qtc

[blowsoot 10+ year member]

whats the magic number to aim for in a sealed box to get best all around bass that blends good? .707 correct? louder you would want higher towards 1.5 ? I think im in the .670's now... the sub really doesn't hit that hard and sounds shitty. Would that be because my enclosure is larger? Now im gonna try AIMing for .730 now to see what happens. makes my box from .62 down to .45

Click to read more...

 

[Jordantyler 10+ year member]

what sub do u have?

 

[96civ 10+ year member]

Anywhere between .707 and 1.000 is a good range I think. My L5 is .9 and it handles well. If you get it too much lower than .707 you'll get boomy bass. Put some polyfill in the box to decrease the internal volume, that might help.

 

[blowsoot 10+ year member]

im like .670 and the sub is not loud at all and sounds bad like weird sounding. Building new box should be around .740's. Diamond M6 sub

 

[squeak9798 5,000+ posts]

Anywhere between .707 and 1.000 is a good range I think. My L5 is .9 and it handles well. If you get it too much lower than .707 you'll get boomy bass.

That "boomy" sound is an increase in low frequency sensitivity and output over the higher Qtc enclosures //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif Not to mention an increase in transient response, group delay, etc etc. Main downside is an overall decrease in output.

But....many, many, many people enjoy a lower Qtc, in the .577 (bessel) and .5 range. Especially the "audiophile" type crowd.

Put some polyfill in the box to decrease the internal volume, that might help.

Polyfill has the opposite effect. It will make the sub behave as if it's in a larger enclosure, not smaller. Hence lowering the Qtc, not raising it.

 

[blowsoot 10+ year member]

does everyone use polyfill in a sealed box?

 

[squeak9798 5,000+ posts]

does everyone use polyfill in a sealed box?

No.

Not really needed if you build the box to proper size. But it's something that can be played with if desired.

 

[96civ 10+ year member]

Polyfill has the opposite effect. It will make the sub behave as if it's in a larger enclosure, not smaller. Hence lowering the Qtc, not raising it.

So even though the internal volume is decreasing, the sub sounds like the volume has been increased? //content.invisioncic.com/y282845/emoticons/uhoh.gif.c07307dd22ee7e63e22fc8e9c614d1fd.gif .. does that have to do with the dampening ability of the polyfill? If so, then adding foam or something other than a dampening "agent" would make the sub sound like the volume has been decreased?

But....many, many, many people enjoy a lower Qtc, in the .577 (bessel) and .5 range. Especially the "audiophile" type crowd.

.577 and .5 Qtc's must take up a lot of car/trunk space I'm guessing... wow.//content.invisioncic.com/y282845/emoticons/eek.gif.771b7a90cf45cabdc554ff1121c21c4a.gif

 

[squeak9798 5,000+ posts]

So even though the internal volume is decreasing, the sub sounds like the volume has been increased? //content.invisioncic.com/y282845/emoticons/uhoh.gif.c07307dd22ee7e63e22fc8e9c614d1fd.gif .. does that have to do with the dampening ability of the polyfill? If so, then adding foam or something other than a dampening "agent" would make the sub sound like the volume has been decreased?

It has nothing to do with the volume of air the polyfill takes up. Basically, the polyfill restricts and damps the rearwave some, causing an increase in acoustic complaince of the enclosure, which essentially has the same effect as using a larger enclosure (or, lowering the Qtc)

.577 and .5 Qtc's must take up a lot of car/trunk space I'm guessing... wow.//content.invisioncic.com/y282845/emoticons/eek.gif.771b7a90cf45cabdc554ff1121c21c4a.gif

Not really. Car audio subwoofers typically work with very small enclosures to begin with.....obtaining a low Qtc with a car audio subwoofer normally doesn't take all that much space.

 

[djman37 5,000+ posts]

Anywhere between .707 and 1.000 is a good range I think. My L5 is .9 and it handles well. If you get it too much lower than .707 you'll get boomy bass. Put some polyfill in the box to decrease the internal volume, that might help.

nice. polyfill makes the sub think the enclosure is LARGER. Put rigid material...wood, sand, clay, etc.. in the box.

 

[CntInjaDisNinja 10+ year member]

I dont wanna sound to much like a newb, but what is Qtc? It sounds like a T/S parameter

 

[squeak9798 5,000+ posts]

I dont wanna sound to much like a newb, but what is Qtc? It sounds like a T/S parameter

It "sort of" is. The Qts is the total "Q" of a speaker, a T/S parameter. The Qtc is the "Q" of the system (speaker in the enclosure). And since it's dependent upon the enclosure, the Qtc will vary by enclosure size. "Q" is basically a measure of the system to resonate, or a measure of damping.

The Qtc basically tells us everything about the low frequency response of the "system".....low frequency extension, transient response, group delay, frequency response, sensitivity, peak output, etc etc. Higher Qtc's have less damping, and hence less low frequency extension, less sensitivity, worse transient response and group delay, more peaky frequency response, but with more peak output. Lower Qtc's have better damping, and have better low frequency output, better sensitivity, better transient response and group delay, flatter frequency response but with less peak output.

A Qtc of .707 (Butterworth alignment) gives us maximally flat frequency response and the lowest F3 out of any other sealed enclosure (any other Qtc). Qtc of .5 is critically damped and is "transiently perfect". A Qtc of .577 (Bessel) has maximally flat delay.

 

[96civ 10+ year member]

Wow squeak, I have to hand it to you, you know a lot about this stuff... do you perhaps have some degree in physics? But anyways from what you say, it would be advantageous for me to purchase polyfill and put it in my box in order to lower the qtc thus achieving a flatter bass response and the ability for the sub to handle lower frequencies?

 

[squeak9798 5,000+ posts]

But anyways from what you say, it would be advantageous for me to purchase polyfill and put it in my box in order to lower the qtc thus achieving a flatter bass response and the ability for the sub to handle lower frequencies?

Only if you enjoy that type of response //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

Quite honestly, most "street beaters" enjoy a higher Qtc enclosure. And a lot of "manufacturer recommended" enclosures are higher Qtc enclosures for that very reason....most consumers looking for subs want that "punchy", higher output enclosure