Going LLT from sealed

[Blaser]

I notice more and more poeple convert to LLT despite being very large. It seems the benefits of LLTs are more meaningful than their inconveniences...

[fireanimal]

I would be able to use an adjacent room to my theater to have the box in.

When I biuld this box, would it be benificial to leave the 4 MJ18's installed, and use all at the same time??

Thanks.

[SteveCallas]

You'll only be robbing yourself of low end if you use the MJ18s in conjunction with the IB18s in ported form - unless you want to apply extreme EQ to the MJs so they are flat into the low teens and run them at a very low level.

[fireanimal]

okay, I will update as I progress. Thanks for the help so far.

[fireanimal]

I plan on moving the sound treatment from this wall, and installing the subs in a vertical array, Sub Vent Sub with the enclosure on the other side of the wall. My current subs are installed in the enclosure under the screen.

[SteveCallas]

Be sure to beef up the wall area used as the baffle - I see too many IB installations with what I would consider very thin baffles as compared to box or sono subs.

[Rodny Alvarez]

Another thing... braces, make sure you brace the box real good!!!
If you can put some braces out side of the box!!

On my front bafle I used two 3/4" MDF plus one 1/2" MDF and the 1/2" plexi and the 2x4's










Here you can see how I built mine........
http://www.hometheatershack.com/foru...ilding-ib.html

http://www.hometheatershack.com/foru...-makeover.html

[jeffreybehr]

Fire, based on the curve you posted 03 April at 10:39AM, I think you're getting excellent response in the lowest (15 - 30Hz) octave. If your SW system doesn't have a powerhandling limitation, and since you already own an amp with a lot of DSP in its frontend, in the amp I'd add a broad rise (starting at c. 2dB and working up gradually) centered at c. 15Hz and a cutoff slope below that, starting at maybe 12Hz.

Also consider running your amp and speakers in stereo, driving 2 groups of drivers with a net impedance no lower than 2 Ohms. If you've already wired the 4 drivers in 2 groups of 2 drivers in parallel, driving them in stereo will be easy. The output impedance of the amp's 2 channels is half of the amp bridged into mono. The amp will dump a kiloWatt per channel into 2 Ohms, so lack of power should NOT be a problem.

BTW I've ordered one of those 2000s for my new IB super-SW project; it should be here next week. I'll be using at least 6 and maybe 8 Sonic Craft SC300 12" woofers backing into my attic. I live in Phoenix, and it's already almost summer, so this'll be a fall project (in Phoenix, 'fall' starts in November), but I'm getting really excited about it in spite of having 2 new SVS PC-Ultras in the room.

[fireanimal]

jeffreybehr wrote:

Fire, based on the curve you posted 03 April at 10:39AM, I think you're getting excellent response in the lowest (15 - 30Hz) octave. If your SW system doesn't have a powerhandling limitation, and since you already own an amp with a lot of DSP in its frontend, in the amp I'd add a broad rise (starting at c. 2dB and working up gradually) centered at c. 15Hz and a cutoff slope below that, starting at maybe 12Hz.

Also consider running your amp and speakers in stereo, driving 2 groups of drivers with a net impedance no lower than 2 Ohms. If you've already wired the 4 drivers in 2 groups of 2 drivers in parallel, driving them in stereo will be easy. The output impedance of the amp's 2 channels is half of the amp bridged into mono. The amp will dump a kiloWatt per channel into 2 Ohms, so lack of power should NOT be a problem.

BTW I've ordered one of those 2000s for my new IB super-SW project; it should be here next week. I'll be using at least 6 and maybe 8 Sonic Craft SC300 12" woofers backing into my attic. I live in Phoenix, and it's already almost summer, so this'll be a fall project (in Phoenix, 'fall' starts in November), but I'm getting really excited about it in spite of having 2 new SVS PC-Ultras in the room.

My subs are power limited right now, at around 20hz they are bottoming out, so I have a high pass filter in place to protect the drivers, which is also lowering my 10-20 hz output. That is why I want to go LLT, so I don't have to EQ the bottom end, which requires a lot of power and driver excursion.

I am also considering going with a berhinger and PLX3402 combo over the Xti.

[fireanimal]

After doing some experimenting with a PLX1202, I have found out that it was the XTI1000 that I currently have that was clipping, and not the drivers bottoming out. The funny thing is on the Xti the clip lights never flashed when I heard the sound, but when I drive the PLX to the max, the noise occurs at the same moment as the clip light.

Also the PLX is rated at 200 watts less then the XTI, but I was able to push the subs a lot further with it.

After finding this out, I don't think I will need to go LLT, and will be looking into a larger QSC amp and a FBQ2496.

Thanks for all the help this far.

[SteveCallas]

Booo

[fireanimal]

SteveCallas wrote:

Booo

I understand the disapontment.....But this actually turned out well. Also I am only using the 1200 watt PLX1202 at the moment, and will soon be getting the PLX3002 to up the max SPL at the bottom, it clipped on the last run for 117db at the listening position.

Here are the filters that I am using.


Equaliser: FBQ2496
Apr 17 13:25:38
Cutoff 80Hz 24dB/Octave
Target level: 80.0dB
Filter 1: ON PEQ Fc 21.7Hz Gain 4.5dB BW Oct 0.250
Filter 2: ON PEQ Fc 399.0Hz Gain -15.0dB BW Oct 10.0
Filter 3: ON PEQ Fc 43.3Hz Gain -15.0dB BW Oct 0.750
Filter 4: ON None
Filter 5: ON None
Filter 6: ON None
Filter 7: ON None
Filter 8: ON None
Filter 9: ON None
Filter 10: ON None
Filter 11: ON None
Filter 12: ON None
Filter 13: ON None
Filter 14: ON None
Filter 15: ON None
Filter 16: ON None
Filter 17: ON None
Filter 18: ON None
Filter 19: ON None
Filter 20: ON None

[Blaser]

I am pretty sure you would have had more "free" output from an LLT... (I am talking 130 db here in my setup ) But anyway, nice you have found out what the problem was...I have mentioned that so many times, power cannot harm subs easily on program material, but it can help a lot.