Axiom Home Page Forums General Discussion Advice from Axiom Owners Raised Floor question

I would then experiment with the placement of your mains from the back wall, side wall, toeing them in, etc... The drivers should not be the same distance from the side walls that they are from the front wall, for example. Also, the more you pull them out from the front wall, the better bass resonse you will get.

Are you running them as "small" or "large"? I received better results with my sub if it was "in line" with my main drivers and in phase. Sorry for the simple questions, I just find it hard to believe you have to reconstruct your floor, and I don't think that will resolve your problem.

Do you have a picture or drawing of the setup?

I have tried several positions of the mains in relations to the side wall and back wall. Currently they are 2 feet from the side walls, and about 2 feet from the back wall, and are 7 feet apart. I found that the minimum for good imaging and stereo seperation is 6.5 and the max is about 7.5, after that I lose the cohesiveness of the image. Now, I did catch in your post that the same distance from side and back is not a good thing.. I remember reading that, it re-enforces something or other ? anyways, I'll experiment some more with moving them away from the back wall. I don't have much more play in the side walls, but the back wall I can go right into the middle of the room if need be.

It's been many months of tweaking, moving things around, trying every crossover option I have, putting up traps, trying blankets on the wall at different locations like back of room, front of room, frz, floor etc..etc..I have done a LOT of experimentation but alas..hence my call to the pro, but before I head down that path I'm going to want assurances that it "will" fix the problem and not create more !!! my room size will diminish by almost half with the wall..so that may introduce more modes as they are typically more apparent in smaller spaces..I don't know..I did not get "all the answers" from my consultation session that I was hoping to get.

The reason I paid $200 bucks to have that guy in was to stop taking shots in the dark and get someone on site to evaluate the situation first hand. I was expecting more I guess, maybe my expectations were unrealistic.

Randy,

Can you tell me how you measured your room using RoomEQ Wizzard ? I have an SPL meter, which can double as a mic, I have an M-Audio revo sound card in my pc, but I don't know how to connect everything to actually record and map the room. The tech guy had a macbook with an Appogee MiniMe external DAC connected to a mic (xlr) on a stand. The sound was then recorded using a software similar to ETF or others like it. If I could just do it myself and experiment I could really map the entire room up, then I would have intelligent data to converse with you guys

Thank you so much

Stephane, the literature relating to bass reinforcement generally is the opposite of what you were told. Concrete absorbs very little of the bass energy and strictly from that standpoint a room with all concrete surfaces would be optimal. The more flexible the walls and other room surfaces, the more the bass energy is diminished.

I see what you mean, from a sound absorption coefficient point of view, carpet is 0.01 and concrete is also 0.01 for a total of 0.02 Now, 1 being the most absortive and 0.00 the least, it's clear that my thin carpet on my concrete floor is not absorpbing much. Mind you those numbers are at the 125hz frequency. I was not able to find any numbers for the low frequencies ie: 40hz to 90hz.

Typical drywall walls on 2x4 studs are rated at 0.29, quite a bit higher. Again that's at 125hz.

So, what you say makes sense, the floor is most likely not absorpbing the bass energy. I'm going to move the speakers around the room in completely different areas and see if I get different results.

Update.

I went home early, ie: before the rest of the fam, and moved my speakers / listening positions in places that I could never leave it that way, but I wanted to know.

Sound did not improve..BUT.. when I put everything back to the " way it was" my speakers were a bit further from the back wall and it sounded better, more bass.. So I played with that for about an hour and I got them in a position where they produce a very good amount of bass..the overall sound is not perfect, but more bass traps / treatments should take care of that..Point being that moving my mains further away from the wall(s) did produce a much better bass response, very acceptable indeed.. So, I guess I don't need to build a raised floor afterall .

The middle of the transducers are 26 inches from the side walls and 46 inches from the back wall.

I think I am starting to actually see the sound waves paterns of my room in my mind !!!!very scary.

Thanks Guys for all the helpfull advice and sugestions.

That is great Stephane! It is amazing how just moving your mains or sub a few inches to a few feet can make a dramatic difference.

Thanks Randy, I appreciate your feedback as always.

when you get a chance, could you tell me briefly how you did your sound measurements of you room ? I know you used the RoomEQ Wizard software, but I am curious as to which hardware you used and how it was connected together.

Thanks again,

Cheers,

Steph

I've used two products to just give me an idea. Keeping in mind, these are taken only from the primary listening position and would be different from other locations.

1) I downloaded the free test tones from the RealTraps website. The CD starts at `10hz and goes upto 300hz in 1hz increments every 10seconds. It takes some time to complete, but gives you a great idea as it includes all frequencies. Some test CD's like 1/3rd octave cd's don't show you the entire picture as they skip over important freq's.

I basically wrote down my results on a piece of paper, and then transfered them to an excel spreadsheet.

2) RoomEqWizzard - I got this off of HomeTheaterShack's website. You have to have a computer/laptop with a soundcard to run this free program. You basically hook up your RS SPL meters "output" connection to the input on the sound card to take the measurements. There is a little more to it, but that is pretty much all it takes. The instructions on the website and help file in the program take you step by step.

Actually, I need to rerun my tests since I've upgraded.

Thanks Randy,

I will give it a go.

Cheers,

Steph