Axiom Home Page Forums General Discussion Technical Questions Using an SPL Meter

Yeah Jason, Since I've gone to a 600 and twin 350's I never have a use for my Velodyne SMS-1 digital sub EQ system anymore. I'll most likely sell it soon.

I'm not quite sure how to parse these two sentences as they direcly oppose each other. My current understanding is that applying filters using something like BFD will only treat a specific position, where as treatments deal with the basic issues in the room IF chosen and placed properly.

Unfortunately, the options for treating frequencies below 100 Hz seem to be either very bulky, or very finicky.

If you have any suggestions based on the info I have posted on my room, I would love to hear them.

I think they are the same. Applying EQ is basically the same thing as applying filters. They both only benefit the location where you took the measurements with the mic or spl meter. Neither have to do with treatments, those address the entire room.

4" of Owens Corning 703 or equivelant stratling all corners, including floor/wall and ceiling/wall do very well below 100hz. I actually built "Super Chunks" in my front two corners, basically cut the 703 into triangles to fill the corners does better than just statling the corners.

From specs I have seen, they seem to taper off fairly steeply below 80Hz. That was not your experience?

I wish I had lots of corners to fill. Unfortunately, I only have one and onehalf vertical corners. That leaves me with only the ceiling/wall interfaces to work with.

I just installed the superchunks and reflection panels and enjoy. I'm basing off the research from Ethen, the owner of Real Traps.

Here are some of my results with NO REW filters or EQ on the receiver or SMS-1.




This picture shows how the overall response improved just by adding my superchunk bass traps, no wall panels yet.

Are you noticing an even greater effect across the room (multiple sweet spots) or is it mostly located where you already concentrated your efforts?

Adding multiple subs, bass traps, and first reflection panels, has improved the response across all seating locations. If you calibrate using REW or the SMS-1, etc. from the primary seat, your only benefiting that location.

Thanks for the graph. Its nice to see some real world measurements. Looks like the superchunks did some interesting things below 100Hz.

I guess I just need to go out and pick up some 703 or similar and do some testing. As a quick and dirty test I can just put a couple of bales above the aquarium at the front of the room and see what that does.

I have 4 subs with an SMS-1 processor and I would totally agree location and acoustics are the most important elements in getting the smoothest bass response. I would, however, submit that the SPL meter drops off significantly in accuracy below 50hz so you won't get an accurate reading of that REAL DEEP bass. This was confirmed in Ian Colquhoun's tutorial on the subject plus a number of other manuals. The advantage of the SMS-1 in this particular case, to my hearing anyway, is it enables you to pump up that deep bass(provided your subs can handle it) and in turn, turn the overall volume down slightly to compensate. Although sirquack's graph is showing generally a balanced response, especially with room treatments applied, the deepest bass(25-40hz) will be masked by the upper bass frequencies since the ear still can't hear these lowest of frequencies as well especially at lower volumes. A similar principle was applied to receivers in the recent past that had a "loudness" control. This is strictly my opinion and in the end, it's all about personal preference anyway.

The SMS-1 is a great piece of equipment, especially for one sub, or multiple subs nearfield. The problem is the EQ adjustments you make change the response for all the subs connected to the single SMS-1 processor. If you have the subs on 2 or 4 opposite walls, you would really need seperate SMS-1's for each sub, or purchase their higher end model that lets you have seperate EQ settings for each sub.

Fred, also keep in mind those changes on the superchunk graph was just by adding the front corner bass traps. I have not done the rear walls, or floor/wall, or ceiling/wall.

Your correct Casey on Ian's statements, I believe that is one of the reasons he does not believe in EQ methods, just following Dr Toole's paper.