Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ.

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Re: ok, but...

206.101.70.198

Posted by hZ on May 6, 1999 at 19:32:58

In Reply to: Re: ok, but... posted by Lukasz F. on May 6, 1999 at 10:49:34:

=> First, I am curious about the idea of the aperiodic vents. Please, explain why and how.

I'm assuming by your question that you're not familiar with aperiodic damping. If you are, I apologize. Aperiodic damping is placing a resistive leak (piece of fiberglass sandwiched between two grills) in a sealed box. This basically ads "shocks" to the air "spring" of the enclosure. It damps the system's resonance peak (fc) considerably, giving the amplifier better control. It also improves transients, creating tigher response. It is very similar in effect to properly using 100% fill in a box. I've been very curious as to what, if any, benefits might be gained by using an aperiodic chamber "inside" (or firing into) a sealed or second aperiodic chamber (Dynaudio's Aries appears to do the aperiodic firing into sealed technique).

=> BTW - what are you building? Just curious.

I'm just designing at this point; it'll be a few (mabye several) months before I can afford to build this. What I'm going for is a two way sealed (aperiodic) "bookshelf" speaker to be used with a powered aperiodic sub (Madisound 1252DVC in 91 liters, two aperio-vents, Parapix amp). My concerns are transparency/neutrality, smooth frequency response, transient accuracy, dynamic ability, and good dispersion/imaging... pretty much in that order. I guess I'm really wanting it all, and on a budget ($400-$500 max)... though neutral sound and transient accuracy are my main concerns... and I refuse to compromise on smooth response. I've pretty well settled on the Seas H881 textile tweeter, crossed over at 2k, mabye as high as 3k (use of a felt diffraction ring is a given). Response must have an f3 below 80 Hz (60 is what I'd like).

=> As concerning the drivers in series - you will have a coil of one driver in series with the XO for the second driver. Plus you will have the voltage generated by the moving coil injected back into the circuit of the second driver. This explains for me that it is a no-no.

I'd build one crossover treating the coils in series as one coil, adding Re, Z, and Le for calcuations. I'm mainly wanting to know if in fact Qes is halved for drivers in series, as this will affect Qts, which will affect computing Vb. I don't have an expert's grasp of back-EMF, but isn't that already a problem in single drivers? I've heard completely different loudspeakers running in series and I heard nothing terribly horrible... just some FR changes I've attributed to different impedances interacting.

Well... now time to read Richard's response... see if he can turn me off to the idea of drivers in series. hehe

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