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I've worked through every thread I could find here without really finding what I was looking for. My issue is with a too small enclosure volume for a dedicated midrange. I have a pair of Fountek FR88EX 3" which I'm putting in a pillars. Optimal Qtc 0,707 have an enclosure volume of 4,1 litre (0,145ft^3) since they have a pretty high Qts (0,65) to begin with. Madisound suggests a speaker volume of 0,5 litre (0,018ft^3) which is closer to the actual space I got, but it would also raise Qtc to somewhere close to 0,95.

As far as I understand, transistant response is connected to Qtc and not frequency response? So no matter how flat I EQ the frequency response, all the negative aspects with the higher Qtc remain?

Another statement I've heard is that Qtc doesn't matter much and that is the reflected backwaves that is the issue. Won't polyfill take care of that? Damping materials should be pretty effective in the midrange area.

Will high Qtc affect more than the area just around Fsc? I plan to cross them [email protected] HP while Fsc is at 180Hz with this smaller enclosure, will there be audible distortion running a small midrange speaker through Fsc. In subwoofer sealed designs, Fsc doesn't seem to matter much though.

Finally, I have good tuning possibilities. I run 4-way active through Pioneer P99RS. 8" Mids low in doors, tweeters in sail-panels. Just my a-pillars left...
 

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I've worked through every thread I could find here without really finding what I was looking for. My issue is with a too small enclosure volume for a dedicated midrange. I have a pair of Fountek FR88EX 3" which I'm putting in a pillars. Optimal Qtc 0,707 have an enclosure volume of 4,1 litre (0,145ft^3) since they have a pretty high Qts (0,65) to begin with. Madisound suggests a speaker volume of 0,5 litre (0,018ft^3) which is closer to the actual space I got, but it would also raise Qtc to somewhere close to 0,95.

As far as I understand, transistant response is connected to Qtc and not frequency response? So no matter how flat I EQ the frequency response, all the negative aspects with the higher Qtc remain?

Another statement I've heard is that Qtc doesn't matter much and that is the reflected backwaves that is the issue. Won't polyfill take care of that? Damping materials should be pretty effective in the midrange area.
That's incorrect. Transient response and frequency response are connected. There isn't anything magical about a QTC of 0.707; it's the frequency response of that alignment which leads to good transient response.

And YES, flattening the response DOES improve the transient response.

Long story short - if you have an EQ, you can equalize the response of a box that's too small so that it sounds like a bigger box.

You can experiment with this pretty easily. For instance, take a speaker which measures pretty well. A speaker that you know is close to flat. Now apply a bunch of EQ in the bass. Does it sound boomy and slow now? That's because you just screwed up the transient response.

There's a speaker on the westhost site that uses this to a neat effect - it's basically a box with way too much bass, which they run a low pass filter to reduce the bass and flatten the frequency response and improve the transient response. It's a cool effect because you get improved power handling AND a very small box. Also, google 'Linkwitz Transform.' Somewhat similar idea.
 

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Here's a WinISD simulation. Both graphs are a FR88EX in a 0.5 L box (Qtc = 0.96) @ 20W. The red graph is no filter and the yellow graph has a LR 24 dB/oct highpass @ 200 Hz. Looks pretty flat to me!

Note: I'm using the FR88EX T/S parameters from Zaph's site so I'm confident with their values.

Ed Perkins
 

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Any more input on this? Im using Vifa PL11 on a very small A pillar enclosure too...any particular EQ i should boost? And where should i cross it?
 
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