Attic listening room project - advice welcome

[Expl0vision]

Hi there!

I've been lurking around on these forums for a few months now, trying to capture as much knowledge and advice from experienced folks as possible. Now, I am getting close to a draft plan for turning my attic into a music listening room. I would like to share my current situation and thought process, in the hope that you guys can provide some advice and perhaps challenge me on my suggested approach.

I am willing to invest some time and money to improve the perceived acoustics of my room, but my biggest fear is spending money on something that only returns marginal improvement at best.

So, please feel free to share any experience or thoughts. If more information is needed to provide sound advice, do let me know.

Current Room Situation​

Attic room size: 4.4 x 6.2 meters (14.4 x 20.3 ft)
Sloped ceilings with heighest ceiling point at 2.85m (9.3ft). Lowest point of sloped ceiling at 0.95cm (3.11 ft).

Please find photos below.

Currently, no (deliberate) acoustic treatment is present. But the room has some characteristics that I hope to be advantageous. I will do my best to use the proper terminology, as English is not my mother tongue.

The walls and (sloped) ceiling are drywall (12.5mm / 0.5 inches thick), behind which is an airgap of about 22mm (wooden horizontal 'suspension laths' for the drywall, spaced at about 15cm / 0.5 ft), behind which are the roof's rafters. Between the rafters there is mineral wool/fiber isolation (thickness 22cm / 8.66 inches).

The image below illustrates this (but in my case drywall is fixed against wooden laths, not alumium).

Below table contains the sound absorption coefficient αS of the mineral wool/fiber between the rafters. These specs are for the 10cm variant (I have 22cm so more than twice as thick).

I have read that sound below 125Hz will mostly pass through the drywall rather than reflecting, which will then be (partially) absorbed by the mineral wool/fiber isolation. So, this could be helpful with the deep low-end, hopefully reducing the need for bass traps once I introduce a subwoofer. I also read that these type of drywall structures may resonate at certain frequences which may be a bad thing. All just hearsay, indeed. I will include my first REW measurements below so we can try and stick to the factuals of the actual room.

The flooring is vinyl on top of a thin layer of cork, below which there is a type of 'isolating cement' which is also marketed to have some accoustic absorption properties, but no specs like αS in the technical sheet so to be taken with a grain of salt I guess. In any case, I have a relatively deep-pile rug on the floor at the first reflection point.

Current Audio Equipment​

Yamaha HS8 active monitors (stereo setup)
Behringer UCA202 USB DAC
UMIK-1 measurement microphone

I listen to various music styles ranging from blues to art-pop to hip/trip-hop to electronica (e.g. lounge/deep house, not overly energized). I tend to enjoy tracks with deep (and clear) bass, so thinking about adding a subwoofer at a later stage.

First Measurement​

These measurements are made without any EQ active. The HS8's switches on the back are all set to flat. Single measurement at MLP (no averaging).

Attached is the FR graph with 1/24th octave smoothing. Also below impulse, waterfall and spectogram graphs, for what its worth.

I do not have a lot of experience with interpreting these graphs, so I will try to formulate my first takeaway (or questions really).

- Some peaks/drops at 41, 95, 130, 160 and 244 Hz. Room modes? SBIR? I don't know what to make of it.
- I guess the heavy fluctuations in the FR graph is comb filtering, which would reduce once absorbers at first reflections points are there (see planned approach below)?
- All peaks above -20dBFS in the Impulse graph are reflections, right?
- Decay time (in waterfall and spectograp graphs) seems rather good for an untreated room, I think?

Frequency Response

Group Delay

Waterfall

Spectrogram

Approach / Next Steps​

1) Listening position and speaker placement

The room is small and as a result I will always be sitting relatively close to the back wall. I already moved the couch a bit away from the back wall and I plan to install accoustic panels against the back wall (well, sloped ceiling) to reduce first reflections there. I am hesitant to move the couch further away from the wall, for aesthetical reasons (and further deviation from the equilateral triangle).

The couch / listening position is centered, Unfortunately the right speaker cannot be moved much more towards the left because of the door, so I had to widen the distance between the speakers. Because I don't think it would be wise to move the couch back against the back wall, this implies that there is more distance between the speakers (3.80m / 12.5ft), than there is between speaker and listening position (3.60 / 11.8ft). I therbey sacrifice a perfect equilateral triangle in order to at least have a centered/symmetrical setup. My intuition says a centered setup is more important than a perfect equilateral triangle but I have not found any science to back that up.

I have read that for small rooms, when it is not an option to keep a minimum of 1.2 to 1.5 meter (4 to 5 ft) of distance between speakers and walls, second best option is to place the speakers as close as possible to the back wall, which is what I did. I plan to place acoustic panels behind the speakers to minimize early reflections.

2) Accoustic treatment

Second step would be to install acoustic panels at first reflection points: Back wall, left/right wall, front wall (just behind speakers) and ceiling. On the floor is a deep-pile rug at first reflection point.

I am considering the Akotherm Basic or Flamex Basic melamine foam panels of Merford, thickness of 4cm or 5cm (2 inches). Unfortunately, I cannot link to the technical sheets.

I am considering going through the effort of installing these with an airgap of 5cm (2 inches) for the back wall.

There is a narrow staircase behind the (not so well insulated) door, which causes reveberations. I plan to cover the door with the same material (without airgap) in an attempt to minimize this problem.

3) DSP / Dirac Live

Third step would be to replace my Behringer DAC with a MiniDSP DDRC-24 DSP with Dirac Live. I hear good things about Dirac Live: It adjusts frequence reponse (PEQ style), it applies phase / IR corrections, and most importantly it is relatively easy to use. I know I said I am willing to invest some time in this matter, but I fear that the 'manual' way with REW, parametric EQ and technology like convolution engines and/or rePhase will send me down a rabbit hole of trial and error and virtually unlimited permutations of tweaks and options to strive towards the best result. I sense frustration in that. I am not the chosen one, I'll take the blue pill.

4) Subwoofer

Next, I would like to try and integrate a (sealed) subwoofer into my system. I am considering the SVS SB-2000. I think I might even be crazy enough to go dual-sub if I fail to get the first subwoofer balanced enough in my room at various listening positions (main listening position and the seats left and right from that). This is a more mid-term idea, as I feel that my HS8's are already quite capable on the low-ends (down to 30-35Hz).

I am wondering if investing in a subwoofer will also cause the need to invest in (either thick and expensive or tuneable/complex and expensive) bass traps, otherwise the sub will do more bad than good?

 

[Sonnie]

Welcome to AVNirvana... thanks for joining and participating.

I'm getting an optical illusion between the first and third images of your room. I assume the speakers are the short wall of 14.4 ft., and your couch sits about 18-20 ft from the speakers. That third image makes the couch appear to be a lot closer... lol.

This is no doubt an odd-shaped room, and there is probably no formula that will be chiseled in stone as to what will work best, not that there ever is, really. It always takes some trial and error to determine the best listening position and speaker placement.

Consider this: http://www.cardas.com/room_setup_main.php

It's what gave me a good starting point. I've never been a fan of equilateral triangles and never heard a system that sounded that good with that setup. When I hear one, if I move forward, it usually sounds significantly better to me... more immersed in the sound... better everything. I've not heard many systems that sound that great with speakers up against the wall... the soundstage is skewed because it lacks depth acuity. I also wouldn't want my primary listening position close to the back wall. You could be putting a lot of effort and possibly money into something that is hopeless due to your constraints. You might get something somewhat acceptable, but is that what you want in a dedicated listening room? I have often asked people why they are buying expensive speakers and shoving them up against a wall... it just doesn't make a lot of sense. If you go to the audio shows or check out the show reports, you rarely see a speaker up against a wall... for a reason. I've seen them against some side walls because they were in a small motel room, but not many, if any, against the wall behind the speaker. They are almost always pulled out from the wall. Again... check out what Cardas has studied and shared in the link above.

If this is a "music listening room", why are you worried about aesthetics... put the couch and speakers where you get the absolute best sound. That's the one thing I love about my room... I can pull the speakers out as far as I want and place my main listening chair wherever I wish... it's my room and I can do that. I want it to sound the best it can sound... if you know what I mean.

I suspect you would appreciate some absorption panels placed on the side walls since it appears you'll get some serious reflections there. I don't think there is much you can do below 150Hz due to what is required to tame reflections down that low. If you wanted to go the Dirac Live ART route, that might help if you have some subs that are capable to help out. Dirac is wonderful in and of itself without ART, so I would highly recommend it.

SVS makes very good subwoofers, and that 2000 should be just fine, although a pair would most certainly be better and worth it in my opinion. You might experiment with one in the front and one in the rear... and Dirac Live will smooth those out like nobody's business. It should also take care of the other frequency response issues you have.