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Old 2nd July 2008, 03:20 PM   #1
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Default Room design, DIY in-wall speakers, IB subwoofer, comments?

I'm getting married in November and I've been able to convince my fiance that having a home theater is a good idea =). She prefers a more inconspicuous design, so I decided to try in-wall speakers with an electric screen and IB subwoofer. The in-wall speakers will most likely be an in-wall version of Jay_WJ's Usher 8945P and Peerless HDS tweeter 2-way and the IB subwoofer will most likely be 4 AE 15" IB woofers in a manifold configuration with a ~16" opening in to the listening room. Detailed drawings are below. They show lots of relevant distances and angles. The listening position on the couch is what I designed as the primary listening position for TV and movies and the position in the middle of the room would be for 2-channel listening (I'd probably drag the recliner over to that spot). Comments, feedback, suggestions, personal experiences? Thanks!

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Old 2nd July 2008, 10:02 PM   #2
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While your at it you might consider a couple of small rear surrounds for a 7.1 system. I think it is a little nicer sounding than the 5.1 setup.

Also, if you only have one screen you may prefer a theater aspect ratio instead of a 16:9. I think it is preferable to have the widescreen movies optimized more than HD TV images. Then you can just run 16:9 images with white bands on the side. Or you can hang some black borders on the sides which is easier to do than hanging temporary borders on the top and bottom.

What I have done and works really well in a room where you can't paint the viewing wall a black or dark gray color is to use a screen that is somewhat bigger than you need for the distance you are viewing and mask off a large black border. I have a black border about six inches wide top and bottom and eight inches wide on the sides. It helps to focus your eye on the movie image a lot better than the narrow 2 inch wide black border.

Of course it is personal preference but this is what I would recommend:

My HT room as about the same size as yours but the viewing distance is only 8 feet away for me. You are more like 12 feet so you can use a little bigger screen. I'm using something like an 85 inch you could probably use a 95-100 inch.
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Old 2nd July 2008, 10:40 PM   #3
Jay_WJ is offline Jay_WJ  United States
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A quick comment, m0tioin. I haven't precisely modeled excursion limits of your system (i.e., HP filtered 2-way at 80 Hz and the IB subwoofers). And I know IB subs require greater excursion. Even so, four AE IB15's may be an overkill? You may want to model the system's power handling with filters in. The 2-way satellites, even if high-passed at 80 Hz, won't give you the max SPL of Dolby reference level at your listening position, anyway. I hope you and your fiance's goal is not the Dolby reference SPL.

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Old 3rd July 2008, 09:43 AM   #4
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The screen is way too small to provide a cinematic sense of impact on scope movies and somewhat small for lower aspect ratio films. You'll get a better sense of immersion out of a larger screen without standard definition DVDs getting too soft or bad transfers becoming unacceptable.

You want to look at an 8' wide 16:9 sreen (110" diagonal) or 4' high constant height setup which would be 113 x 48".

With the scope screen 1.85:1 academy movies will be sized as if you had a 102" diagonal 16:9 screen and scope movies 130". The smaller low aspect films are a feature not a bug.

Decent anamorphic scope DVD transfers look good at that sort of subtended field of vision and the scope DVDs you'll be watching are most likely to be either epic classics with nice transfers (because they were remastered) or newer films (because we figured out how to do transfers and encode MPEGs for better than laser disc quality). I think they look a bit sharper than lower aspect ratio films, with theory suggesting that the lack of entropy in the encoded black bars allows for more bits to encode the higher frequencies in the rest of the image. Older poorer lower aspect ratio films will be small enough to still look acceptable (you see less with the lower subtended field of vision) and "big" (perceived size seems to be mostly a function of how many steradians the screen subtends).

HD won't be an issue. Without fim's judder 1920x1080 HD is sharper than a nice 35mm print which the SMPTE guys have found to look great at a 45 degree subtended field of vision.

This assumes you're using a projector with acceptable screen door. CRTs are completely imune with proper setup and scaling, 1080p LCOS projectors are fine on large screens, and I've yet to look at other digital projection technolgies (For four years I ran an 87x49" screen (100" diagonal) with a 9" CRT projector and 11' viewing distance on low aspect ratio pieces and 9' on nice scope transfers before I sold my home and moved through a series of apartments and states. Next time I'll do a scope screen so I don't have to move my butt especially now that we have pre-recorded HD where it stays sharp closer).

The sharpness vs. immersion trade-off is a personal thing. You pretty much need to live with a projector long enough to start thinking of it as a small movie screen instead of a big TV at which point you can figure out what works for you. As a reference point, sitting as far as you can from the screen in a decent THX certified theater produces a 36 degree subtended field of vision which is about what you get 12' from an 8' wide (110" diagonal 16:9 screen). Most of us sit closer than the last row. Using the projector you'll ultimately live with would be a big deal with older digital projectors but isn't an issue with LCOS and should be better with DLP/lCD at 1920x1080.

When not running dipole side surrounds, upgrading from 5.1 to 7.1 produces a quantum improvement in the immersiveness of the surround field when you're using a processor that generates 4 surround channels (I like my old Lexicon DC-1 with Logic-7, but some of the Dolby Prologic-2 processing and Meridan's Tri Field should be similar)

You may get too bassy when seated near the rear wall and things might get a little harsh if its untreated.

I'd move everything closer (that would tolerate a smaller screen which would be brighter, and get you better detail and clarity since you're closer to the speakers). I'm married too and my favorite honey tolerated that although the equipment and construction project were there first.

Also note that if you want reference level home theater you'll probably want to do something about your room acoustics for that to work (untreated rooms are too reverberant).

Attachment of my last front projection setup is attached. 11' seating distance to 87x49" screen, 46x13" speaker baffles with tweeter dome apexes 4' off front wall 96" apart, 13x19x8' room.
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Old 3rd July 2008, 02:47 PM   #5
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Thanks for the replies!

Hezz:
As for the rear surrounds, I'm not sure where I'd put them because (as I hope the picture implies) the room continues on past the bottom of the picture. The only idea I have to to mount them in the ceiling facing downward and I'm not sure of the sonic implications of this.

Also, this setup will be used approximately 50% TV, 25% movies, 20% non-critical listening music, and 5% critical listening music. Because of this I like the 16:9 aspect because, well, thats what HDTV is =).

Also, I'm somewhat limited in screen size for two reasons. I plan to use this system to watch TV during the day and the room is not light controlled (there is a double window with curtains on the right side of the room). Also, I don't want to move the ceiling fan much further back because then it wouldn't really cover the room anymore. I'm thinking I want to use a Panasonic PT-AX200U because of it's high lumen output (2000 rated, close to 1900 measured by ProjectorCentral.com).

Another possibility would be to scrap the projector idea all together and mount a 50" plasma or LCD, but thats not really solving anything with regard to size.


Jay_WJ:
As best I can tell with a 4th order HP filter at 80Hz the 8945P will not be excursion limited. WinISD reports a max SPL at 80Hz for the 8945P in a 1-3 ft^3 enclosure (I'm not sure how much space is going to be seen by the woofer mounted on the wall, but not more that 3 ft^3) is about 102dB@1m. Add in room boundary gain, but subtract for distance and it's maybe 98 - 100dB max? I think this should be loud enough. If not I can always try crossing over to the IB a little higher (100Hz, 120Hz).

With regard to the IB sub design, I'm not sure how much you've looked into them, but they behave a little differently than normal sealed subs. The reason I've included 4 15" as opposed to 2 15" is I plan to EQ them flatish to 10Hz. WinISD reports max SPL for 4 15" at 10Hz as ~104dB. I doubt I would ordinarily listen that loud, but the additional 2 drivers only add marginal cost to the whole system and it decreases the excursion for a given SPL by 1/2, so hence lower distortion. Basically I'm trying to say I planned for 4 15" not for SPL headroom, but for lower excursion and distortion.

I don't know what SPL dolby reference level is =).


Drew:
Wow, thanks for your huge, detailed reply. I think most of your comments are addressed above, but you do bring up an interesting point and thats di/bipolar surrounds. I don't exactly know how you accomplish this in-wall, but I'd like to keep my design completely in-wall. I see you have Orions! =) Awesome, how do you like them?
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Old 3rd July 2008, 03:02 PM   #6
boone is offline boone  United States
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Jay,

Will the no baffle step version of your Usher/Peerless 2-way be posted on your web site?

Thanks
boone
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Old 3rd July 2008, 04:20 PM   #7
Jay_WJ is offline Jay_WJ  United States
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Quote:
Originally posted by m0tion
As best I can tell with a 4th order HP filter at 80Hz the 8945P will not be excursion limited. WinISD reports a max SPL at 80Hz for the 8945P in a 1-3 ft^3 enclosure (I'm not sure how much space is going to be seen by the woofer mounted on the wall, but not more that 3 ft^3) is about 102dB@1m. Add in room boundary gain, but subtract for distance and it's maybe 98 - 100dB max? I think this should be loud enough. If not I can always try crossing over to the IB a little higher (100Hz, 120Hz).

With regard to the IB sub design, I'm not sure how much you've looked into them, but they behave a little differently than normal sealed subs. The reason I've included 4 15" as opposed to 2 15" is I plan to EQ them flatish to 10Hz. WinISD reports max SPL for 4 15" at 10Hz as ~104dB. I doubt I would ordinarily listen that loud, but the additional 2 drivers only add marginal cost to the whole system and it decreases the excursion for a given SPL by 1/2, so hence lower distortion. Basically I'm trying to say I planned for 4 15" not for SPL headroom, but for lower excursion and distortion.

I don't know what SPL dolby reference level is =).
Dolby reference level is defined as 105 dB peaks from any surround channel, and 115 dB bass peaks from the LFE channel - as measured at the listening position. Yes, this is very loud. People normally don't need this in a home setup. Any single 7" midwoofer based 2-way satellites, high passed by a usual AV receiver's BW 2nd order 80 Hz filter, can't play this loud without distortions. In-wall speakers can be a bit better because of no baffle step loss.

You may want to consider using an in-wall cabinet of 0.3 to 0.4 cu ft filled with damping material. This will give you a more precise 2nd order rolloff, which will, when combined with a receiver's BW 2nd order filter, give you an acoustic LR 4th order HP rolloff.

As for the IB subs, if your goal is flat to 10 Hz by EQ'ing, the story is different. But do you really need 10 Hz? I'm not sure how many movie soundtracks contain 10 Hz tones. John kreskovsky recommends using a subsonic filter for IB or dipole woofers to prevent overexcursion.

-jAy
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Old 3rd July 2008, 04:30 PM   #8
Jay_WJ is offline Jay_WJ  United States
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Quote:
Originally posted by boone
Jay,

Will the no baffle step version of your Usher/Peerless 2-way be posted on your web site?

Thanks
boone
It will be when I get a chance. But I don't know when I will update the page. If you need this design, send me an email.
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Old 3rd July 2008, 04:52 PM   #9
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Jay:

Wow, thats loud. No I don't think there is a reasonable need for that level of volume. Again, I don't even really consider what I'm trying to do "home theater" proper because my goal is not to recreate a movie theater experience at my house. It's just to have a big TV that I can play movies and music on that has excellent sound and picture quality.

The EQ flat to 10Hz isn't really a "goal" per-say, but it just seems like something that would be easy to do. The subwoofer models -9dB @ 10Hz, so it just seemed like low hanging fruit to apply some EQ either via my HT receiver or a stand-alone DSP device to combat room-modes and give good frequency extension. I suppose, depending on source material, hearing sounds as low as 10Hz may not be pleasurable in which case I'll have to figure out how to apply a subsonic filter of some kind.

I haven't actually checked the depth or stud-spacing for these walls yet so I may end up implementing some sort of barriers in the wall above and below the speakers to limit the total volume and provide some rudimentary bracing. That will probably be addressed at the time of installation. Are you sure that the subwoofer x-over in HT receivers is 2nd order? For some reason I thought it was 4th...
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Old 3rd July 2008, 05:04 PM   #10
Jay_WJ is offline Jay_WJ  United States
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Quote:
Originally posted by m0tion
Are you sure that the subwoofer x-over in HT receivers is 2nd order? For some reason I thought it was 4th...
Yes, it is. BW 2nd order high pass (-3 dB at the xover freq) and LR 4th order low pass (-6 dB at xover freq) filters. This is a THX standard adopted by most of brand AV receivers (e.g., Denon, Yamaha, Onkyo, etc). The reason is, when combined with most of mid to small sized satellite speakers' natural rolloff, a BW2 HP filter results in a LR 4th order rolloff. And for your IB subs, you don't want to use any external LP filter in addition to your receiver's since it's already LR4.
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