.
About the clamp, check my site, there are pics and explanation: the driver has to be firm and without close reflecting surfaces.

Regards

Claudio
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Old 8th January 2004, 04:00 PM   #7
gjeff80 is offline gjeff80  United States
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Thanks, I thought you would need to clamp the woofer if you were using a external amplifier to drive the load, because I can't see the lineout of the sound card being able to move the cone that much. I was thinking of mounting the woofer no two plastic saw horses I have, this would give the woofer a good place to mount, and wouldn't have anything around it to interfere.

Glenn
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Old 9th January 2004, 12:41 AM   #8
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If a sound card can output around 1v it would certainly be an easy solution for measuring TS params. Your computer would become the freq generator, too.

Is there any downside to using a sound card?

My preamp can output up to 25v so I was going to use that driven by a cd player with disc full of sine waves :-)

Mos
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Old 9th January 2004, 03:39 AM   #9
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Quote:
Is there any downside to using a sound card?
unknown frequency response.

Perhaps in hidden places in the net it displays the specs of them

Cheers!
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Old 9th January 2004, 06:54 AM   #10
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Quote:
Originally posted by mikee12345


unknown frequency response.

Perhaps in hidden places in the net it displays the specs of them

Cheers!
Ahhh just download rmaa and test your sound card (not that it should matter though as SW feeds back in one channel as a reference)......

http://audio.rightmark.org/

Tony.
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