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Old 26th June 2003, 06:25 PM   #1
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Default JBL active speakers using LM3886

I have just been offered a pair of JBL LSR25P monitor speakers at a very good price, and doing some research I found the schema on the JBL website. They use 1 amp for the tweeter and 2 bridged for the woofer with active crossovers.

So, I'm posting the link to the pdf in the hope it might help some people out trying to do a similar thing

http://www.jblproservice.com/pdf/LSR...ies/LSR25P.pdf
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Old 26th June 2003, 06:41 PM   #2
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Thanks!.....Imagine trying to p2p that schematic!!!...hahahaha
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Old 26th June 2003, 06:52 PM   #3
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A lot of the complication comes from the various switchable options for the built in sub hp xover, baffle step compensation if used next to a big monitor, and 3 different slopes on the high end to compensate for room response etc.

If I get them, (which is looking likely), then I will post some pics and give some details on the other op amps used.
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Old 26th June 2003, 06:53 PM   #4
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Very interesting as i was thinking about doing this for my computer speakers.. Humm..
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Old 26th June 2003, 07:15 PM   #5
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Default Not a Genelec...

Well its not a Genelec, but if the price is right, who cares.

Ive been a big fan of active monitors for some time, these should do quite well for you. Looks like there is some fine Harmon engineering in there.

Very nice of them to show us thier crossover network too.
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Old 27th June 2003, 01:16 PM   #6
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hey pinkmouse,

Interesting piece of kit to try some good op-amps.
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Old 27th June 2003, 05:04 PM   #7
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Well I am getting them for a specific task, as I need to knock together a little playout video for a conference I'm doing next week. I was planning on building some monitors, but this job came in at short notice, and is paying well enough just to go out and buy them.

So I'm sure I will be doing some tweeking when that job is wrapped, swapping out op amps looks like it might be a good start, as well as some decent Schottky diodes in the PSU.

Strangely, however, I was doing some serious listening to them this morning, before I handed over the cash, and I noticed none of the slight "compression" type sound I noticed when I built an inverted GC with the same chip. So I wonder if the 3886 is a chip that needs a litttle more support circuitry to get it to sound at it's best.

And yes, they are not quite Genelecs, but then again, it would be a close run thing to buy the parts to build them for the price I am paying
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Old 27th June 2003, 05:31 PM   #8
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Default But then again...

But then again a Genelec wouldn’t be quite appropriate for a conference application, even if it had a platinum budget.

Thats an interesting observation about the compression.

Are you getting more than two? These things would be killer for a small home theater.
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Old 27th June 2003, 05:44 PM   #9
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Default Re: But then again...

Quote:
Originally posted by Da5id4Vz
But then again a Genelec wouldn’t be quite appropriate for a conference application, even if it had a platinum budget.
You would be suprised at the high production values used in some conferences, one we did for HP had the set designed by a world famous artist, very high quality surround sound, and all the video inserts were filmed on 35mm, and then transferred to HD video for playout.

Quote:
Thats an interesting observation about the compression.
Yeah, I posted my impressions of all the chips in four or five posts somewhere in the NJAGC thread, feel free to look

Quote:
Are you getting more than two? These things would be killer for a small home theater.
I know where there are two more SH, but at about £350 each new I don't think I will be buying the fifth. Besides, it's much more fun to build them

p.s. Pics will be coming soon, I just had the phone call to say they will be dropped off tonight...
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Old 27th June 2003, 07:06 PM   #10
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Over the years Ive worked around quite a few corporate staging people. They often seem to have the best budgets, most interesting projects, and highest level of satisfaction compared to their theater, broadcast, and documentary counterparts.

Another neat aspect about the niche is that it is (oops was) fairly unknown to the usual "characters" that can make those other worlds such a joy to work in.

I dissected a Genelec 1031A late one night about a decade ago. I was floored to see a 2 channel chip amp with a bunch of surface mount op amps for the x-over. I cant remember what the genre of the chip was (STK?) but do remember that they had put some effort into mechanically decoupling the amps from the speakers vibration.
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