Ready for sub upgrade - now which configuration?

[engr_dave]

My "little" DIY JBL B380-clone sub (15" 2235H in 120L with active EQ for 24 Hz anechoic F3) served my music / HT system well. It was used as the front sub, picking up from the mains and surrounds at 60-70 Hz. LFE is handled by a different sub (18" JBL 2245H built into a seating riser).

However, the 2235H's modest Xmax doesn't support even 24 Hz at reference levels in my 3000 cu ft room. I've set up the sub limiters on my Lexicon MC-12 prepro to avoid any damage... but I think it's time for a sub upgrade :W I picked up a Crown K2 a few weeks ago and I'm considering a pair of SS RL-p15s sealed with LT (I got in on Bob Ellis' EQ board group buy).

My question is: should I go with two 60L boxes or one 120L with drivers on opposing faces? The MC-12 has outputs for stereo subs in addition to an LFE sub so I can run stereo subs next the mains (Dynaudio WMTMW) sort of like "sub-bass bins". However, I have read that dual subs (either stereo or mono) can be problematic if they're not in the same location. The smaller boxes would be easier to move around, but I'd hate to go to the trouble of two enclosures, two LT circuits and twice the BFD channels, only to have the stereo sub arrangement sound worse than a single box.

One "keep your options open" approach that came to mind was to build the boxes separately but include some sort of provision to bolt or clamp them together back-to-back. Maybe some sort of tool box latch arrangement? Has anybody ever done this?

[dyazdani]

60L seems a little small for the RL-p15...I may be wrong. I think most people are going with 100-120L per driver.

Are you just planning to EQ so you can get by with a smaller volume?

Multiple subs can often be arranged to cope with room issues, I'm planning to do the same (once the RL-p15 is back in stock).

[ThomasW]

If you have the 'room' and can live with larger boxes, then you'll use up less of your amplifier power to the LT circuit.

Nope never seen anyone latch two boxes together, that of course doesn't mean it hasn't been done.

As Danish indicated, multiple boxes can actually be helpful smoothing out the in-room response. And they're certainly easier to move around.

[dyazdani]

As Danish indicated, multiple boxes can actually be helpful smoothing out the in-room response. And they're certainly easier to move around.

My one box 3.5 cu ft box will be 150lbs when I put the sub in it, but I guess that's "easier" than a 300lb box :E

[ThomasW]

Danish, thats why furniture dollys were invented .....:wink:

[Scott Simonian]

...and friends, Thomas.

[dyazdani]

Some of us don't have either... :cry:

Actually, my best friend can bench about 470lbs, so it's not really a big issue.

[engr_dave]

Thanks for the feedback

60L seems a little small for the RL-p15

Interesting. I was going from the SS website, which says, "we suggest a sealed enclosure between 1.5 - 2.5 cu ft, with the general consensus being that 2.1 cu ft net volume is ideal for a flat frequency response with good low-end extension and output" 2.1 cuft = 60 L, no? I understand Hoffman's law, but I figured that I have enough power to drive them to the excursion limit in any size box, there's no real advantage to going larger... except maybe lower distortion and/or power compression and more thermal headroom (is this an issue with the brief transients typical of movies?). Am I missing something here?

And they're certainly easier to move around.

Amen. How big a problem is a 100lb sub "walking" or buzzing against the wall?

I'm planning to do the same (once the RL-p15 is back in stock)

I didn't realize that they are out of stock. Is this a brief thing or should I look for another driver?

Dave

[ThomasW]

They'll be restocked in approx 2 weeks...

If you can use spikes they don't walk.

Most of the designs on the SS website had their origins in car audio. Slowly Mike is catching on and increasing box size to create lower "Q" designs, now that a bazillion people are buying the 15"s for home use.

If you have Excel on your PC grab a copy of Unibox and play around with different sized boxes. It let's you model input power, excursion, etc....

[---k---]

My sealed RL-p15 is ~100L. Unibox tells me, that with heavy fill, Q = 0.509.

[dyazdani]

I think they have the D4 models, but not the D2 - at least as far as the website suggests.

I read the same as you on the box size - but several reports from others say that Mike at SS suggests around a 4 cu ft enclosure. I'm glad Thomas gave a reason for the discrepancy.

[chasw98]

I'm running 7.5 cu ft with a D4 ported. It's tune to 17 Hz. Goes deep and clean.