Room Acoustics

[jim1961]

What I am drawn to first looking at your graph is the lack of bass extension. Its looks like your 10db down by about 70hz, and have almost nothing below 60hz.

As far as acceptability, surely this depends on standards you set for yourself. But for me, +/-5db in the bass region I consider pretty good. +/- 7db acceptable.

[theteach]

I think the roll off is the nature of the speakers. I'm using KRK RoKit 6 speakers without a sub. Most of what I work on in in the acoustic rock genre so I don't feel like I need tons of low end.

The null at roughly 64 Hz is definitely a room issue. If I move the mic that null moves. Any advise would be great.

[Jens Eklund]

Originally Posted by jim1961

But for me, +/-5db in the bass region I consider pretty good. +/- 7db acceptable.

Important when throwing numbers around, is to also include the assumed resolution. If 1/24 octave resolution (what we normally use when looking at FR curves); a +/- 5 dB swing through the FR (including the lowest octaves) is exceptional by any standards and a +/- 7 dB is still very good. The median notch depth found by Genelec when evaluating 164 professional control rooms was -14,2 dB, -20 dB or deeper was not uncommon … The deepest notch below about 150-200 Hz is often related to the floor bounce.

Also important to remember is that the FR curve is usually the least interesting one. The ETC and decay plots are usually the most revealing ones.

[jim1961]

Originally Posted by Jens Eklund

Important when throwing numbers around, is to also include the assumed resolution. If 1/24 octave resolution (what we normally use when looking at FR curves); a +/- 5 dB swing through the FR (including the lowest octaves) is exceptional by any standards and a +/- 7 dB is still very good. The median notch depth found by Genelec when evaluating 164 professional control rooms was -14,2 dB, -20 dB or deeper was not uncommon … The deepest notch below about 150-200 Hz is often related to the floor bounce.

Also important to remember is that the FR curve is usually the least interesting one. The ETC and decay plots are usually the most revealing ones.

Yea, I thought about better defining what I meant after I posted, and then got sidetracked by something else. Yes, 1/24 octave is what I use, but I usually leave out the last octave (20hz-40hz) for my +/- numbers.

So, id say:

+/- 5db, 40-250hz @ 1/24th octave smoothing is very good
+/- 7 db 40-250hz @ 1/24th octave smoothing is acceptable
+/- 9 db 40-250hz @ 1/24th octave smoothing is marginal

[Jens Eklund]

Originally Posted by jim1961

Yea, I thought about better defining what I meant after I posted, and then got sidetracked by something else. Yes, 1/24 octave is what I use, but I usually leave out the last octave (20hz-40hz) for my +/- numbers.

So, id say:

+/- 5db, 40-250hz @ 1/24th octave smoothing is very good
+/- 7 db 40-250hz @ 1/24th octave smoothing is acceptable
+/- 9 db 40-250hz @ 1/24th octave smoothing is marginal

Below 40-50 Hz (except perhaps the floor bounce) is the trickiest part ...

[theteach]

Okay so the million dollar question is do I have a problem? Do you need more info? If there is a clear problem what should I do about it? Thanks again for your help.

[jim1961]

Originally Posted by jim1961

What I am drawn to first looking at your graph is the lack of bass extension. Its looks like your 10db down by about 70hz, and have almost nothing below 60hz.

Originally Posted by Jens Eklund

Also important to remember is that the FR curve is usually the least interesting one. The ETC and decay plots are usually the most revealing ones.

[akebrake]

Originally Posted by theteach

Okay so the million dollar question is do I have a problem?

As you've sent a REW file to this forum it seems like you are concerned.
Nice start! What problems do you experience?

Do you need more info?

You guessed it! A layout sketch over the room, speaker placement some more info about the building. Wood, concrete, glass, doors. Preferable some photos.

Best

[Glenn Kuras]

Originally Posted by theteach

Okay so the million dollar question is do I have a problem? Do you need more info? If there is a clear problem what should I do about it? Thanks again for your help.

From looking at the waterfall I would say it "looks" good but "looks" are only that. When you mix, does it translate well when played on other systems? Any surprises? If not then "get back to work".

[theteach]

My mixes translate well but often I listen to them on several systems in other parts of the house before I commit to them. I don't have any major concerns but I've always read that one of the most important things to invest in is room treatment and I currently have none.

I'll try to draw up a floor plan tonight and take some photos. Thanks again to everyone for their help.

[Glenn Kuras]

Originally Posted by theteach

My mixes translate well but often I listen to them on several systems in other parts of the house before I commit to them. I don't have any major concerns but I've always read that one of the most important things to invest in is room treatment and I currently have none.

I'll try to draw up a floor plan tonight and take some photos. Thanks again to everyone for their help.

Actually I just downloaded your zip file and saw a few things.
1)Your monitors seem to start to cut off at around 100hz which might be pretty hard to judge what is going on in the low end.
2)Seems to be a lot of strange stuff in the mids and highs which is common for a small room.
I would still treat the corners with bass trapping and if nothing else treat the early reflection points to start off.
Video: First Reflection Points

[akebrake]

Originally Posted by theteach

I've just rearranged my studio based on reading threads here and on a few other forums. The room is approx. 10'9" wide by 16' long with a 86" ceiling. The listening position is about 6' from the shorter wall with the speakers about 2'6" from the wall. ..

The distance between the loudspeaker and the short wall (behind the speakers) is 2'6 which corresponds to 1/4 wave length at 113 Hz.
Speed of sound: 1130 ft/s ; 1130/4/2.5 = 113

This frequency will be out of phase with the direct sound at the listening position and probably causing part of the dip around that frequency.

Try too move the speaker closer to the front wall and see if the hole in the LF response between 100 - 150 will be a little less deep.

Cheers

[akebrake]

I just did a fast check of your REW files. There are two measurements. How are they measured?
Left and Right one each or together? Are there a table or shelf close to the speakers? What was the microphone height?

Best

[theteach]

If I remember correctly the two measurements were done with slightly different mic position to see if the big dip was part of a standing wave null. Each measurement was done with the mic at ear height. The speakers sit on my desk with my computer monitors in between them. I'll try to take some pictures tonight and make a drawing of the layout of the room. Thanks again.

[jim1961]

Originally Posted by Jens Eklund

Below 40-50 Hz (except perhaps the floor bounce) is the trickiest part ...

Subwoofer response in room

How about +/- 3db from 18hz - 180hz @1/24th smoothing at listening position ?

In my case, I am finding the floor bounce infinitely more of a challenge.