Help designing DIY box for RSS315HF-4 12"

otakar

Member
2020-02-10 5:51 pm
Hi all, I should start by saying I'm a complete noob to box DIY speaker building as well as forums, so I am sorry if I get anything wrong/say something stupid but is all a learning curve..

Having spent the last month trawling the internet trying to work out the best way to go about starting my first DIY project and, seeing as I had loudspeakers but no sub, I decided to go for building my own. I spent many hours trawling threads and watching youtube videos I decided to order the RSS315HF-4 12" from Dayton, largely due to lack of options in the UK.
Now I have my driver I think I have decided to start with sealed and then maybe build a ported design at a later date. I found the zaph audio design and was about to go ahead and follow that but then realised I would probably want to build a passive design as the main reason for wanting to learn DIY speaker building is I aspire to build some sort of smallish rig for parties in the future. So I guess my main questions are:
- is it a bad idea to go for a passive subwoofer given my situation?
- if no, how would I go about modifying the design to work for a passive box?
- and does anyone have suggestions for 4 channel power amps which would allow me to add more speakers in the future?

Sorry for the long post and again if something doesn't make sense due to lack of knowledge, hope someone can help!:)
 
A passive speaker is one that doesn't have the amplifier built-in.

A Behringer NX4-6000 should do just fine for you, but you'll need a crossover or other signal processor to make sure the mid/high range doesn't get to the 12" subwoofer. It won't damage the driver (although the tiny bit of extra heat isn't useful), but will sound bad if the 12" cone tries to produce that range.

For home use, sealed boxes are fine.
For parties, you might want something more efficient and sturdy - that's where PA drivers come in.

FWIW, I'd strongly recommend the purchase of a measurement mic.

Chris
 

otakar

Member
2020-02-10 5:51 pm
A Behringer NX4-6000 should do just fine for you, but you'll need a crossover or other signal processor to make sure the mid/high range doesn't get to the 12" subwoofer.


Thanks for the response! I checked out that amp and from the little I do know about matching amps to speakers, does this not have a way too high output for the driver given that it has an impedance of 4 ohms and and r.m.s power handling of only 400W? on the Behringer website it seemed to be saying that the Nx4-60000 had a 3000W output! would this not blow the driver? (sorry if this is all completely wrong).

Also I've been trying to use WiniSD to learn about enclosure design and sizes and was wondering, is the box volume given by the software the total volume of air needed inside the box? i.e. would I need to make the actual internal volume of the box significantly larger to account for the bracings and driver itself taking up room?
 
otakar,
Yes, bracing, driver, ports (bass reflex), baffles and all. It's the NET vol. of air (vs. gross or outside dimensions.)
Calculating Internal Enclosure Volume

To find the internal volume of an enclosure, internal dimensions must be used. Internal dimensions can be found by subtracting the thickness of wall and dividers from an external dimension.
Calculating Enclosure Volume – JL Audio Help Center - Search Articles
 

4real

Member
2004-05-27 8:51 pm
Steyl
Thanks for the response! I checked out that amp and from the little I do know about matching amps to speakers, does this not have a way too high output for the driver given that it has an impedance of 4 ohms and and r.m.s power handling of only 400W? on the Behringer website it seemed to be saying that the Nx4-60000 had a 3000W output! would this not blow the driver? (sorry if this is all completely wrong).

Yes it could blow the driver. So could a much lower power amp playing full power at the wrong frequency. It's all relative and in the end you can better have too much than too little. For the money that thing has a lot to offer. Only disadvantage is that is missing a DSP, so you cannot filter the sub(s).

Also I've been trying to use WiniSD to learn about enclosure design and sizes and was wondering, is the box volume given by the software the total volume of air needed inside the box? i.e. would I need to make the actual internal volume of the box significantly larger to account for the bracings and driver itself taking up room?

Yes the volume is always the Netto volume, which excludes bracing, port volume and volume of the driver and magnet assembly. On the other hand, filling the box with polyfill or equivalent will increase the netto volume again (speed of sound is lower though the material).
 
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otakar,
As 4real said you would benefit from an amp with DSP. About 400W in 4 ohms is more than enough for this driver on a bass reflex. About ~65L NET and +10L driver and ports volume to play with various alignments.
In case of a sealed speaker you ONLY take advantage of ~50W from the amp because of excursion.
 
Thanks for the response! I checked out that amp and from the little I do know about matching amps to speakers, does this not have a way too high output for the driver given that it has an impedance of 4 ohms and and r.m.s power handling of only 400W? on the Behringer website it seemed to be saying that the Nx4-60000 had a 3000W output! would this not blow the driver? (sorry if this is all completely wrong).

Also I've been trying to use WiniSD to learn about enclosure design and sizes and was wondering, is the box volume given by the software the total volume of air needed inside the box? i.e. would I need to make the actual internal volume of the box significantly larger to account for the bracings and driver itself taking up room?

The NX4-6000 will do 300/600/1000w/ch into 8/4/2ohm, so your 400w driver will be pretty safe with 600w on tap. Just turn it down if things start sounding ugly.

If you bridge the amplifier, it'll do 1200/2000w into 8/4ohm, which would put your driver in more danger.

The NX4-6000 will run the sub you're planning just fine, and when you want to expand for party use it'll still hold up.

Chris
 
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This subwoofer is indeed not fit for parties, it's a hifi sub, to lo in efficiency and too fragile for abuse like done by dj's at parties. Therefor a pro audio subwoofer is more fit.

But for hifi (home) use, this one in a 40L sealed cabinet is very good. You'll get an good response (in room) untill about 30Hz, and can be crossovered up to 500Hz (so it can be a subwoofer and woofer at the same time).

For parties, ported boxes with a pro audio driver will be way better. This one won't keep up with party levels, especially not in open air.
 

4real

Member
2004-05-27 8:51 pm
Steyl
OP mentioned a "small rig for parties in the future" so something that would integrate like BR type speakers that would grow in number as a possibility.

Ah yes, I missed that one (for some reason the browser search failed us). Then I would definitely not build a closed sub. Tune low (65L, 25Hz), gives you 110dB from 30Hz on. Not quite enough for a big party, but plenty for some music and movie fun.

Otherwise go for a PA woofer, if 12" size needed: something like Faital 12HP1060 or 12RS1066. 30 Liters, tuned to 35Hz will do > 116dB from 40Hz. Plenty for parties. Will need 1kW for full potential though.
 

otakar

Member
2020-02-10 5:51 pm
Thanks all for the responses and sorry for the slow reply, was stuck in a hole of uni coursework stopping me from having any fun....

I'll look into the amplifiers suggested and as said above, I do hope to move onto building speakers/subs more suitable to parties after this so an amp which could do both will be perfect. So is the general consensus that a ported sub would be a bad idea for this particular driver?

Im not entirely sure I understand how the forum works still but once I begin the design and build process, is it best for me to continue to post related questions/problems on here rather than start any new threads?
 

lousymusician

Member
Paid Member
2005-11-24 4:10 am
NorCal
I have two of the RSS315HF's in sealed boxes measuring 14.5" x 16" x 17". They are made of 18 mm Baltic Birch plywood with internal bracing on all panels and a double front panel. The walls are lined with Ultra Touch insulation and the rest of the cavity is lightly filled with poly fluff. I measured the final system Q at .723, and 46 Hz resonance. A bit larger volume might be more ideal, but this is close enough considering the boxes were reused from an earlier project.

I power them with a Crown XLS1000 amp (rated for 350 W/channel @ 4 ohms) and use a miniDSP for crossover and equalization. Simulation in winISD says one woofer should hit 112 dB at full power without running out of excursion at any frequency. I would be concerned about sustaining that drive level for a long time in a small box with no way to dissipate the heat.

I don't need that kind of volume, so I trade output for deeper bass. I equalize the woofers (with a Linkwitz transform, you can look that up) to achieve an f3 of 25 Hz, Q = 0.7. Simulation in WinISD says this combination is good for 102 dB (one woofer driven) at full power and achieving full excursion at 15 Hz. With two of those in a small den (11' x 14'), I have plenty of output available for music (no movies). For a party I would disable the EQ and live with less low bass.

A vented box would be something like 2.7 ft^3 tuned to 24 Hz, or Parts Express' recommendation of 2 ft^3, 30 Hz. That would handle full power down into the 20's, but would HAVE to be high pass filtered below that to avoid over-excursion. The advantage of the BR box is in output between 60 and 30 Hz. Whether that means much to you would depend on the room and style of music you would play. In a small (e.g. dorm) room the BR could wind up sounding very boomy, the sealed box might be a better fit both sonically and physically.