Control room angles with PMC TB2's?

hi there, I have a question about control room angles using pmc tb2 monitors, supposedly equilateral triangles are the way to go. All of the designs I can find for inspiration here are based on this idea, with corresponding wall angels. The PMC's however are said to be best if you use them 1.5 metres apart, shooting straight down the room toed in a fraction, while the listening position is 2 metres away and slightly under the tweeters. complicating things is that we also have a pair of Adam a7 near fields as B speakers to include, which would benefit from standard equilateral design. I want to In wall mount the PMC's. if i go with the equilateral, I am sure it will be fine. But to ensure I am 2 metres away from them, in a room shaped like below (attached) with the hope of 2nd room to record in, Its going to be tricky to stay 1 third into the room! perhaps I need a single room design for recording and mixing? Also if I In wall mount these, it means the nearfield adams will have to be stand mounted closer to the listening position, will these create reflections for the PMC's? cheers all for any thoughts.

potentially anything in between the wall mounted monitors and you could result in reflections so you might consider the ADAMs need to be positioned in a bit and closer or raised the PMC up and perhaps angled if needed to make the clearance as good as possible. it's mainly the HF and mids that you have to clear as the LF stuff (while impacted) is big enough to mainly ignore the other monitors.

"The PMC's however are said to be best if you use them 1.5 metres apart, shooting straight down the room toed in a fraction, while the listening position is 2 metres away and slightly under the tweeters. " I didn't locate anything like that...from reputable persons. These monitors are not so far removed from a Tannoy monitor from 12 years ago...nothing new under the sun as they say. Establish, in YOUR room, an equilateral triangle between the speakers and your head. Adjust as needed to get perfection ;) The room will dictate if you even have enough room to reach back for 2 meters. Every thing matters and your room size and treatments will have more influence over this monitor placement than someone saying that this thing has to be done and that is the only way you can do it. Everything matters ;)

how is this looking for a start? comon rip this design apart :)

screen shot pmc's on the outside, adams inside

i'll keep adding screen shots as I progress, I've removed the air gap between the drum room as high isolation between the two is not as essential here, and it will be cheaper, less doors, less walls. I've also added where the doors are likely going to be. (am I effecting my CR angles too much by putting a door close to the monitors?) The PMC's will be in the wall, and the wall will tilt down at an appropriate angel to the listening position (not yet done in sketchup) what is the standard height to expect ones ears to be? The Adam's will be in the same line as the PMC's, just closer and lower. (anything to be aware of here?) In terms of treatment in the room, I am open to suggestions as I am not sure how the angles of the back walls I currently have will effect things. also any comments on the drum room space? cheers all! I would really appreciate any comments! evan.

the second design is looking better. typically you would put the near fields on stands more in front of the desk and angled flatter (15degrees or so) to avoid blocking the soffit mount speakers.

further work on the in wall mounts... any advice?

The tilt angle is way to high. You can tilt the monitors a little if you have to, but 10 degrees is about the limit, and even that is pushing it. 5° is OK. Yours is about 22° !!! The reasons being: your ears are not designed to do the best job with sounds coming from more than about 3 or 4° up. Your ears do better with sound coming from straight ahead. plus you are creating first order reflections all over the desk, console, and your A7s, and also pointing your speakers at the floor, which will be reflective anyway, not to mention comb filtering effects, and other nasty stuff. Then there is the issue of the soffits themselves: If you are going to tilt it, you should really tilt the entire thing, floor to ceiling. The soffit acts as an infinite baffle, an extension of the speaker cabinet itself, so you want it as large as you can possibly get. Ideally, it should be at least a 1/4 wavelength of the lowest frequency that comes out of the speaker in all directions (up, down, both sides). That's really hard to do in a small room, of course, but you still want to go as far as you can in that direction. Putting just a few extra inches above and below the monitor isn't going to help all that much. Think BIG! Finally, there's also the issue of that "stepped wedge" shape poking out from the front wall: Hard to say exactly what that will do to the room acoustics, but whatever it does will most likely not be very pleasant! - Stuart -

thanks!! back to the sketchup board :)

out of interest, on the angle of tilt, if the screen you are looking at is also raised, and your head is tilted, (even if this is only 5 degrees, with the speakers at 5 degrees) would that not make your ears flat with the speakers? ie, if i wanted to go for 10 degree tilt on the wall mounts, if i make the screen at the same height as the tweaters creating the same angle, that would improve things? just out of interest. I hear all your other comments about first order reflections. the 1/4 wavelength of 40 hz is 2.125 yes? seeing as that is impossible for me to achieve with my room, what would be a more realistic goal? cheers, and thanks SO much for criticism.

this is a useful paper for this type of estimating. http://www.quarter-wave.com/General/BSC_Sizing.pdf then you get into technical stuff http://diyaudioprojects.com/Technical/P ... ackman.pdf but if you want details... http://www.kensonpro.com/linnaraudio/te ... ction.html or a more simple approach: http://trueaudio.com/st_diff1.htm or just plan on your baffle plate being a minimum of 3x the diameter of your LF driver. also consider that the overall soffit assembly often includes the angled side walls, baffle, middle section and the baffle could extend up to the ceiling and almost to the floor so the total area of the baffle isn't just the baffle plate immediately adjacent to the speaker. more correctly, the lowest frequency where the baffle step starts to rise is about 1/8 wavelength not 1/4. max increase is about the wavelength of the panel - so your planned compensation settings should span that range. eg. if you have a panel 40" wide, then you're probably around 43hz on the low side and 340hz on the top. wrapping the front of the room with solid (or slat) side walls and middle section plus top and bottom and solid backed clouds, you begin to see how the LF is extended and the slats and wave guide effects transition well through the calculated middle frequency point and diffusive mid-high absorption reinforcing the RFZ sweet spot with enough HF energy... rambling now...