Is my box too big?

[mr_push_pull]

I think that my bass-reflex box is too big. The bass is boomy and it rumbles. Instead of building a recommended and tested enclosure of 28l I made it of 40 liters. Now, making some simulations I got to the conlusion that shortening the port is equivalent to lowering the box vulume: the SPL resp extends a bit lower but with faster rolloff, the peak power handling due to maximum cone displacement gets bigger. There is a slight difference in transient response but I think it will not be audible. But something tells me that I'm missing something since removing the port completely seems to make it even "boomier". I'll experiment but I'd like to know what is it that I'm missing. Also, other suggestions that might help me get rid of the boomy sound are welcomed.

[BillFitzmaurice]

Boomy bass is usually caused by an enclosure that is too small, not too big. Assuming you have the box properly tuned I would guess that insufficient stuffing/lining is the problem.

[mr_push_pull]

Originally posted by BillFitzmaurice
Boomy bass is usually caused by an enclosure that is too small, not too big. Assuming you have the box properly tuned I would guess that insufficient stuffing/lining is the problem.

I suck at describing sound, but maybe boomy is not the exact word, but also slow, at least this is how I perceive it. Does boomy bass come with slowness too?
Can this be because of room gain? Also, could the fact that I haven't broken-in the drivers be of any importance? I've read an article on the Visaton webpage where they state that the effect of breaking-in is practically inaudible, and prove it with measurements and theoretical explanations. And, if this persists with more damping material, should I shorten the port or extend it? I'm pretty confused, theory and practice are starting to contradict each other.

[Tomac]

Could you give us the T/S of that driver?
I suspect it might be peaking at pipe resonance.Some of the box calculators don't calculate it.You should probably make the pipe longer.
give us the specs,please

[mr_push_pull]

Originally posted by Tomac
Could you give us the T/S of that driver?
I suspect it might be peaking at pipe resonance.Some of the box calculators don't calculate it.You should probably make the pipe longer.
give us the specs,please

http://www.visaton.com/english/artik..._457_1_19.html

I used published specs.as I was assured times and times again that Visaton is very strict on parameter deviations and I trust this brand. I could measure them of course but right now I don't have a low distorsion amp to do that.

[Tomac]

What are the dimensions of the box you are currently using?
dimensions of port?
Judging by the simulation it shoud work without "boominess" in 40 l box.
But if the parameters are quite different than the published ones,than this simulation has no use. I do own pair of W170s which were measured to have Qts of 0.7 . I didn't measure it but I trust this guy who did measurements.
If this driver also has higher q than it was published ,it might cause bass to sound without control.
Overdamp your box and make a port longer.This should help.Without measurements it is hard to guess the solution,becuse first you should guess about the cause...
put lot of damping in that box
if there will be no improvement,than you'll have to measure T/S again.
don't be desperate,even if you find out it has higher Q you can put it in closed box,or you could make a TL.
Report us on your progression

[mr_push_pull]

Sorry for not giving all the details from the beginning.
The BR tube: http://www.visaton.com/english/bildg...eichnung1.html
I haven't cut it.
Dimensions of the box: 1mx20cmx20cm. The woofer is placed approx 20 cm from the top. The port is cca 10cm from the bottom.
You can find all the details here (scroll down to GM's first post): s this setup OK? (especially for MJK and GM) I only made very small adjustments to what is listed there. Don't be confused by the title, I hardly think of it as a TL, it's too short.

I will measure the drivers tonight, even if this will mean going to bet at 3 AM That huge deviation you measured is very scarry.

[richie00boy]

Originally posted by mr_push_pull
Now, making some simulations I got to the conlusion that shortening the port is equivalent to lowering the box vulume: the SPL resp extends a bit lower but with faster rolloff, the peak power handling due to maximum cone displacement gets bigger.

Shortening the port will make the tuning frequency higher, this makes the air velocity higher and less linear. Also, as you noticed the transient response worsens.

If you are getting boomy sound the last thing you want to do is make the port shorter.

This driver has Qts a little on the high side, and Vas a little on the low side, for use in a vented box. It may well not be the tightest sound that you can hope for.

What diameter port are you using? What frequency are you tuning it to?

[adason]

have you tried to close the bass reflex opening?
should cure the problem since the box is big you will have enough low frequency extension without bass reflex

[mr_push_pull]

Originally posted by adason
have you tried to close the bass reflex opening?
should cure the problem since the box is big you will have enough low frequency extension without bass reflex

Yes, I did put damping material into the port enough to choke it completely. The boominess has gone but I had no bass.

Originally posted by richie00boy


What frequency are you tuning it to?

With the current parameters the tuning is at 44-45 Hz.