how to figure out Vol of Ported Box(my first DIY)

kelticwizard

diyAudio Moderator Emeritus
2001-09-18 2:33 am
Connecticut, The Nutmeg State

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kelticwizard

diyAudio Moderator Emeritus
2001-09-18 2:33 am
Connecticut, The Nutmeg State
The following are WinISD simulations for the JL Audio 10W0-4:

A) In a 2 cubic foot enclosure tuned to 25 Hz.

B) In a 1.5 cubic foot enclosure tuned to 27 Hz.

C) In a 1 cubic foot enclosure tuned to 30 Hz.

All these are for one JL Audio 10W0-4 only.
For two, you can double the size, but I cannot vouch if the response will be the same-I have to conduct tests to see how the Q factor is affected by being hooked up in series and in parallel-or if it is affected at all.

If you hook the two subwoofers up to different channels, then it will not affect the response-simply double the volume, and tune to the same frequency.
 

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kelticwizard

diyAudio Moderator Emeritus
2001-09-18 2:33 am
Connecticut, The Nutmeg State
I recommend either one 3" port or two 2" ports-the cross sectional area is very close. If the lengths are too long to fit in your box, any home construction type store will have PVC elbows. It would be a good idea to figure the port volume and increase your box volume by that amount.


I cubic foot enclosure tuned to 30 Hz: 3" port, 18.5" long, or two 2" ports, 17" long

1.5 cu bic foot enclosure tuned to 27 Hz: 3" port, 14.88" long, or two 2" ports, 13.75" long

2 cubic foot enclosure, tuned to 25 Hz: 3" port, 12.75" long, or two 2" ports, 11.8" long

Hope this is what you are looking for. Feel free to ask more questions-that is what the forum is for.
 

kelticwizard

diyAudio Moderator Emeritus
2001-09-18 2:33 am
Connecticut, The Nutmeg State
A) If you put in two speakers, double the size of the box.

B) You do not have to change the frequency the doubled box is tuned to-but the length of the port will change.

C) If you hook up two 4 ohm speakers in parallel, you get 2 ohms. If you hook up two 4 ohm speakers in series, you get 8 ohms.

Many car amps work well with 2 ohm speakers. I do not know if yours does.

If you hook up two speakers together, to be driven by one channel, I cannot predict how that will affect the response, I mentioned this before. All I can tell you is that if you double the volume, change the port length to maintain the same tuning, and hook the speakers up in series, one of two things will happen:

1) The speakers will play identically as if they were each in an individual box-that is, they will play like the charts indicate they will

OR

2) The sound will become a lttle more boomy-a little more bass than optimum.

If you hook the speakers up in parallel, the sound will be either unaffected or the bass will get thin.

Knowledgeable people have maintained that it would go both ways. Until I do some testing myself, I cannot tell you what will happen.
 
I have completed my box it looks great. But i have one more question. I have a electronic crossover hooked up to the amp and it has a few settings.one for sub freq, one thats says freq with a bass boost 0dB to +12dB, i dont know what freq to set to im stupped? PLz Help. its a 3cubic ft box with two 10inch jl tuned to 27Hz.
 

kelticwizard

diyAudio Moderator Emeritus
2001-09-18 2:33 am
Connecticut, The Nutmeg State
I am not particularly familiar with all electronic crossovers. I believe the "Sub freq" would be the frequency where the sub starts playing-the crossover frequency. To know the proper setting, you would have to know where the speakers that you are crossing into start rolling off in the bass. Barring that, the best advice I can give is to try several settings, and go with the most natural sounding one.

Remember, the loudest setting is not necessarily the right one, because all that could mean is that the car speakers and the sub are overlaping each other, which is not good either.

As far as frequency with a bass boost, not sure of that either. I think you might want to open a separate thread on this-others might have experience with your electronic crossover. If I had to take a guess, I would guess that you can select a frequency-say 40 Hz-and boost it anywhere between 0 and 12 dB. Some speaker designers build their boxes small, tune the box too low and use the bass boost to bring the response up.