VLA -- How Lo Do It Go???

PLMONROE · « **on:** 23 Nov 2007, 10:03 pm »

I have been trying to dial in my VLAs for the past couple of weeks. Do to room size constraints I have ended up placing them closer to the side walls than I would have liked. They each are now in from the end of the room about six feet, facing out at a forty -five degree angle, with the rear edge about six inches from the side wall. I made initial settings to the amps as per Brian's suggestions and the subs really purred! Some time ago George (Zybar) in one of his posts suggested to Dave (Housteau) that the Velodyne SMS-1s might be a great addition to the VLAs. So , although my room has extensive acoustic treatment, and figuring I might need all the help I could get, I purchased a pair. In setting things up I took my Phonic PAA-2 and made a lot of measurements at positions all around my seating position. I then used it to compute average equalization settings. Next I dug out on old Behringer UltraPro 2496, placed it in the system, and programmed in the settings from the Phonic. Darned if it didn't sound even better. Then I used the Velodnes automatic calibration feature to match the VLAs to the room. This produced another substantial improvement. At this point it was time to check it all out. Using the Stereophile Test Record #3 I took readings on the test tones from 200hz down to 20hz. The readings on my Quest SPL meter were all between 70 and 75 with a reading of 75 at 20hz. WOW! Being a Doubting Thomas, I downloaded the Test CD from realtraps.com that gives tones at one hz increments. I took 190 readings, one hz apart from 200 hz down to 10 hz. Boy is running that a PITA! However it confirmed the previous test. Every reading between 200hz and 20hz fell in the range of 80 plus or minus 5 as measured with the Phonic. I did not find a hidden peak or valley anywhere. The readings gently rose and fell within that range of values. But how lo do it go? Weeelllll, Using the Phonic, I got readings of 84 at 30hz, 83 at 25hz, 83 at 20hz, 81 at 19hz, 78 at 18hz, 75 at 17hz, 73 at 16hz, 67 at 15hz, 61 at 15hz, and 55 at 14hz. Those suckers will go below 15hz! My 14 year old grandson, who has ears like a cat, could tell when I turned the 15 hz tone on and off (but not the 14hz one). I understand the lowest note anywhere in music is the 16hz note of a pipe organ. If that's true, I guess the VLAs could be said to be reasonably adequate for most peoples music systems?

[Hay John, is that subterranean enough?]

Paul

John Casler · « **Reply #1 on:** 23 Nov 2007, 10:41 pm »

WoW!!

Seeing how long a 14Hz tone must be, maybe you could hear it more clearly someplace else in the house.

Did you have all the doors and windows open when performing the tests?

That helps reduce standing waves.

Brian Cheney · « **Reply #2 on:** 23 Nov 2007, 10:48 pm »

Paul's results are consistent with my nearfield measurements (taken 4" off the floor and 3" in front of the front baffle). I'm glad these jibe with his in-room measurements.

With the PR's properly tuned harmonic distortion at 20Hz/1W measures 1.7%!.

Brian Cheney · « **Reply #3 on:** 24 Nov 2007, 03:28 am »

14Hz is a subsonic frequency and should not be audible by ear anywhere.

It can, however, be perceived by the body and bone structure and has been used in the past as a weapon of psychological warfare. Prolonged exposure to subsonics imparts a strong sense of dread or foreboding to someone unaware of their presence.

Housteau · « **Reply #4 on:** 25 Nov 2007, 08:03 am »

"Some time ago George (Zybar) in one of his posts suggested to Dave (Housteau) that the Velodyne SMS-1s might be a great addition to the VLAs."

I did consider that, but instead chose to keep my signal chain as simple as possible. It was already getting a bit complicated being triamped and with two sets of those amplifiers as mono blocks. So, I allowed the room, treatments and speaker placement to dictate my final rewards. Fortunately the VLAs integrated into my room as no other bass system had done before. Previously measured peaks and valleys had been minimized by the nature of how my room was being energized by these monoliths.

Through design the VLAs do naturally roll off higher in frequency than one would think a high quality subwoofer system like this should. But, I understand that this was done to maximize the other performance parameters that are even more important, and this compromise brought them up to exceptional levels. Besides, with the included single band of parametric EQ on the supplied amplifier used properly, the lower registers can be smoothed out to just below 18Hz.

That is what I ended up doing. Since I didn't really have any major peaks to deal with, just a few dips, I used that single band of EQ to correct the natural roll off of the bass towers. I am down 3db at 18-19Hz where things roll off pretty quickly after that.

PLMONROE · « **Reply #5 on:** 27 Nov 2007, 04:04 am »

If I had been blessed with Dave's elegant and spacious sound room (and in a separate structure yet) I probably would have relied only on treatments as a way to achieve my ends as well. But alas that was not the case. What is interesting is that he and I were able to accomplish essentially the same results but did so by going in completely different directions. It is to the Brian's credit that the VLAs have such fantastic flexibility as to allow us both to succeed while on such different paths.

Paul