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Old 25th July 2013, 06:41 PM   #11
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Quote:
Originally Posted by Quartz19208 View Post
I just recalled that the foam in the back plate of the left(louder) 2446 have degraded into dust. would that be the reason for my problem?
That would make quite a difference.
JBL used felt back in the "good old days" 50 year old felt generally is OK, foams vary widely.

Replace the foam, remove the diaphragms, clean the gaps, re-install and align the diaphragms and you may find the differences are reduced.
The alignment posts are a guideline, proper alignment using sine wave tones and shifting the voice coil in the gap is still often needed to eliminate voice coil dragging, which shows up as a "buzzing sound" when sweeping sine waves from around 200-500 Hz. You only need a fraction of a watt for testing, adjust the sine wave for a comfortable level at around 1200 Hz and sweep down and up.

Also check for any sharp edges on the horns, they don't always come out of the mold cleanly.

At any rate, all diaphragms are not created equal, if you swap diaphragms and the problem persists in the opposite driver you know it is diaphragm rather than a driver (magnetic) difference.
Also, when cleaning the gap, use some card stock to make sure the gap is consistent, the pole piece or keeper can shift if it was ever dropped or slammed around.

Art

Last edited by weltersys; 25th July 2013 at 06:44 PM.
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Old 26th July 2013, 04:31 PM   #12
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Hello jjrenman!
I have found the great unbalance to be slightly due to room acoustics however the difference was totally eliminated when I changed the entire driver with the spare I left at my mentor's shop. With the spare the leis still louder despite of which of the two properly functioning drivers I am using for the left side.
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Old 26th July 2013, 04:48 PM   #13
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Hello weltersys!
I have decided to remove all of the old foam on both my properly functioning drivers for the time being until I can get a suitable replacement (would felt be better?). Strangely swapping the diaphragms around did not alleivate the problem thus I changed the weak driver out for a spare. Looking at the gap of the weak driver I could find no problems . The gap was uniform through out , the phase plug and the gap were clean. The driver was technically in a 'minty' condition I really could'nt find a fault that should cause it to sound weak.

Unlike my altec 802 8g , the 2446 does not have aligning pins rather they have a depression in which the outer ring of the diaphragm sits in snugly. Making it impossible for any adjustment of the diaphragm.
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Old 26th July 2013, 06:10 PM   #14
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Felt would work fine as a replacement for the foam, and won't deteriorate.
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Old 27th July 2013, 09:14 AM   #15
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Would you happen to have any reccomendation as to where I can purchase the felt?
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Old 27th July 2013, 09:59 AM   #16
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Quartz,

Agree that checking the drivers are matched is important. Do you have any way to measure the drivers?

Personally I would be measuring, comparing, measuring again, comparing each pair of drivers just for level output to see how well matched they are. Make sure each pair of drivers are in the same condition - either a pair of new or a pair of old, but one new one old will never be a good idea.

If the output is slightly off between drivers you can accomodate that in the xo's.

equally, did you measure and check all the components you put into your crossover?

Many tollerances for xo components can be low, you may be unlucky in just having really poorly matched xo's. Personally I'd pull them apart and measure EVERY component to make sure they're performing as they should. You can measure the effective resistance of inductors/caps in the same way as you'd measure impedance curves with arta on a computer (very cheap and relatively easy, if time consuming) - gives you a chance to calculate the actual % variation)

I understand you've already tried swapping the speakers around in the room and switching driver polarity?
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Old 29th July 2013, 09:36 AM   #17
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Hello nanno!

The drivers were bought together at the same time. At risk of sounding like a über dummy, I have to admit
that the angle of the right speaker was off by around 5degrees which after rectification, have brought the balance back. (Are these horns so directional?)
Nonetheless I ought to measure to match my drivers and my crossover components when I get the time.
Thank you!
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Old 29th July 2013, 02:01 PM   #18
mortron is online now mortron  Canada
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Room acoustics and speaker placement have oft led me to believe I have issues with my system only to find a few degrees of rotation to a speaker will solve the issue. That being said, without a symmetrical room, you will likely perceive some type of imbalance or imaging issue. I had to find the best orientation and live with it, while making minor adjustments.
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Old 29th July 2013, 08:43 PM   #19
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Originally Posted by Quartz19208 View Post
Would you happen to have any reccomendation as to where I can purchase the felt?
Felt shoe liners could be used, or the jute felt backing used beneath carpeting.
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Old 30th July 2013, 01:09 AM   #20
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Originally Posted by weltersys View Post
Felt shoe liners could be used, or the jute felt backing used beneath carpeting.
Never thought of wool shoe felt, now I can reappropriate my Mukluc's.

Never found a use for them in SUNNY HOT FLORIDA

Quartz, the felt under automotive carpet would also work. Junk yards should have tons, would cost next to nothing
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