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Thread: Ideas & suggestions for designing a dedicated Sound Room

  1. #16
    Senior Member 1audiohack's Avatar
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    Quote Originally Posted by RMC View Post
    RE "people swore by the golden ratio, which I don't really remember,"...

    The Golden Ratio: (0.618X1X1.618) yields a 2/3 octave spread between the first standing wave of each dimension.


    A common acoustic ratio of: (0.7937X1X1.2559) spreads the first standing wave of each dimension by about 1/3 octave.

    There is a bit of easy math that predicts the low frequency performance of a room but most goes out the window when the space becomes more complex than a box.

    I am interested in this project.

    Barry.
    If we knew what the hell we were doing, we wouldn't call it research would we.

  2. #17
    Senior Member RMC's Avatar
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    RE "... but most goes out the window when the space becomes more complex than a box." This is probably what made Eargle say the following:

    " Extending the analysis of boundary conditions to an arbitrary space is complicated, but if we can limit the discussion to a rectangular space the analysis will be much simpler."

    The math referred to by Eargle is on the pic shown (Loudspeaker Handbook, 2nd ed., P. 368 and 369; chapter on the listening environment; interesting stuff but sometimes gets complicated...).

    Richard

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  3. #18
    Senior Member Champster's Avatar
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    I’m reporting back after I talked with 2 acousticians. They each reviewed my drawing and gave me some helpful ideas over about a 15-20 minute phone call. I am fortunate to have received a very high level referral to each of them as their fees were far more than I’d be willing to pay for a full blown analysis and treatment of the room, so these short calls are as far as I’ll take that with them.

    They both suggested things that were previously mentioned by previous posters on this thread. Things like the golden rule, the angles making a computer model more difficult to use and have a high degree of confidence in without confirming the model with real room measurements after construction.


    Although they had the correct drawing to review, the one I posted in my first post should show the width at 14’8” rather than 13’6”. We accomplished that by lowering the height of the side wall from 5’4” to about 4’. They confirmed that other than the length of the room, its ratio is a good starting point. One suggested adding a moveable (making the room tuneable) convex, semicircle wall near the door, in that squarish room, to limit the listening space to about 23'. Also, they both liked eliminating as many vertical 90º corners as possible with products designed to diffuse and absorb, they called them bass traps. They offered other suggestions like: isolating the drywall from the studs; adding extra padding under the carpeting; general rule of diffusion behind the speakers (M2) and absorption behind the listener; more 20A electrical plugs than I think I’ll ever need.


    But really, other than the moveable wall idea, they really didn’t offer anything that others hadn’t mentioned in previous posts.


    They were very instructional conversations and I’m sure if I had $10g’s to drop it’d be amazing but maybe I can get most of the way there on my own…


    Thanks for everyones interest in this project!!!!
    JBL M2 & 2x SUB18s, BSS BLU800, VTV Purifi Amps, MiniDSP SHD Studio, PS Audio Perfect wave DAC

  4. #19
    Senior Member RMC's Avatar
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    More room proportions and ratios...



    Yesterday came across this short oldie, but quite interesting note about room proportions and ratios, authored by Paul Klipsch but discussing shortly an older paper on this subject from R.H. Bolt, Acoustician. Though from the late sixties, still relevant being fortunate the laws of Physics don't change every year. Not a difficult read.

    Klipsch has done Engineering school, graduated twice (two different levels) in Electrical Engineering, in addition to his speaker-in-room experiments. Referring to Bolt's article, published in the Journal of the Acoustical Society of America, he comments, and adds his own input plus some assessments of other room ratios. Paul Klipsch's name appears at the end of the second page posted.

    The R.H. Bolt mentioned is the one from Bolt, Beranek and Newman the famous acousticians firm (Beranek's book Acoustics being a classic reference on the subject; along with Harry Olson's Acoustical Engineering from the same period).

    Barry mentioned (Post # 16) "I am interested in this project." Well, here's some other room ratios to chew on...

    Richard

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  5. #20
    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by RMC View Post
    Yesterday came across this short oldie, but quite interesting note about room proportions and ratios, authored by Paul Klipsch but discussing shortly an older paper on this subject from R.H. Bolt, Acoustician. Though from the late sixties, still relevant being fortunate the laws of Physics don't change every year. Not a difficult read.
    Thanks for sharing…. I must agree 100% with Paul Klipsch.


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  6. #21
    Senior Member Champster's Avatar
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    As 6 months has now passed since the most recent post, we are looking a lot like a home. The roofers finished yesterday and all (framing, mechanical, plumbing & electrical rough in) permits have all been approved. Next week we move forward to spraying the foam insulation (sealed attic and crawl space) and then on to drywall.


    As for the sound room, it has changed somewhat from the original architects drawing. I've increased the size of the area by the door (reducing the size of the closet) and moved a few walls around to eliminate the small jogs in them. I also framed in a few 45º corner openings for bass traps and will use ⅝" drywall on all surfaces. We also added a dedicated 20A circuit with 4 different outlet locations to allow for multiple setup positions.

    As you can see from the attached drawing (not to scale), the longest length in the room is about 33' and the shorter (long) length is about 26'. The width is 16' at the base and up to 48", then the side walls angle inward at 45º. This angling ends at the other thin line on the drawing. The ceiling is (flat) 9'. Although not ideal dimensions, at the suggestion of one of the acousticians I talked to, I have the option of building a concave wall to shorten the room, if needed.

    I'm looking forward to getting in and seeing what challenges all these angles create.
    Paul

    Audio Room - Sheet1.pdf
    JBL M2 & 2x SUB18s, BSS BLU800, VTV Purifi Amps, MiniDSP SHD Studio, PS Audio Perfect wave DAC

  7. #22
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    Many of the specifics I'd mention have already been suggested, but can vouch /validate that a combination has worked for me.
    Non-parallel and 'floating' walls with 'hanging' ceiling have been excellent, as has use of Double-drywall, acoustic caulk, rubber washers.
    For me, 'Rockwool' proved to be single most essential material and brought immediate, audible improvement to every location.
    When finishing, it can be easily shaped/wrapped in fabric to create bass-traps, wall panels, whatnot and to my ear, seems more effective than foam units.
    Best of luck!

  8. #23
    Senior Member HCSGuy's Avatar
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    I would consider having your electrician run a second 20A circuit to your equipment rack for your subwoofer amplifier. I don’t know all of your equipment, and do know your VTV amps are very efficient, so you may be able to get away with a single circuit, but it would give you future flexibility. My system uses almost half of your single circuit at idle - almost 1100 watts. Admittedly, I am using some inefficient amps (Bryston), which draw almost 200 watts each sitting still, and are only about 50% efficient in use, so 5x100w coming out of my speakers would require 1000w going into the amplifier. My projector also sucks about 400w. Three crown amps and 3 powered subwoofers all use very little power at idle, but the rest of my rack (DVR, Emotiva processor, networking, sources, etc) is about 250w turned on and idling). With a single dedicated circuit, this would only leave 1300w for actual speaker power (less with my Bryston amps), which goes away quick on subwoofers. When I’ve experimented with sealed and EQ’d subs, I’ve clipped 600w amplifiers at only moderate levels. My room currently has (1)20A/120v circuit for the Bryston Amps, (1)20A/120V circuit for the surround amps, projector, and sources, (1)20A/240V circuit for a future subwoofer amplifier (which may end up being reconfigured into 120V for a VTV amp), and a 20A room circuit, which currently runs (3) Array 1500 subs and the LED lights in the room. I realize this is overkill and am not lobbying that you go this far, but do recommend having 2 dedicated circuits and letting your sub amp, which does most of the work, have its own. Hope this helps
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  9. #24
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    In the past I had heard/read (IIRC), that for a room with an 8 foot ceiling, the ideal ratio is 20' x 14' x 8'. Other sizes can be scaled from this ratio.

    BTW, I recently updated my entertainment center with 8-gauge romex and a dedicated 20 amp breaker. And FWIW, I put a big ferrite bead over the romex where it exits the breaker panel. The romex runs directly from the breaker to a 30-amp recepticle located within the entertainment center, then to two 20 amp, hospital recepticles, still in 8-gauge all the way. This seems to have taken "hash" out of the system.


  10. #25
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    when some houses were built in AZ, the higher end ones got floor sound deadener installed on the second level's floor. Even while still being finished, those homes were so much quieter. Joists were still on 16" centers. The sound just didn't make it to the joists very much.

  11. #26
    Senior Member RMC's Avatar
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    I agree with HCSGuy. A 20 amp circuit may seem like a lot but its not that much when you give it some thought. More so when the 20A has 4 different outlet locations. With 4 outlet locations it could be tempting to plug other stuff, robbing you of some current initially for audio?

    Naturally all this juice talk depends on the breaker panel size and number of circuits available. I think another 20A you won't regret, probably will be glad if you do, as long as you can afford it electrical panel wise.

    There's other options too like using 14/3 or 12/3 cables (instead of 14/2 or 12/2). In the former you have two 15A circuits in one cable (wires: one black and one red, both hot; one white neutral, and a ground. Neutral and ground are shared). Same thing for the latter except its two 20A in one cable. These cables are usually somewhat more expensive than standard ones since they have an extra wire. But you get two circuits.

    When you're short on breakers sometimes you can double tap one when the loads allow. e.g. You check what's on breaker A and breaker B and if its two small loads you can put them both on the same breaker often having two spaces for hot wire, therefore freeing a breaker for something else. You only move one hot wire, when wiring length allows, the neutral and ground usually stay where they are. Simple.

    The use of power bars is generally a good idea to protect audio gear from power surges or lightning strikes. The bar should take the hit instead of audio equipment connected. Some older equipment may be difficult to replace, better off scrapping a power bar than a valuable amp. My advice is stay away from cheap or bars with long (e.g. 25 ft.) cable this is crazy, it adds way too much resistance. Most power bars are 15A, but i have two with only 2 ft. of 14 ga cable which adds next to no resistance. The shorter the better.

    RE "(1)20A/240V circuit for a future..." A 240V circuit is certainly appealing since twice the voltage means half the current draw, so smaller electricity bills. Problem is not much gear around here is made for 240V, except for a few having dual or multiple voltage built in capability.

    Btw i considered purchasing from Clair Brothers Audio a new old stock 220V Crest Audio amp. The voltage didn't scared me off. But when i calculated cost with the currency exchange rate, shipping of this somewhat heavy amp and the likelihood of having to pay Canadian taxes on it (since its new not used), well it was getting near to twice the cost, so i kissed it goodbye...

    Btw(2) If i ever get enough time to work on my room as much as i would like (boss to do list always more important than mine, you already know that), then i should have 90A dedicated to the room (2x15A + 3X20A), but sometimes i wonder if i'll add a little more...

    Finally, lawyer insists for the following mention: Always consult a licenced electrician.

    Richard

  12. #27
    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by toddalin View Post
    BTW, I recently updated my entertainment center with 8-gauge romex ... This seems to have taken "hash" out of the system.
    That explains the hash I heard that on your videos!

    Sorry man, just pulling your chain.

    I agree with you that a dedicated circuit for your AV is a good call. A couple of years ago I did something similar. My old house's wiring was so bad that the voltage drop to my amps was enough that during peak use times my amps would shut off. I added a sub panel near my system and had my electrician run 10ga wire to my dedicated 20 amp outlets. I used twisted pair conductors in steel EMT conduit. (effectively shielded power)


    Widget

  13. #28
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    Quote Originally Posted by Mr. Widget View Post
    That explains the hash I heard that on your videos!

    Sorry man, just pulling your chain.

    I agree with you that a dedicated circuit for your AV is a good call. A couple of years ago I did something similar. My old house's wiring was so bad that the voltage drop to my amps was enough that during peak use times my amps would shut off. I added a sub panel near my system and had my electrician run 10ga wire to my dedicated 20 amp outlets. I used twisted pair conductors in steel EMT conduit. (effectively shielded power)


    Widget
    You need to consider that the prior circuit, and its breaker, was the oldest circuit in the house (and one of just a couple circuits to still use a 15 amp breaker) and is shared with the HVAC system's fan (but obviously not the compressor) and other areas of the house. With nothing else turned on, I could put the Behringer RTA up to its maximum sensitivity, turn on the HVAC, and watch the noise floor rise on the display when the fan comes on.

    Now consider that this old circuit was also supporting the Yamaha (1,200 max input), a Sunfire Signiture sub, a Crown PSA-2XH sub, and an Epson projector, plus all of the other stuff that draw's little, and there is bound to be some voltage sag especially when engaging 7.2 mode.

    If in fact you could hear the "hash" in a YouTube video..., what does that say about the resolution and ability of YouTube, as well as the Nikon D750 SLR, to convey detail? That is of course, unless YouTube/Nikon was responsible for the hash.

  14. #29
    Administrator Mr. Widget's Avatar
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    Todd, I was kidding about the hash!
    I was just continuing my ribbing you about the utility of that form of "scientific" demonstration.

    On the more serious topic of AC power; from your description above, it sounds like you absolutely needed to upgrade your power as I did.

    In my case, often between 5:00PM and 9:00PM with the neighbors all coming home and powering up their everything, I could watch the voltage drop at my amps to 115 VAC and then it would dip below that and my amps would literally start distorting and stop putting out a signal... I doubt it was too good for them. I would run over to them power them off and wait for the voltage to go back up after the neighbors' daiquiri blenders and god knows what were powered off.


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    Misc Electrical Comments...

    You can put many audio loads on one breaker, but when you turn up the volume expect breaker trips. I had 17 power amps (4 of them bridged), active crossovers, time delays, equalizers, audio sources and more on one 20 amp circuit lol. It was ok at lower listening levels, but it wasn't hard to trip (it was a temporary setup just to test various equipment setups). Then there is the problem of the noise being generated on the power lines and transmitted to other equipment (like power amps) if digital sources are not isolated from other equipment. You are better off having several separate circuits (that is, several circuits from different breakers) as a minimum

    Putting more than one wire to a breaker may be permitted in Canada, in the US it is very questionable. Depends if allowed by the local authority having jurisdiction. Even if allowed, the breaker must be designed and rated for more than one wire. Be careful...

    Same goes with using 14/3 and 12/3 wire for two circuits. If it is allowed in your area, it must be done properly not only from a safety standpoint (properly grounding the two circuits can be tricky), but also from a noise isolation perspective (especially in audio!). Many areas only permit 20 amp circuits (12 gauge wire) minimum...

    Twisted wire in EMT conduit is an excellent way to shield wiring. Rigid galvanized conduit shields better. An easier way with equivalent shielding results is armored steel (better) or aluminum cable. They are metal shielded, already twisted, and fairly easy to install! Aluminum can be had at any Home Depot or Lowes, steel is rare.

    If you need more circuits in your panel, tandem breakers will put two breakers in one panel circuit breaker space. However, your panel must be rated for tandem breakers.

    If you need many additional breakers, utilize one unused 220V breaker slot and run that to a subpanel providing many more 120 volt circuits.

    If you understand electrical principles, wiring methods, and know your way around the NEC (NFPA 70) electric code (USA), you can do much of this work yourself. Otherwise be safe and get a licensed electrician. Another word of caution, extensive DIY electrical work on your house even though safe and in compliance, could make it tricky to sell your house in your area...

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