Ideas & suggestions for designing a dedicated Sound Room

[Champster]

Hey Guys,
I'm building a home and have the luxury of having an upstairs room that will be dedicated to my audio hobby. I was wondering if anyone had been down this road before and had some suggestions of things for me to include in the room while we're still in the planning stage. I'm thinking of course of things like adding 20A circuits instead of 15A. What else would you suggest? The room will be 13' 6" x 26' 6" with a large closet. I'm going to have the floor supports spaced on 10" centers rather than 16" as normal to cut down on floor vibrations. I was thinking of doubling up the padding under the carpet. Is that a good idea? What else????
Thanks
Paul

88747

[Robh3606]

Couldn't hurt to contact a professional installer for some advice.

Rob:)

[speakerdave]

Your builder will tell you twelve inch spacing would be better because it is a module for standard sheet materials (plywood) sizes. Ten would waste time and materials.

[rusty jefferson]

Congratulations on that! If it's in the budget, I'd do 2 layer drywall with rock wool in the bays.

As Rob mentioned, if you can afford to treat it.....

I have a friend who just did a similar new build. He used this company (https://www.sonitususa.com/product/home-cinema-acoustic-systems) after much research. He's posted some pictures on another forum of the project as well as impulse response and ETC measurements of the empty room, then just absorbers, then adding diffusors, and then adding bass traps. Really impressive performance. I'm going to hear it in a couple weeks. Not sure you'll be able to see it without joining the forum, but here's the link. (http://www.dcaudiodiy.com/phpBB3/viewtopic.php?f=3&t=1983)
Happy to put you in touch with the guy if you pm me. I'm sure he'd be happy to send you the measurements and talk about what he did.

[jmpsmash]

insulation / Safe 'n Sound in the wall, floors. Whoever will be downstairs and next door will appreciate it.

[mmc8180]

Like others have stated, if you are modifying the floor structural stiffness and since this is a second floor room, by all means add insulation in the floor - and possibly walls too. Fiberglass, rockwool, or cellulose whatever your flavor will work, reasonably dense packed. If you can afford, other ideas include:



Consider installing a free floating wall and floor system. This de-couples the room acoustically from the house structure to greatly minimize sound from exiting or entering the room. This consists of a subfloor attached to the floor joists, a layer of an elastomer (e.g., "Green Glue"), a top floor not nailed or glued but riding on the elastomer. The walls will have a similar design. I would use a cement board as the top layer (Durock) for the increased density to deaden the top floor layer.
Dense carpeting and under layments sound padding could be cheaper than the above and may work reasonably well too, but wouldn't be as isolating as the above ... I don't think. There are also products for under layments to wood floors too
By all means upgrade your electric service to 20 amp. I would also add enough circuits to cover your known A/V load and several additional for future needs.
Also consider cable, wired internet, wireless internet and methods for hiding speaker and low level audio wire


Like you I had the blessing of starting with an almost clean sheet, so I did the insulation, free floating walls/floor, and electrical service upgrade. I have yet to install any audio equipment to test it out but playing radios very loud and walking women's heels do not transfer out of the room, nor does my wife's piano playing downstairs enter the room. Subwoofers will be the real test I'm sure. I ended up with 6 120v 20 amp circuits and 1 220V 30 amp circuit dedicated to A/V systems.

Not done yet so I'm hoping to get some additional ideas from this thread!

[jbl4ever]

Hi Champster, here is what I used to help determine my construction for my room. A good thing to follow as I got my STC rating to over 60 db.
https://en.wikipedia.org/wiki/Sound_transmission_class

[HCSGuy]

I do not know what phase you are in, or what your budget is, so take this advice, or don't. As drawn, you have a very difficult room. I would suggest hiring an acoustic engineer, but I think they would find it tremendously difficult to model a small room (compared to an auditorium or the wavelengths you're dealing with) with so many changes in the ceiling and walls. There are two issues I see. First, your room length is almost exactly double the room width. This means that any frequencies that have room modes side to side will also have them front to back, and many of the frequencies that don't, won't have them lengthwise either. This means that, in the bass, you will have very strong variations from one seat to another in frequency response. The first dedicated theater room I built was built into an existing space, and while larger, had a similar almost multiple of the width and length. It was a two row theater, with the largest screen we could light up with a 7" three gun Vidikron CRT projector, which wasn't large by today's standards (110", maybe?). When we were done, the back row had this awesome bump at 27hz or so, and the front row had a suckout at about the same frequency. So, explosions rocked the back row, but did nothing in the front row. Conversely, the picture looked about right in the front row, but a little small from the back row, so the owner was never really happy, as he didn't get the best of both in any place. We ended up putting bass shakers in the front row riser, which faked it a little, but it was never satisfying. As an exaggeration of this I remember taking an acoustics workshop with Dr. Floyd Toole at a CEDIA convention, and he purposely went there ahead of time and found a room that had even multiples in all three dimensions - like 24x24x12, with cement walls and floor to keep the energy in. After talking about the importance of evenly distributing room modes, he fired up a signal generator, and played one frequency, mid 40hz range, and had us walk around the room. You could move 4-5 feet and experience maybe a 20db swing at that frequency - you'd go from being able to feel it, to barely being able to hear it. So, if it's not too late, get an acoustic engineer to at least give you their opinion. I remember in the old days, people swore by the golden ratio, which I don't really remember, but the idea was to distribute room modes as evenly as possible to get the flattest bass response throughout the room. Btw, It will help somewhat (and unpredictably) that the entry wall is broken up by the closet and the entry space, but I don't think anyone can tell you how much.

Second, your double vaulted ceiling may cause a problem, especially if you set the room up lengthwise. If you sit down the center of the vaulted part, at the right range of heights, you'll get some weird echos off the ceiling. You may hear the HF part of a snare drum hit three times, very close together, which sounds odd. If a percussionist is using a brush on the snare, you may not be able to tell how he's moving the brush, as it all blurs together. As another exaggeration, we used to work with a contractor who built really high end spec homes in the SF Bay area. On one house, he had us wire for a dedicated theater room, but changed his mind before the house was done, and changed it to a multi-purpose media room. Part of this change was hardwood floors instead of carpet, and the other was that he didn't like the plain, flat ceiling, so he put in a barrel vaulted ceiling. It looked great, the house sold, and the new buyers put a pool table in the back of the room, and wanted a surround system in the front of it. We did, and it was probably the worst sounding room we ever did. If you sat down the middle of the room, and were at the right height, which in this room was a higher than seated height (maybe low barstool height?), near the foci of the barrel vault, you would hear any transient high frequencies as a series of very closely spaced reverberations - kind of like being in a mini echo chamber. The owners didn't really care, as it wasn't really bad when sitting down, but if you were moving around the room while something was playing, every now and then it felt like an acoustic laser had locked onto you - very weird sound. Obviously, thick carpeting would really have helped for this, as what we were hearing was a vertical, high frequency "Slap echo" between the floor and the ceiling that was then being focused back to a narrow range of points.

Sorry for the post, as I realize it doesn't really contain any helpful information. Btw, if you had high six figures money for this room, and hired an acoustic designer, most of them would have you build the room as a plain rectangle - flat walls, flat ceiling, with proper dimensions to evenly distribute room modes. If you wanted a curved screen wall, or stepped side walls, they would do them, but they would be built as acoustically transparent faux-walls in front of the flat ones, in fabric panels. This way they can give you predictable performance in a room with irregular surfaces. Like most people here, I have never had the luxury of building a home, and have always had to work with what I had, but given the opportunity, I'd start with the right room dimensions, since it doesn't change construction costs. Lastly, if you get bored, look at Keith Yates' website for the most over the top engineered solutions out there...

[jmpsmash]

Agree, I am sure a lot of us would love to be in the position to design and build a room. Instead, we are just trying to deal with what we have. Personally, I am still fighting my 20x20x9 room which has huge suckout between 40-50Hz.

[Mr. Widget]

I didn’t want to bring it up, but since HCSGuy jumped in, my first thought was oh dear, those dimensions look difficult.

If it was my room and I couldn’t negotiate a different space in the house, I would build another closet or storage area in part of the space to shrink the long dimension of the room. Finding a pro who can help and not rip you off might be tough, but it could be a really good investment.

Other than that, I agree with most of the suggestions for room isolation, added power etc.



Widget

[RMC]

RE "people swore by the golden ratio, which I don't really remember,"

The Golden ratio of dimensions used for its acoustical properties is 0.618 D, 1.0 W and 1.618 H. The reference dimension being 1.0 Width, then depth will be 0.618 of width, and height will be 1.618 of width. Basically a "shoe box" type room when placed horizontally instead of vertically.

When applied to the room this ratio will usually mean: 0.618 is height, 1.0 is width and 1.618 is length. That should help to minimize acoustical issues, but won't eliminate all of them. Other ratios do exist.

As i recall this ratio is the same for a room as for a speaker box, both being enclosures.

If one's bank account allows, hiring an acoustician for big bucks is the best solution.

[jmpsmash]

OP's room is reasonably close to golden ratio if he cuts the length to 22 feet long.

[Mr. Widget]

OP's room is reasonably close to golden ratio if he cuts the length to 22 feet long.:yes:


Widget

[grumpy]

video wall, equipment cabinets, bass traps, ... "extra" space could work out well :)

[Champster]

Wow you guys are great!!!! I go away for a few days and came back to many very insightful comments and all are very much appreciated!

I’ve received a few names of acoustics consultants and will reach out to them to see what they can offer without charging an arm and a leg.

I’ll report back with my findings...

Thanks again!

Paul

[1audiohack]

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.

[RMC]

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

88792

[Champster]

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!!!!

[RMC]

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

8908989090

[Mr. Widget]

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.


Widget

[Champster]

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

90071

[Wespence]

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!

[HCSGuy]

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 :)

[toddalin]

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.

https://cimg0.ibsrv.net/gimg/www.corvetteforum.com-vbulletin/2000x1333/80-dsc_0009_515f2b5a91414dfcf37353ab6446b6c3bc4fb0f9. jpghttps://cimg8.ibsrv.net/gimg/www.corvetteforum.com-vbulletin/2000x1333/80-dsc_0005_6ab72795dea4ab8c01d615df31ea66a738902486. jpg

[engineerjoe]

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.

[RMC]

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

[Mr. Widget]

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. :duck:

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

[toddalin]

That explains the hash I heard that on your videos!

Sorry man, just pulling your chain. :duck:

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.

[Mr. Widget]

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.


Widget

[mmc8180]

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...

[RMC]

RE "Then there is the problem of the noise being generated on the power lines"

When equipment is properly wired and grounded, there is no power lines noise for me.

RE "Even if allowed, the breaker must be designed and rated for more than one wire."

My 120V breakers from a Square D breaker panel, MADE IN THE USA, have two slots to specifically allow connection of two hot wires on a single breaker, known as double tap. Maybe cheap panel breakers don't allow but mine do.

RE "Same goes with using 14/3 and 12/3 wire for two circuits."

That mention implies the two hot wires from a double circuit cable (14/3 and 12/3) are connected to the same breaker, it is NOT the case. When a two-circuit cable is used the black and red hot wires each go to a separate breaker. Stating "Same goes..." seems incorrect. Double tapping (two hots on same breaker) and double circuit cable (each hot going to a separate breaker) are different animals.

RE (properly grounding the two circuits can be tricky)

Its not rocket science nor tricky, simply need to know how to do things when neutral and ground wires are shared with the two circuits. There's an additional safety trick most electricians and DIY don't do when installing a double circuit, i learned it from a Master Electrician, you need to put a flat head nail joining those two breakers (there's a hole for this) so that if one trips the other follows. Very logical, good reasons for this, too long to explain here. Other breakers don't have a joining nail, only those for a double circuit.

RE "or aluminum cable."

The suggested use of Alu cables is very surprising. Alu cabling for electrical work has been banned for years in many jurisdictions due to connection problems with this "soft" metal, softer than copper which is the preferred one. Moreover, Alu has a resistivity about 1.6 times that of copper. Not a great conductor.

RE "sub panel providing many more 120 volt circuits"

The many more may or may not happen since this depends on how loaded the main panel is, and the sub panel can only use the "loose" (amperes) from the main panel. An unused 220V breaker slot would provide two 110V lines.

As always consult a licenced electrician.

[mmc8180]

[QUOTE=RMC;439635]RE

When equipment is properly wired and grounded, there is no power lines noise for me.

Noise can be generated and impressed on power lines from outside or inside your house. Digital sources (CD players etc.), cable TV, lighting, motors within your home (through wiring or through the air) can generate noise in your system. Proper grounding will not eliminate these; it only reduces common mode sources of noise. You should educate yourself on common mode and normal mode noise...

RE "Same goes with using 14/3 and 12/3 wire for two circuits."

That mention implies the two hot wires from a double circuit cable (14/3 and 12/3) are connected to the same breaker, it is NOT the case.

No, two hot leads from two different breakers feeding two circuits sharing the same neutral and ground in a 12/3 cable. In addition to the potential noise from these circuits impressing on the other as stated above (especially in audio power circuits), taking the hot leads from the opposite legs (L1 and L2) can cause several unsafe situations. What could happen if one of the two shared circuits is taken offline and the ground or neutral is mistakenly disconnected? Or the circuit is misidentified on the opposite end and thought to be de-energized before work is started? Many jurisdictions in the USA forbid multiwire circuits in residential structures for that reason.

RE (properly grounding the two circuits can be tricky)

Its not rocket science nor tricky, simply need to know how to do things when neutral and ground wires are shared with the two circuits. There's an additional safety trick most electricians and DIY don't do when installing a double circuit, i learned it from a Master Electrician, you need to put a flat head nail joining those two breakers (there's a hole for this) so that if one trips the other follows. Very logical, good reasons for this, too long to explain here. Other breakers don't have a joining nail, only those for a double circuit.

Proper grounding IS rocket science to someone that does not understand it - I cannot tell if you do. Putting a nail through two breakers is illegal, period. For a multiwire setup (the proper term you are describing) the two breakers must be mechanically connected and designed this way (like a 220v breaker).

RE "or aluminum cable."

The suggested use of Alu cables is very surprising. Alu cabling for electrical work has been banned for years in many jurisdictions due to connection problems with this "soft" metal, softer than copper which is the preferred one. Moreover, Alu has a resistivity about 1.6 times that of copper. Not a great conductor.

Not aluminum cable - aluminum and steel ARMORED cable. Ever hear of those, do you know the difference?

RE "sub panel providing many more 120 volt circuits"

The many more may or may not happen since this depends on how loaded the main panel is, and the sub panel can only use the "loose" (amperes) from the main panel. An unused 220V breaker slot would provide two 110V lines.

Everything you stated in this paragraph is pretty much factually incorrect. You can have a subpanel breaker rating up to 80% of the main panel main breaker rating, and the subpanels branch circuit breaker rating maximums are 80% of the sub's main rating. There is no limitation as you state ("loose amps"? lol) in NFPA 70 that the summation of the values of the branch circuit breaker ratings need to be below the value of the main breaker rating (go to your panel and do the math).

A 220V breaker does not provide two 110V lines, it provides L1 and L2 to the subpanel from which you can derive both 220V and 110V circuits as in your main panel.

So expert in grounding, can the ground and neutral in a subpanel be tied together? If you are wrong and wire it up the incorrect way you could kill someone. Only you need to see your answer before you google it.

I just needed to correct the misstatements you made, so someone doesn't utilize the incorrect information given. I am not going to argue with you - get an electrical engineering degree or a master electrician certification then we can talk.

[Mr. Widget]

RE "or aluminum cable."

Not aluminum cable - aluminum and steel ARMORED cable. Ever hear of those, do you know the difference? FWIW: Using steel MC cable offers a significantly higher degree of EMI shielding than the aluminum MC cable. Some years ago we measured it at work and the difference wasn't trivial.


Widget