confuse about box size for diy sub - Home Theater Forum and Systems - HomeTheaterShack.com

 
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post #1 of 7 Old 03-25-17, 09:01 AM Thread Starter
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confuse about box size for diy sub

Good evening

I am thinking about building a new subwoofer using this driver dayton Audio RSS390HO-4 15" . Still undecided if i will go vented or sealed. reading the info about this driver on Parts-Express website. In the optimum cabinet size recommended by using BassBox 6 they recommend a box size of 1.58 Cu Feet for the sealed one or 2.72Cu feet for the vented one. Yet they are offering a 3 Cu feet knock down cabinet to mount this driver .

So I am confuse. Is 1.58 Cu feet is the smallest i can go for a sealed version and 2.72 Cu feet for the vented version ? Also what is the sealed F3 or vented F3 numbers refers to

I know pretty basic questions i guess but being a newbie i am just trying to understand


Thanks for your help.

Alain
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post #2 of 7 Old 03-25-17, 09:27 AM
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Re: confuse about box size for diy sub

F3 is the point at which the subwoofers lower response is -3db.
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post #3 of 7 Old 03-25-17, 01:45 PM
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Re: confuse about box size for diy sub

I can see why you're confused; PE isn't providing an "optimum" configuration, in spite of the fact they have a section called just that. The F3 is a dead giveaway.

A quality 15" driver - which that one is - should have no issue with an F3 in the mid 20Hz range, a full octave below PE's optimum config provides. That means a 1.5 ft^3 box is way too small and the driver doesn't have sufficient cabinet volume to work with. You would have to add a Linkwitz Transform with a DSP - and a lot of power - to flatten out the response curve and get any output into the 20's. You would be better served with the larger enclosure.

FWIW, DIY Sound Group makes those cabinets for PE. You can check out their website for other options.

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post #4 of 7 Old 03-26-17, 11:44 AM Thread Starter
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Re: confuse about box size for diy sub

Thanks for the reply Jman. I went to Dayton website and found the same information about box size that was displayed in PE site. I do not know bass box but i entered the RSS390HO driver into Winisd and it returned a suggested box of 1.687 Ft 3 with a FSC of 46,45 and QTC of .703. If i enter the suggested 1,58 Ft 3 i get a FSC of 47,52 and a QTC of .718

All are with a filter of low pass butterworth N=2 120Hz seating distance 11 ft power 2000 watts but since i do not have much idea of what i am suppose to look at in winisd i am not sure what need to be tweak to see what box size is required. Is what winisd suggest is reliable ?

Alain
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post #5 of 7 Old 03-26-17, 02:42 PM
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Re: confuse about box size for diy sub

Quote:
apilon wrote: View Post
Thanks for the reply Jman. I went to Dayton website and found the same information about box size that was displayed in PE site. I do not know bass box but i entered the RSS390HO driver into Winisd and it returned a suggested box of 1.687 Ft 3 with a FSC of 46,45 and QTC of .703. If i enter the suggested 1,58 Ft 3 i get a FSC of 47,52 and a QTC of .718

All are with a filter of low pass butterworth N=2 120Hz seating distance 11 ft power 2000 watts but since i do not have much idea of what i am suppose to look at in winisd i am not sure what need to be tweak to see what box size is required. Is what winisd suggest is reliable ?

Alain
WinISD is a good program, so I don't think the issue is there.

Why model with 2000 watts? The max power handling for that driver is 1600, so you're using a peak of 25% more than the driver could actually handle. With an enclosure size that small you will lose efficiency, so a lot of power would be required no matter what, but that's quite a bit more than you should be considering. Looking over the published T/S parameters I see Fs is 21.5Hz. That further indicates the 1.5 ft^3 box is too small as the F3 is only 50Hz.

I just took a look at DIY Sound Groups website and see that the 1.5 Ft^3 and 2 Ft^3 enclosures are for 12" drivers. The smallest one they sell for a 15" driver is 3 ft^3, so it might be better to consider going that route instead.

-Jim

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post #6 of 7 Old 03-27-17, 09:54 PM Thread Starter
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Re: confuse about box size for diy sub

Quote:
theJman wrote: View Post
WinISD is a good program, so I don't think the issue is there.

Why model with 2000 watts? The max power handling for that driver is 1600, so you're using a peak of 25% more than the driver could actually handle. With an enclosure size that small you will lose efficiency, so a lot of power would be required no matter what, but that's quite a bit more than you should be considering. Looking over the published T/S parameters I see Fs is 21.5Hz. That further indicates the 1.5 ft^3 box is too small as the F3 is only 50Hz.

I just took a look at DIY Sound Groups website and see that the 1.5 Ft^3 and 2 Ft^3 enclosures are for 12" drivers. The smallest one they sell for a 15" driver is 3 ft^3, so it might be better to consider going that route instead.

Hi

The reason for the 2000 watts is because i have a Behringer EP2000 that i can use and it output 2000 W bridge. But still sure would like to understand why winisd is recommending a 1.6 cy ft box for that driver instead of 3 cu ft i will= take a look at diy sound group.

Thanks again
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post #7 of 7 Old 03-29-17, 08:00 PM Thread Starter
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Re: confuse about box size for diy sub

Good evening

After rethinking my goal and desired foot print here what i came up with

I want to build 2 X 12 inches sealed subwoofer for my home theater. I am looking to build a sub that will be very tight, fast and articulate with its bass response that would provide a great movie game and musical experience!

my listening preferences are as follow: 5% music, 45 % games 50% movies. Room is 13 X 10 X 8 and sub will be driven by 2 behringer EP4000. MY current speakers are Behringer B212XL .

Any recommendation in term of driver and cabinet size ( 14 X 14 X 15 would be a nice footprint if achievable) and amount of polyfill i should stuff the cabinet with
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