Yet another LLT build

[Leonardo]

Greetings all. Long time, first time.

I plan to build an LLT Sonosub. My current sealed Tempest 15" is not gettin' it done any more.

Here are my constraints:

• 8 foot ceiling and a tolerant spouse. (I used 7' endcap-to-endcap as a design limit; I am willing to use a grille on the top if I need the volume)
• The room is ~ 1900 cu ft with one standard door
• Up to 24" tube diameter (would prefer 20 to leave more room for a 16x9 screen, plus I think it would look better)
• Samson S1000 power amp (2x500; minimum of 4 ohms per channel)
• Would like to tune to 14 Hz

I read here that the Tempest is not suitable for LLT and that's OK. It looks like the RL-P15 (or 18) is a popular choice. Are there other drivers I should be looking at in the same price range?

I've been playing around w/ the RL-P15 (4 ohm) using Sonosub and UniBox. WinISD not so much.

Am I on the right track here?

• For a 7' x 20" tube (371 l), a 36" x 8" port yields 15.8 Hz. Not an LLT.
• For a 7' x 24" tube (500 l). a 36" x 8" port yields 14.1 Hz. I think UniBox says excursion is 30mm @ 20Hz. (Xmax is 26). Is this excessive and if so, how do I fix it? Peak port air speed is 36 m/s @ 13 Hz. Does this mean I need a larger port?
  

I don't have a good feel for what I'm shooting for in the response graphs, nor how to "move the line" (more power? bigger driver?)

I hope I've listed enough info here. Any help would be much appreciated.

[mrstampe]

As far as other drivers to consider, how about the SDX15? It seems like a great "boom-for-the-buck" and others on the Shack have had very successful builds with it.

SDX15 subs
Eric's sonosub
Geoff's Dual SDX15
SDX15 to RL-p18 comparison discussion
SDX15 main discussion thread


Funky Waves has it for $279(US) or $259(CAN) with free s/h.

[brent_s]

First, welcome to the Shack.

This is one of the reason why I prefer WinISD. You can overlay multiple designs directly on top of each other to compare performance directly. Not to mention Unibox requires Excel, although some have said it works on the latest OpenOffice release.

Anyway...have you considered simply rebuilding your current Tempest into a ported alignment? 1900 ft^3 is not a lot of volume to fill. I've got a DVC15 (virtual clone of your Tempest) in 5.9 ft^3 net tuned to 17hz. With REW and a 100dB sweep, it measures essentially flat down to 10hz in my 24x16x9 (3450 ft^3 gross) theater room. Everybody's idea of loud enough is different...generally we listen 10-15 dB below reference, but I have run a few big bang demo scenes at reference level without any audible distress. Measurement/listening position is about 7' to the corner loaded sub.

If you're set on replacing the driver completely, I would first model you're current build and do some REW measurements to understand how theory is translating to reality in your space. Using this data, you'll also have an idea of how much room gain you're getting. For instance, I get 7-10dB of gain at 20hz so I'd have a pretty bass heavy sub if I designed for flat to 20hz.

With WinISD, you could then quickly overlay optional alignments directly on top of your current sub to see the advantages.

The Tempest-X from DIYCable is the current budget leader of high displacement drivers and was designed by Dan Wiggins, the same man behind your original Tempest. The other usual candidates are the Creative Sound's SDX15, the Soundplinter 15/18, if they're available, FiCarAudio's 15/18 models (IB a possibility?), and Mach5audio's 18 offerings. John at AESpeakers is also getting back into the DIY market, but doesn't have much information listed yet.

-Brent

[Mike P.]

As for the "over excursion" in your modelling, lower the input power until xmax says 26mm. That's as far as you should push the driver. You will also notice that port speed drops to 28m/s.

[Leonardo]

mrstampe:

Thanks for the links. I'll definitely put it on the list.

brent:

I didn't realize you could overlay models in WinISD. Looks like I need to buckle down and learn how to use it.

The sealed Tempest has been taken apart and the cab discarded, so REW is out for the moment. I didn't think the Tempest was a good choice based on comments by stevecallas, but will definitely compare it vs. your other suggestions using WinISD.

IB is out given the way the house is configured.

BTW, I actually measured the room this morning and it's 3000 ft^3 instead of 2000. So much for my estimating skills.

Thanks for taking the time to respond.

Mike: Point taken about limiting the power.