Carlspeak Posted June 15, 2011 Report Share Posted June 15, 2011 Working with my speaker parts distributor, I was able to acquire the parts to recone a vintage alnico magnet cloth surround woofer. Following some testing and comparing the results with previous tests in my records done on cloth and foam surround woofers, I found the recone results to be closer to the refoam type than the earlier, cloth surround type.Below is a little table summarizing the test results. The two cloth results are from two different woofers measured quite some time apart, but were what I had on file.TYPE Fs QTsRECONE 51 1.37CLOTH 33&46 0.54&0.85REFOAM 52 1.07 Below is a picture of the reconed 4x woofer. The foam is the filleted type commonly seen on Boston Acoustics woofers. Link to comment Share on other sites More sharing options...
RoyC Posted June 16, 2011 Report Share Posted June 16, 2011 Working with my speaker parts distributor, I was able to acquire the parts to recone a vintage alnico magnet cloth surround woofer. Following some testing and comparing the results with previous tests in my records done on cloth and foam surround woofers, I found the recone results to be closer to the refoam type than the earlier, cloth surround type.Below is a little table summarizing the test results. The two cloth results are from two different woofers measured quite some time apart, but were what I had on file.TYPE Fs QTsRECONE 51 1.37CLOTH 33&46 0.54&0.85REFOAM 52 1.07 Below is a picture of the reconed 4x woofer. The foam is the filleted type commonly seen on Boston Acoustics woofers.Nice, Carl...The surrounds you used are very good replacements for AR woofers.Roy Link to comment Share on other sites More sharing options...
michiganpat Posted June 16, 2011 Report Share Posted June 16, 2011 Working with my speaker parts distributor, I was able to acquire the parts to recone a vintage alnico magnet cloth surround woofer. Following some testing and comparing the results with previous tests in my records done on cloth and foam surround woofers, I found the recone results to be closer to the refoam type than the earlier, cloth surround type.Below is a little table summarizing the test results. The two cloth results are from two different woofers measured quite some time apart, but were what I had on file.TYPE Fs QTsRECONE 51 1.37CLOTH 33&46 0.54&0.85REFOAM 52 1.07 Below is a picture of the reconed 4x woofer. The foam is the filleted type commonly seen on Boston Acoustics woofers.what foam was used on the refoamed? a generic? one of the floppy 8" JBL or boston surrounds? with the QTS that high (1.37) on the recone, I'd imagine response might be a bit "humpy" on the low end....is there a way to drop the QTS? more compliant spider? would adding mass to the cone raise or lower it? Link to comment Share on other sites More sharing options...
RoyC Posted June 16, 2011 Report Share Posted June 16, 2011 Working with my speaker parts distributor, I was able to acquire the parts to recone a vintage alnico magnet cloth surround woofer. Following some testing and comparing the results with previous tests in my records done on cloth and foam surround woofers, I found the recone results to be closer to the refoam type than the earlier, cloth surround type.Below is a little table summarizing the test results. The two cloth results are from two different woofers measured quite some time apart, but were what I had on file.TYPE Fs QTsRECONE 51 1.37CLOTH 33&46 0.54&0.85REFOAM 52 1.07 Below is a picture of the reconed 4x woofer. The foam is the filleted type commonly seen on Boston Acoustics woofers.Carl,...just took a closer look at your numbers after reading Pat's post. The spider you used is too stiff. Fs should be around 35hz. 52 is way too high. The Boston FF foam surrounds are very compliant and would not be the cause.Roy Link to comment Share on other sites More sharing options...
Carlspeak Posted June 17, 2011 Author Report Share Posted June 17, 2011 The spider I used wasn't too bad. The foam on the new cone was thicker than my 'stand alone' BA foams. Next time I'll strip the foam from the cone (they come pre-assembled) and use a stand alone one. Maybe that will lower Fs a bit.The old refoam data point is the only one I could find. Is that normal? I don't know.I have found after numberous measurements the bass spike is typical in the 4x speaker. Unfortunately, the recone job was for a customer in Texas who had the cabinets so I could not do a test with the reconed woofer in the box. I'll have to await feedback too determine the acceptability of the result I got. Link to comment Share on other sites More sharing options...
RoyC Posted June 17, 2011 Report Share Posted June 17, 2011 The spider I used wasn't too bad. The foam on the new cone was thicker than my 'stand alone' BA foams. Next time I'll strip the foam from the cone (they come pre-assembled) and use a stand alone one. Maybe that will lower Fs a bit.The old refoam data point is the only one I could find. Is that normal? I don't know.I've measured the fs of quite a few cloth surround AR 8 inchers of the 60's and 70's, and the vast majority of them were around 35hz. Until we found the high compliance JBL and Boston FF surrounds, the typical replacement foam surrounds sold by Ebay's "Vintage AR" (who has recently switched to the JBL surround), and others, could easily kick the fs up 10hz or more. This is also true of the 10 inch AR woofers, which should have fs of 25 to 30hz. Since you were using the very compliant Boston FF surround, I'm thinking your spider is the culprit. Fs of the foam surround AR woofers was very consistent with their cloth surround counterparts, but Q appears to have varied.Roy Link to comment Share on other sites More sharing options...
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