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I've heard .707 and also .5, which is quite a wide range. Do you base your sealed enclosure volume on QTC and what is the best QTC to have? Is it important?
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Sharp LC-42D64U
TriTrix MTM (Sealed) -
0.707 = maximally flat
0.50 = critically damped.
The effects of room gain has the potential to make 0.707 a little boomy. So my personal preference is for 0.50.
YMMV....
IB subwoofer FAQ page
"Complicated equipment and light reflectors and various other items of hardware are enough, to my mind, to prevent the birdie from coming out." ...... Henri Cartier-Bresson -
Use Unibox (from FRD consortium) to get a feel for what happens to the impulse response with different enclosure alignments. This will help you see the difference between sealed box Q, vented, PR and bandpass enclosures.Comment
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It's really about personal taste.Comment
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The elephant in the room is, errrr.... the room with its 20dB peaks and valleys added to the response.
Your final system Q will be determined by the box + the driver + the room + any EQ you use. Almost any sealed sub needs EQ to boost the low end and knock down some room modes. Just build the biggest box you can handle in your room and EQ it flat. Don't sweat the theoretical anechoic Q too much unless you live in an anechoic chamber. You can set the final Q to whatever you want with EQ. Q is just fancy engineer speak for the shape of the frequency response curve at the bottom end and EQ can easily change that.
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I'll just add that optimum box Q is affected by the additional series resistance from the amplifier source impedance, cable impedance, DCR of the crossover network, and the effects of voice coil heating. All these are accumulative, and raise the system Q.
Take for example, the RS180-4. In 12 ltrs sealed its Qtc is .705, assuming a series resistance of 0.1 ohm. Change this to 0.7 ohms however, and the system Q jumps to .806.
OTOH, if one starts off with a modeled Qtc of .6, the resultant box Q is .688 when the additional 0.6 ohms is factored in.
CComment
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Interesting. The only 'EQ' I have right now is that which is built in to my receiver. What types of products, or perhaps specific products if that is allowed, would you guys recommend for an EQ?Sharp LC-42D64U
TriTrix MTM (Sealed)Comment
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Digital parametric is most flexible/accurate.
IB subwoofer FAQ page
"Complicated equipment and light reflectors and various other items of hardware are enough, to my mind, to prevent the birdie from coming out." ...... Henri Cartier-BressonComment
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