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Old 15th November 2010, 04:05 PM   #1
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Default Hopefully a simple question

(Quote from the noob section) All right. I'm going to get a bit technical, so hang in there with me. The first thing most often considered in a design is the box and bass alignment. The two most common bass alignments for woofers are vented and sealed, but transmission lines, horns, infinite baffles, and dipoles can sometimes be an option as well. However, every woofer is usually best suited for only one of those applications. To figure out which one, we examine its electrical and mechanical strength (Qes and Qms), and come up with a figure called its Qts, which, depending on its value will tell the designer which bass alignment will work the best. Next, we need to know the equivalent air volume (Vas) of the driver. Using this number in conjunction with the Qts and the drivers' resonant frequency (Fs), we can start designing appropriate cabinets and alignments to get the proper bass response from a driver. Getting this step wrong means that the speaker's bass will either be way too weak, or overbearing and boomy... neither of which is fun to listen to.Q: Can't you just get the best bass from a big woofer, and just sort of add stuffing or fiberglass until it sounds right?
A: It's a common misconception that a "huge" woofer is gonna make super-deep, visceral bass. Actually, the point of having a woofer with a lot of surface area is to increase its Sound Pressure Level. You'd be surprised; an 8" or 10" woofer can easily extend down to the bottom range of human hearing (20 Hz or lower), when it's in the properly tuned enclosure. Now please, pay attention. We still haven't gotten past step #1.

So, now that we have a general idea of our box volume, we can start considering how we want the cabinet to look and where we might want to arrange the drivers on the baffle. A lot of beginners (myself included, once upon a time) think you can just fenestrate drivers anywhere on the baffle, so long as it looks cool. Visions of rows of tweeters and midranges are sketched up--and often shot down by the DIY community.



Heres my question/s How do I calculate the proper bass alignment and box volume for my Altec Lansing 604 Duplex speakers?
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Old 15th November 2010, 04:14 PM   #2
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You've already given the answer in your preamble - find Qts, VAS and Fs. Then use modelling software. There are published alignments that are good for starting points, but if you read up on what group delay is you should be able to come up with something reasonable yourself. Just keep one eye on the frequency response curve and the other on the excursion curve and thermal power curve.
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Last edited by richie00boy; 15th November 2010 at 04:18 PM.
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Old 15th November 2010, 06:31 PM   #3
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cradeldorg,

First I Agree with richie00boy.You almost answered our own question.
See one (quick) example on how to continue using HR (Hornresponse):

b
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Last edited by bjorno; 15th November 2010 at 06:39 PM.
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Old 15th November 2010, 08:27 PM   #4
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Impedance varies with frequency, use impedance plots of your drivers and make crossover calculations using the actual impedance of the driver at the crossover frequency
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