Guest Sweden Posted August 23, 2004 Report Share Posted August 23, 2004 Hello all,As some of the members of this board recalls, I bought a pair of AR91 that had some "problems". I could write off all "problems" except one, the somewhat "weak" bass. I must stress before I continue that the bass is not weak, but I feel that it could delivers more. I get quite a good output but I have to alter the bass-level on the amp to 3 o' clock to get good bass and I especially feel the bass when I'm sitting in the couch, not so much when standing up. Here I also must stress that my listening room is very limited (appr 5 times 4 meters or so). The speakers are placed 20 centimeters from the wall. They are directed straight forward.When I bought the speakers the previous owner told me something that has been stored on the "back-up server" until some days ago. He told me that he had to remove some of the stuffing inside the speakers due to that the bass was to pronounced. So the obvious questions now are:- How much will the amount of glass-fiber in the speakers affect the output on the lower freq's? (I don't know how much fiber that has been removed)- When replacing, will any fiber do or should I buy a special kind?- How will the "restoring" to original state affect the mid and high-range. My wife and I are satisfied with these freq's (we have set the switches to high on both selectors on the back of the speakers)- Will spikes make any difference?I gear the speakers with a DENON PMA2000R, which is a powerful integrated amp that produces appr 140 ampère.ThanksRickard Link to comment Share on other sites More sharing options...
soundminded Posted August 23, 2004 Report Share Posted August 23, 2004 The stuffing inside is critical. It's amount, type (density) and distribution will affect bass performance. Here's why. (I often wondered about this myself and it wasn't until a few years ago that the answer dawned on me.) There are three important inter-related factors which affect bass performance in an acoustic suspension speaker. The moving mass which is the mass of the cone/voice coil assembly, the springiness of the air trapped inside the box (smaller boxes will make the air more springy) combined with the springness of the woofer itself, and the aerodynamic drag of whatever the woofer cone has to pull and push the air through, in this case the small spaces between the stuffing fibers. This is where the stuffing comes in. It is a damping material controlling this aerodynamic drag the woofer has to work against. To much stuffing and the woofer is over damped making it too difficult to overcome the drag reducing bass. Too little and there won't be enough drag allowing the speaker to resonate spuriously at it's resonant frequency. This resonant peak in the frequency response is not musically useful or accurate. Trying to adjust the bass response of an fine acoustic suspension speaker yourself by altering the stuffing IMO was a bad mistake. It was carefully determined for optimal performance at the factory. Tom or Ken said at one point I think that it was about one pound or slightly less per cubic foot of enclosure. The other thing to look for if the bass is weak is an air leak. The cabinet must be air tight. If the driver was removed, when it was replaced the seal may no longer be tight. Also look for any deterioration of the cone or surround which might cause an air leak. Look at the seal around the other drivers too if they are not in a sub-enclosure. Link to comment Share on other sites More sharing options...
Guest Nigel Posted August 23, 2004 Report Share Posted August 23, 2004 The other thing is that 20 cm (8 inches) is a LONG way from the wall for optimum bass response from an AR91 (or any other AR9 series speaker). Link to comment Share on other sites More sharing options...
Guest Sweden Posted August 23, 2004 Report Share Posted August 23, 2004 OK Nigel, thanks for your input. They goes in line with what I have thought myself (i.e. dampening factor).(Just a point, I wasn't the one who removed the stuffing. It was the guy that sold them to me.)I have checked the speakers and they seem air-tight. As I said in the previous thread, the speakers are in an excellent condition for their age.Anyway, I will start with moving the speakers closer to the wall (appr 5 cm).In september, I will open the speakers and see how the stuffing looks like. I have my AR6 as a reference I guess.ThanksRickard Link to comment Share on other sites More sharing options...
soundminded Posted August 23, 2004 Report Share Posted August 23, 2004 It seems counterintuitive that removing stuffing would reduce bass. I would have expected it to increase. Link to comment Share on other sites More sharing options...
Guest Sweden Posted August 24, 2004 Report Share Posted August 24, 2004 Sorry Nigel, I mixed your message up with Soundminded.I moved the speakers closer to the wall and I experienced a slightly better bass-performance so thanks for the advice! Link to comment Share on other sites More sharing options...
Guest Sweden Posted August 24, 2004 Report Share Posted August 24, 2004 >It seems counterintuitive that removing stuffing would reduce>bass. I would have expected it to increase.The seller said to me that removing some fibers, lessened the bass. Perhaps that coloured my intuitivity?No one has given me some input on my other 2 questions:- Spikes, what will they do to a pair of AR91?- What will happen to the mid and highrange if I put in some fibers (nothing I would guess)?ThanksRickard Link to comment Share on other sites More sharing options...
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