Question for Wes

Posted: Mon Aug 02, 2004 1:02 pm

I'm about to build a tracking room in an inner patio, aside my control room. I'd like to have a good ratio, so I can use this room to track drums, guitar, vocals, etc.

The main problem is the available space... it's simply too small. One of the sides of the room will have to be 2.69 m (8.83 ft) This is the space I have available, period (Neighbor on one side, garage on the other side).

Considering a healthy ratio (1:1.14:1.39) that would make it:
2.69 m : 3.07 m : 3.74 m. The problem is I can't extend all the way to 3.07 m, at the most I could use up to 2.90 m. Because I'm considering the actual measure to the exterior wall: about 3.10 cm, which is what I've got available.

The 3.74 m would not be a problem. This would be a pretty tall ceiling (12.27 ft) for the room, but that's ok.

So what do you think of these measures: (8.83 ft : 9.51 ft : 12.27 ft)??

Also, someone recommended I made an angled ceiling to minimize fluttter echoes. But at this height (12.27 ft) I wouldn't like to go taller on one side and then angle down from there (e.g. 13.30 feet to 11.30 feet)

Is it the same it I build it something like 12.27 ft to 10 ft.??

Any help will be very very much appreciated!!

Thanks,

Rodrigo Montfort
Monterrey, Mexico

Posted: Mon Aug 02, 2004 11:43 pm

Rodrigo,

Thanks for your question:

Quote:

I'm about to build a tracking room in an inner patio, aside my control room. I'd like to have a good ratio, so I can use this room to track drums, guitar, vocals, etc.

The main problem is the available space... it's simply too small. One of the sides of the room will have to be 2.69 m (8.83 ft) This is the space I have available, period (Neighbor on one side, garage on the other side).

Considering a healthy ratio (1:1.14:1.39) that would make it:
2.69 m : 3.07 m : 3.74 m. The problem is I can't extend all the way to 3.07 m, at the most I could use up to 2.90 m. Because I'm considering the actual measure to the exterior wall: about 3.10 cm, which is what I've got available.

The 3.74 m would not be a problem. This would be a pretty tall ceiling (12.27 ft) for the room, but that's ok.

So what do you think of these measures: (8.83 ft : 9.51 ft : 12.27 ft)??

Not to worry. Changing the middle dimension from 3.07 m to 2.9 m will not adversely affect the modal response of the room that much, down in the range where it matters.

Here's why, from a modal/ musical perspective:

The outer dimension is a slight variation of one you see all the time. It's the old tri-tone, devil's tone, augmented 4th, or whatever you want to call it. In equal temperment, it's actually 1 : 1.414..., or the square root of 2. In just intonation, one variant is 1 : 1.4, or the ratio of the 5th harmonic to the 7th harmonic.

(We aren't concerned with coincidences up in the range where the 5th harmonic of one dimension coincides with the 7th harmonic of another dimension, since this happens in the midrange, and modal theory is only concerned with the bass range.)

When I encounter a ratio like 1 :1.39, what goes through my mind is "a very slighty flat augmented 4th". An augmented 4th is a perfect dichotomy musically, because the two keys are diametrically opposed, or polar opposites, if you prefer. The two keys are as far apart as is humanly possible within the 12 tone system. So if you are trying to spread out the bass response across as many keys as possible, this is a good start.

(As to whether it's 1.414 or 1.4 or 1.39: Most people can't easily hear the difference. The 12 tone system requires that we constantly make much bigger compromises than this just to form a major or minor triad, and unless you are a piano tuner or classical virtuoso, you are unlikely to be listening beyond this level of resolution.) Anyway, you are not changing this outer ratio of 1 : 1.39.

So now we look at the new middle dimension. It actually has two ratio relationships: one to the shortest dimension, and one to the longest dimension.

On the short side, your new ratio of 1 : 1.08 is not the end of the world by any means. The ratio of 1 : 1.14 is a sharp sounding major 2nd, like a C t a Bb. (We're going down, remember, since 1.14 is a lower note than 1.) Changing it to 1 : 1.08, it's still bigger than a minor second (my theoretical cut-off point for closeness, since we live in a twelve tone culture). The harmonics between the two modes will not line up anywhere in the bass region, and a wide minor 2nd is too far away to resonate.

On the long side, 1.08 : 1.39 is a "hidden" ratio between the middle and longest dimensions of 1 : 1.29. (Your original starting ratios, 1 : 1.14 : 1.39 also contain a "hidden" ratio of 1 : 1.22 between the middle and longest dimensions. This 1.22 is a good and flat, "bluesy" major third. That's fine, but sharper - equal temperment - major thirds are also highly recommended and have gotten a lot of publicity. Bottom line is that the major 3rd range of ratios is a good range to be in.)

The ratio of 1.08 to 1.39 is 1.29, our new "hidden ratio". This is somewhere between a major third and a perfect 4th. It may be a very sharp sounding major 3rd, but it's still far enough away from the perfect 4th. (Perfect fourths are bad because you are in neighboring keys, instead of diametrically opposed keys, so you have lower frequency coincidences.)

But at 1 : 1.08 you are still far enough away to avoid a musical coincidence, or resonance. Now we're talking about a tuning difference that anyone can hear, and your room's ability to resonate at close ratios isn't all that different from the average person's ability to discern its resonance, in terms of close ratios, in the big picture.

So you still have an ideal set of outer dimensions. The middle to long ratio is between a major third and a perfect 4th. Your middle to short ratio is getting closere to a minor second. In both cases you've compromised, but not sold out. You haven't created any resounding renonances, if you will.

If you treat your room well, it should sound fine. At that size, you'll need to trap it pretty heavily anyhow, and that helps to widen the Q and lower the volumn of room resonances.

--Wes

Posted: Tue Aug 03, 2004 5:12 pm

Wow!!

Thanks for such a complete explanation! It's a bit complex for me, but as long as it's clear that the bass frequencies won't build up on certain notes more than others, that's great.

I'm aiming for a balanced, natural sounding room. If I'm able, I'll get a bit closer to the original ratio vlaues. Maybe a slightly larger middle dimension (say,9.70 ft) , and I will try to respect the long dimension with a tall ceiling that tilts (perhaps 12.6 ft down to 11.25 ft). Would you recommend a tilted ceiling at all? Or is it best to have a flat ceiling with acoustic treatment to minimze flutter echo?

I should probably mention that I really appreciate this forum for its experienced people willing to share their knowledge. Thumbs Up

Thanks,

Rodrigo

Posted: Tue Aug 03, 2004 5:33 pm

Rodrigo,

Sorry I forgot to address the issue of sloping the ceiling. You can do that, and if you do, just measure the ceiling at the mid-point, for the purpose of figuring the modal ratios.

--Wes

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