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doyall
09-06-2007, 08:16 AM
After two weeks of rearranging and running new cables for practically all of my AV equipment to accommodate a recently acquired B460, I finally got to fire it all up. Signals run from a Nakamichi CA-5 preamp into a BX63A crossover then to a bridged JBL Urei 6360 amp. I had it cranked up to what I thought was a moderate level and everything was sounding wonderful until I heard a rather loud pop immediately after a powerful bass note. Girlfriend heard it too. I take it this was the voice coil bottoming out. Is the 2245H just not designed to be driven hard or could this be a result of spider fatigue/some other cause? If it canít be driven any harder than I had it, then its use for home theater would appear to be severely limited.

toddalin
09-06-2007, 09:34 AM
I've bottomed out 130As and 2235s when used as subs in our home theater and also wondered "is that all there is?" Luckily, I quickly turn down the volume and have done no apparent harm.

I've never bottomed out the W15GTI, probably because of its architecture (i.e., dual voice coils out of phase that limit cone travel at the extremes).

You may try blocking one of the ports to limit woofer excursion, although, it would seem that the design should consider this.

Robh3606
09-06-2007, 10:03 AM
I would be curious as to what it was, ie sound effect explosion that did the deed. These woofers are in bass reflex cabinets and should be protected from high level bass below the box tuning frequency. Simply said they should be run with high pass filters in place. You have to remember that these designs are older and done long before HT and digital cannons at 10 ft, That type of special effect LFE bass was not a consideration back in the early 80's.

I think the BX-63 has one:blink: Did you see how much cone excursion you are getting?? You can get close to an 1 inch out of a 2245 so I would pop the grille cloth and see what is actually going on. You getting any pumping or offset of the woofer?? Is the woofer new or is it old?? You could have an offset spider depending on how the driver was stored.

Rob:)

Thom
09-06-2007, 10:09 AM
Real non expert here but if that is what you heard it may have been from too strong of a signal (information or noise) at a frequency lower than it can handle. A subsonic filter may be all you need. Caution, long distance trouble shooting is always pretty iffy.

doyall
09-06-2007, 10:21 AM
I would be curious as to what it was, ie sound effect explosion that did the deed. ... You have to remember that these designs are older and done long before HT and digital cannons at 10 ft, That type of special effect LFE bass was not a consideration back in the early 80's.
... Did you see how much cone excursion you are getting?? You can get close to an 1 inch out of a 2245 so I would pop the grille cloth and see what is actually going on. You getting any pumping or offset of the woofer?? Is the woofer new or is it old?? You could have an offset spider depending on how the driver was stored.

Rob:)

It was playing music when it happened, either Pink Floyd or Barry White, I can't remember. I'm kind of reluctant to try any LFE's at the moment.

As a matter of fact I was watching the cone when it happened. The cone excursion could readily be seen but I don't think it was anywhere close to an inch. (With that small roll on the surround seems like an inch would blow it out.) If I remember correctly it happened after a quick series of maybe three powerful bass notes. Could this have caused "pumping?" I'm not exactly sure what that is. I haven't had the 2245 out of the cabinet to see if there is any discernable offset but that will be forthcoming. According to the previous owner this is the original woofer (he said he bought it new) and it was refoamed a year or two ago. From the outside it looks like a quality refoam job. He said good things about the shop that did the work. I specifically ask him if he ever rotated the woofer and he said he did not. Should I try rotating it?

doyall
09-06-2007, 10:27 AM
Double post. Sorry.

Thom
09-06-2007, 10:47 AM
If it's offset, I don't know if I can recommend this but I had a 2240 with real bad offset. I'm not sure if it was hurting anything but it was bothering me. I set it out in the sun face down supported by the rim. Put a couple of small balloons between the frame and the cone to give it a slightly positive offset and let it bake and then cool down. When I took out the balloons and brought it in it had no offset. Way to recent to know how permanent it is.

grumpy
09-06-2007, 10:48 AM
you have the manual?

http://manuals.harman.com/JBL/HOM/Owner%27s%20Manual/BX63om.pdf

If it's set up properly and still bottoming out, it's probably not what you need
for your environment/setup. -grumpy

doyall
09-06-2007, 11:02 AM
you have the manual?

http://manuals.harman.com/JBL/HOM/Owner%27s%20Manual/BX63om.pdf

If it's set up properly and still bottoming out, it's probably not what you need
for your environment/setup. -grumpy

I've got the manual and followed it to the letter.

While it didn't really sound like it was out of phase with my L250's, if it was could that have caused the cone to be pushed back farther than it otherwise should go?

Please don't tell me that I've spent all this time and money for naught. :banghead:

Thom
09-06-2007, 11:10 AM
Have you tried playing different tones through it?

I'm not suggesting that this is you, but sometimes people have a little boost here and a little boost there and when every thing is added up they have 30db boost at 10 hz and you can't hear it so until something fails it goes unnoticed.

doyall
09-06-2007, 11:18 AM
[quote=Thom;184057]Have you tried playing different tones through it?
quote]

Haven't tried it but I certainly will.

grumpy
09-06-2007, 12:13 PM
Please don't tell me that I've spent all this time and money for naught.I certainly hope not, and you can always try the phase inversion, but short of
a failure (seems unlikely), having the will to turn down the LF Gain on the BX63A,
or relocating the sub for better reinforcement (or less bad cancellation), you might get
what you're after via another path.

Verifying that the 2245+cabinet frequency of minimum cone motion is close to where
the BX63A peaks (roughly 25Hz?) might be worthwhile (it does have an infra-sonic
filter built in as well as DC blocking). -grumpy

good read:
http://audioheritage.csdco.com/vbulletin/showthread.php?t=610&highlight=bx63A+schematic

doyall
09-06-2007, 12:34 PM
... Verifying that the 2245+cabinet frequency of minimum cone motion is close to where the BX63A peaks (roughly 25Hz?) might be worthwhile ...

I suppose that if I have to ask how to do this I am not really equipped to handle it? :confused:

grumpy
09-06-2007, 12:41 PM
If you can do "tones" via CD or computer, that would get you there.
Could be a red herring anyway.
I'm really trying to not sound too pessimistic.

In some rooms, that sub can do dance-club level sub-bass, but it is a subwoofer...
a lot of folks crank up the sub level to hear or feel -bass- as opposed to sub-bass
and end up overdriving the very low end (which the BX63 has already peaked up 10dB).
Are you sure your amp isn't clipping? (~300W? ... wouldn't be terribly surprising)
Since there really aren't lots of recordings with much sub-bass material, it's easy to do.
The beginning of Dark Side of the Moon is an interesting example... if that's not shaking
your vases without causing the voice coil to bottom out, there's something wrong :)

-grumpy

Robh3606
09-06-2007, 01:17 PM
The BX-63 has a subsonic filter. Listening to music it should be fine. I went back to double check the x-max and its about 3/4 inch peak to peak. That's a lot of movement and that is not the X mechanical where you would hit. By pumping I meant the cone moving slowly backwards and forward from a DC offset. Or if when you hit those 3 notes if the cone doesn't go back to rest like it gets offset by a DC voltage. I just went through this with a pair of sub's. In this case the spiders were offset from in box storage. Fortunately they were easy to fix. That woofer should kick butt I am sure you can figure out what the issue is.

Rob:)

grumpy
09-06-2007, 01:47 PM
Must have been a good evening, otherwise...

...either Pink Floyd or Barry White, I can't remember.:rotfl::rotfl::rotfl::rotfl::rotfl:

Source was not a turntable, I presume?

doyall
09-06-2007, 01:48 PM
... Are you sure your amp isn't clipping? (~300W? ... wouldn't be terribly surprising) ...


As the amp is not in plain view I couldn't see the clipping lights to tell. But the attenuator dial on the amp was turned to about 50% of max and the attenuator dial on the BX63A was around 75% of max. Volume dial on the pre-amp not even at 50%. The amp specs 600 watts in bridged mode but I am suspect of that.

doyall
09-06-2007, 01:50 PM
Must have been a good evening, otherwise...
:rotfl::rotfl::rotfl::rotfl::rotfl:

Source was not a turntable, I presume?

Very good evening, thank you!

Source was CD player.

grumpy
09-06-2007, 02:04 PM
ah 6260... even a 600w amp (at 8 ohms) can run out of gas ( & only a little louder than 300w).
I would try backing off the BX63A gain as well as checking for the offset or slow
drifting that others have suggested. Is this repeatable (knowing that you'd really not like
to do this on purpose again)?, but perhaps doesn't happen at all below some threshold?

Your control ranges seem reasonable given how I've used a 6260,
the max gain of the BX63A (12dB), and what I assume is "normal"
for the rest of your system (pre-level).

doyall
09-06-2007, 02:09 PM
[quote=grumpy;184086] ... Is this repeatable (knowing that you'd really not like to do this on purpose again)?, but perhaps doesn't happen at all below some threshold? [quote]

Haven't really had much more of an opportunity to listen. I suppose in the absence of any other problem I will ultimately find that threshold and turn it back a little.

Appreciate all the discussion.

GordonW
09-06-2007, 02:58 PM
One other consideration- I agree with the folks suggesting looking for suspension offset... however, I recently had a problem with a JBL 6260 amp, where it was slightly "unstable" due to some bad solder joints and a few tired, worn-out capacitors. It would "walk" the woofer slightly in and out (infrasonic motion)... the louder the output, the more the "walk" would increase in amplitude. This, combined with source material with reasonably loud bass, could "use up" the available excursion of the woofer, and cause it to momentarily bottom out, at weird times.

Had the amp recapped and the errant solder joints re-flowed, and it seemed to be MUCH better.

Those amps, especially if they've been used in an application previously, where they were left on all the time, can be in need of the type of retrofit and repair I describe above... I think of it a maintenance, realistically. Anything of that age used much, and it's gonna need a tune-up, sometime...

Regards,
Gordon.

grumpy
09-06-2007, 03:30 PM
Really good point, Gordon :)

opimax
09-07-2007, 06:07 AM
I have 250s and a b460. the b460 is powered by a adcom 555 bridges to 600, no b63 (yet :)) but a Velodyne SMS-1. I have run out of gas earlier than I expected myself. I thought my woofer was in question, brought to another members set up, it was fine. my out of power though comes from HT use . I think an even larger(different) amp would be a good test

Mark

doyall
09-07-2007, 01:18 PM
While shopping eBay I have just run across two purported 2245H raw woofers for sale. This one

http://cgi.ebay.com/JBL-2245H-18-LOW-FREQUENCY-TRANSDUCER-SUBWOOFER_W0QQitemZ270163565589QQihZ017QQcategoryZ 47095QQssPageNameZWDVWQQrdZ1QQcmdZViewItem (http://cgi.ebay.com/JBL-2245H-18-LOW-FREQUENCY-TRANSDUCER-SUBWOOFER_W0QQitemZ270163565589QQihZ017QQcategoryZ 47095QQssPageNameZWDVWQQrdZ1QQcmdZViewItem)

appears to have the treated cloth accordian surround and this one

http://cgi.ebay.com/JBL-2245H-Pro-Audio-18-subwoofer-18-inch-2245_W0QQitemZ150158493392QQihZ005QQcategoryZ47095 QQssPageNameZWDVWQQrdZ1QQcmdZViewItem (http://cgi.ebay.com/JBL-2245H-Pro-Audio-18-subwoofer-18-inch-2245_W0QQitemZ150158493392QQihZ005QQcategoryZ47095 QQssPageNameZWDVWQQrdZ1QQcmdZViewItem)

appears to have a (rotted) foam surround.

Which is the correct surround for the 2245H?

The one I have in my B460 is a foam surround the seller said was replaced in the last couple of years. If the treated cloth accordian is the correct surround could this be the root of my bottoming-out problem?

Fred Sanford
09-07-2007, 01:33 PM
Here's my 2245H, OEM cone, replaced foam.

je

grumpy
09-07-2007, 01:58 PM
accordian surround? likely reconed as 2240... (same frame/mag, no aquaplas).

2245 has a foam surround as shown in Fred's pic (and aquaplas applied ... sometimes white, sometimes black,
on the back of the cone) -grumpy

(so, no... that shouldn't be the issue)

opimax
09-07-2007, 02:34 PM
In another thread it has been pointeed there are different factory cones. Some w/lesser number of ribs, that don't extend all the way to the outer edge...

Mark

grumpy
09-07-2007, 02:38 PM
:yes:

Thom
09-08-2007, 02:30 PM
would say that rotted foam is probably original but not correct. More seriously if yours isn't new and has been refoamed you can get it good enough not to touch at mild levels and still raise hell at higher levels and pride prohibits me from telling you how I know that.

Zilch
09-10-2007, 02:41 PM
Inspect the foam and spider, particularly their attachment, very carefully.

A single B460 flexes walls and ceilings here with subsonics. Something is awry....