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Home theatre build....DIY..slowly..


MercedesBerater
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Ive been a crown fan for years, so I was hesitant to go away from them. but I took a chance with Emotiva XPA-1L. I've had them for almost 2 months now and I love them. However if went back to doing live sound I would go back to Crown. (Bullet tough).

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Not sure that I'd need monoblocks for the 7's? It'd be super cool, don't get me wrong! Having four big monoblocks for the towers.. Hell maybe even a monoblock for the center 64ii ! But that's just a lot of money to spend, and I think after the XPA2 it's diminishing returns.

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monoblocks is a big fat waste of time. i bought 7 to replace a xpa-2 and xpa-5 and there was no improvement what so ever. so after realizing it took up my whole damn rack and all my plug ins i got rid of them and switched back to another xpa-2 and xpa-5 and then soon moved the a sherbourn pa7-350

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I agree. I have no use for monoblocks. I just like the idea of the impressive look it would have in the equipment rack. But I do still enjoy having a few digits remaining in my bank account.

i thought the same way. Big ol stack of monos would look sweet. Lol took up all my space and all my plugs. I hated it the first day. Then when I heard no differences I sold them all
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Soooooo that's almost all of my first row seating is in a 70, 72, 89, 215 Hz null zone? The first three frequencies are pretty powerful bass frequencies in movies, correct? Or is that more down in the 50-60range?

Would quad subs make a better choice? Each a foot from rear/side walls?

Duals? One front / one rear? Both front? Both rear?

Single?

Or will the XMC-1 be able to correct for room imperfections down into that freq.?

See.... The scientific stuff is where I get all kinds of lost.

No. Frequencies will hit you normally from the other two directions. For instance, the 35Hz width will only create a standing wave from left wall to right wall. You will not get a standing wave anywhere else in the room including front to rear and floor to ceiling. Where trouble occurs is where these standing wave frequencies become common in the different directions and orders. The lower the order, the worse the standing wave.

 

I see where you have a 70 and a 72Hz standing wave. The 70 2nd order standing wave is at 4' in from the side walls. There is also a 72Hz 1st order standing wave at roughly ear level. Since these frequencies are very close, you will theoretically notice a big dip in that frequency of you are sitting exactly 4' from either side wall. If you are in the habit of playing sine waves in the 70Hz range, then this will matter. What you have to think of is that 70Hz is only one frequency.

 

In all, your room looks very good. You have only that one overlap of low order and low frequencies. I think you have a very acoustic friendly room. Where people get into big trouble is when the measurements of the room are equal or equally divisible length width and height. For instance, a room that is 16' X 16' X 8' would be horrible. A cube room would be the worst.

 

Try going to this site (http://www.bobgolds.com/Mode/RoomModes.htm) and plugging in 16 x 16 x 8. Also try a cube like 10x10x10. You will see lots of pink and worst  red. Now put in your dimensions 25x16x7.75

 

Hope that makes sense.

 

Also, why does that graph only show a few different Hz? Or are those the ones that are the most affected?

Basically my prime listening position should be somewhere either 10.5 or 13.5 feet from front? If I'm reading that correctly that kind of minimizes the Nulls?

 

Anything above 4th order is pretty much irrelevant, since the db will be diminished by the time it bounces off yet another wall as compared to the fresh sounds being made in the room. Also, higher frequencies are not nearly as relevant.

 

I don't think there will be a bad seat in the house. The only thing you need to be concerned with is sub placement, and that will be determined by the number of the subs and the seating. A sub move of as little as 6" in a room can make a big impact. Adding subs can reduce standing waves to nothing, since the sounds are coming from multiple positions.

 

Lastly, the position and direction of the speakers will have an impact on standing waves. 

 

Like I said, you have a good room there. You needn't worry! 

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Does the balance of the room also mean I will require less in bass trapping? Would you recommend 4 15" subs or just stick with the two 15"s in front.

I'm glad to hear from someone that the room is a good size! I tried to base it off of the golden room dimension formulas within the space I had for maximum width.

Edited by MercedesBerater
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I was looking into johns manville whispertone wall board

 

 

On your other thread, you mention wanting to use acoustic wallboard, which will be better for the sound inside the listening room, but now you describe using double thickness drywall inside and outside the studs, which will be better for reducing sound outside of the room. If your goal is sound containment, your overhead heating and a/c ducting needs to be insulated and isolated so it doesn't carry sound through the whole house.

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Yes. I want to shoot for sound containment & interior acoustic superiority.

I have so far isolated the ductwork that does not open to the room- so that should be good. My only room outlet for ac/heat is off of the main ac/heat trunk running through the whole house.

I haven't determined how to isolate that yet. I've thought about capping that and adding a new branch and using the bendy furnace tubes... Since I haven't figured out what to do with ac/heat access I stopped the ac/heat trunk boxing on both sides of where I may need to access to add a fresh run, and cap off the old.

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If I was building a listening room like yours, I might consider using the drywall-green glue-drywall on the outside of the studs, fill the spaces between studs with Roxul Safe-n-sound, cover some areas of the inside wall with Fire Code rated acoustic fabric (at less cost than commercial whispertone wallboard) and some areas with single layer drywall. Your local building codes supercede my suggestions, but if you can do it, my idea turns your walls into bass traps, allowing you to have more even bass response throughout the room with fewer subwoofers.

 

As for the a/c duct, the flexible duct tubing pre-wrapped in fiberglass is probably the best fit for your application.

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I've considered a false wall at a few locations, I don't know if I could make it seamless enough to look correct or if it would look like a fabric covered portion. Or even where to get fabric wide enough.

I also though about keeping two floor joist cavities open down both sides of the ceiling and filling with Roxul the whole length and doing essentially a "reverse soffit trap" Wouldn't look as bad compared to the wall that people (kids) may touch/poke

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If doing soffit style traps do they HAVE to be fabric covered or just a thin layer of drywall or wood veneer?

If wood veneer would work I could do false columns and just wrap with nice 1/8" veneer and have decorative traps.

If it must be fabric covered- then I'll be forced to do the ceiling style

If drywall doesn't hamper the trapping then shouldn't the whole room be a bass trap since everything will have Roxul?

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Fabric covered Roxul mineral wool (or other noise reduction material like fiberglass or denim insulation) will have an effect on the entire audio spectrum. Roxul covered with a thin rubber, plastic or wood veneer membrane will absorb low frequency vibrations while the membrane is reflecting the higher frequencies. Your drywall covered insulation should impart some bass trapping at very low frequencies, but effective bass traps are not separated by a rigid barrier.

 

Also, at this stage of your project, keep in mind that a completely drywall finished room interior will be highly reflective, a leading cause of complaints about horns sounding shrill.  

 

It would be interesting if you were to set up a pair of loudspeakers in your room under construction and listen to the change as you install each sheet of drywall. 

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