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Old 25th January 2004, 03:21 PM   #1
k98luka is offline k98luka  Sweden
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Question speaker design and evaluation equipment - what are my basic needs?

first time on the forum. Looks great. i have done a number of DIY projects, but I have never made any measurements on my speakers, in other ways then to listen to them.

I am looking for equipment in order to design and evaluate the performance of my DIY projects. So far I've reckoned that I probably need three things to start off with:

1: Software (e.g lspCAD)
2: something called a JIG.
3: A microphone.

My question is where I can get hold of these gadgets or how to build them? Or if it is anything else that I have forgotten for some basic construction/evaluation work?

Any suggestions or advice would be of great help.

regards, karl
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Old 25th January 2004, 08:54 PM   #2
claudio is offline claudio  Italy
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Hi Karl,
first let me say that you should have put this thread in the loudspeaker forum.

About testing, check my page where is described a tutorial on how to use Speaker Workshop, a freeware software to measure speakers.

Remember that for impedance measurement you don't need a mic, while for acoustic measure you need it; listening to you project is very important too, don't think that measures alone are the best thing to do: both helps each other to get your gol.

Regards

Claudio
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Old 26th January 2004, 11:23 AM   #3
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Old 27th January 2004, 09:00 AM   #4
k98luka is offline k98luka  Sweden
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Talking Reply to Claudio:

Thank you very much Claudio, this was great help !

I still have one question though:

if I want to build my own mic-preamp, can i go for the one proposed by eric wallin as below:

__________________________________________________ ____
The jig is designed to plug a preamplified mic into. You could
probably just use a 3V to 9V supply (2 AA bats or a 9V bat)
along with a capacitor and resistor in order to power the
Panasonic mic cartridge. They are very cheap from Digikey (<$3
in single quantities). Engaging ASCII-CAD:

power switch
/
+-----o o-----+
| |
(+) 5k
3Vbatt |
(-) +------- 10uF -------(+)
| |
| (+)
| Panasonic cartridge To mic input on jig
| (-)
| |
+-------------+--------------------(gnd)


_________________________________________________

Do i need a polyprop capacitor or is it OK with cheaper ones?
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Old 27th January 2004, 10:24 AM   #5
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I doubt you would get enough usable level from such a simple mic powering scheme. I built up the Wallin preamp1 and it works fine - the extra gain is neccessary if doing far field measurements.

Cheers
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Old 27th January 2004, 02:18 PM   #6
claudio is offline claudio  Italy
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Karl, I am glad it helped you!
About the mic-pre, I have no experience with Eric's pre; check the SW forum to have more infos, or follow Centauri advise. However remember that if you are going to use a balanced mic, like the ECM8000 I suggest, you will need a balanced pre.

Claudio
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Old 27th January 2004, 08:27 PM   #7
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Default measurements don't replace listening...

Quote:
Originally posted by claudio
...listening to you project is very important too, don't think that measures alone are the best thing to do: both helps each other to get your gol....
Definately, I've spent a lot of time designing and building custom drivers from scratch. One time I damped and tweaked a driver until the response was nearly perfectly flat ( +/- about .5 db from below 100 Hz to over 1 Khz) and we were excited to bring it from the lab over to our home theater test room to give it a listen. It sounded like crap, hardly better than your average 1.5 watt K-mart special 1/4" wall particle board non-removeable grill junk speaker.
I'm sure if they didn't take hours to build each driver, and we printed out the freq. respons charts people would have bought them anyway and convinced themselves that they sound good. It's amazing how bias can overpower your ears...
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Old 30th January 2004, 01:23 PM   #8
Shaun is offline Shaun  South Africa
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I've built both Jason Neal's mic preamp (with Panasonic WM60A) and the Wallin jig. I also started out with Speaker Workshop. This is probably the cheapest speaker design setup you can find in the Universe.

I highly recommend building the preamp, it's not too difficult.

Good luck
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