Subwoofer design question(not how big a box)

[Robert F.]

Hello all,
I am going to build my first subwoofer and would like some information that I can not find for myself. I am using WinISD beta as a design tool. I have two possible plans on the table now. One plan is to use Dayton RSS265HF-4 10" in a 2 cubic foot box with a 3" vent 15.81 long tuned at 22.77Hz powered with 500 watt Dayton plate amp. Second plan is Dayton RSS315HF-4 12" in a 2 cubic foot sealed box with same type of amp. My question is how would these compare to each other? My room is 14' X 16' with 16' length totaly open to another room. Volume I like is moderate but when I feel froggy I will tend to turn it up some. Wish to have setup good for 50/50 HT & music. Am trying to keep enclosure size down for WAF. Also is there any negative effects of haveing these two drivers in a downfiring design? I don't know if gravitaional force pulling the cones down will be a problem.

Thanks

Robert

[ThomasW]

First of use WinISD Pro alpha if you must use WinISD. Personally I prefer Unibox but using it requires a copy of MS Excel.

Some drivers are better than others for down-firing applications. That said regardless of whether or not they pass the 5% test, any driver used down-firing will have a shorter life than one used in a vertical orientation.

Here's the webpage with the formula for calculating 5% sag

http://www.parts-express.com/resources/woofer-mount-up-down.cfm

[brent_s]

First, while I think all of the RS series pass the 5% sag rule, I don't think downfiring is ever really a good thing for a driver, IMO. Depending on how close to the limits you push the driver, you may never notice the changes even if you run it for 10+ years.

Without knowing the room gain, which is effected by both room dimension and room placement, it's hard to say how much help the sealed RS315-HF is going to get. I used to run NHT1259s that modelled similarly, f10 @ 20Hz, that were essentially flat to 20Hz in room.

You've got some real potential for port noise below 30hz with the RS265-HF in that alignment. Even at half power, 250 watts, you're exceeding the Peerless suggestion of 34 m/s below 26Hz. The ported alignment will sill see the same room gain as the sealed box, so whatever output advantage WinISD gives the ported RS265-HF should be present in room below the room gain corner frequency. Being almost ruler flat to 25Hz, you'll probably have a natural "house curve" with room gain added.

I have an alternate suggestion. One I plan to build for my own living room in the near future. John at AESpeakers has his PR15-1050 on sale for $50. It will tune 2 ft^3 to 21Hz without any additional mass applied. I plan to match it with an RS315-HO, but it would do the same thing with a RS265-HF in place of your proposed 3" port. Since WinISD deals in net volumes (gross - driver/port/bracing), you should be able to get a slighly smaller overall cabinet going with a PR instead of a port. The RS315-HO with PR shows the least cone excursion with 500 watts while only giving up about 2dB at 30hz (less above/below) to the 265-HF ported. Since the 265-HF is well beyond rated Xmax at that point, the 315-HO/PR should be capable of more real world output, as one would expect when comparing a 10" to a 12".

For my tastes, any of these should be ok in a room your size. "Moderate" and "froggy" are subjective terms, though. My typical movie watching volume in my dedicated theater room (24'x16'x9') produces peak readings in the 95-100dB range...that's all speakers/sub on real sound tracks, not test tones. That level can still produce vibrations in the house structure (mostly stuff on the wall) 35' away and down half a level even if the high frequencies aren't audible beyond 10' or so from the theater's hollow core door. YMMV. :-)

-Brent

[orlofstg]

PR's

I agree with Brent. I reconfigured a down firing 15" sub that was in a vented 3ft2 box built to ***** specs. I went to a smaller front firing box with a pair of 15" AE PR's. No more port noise during movies, ruler flat response, and a smaller box. It looks cooler IMO too. :lol:

Edit by moderator to conform to forum rules

[Robert F.]

Thanks gentlemen,
I am new to DIY sub building and the passive radiator idea did not cross my mind.
Now that I have this new avenue to explore I am going to see what I can come up with.
Plans now are for 2 cu foot enclosure with one AE PR15-1050 as per Brent. Driver will be RSS315HF or HO. Have to figure out what version of driver will work best for me.
Amp will be 500 watt Dayton. I have the amp already as I picked it up at PE during the black Friday sale. I have no software except WinISD and I downloaded WinISD Pro. The Pro version has passive radiator modeling. Now I need to see what box/driver parameters I can come up with. In the future I will purchase better software, perhaps Unibox as Thomas suggested. For now I need to ease myself into the DIY hobby.

Robert

[Amphiprion]

Did the 5% sag test exist before Dan Wiggins and the Avatar Shiva?