sub using two RSS315HF-8 speakers

[D, Rose]

Hey guys
I've picked the RSS315HF-8 for my sub. Most people last time I posted felt that two of these subwoofers coupled with the HPSA1000(now onsale!) would be a good way to go. I have two 3" precision Ports from an old project that I'd like to use. The PE finished cabinet for the 12" sub is 17x17x17-1/4. Could I just double those dimensions? How will the ports effect the cab?
I've noticed other peoples cab. sizes can vary quite a bit. John used the RSS315 in a 2.5 Cu. Ft. cab., another used a 3 Cu. Ft. cab. I'd like to get the parts ordered before the sale is over. Any help would be greatly appreciated, guys! Thanks!

[Pete Schumacher ®]

Hey guys
I've picked the RSS315HF-8 for my sub. Most people last time I posted felt that two of these subwoofers coupled with the HPSA1000(now onsale!) would be a good way to go. I have two 3" precision Ports from an old project that I'd like to use. The PE finished cabinet for the 12" sub is 17x17x17-1/4. Could I just double those dimensions? How will the ports effect the cab?
I've noticed other peoples cab. sizes can vary quite a bit. John used the RSS315 in a 2.5 Cu. Ft. cab., another used a 3 Cu. Ft. cab. I'd like to get the parts ordered before the sale is over. Any help would be greatly appreciated, guys! Thanks!

The RSS315HF-8 isn't really designed for vented boxes. it's Qts is a bit highish to get a smooth cutoff. However, venting is still an option, though the boxes can get fairly large or the port very long. To tune as low as you need to, you may want to consider going with Passive Radiators.

Three cubic feet (any smaller and you'd have to use PRs) tuned to 20Hz will require a 3" port that is 13" long. 3" is a bit meager for a 12" woofer and tuning that low. 4" diameter requires 24" long to tune to 20Hz, and would be better suited. That alignment will give you -3dB at 23Hz and -10dB at 15Hz. You'll want to make sure the sub amp is high pass filtered at 20Hz so you don't damage the drivers with signals below resonance. You can achieve deeper F3s with a larger box and slightly higher tuning, at the expense of power handling and F10. the slow roll off of the smaller box and low tune will better match most room gain curves too.

[D, Rose]

Heya, Pete!
I mentioned a couple different subs guys from PE made using just one 315HF-8;one used 2.5Cu. Ft., the other used 3. So for my two RSS315HF-8s in one box would the box be 5 to 6 Cu. Ft? I have two 3" ports from my original project( I used your front L & R Schumakubins) so I didn't use them. If I could make use of them in this sub, all the better! I have 3 sheets of MDF in the garage, so wood isn't a problem. I'd just like my spleen to pop when the Death Star 'splodes! With the sale on the power amp, nows the time, right?

[Pete Schumacher ®]

Heya, Pete!
I mentioned a couple different subs guys from PE made using just one 315HF-8;one used 2.5Cu. Ft., the other used 3. So for my two RSS315HF-8s in one box would the box be 5 to 6 Cu. Ft? I have two 3" ports from my original project( I used your front L & R Schumakubins) so I didn't use them. If I could make use of them in this sub, all the better! I have 3 sheets of MDF in the garage, so wood isn't a problem. I'd just like my spleen to pop when the Death Star 'splodes! With the sale on the power amp, nows the time, right?

You could probably get away with the 3" ports for now and see if they remain quiet during those "splozhuns" and other low frequency sections. You can always increase the port to 4" if you find the 3" version to "chuff" a bit.

Yeah, go with 3 cubic feet per driver.

[Mayhem13]

Port air speed approaches nearly 60 m/s in 6cuft so better opt for the 4" version right off the bat. The 4" precision ports will give you a near 23hz tune at 17 inches. You'll need an SSF centered around 18hz.

[D, Rose]

So, should I isolate each driver and use one port per driver, or have one 6 Cu. Ft. box, brace it all to hell, and use one port?

[Pete Schumacher ®]

So, should I isolate each driver and use one port per driver, or have one 6 Cu. Ft. box, brace it all to hell, and use one port?

You can use one volume for both drivers, and you'll need both ports at a minimum. Even then, it's more than likely that for anything below 20Hz, you will hear port noise when the power levels are pushed.

And while a pair of 4" flared ports would be better, they get to be prohibitively long to keep tuning low.

I'd like to suggest that you forget the ports for now, and just build your enclosure with the drivers on opposite sides, leaving enough room on the other two sides to host a 15" passive radiator. (You may be blown away just by the performance of this pair in a sealed box!!!)

Later, you can add a pair of AESpeakers.com PR15-1050 15" passive radiators to the other two sides, so all masses inertias cancel. As the RSS runs out of Xmax with 500W at 15Hz, the PR is running out as well. They're a good match.



Compared to the sealed enclosure, adding the pair of PRs will push F3 from 38Hz to 28Hz, and move F10 from 21Hz to 14Hz. You also gain an additional 5dB of output at 20Hz. The sealed version runs out of Xmax with 500W at 36Hz. Adding the PRs extends that to 15Hz before Xmax is exceeded with 500W. Adding those two PRs will allow your 20Hz level to reach 109dB, not considering any room lift. That will be noticeable. 3" ports would be chuffing away, compressing the output, and annoying the heck out of you.

I did something similar. I built a vented sub, 4 cubic feet, for a DPL-12 subwoofer. I used FOUR 2" ports, which has almost the same area as your dual 3" ports. Remember, only 1 woofer, of similar capability as the RSS. Port noise was OBVIOUS and distracting. I wound up cutting them out, plugging them up, and replacing them with a 15" AE PR. What a great decision!!!

PR is the way to go for low tuning.

[D, Rose]

Hey, Pete!
The passive radiators sound cool, and at 65 dollars each they aren't too pricey, but...The actual cabinet dimensions would be around 19-1/8 x 38-1/4 x 19-3/8, with the RSS315HF-8s on one side and the 15" PRs on the opposite, and put the HPSA1000 on one end, with bracing in the cab, but not actually separating the drivers in the box, right? How would you lay this setup out? Do you think I could get the 315HF-8 for the same price as the 315HF-4? The 315HF-4 is on a sweet sale right now! I'm still working on the form to make my curved sides for my schumakubins. I think this dang form is tougher to make than the speakers will be!
Thanks again for the help! If you guys are ever in the Detroit area, swing by for a movie! When this is all done, it should rock! I want this sub to pull the hide off the neighbors cat when those depth charges go off in "Das Boot"!!!

[Pete Schumacher ®]

Hey, Pete!
The passive radiators sound cool, and at 65 dollars each they aren't too pricey, but...The actual cabinet dimensions would be around 19-1/8 x 38-1/4 x 19-3/8, with the RSS315HF-8s on one side and the 15" PRs on the opposite, and put the HPSA1000 on one end, with bracing in the cab, but not actually separating the drivers in the box, right? How would you lay this setup out? Do you think I could get the 315HF-8 for the same price as the 315HF-4? The 315HF-4 is on a sweet sale right now! I'm still working on the form to make my curved sides for my schumakubins. I think this dang form is tougher to make than the speakers will be!
Thanks again for the help! If you guys are ever in the Detroit area, swing by for a movie! When this is all done, it should rock! I want this sub to pull the hide off the neighbors cat when those depth charges go off in "Das Boot"!!!

If you get the 1000W amp, and drive two RSS315HF-4 in series, you'll still be delivering 500W to the pair, which is plenty to get them moving to their linear limits. 110dB at 20Hz (without room gain) with 500W total, and you'll almost be hitting Xmax at 27Hz.

You really do want to put the drivers and PRs on opposite sides to reduce inertial forces. Instead of a plate amp, consider the 1000W "rack" style.