# Thread: Subwoofer Enclosure Q-Value ???

1. ## Subwoofer Enclosure Q-Value ???

Hi all,

I just got my new sub (USB2830), and now I have to make a case for it..
I have built a box before, by just putting the numbers into blaubox.
I already know I want a sealed box, my prev was one and I was pretty happy about the results
But now this sub is a lot better, so I want a better box.
Now I'm experimenting with the spreadsheet from Brian Steele's DIY Subwoofer Pages.
But I have one Question.
What does the Q-value in this spreadsheet mean ?
I know I can set Q from 0.6 to 1.0 , but what does it do ??
With some different Q values, the box size will be 2x as big.

Here are some off the specs of my sub.. (maybe someone else knows a better box for this...)

Revc (DC VC Res) = 3.6000 Ohm
Fo (Res Freq) = 29,4787 Hz
Zo (Zmax at Fo) = 56,0648 Ohm
Sd (Piston Area) = 0,0491 sqM
BL (Flux * Length) = 12,2001 TM
no (Ref Effncy) = 0.6805 %
SPLo (SPL at 1w) = 90,3463 dB
Qms (Mech Q) = 5,8790
Qes (Elec Q) = 0,4034
Qts (Total Q) = 0,3775
Vas (Acous Vol) = 110,8172 Liter
Cms (Compliance) = 323,7024 uM/N
Mms (Total Mass) = 90,0488 Gram
Mmd (DiaphmMass) = 83,7929 Gram
Continous Power = 400 Watt
Diameter = 12 Inch / 30,48 cm
Voice Coil = 50 mm
Mass Added To Cone = 58,50 Gram

These are all the specs I got with it..
I was thinking about a sealed box of 37 Liters..
Anyone prove me wrong ?

Greetz,

2. i am far from an audio experts, but i think this is right:
i believe the Q value determines the frequency range of the box... higher q values will narrow the frequency range, and opposite for the low...i cant recall which makes the box bigger

now here's what you can do:
most DIY speaker designers aim for a q of 0.707 when designing their enclosures.

i reccomend you take a look at www.diyaudio.com , the people there are VERY knowledgeable adout all things audio, however they usually come across as a bit elite. some of them have homemade equipment that rivals the best commercial components and even betters many of the more store bought crap that the audio industry pedels as "high fidelity".

dont be affraid of them though, just explain what you are doing and that you are trying to learn the ropes as far as enclosure building goes.

~Mike

edit: i just found this on a speaker definitions page:
Q - the magnification of resonance factor of any resonant device or circuit. A driver with a high Q is more
resonant than one with a low Q.

Qes - the electrical Q of the driver.

Qms - the mechanical Q of the driver.

Qts - the total Q of the driver at Fs. Qts = Qes x Qms/Qes + Qms.

Qtc - value for the damping provided for a driver in a sealed enclosure. Denotes the enclosures ability to
control the driver response at resonance. Qtc = 0.707 is the optimum value for sealed enclosures, providing
flattest response and highest SPL for deep bass extension. Enclosures for this value are often rather large.
Lower Qtc can give even better transient response, down to a Qtc of 0.577 for the best damping and
transients, but the enclosure is usually huge and SPL's are down. A Qtc of 1.0 is a compromise between deep
bass and transient response vs. smaller sized enclosure. Larger subs can go with an even higher Qtc, as their
resonant frequency is often very low, but Qtc's above 1.5 can begin to sound very muddled and boomy, and
sacrifice deep bass extension and transient response for enhanced mid-bass peaks (louder).

3. Thanks for the input !!
It explain's some things...
I had designed the enclosure with a Q of 0.7, giving me 37 liters.
I designed a box of about 40 liters, taking into account that the sub will consume 3 liters in the box.

inner measurements. 0,35x0,35x0,32m (WxHxD)
and is made of 20mm MDF.
The box has no braces.

Right now it's drying from the glue, after work I will paint it, and tommorow I will put the sub in, and test it in the car..

I will let you guys know how it performs...

Greetz

4. 20mm MDF??? you sure its not 18mm??? I looked for 18 but was told it was very rare.. :P

5. I think it was 20, if I'm not mistaken... (otherwise, it could be 18mm... but it's enough for this enclosure)
My dad is some kind of carpenter, so obtaining these materials is not that hard..
He brought me a big plate from which I told him to create the box..
With my dad having more than 30 years experience with wood I'd better let him make the case.. (than, at least all the angels are right.. hehehehehe)
(I only gave him the measurements, and told him to use lots of, I repeat lots of glue... He wanted to use staples, but I wanted screws and glue)

I'm pretty curious how it sounds....

Greetz

EDIT:...
I had a box.. But I got a new car.. (whoooo)... so I needed a new box.. (the other one didn't fit and was to big.. 56 liters...hehehehe)
I had a Peugeot 405 Diesel,
I Now have a Peugeot 406 Diesel... yeah.....
runs great !!!

Greetz

#### Posting Permissions

• You may not post new threads
• You may not post replies
• You may not post attachments
• You may not edit your posts
•