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JBLROCKS
02-21-2005, 09:09 PM
Got a puzzler here to ponder over...A couple of weeks ago I bought a pair of speakers froma thrift store. Not sure of brand, however they looked well-built and a good bargain. Main reason I bought em was for a "Project"
Boxes were pretty much trashed but derivers looked nice and substancial. So I bought em took em home and hooked em up...High emd really sings!!! BUT....NO BASS!!!! hmmmmm.....pulled woofers out to see if anything
inside was astray with X-over or anything. Looked fine. Pulled em apart and salvaged components (mids and tweeters I am using for "My Plan" ) Friend of mine has pair of bookshelf speakers he wanted to rehab ( mismatched
woofers with dead foam and one dead mid and dead tweeter. Guess he is attached to them) Told him I have a pair of woofers if he is interested. He brought one of his boxes over and I dropped the woofer in it.....ARGH!!!
NO BASS!!!! <again> These had been refoamed, good looking job, they pulled dustcaps and shimmed the coiles etc did everything right. No strange noises or anything. Checked VC and DCR was 4.6 & 4.8 ohms. hmm
Even stuck one of them in a sub box I have got with high efficiency amp...took much more power than original to produce same sound...

Here is the only thing I can figure....The new foam surrounds seem very "light" (cone very easy to move back and forth not stiff) Perhaps new surrounds were "lighter" tahn the old ones and were not able to control cone properly..

Whatcha think?

I am TRULY PUZZLED!!!:hmm: :blink:

Thanks

Don C
02-21-2005, 09:53 PM
Demagnetized? Voice coil is no longer glued to the former?

Mr. Widget
02-21-2005, 10:45 PM
By no bass, do you mean the woofer plays but is deficient in bass?

Widget

JBLROCKS
02-22-2005, 05:05 PM
I checked these things over with a fine tooth comb. Magnets are fine. (BIG AND POWERFUL!!) Coil, spider etc all look good.

You can watch the cone move but serious lack of bass. Like I said I tried it in three different cabinets with the same results! :blink: :hmm: :cooked:

Thanks for input!

pelly3s
02-22-2005, 05:15 PM
maybe the woofers just suck that much.

Mr. Widget
02-22-2005, 05:21 PM
That is my guess too.

You say the mags are big and powerfull. A woofer with a really large magnet can easily loose LF performance as it will shift the TS parameters to the point of becoming a mid bass driver.

Widget

Robh3606
02-22-2005, 05:25 PM
Do you have any idea what they are??? Looking at a 15' E-145's and a 12' like a 122A and the 122A smokes the 145 below 40Hz. You would never quess that by looking. Some "woofers" simply don't because of the design. Don't let size or a big magnet fool you. Can you drop a picture in the forum??

Rob:)

Zilch
02-22-2005, 05:30 PM
Acoustic suspension drivers flappin' in ducted port boxes.... :D

Vented pole drivers with permeable dust caps.... :D

Demagged crap thrift shop woofers.... :D

Take 'em to a reconer and ask what's up with them....

GordonW
02-22-2005, 07:11 PM
Sounds like, to me, one of two possibilities:

a) the woofers need a much bigger box, probably ported

b) they may be more of a midbass driver, like for a PA system or something similar).

I've seen high-efficiency woofers that simply didn't do anything bass-wise, until they were in appropriately big boxes. Didn't get excessively boomy or anything, just didn't have substantial bass...

Regards,
Gordon.

JBLROCKS
02-22-2005, 08:18 PM
These were in large sealed boxes approx 2.5 -3.0 C.F.
Judging from the overall appearance of the boxes and drivers I would say these were very high quality/high cost speakers about 20 or so years ago.

I tried them in ported boxes and a subwoofer box with same results.

Non vented poles.

Magnets seem powerful. at least externally.

:hmm: :confused: :dont-know

Mr. Widget
02-22-2005, 09:18 PM
That looks like a pretty low end (price wise) woofer. It is hard to judge a woofer by looking at it alone. It may be defective, but it wouldn't surprise me if it is as good as it ever was.

Widget

JBLROCKS
02-24-2005, 09:33 AM
This is my final update to this thread. I pulled out one cone and examined the coil etc and all looks fine. Magnets SEEM powerful but I have no way of telling.
I am guessing that they may have lost enough magnetism to result in a substantial loss of power.

Thanks for all the input on this puzzle!http://audioheritage.org/vbulletin/images/smilies/applaud.gif

Mr. Widget
02-24-2005, 09:45 AM
Looks like the puzzle has been terminated.

Widget

Alan Fletcher
02-26-2005, 05:44 AM
C'mon, have some fun! Plug the other one into the 110VAC outlet! :D

-A

JBLROCKS
02-26-2005, 08:25 PM
:nutz: :cooked: :shock: LMAO!!!! <get the fire extinguisher ready!!>

Steve Schell
03-01-2005, 01:05 PM
I dunno; these look to me like low price "strokers", woofers designed to produce bass through long excursions in a sealed box. It is unlikely that the ceramic magnets have lost much of their charge, but the flux density may have only been 3 or 4 kilogauss to begin with due to a wide, sloppy voice coil gap. That looooong voice coil indicates a severely overhung design, so only a portion of that coil is seeing the gap flux at a time. They look to me like low efficiency devices, and will need a lot of power to make big noises. Try hitting them with a Dyna 400 and see what happens.