Two way LCR for home theater

[NoMjolnir]

Hi there, I've been lurking on these boards for quite some time.

Were in the process of building a new house and with that a dedicated HT room. (see attachment)
The room is L 6.4 x W 5.0 x H 2.8 Meters

At this time I have Klipsch RF-83 and RC-64 as LCR and will use those when the HT is completed, but for a future upgrade I've been looking for DiY plans for home theater LCR's.

I'd like to build an active two way system (or three ? ). Zilch's Mega system caught my attention.
http://www.audioheritage.org/vbulletin/showpost.php?p=92390&postcount=419

I'm thinking of using the
JBL 2352 horn
http://www.usspeaker.com/jbl%202352-1.htm
2435HPL Compression driver.

From sub x-over (50-80hz) to horn x-over (800-1200) I was considering two Usher 15HM. Two of these placed horizontally below the horn. Seperate enclosures.
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=296-630

In the front of the room I will be building a false wall which can house the horn and seperate box(es) for the LF drivers. The LF boxes and the horn can be positioned by making a holdingshelf between the studs of the false wall, so the LCR's will be flush mounted in the false wall so to speak. The three front speakers will be positioned in ear level height with the perforated screen covering at least the center monitor. The front of the wall will be covered by acoustic panels and the unused cavity can be filled with fiberglass for bass trapping.



So is this viable, the 2352 horn + compression driver, Usher LF driver, behringer electronic crossover and one amp for each lf and hf for each of the three monitors?

[4343]

It might be difficult to match the center to the LR pair if it's the only one experiencing the HF rolloff of the screen. Maybe not, but if it was me, I'd put all the fronts behind the screen just to be consistent. Sounds like the horns should have plenty of output, and losing some through the screen would be no big deal...

[NoMjolnir]

It might be difficult to match the center to the LR pair if it's the only one experiencing the HF rolloff of the screen. Maybe not, but if it was me, I'd put all the fronts behind the screen just to be consistent. Sounds like the horns should have plenty of output, and losing some through the screen would be no big deal...

I'll be using a SMX curved perforated screen, supposedly the loss is minimal. I guess I can experiment and take measurements when the time comes.

So, guys, has anything like this been done before? Perhaps there is another DIY HT LCR project you could point me to for ideas and inspiration?

The reason I chose the 2352 horn is because size is no issue and and the spread fits nicely for an LCR since they are supposed to be point sources and there will be less room interaction.
I'm unsure about compression driver though.
I chose the Usher LF driver because it's been getting alot of positive feedback from other projects. The response seems to fit well for an 800-1000hz x-over. With the behringer digital xover I'll probably use 24 or 48 db db/octave rolloff. Perhaps there is a JBL model which would be better suited to handle 80-1000hz?

[pos]

Just for inspiration, here is Greg Timbers' take on a DIY HT system:
http://www.audioheritage.org/vbulletin/showthread.php?t=9951


Perhaps there is a JBL model which would be better suited to handle 80-1000hz?1200FE?

[NoMjolnir]

Just for inspiration, here is Greg Timbers' take on a DIY HT system:
http://www.audioheritage.org/vbulletin/showthread.php?t=9951

1200FE?

Breathtaking!

[NoMjolnir]

http://www.partsexpress.com/pe/showd...number=296-630 (http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=296-630)

Are there any drawbacks for using an 15"'s up to 800-1000hz? cone breakup etc? Should I perhaps opt for a three way with the 15"'s working up to 200-300 range and have multiple 6.5" or 8" work up to 800-1000hz?

[NoMjolnir]

Ok, let's see if I get more feedback if I take a different angle here.

I've heard the Klipsch Thx ultra II monitor and this is more natural sounding than my RF-83 but lacks dynamics and attack. I'd like something that does both, natural sound with no harshness and dynamics that'll knock your breath out.

I would like to diy, three monitors for LCR use. Is it possible to build something which would demolish the KL-650 thx ultra II LCR and the Klipsch RF-83 / RC-64 combo, possibly rival the Juibilee?

[JBL 4645]

NoMjolnir


Watch some of these rare interviews with Mr. Tomlinson Holman AKA (THX) because what the rest of the guys said about placement behind the screen is the best place, but there’s (more to that).

Here’s the link to the page watch THX baffle wall and mathematics? Or you can watch the whole lot.

http://www.audioheritage.org/vbulletin/showthread.php?t=12476 (http://www.audioheritage.org/vbulletin/showthread.php?t=12476)

[NoMjolnir]

NoMjolnir


Watch some of these rare interviews with Mr. Tomlinson Holman AKA (THX) because what the rest of the guys said about placement behind the screen is the best place, but there’s (more to that).

Here’s the link to the page watch THX baffle wall and mathematics? Or you can watch the whole lot.

http://www.audioheritage.org/vbulletin/showthread.php?t=12476 (http://www.audioheritage.org/vbulletin/showthread.php?t=12476)

Amazing videos, Mr Holman was really interesting to listen to. I believe when he was about explain the .2 in 10.2 he he trailed off and talked about how satellites could be smaller because of the 80hz crossover so he never explained why .2. I wonder if the reason is that you can feel where sub 80hz is coming from even though you can't necessarily localize it by hearing.

I'm considering building a front baffle wall, with flush mounted lcr and and an LLT subwoofer solution.

[pos]

Maybe you should contact your JBL dealer and see if you can get some 1200FE.
If Greg Timbers chose these for its 80-800hz needs then I would say this is the best you can choose too.

[NoMjolnir]

I've modelled a thx baffle wall in my HT. I've angled the wall on the left and rigth so that the right and left channel will be 30 degrees on the sweetspot when flushmounted.

The cavity behind can be used for an LLT subwoofer, that way I dont have to build boxes.

[Mr. Widget]

Is it possible to build something which would demolish the KL-650 thx ultra II LCR and the Klipsch RF-83 / RC-64 combo, possibly rival the Juibilee?Sure.

Hell, demolishing the Jubilee isn't all that difficult either. What's your budget?


Widget

[JBL 4645]

NoMjolnir

I like the approach that you’ve taken at the last minute.


What is the size of the loudspeakers, in relation to the depth behind the baffle wall area? Some (lean way) well be needed to get easy access to remove them if a fault was to occur, say a blown driver?

The professional THX baffle walls have access from behind the wall where you’d climb up a ladder and therefore be able to maintain and damage.

http://www.homecinemachoice.com/articles/hccarticles/interviews/GrahamHartstone/PinewoodStudiosSpeakers.jpg
Pinewood Studios England

This is what a typical THX screen looks like at the Empire Leicester square London.
It’s more of an art with interior architectural design as well.

http://forum.ecoustics.com/bbs/messages/289508/362481.jpg
Empire Leicester Square London

The Empire Leicester Square London a JBL installation!
http://www.audioheritage.org/vbulletin/showthread.php?t=13057 (http://www.audioheritage.org/vbulletin/showthread.php?t=13057)

THX screens usual use plasterboard but that can be a messy affair. There are other types of (affordable materials) to use for a (baffle wall) that don’t cost.

Don’t forget the absorbent material to cover over the (barrier wall surface), because that part where Tom Holman, mentioned the (reflectivity bouncing around behind the screen) was fascinating

Here is a basic how it works sort of thing at the THX website.

Behind-the-screen baffle wall
http://www.thx.com/cinema/builtTHX/baffle.html (http://www.thx.com/cinema/builtTHX/baffle.html)

16 feet in width

18 feet in length

The length of the HF horn is what I looked at because of the shrinkage of the rooms depth will decrease once you place this and the (compression driver on the back) I think another 3” of room depth space will be lost, 13” for the HF and compression driver?

Overall Length 10" / 254mm
http://www.usspeaker.com/jbl---2352-size136.gif

So plain out the mounting depth around the centre part of the baffle a few times over. I know it sucks when the room shrinks down.


Or you can use a flat area surface that will more in you’re favour as it will be far easier.

[NoMjolnir]

Sure.

Hell, demolishing the Jubilee isn't all that difficult either. What's your budget?


Widget

For the front LCR the budget is around 2000-3000$ each.

If I use electronic crossover that is not included in the budget, neither is amps.

For the surround and surround back channels I want to take my time and experiment with direct radiators and sound sprayers. So for now I focus on the LCR.

[JBL 4645]

NoMjolnir

Evening

I’ve just been looking around Google image and stumbled on a different loudspeaker management crossover system. Myself for example, I’m using a Behringer DCX2496 a few others here also use them in the home. But a found a different one and I just need a few extras minutes to research it and look for the best low prices.

Edit

Omni drive compact plus loudspeaker management crossover system.

Whoa BUGGER ME! £2,419.99! That is a bit over the top!
http://www.ultimate-av.co.uk/acatalog/signal_signal_bss.html (http://www.ultimate-av.co.uk/acatalog/signal_signal_bss.html)

http://www.discostudio.co.uk/images/shopimages/4797.jpg

I’d stick with the Behringer DCX2496 as the above will cost an arm and leg! :blink: It’s a good looking one I must say I do like the appearance of it.

But just in case you win the national lottery here’s a user manual to skip though. It’s not the only loudspeaker management crossover as there are a few more like the (dbx4800) that are THX approved and used in only one cinema the Empire Leicester square. And that has four inputs with eight outputs configurations, but still its around the £2K price tag range.

Omni drive compact plus loudspeaker management crossover system user manual pdf file
http://www.usc.edu/student-affairs/gzcoffee/printable/Technical-Audio-Omnidrive.pdf (http://www.usc.edu/student-affairs/gzcoffee/printable/Technical-Audio-Omnidrive.pdf)

dbx 4800
http://www.dbxpro.com/4800/4800.htm (http://www.dbxpro.com/4800/4800.htm)

[NoMjolnir]

:blink::blink::blink:

Think I'll stick to the Behringer :D

One more thing, I know one place I'm going to visit the next time I'm in London.... ;)

[JBL 4645]

:blink::blink::blink:

Think I'll stick to the Behringer :D

One more thing, I know one place I'm going to visit the next time I'm in London.... ;)

NoMjolnir

LOL yeah let me guess it called the Empire! :D You should check it out 56KW and it make any, any, film sing to your expectations! I measured 120dbc at the front of the cinema back on 26th July 2007 Transformers, the pressure and depth of the low end was unquestionably deep. The original JBL THX specification was 13KW! And even that was in my face! So you can imagine what 56KW would be like.

I’m hoping to visit the Empire when Indiana Jones IV opens on opening day May 2008.

It’s truly a JBL inspirational cinema for any JBL fan!:p


As for the crossover it will only take a small percentage of the planed budget and thou a few like said use here on this site it’s a not a bad investment that works and like all things it has its pros and cons.

The crossover filters are easy to select and use, after you’ve had a few hours (hands on) experience with it.

It does generate a little noise, I’m not going to lie about that, a little hiss on one of the HF band outputs, mostly on the right channel, but it depends on how you set the unit up and use it, with the amplifiers.

Three stereo amplifiers will do a common basic two-way output over its 6 channel outputs.

Or four-way but then you risk the cost escalating because you’ll need at least two DCX2496 because you’ll only have 2 inputs to use then and only (three outputs LMH, LMH)

Its easier to stick with (left LH centre LH right LH) and then use a second one for the surrounds if you wish so, to do (sidewall surrounds and centre back surround) in the same fashion as the fronts.

A third can be used for sub bass arrays of subs placed in the baffle wall and then with the DCX2496 you can tailor the sound to the, likens of the rooms inner surroundings.

[NoMjolnir]

THX screens usual use plasterboard but that can be a messy affair. There are other types of (affordable materials) to use for a (baffle wall) that don’t cost.


Baffle wall 16cm, perhaps 30mm chipboard(?) on each side and 100mm insulation? Chipboard would be easy for flushmounting of drivers. The front of the baffle wall should perhaps be 30mm MDF for mounting of the drivers ?



Don’t forget the absorbent material to cover over the (barrier wall surface), because that part where Tom Holman, mentioned the (reflectivity bouncing around behind the screen) was fascinating


For the ceiling I'll use black/grey ecophone acoustic panels. I was thinking I could use the same on the baffle wall. Side and back walls will be greyish and floor will cherry stalls (?) but with carpet between seating area and front wall.



The length of the HF horn is what I looked at because of the shrinkage of the rooms depth will decrease once you place this and the (compression driver on the back) I think another 3” of room depth space will be lost, 13” for the HF and compression driver?


Hopefully with 40-45 cm I'll be able to access this area and there will be more space from the back wall to the sub drivers. I'm considering using 4 soundsplinter 18" in an LLT configuration, these drivers will also be flushmounted in the baffle wall. The baffle wall should probably be anchored to the back wall considering the moving mass of the 18"'ers.

I presume that the LF drivers of the LCR's will have their own enclosures behind the baffle wall.



I've made a new sketchup model just for the ht room. The inner walls, ceiling and floor are mechanically decoupled creating a room within the room. In the back I'll have bass trapping in the corners. The entire ceiling is 280cm with 30cm of insulation before ecophone acoustic panels making it a bass trap.

[JBL 4645]

NoMjolnir

Afternoon there sorry for the long post.

Oh yes I like that I what you’ve done with the computer model.

So I take it the front loudspeakers LCR will be ported from what position? Front ported or rear ported because nearly all the cinema types are ported from the (front) subs as well.

So the 18” sub bass drivers, won’t have there own enclosure or will they? If that’s so will you install them into the fittings, that is the hole in the wall and then use some wood edging to over up the gaps around it, not that it’s a paramount issue.

The wall should have an (absorbent material) that comes of a role and from what I have seen in pictures, it appears to be fitted all around the edges or you can staple it to the wood, that’s just a fast and cheap option.

If I get an opportunity like you have at the moment I would like to do the same thing, but there’s no point if you don’t have a video projector.

I must say that the few THX screens that I have been to in the UK and sound engineers in the UK take great pride in getting the best and more out of it, that’s just a personal opinion of mine.

There was one other THX screen that used to be THX certified during the late (1988 to 1999 2000)? High Welcome UCI or CIC as it used to be called.

This cinema could do dual 35/70mm film presentations and had JBL 4675-A five screen and two JBL 4645 subs not sure how many JBL surrounds they had or what model they where.

But when I saw Arachnophobia (1990) at the cinema I was BLOWN AWAY the bass sub bass was very tight it was in my (chest stomach face) all over me and still to this day I can remember what it felt like, call it if what (THX syndrome)

There’s only so much my JBL control 5 and 1 can do at the front, given where there positioned, there’s only so much the sub bass extension can do within technical tolerances and there is only so much the LFE.1 can do when playing Arachnophobia on region DVD.

There seems be a few low frequencies that need addressing or I need larger matching JBL for LCR. Most of the deep bass is generated from the centre channel, but like I said there’s only so much each loudspeaker is capable of, I’m not trying to put my home cinema down, it has limits and as long as I know where it can go and where it can’t go I tend to keep it within its (technical tolerance level).