# sealed enclosure for a low-Qts subwoofer?



## s0n1c (Aug 9, 2005)

help guys...

i know that low-Qts subwoofer drivers (Qts<0.4) are meant to be used in ported enclosures given that the drivers are well damped. but my question is, can a well-damped, low-Qts driver also be used in a small sealed enclosure, and still produce a Qtc below 0.7? It seems logical because a very small sealed enclosure that has very little damping would be a good match for a well-damped driver...

My goal is to have a subwoofer in the passenger footwell. I want a Qtc below 0.7 because I pefer dry-shouding bass over muddy/boomy bass. Also, I want it in a very small sealed enclosure because space is scare.

Thanks in advance.


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## 300Z (Mar 20, 2005)

In my opinion i think it depends more on a speciffic driver than just the low Q factor... you just loose a lot of output using such drivers in sealed app...

If you like dry sounding subs, you may like the Diamond Audio old M5 (second gen)... i had a single 10" and at first i had problems getting it to blend in with my front stage but once i got it right damn it sounded good. and for a .7 Q it only needed .38cu.ft...
Now the sub is in my roomates ford focus in a 1cu.ft ported box tunned to 28hz and it sounds incredible... better than when it was on my car... 

Leo


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## npdang (Jul 29, 2005)

Tight bass in the car is usually due to:

Flat, smooth frequency response.
Good integration with the frontstage.
Proper level matching.

Don't worry too much about the enclosure alignment. In fact, if you ask most car audio enthusiasts they'll say that smaller, underdampened alignments give tighter bass which is somewhat counterintuitive.


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## DearS (May 14, 2005)

I agree, or better yet, I'm joining the winning side. my bass was really good after a spent a bit of time matching the front speakers to the sub. without my mids helping the sub, the bass never got to sound fast, accurate and tight. then I was glad the sub was pretty flat, even when the bass got deeper. but then I was going after lower and lower bass. then I heard nothing. just when I thought it was enough, I had reached Xmax. its really nice to have the full spectrum of sound and have it flat.


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## rutger j (Aug 1, 2005)

hmm, I repost my respons (all that I can remember anyway ) due to npdang´s webhost change:

graph one is the first curve I competed with.
It earned me a dead last place finishing...
The judges had some not so nice comments about the sound, and when you look at the graph You see why...

1
http://forum.lazzat.se/attachment.php?attachmentid=9378

Graph 2 is my latest curve.
It earned me a 3rd place finishing...
Look at the 20-50hz region, it differs 1 db from the lowest "peak" to the highest...!!!!!!!
I believe we looked at it in 1/36 or something and still couldn´t see any peeks/dips higher than 1 db, comparing the lowest to the highest.
Btw, the guy who made the RTA reading were close to ecstatic 

2:
http://forum.lazzat.se/attachment.php?attachmentid=9379

The sub is a *Digital Design 3510c * 2x2 ohm dvc

I hope this foil any questions whether DD is a db sub only or not...
It works really fine for SQ as well (Jassa Langford initial made them for SQ at the beginning, but since the DD´s can take such a beating, all the db boys/gals started using them)

The difference between the 2 graphs are two things, some EQ and different X-over freq and slopes.

Graph 1
High: 2,5 khz/6db - and up (Through), no attenuation
Mid: 25hz/6db(or Through, can´t remember which one) - 2,5khz/6db attenuated -2db
Sub: Through - 40hz/6db attenuated -2db

No EQ

Graph 2:
High: 4,3khz/18db - and up (Through) no attenuation
Mid: 25hz/12db - 5khz/18db attenuated -2db
Sub: Through - 50hz/12 db no attenuation

EQ: 
-1,5 db at 315hz
+2.0 db at 1,25khz

The first settings resembles the Factory settings of my Dynaudio 240mkII system (I haven´t the x-over boxes, just the speakers).
Dynaudio utilizes only 6db on their x-overs, and the x-over freq is 2800hz.

The sound from my first settings were:
harsh trebble, lack of bass, ok midbass, lack of "feeling/body(thats the word we use in Sweden for this)/omph in the midrange/midbass"
And the singer/singers sound as if they sing into a cup or something...

Settings two on the other hand has close to everything I want.
Smothness, body , omph, and so on.
The "cup" is also gone, mostly thanks to the 315hz adjustment.
I also got the maximum points (15p) in "listening pleasure".
And to be honest, that´s all I´m looking for: To see people smile when they listen to the car.. 

Maybe my system diagram has nothing to do with the initial question, but I wanted to give You all the "low down" of my system, and also show that there are more things to a systems integration than just adjusting the EQ 

Best Wishes
Rutger

Fell free to ask me any questions regarding my system


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## s0n1c (Aug 9, 2005)

Thanks for the inputs guys.

Rutger,
What I had in mind is actually close to your setup. I plan to use a DD1008 in a very small sealed enclosure mounted at the front passenger footwell. 

Why DD? I noticed that almost all DDs have very low Qts and Fs values, which means that they would sound very deep, and be suited for either ported or very small sealed enclosures because the drivers are well damped.

Using WinISD, I modeled a DD1010 on a 15L enclosure... it resulted to a Qtc of <.7... very good for such a small enclosure. So I assume that a DD1008 would have a Qtc of <.7 on a 15L or even smaller enclosure. 

Others would say that even if a very small sealed enclosure would work (in terms of Qtc and FR), this would severely limit system output. I agree with them... but maximum output is really not a big concern of mine since the sub would be right infront of me.

BTW, my curret 2way setup plays reletively smooth and flat from 63Hz-20kHz...
I'm running an Alpine SPX-177R (Type-X... the Vifa made drivers) with a Butler Audio TD1500 amp. Incorporating the DD1008 from 50Hz down should work out nicely.

Wish me luck


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