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In the Forum: Audio Discussions
In the Thread: Romy The Cat's new Listening Room

Post Subject: Experiences with DEQ'd ULFPosted by jessie.dazzle on: 5/15/2010

El`Ol wrote:
"...And what about the brute force method (room correction for the bass arrays)? [Digital EQ]..."

Romy wrote:
"...Actually I am considering something like this... I think the final result might use some of your limp methods but the EQ ONLY for LF does not sound too absurdish as well... Let pretend that EQ does not destroy sound by DSP in case it is digital and does not spin phase... Still, flat response is not the objective. I have seen in some rooms very un-flat response that did not affect listening. Some peaks and some dives in the response are fine..."

Having less than ideal lower-bass response in my current room, I bought a single Velodyne SMS-1 as an experiment.

The idea was to use it only on the ULF channels, and to use it as sparingly as possible.

With more than two years of experience using this device I can say the results are impressive, and to my ear, non-destructive (it is possible to defeat EQ via the remote for quick A/B comparison). I say this while running the ULF channels higher (in frequency) than I will once the mid-bass horns are done.

As for phase, it is completely adjustable, though in my case it was not necessary (I left it at zero; ULF channels are sitting next to the main channels), and I see no difference when defeating the EQ; like all changes made, the results show up in real time via a graph/onscreen display (requires a television or projector).

As for flatness of response, I would agree with Romy; I left smaller peaks and valleys, and oriented the composite curve (all channels) to slope down gradually from the higher LF end.

From my experience, I conclude that if used intelligently, and only for ULF, the effects of this device are not destructive, at least not to the point where they are perceptible. Think of it as accepting to pixelate the blackest 10-15% of an image, while leaving everything else untouched. Defeating the EQ will convince you not only of the non destructive intervention, but also of how much the device is actually helping the situation. Given the right enclosures, armed with high-excursion drivers and adequate power, I cannot imagine a situation this device would not remedy.

Forget the auto-correction feature; it is crude and the result is not even close to what can be obtained using the manual adjusters. Also, I find the presets for different types of music to be of no interest; I use one setting all the time... Once set up, I don't touch the remote; don't even find it necessary to vary the volume of the ULF channels relative to the main channels.

Using the ULF channels in stereo requires daisy chaining two SMS-1s together.

One word of caution: This device is intended to be used with drivers that can handle a lot of excursion, and will permit asking a "normal" drivers to perform beyond their limit.

Unicon wrote:
"...You need to correct your fundamental room modes(below 100hz) by using limp mass acoustic..."

It is possible that I am currently using this technique without knowing it... I'm not entirely clear on what is meant by "limp mass acoustics", but I use several flexible polycarbonate panels onto which I've attached blocks of 4" deep wedge foam. The panels are probably not flexible to the point that they would qualify as "limp", but they are far from rigid. They can be suspended back to back in mid air, or mounted on foam supports. These devices make one hell of a difference, as I have a "polished concrete" floor, stone walls, a steel and glass ceiling, and very little furniture.

jd*

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