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Bigus 04-10-2019 01:47 PM

Suggestions for theater speaker/system topology
 
For years I have been able to dream about my ideal theater speaker setup. "Dipole done right" I guess you could say. Enough surface area to reach reference level at seats, small enough high frequency drivers to be nearly perfectly dipole up to over 5kHz.

I built a prototype sans woofers. I built a prototype multichannel amp to power it - 14 channels in 2u chassis. Sounds fantastic. Still tweaking xo.

Expanding this to the entire theater would net nearly 180 total drivers and >150 channels of amplification.

The complexity has started weighing on me, particularly as our home construction has finally started and the idea of how much time it would require to go this route has started to become more of a reality. And now the best source I had for high performance amplification for that many channels in reasonable space and budget is no more, so it would be back to the drawing board on amplifier front.



So I'm open to suggestions. I will have a large room to work with, something like 25 x 30 x ~10. Speakers can be off the wall a couple of feet (had planned this with dipoles). Sound quality is every bit as important as sound quantity. The room will be designed and treated to enjoy a piano sonata as much as a star wars film.

I bought into the benefits of constant directivity years ago. Haven't quite bought into horns though. I realize that narrows the field quite a bit! But I'm here now asking so open to suggestions. Big fan of actives and may well stay that course especially if facing dozens of channels instead of hundreds.

More of a DIY guy especially for the cost but haven't completely ruled out a retail solution.

My dream was dipoles on steroids. Afraid that might turn into a nightmare! What would your dream be?

Trimlock 04-10-2019 02:22 PM

You bought into directivity but you aren't sold on horns? That's sort of a major proponent for horns lol.

trilkb 04-10-2019 02:28 PM

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My dream is qsc 2150 clones, or titan 615, or JBL screen array. I'd use volt 10s for surrounds and then do 18 JBL 12s in a baffle wall with the mains.

Bigus 04-10-2019 03:21 PM

Quote:

Originally Posted by Trimlock (Post 57883392)
You bought into directivity but you aren't sold on horns? That's sort of a major proponent for horns lol.

Yeah I know not exactly the most solid application of logic there.

To be a little more specific about where I'm coming from...

1. I believe the science behind constant directivity is rock solid. And there is something in common about the sound of all approaches I really enjoy.

2. Love the sound of ribbons on their own but causes real difficulties in driver spacing vertically.

2. Had magnepans for years but there are shortcomings of planars that are very difficult to work around.

3. Omnipolar is a valid choice but the room becomes even more critical, whereas controlled directivity like horns and dipoles takes a lot of the room out of it.

4. Horns have some intrinsic issues with resonance and honk as well as physical size that again complicates vertical spacing and lobing. Not out of it but haven't seen an ideal one for smallish residential spaces IMO.

5. That leaves traditional cone/dome drivers and dipoles, which is how I got where I am. But it resulted in a 10 driver design that is going to be complicated and time consuming to build multiples of.



So I'm here for ideas, suggestions, education, inspiration. Horns, omnipoles, line arrays, traditional direct radiating. Big room with big dreams.

gazander 04-10-2019 04:51 PM

I'm experimenting with an active setup for the theater, 28 channels just for the full range speakers. I'm using clearone xap800 ($30 on ebay), it has lots of filters and dsp... Sounds good to me, check it out.
I stumbled on to 3 sonamp 1250 with 50wpc and 100wpc bridged, high quality amp about 80lbs each with toridal transformer.

BassThatHz 04-10-2019 07:00 PM

I think I'll just have to be happy with what I've built thus-far.
I don't even know what my dream system would be...

It scares me to even think about it because I know I can't afford what I truly "want to have".
24 24's and 30'x40'x15' and 200kW would be a "good start" me thinks.

I don't really care about SQ in movies much, but bass and 2-ch is VERY important to me. It has to be dynamic, loud when called for, and as transparent as possible.
I don't really care what the technology "is" that makes that possible. Whatever works best!
Besides, technology is constantly changing regardless. Today's best is tomorrow's useless...

As far as the PQ goes, 4K HDR is "good-enough" (for me at least...)

Bigus 04-10-2019 07:28 PM

Bass will take care of itself regardless of speaker topology I think. I've got room for an enclosure in each front corner measuring in the many hundreds of cu ft, room down the sides for more, room in riser for nearfield. Expense is the only limit there.

I'll do some reading on line arrays and omnipolar designs. One of the things driving complexity with dipoles was the need to go to 4 way plus sub plus rear tweeter to reach output goals. Omnipole and line arrays can do that with a simpler 2 or 3 way.

Interested in any and all ideas and suggestions.

mhutchins 04-10-2019 07:53 PM

My suggestion is to try and find someone with DIY SoundGroup speakers that you could audition. The horn design that resulted from the crowd sourced collaboration is supposed to be pretty good and free of many of the common drawbacks associated with horns. Doubling down, I would suggest you find some Titans to audition and consider HTM12's for surrounds. 6 Volt 10 V2's would work well for Atmos and should timbre match fairly close to the other speakers.

If you can't find anyone nearby for an audition, try building an HTM-12 to get a feel for the sound quality you could expect from the rest of the lineup I mentioned above.

Mike

Bigus 04-11-2019 06:46 AM

I have considered building a diysg kit to see what I think.

Anyone here heard a Keele CBT based speaker in person? Was intrigued years ago but went a different direction in research. The line arrayish multitude of drivers would obviously have benefits for reaching reference level in theater.

PE has a kit... only a handful of reviews. I guess I could build a pair of those for a listen?

notfastenough 04-11-2019 07:33 AM

JBL also offers a CBT speaker that is pretty cool.

http://www.jblpro.com/china/products...eries/cbt70j-1

@Archaea could give some insights on response and whatnot. Personally, I've got some driver envy of his setup!

As far as line arrays go, I've only got a month of stereo listening under my belt with some TLAHs and certainly notice some compromise. I'd love to understand how to work with the vertical pattern a little more. I understand that the CBT designs are supposed to help with response there, but have not dove into the papers written on the subject. More than likely, I'll try out a WG speaker or designed CBT speaker of some sort.

Archaea 04-11-2019 03:36 PM

hey thanks, @notfastenough


If you are ever in the Kansas City area and fancy a demo, I'd be happy to oblige.


Someone was asking me about my thoughts on CBT speakers on a hardware forum I frequent called hardforum. I wrote up a fairly long post there, that I'll just link here rather than rehash it. When I get some free time I should move that post over to AVSforum, but at the end of the day it's just one guys opinion, and on such a subjective thing like a speaker...


https://hardforum.com/threads/lookin...ost-1044090440


My keenest advice in this new world of atmospheric audio, where objects can pan all over the room, is to acquire all matching speakers -- so the tonality of objects don't change as they move around the room. That doesn't have to be done with CBTs, that can be done with most any competent speaker. In my opinion/experience, an all matching speaker system hits way above it's price point for home cinema with the new codecs, DTS-X and Dolby Atmos.

Archaea 04-11-2019 03:47 PM

Quote:

Originally Posted by Bigus (Post 57886088)
I have considered building a diysg kit to see what I think.

Anyone here heard a Keele CBT based speaker in person? Was intrigued years ago but went a different direction in research. The line arrayish multitude of drivers would obviously have benefits for reaching reference level in theater.

PE has a kit... only a handful of reviews. I guess I could build a pair of those for a listen?


I reference the Don Keele CBT in my hardforum link above. It was impressive to be sure. I heard it at Axpona. I bought one near immediately on that demo alone and so did the friend I was with. @Randy Bessinger , do you still have your pair for sale? Randy likes buying gear to try, and ends up selling most of it. His full system is a JTR setup, I saw that he had his CBT's on the selling block after enjoying them for a while, so he can try some more new gear.

Bigus 04-11-2019 03:49 PM

Thanks Archaea, will certainly give that a read. The more I research CBT the more intrigued I become. I may buy a pair of the PE CBT36 kits to play with. Already have plenty of amplification and minidsp 4x10HD that would suffice.

Don't mind spending $1k per speaker for base layer of 11 speakers. I wonder if these may benefit from a midbass module at least for front channels given the smallish drivers used. Would cross at 60-80hz to competent sub system... but my dipole design was 4x12" drivers covering from 60-240Hz so I know there would be a compromise there.

Hard to imagine using these CBT arrays for height/overhead channels though! I mean, you could place on ceiling at wall/ceiling corners but by design there would be limited output at floor level.

Randy Bessinger 04-11-2019 04:18 PM

Hi Bigus. Just to let people know, Bigus is one of my heroes from the old days in the free for all subjective vs. objective debates in ultra high end forum. Was Randyb then randybes then. Engineer to MD as I recall. Hope that is going well.

As for the Parts Express CBT arrays, I did have them for sale but local delivery only. When they didn’t sell, I decided to do a simple 5.1 system with TV in small room upstairs rather than always using the theater room and projector for all TV watching. That is where they are now as close surround speakers (since they don’t localize easily). I would still sell them but I just think with their size, shipping would be prohibitive. When I was using them for two channel, I did use a minidsp HD with the eq file from Parts Express. My understanding is that eq assumed hard wood/tile floor rather than carpeted as I used them.

@Archaea , you finished yours?

Edit for clarity sake....Archaea and I have the CBT 24’s.

Archaea 04-11-2019 04:31 PM

Quote:

Originally Posted by Randy Bessinger (Post 57889176)
Hi Bigus. Just to let people know, Bigus is one of my heroes from the old days in the free for all subjective vs. objective debates in ultra high end forum. Was Randyb then randybes then. Engineer to MD as I recall. Hope that is going well.



As for the Parts Express CBT arrays, I did have them for sale but local delivery only. When they didn’t sell, I decided to do a simple 5.1 system with TV in small room upstairs rather than always using the theater room and projector for all TV watching. That is where they are now as close surround speakers (since they don’t localize easily). I would still sell them but I just think with their size, shipping would be prohibitive. When I was using them for two channel, I did use a minidsp HD with the eq file from Parts Express. My understanding is that eq assumed hard wood/tile floor rather than carpeted as I used them.


@Archaea , you finished yours?


Not yet

I too plan to use mine in the living room whenever I finally get around to finishing them.

I have a bad habit of putting too many irons in the fire.

Randy Bessinger 04-11-2019 04:33 PM

Quote:

Originally Posted by Archaea (Post 57889230)
Not yet

I too plan to use mine in the living room whenever I finally get around to finishing them.

I have a bad habit of putting too many irons in the fire.

Maybe, but your results are usually superb.

Bigus 04-11-2019 04:48 PM

I wonder how negative carpet would be as a hard groundplane reflection is part of the design? Could always forgo pad and use a thinner carpet at least in the front of the room I guess.

Leaning towards buying a pair of CBT36 to play with. Haven't pulled the trigger yet. If I really like them maybe buy more or build some with upgraded drivers.

Randy... yeah, finally recovering from the road to MD! I did recognize your name when mentioned. Dream home is finally starting construction (well, still just pushing dirt around) giving me the room to finally fill with all my wild ideas.

BassThatHz 04-11-2019 07:05 PM

Well, all the same speakers would be nice-to-have, but not if it is at the expense of a massive drop in SQ.

Depending on how loud you like your movies, the beds may really have to be SOLID, especially the front 3...

When I only had 3 B&W 803's, I was stressing the 3 7" woofers in the center almost to the breaking point, even though that speaker is ported to 28hz and rated for 350W. Hence why I build the center that I did (with matching L/R's).

Even though my SEOS's and mid-woofers are all the same drivers, bought all at the same time, there are still massive tonality differences between the 4 surrounds and the LCR; that's because the surrounds are using passive 2-way crossovers and the LCR's are active 4-ways (but the same drivers).

I also noticed that the tonality still varies even with the speaker settings are identical in every possible way and EQ'ed, that is because of slight differences in room acoustics, even though my walls are heavily treated at 50% coverage with an average depth of 4inches of absorption. Much much closer to an ideal-match though.

I'd imagine the only way that is going-away is if the room was circular and treated and lacking all furniture (or NOTHING more than seating at least) with all speakers at the same distance.
But circular and cylindrical rooms tend to (do) have HORRIBLE acoustics, so I'm not sure how well that would "actually" work out in reality...

Now that I actually have enough DSP horse-power, I suppose I could go active surrounds, but it's hardly worth the cost IMO.

The more I think about it, the more I think that a matrix plug in the back of our heads is the best way to go in order to trick all 5 senses with 100% precision, but until then, I guess 128 channels of Atmos is the "best we got..."

There are a lot of good sounding speakers but if you want great sounding or flawless, then things get MUCH harder and more expensive (and generally: bigger and heavier too...)

For male vocals you really need to be solid to 70hz at a minimum.
I've noticed vocal improvements even EQ'ing flat to single digits sealed, so sky's the limit.

Mid-bass subs are pretty much REQUIRED imo, without them drums and explosions just AREN'T the same,
hell even guitar rifts and pianos and a number of other related things.
Just like you wouldn't play pipe organ music or earthquakes or door slams and dinosaur stomps without dedicated ULF subs.

From a pure technical perspective, if you aren't flat from 1hz to 22.1khz (i.e. CD quality), then technically it is not TRUE hi-fi now is it? High fidelity STARTS with being able to play all frequencies, with authority and cleanly, and so pretty much ALL systems are a compromise to some-degree.
The question then becomes: when is good-enough good enough.
Some call it quits at 16khz and 15hz, others 20khz and 10hz etc.

The facts and truth is: Speakers and recordings will NEVER sound the same as the original live-sound that was supposed to be captured. For several obvious reasons: take a piano for example. That is a body that is large and radiates sound in all directions with mostly equal-power. That's not something a tweeter can really do, especially a domed or horned tweeter. So from the get-go you are already compromised. Furthermore, when we listen to such live-sound we are often moving our heads from side to side, even subconsciously, a static microphone isn't going to capture that, not even binaural microphones or other DSP trickery. Also most tweeters and mids (and even woofers and subs) lack sufficient dynamics to capture an aggressive piano hammering. Often times it clipped the mic and is thus clipped in the recording, or the recording is too soft or too muffled or was mic'ed too nearfield or too farfield. (There is almost no "good distance" to record at, only differences.)

It's hard to trick the human ear, we are designed to detect the slightest differences in level or direction or tonality or harmonic texture / resonances and distortions.

For these reasons and others, Humans can easily detect a real human singing from a played back recording, even on the world's best headphones or speakers. It is an exorcise in futility, but that never stopped us from trying regardless. hehe! :p

Sometimes you just have to kick back and have a beer, or 24... because, that's all that can be done about it. ;)

Bigus 04-11-2019 09:21 PM

Linkwitz does a good job of discussing the complexities and limitations in the recording and reproduction chain and offers some useful thoughts on how to best capture and/or recreate a sense of real instruments and people. That and/or is a good starting point for example. Is the goal to reproduce with extreme precision what the mic heard, or "do whatever necessary" to the signal and soundfield to best emulate what it probably sounded like to a human present at the time of recording?

Relevant to this thread and my search is that I am convinced power response is an utterly critical part of the answer. Toole has been saying this forever. And Linkwitz. And Geddes. And Keele. And so on.

Different ways to try and get there for sure. I started down one path and to overcome the compromise of SPL ability is going to take some true conviction of wallet and clock. For a largish room where HT will be a large use of the system, perhaps it makes more sense to look at paths where SPL is a strength and then work on their inherent compromises?

Horns and arrays are the logical choices. The CBT is very intriguing. I'm a little concerned about a 1kHz xo though with that 3/4" Dayton tweeter used. Probably necessary for horizontal response. Better drivers are available but man designing a CBT from scratch looks more daunting than a 5 way dipole!

OJ Bartley 04-12-2019 10:03 AM

1 Attachment(s)
Quote:

Originally Posted by trilkb (Post 57883424)
My dream is qsc 2150 clones, or titan 615, or JBL screen array. I'd use volt 10s for surrounds and then do 18 JBL 12s in a baffle wall with the mains.

I'll second the 2150s. I honestly was blown away by them and haven't heard a speaker play as effortlessly as those at the volumes we had before. Well, maybe the KEF Muons I heard one year at a show, but that was a long time ago. And they're slightly more expensive.

I've been curious about some of the really big JBLs like the Everest, but those are also cost prohibitive! If I were to cash in that winning lottery ticket today and hire a designer for my next theatre, I would start out by specifying 2150s in a baffle wall up front. And likely some horn subs supplemented by a few sealed 18s or 24s to dig down to single digits.


EDIT: I was just reminded in another thread of a different improvement I'd plan for... Tirnnov processing. It is more expensive to implement but I haven't read any negative reviews yet. I'd love to have that in my "dream" setup.

Bigus 04-13-2019 08:01 AM

I think I'll build a pair of CBT to play with. After more reading they seem to have most of the positives I like about dipole while avoiding most of the negatives. May need a larger driver than the CBT36 though to integrate well with mains and supply enough midbass for a theater. Or perhaps augmented by a midbass module at arc centerpoint. I will see.

Bigus 04-14-2019 04:20 PM

Well I ordered drivers, 128 of them in all. Something tells me this cabinet design and construction is going to take a long time. Will have to play with Legendre vs chebyshev shading. Time to get to work with soundeasy.

Bigus 05-15-2019 07:31 PM

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Yeah, this is going to take some time. Will get to work on them over the next week or so, hopefully can make some headway.

BassThatHz 05-16-2019 08:37 AM

1 Attachment(s)
Quote:

Originally Posted by Bigus (Post 57902034)
Well I ordered drivers, 128 of them in all.

How many speakers does that make? I hope at least the LCR's...

CBT's sounds like a lot of work. Wiring, EQ, routing curved wood...

If you are going to all this work, what about beveled edges?
https://www.avsforum.com/forum/attac...mentid=2567482

Bigus 05-16-2019 11:10 AM

That will make the LR pair. 16 midwoofer and 48 tweeter per side.

It is a lot of work. I haven't dabbled in line arrays much... for good reason! My previous path wouldn't have needed all the router work, but I'd have spent forever laying up and finishing all the panels in composite. And building a lot more amp channels. So a give and take I guess.

I do plan to chamfer edges but will have to experiment on the curved face to see how that goes.


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