YIOF's sub thread

[yepimonfire]

this thread is because i am building a subwoofer and want to keep all questions or whatever else i post about it in one thread.

first question, i was planning on adding one 4" port but wondered if 3 two inch ones would work just as well.

 

[annunaki]

That will depend upon the driver itself and the vent airspeed along with the power available. What are you thinking here?

 

[yepimonfire]

like what do you want to know?

 

[bandphan]

like what do you want to know?

what driver

 

[annunaki]

what driver

Well that is a start...

Along with:

What are your expectations or goals for the system?
what is the size of your room?
what type of budget are you on?
what are your limits for enclosure size, etc?

 

[yepimonfire]

http://www.parts-express.com/pe/pshowdetl.cfm?&Partnumber=295-334

the enclosure has already been cut to size, 33x12.5x20.5

the sub has already been designed to use that woofer in a ported enclosure, i have a calculator that tells me port lengths etc i just need to now decide what size port to use and the assemble the enclosure and do some bracing etc, the goal of the sub is to do a better job then the polk i have now and kind of as a learning experience. i want to avoid port noise at reasonable levels (90dB) the enclosure is tuned to 24hz

 

[bandphan]

http://www.parts-express.com/pe/pshowdetl.cfm?&Partnumber=295-334

the enclosure has already been cut to size, 33x12.5x20.5

the sub has already been designed to use that woofer in a ported enclosure, i have a calculator that tells me port lengths etc i just need to now decide what size port to use and the assemble the enclosure and do some bracing etc, the goal of the sub is to do a better job then the polk i have now and kind of as a learning experience. i want to avoid port noise at reasonable levels (90dB) the enclosure is tuned to 24hz

Who or what gave you the enclosure size based on the T/S parameters of the woofer? When doing a build for the first time, you need to provide all of the specifics as best you can

 

[yepimonfire]

aj vented designer ajdesigner.com

 

[Seth=L]

Pardon my confusion, but that driver is not a subwoofer. Would it not make sense to get a driver that's meant to be used in a subwoofer application versus a woofer?

Why wouldn't you want to do a build around a subwoofer like this one?

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=295-550

It's in the same price bracket, handles much more power, and is slightly more sensitive.

 

[bandphan]

Pardon my confusion, but that driver is not a subwoofer. Would it not make sense to get a driver that's meant to be used in a subwoofer application versus a woofer?

Why wouldn't you want to do a build around a subwoofer like this one?

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=295-550

It's in the same price bracket, handles much more power, and is slightly more sensitive.

or bid on this

Id run a better modeling program, shoose a better driver and let us know what you are going to power the sub with and how is it going to EQd. Rob can give you some great direction but dont start running before you learn to crawl.

 

[Seth=L]

or bid on this

Hell ya, doesn't get much better than that for a 10" subwoofer, at least not for the money you can get them for.

dont start running before you learn to crawl.

Where would I be now if I had followed this sentiment?

 

[yepimonfire]

guys keep in mind that even if i didnt chose the best driver it is the driver i must put into the box since the wood and cuts have already been purchased, i simply need to know if 3 2" ports would work as well as one 4 inch port.

 

[GO-NAD!]

guys keep in mind that even if i didnt chose the best driver it is the driver i must put into the box since the wood and cuts have already been purchased, i simply need to know if 3 2" ports would work as well as one 4 inch port.

Well, I've only built a pair of identical subs (under Annunaki's tutelage) and I only have a basic understanding of porting.

But, I would've thought that multiple ports would each be the same length as a single port and that the cross-sectional area of those ports should add up to the same area as the single. The area of a 4" port is less than that of 3 x 2" ports. (That is, if you are trying to maintain the same tuning frequency).

By the way, how were you able to come up with your tuning frequency before you finalized your port dimensions?

As for the wood - it's cheap. Don't feel that you have to commit to that driver because you've already cut it.

 

[bandphan]

guys keep in mind that even if i didnt chose the best driver it is the driver i must put into the box since the wood and cuts have already been purchased, i simply need to know if 3 2" ports would work as well as one 4 inch port.

Its very hard to work backwards. The box should constructed to suit the driver unless its sealed and heavily EQd. As Seth stated the driver you choose isn't really applicable for a sub build. When you modeled the driver what was the port size you used? Can you post the results you achevied?

 

[yepimonfire]

actually the ports must be longer to maintain the tuning frequency when using multiple ones, and the port size i originally was going to use was 4" single the driver seems ok for a sub build looking at the thermal and excursion limit calculations i can hit 100dB at 20 hz without any problems. the extension of the design is 24hz -3dB, in a room it may go down to 20. when running different drivers calculations through the designer i actually chose this driver over a sub driver because of the extension i could get, the excursion limit and thermal limits were pretty much the same. and that box was made for that driver bandphan. also according to the calculator 2 2" ports would not reach an air velocity high enough for chuffing (if the port is too small or you use too few ports its warns you the air velocity will be too high and cause chuffing.)

 

[bandphan]

What power did you use to determine the 100db @ 20hz? I can't see that happening without unexceptable thd. Can you post the plots that the software gave you? You might want to try some different software and check the results.

 

[bandphan]

This driver will not work, I just ran a quick model and you will be wasting your time and money.

 

[yepimonfire]

alright then what do i do with my cabinet? set it on fire?

 

[dkane360]

set it on fire?

yepitshouldbeonfire

 

[yepimonfire]

my box is only off by 300 cubic inches for this driver http://www.parts-express.com/pe/showdetl.cfm?Partnumber=295-485