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JBL 4638/4648A-8 update:


kenratboy

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No grills. They are supposed to go into a movie theater. You could make your own.

Is the speaker a 4638 or a 4648A-8? I don't know why it would say 8 ohms. Each of my woofers on my 4648A-8 are 16 ohms, so an 8 ohm speaker. You should putt the woofers and see if they are 16 or 8 ohm.

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Receiver: Sony STR-DE675

CD player: Sony CDP-CX300

Turntable: Technics SL-J3 with Audio-Technica TR485U

Speakers: JBL HLS-610

Subwoofer: JBL 4648A-8

Sub amp: Parts Express 180 watt

Center/surrounds: Teac 3-way bookshelfs

Yes, it sucks, but better to come. KLIPSCH soon! My computer is better than my stereo!

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Has anybody found the Thiele parameters for the woofer in these beasts? I am not sure that they are tuned perfectly. They seem to boom at very low frequencies on certain CD's. Not sure if it is the port loading or my own room resonances that I am hearing. The size of my room gives me fundamentals down in the 20-25 Hz range.

Jim N

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There SHOULD be tech specs on JBL's web site.

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Receiver: Sony STR-DE675

CD player: Sony CDP-CX300

Turntable: Technics SL-J3 with Audio-Technica TR485U

Speakers: JBL HLS-610

Subwoofer: JBL 4648A-8

Sub amp: Parts Express 180 watt

Center/surrounds: Teac 3-way bookshelfs

Yes, it sucks, but better to come. KLIPSCH soon! My computer is better than my stereo!

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Hey jnorv - is the 'boom' still there?

what is your overall assessment at this point?

happy or indifferent?

I was actually thinking that if one were to lay it on its side -- it would make a great TV stand -- a couple of sheets of sheet metal and a 1/2 dozen vibrapods between the cabinet and TV might provide enough shielding vibration control to prevent the picture from distorting. Of course, I'm only talking 27' TV here.

That would be only way I could do it. My listening area is way too small for that monster.

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dean

This message has been edited by deang on 03-16-2002 at 11:23 PM

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What I think I am hearing is the 3rd harmonic distortion at very low frequencies. If you look at the distortion data on the second page of the spec sheet, the 3rd harmonic takes off at about 40 Hz (-35 db). At 30 Hz it is down 20 db and at 20 hz it is down only 6db. I am going to pull one of the drivers and replace it with a blank piece of MDF and then retune the ports. I lose 3 db but I lower F3 by 12 Hz. Worth a try. I am also going to do a better job of distributing the poly fil inside the cabinet. This effectively makes the cabinet larger by about 10%.

jnorv

This message has been edited by jnorv on 03-17-2002 at 01:33 PM

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