Rotary Subwoofer Install Blog

September 26, 2006

We’re at the 2/3rd point… TRW’s have been powered up…read on for what happened!

Filed under: Uncategorized — bassment @ 10:41 pm

OK, it’s Tuesday. Just to close off on that RS-485 issue, I had to buy $250 of software and RS-485 adapter gimmicks from Schneider Electric (supplier of the TRW motor controllers)… all of which was worth about $25. Nonetheless, this will fix the HTPC to TRW command/control connection.

Onwards… the box was completed this morning as you can see below… the first two pics show the inside of the box. The fiberglass batting is transparent to sub 20Hz frequencies, but absorbs well the modest higher frequency noise that the fan blades stir up. The second pic shows both TRW’s ready to bite the air. The 3rd pic shows the manifold fully assembled. The 4th pic shows the view from the media room, looking at the front left ceiling corner… into the manifold area.

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Now the drywall guy is repairing our demo work… thanks Ramon and Javier for coming out on such short notice! You can see the manifold fully assembled, the TRWs in the back like cannons ready to fire.

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OK, so we fired up the TRWs around 3pm. I was a bit anxious… I just destroyed the air tight sanctity of my media room, demo’d a perfectly nice soffit, ceiling, introduced dust and soot everywhere, all in the pursuit of sub 20Hz bass. So this first power-up test better do show potential for massive performance… this first test better show that our concept for the design of the manifold would provide the sufficient opening into the room, and sufficient back volume to let the TRW’s fulfill their potential, all without disturbing the peace outdoors or in the house.

Bruce hooked up the 250W amplifer to the TRW speaker wires, his laptop output to the amplifier input, and started his pink noise LFE test. Mind you, this was at 1W amplifier output. The media room doors were open at the time… and the hallway wine cellar door started shaking like a ghost was inside and wanted out. I had to close the IAC sound door to stop that nonsense… now we know why we should always install very heavy sound doors… so that the TRW will be unable to shake the 300 pound door leaf from it’s magnetic seals. The SPL in the 1-10Hz range was already at 100+ dB, and this was at 1W of amplifier output power. Talk about efficiency.

Then I went to close the media office/bath exterior door, as at this time we were venting outdoors, just like in the BAAS test. This caused the back venting to be limited to the media room office, bath, and garage area. As well as some area between the media room walls and the concrete surrounding foundation. Bruce related that the output dropped 3dB. We moved upstairs into the garage to see how much power was being back vented, via the AC plenum chase. The concrete garage floor was shaking underneath us in certain spots. The garage doors were hitting against the framing. So I had another idea. I opened up the door into the attic, which created more back vent volume. This reduced the garage floor banging to almost zero, but still we felt the garage floor shake. Simply amazing, for 1W!

Tomorrow we continue to improve the manifold design to further reduce high frequency noise. It’s already acceptable noise floor for movies, perhaps not so in my ultra quiet media room for 2 channel, at least not yet. Also tomorrow, Bruce continues to EQ the TRWs, via the amp’s on board EQ system. We need less output between 1-10Hz and more between 10-20Hz. Simple matter of playing with fan speed and the EQ. We’ll get it there.

One final open issue is the finish of the various new openings in walls and ceilings… I am searching for a suitable grill that lets the air pressure changes pass efficiently, but that block the unsightly ceiling and manifold views.


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