LSim 707 For a custom home theater

diverdog

I was on the fence about these but at $855 and free shipping they are a tremendous value. I just bought 3 707s and 6 703's for an 9.2.4 Atmos home theater I'm building. Center channel will be a 707 behind the 115" diag screen. left and right 707's will be in the room flanking the screen. These will be my first Polk's ever. I won't have the room ready for 6 months so I'll replace the Infiniti towers I have in my living room with the 707's to break them in and give a critical long term listen.

Some of the other speakers I was considering are Martin Logan 60XT and Golden Ear Triton 1.

I'm an engineer that owned a pro audio design build company for many years. I will be doing all of the design, construction, acoustical treatment and installation myself. I have a new semi custom house with a dedicated room for the theater. They eliminated the windows and a door that opened to a courtyard and installed two extra 20 amp power circuits, #12 wire to the speaker locations and balanced twisted pair to multiple sub locations. The room is 19.5' wide by 19' deep with 10 ' ceilings. I wanted 12' ceilings but the same house with 12' was $200k more! I'll be constructing a new wall in the front of the room 2' out to make the room 17'x19.5. It will also give me room for the 707 behind the screen. Viewing distance will be ~10'. All of the walls and ceiling will be damped with an ASC wall damping system. I'm not concerned too much about noise transmission but I want the walls and ceilings to act as diaphragmatic bass absorbers and to be properly damped so they don't re radiate bass back into the room.

Right now I'm mostly concerned with getting the room construction and treatment planned and underway. I've found that a good room can make even bargain equipment sound damn good. I'm pretty pragmatic and brand agnostic about equipment choices and I'm looking for bang for the buck. More about additional equipment later but I'm pretty sure I will be getting a processor and separate power amps rather than a receiver.

WLDock

Make sure you document the build and post up. With you being in the Pro audio world, you might like the fact that the LSiM line measures pretty flat and have a nice level of accuracy to them. You should be able to tune this setup to get the sound to your liking. Its says a lot that you went with conventional speakers over horns.

If you have not seen it, here's the Tech Brief for the LSiM line. Great read!
http://www.sohmerassoc.com/cedia_2011/sa_cedia_2011_downloads/polk_audio/LSiMSeries_technical_brief.pdf



Your room seems like a candidate for four BIG subs!
https://stereointegrity.com/product-category/subs/
https://www.parts-express.com/dayton-audio-um18-22-18-ultimax-dvc-subwoofer-2-ohms-per-coil--295-518

diverdog

WL, thanks for the tech brief. Horns can be very useful and the latest ones can rival direct radiators for sound. But the size and cost make them unattractive for this room. I've built many monster subs for dance clubs and home use. Some of the arrays could hit 140+ db at 25 hz! For this room I'm looking for quality over quantity and I can buy way cheaper than I can make as my time is valuable. I like the sound and value of the HSU ULS-15MK2 and I'm going to start with a pair and experiment with placement to get the best response at the seating row (just one row of 3-4 seats). I'm pretty sure two will work fine for level and coverage.

WLDock

I'm a fan of HSU and sealed 15's also. The ULS will give you the quality you are after.

diverdog

Excited that Amazon straightened out my order and the speakers have shipped.

A bit about the center channel. It will be a 707 behind a acoustically transparent screen. I love the sound of three identical speakers across the front. I really want the dialog to come from ear level as I can really notice the vertical displacement of the center channel when listening to the system I have with my 90" monitor. I don't like the lobing from horizontal arrays either. I know there will be a bit of HF attenuation but that can be easily fixed with EQ.

Even the wife is excited as she has a hearing issue and she was blown away when she first heard my system with a good center channel for dialog when we started dating 5 years ago. I promised her the new room will be better in every way.

mdaudioguy

Three towers across the front makes a great soundstage! Three RTi10s here. Unfortunately, not with an acoustically transparent screen. My pull-down screen comes down right to the top of my center tower. I use Yamaha's "Dialog Lift" feature with RTi4 presence speakers mounted high and wide, and it really works well. Voices do seem to emanate from the center of the screen. I'd have liked to have done an acoustically transparent setup, but my room wouldn't allow for it.

diverdog

Mdaudio guy I'm very lucky as I can do as I like in this room. I've waited a long time to be able to do this. All is not perfect though, the room dimensions are not ideal but I'll change one wall and work around it with acoustical treatments.

diverdog

So after two years in this new house purchasing these speakers has got me off my butt to get this room started. I promise no lightning, thunder, plasma or conventional current will be used in the construction.

Unfortunately the first work will be to move all of the stuff I have stored in the room, pulling up the carpet and then tearing out the dry wall off three interior walls. I need to change the wiring layout as I changed where I want the screen wall to be and the ASC IsoWall system needs to be mounted directly to the studs.

Then I will stud out a new 2x6" wall 24" out from the existing outside wall giving me a 17.5' room depth. The wall will have a pocket for the center channel 707. The wall will also have the IsoWall system making it a 19.5' X 10' diaphragmatic bass trap. The 24" void behind the wall will be filled with blown in fiberglass as will the other walls. The different wall sizes and depths of the space behind the walls will absorb different bass frequencies < 250hz. The multi layer floating construction is also damped so the walls don't ring much and reradiate sound into the room. Unfortunately it is not tunable. The only system I know that is tunable is the carbon wall from Acoustic Fields. At about $30k it is out of my budget. Tunable in room bass traps don't have anywhere near the needed attenuation or low bass capacity for theater use.

The ceiling (5/8" drywall on 2X10 rafters) will be left as is because the sprinkler system, lighting, HVAC and 16" of cellulose insulation make it a PITA and out of the budget to deal with for bass control.

Next post I'll talk about diffusion and absorption for mid and high frequencies. When I get the room cleaned out I'll post some baseline pictures and then progress pics along the way.

Clipdat

Thanks for the update!

dromunds

What are you going to be using for speaker cables for the front? Can make a significant difference IMHO.

diverdog

#10ga CL2 rated cable running through the walls. They will poke out with no jacks at the wall and connect directly to the speakers.

I'm not a believer in magic speaker cables. If you can hear a difference in the sound it's because the cables are EQing your system. You may prefer the sound but a $1 capacitor or the EQ on your equipment can do the same thing.

The one exception to this is using an appropriate gage wire for the distance run. Controlling the woofer properly requires a lot of current to start and stop the driver. My longest run to the front speakers will be ~ 30' so I'm using #10ga. I may bi-wire since the 707's have that capability.

Back in the day I participated in a double blind test of some very expensive speaker cables VS #12 and there was no statistically significant difference among the trained listeners in the results. Even though it would be very easy to do, to this day I've never seen a professionally conducted published double blind test on cables with a statistically significant result. If you know of any please point me in that direction.

In short I don't want speaker cables that modify the signal, just pass it on to the speakers.

I feel the same way about equipment power cords. Three feet of magic wire is not going to make a difference compared to the 1000 miles of crappy cable behind the wall. I will use multiple circuits with hospital grade 20 amp receptacles and #10 cable to the main breaker box to make sure there is minimal voltage drop to the equipment.

Low level interconnects will be balanced TP where possible with pro quality XLR connectors.

HDMI is one area where a better quality interconnect is important. The very high bandwidth / frequency makes the dielectric, wire twist and connectors way more critical than at audio frequencies, but even for these no magic is required, just solid engineering.

diverdog

I ran a resonance analysis on my 19.5x17.5x10 room and although its not optimal it's not real bad. I do have some pretty bad floor to ceiling resonances so I've decided to add a layer of 1/2" dry wall with Acoustic Sciences Corp. wall damp between the existing 5/8" layer on the ceiling and the new 1/2". Not as good as the floating ASC system but no way I'm going to rip out the ceiling.

On the power side I have a 50A 220V circuit pulled for a spa that I'm not going to use so I'm going to disco the outlet and move it over to the home theater. The side wall that will have the equipment cabinet is common with a garage. I'll put a sub panel there. Since the interior sheet rock will be ripped out it will be simple to add new outlets and home runs to the sub panel. I'm planning on two circuits on the front wall, one on the far side wall, two on the rear wall and four on the equipment side wall. Three will be inside the equipment cabinet and one on the wall. All will be 20 amp outlets wire with 10ga to limit voltage drop. I'm not sure how many subs I'll be using (starting with 2) and where they will be located, and I want each sub to have it's own dedicated circuit so there are available circuits on each wall. In the equipment cabinet, one circuit for the front 3 channel amp, one for the surround channel amps and one for signal processing.

Viking64

Hey, Horshack! Did you hear Epstein died?

diverdog

Yep he hung himself with a $100,000 speaker cable when he couldn't hear the depth of the sound stage increase. Perhaps you would rather I describe how I'm going to polish the speaker cabinets so the sound is smoother? LOL There is a science to superior sound reproduction and the room is a big part of it. It's not sexy like esoteric components or add on's like magic wire but it makes a huge difference.

Viking64

diverdog wrote: »

Yep he hung himself with a $100,000 speaker cable when he couldn't hear the depth of the sound stage increase. Perhaps you would rather I describe how I'm going to polish the speaker cabinets so the sound is smoother? LOL There is a science to superior sound reproduction and the room is a big part of it. It's not sexy like esoteric components or add on's like magic wire but it makes a huge difference.

I was referring to the SPAMMER who posted above me named "HARSHAK".

I didn't quote them because they had SPAM links in their post.

shs

Your setup sounds great. I am running 705 left and right with a 703 for the center with the tweeters and midrange all at the same height. Front soundstage is great. I am using 4 702F/X for surrounds in a 7.1.4 Atmos setup with 2 15" Velodyne subs. I am driving my bed layer speakers with a D-Sonic amp that can do 800w x3 for the front 3 and 400w x4 for the surrounds. The Polks can handle the power and actually seem to thrive with it. When you get to that stage don't skimp on the amps!

diverdog

Viking, got it. Thanks. SHS, thanks for the input. I'm still up in the air on processing and power amps but for amps I'm leaning towards Emotiva with a three channel for the fronts and 2, 5 channel for the surrounds and overheads. Hoping when I'm ready the Emotiva and Monoprice 16 channel processors will be sorted out.

tonyb

bump

diverdog

TonyB, the wife has me running around working on our backyard landscaping project so I've put this on the back burner a bit. I am doing the bill of materials for the electrical, wall construction and acoustical treatment. Started to empty the room of all the stuff we have stored from our move. Sorting what stays, what get sold and what gets thrown out. Unpacked all 6 of the 803's and found a damaged one that has been exchanged.

diverdog

So I'm finally moving forward with this project. Back yard and other projects had to be done first to preserve martial harmony if you know what I mean. Ordered the ASC wall damp supplies and got a nice black Friday deal. I have a bunch of nasty work to do ripping out the wall board and ceiling. I've decided to do the ceiling too since its such a big surface. The attic insulation will be fun to remove! At least it will be much easier to upgrade the power wiring.

Still no decision on the processor and power amps. But I'm still leaning towards the Emotiva. The only additional equipment I've purchased is 4 Polk 900-LS ceiling speakers for the Atmos overheads. They are voiced to match the LSiM

dromunds

You were wise to purchase the LSiM’s when you did. Good luck going forward