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Multi-Way Conventional loudspeakers with crossovers

jbl lx44's
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Old 9th August 2018, 01:22 AM   #1
jimmy audio is offline jimmy audio  United States
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So I got a pair of lx44 cheap. Upon investigation the woofers have been replaced with 10 ohm yamaha drivers hows that gonna work out the origionals were 5 ohm. they sound good but the crossover network must be getting messed with. any thoughts on how to mod them for origional sound?
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Old 9th August 2018, 04:22 PM   #2
system7 is offline system7  United Kingdom
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If you're going from 5 ohms dc to 10 ohms dc woofers it does mess up sound and impedance.

I think these speakers got foam rot, which is why someone changed it. To get it flat you probably need 6.2mH and 26uF on the bass.

No idea if levels will be right, and you just take your chances on bass response, especially on tuning the reflex port.
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File Type: png JBL LX44 Crossover.PNG (182.6 KB, 59 views)
File Type: png JBL 5-10 ohm conversion.PNG (18.7 KB, 59 views)
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Old 9th August 2018, 05:05 PM   #3
jimmy audio is offline jimmy audio  United States
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Thanks Steve for your response. I bought a pair of these new for lots of cash (at the time) and still use them daily. Sweet sounding, to say the least. So seeing a pair at a garage sale for 50$ I talked them down to 40 and took them home. They sound good, surprisingly good. But in looking up the yamaha drivers the spec's don't compare to the 408g drivers in the originals and side by side tests show a huge gap from about 180hz to 320hz down 9db from the originals. instead of messing with a superb crossover will look for a more suitable replacement driver. I know the 408g's are unavailable. If anyone knows of a replacement or has a pair of 408g's that need reconing please let me know. I think they are worth saving
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Old 9th August 2018, 05:46 PM   #4
system7 is offline system7  United Kingdom
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Replacing woofers is a tricky business. Seems the LX44 is 91dB SPL and the original 408G is some sort of 8" polycone.

It's up to you, but this 91dB PE Eminence special might do better than the Yamaha replacement:
Eminence 8" Paper Cone Professional Woofer 8 Ohm

It's unusual. Heavy old cone on that one, which is why it's not as loud as most Eminence drivers. Otherwise the Eminence Beta 8A at 95dB might be OK. It being very difficult to guess how loud you need to go and how bafflestep affects it.

But since I thought that half the speakers in the US use Eminence drivers, maybe you can borrow one for testing.
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Old 9th August 2018, 06:04 PM   #5
phivates is online now phivates  United States
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There's a good chance the 'Yamaha' woofers are Eminence - but they're not a good fit
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Old 9th August 2018, 06:24 PM   #6
system7 is offline system7  United Kingdom
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How do you know that?

It gets worse, actually. I just reread the Eminence woofer spec. It's all a bit dubious. The Photo shows a 4 ohm driver with the same 290-4007 part number. I don't know what is going on there. One of the comments says it's 4 ohms too.
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Old 9th August 2018, 11:32 PM   #7
jimmy audio is offline jimmy audio  United States
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Found a pair of re-coned origional 408G drivers on ebay for 125$ + shipping!! gonna get e'm! thanks guys
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