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Old 29th August 2018
  #131
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Quote:
Originally Posted by scraggs View Post
anyway if i can get in a couple questions for Thomas before the ax falls on this:

1. how much attention do you pay to the FR above say 500hz? i ask because as i said earlier, simply moving my empty chair would change the measurement. and also, according to the graph, i have a general dip in the response between about 1 and 3k. but it doesn't sound like that at all, i've had the same speakers for 12 years and they sound the way they always have, just way better and more detailed. and actually any hi mid harshness jumps right out of the speakers and is really obvious.

so i don't think this is a problem at all, other than i'd like my graph to look prettier, just curious to hear your thoughts on this.
If you witness a room measurement (which always happens after a first critical listening session) you will see that the first thing I'm literally sweating about and can't wait to see is the ETC data and then look at the 20-200Hz frequency response. If that's where it's supposed to be - and I always double check the floor effect too - because of how these rooms work the rest is de facto OK too. So I'll concentrate on that first, and then later move up on the FR.

If the room is empty of furniture and equipment (which is always the case when we do a room certification) you will see some fairly gentle comb filtering happen in the MF, due to the floor. That's normal and it will change as you slightly move the mic around. The dip you have may be due to desk reflections. At least that would be the first thing I'd look into. But if it's not really an audible problem... Moving a chair near the mic definitely influences the measurement. In critical measurements, I will delay the sweep start and go hide in the studio's entrance door frame to prevent my body from altering the measurement by being too close to the mic.

So LF>MF>HF when measuring a room.

Quote:
Originally Posted by scraggs View Post
2. is off topic, but i'm not sure what the topic even was, other than a vehicle for dan to argue stuff he doesn't have any direct experience with, so here goes: in your rooms with the glass front walls, like J. LaPointe's, how do you handle the front wall trapping? is the lounge on the other side of the glass serving as a big bass trap? and/or there's stuff (secret or not) in the walls of that room?

thanks!
Ha!

The glass front wall basically being acoustically an extension of the ATC front baffle, in itself all it needs to be is very dense and non-resonant / dampened - and it also acts as a soundproofing interface between the two spaces. So the glass is really heavy and thick. I'm sure J still has fond memories of the install day and all the weight lifting. The detail that makes it work 100% is that speakers are fully decoupled in the nacelles you can see on photos, which are suspended on cables who are then are attached to a 2 axis push-pull spring system with an added dummy load to optimize the tension and natural frequency of the system in the Z axis, and a pre-constraint spring system in the Y axis. The outer box of the nacelles is simply holding in the glass and seals around the secondary box that is the one that's decoupled. So no vibrations are mechanically transmitted to the glass or the room. The very deep full range bass trap in the back (and side walls and ceiling) of the Mastering suite makes sure that basically no energy is bouncing back to glass wall at any point in time, it's a one way trip from speakers to any other surface (except floor).

You got it 100% right re: the lounge. It's a bass trap for whatever LF energy is still radiating from the back of the decoupling nacelles/speakers. But if you were to stand behind the nacelles in the lounge while J is playing music at high SPL, you'd realize that in fact not so much energy radiates anyway. While in the Mastering suite you'd have to scream to have a conversation, in the lounge, you could just speak with a normal voice. This is due to the nacelles being very heavy, using 2 thick layers of dense material. So it kills a lot of the residual LF from the get go. Which in turn makes my life a lot easier as it means I don't have to use heavy artillery in the lounge - unlike the bass traps in the Mastering suite itself which are very substantial. Backwall trap is often over 1.2m deep.

Down the line all I need to do in the lounge is control the modal range a bit, widen the Q of any resonance to tame it. From this point it is so attenuated on the way back to the glass wall, that it simply can't make it back through the heavy glass or 56 or 59dB R(W) door (can't remember which was used there). Even without the treatment it would not make it back. But we don't take chances.
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