Guest SteveG Posted April 22, 2004 Report Share Posted April 22, 2004 Tom,In the post "2ax tweeter swap", you said that a 2ax should have 1.3 to 1.5 pounds of fiberglass in the enclosure. How much should a 3a have???ThanksSteveG Link to comment Share on other sites More sharing options...
stan461 Posted April 22, 2004 Report Share Posted April 22, 2004 Just like to tap Tom's knowledge and also jump in here.I have emptied and weighed 4 AR3a's and each had 1 lb. and 12 oz. to 1 lb. 14 oz. of stuffing. My question for Tom (or anyone else) is:Has anyone tried Acousta Stuf and would it warrant the same amount of stuffing?I have tried it and I can't hear any difference. I think that the bass would be where any change would be audible. Link to comment Share on other sites More sharing options...
johnieo Posted April 22, 2004 Report Share Posted April 22, 2004 My two AR3a contained 1 lb-11.2 oz and 1 lb-14.5 oz, respectively. Somewhere on some AR document, I saw a statement saying 1 lb fiberglass per cubic foot of speaker volume for the correct Q. If so, then 1.7 cf becomes 1 lb-11.2 oz. ...For what it's worth; sounds like we are all measuring about the same weight. Link to comment Share on other sites More sharing options...
tysontom Posted April 22, 2004 Report Share Posted April 22, 2004 >Just like to tap Tom's knowledge and also jump in here.>>I have emptied and weighed 4 AR3a's and each had 1 lb. and 12>oz. to 1 lb. 14 oz. of stuffing. >>My question for Tom (or anyone else) is:>>Has anyone tried Acousta Stuf and would it warrant the same>amount of stuffing?>>I have tried it and I can't hear any difference. I think that>the bass would be where any change would be audible. >>Ken could tell us about Acousta Stuf or other synthetic stuffing; I'm sure it works fine. Fiberglass is a known-quantity, however, so the weight and the damping properties are well-established variables in the case of the AR speakers. It might take more or possibly less Acousta Stuf than fiberglass due to any difference in density, absorption, etc.--Tom Tyson Link to comment Share on other sites More sharing options...
tysontom Posted April 22, 2004 Report Share Posted April 22, 2004 >My two AR3a contained 1 lb-11.2 oz and 1 lb-14.5 oz,>respectively. Somewhere on some AR document, I saw a>statement saying 1 lb fiberglass per cubic foot of speaker>volume for the correct Q. If so, then 1.7 cf becomes 1>lb-11.2 oz. ...For what it's worth; sounds like we are all>measuring about the same weight.--Tom TysonJohn,I agree with you that we are all on the same page here. A few ounces one way or the other probably will make less difference than by moving the speaker a few feet this way or that. The problem comes in, of course, when the original fiberglass is removed and replaced with a given *amount* of synthetic stuffing, and the damping properties of it are somewhat different probably by weight, thus affecting the Q of the speaker. The correct weight of fiberglass is already known in AR speakers, and it is vital to proper damping and uniform response, especially down around resonance. Synthetic material would do fine, I am sure, but it's hard to know the specific properties of it by weight without doing speaker measurements.--Tom Tyson Link to comment Share on other sites More sharing options...
Guest SteveG Posted April 23, 2004 Report Share Posted April 23, 2004 Thanks to all for the excellent and quite uniform responses. Sounds like standard fiberglass house insulation is the way to go. Not pleasant stuff, but a known quantity.SteveG Link to comment Share on other sites More sharing options...
Guest SteveG Posted April 23, 2004 Report Share Posted April 23, 2004 Thanks to all for the excellent and quite uniform responses. Sounds like standard fiberglass house insulation is the way to go. Not pleasant stuff, but a known quantity.SteveG Link to comment Share on other sites More sharing options...
soundminded Posted April 23, 2004 Report Share Posted April 23, 2004 The density of the fiberglass, the amount, and its distribution is critical to the tuning of the woofer/enclosure system response. It is inherent in the system. This is because as the woofer cone moves in and out, during the compression/rarifacton of the air inside the enclosure, the velocity related drag controls the damping factor. This is the frictional drag of the air as it moves back and forth through the spaces created by the fibers. According to Newton's second law of motion, the motional response of an object is related to the mass (M), the spring constant (K) and the velocity related drag coefficient ( in the equation F(t) = M*acceleration + B*velocity + K*displacement. The equation and its solution for the case of forced resonance which is the case for any loudspeaker mechanism is given in every standard college physics text book. It relates these three variables to the resonant frequency and the resonance peak (Q). In principle, any loudspeaker driver could be tuned to have any resonance frequency and Q by adjusting M, B, and K. That is why small diameter acoustic suspension speakers could be tuned to very low frequencies. The ingenuity of the acoustic suspension principle is that K is no longer a function of frequency because the mechanical suspension is very loose but instead obeys the ideal gas laws which are completely linear for small changes in volume P1V1=P2V2. It also eliminates the resonant peaks and anti resonant dips that occur with tuned bass reflex type enclosures. Link to comment Share on other sites More sharing options...
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