Mid base enclosure volume

[idris]

How do you vary Qtc?

[lynx]

Try a program like bass box pro.

[Ayub]

http://www.bcae1.com/spboxnew2.htm

[idris]

Yep seen those, but BCAE asks you to input Qtc in order to calculate the required enclosure vloume. But it doesn't tell you what you need to do to the design to change the Qtc.
Obviously if you vary the volume, you vary the Qtc. But I want a flat reponse so I need to aim for Qtc=0.707

I'm using Focus 100v mid-bass drivers as an exmaple for ball-park calculations but if I use the BCAE speaker calculator and specify Qtc=0.707, it says ERROR:The selected Qtc is too low for the selected woofer's Qts. Surely that means it's impossible to get a flat response no matter what size enclosure you build?

[avanzato]

What's the Qts of the driver?

Is it the Focal 100V slim you're using? If it is that driver has a Qts of .811 IIRC you can't have a Qtc that is lower than the drivers Qts.

Try plugging the TS numbers into a programme like WinISD and see what variations you can come up with.

[idris]

Originally Posted by avanzato

If it is that driver has a Qts of .811 IIRC you can't have a Qtc that is lower than the drivers Qts.

And there lies my problem.

The spec sheet does say Qts=0.811
And the maths / calculators confirms that you need Qtc > Qts
But with this figure, how do you optimise the enclosure for a flat respose?

I've not actually bought the speakers, I just picked them because they were the only 4" components I could find the TS figures for on the net. I figured they'd be "typical" & just use them as a starting point. Are there any 4" mids that'll allow me to make a tiny enclosure and have a flat reponse?

[micb3rd]

For midbass speakers you don't often need a Qtc of 0.707 in car as there is so much cabin gain in the vehicle that response still can extend nicely.

Also sometimes if you are wanting to play a higher output levels a slightly raised Q can be better for the drivers mechanical handling.

The majority of decent car audio systems use subwoofers for the lower octave so extreme extention may not be required from the midbass units.