Guest ghstudio Posted April 18, 2004 Report Share Posted April 18, 2004 Just refoaming my woofers and then I'll start replacing my pots and changing polarity on midrange. I removed the old fiberglass and really would rather throw it out then work with that stuff. Is there a modern replacement product that will work just as well? Link to comment Share on other sites More sharing options...
ninohernes Posted April 18, 2004 Report Share Posted April 18, 2004 The original stuff works the best, but if you want to replace it, Acousta-Stuf works very well. http://www.partsexpress.com/pe/showdetl.cf...tnumber=260-317Also, I wouldent change the polarity on the midrange, it really messes up the sound. It gets muddy in the lower midrange, and upper midrange will sound "honky". The system really sounds best with its original crossover. You can try it, but you will end up going back to the original Link to comment Share on other sites More sharing options...
stan461 Posted May 9, 2004 Report Share Posted May 9, 2004 Ninohernes,I have "Acousta-stuffed" my AR3as and was wondering how much by weight did you use? The original stuffing was 1 lb. 12 oz. to about 1 lb. 14 oz. I should know, I have 4 of them and have removed and weighed all the stuffing.According to Acousta-stuf literature, you should use 1/2 lb. per cubic foot. The interior of the AR3a is about 1 3/4 cubic foot which means 14 oz. of stuffing. Thats what I used.I will play around with the stuffing if I have to in order to get it right but I just can't bring myself to go back to fiberglass. Not yet anyway. Link to comment Share on other sites More sharing options...
soundminded Posted May 9, 2004 Report Share Posted May 9, 2004 I will repeat my thoughts on my previous post on this subject. IMO, the amount, distribution, and density of the fiberglass is inherent in the performance of the woofer. The woofer is forced to overcome the aerodynamic drag created by pulling and pushing air through the spaces between the fibers. This controls the speaker's mechanical damping factor. It also controls the effective air volume inside the box since the space taken up by the fibers themselves displaces air and changes the overall spring constant. While this may not have been scientifically explored to the same degree as the woofer design or the crossover design (I don't know one way or the other, perhaps Tom or Ken can comment), the optimal amount was determined by the manufacturer possibly through experimentation. By changing the type or amount, you will likely change the bass response. That doesn't mean you can't achieve equivalent results but it would require experimentation with the new material which can also be a nuissance. The hit or miss approach will almost surely yield a miss. I'm just pointing this out so that if you do make a change and get different results, you would have at least a good guess as to why it happened. Link to comment Share on other sites More sharing options...
roundhome Posted May 10, 2004 Report Share Posted May 10, 2004 On the fiberglass stuffing. it is denser but it is put in in chunks and the air would take the least path of resistance. and flow around the chuncks first. I understand the concept it is to provide. if it was evenly distributed. why can't we set up a flow test chamber using a given cfm of air flow stuff it with the glass and check the flow them stuff it with the new stuff until the same flow is reached. this could be set up easy with a flow tube . the idea is to come up with the same resistance to the air flow as the glass. the new stuff has a more even distribution inside the box. and would be more consistent in air flow. the chunks of glass would have to be put in the cabinet vary carefully to get the same air flow consistency.I have the glass from a pair of threes and the flow meters if this sounds like something that would work and i'm even in the ball park in my thought . I could set it up and test it I also have the stuffing from a LST II.tell me if i'm out to lunch on this and I will understand.Jim Link to comment Share on other sites More sharing options...
soundminded Posted May 11, 2004 Report Share Posted May 11, 2004 I have a hunch that the original design decision was made by trial and error. Not having been there and not knowing, I'd bet they took the same size box and stuffed it with different amounts of the fiberglass they intended to use and measured the frequency response of each until they got the best compromise of damping factor and in box resonance frequency. The in box resonance is supposed to be 42 hz and it IS affected by both the remaining air volume in the box which controls K in Newton's second law and the aerodynamic drag which controls B. The relationship can be found in any college physics text for giving the resonance frequency and damping factor relating M (mass) B (usually called viscosity) and K (spring constant). Look for the solution for the special case of forced resonance. It hit me 15 years ago that this was an exact mathematical model and I thought I had really discovered something. Then I started reading Sam's Audio Reference Handbook and I saw that the people who developed mathematical models were way ahead of me. However, If you can understand Newtons second law, you will also understand exactly how every woofer/enclosure works at least mechanically. There are no secrets and there is no magic to it. Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.