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maxwedge
03-06-2011, 10:34 AM
I bought some new Truextents for a pair of my 2445's (I have 4 and 2 not in use) and have a problem with one of the 2445's. The 1st went fine: I cleaned the gaps using masking tape & canned air and then ran a 1k tone while slowly snugging down the screws in a cross pattern. After that I tested from 700hz up to about 15k.

The 1st one no problems, but the 2nd one I would come across one screw that will make it buzz with the 1k tone. This is on the 1st tightening pass. I tried moving the diaphragm around but it didn't help. It's just random as to which screw will make it buzz. Usually near the end of tightening pass. :(

The driver is very clean so I think wtf!? I got a bad diaphragm? :dont-know:
So I put the JBL diaphragm back in with the same results!
So I've been listening to this thing like this for all this time?!:dont-know:
But then I didn't test it before I took it apart either!:banghead:

Anyway so I pulled one of my spares out from under the bed and put the Truextent in it and it went smooth as butter, with no buzzing.

So the question is, what do I do next. Visually the gap looks good and I suppose that I can measure it to confirm, but after that I think that is all that will be within my ability to do.
Edit: Actually I haven't found any specs on the gap so the best I could do is make sure it is concentric.

Any ideas?

Scott

more10
03-07-2011, 02:32 PM
Check the surface of the driver. If there is something uneven there the diaphragm will be slightly bent.

maxwedge
03-07-2011, 04:27 PM
Thanks for the reply.

That makes sense and I could see the diaphragm tweek as the last few screws were lightly snugged down as the buzz started. The surface look real good but I'll have to take a 2nd look.

edgewound
03-07-2011, 09:20 PM
I bought some new Truextents for a pair of my 2445's (I have 4 and 2 not in use) and have a problem with one of the 2445's. The 1st went fine: I cleaned the gaps using masking tape & canned air and then ran a 1k tone while slowly snugging down the screws in a cross pattern. After that I tested from 700hz up to about 15k.

The 1st one no problems, but the 2nd one I would come across one screw that will make it buzz with the 1k tone. This is on the 1st tightening pass. I tried moving the diaphragm around but it didn't help. It's just random as to which screw will make it buzz. Usually near the end of tightening pass. :(

The driver is very clean so I think wtf!? I got a bad diaphragm? :dont-know:
So I put the JBL diaphragm back in with the same results!
So I've been listening to this thing like this for all this time?!:dont-know:
But then I didn't test it before I took it apart either!:banghead:

Anyway so I pulled one of my spares out from under the bed and put the Truextent in it and it went smooth as butter, with no buzzing.

So the question is, what do I do next. Visually the gap looks good and I suppose that I can measure it to confirm, but after that I think that is all that will be within my ability to do.
Edit: Actually I haven't found any specs on the gap so the best I could do is make sure it is concentric.

Any ideas?

Scott

It's possible that the coil is slightly out of round or has a high voice coil winding. Did you make sure that the terminations to the terminals are aligned with the reliefs in the gap?

maxwedge
03-08-2011, 08:30 AM
It's possible that the coil is slightly out of round or has a high voice coil winding. Did you make sure that the terminations to the terminals are aligned with the reliefs in the gap?
This buzz is with 2 voice coils, the original and the Truextent. Unfortunately I didn't test the driver before I took the JBL diaphragm out.

Before I took the JBL diaphragm out I marked the driver as to where the positive terminal lines up with a red pen and I saw those two reliefs but didn't understand their purpose. This driver is one of two in an Ebay buy so I don't know if the phragms were ever replaced before. I'll pull it out and look again and might as well test the other one under my bed, LOL!

Thanks edgewound, to bad you're all the way down in the LA area because some of my old JBLs need some tlc.

subwoof
03-08-2011, 08:47 AM
Make sure the phaseplug is level / seated all the way down. Some of the first gen 2445's we got for a big club install used the same phase plugs and throats as the 2441 and a few were not aligned...:)

That one drove us nuts on the bench...:)

maxwedge
03-08-2011, 09:23 AM
I have it on the bench and am going to recheck it after I take a shower. All 4 of my 2445s are mid 80's with low 30k ser#'s. Are the phase plugs just pressed in?

Thanks

maxwedge
03-08-2011, 11:33 AM
The phase plug seems all the way down and the diaphragm is aligned with the reliefs. I rechecked the surface with a magnifying glass and I don't see any protrusions, unevenness or damage to the machined surface.

I'm going to try again to tighten the diaphragm without it buzzing...:dont-know:

Here's a couple pics..

http://i76.photobucket.com/albums/j7/maxwedge572/Music%20Gear/My%20Sound%20System/TopView1.jpg

http://i76.photobucket.com/albums/j7/maxwedge572/Music%20Gear/My%20Sound%20System/PhasePlug.jpg

subwoof
03-08-2011, 12:18 PM
chances are the machined area that the diaphram sits into isn't perfectly centered. here's how to fix that:

Get a good 90 degree tool edge ( like the side of a wood chisel ) and shave off a little material all around the diaphram's bottom edge. This way you have more room to "adjust" the centering before tightening. Nearly all of the 2445's have required this - in the old alnico days we would enlarge the guidepin holes 1/64 to achieve the same result.

This should do the trick. It's actually rare that all the tolerances align esp when mixing and matching parts from different decades.

This is the biggest reason that JBL insists that these be installed by a service center - if one doesn't fit the center can try another OR do some of these tricks to make sure it performs correctly.

Some of the old LE85's and LE175's were an absolute bitch to work on....

sub

maxwedge
03-08-2011, 12:35 PM
Ok I get that.
I've been trying to get it centered right now and find that the diaphragm deffinitly likes to be more over to the negative side and only takes a very small nudge to get the buzz to go away but tightening or loosening a screw just a tiny bit will change it.

I've just got the bare driver with the throat flat on the table with no horn on it and listening to the back side of the diaphragm. Is this how you guys normally set them up?
When I 1st swapped in the Be diaphragms I had my horns on them.

Thanks a lot subwoof

subwoof
03-08-2011, 12:59 PM
use a horn installed if possible otherwise a resonance might sound like a "buzz". I used a small horn with a carpet glued to the face to keep the volume down.

maxwedge
03-08-2011, 01:09 PM
Ok Thanks. I'll have to go out to the shed and grab a 2380. That's all I have available.
Yeah, I gotta put my ear plugs in when doing this lol.:blink:
I'm going to mod that diaphragm now.:)

maxwedge
03-08-2011, 02:56 PM
She's all better now and thanks to all who replied. :bouncy:
:cheers:

Comparing the Be and Ti diaphragms now:applaud:
http://i76.photobucket.com/albums/j7/maxwedge572/Music%20Gear/My%20Sound%20System/StackedHorns.jpg

Mr. Widget
03-08-2011, 03:06 PM
I think you could fit ay least one more horn and driver in there. :D


Widget

subwoof
03-08-2011, 03:26 PM
nah...those are little book shelve speakers....

:)

maxwedge
03-08-2011, 03:27 PM
I think you could fit ay least one more horn and driver in there. :D


Widget
You know I have a lot more...:p

Lately I've been hinting to the wifey that "we need a bigger place". You know I'd probably have every one of my speakers out then, lol.:blink:

maxwedge
03-08-2011, 05:00 PM
nah...those are little book shelve speakers....

:)
There's book shelve spks there. Gotta keep the wife happy having only one button to push,:dont-know:

maxwedge
03-21-2011, 05:48 PM
A few years back I bought two 2445's on Ebay, one that this thread is about and another (same deal). My other two I bought new in the mid 80's.

Anyway I tested my other Ebay driver and it was buzzing too!:( As I remember,when I got them I tested it and then put it under the bed because it didn't sound right LOL.

So I tried to get the diaphragm out and it was stuck! I managed to finally pop it loose and found that it had stuck to the phase plug and maybe in the gap too. It was all stuck up at the negative pole. I cleaned the gap up good, and it was really nasty, and put one of my spare diaphragms in. This one is good to go now.:)~:(

I'm not sure if it overheated or someone spilled something down the throat. These came out of a club in Canada.

http://i76.photobucket.com/albums/j7/maxwedge572/Audio/StuckDiaphragm.jpg

Eaulive
03-21-2011, 06:36 PM
A few years back I bought two 2445's on Ebay, one that this thread is about and another (same deal). My other two I bought new in the mid 80's.

Anyway I tested my other Ebay driver and it was buzzing too!:( As I remember,when I got them I tested it and then put it under the bed because it didn't sound right LOL.

So I tried to get the diaphragm out and it was stuck! I managed to finally pop it loose and found that it had stuck to the phase plug and maybe in the gap too. It was all stuck up at the negative pole. I cleaned the gap up good, and it was really nasty, and put one of my spare diaphragms in. This one is good to go now.:)~:(

I'm not sure if it overheated or someone spilled something down the throat. These came out of a club in Canada.

http://i76.photobucket.com/albums/j7/maxwedge572/Audio/StuckDiaphragm.jpg

You have to be careful when buying horns and comp. drivers that come out of stage monitors or any horn that was facing slightly upwards, they act like big funnels and are very prone to receive any liquid, beer or rain.

pos
04-01-2011, 07:37 AM
So, what about this Ti vs Be comparison?
Do you still use the 2404H ?

maxwedge
04-01-2011, 09:43 PM
So, what about this Ti vs Be comparison?
Do you still use the 2404H ?
I still use the 2404. I tried with only the 2445s and Be diaphragms and found it lacking. Using pink noise I can see that they drop off fast after around 10k. Maybe because of the bi-radial 2385 horns I use? :dont-know: I have a CD Horn eq option on my Rane AC24 x-over but I didn't mess with that much. Enabling that function does boost the highs quite a bit.

Anyway, I've been doing a lot of changes to my system in the last few weeks, mostly with crossover settings, levels, ect and was really frustrated at one point but I feel that I finally got it dialed it. I'm really liking the 2445s with the Be's crossed over ~ 500hz but felt a little nervous using them that low so I settled on 630hz with 24db/oct. They sound really nice!:bouncy: But like I was saying, my head has been a little spun lately. I think what I'll need to do, after I get it all set up right, is swap my other 2 2445s with the Ti diaphragms and see how crappy they sound, LOL!:p

If you don't remember, my system is quad amped 2245, 2206, 2445 and 2404.
Just last week I also swapped out my 2242's for 2245's so that's another story. More thump thump!:)

Here's a link to the x-over I use. It's nice but takes a light touch on the knobs and you really need an rta to set it up properly.
http://www.rane.com/ac24.html#gpm1_1

Scott

JeffW
04-01-2011, 10:20 PM
Just last week I also swapped out my 2242's for 2245's so that's another story. More thump thump!:)



Same box?

I don't have any 2242s, but tell the story!

maxwedge
04-02-2011, 06:51 PM
Same box?

I don't have any 2242s, but tell the story!
Same box tuned to ~28hz and measured.

With the 2242's I needed to run my 2 Sub1500's with a low pass at about 70hz to fill in the bottom. Don't need those with the 2245's. :) So I just use the Sub1500's for HT now:).

The 2242's are great 18's but not really ideal when used in a home situation. Their lower end response improves when used in corners and grouping several together, so their much better used in SR.

This is a BBP6 simulation of the 2 in a JBL 4645 cab tuned at 30hz. You can see how much more bottom the 2245 has. But you get a bunch of the 2242's together and that bottom comes up.
Orange=2245, red=2242
http://i76.photobucket.com/albums/j7/maxwedge572/Audio/JBL2245vs2242in4645box.jpg