My "Defender SPK-720 Upgrade" project. - diyAudio
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Old 1st April 2009, 07:29 AM   #1
Stream is offline Stream  Russian Federation
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Default My "Defender SPK-720 Upgrade" project.

Hello. Here is project-log about my speakers. I'm woring on them when I have some ree time, so I'm planning to finish it before Summer

In 2005th I have bought a pair of Defender Mercury 50A active Multimedia Speakers. Price was ~70$ and it was one of the best multimedia stereo-speakers at that time.

Good speakers for resonable price, but of cource with some issues\weak points:
* HF were too soft but not intereresting. Sound was too calm andboring.
* Built quality also was not very good. Enclosure was mde rom 12-13mm MDF,without any damping materials and braces. Vented port diamenter was about 34-36mm, which added some distortions on high volume. ...

At first time i made them passive, and bought amplifier:
Click the image to open in full size.
http://pics.livejournal.com/s3am/pic/00016eqz


After some little tweaks I take desigion to make absolutely new speakers...

Click the image to open in full size.
http://pics.livejournal.com/s3am/pic/000152s4

Click the image to open in full size.

Click the image to open in full size.
http://pics.livejournal.com/s3am/pic/0001zf9r

Click the image to open in full size.
http://pics.livejournal.com/s3am/pic/0001y0wb

Click the image to open in full size.
http://pics.livejournal.com/s3am/pic/00021da7/

After these measurement, I have some conclusions:
1. 50A uses descent woofers and stock enclosure parameters are not bad.
2. Tweeters should be threw to junk. So i sold them

Then I started designing new enclosure and bought a sheet of 18mm MDF.
Click the image to open in full size.
http://pics.livejournal.com/s3am/pic/0003ehpg/

Click the image to open in full size.
http://radikal.ru/F/s39.radikal.ru/i...1bd1a.jpg.html

Click the image to open in full size.
http://radikal.ru/F/s56.radikal.ru/i...3aa10.jpg.html

Net volume is ~ 15L without brace, port, loudspeakers.

Then I found suitable vented port - BR-50HP.
Click the image to open in full size.

Now I'm thinking on this to problems:
1. Selecting tweeters. I'm thinking on Vifa DX25 or Seas 22TAF.
2. I need help with Xovers.

The problem is vifa dx25 has only 4Ohm nominal impedance and 2.7Ohm DC resistance. And I'm afraid, about oeall impedance of the whole system...

So, here is my first Xover design and I want to hear your opinion about this.

Click the image to open in full size.
http://radikal.ru/F/i064.radikal.ru/...49e88.png.html


P.s. woofer's sens. is about 86db, and vifa is 93.5 db(datasheet) so I think it should be ~8db attenuation for tweeter...

I would be very pleased, if you help me with selecting tweeters (concerning optimal impedance) and designint right crossovers.

And sory for my broken English
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Old 1st April 2009, 05:41 PM   #2
Stream is offline Stream  Russian Federation
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