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Old 14th March 2006, 07:58 PM   #11
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Those look really ood

What PR did you use?
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Old 14th March 2006, 07:59 PM   #12
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Neat! What's the volume of your speaker? Did you use any extra mass on the PR?
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Old 15th March 2006, 03:52 AM   #13
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this one?

http://www.madisound.com/cgi-bin/ind...22815&pid=1073
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any one use this?

http://www.madisound.com/cgi-bin/ind...22815&pid=1924
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Old 15th March 2006, 05:05 AM   #14
knorke is offline knorke  Germany
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I used indeed the seas sp17r in a enclosure with around 10l volume.
I didn't use any extra weight on the pr which should give us a resonance
around 60Hz....
I didn't do any extensive listening/testing/measurements on these speakers
since it was a rather quick build for a friend who needed a present for his
girlfriends birthday...
But the initial impresssion was good, quite strong bass output but not very deep
though.
I didn't use any baffle step or other correction circuits...
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Old 15th March 2006, 12:05 PM   #15
badman is offline badman  United States
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Nice job. Sounds like you're a good buddy, building speakers for HIS girlfriend. Guess she's pretty The 60Hz tuning might be a little high, might be worth adding a small weight to the PR to lower the tuning and damp the peak a bit. But nice job!
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Old 15th March 2006, 12:47 PM   #16
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Hi,

if you use the Dayton / PartsExpress SD215 PR (no added mass) you can reach 45Hz -3dB in a 0.5 cu.ft enclosure. Interesting approach - I only tried reflex and was very pleased. Worth a try.......

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Thorsten
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Old 15th March 2006, 03:56 PM   #17
SCD is offline SCD  Canada
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Hello Fellows:
I am thinking this is a good way to deal with this driver. I have made a couple of TL designs that have been only moderate performers. There is a tendence to tune the cabinet too low with this driver. When the music volume is low they sound fine but as soon as you turn it up the driver tends to flap and fart at the lower frequencies. I am thinking the high excursion may need to be tamed down a bit and either a sealed box ala the bipolar bipoles or a PR may solve the problem. Can someone explain a bit of the concepts around using a PR and how to decide on PR size.
thanks for the help
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Old 15th March 2006, 04:47 PM   #18
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Hi SCD,

PR size is a rule "by thumb". It should be 1,5 - 2 times the size of your drivers SD. The Dayton PR is very big in relation to FR125S.

A PR combines the good things of closed and reflex without the bad stuff (for example port farts ). You tune your frequency by PR weight. The math behind is of course more advanced .....

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Thorsten
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Old 15th March 2006, 05:25 PM   #19
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Quote:
Originally posted by SCD
Can someone explain a bit of the concepts around using a PR and how to decide on PR size.
Scotty, I'm glad you asked. I know you love my logic so here goes:

Small PR = even smaller woofer

Big woofer = even bigger PR.

Actually buddy what I do is simple: If it's one woofer then the PR should be a minimum one size up or two of the same size. Now because you're slow, I'll explain it.

One 8" woofer requires a minimum of one 10" or two 8" PR's. And we haven't yet touched on the mass of the thing. I'm sure others smarter than myself can chime in with the details. As you know I tend to do things a little different than the rest of the world.

Not sure what the upper boundary would be ie: at what point the amount of PR becomes too large for the woofer.

* For those of you who don't know, SCD is actually a very intelligent and extremely funny guy. I was taking liberties with him.
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Old 15th March 2006, 08:50 PM   #20
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I agree with the dudes. A 6"-8" PR with ~8mm xmax should be enough for the FR125, or two 5" if you can find PR's that small. WinISD Pro can model PR's with ease. It seems that a PR will tame the 100-150Hz bump normally present with small vented designs with FR125. It slightly limits the lowest output (F3 slightly higher) but reduces group delay with a large margin.
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