[fusseli]

I'm wanting to put together an easy-to-construct sub that's efficient on dB/$ with some sense of quality.

A reasonable size is also desirable. To pull it off I'm hoping to put the most efficient big sub in the smallest large box I can muster, rather than a high power small sub... hence the dB/$ goal.

Right now what I have put together is a prefab 3.0cuft box, the new version of the 15" Dayton Classic Sub (DCS385-4), in a vented alignment tuned to 24Hz with a cheap 4"x17" port kit (air velocity doesn't break 20m/s). Powered with a 300W Bash amp, xmax isn't breached until <17Hz. The total comes to about $425.

Comments on the build or suggestions for similar price and performance? This sub will be integrated into my system, the mains are 3cuft w/ 12-inchers.

I've considered a sealed sub but for a good Qtc I'd have to go with a much smaller sub and lose out on a lot of output (this 15 in the same box has a high Qtc of 0.9+). A big point to limit cost was to stay on the 240W or 300W power range. The 3.0cuft sized box is about as big as I can really go since I'm trying to avoid building one or having a box built for this project. The goal being to have this sub for a couple years until I can go all out on a "real" sub ;-)

EDIT: final specs are 3cuft, 4"x24" round port tuned @ 21Hz w/ Dayton QT385-4 & 300W Bash amp. EQ'd via computer with +2db @ 20Hz and +2dB @ 31Hz.

w/ LPF @ 60Hz

 

[Mike P.]

Can you upload the driver file?

 

[fusseli]

Is this what you wanted? Files attached.

To be more clear, the available cookie-cutter boxes on partexpress are 1.0, 2.0, and 3.0cuft. I don't know of any others.

After another test, it looks like the 15" Dayton Quattro (almost identical xmax) might be a better option, much better output below 40Hz, smoother response, and runs off of the same 300W. $25 cheaper, too.

LPF @ 60Hz

with subsonic filter

 

[Mike P.]

I'm looking for the driver file from the Drivers folder in WinISD, it would save me the time of creating my own.

 

[fusseli]

I'm looking for the driver file from the Drivers folder in WinISD, it would save me the time of creating my own.

Ah, I follow. Both are attached to my post above this.

 

[Mike P.]

Is 3 cu.f.t as big as you can go?

 

[fusseli]

Ya, since I want to avoid building a box and the biggest prefab from PE is 3cuft. I see that something twice that big would have some impressive results though... .

 

[Mike P.]

The Quatro 15 would be the way to go in my opinion.

 

[fusseli]

I've been thinking the same thing. Thanks for looking into that. Would you also agree the 15" Quattro is probably a better bang for the buck solution over some 12" setup with the same 1-3cuft and 240-300W available?

 

[Mike P.]

I haven't modeled any cheaper 12's but I imagine you might get more low end output but it will be at the expense of SPL. Model some Dayton 12's and see what you come up with.

 

[fusseli]

Well I've found a pretty good setup with a 12" Dayton Reference HF. Using the same box and vent it (tuned 0.7Hz below Fs) would handle over 500W (though limited to 400W thermal), and outperforms the 15" quattro. Only kicker is that for the sub and more powerful amp it's $150 more :-/

So... the 15" setup for ~$400 or the 12" RS setup for $550... Can't decide! How safe would it be to run the 12" at 500W, when it's rated at 400W? Xmax doesn't breach until the sub 20Hz range, it's just that VC rating I'm worried about. The solid 3dB in the 20-30Hz range almost makes me want to spend the $150 more!

 

[Mike P.]

Can you upload the 315HF-4 file please?

 

[fusseli]

Here's the file.

After closer examination, I'm not so sure. The 4" vent isn't quite big enough for the 12" RS, the group delay is actually worse than the 15" Quattro, and there's that worry about being 100W over it's thermal rating. I'm not sure all that worry is worth the $150, even for better sub bass performance...

Leaning heavily towards the 15" Quattro setup.

 

[Mike P.]

The 12" would only handle 500 watts if the Hi-Pass filter on the Bash 500 amp is changed to 20.7 hz to control the over excursion. With that being done there isn't much difference between the two to justify the extra $150.

 

[fusseli]

Ya, not worth it. Thanks again for checking that for me!

I opted for the 15" Quattro setup last night, tough to beat the dB/$ and construction will be super easy. Parts as follows:

Dayton QT385-4
Spikes
3.0cuft Prefab box
4" port kit
Bash 300W @ 4 Ohms, 0.09% THD

 

[Mike P.]

The port won't fit in that cabinet and have enough clearance without either using an elbow or part of the port extends out the back of the box. You need 4" of clearance from the port intake to any cabinet wall

 

[fusseli]

Haha funny you mention that, I was just mocking it up in CAD to take a look at that and get everything spaced and measured.

Why does the spacing from the end of the vent to the wall have to be the same as the vent diameter? The way I was thinking of it, if the vent is 1" from the sidewall the area around the vent's flare will still be as large as the cross-sectional of the vent itself, so how does that limit airflow or harm the vents performance? If I shorten the vent by 1" It'll only lose 0.6Hz of tuning. I could also easily switch to 4" vent parts and put in an elbow if it's known to be an issue...

Here's the layout. Area surrounding the flare: 2 x pi x 3.875" x 1.375" = 33.5sqin ; Area of the total 7" flare: 21.9sqin Am I wrong to assume the 1-3/8" spacing is too close to the wall for some other reason?

 

[Mike P.]

The air speed is just under 26 m/s at 21 hz which is the maximum you want to go with a 4" flared port. At that speed you need at least one diameter away from a cabinet wall to prevent port noise.

A 4" Schedule 40 PVC elbow is under $5.

 

[fusseli]

Ahhh. Didn't even think of port velocity for the spacing, that makes some sense that low airspeed could tolerate closer spacing. I'll just give the tube a slice and put an elbow in when I'm putting it together.

If I take the bend sideways does it really matter which way the internal flange faces? E.g. towards the rear wall or towards the driver? I think I've read that port placement essentially doesn't matter, but I think I've also read that it does effect some things for some specific alignments...

 

[Mike P.]

It doesn't matter which way it faces as long as it has the required clearance. Measure the port length through the center of the elbow to get the correct length you need.