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Old 22nd January 2011, 02:38 AM   #1
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MichiganMan's Avatar
Join Date: Jan 2011
Location: North of "The Strait", Michigan
Default My first crack at WinISD - please take a look-see

Here's the Reader's Digest version - I want to build a sub for my living room HT, prefer to keep the cost around $400-600 excluding finish supplies.

I was originally intending to go with a BFM THT, but even in my living room that is one big box, and I had read enough to wonder if the goals of a horn design didn't quite jibe with what I wanted.

So, I started thinking about sealed or ported designs. I have couple of places around the room where I can put a sub, though the size would have to vary depending on exact location.

Assuming I get decent performance in the preferred spot, I could go as big as 24 x 24 x 36 or so, which gives me a 12^3 box, or 340 liters not counting bracing, drivers, ports, etc.

I started seriously playing with WinISD Pro to see what I could come up with. I found a driver file for a couple different Dayton 15" subs, the RSS390HF and the RSS390HO.

Here's what I got out of WinISD - I *think* I was doing it correctly!

(Link to Picasa slideshow...)

In looking at the model, it seems that the HF version of the Dayton RSS390 will provide a smoother response and a smidge more extension than the HO version, all things being equal.

I tried adding a highpass at 16 hz but it didn't make all that much difference. I also used 300W as the signal input since anything more than that and the excursion went way beyond xmax (14 mm on the HF, 12 mm on the HO).

I did have a question on the port size; the only way I could get the port velocity out of the "no bueno" zone was to use an 8 inch port, and it ends up being almost 36 inches long. I was not real sure how messing with port numbers changes things, when I tried that it seemed to produce some non-intuitive results but it is probably a chair-to-keyboard interface error.

Also, what does "series resistance" mean on the Signal tab? I just left it alone as I didn't know what it was for...

All in all, with $300 in stuff from Parts Express + some MDF it seems like one could put together a pretty thumping sub.

I would really appreciate it if some of the veterans here could take a look at this model and help me firm it up!

- Mike
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Old 22nd January 2011, 03:54 AM   #2
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OK, this stuff is seriously addicting. I've already updated The Plan(tm) but am too whooped to upload it today
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Old 22nd January 2011, 06:18 PM   #3
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Location: Toronto
I had a look at what you posted and I think your calc's are quite a bit off. 12 ft^3 IMHO is just way too big for this driver.

You also failed to mention what your design target was for this sub - HT only? Music only? HT/Music mix? the target will go a long way to dictating what the final design will be.

Rule of thumb(sanity check) is that generally the optimum enclosure size will be approximately the same as the driver VAS.

ie for the RSS390HO in WinISD the program calcs out in a ported QB3 alignment(tuned to 24Hz) to about 3.5 ft^3 (the driver VAS is approx 3.8 ft^3)

With that alignment and 500W applied you don't even come close to exceeding xmax until about 20Hz which generally will be taken care of by the HP rumble filter built into most sub plate amps.

As to port velocity with this alignment and 500W applied - a single 6 inch port should be all you need.
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Old 22nd January 2011, 07:30 PM   #4
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Join Date: Jun 2010
He does have it correct for the HF version. Winisd suggests a 11 cu ft box as a minimum to get the best alignment. If you look at the T/s parameters you will clearly see that the HF does require a much larger box than the HO version. You can feed 250 watts into the HF driver in a 12 cu ft box fine with no issues and have pretty good output.

Because off the parameters off the HO driver you can get away with a 6 cu ft box tuned to the same frequency with 400 watts and you will only be 2db down on the 12 cu ft box.

It doesn't really make sense to buy the HF personally because off the size but when it comes to modelling the HF driver you have it correct.


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Old 22nd January 2011, 09:58 PM   #5
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Location: North of "The Strait", Michigan

I find your comments very interesting. In surfing the various HT sites, it seems like the HF version is much more popular than the HO. Obviously Dayton makes two different drivers for a reason, though I find it kind of odd that they are essentially the same price. I'm sure there are differences I'm not seeing at first blush, but the HF has a somewhat greater Xmax.

Since I put this up, I've modeled a somewhat better 12 cu ft box with an HF that pretty much hits all the marks I want - relatively easy, relatively cheap, good output down to 20 hz and below. If the Feds cooperate and return my money to me fairly quickly, construction shall commence!

This is a 95% HT box, BTW.
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Old 24th January 2011, 11:07 PM   #6
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Join Date: Dec 2010
Location: SoCal
Check out this 12" from SB acoustics...
It's 4db louder, and hits nearly as low as the Dayton... (F3 of 17 vs 19)

I have spent a lot of time looking for a musical sub that also hits deep and loud. This was the best one I could find that did both, for the money... I compared 15's first, then 12's. Then comparted the best of the 15" group to the 12" winners. The SB came out on top (WinIsd mock ups). The Dayton is best suited for sealed, whereas the SB may do ok in ported. They are pretty similar in EBP with the Dayton at 37.5 and the SB at 45.2

Hope this helps. If not, ingore me
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