LTD-M18 Sub Build - Page 19 - AVS Forum
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post #541 of 548 Old 07-30-2014, 01:50 PM
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Jbrown how tall is your stage?
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post #542 of 548 Old 07-30-2014, 01:59 PM - Thread Starter
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10"

My Gear:

JTR Noesis 228HT (LCR)
Axiom Audio QS8 surrounds
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post #543 of 548 Old 07-30-2014, 02:08 PM
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see posts #15 and #16 in this thread:


LTD-M18 Sub Build


with 1/4 distance WIDTH placement, i.e. placing the subs at position 25 and 75 in the picture above does this:
mode 1: canceled, because half the subs are in blue, half are in pink.
mode 2: not excited, because all subs are located in velocity zones which do not couple to the room.
mode 3: canceled, again, half the subs are in blue and half the subs are in pink, though in this case the placement only partially couples to the room
mode 4: excited. however, the fourth order mode tends to be pretty far down the list in terms of being able to he heard. i.e., it tends not to be too offensive or have too much impact on frequency response.


with 1/4 distance HEIGHT placement, all that same stuff remains true again, but with respect to the HEIGHT modes.


the only modes left are from the front wall to the rear wall. best to treat the rear wall with fiberglass (set some distance out from the wall) or a limp mass tuned and placed on the wall itself.


or, you may get lucky and be able to use eq for the final fix depending on where and how many rows of seats you are working with.

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post #544 of 548 Old 07-30-2014, 02:44 PM
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Quote:
Originally Posted by jbrown15 View Post
So here was two measurements that we took yesterday while BassThatHz was over. The red graph is the screwy way that I had the amps setup and the blue graph is basically with zero boosting applied and just having a high pass filter in place to protect the drivers. Basically you can see that I was bottlenecking the subs and robbing them of output.
Oh there's also zero smoothing applied to the graphs.


I still think you could squeak out some more db's below 20hz if you buy a miniDSP.
The inuke is limited to 20hz, which isn't ideal for a ported sub that goes to 12-13hz.

If you are feeling more adventurous, you could apply the follow 2 DEQ's to all 4 channels (ie subs).

This will make the subs sound more aggressive at lower SPL's, so I don't think it would be too risky,

but you should optimize your gain structure firstly, like I mentioned in the GTG thread.
Or at least change your XO to this and increase your AVR sub-out back up to 0db.
or at least -5db in each would be the middle ground. That would still leave you 5db of risk-free boost in the AVR to avoid digital clipping.


When I first saw that his subs were rolling off like a rock at 23hz I instantly knew something was wrong (bad DSP settings or bad box tune), luckily it turned out to be the DSP settings.

He was running a +7db HS12 @ 20hz, which makes everything above 20hz 7db hot, but he was also running a 20hz HPF which made the <20hz even weaker.
Basically he turned his $6000 subwoofer-system into a Bose-module with that one DSP filter. (Just giving ya a hard time... LOL!!! )
The DEQ settings listed above is the correct way, and less-risky way, to boost below 20hz with the inukeDSP (rather than with a PEQ).

Last edited by BassThatHz; 07-30-2014 at 02:49 PM.
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post #545 of 548 Old 07-30-2014, 03:09 PM
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Here is the chart with mic corrections and the native no-DSP blue response added.


His system is -3db @ about 12.5hz, that includes whatever room-boost he may be getting.

So with a miniDSP he could probably squeak out another 4db at 12hz, perhaps not worth the $130.
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Last edited by BassThatHz; 07-30-2014 at 03:13 PM.
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post #546 of 548 Old 07-30-2014, 04:47 PM - Thread Starter
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Shawn, I actually have a miniDSP. I just need to get around to getting some cables to hook it up. I plan on using it to EQ the subs and not even use the DSP function in my amps. I'll let the miniDSP take care of everything. I'm actually thinking about changing amps for the subs anyways.

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JTR Noesis 228HT (LCR)
Axiom Audio QS8 surrounds
Sherbourn PA 7-350
Pioneer VSX-21TXH
JVC RS45
Falcon Screens FVHD105
Dual PSA XS30's (gone but not forgotten)
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post #547 of 548 Old 07-30-2014, 06:42 PM
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"The inuke is limited to 20hz, which isn't ideal for a ported sub that goes to 12-13hz."


a shelf filter can be used to push the high pass as low as one likes...


How to extend the high pass filter below 20hz in DCX2496

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post #548 of 548 Old 07-30-2014, 06:44 PM
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"He was running a +7db HS12 @ 20hz, which makes everything above 20hz 7db hot, but he was also running a 20hz HPF which made the <20hz even weaker.
Basically he turned his $6000 subwoofer-system into a Bose-module with that one DSP filter. (Just giving ya a hard time... LOL!!! )"


the HS12 should have been set at about "-4db @20hz ". that would provide a high pass filter around 16-17hz and would be a good start for examining woofer control.

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