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Old 21st January 2009, 02:03 AM   #1
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Default What Modifications can I make?

I know, I should just build one from scratch.... but I have this Polk RM7300 to play around with a little bit, and I am curious as to how modifying this speaker will sound to better understand designing my own. That probably makes sense to most of you, but try explaining that to my wife!!

The speaker that I'm looking at changing is

http://www.polkaudio.com/homeaudio/specs/rm7300system/

I have the fronts and centre, and am playing around with the centre using 4.1 for now (almost sounds better this way...). So I've taken the speaker apart now and noticed how great the build parts seem to be. I also sent the Polk people an e-mail, they said that the crossover was a 2nd order (both high and low pass) crossed over at 2360hz.

I have pic's, can't figure out how to post them.....

The crossover has the following on it:

Tweet
Air core inductor
Red Cap - MF825K 100V
res - OHM.K0R 5W 0.5ohmJ

Woof
Ferrite (?) inductor
Black Cap - Bipolar 22uF 100V
Res - OHM.K0R 5W 1.5ohmJ

As you can see in the link, the enclosure is an aluminium extruded body with plastic caps on the top and bottom, with the top part having a port (appx 3").

What I am doing tomorrow is going to purchase some duct seal to
damp the top and bottom plastic pieces, I'm guessing that I will need at least three pounds of it.

Any ideas on the crossover and if it would be worth investigating making a new one? How about different ideas for damping the aluminum enclosure? Stuffing? Anything else you can think of?
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Old 21st January 2009, 12:43 PM   #2
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Still can't figure out how to put the picture on.....
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Old 21st January 2009, 09:27 PM   #3
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C'mon.....you guys have to have some ideas......
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Old 22nd January 2009, 02:11 AM   #5
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Quote:
Originally posted by dmongrain
C'mon.....you guys have to have some ideas......
Are you trying to preview the pictures? That is broken, just post them.

The electrolytic ca could be replaced with a poly cap...

dave

PS: i had to reduce the file size of the attached picture as well (100 kB limit)
Attached Images
File Type: jpg dsc00192kl8.jpg (25.9 KB, 98 views)
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Old 22nd January 2009, 02:40 AM   #6
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see if this works, I've put the file in the through the 'Choose File' option and see the name there, not sure if I need to hit any other buttons.....
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File Type: jpg dsc00193.jpg (80.1 KB, 90 views)
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Old 22nd January 2009, 02:41 AM   #7
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That worked! now the question is, can you do more than one pic at a time?
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File Type: jpg dsc00194.jpg (81.5 KB, 89 views)
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Old 22nd January 2009, 02:45 AM   #8
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Quote:
Originally posted by dmongrain
That worked! now the question is, can you do more than one pic at a time?
No.

dave
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Old 22nd January 2009, 02:56 AM   #9
okapi is offline okapi  United States
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i did a similar project a while back. here is the thread:

First (Noob) crossover project - upgrade klipsch RF-7

what i found during the process of trying to upgrade my speakers was that, without measurement tools, altering a loudspeaker is a very difficult process. developing these tools is where i have invested my time since that thread.

i would also recommend reading one of any number of books on loudspeaker design. the loudspeaker cookbook seems to be a popular one.

i am very thankful for the help i received in that thread and i plan on reviving it soon (once i have completed my measurement software and hardware). i hope you find it useful as well.

good luck!
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Old 22nd January 2009, 05:30 PM   #10
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Thanks for the response, I read through your link and got some insight. I really liked your scientic based ouklook. I have a copy of the loudspeaker cookbook and have read through it several times now.

Before I start making these mod's perhaps it would be better to fully understand the tested response as a baseline.

As it stands right now, I have a Radio Shack SPL meter that I use in conjunction with my soundcard that can transmit and recieve at the same time. I have downloaded Room EQ and can run the Frequency response as well as a couple of other tests that I am not too familiar with.

What other tools/programs can I use that are low cost? Do you know of any webpages that are dedicated to testing speakers and analyzing the information?
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