Planning Budget LLT

[spidrman]

Been browsing here and have read about everything I can here on LLT subs. I've been playing with WinISD and different drivers in different sized boxes. So far it seems my best option is a dual Tempest Classic 15" in about 20 cu ft tuned to say about 12 hz. Here is what WinISD shows with only 200 watts input power:



This is going to be a large box under my screen. I can go up to 8 feet wide and about 30 inches high but my depth is limited to 18" deep (the distance from the wall to the front of the screen). I want to keep the drivers in the middle of the box so the output is centered between the mains. Would front firing or down firing be better?

The room is 12 feet wide by 22.5 feet long. The side walls go up 8 feet, then angle over to 45 degrees and continue up to 10 feet. The 10 foot central portion is about 6 feet wide.

Anyway ... I'm trying to keep my "initial" budget down to about $700 for this build including an amp. I'm looking at using the Nady XA-900 so I figure I need drivers around $150 each (the Tempests are on sale right now for less). Down the road I plan on adding a Behringer DSP 1124P but until the room is more complete there really is no point. The riser isn't done, I have yet to put up any acoustic treatments, etc.

I want to build the box for them in such a way that down the road I could upgrade the drivers if I wanted more output. But honestly I think this will be more than I need in my theater room (pretty much 100% HT use). Right now I have a tiny 10" sub so this will be a HUGE step up in performance.

Any thoughts on driver selection?

Thanks!!

[SteveCallas]

Tuning should be much higher for those drivers, I'd guess between 15-16hz without modeling it.

Also, the drivers don't need to be centered between the mains, as bass isn't directional. Your final placement should be a function of the in room FR at various locations.

[bonehead848]

something else I would consider if you are planning on upgrading anyways is to just buy one really nice driver, build your big dual box and plug the other hole. That way there is no money loss when you upgrade to nicer drivers and you only have to buy one. You will probably be shocked by the output of say, a single tc2000 or rlp15 compared to what you have now and be content enough to wait a while until you can afford another driver and amp.

[spidrman]

SteveCallas wrote:

Tuning should be much higher for those drivers, I'd guess between 15-16hz without modeling it.

Also, the drivers don't need to be centered between the mains, as bass isn't directional. Your final placement should be a function of the in room FR at various locations.

I actually chose the tune based on having better drivers later. WinISD actually doesn't show much change between 12 hz and 15 hz. At 20 hz the higher tune is about 1.5 db down and at 10 hz it's actually up 3 db. The curves cross at about 12.5 hz. So I guess since ports are cheap compared to the big picture if I can figure out how to put it together so I can replace the port later, I can use the more optimal tune now.

Wanting to have the drivers centered was more of an aesthetic choice since I'm limited on height and depth I figured front firing was going to be my best choice and having them centered I felt would just "look" better. But the sound quality is most important.

I'm assuming that I can test my room's bass response using my existing 10" sub by moving it around and the ideal spot for it will still be fairly ideal for the new one?

Since this is going to be a "wide" box, could putting a driver at each end work better ? Maybe even on the sides which would cancel their mechanical movement? Or will having them side by side in the enclosure work better? And if I put them on the ends, where would the best place for the port be?

Thanks again!

[SteveCallas]

I actually chose the tune based on having better drivers later

Hmm - unless you plan on going with dual 18s in ~700 liters each, your room is dorm sized, or you will build a multi driver SLLT, a 12hz tune is too low for ideal performance in my opinion.

WinISD actually doesn't show much change between 12 hz and 15 hz

You mention output at 20hz and 10hz - what about 13-20hz? That's the region where you will get your infrasonic performance from, not 10hz and below. Also, the output advantage you see at 10hz won't come to fruition due to excursion use and port compression. I don't want to sound like a wet blanket, but you are better off with the higher tune.

But the sound quality is most important.

If that is the case, I agree with bonehead. Instead of buying two cheapo 15" drivers, buy one good 15" or 18" driver. A TC 2000 15" or RL-p18 LLT will be a very dramatic improvement over any 10" sub.

[spidrman]

bonehead848 wrote:

something else I would consider if you are planning on upgrading anyways is to just buy one really nice driver, build your big dual box and plug the other hole. That way there is no money loss when you upgrade to nicer drivers and you only have to buy one. You will probably be shocked by the output of say, a single tc2000 or rlp15 compared to what you have now and be content enough to wait a while until you can afford another driver and amp.

I have no doubt that a single tc2000 would blow my existing sub out of the water. And now it appears that I did something wrong in my WinISD modeling. Here is a comparison of dual tempests vs dual RLp15s:



Both in the same 20 cu ft box. Tempests tuned to 15 hz (red line) and the RLp15s tuned to 12 hz (blue line). That big hump doesn't look good to me ... but then I'm a "noob" Originally I thought the RLp15s curve was closer to the Tempests.

TC-2000s look about the same in that size box and tune as the rlp15s. The TC-1000 looks just like the Tempests but actually wants more power to get the same SPL (again I'm a noob and may have done something wrong).

Most likely the Tempest's will never get replaced, so assuming that, does the concept seem sound going with the 15 hz tune?

[spidrman]

Geez ... I guess I should wait a while between my replies since I'm getting answers to my questions while I'm asking more.

Ok, since I'm the "noob" and Steve (and bonehead848) are the "experts", I guess I'll go the single driver route for now (actually make that forever ). Along with the higher tune. The RL-p18 would probably put me over budget but supposing that I could swing that, what size box and tune would you recommend for my room size? Also with the 18" driver I don't see the need for a second one later.

Thanks a mil!

[Jerm357]

If I ever get a RL-P18 Im going to get the duel 2ohm verson and put it in 22cf tuned to 14.5hz with a 8" port.

[SteveCallas]

650 effective liters with a tuning between 13-14hz would be great for the RL-p18. If going with a TC 2000 15", 320 effective liters with a 14-15hz tuning would do it.