Guest Pointwhere Posted July 12, 2004 Report Share Posted July 12, 2004 Hello guys...I recently bought a used pair of AR303 speakers, only they had been "converted" to 303a's by the original owner's installation of the 303a crossover. The speakers have some definite internal resonances, and can sound boomy during some types of music. I downloaded a shareware test tone generator software, and after playing around with it a bit I have concluded that there are strong resonances around 150hz and around 45hz. It doesn't make sense to me that then new crossover would cause this, since all the drivers and cabinet are the same in the 303 and 303a, is there something I am mising here?Is this boominess natural for a 303? I assume not, since the speaker is so highly regarded. What might be causing this problem? It is not the listening room, I took the speakers outdoors to test and the resonances persisted. I can feel vibrations through the walls of the speaker cabinet at those frequencies. I opened the speakers up by unscrewing the woofers, and the material inside is a cotton-like fill; different from the fiberglass used in the vintage models. Is this the factory fill for this speaker? If everything is correct about the speaker's configuration, is there any way I could kill these resonances by using more/different fill, bracing, or other techniques? I would really appreciate any advise anyone may have, this issue has been driving me nuts to the point where I am fruitlessly researching it online when I'm supposed to be accomplishing things at work Thanks for any help. Link to comment Share on other sites More sharing options...
ninohernes Posted July 12, 2004 Report Share Posted July 12, 2004 This speaker should not be boomy. Boomy sound is caused by not enough internal dampining. When the crossover was upgraded, the owner probably did not replace all of the fiberglass stuffing on the inside, and if he did, he did not distribute it evenly. I would open up the cabinent, and make sure that the stuffing is easily distributed. I forget exactly how much stuffing this model uses. Tom can probably answer that. Link to comment Share on other sites More sharing options...
Guest Pointwhere Posted July 12, 2004 Report Share Posted July 12, 2004 Ok, I opened up both speakers, and removed half the stuffing (not fiberglass, some sort of cotton stuff) from one and put it into the other. The one with less stuffing sounds noticeably worse than before, but the one with 1.5x the original stuffing amount still has the same resonance peaks as my original. Any other ideas? Link to comment Share on other sites More sharing options...
ninohernes Posted July 12, 2004 Report Share Posted July 12, 2004 Interesting problem. I am afraid I cant help you any more. I am sorry that I made you open up both cabinents, I know that it is a pain! But I really thought that the stuffing was the problem. I had a similar boominess issue with a pair of AR-3's, and adding stuffing fixed the problem. Link to comment Share on other sites More sharing options...
Guest Pointwhere Posted July 13, 2004 Report Share Posted July 13, 2004 Does anyone know how the stuffing should be installed? Even density, pack as tight as possible, make sure it gets in the corners... Do any of these things matter, and are they good, or bad? DOes anyone else with 303s have this problem? I'm a newbie, thanks for the help. Link to comment Share on other sites More sharing options...
ninohernes Posted July 13, 2004 Report Share Posted July 13, 2004 Tom, Ken, where are you...(They will be able to help you!) Link to comment Share on other sites More sharing options...
Rlowe Posted July 13, 2004 Report Share Posted July 13, 2004 Could this possible be room resonances? What size room are you listening to them in (length and width and height) and where are you seated when you're listening to them? Link to comment Share on other sites More sharing options...
Guest dogmeninreno Posted July 13, 2004 Report Share Posted July 13, 2004 >Ok, I opened up both speakers, and removed half the stuffing>(not fiberglass, some sort of cotton stuff) from one and put>it into the other. The one with less stuffing sounds>noticeably worse than before, but the one with 1.5x the>original stuffing amount still has the same resonance peaks as>my original. Any other ideas?This might help? I would bet on an air leak. Are your dustcaps perhaps vented? Dale http://www.arsenal.net/dc/dcboard.php?az=s...ing_type=search Link to comment Share on other sites More sharing options...
Guest Pointwhere Posted July 13, 2004 Report Share Posted July 13, 2004 It's not room resonances, since I tested it in 2 different rooms and also outdoors and the resonances persisted. As far as vented dust caps, how do I tell? They look nice and new to me, no visible cracks or anything like that... The only other place I can imagine an air leak is around the drivers or crossover, but my instinct (newbie instinct mind you) tells me that since the resonances are the same in both speakers, this is probably not the problem. I will try taking the drivers off and making sure they have good seal around them though, to see if it helps. BTW, does anyone know if the cotton stuffing material is supposed to be inside these speakers? If the stuffing is not original, that might be my problem. Thanks for the help. Link to comment Share on other sites More sharing options...
rrcrain Posted July 13, 2004 Report Share Posted July 13, 2004 What are the differences between a 303 and a 303A crossover? My first guess would be to start looking here first and try to figure out of the conversion is to blame, or perhaps was done incorrectly. Link to comment Share on other sites More sharing options...
ninohernes Posted July 13, 2004 Report Share Posted July 13, 2004 >>BTW, does anyone know if the cotton stuffing material is supposed >>to be inside these speakers? If the stuffing is not original, that >>might be my problem. Thanks for the help.The stuffing is supposed to be there, I just cant remember how much. And yes, the cotton like stuff is original. Link to comment Share on other sites More sharing options...
Guest chet helms Posted July 13, 2004 Report Share Posted July 13, 2004 The AR 303 was packed with some sort of fiber (poly? acoustastuf?)fill--not fiber glass. It was packed tight--so tight that you would be hard pressed to pack any more in. A hole was dug out in the fill for the woofer. Having said that I have no ides what your problem might be. If you had the equipment (or a friend) to run an impedance sweep in the bass that would help tremendously. Chet Link to comment Share on other sites More sharing options...
Guest Pointwhere Posted July 14, 2004 Report Share Posted July 14, 2004 I am considering putting acousta-stuf, black hole, or some other resonance-killing material in the speakers, to see if there is a change. Would anyone recommend for or against this? What types of material might work?As far as doing an impedence sweep, I don't have any equipment but will ask around locally to see if someone can do it for me. Thanks for the tip. Link to comment Share on other sites More sharing options...
Guest Pointwhere Posted July 15, 2004 Report Share Posted July 15, 2004 Can anyone please post or direct me to some graphs of frequency response and frequency vs. impedence for the AR-303 speaker? I want to see what the curves look like for a speaker that is working properly. Thanks. Link to comment Share on other sites More sharing options...
tysontom Posted July 15, 2004 Report Share Posted July 15, 2004 >I recently bought a used pair of AR303 speakers, only they had>been "converted" to 303a's by the original owner's>installation of the 303a crossover. The speakers have some>definite internal resonances, and can sound boomy during some>types of music. I downloaded a shareware test tone generator>software, and after playing around with it a bit I have>concluded that there are strong resonances around 150hz and>around 45hz. It doesn't make sense to me that then new>crossover would cause this, since all the drivers and cabinet>are the same in the 303 and 303a, is there something I am>mising here?>To my knowledge there is little difference, other than the bi-wiring capability and cabinet finish, between the AR-303 and the AR-303a. Both speaker systems use exactly the same drivers and cabinet size, etc. The crossover components are the same except for the wiring, I believe, and only minor differences if that. What you describe sounds a lot like a speaker-placement or room-resonance problem. Improperly re-installed drivers, or something of that nature, could also contribute to the problem. Remember, too, that the 303 has *very* strong low-bass output, and the placement of the speaker is somewhat critical. Anything close to the floor, in a corner or along a short wall in a long, narrow room would tend to amplify low-frequency nodes and resonances in a big way. Be sure that the speaker is up off the floor by at least 12-18 inches or more, and out of a corner.>Is this boominess natural for a 303? I assume not, since the>speaker is so highly regarded. What might be causing this>problem? It is not the listening room, I took the speakers>outdoors to test and the resonances persisted. I can feel>vibrations through the walls of the speaker cabinet at those>frequencies. I opened the speakers up by unscrewing the>woofers, and the material inside is a cotton-like fill;>different from the fiberglass used in the vintage models. Is>this the factory fill for this speaker? >The AR-303 and 303a could not be characterized as being boomy by any standard. The low bass is very present, and can excite room nodes easily, but the speaker itself is not boomy ever. Certainly testing or measuring outdoors you would not notice room nodes or characteristics, but be sure to mount the speaker carefully when in the listening environment. Make sure the speaker does not have air leaks, and make sure all components on the crossover are connected correctly to the drivers, etc. The 303 actually has a small intentional rise in output around 50 Hz or so, but this small increase in output is not noticeable as boominess (which implies "ringing" or hangover in the response of the driver), but gives the speaker a somewhat warmer sound than an equivalent AR-3a around the same frequency. Be expecially careful to insure that there is no resistance in the speaker-output circuit, and that the damping factor on the amplifier output is not somehow at 1 or below, which could happen on some of the older tube amplifiers. Newer solid-state amps don't usually have this capability. Be sure that the speaker wire is not excessively long or of too-small size for the distance with regard to the 303's 6-ohm impedance.>If everything is correct about the speaker's configuration, is>there any way I could kill these resonances by using>more/different fill, bracing, or other techniques? I would>really appreciate any advise anyone may have, this issue has>been driving me nuts to the point where I am fruitlessly>researching it online when I'm supposed to be accomplishing>things at work Thanks for any help.There is absolutely no reason to think that you should have to brace the cabinet or add damping to the 303. It already has 1-inch MDF panels, I believe, and it should be relatively acoustically "dead." It was designed properly to begin with, and unless someone has altered it, which might have happened in this case, no changes should be attempted.--Tom Tyson Link to comment Share on other sites More sharing options...
Guest chet helms Posted July 15, 2004 Report Share Posted July 15, 2004 Impedance curve and freq. response attached. Some minor jiggles in the curves but you an see what they're supposed to look like. Note the resonance of this woofer is around 37 Hz when the spec is (I think) around 41 Hz. Chet Link to comment Share on other sites More sharing options...
Guest Pointwhere Posted July 15, 2004 Report Share Posted July 15, 2004 Hmmm... Assuming nothing is wrong with the speaker wiring and that no modifications have been made, it sounds like air leaks or driver installation are the most likely culprits. Could anyone please let me know how to detect/correct air leaks or poorly installed drivers? My driver installation techniques were kinda simple, I put the driver in the hole and screwed it down with the original screws, quite tight. Please let me know if anyone can think of a way to improve this. Link to comment Share on other sites More sharing options...
Guest chet helms Posted July 15, 2004 Report Share Posted July 15, 2004 OBTW, in the curves above the woofer freq. response is close miced--about 1/4" from the dust cap. Just in case there is confusion. Chet Link to comment Share on other sites More sharing options...
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