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post #1 of 515 Old 06-02-2015, 10:33 AM - Thread Starter
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DIY Dolby ATMOS module

I am thinking of adding Dolby ATMOS enabled modules to my HT (4 Pi L/C/R's and custom Eminence Beta 10 CX surrounds/back). Due to low ceiling (slightly less than 8') and lack of interest in adding ceiling speakers (will be moving w/in a few years and don't really want to go to all the effort, due to WAF on ceiling is not an option); plus the Dolby white paper and designers such as Dennis E have indicated that for these conditions the ceiling-reflection approach is preferred.

Looking at all the commercial offerings (KEF, Atlantic Technolgies, Onkyo, and ELAC US) I see no real technological "magic sauce" in the actual module, rather it seems the bulk of the work is accomplished by the Dolby processor (in my case a Marantz AV7702). Coaxial seems a fairly common factor. Bass extension below 150 Hz is not desired due to the nature of larger waves.

Seems to be little interest on AVS for a DIY project, @BIGmouthinDC 's thread really went no where. I get the desire to build speakers and put them on/in the ceiling...but it is not the best approach for my space.

I "think" the angle of the enclosure is going to be critical. Would be interesting to see if the angle is common across manufactures.
[edit: Dolby patent has a range, Pioneer settled on 20 degrees and I assume the ELAC will be the same as it's the same designer)

I think a 5-6" coaxial driver would be the logical starting point. The Volt 6's are attractive as they are Eminence drivers that fairly match my surrounds. Eminence doesn't seem to offer the 6" driver direct to the consumer. Madison Speaker offers a Seas 7" coaxial w/crossover for around $200/ea. For power would probably buy another 4-channel Adcom amp off eBay.

Anyone here done a DIY project and not posted the results? I have searched the site and the interweb but have failed to find any build threads.

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post #2 of 515 Old 06-02-2015, 11:39 AM
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We can do a group buy on the 6.5" coaxials if you wanted to and I can send you a couple to mess around with in the meantime until Eminence was done making them. They can be used in really small sealed boxes and still work for Atmos.
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post #3 of 515 Old 06-02-2015, 01:34 PM - Thread Starter
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Quote:
Originally Posted by Erich H View Post
We can do a group buy on the 6.5" coaxials if you wanted to and I can send you a couple to mess around with in the meantime until Eminence was done making them. They can be used in really small sealed boxes and still work for Atmos.
Erich, thanks. I know you have probably played with more coaxial/concentric drivers than just about anyone on AVS. Just looking at the commercial products it doesn't seem that difficult.

I am laid up with post-surgery healing so can't really do much in the near term. What seems a good approach is for me to start with a small rectangular plywood enclosure, just deep enough so the driver fits (probably double front baffle to recess the driver). I have not modeled the 6" drivers T/S parameters in winISD but I saw you posted them on your forum. I assume it will be a pretty small enclosure to get an -3 dB point of 120-150 Hz.

Using a laser pointer (or geometry ) I can then determine the exact amount of angle from front speaker ---> ceiling ---> listening position. Won't be as pretty as an angled enclosure, but for a test box should be good. Can deal with pretty once (if) the concept is viable.

Seems a good project. I would assume some of the DIYSoundgroup customers would want a Dolby enabled speaker vice ceiling mounted.

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post #4 of 515 Old 06-02-2015, 02:11 PM
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Quote:
Originally Posted by NWCgrad View Post
Looking at all the commercial offerings (KEF, Atlantic Technolgies, Onkyo, and ELAC US) I see no real technological "magic sauce" in the actual module, rather it seems the bulk of the work is accomplished by the Dolby processor (in my case a Marantz AV7702).
Other 'way round. Dolby Elevation processing (HRTF notch) is built into the speaker. Your Marantz pre-pro doesn't have to do anything, unless you use Audyssey, in which case the same notch will be inserted into the Audyssey target curve (to keep it from equalizing the notch away).

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post #5 of 515 Old 06-02-2015, 03:29 PM - Thread Starter
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Originally Posted by sdurani View Post
Other 'way round. Dolby Elevation processing (HRTF notch) is built into the speaker. Your Marantz pre-pro doesn't have to do anything, unless you use Audyssey, in which case the same notch will be inserted into the Audyssey target curve (to keep it from equalizing the notch away).
Thanks Sanjay...

Read up on the issue and it seems there is some controversy on the need for the HRTF notch. An article (http://www.audioholics.com/loudspeak...nd-dolby-atmos) interviewed Dr Floyd Toole on the topic. Seems the enabled at best will be a compromise, not sure why some of the HT designers indicate it is the best option....I guess that the joy of new technologies. But as on-ceiling speakers are not a viable option right now I don't really have anything to lose except some time and effort. Drivers can be repurposed into on ceiling versions later if necessary.

Bottom Line from the article:
Quote:
Since this is a rather complex topic of discussion, I thought it would be useful to recap the main points herein as follows:

--- Head Related Transfer Function (HRTF) was first documented in 1972. Its incorporation into a Dolby elevation speaker is not a unique application.
--- HRTF varies among individuals and are not predicable but can be generalized.
--- If you want a sound to come from a discrete location, its most effective to put a speaker in that location rather than bouncing soundwaves off a ceiling.
--- HRTF encoded into speakers is redundant and may degrade the sound quality. Timbre matching speakers is important especially when directional and distance cues are involved. Choosing speakers of similar quality and dynamic capabilities for all of your home theater speakers is recommended.
--- The listening window for a reflected speaker varies significantly within the room and careful aiming is required to generate the proper effect. Sounds with insufficient high frequencies will be localized at the origin speaker locations producing those sounds.
--- A controlled dispersion speaker can create the illusion of elevated sound for a narrow listening area.

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post #6 of 515 Old 06-02-2015, 03:42 PM
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Quote:
Originally Posted by NWCgrad View Post
Read up on the issue and it seems there is some controversy on the need for the HRTF notch.
That site has been on an anti-Dolby campaign (especially regarding the Atmos-enabled speakers) since last February, so I would take everything they say with a large grain of salt.
Quote:
Seems the enabled at best will be a compromise, not sure why some of the HT designers indicate it is the best option.
Some HT designers indicate it as the best option because they've probably tried it and found it to work better than ceiling mounted speakers for their particular rooms. In other situations, it could end up being a compromise. Even then, having a compromised (non-optimal) impression of sounds above you is better than no impression of sound above you. Let's not make perfect the enemy of good.

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post #7 of 515 Old 06-02-2015, 03:49 PM
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If my hearing tests mean anything
and for the most part I can't hear over about 6.5K, (thanks, REW)
is the notch an issue?

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post #8 of 515 Old 06-02-2015, 04:02 PM
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Quote:
Originally Posted by asarose247 View Post
If my hearing tests mean anything
and for the most part I can't hear over about 6.5K, (thanks, REW)
is the notch an issue?
The notch is at 10kHz, which means its effect (giving the impression of sounds above you) is out of your hearing range.

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post #9 of 515 Old 06-02-2015, 04:16 PM - Thread Starter
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Info is spotty, but seems at least some of the required processing is in the AVR due to steep gain and notch which is most consistent in the digital domain. However, it seems some of the elevation modules have at least some in the XO.

As Dr Toole worked next to the guy that developed the transform function and understands it as well as probably anyone on eart, and thinks it's probably unessessary makes me go hmmmm.

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post #10 of 515 Old 06-02-2015, 04:44 PM
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Quote:
Originally Posted by NWCgrad View Post
I am laid up with post-surgery healing so can't really do much in the near term. What seems a good approach is for me to start with a small rectangular plywood enclosure, just deep enough so the driver fits (probably double front baffle to recess the driver). I have not modeled the 6" drivers T/S parameters in winISD but I saw you posted them on your forum. I assume it will be a pretty small enclosure to get an -3 dB point of 120-150 Hz.
There is a sealed Atmos box coming that's 7.5" wide, 9" tall, and 6" deep with 3/4" material. I think MTG90 said it will get down around 120hz or so in that sized enclosure.

Dimensions could go smaller if the box was made from 1/2" material, but it might need a brace which would be hard to squeeze in there behind the compression driver. Maybe it wouldn't if it was Baltic birch, I'm not really sure.


If there's a certain compression driver you want to use I'll get it and see how deep the enclosure needs to be, then send you a prototype to work with when you get out of the hospital.


If you have any other funky ideas like four small 3" woofers surrounding a dome tweeter, or something like that, I can make up a very shallow prototype just to see how it goes.

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post #11 of 515 Old 06-02-2015, 04:44 PM
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I don't see how a head shape TF is necessary either. I've mostly stayed out of the atmos thing, but I don't see how the reflection method can work without high directivity, which seems to be a key point of Toole's in that summary you posted.

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post #12 of 515 Old 06-02-2015, 09:16 PM
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NWCgrad, I was just experimenting this evening and found a way to make the 6.5" coaxial with a small compression driver have a mounting depth of less than 3.5"! I'll try to get some photos showing how we can do it. It's kind of neat.
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post #13 of 515 Old 06-02-2015, 11:55 PM
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That's quite a feat Erich! I think a lot of guys would welcome those who aren't for cutting holes in the ceiling. 3.5" is nothing.
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post #14 of 515 Old 06-03-2015, 08:29 AM - Thread Starter
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Quote:
Originally Posted by Erich H View Post
There is a sealed Atmos box coming that's 7.5" wide, 9" tall, and 6" deep with 3/4" material. I think MTG90 said it will get down around 120hz or so in that sized enclosure.

Dimensions could go smaller if the box was made from 1/2" material, but it might need a brace which would be hard to squeeze in there behind the compression driver. Maybe it wouldn't if it was Baltic birch, I'm not really sure.


If there's a certain compression driver you want to use I'll get it and see how deep the enclosure needs to be, then send you a prototype to work with when you get out of the hospital.


If you have any other funky ideas like four small 3" woofers surrounding a dome tweeter, or something like that, I can make up a very shallow prototype just to see how it goes.

Would probably want to go with a neo based CD for space considerations, definitely NOT the 6 lb, 2.5" thick Eminence PSD2013 I used for my surrounds

Quote:
Originally Posted by Erich H View Post
NWCgrad, I was just experimenting this evening and found a way to make the 6.5" coaxial with a small compression driver have a mounting depth of less than 3.5"! I'll try to get some photos showing how we can do it. It's kind of neat.

Wow, that is thin...I think that would be a winner right there! I wonder how it would model in the sealed Atmos box you are working (with depth shaved to just fit the driver). I bet 1/2" Baltic Birch would not require bracing for this application.


If we can get it down to 4 - 5" I bet a lot of people would be interested for on-ceiling application. I may be tempted to build a truss system using 80/20 aluminum (I love that stuff, its very light and strong - pretty inexpensive off the eBay store if you do not need custom sizes) and ceiling mount if the ceiling reflection experiments fail. The more I read the less effective it seems to be except at higher frequencies (around 7 kHz and up depending on end-users ears).

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post #15 of 515 Old 06-03-2015, 10:05 AM
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You got my attention fellas. Shallow depth surrounds that would mount flush inwall with 2x4" depth or onwall at 4-5" deep cab size would be fantastic. I don't think you could keep those in stock.
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post #16 of 515 Old 06-03-2015, 01:05 PM
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had an ad for this pop up on me http://legacyaudio.com/images/upload...6_2015_opt.pdf
didn't bother to check the price . . .

but I think coolrda is on to something

a slim design with the "right" dispersion/response/aiming could easily become mountable ATMOS/DTS tops

that's my SLX bracket construct using modified security camera mounts
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What ceiling material do you have ? That would matter in a reflection situation.
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post #18 of 515 Old 06-04-2015, 11:33 AM
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I've been thinking back to my very first speaker project in the late 70s it was a clone of the Bose 901

I don't have any pictures but here is a Google image



what if we took the available $19 replacement drivers from Parts Express put them in a flat "pancake" shaped box maybe a series of ports around the perimeter and covered it with fabric?

kind of this shape covered with fabric:



The drivers are less than 1 ohm and you would put all 9 in series. they are rated 83-15,000 hz

should put out a very diffuse sound when mounted on the ceiling.
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post #19 of 515 Old 06-04-2015, 12:16 PM
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maybe not flat but on the section of an arc based on , from the hip, a circle or sphere of 2 ft. (or bigger?) radius for slightly enhanced dispersion
but not the 30, 45+ degrees seen in dipoles, as monopole seems to be the order of the day for "tops", hence the "slightly"
like the opposite , mol, of a synergy horn
somebody capable of using cadcam or the like might find a range of that slight curvature, even just starting with the illustration provided
there was much debate about the 90 degree total dispersion issue for overheads in another thread, the design competition


a question from me provably unqualified to even ask , but anyway
would there be comb filtering/interference issues with just being flat? and there are probably others, I know nothing . . .
I have to think back to questions/discussions/answers about line arrays , some here , some at BF, his short line arrays, and other sites
for me its like the words are "dots" I've heard - but connecting the "dots" coherently, not me . . .


oh yeah, that's why I like AVS
hope those folks speak up as to why or why not


thanks

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Quote:
Originally Posted by asarose247 View Post
had an ad for this pop up on me http://legacyaudio.com/images/upload...6_2015_opt.pdf
didn't bother to check the price . . .

but I think coolrda is on to something

a slim design with the "right" dispersion/response/aiming could easily become mountable ATMOS/DTS tops

that's my SLX bracket construct using modified security camera mounts
That Legacy looks to be pretty good speaker, I shudder at the cost. When I was in college I lusted after Legacy ( and VMPS) speakers.

The SLX bracket looks similar to what I am thinking. The extruded aluminum has an inner chamber where I could run the wires so they are not seen. 8020 is like tinker toys/Lego's for adults.

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What ceiling material do you have ? That would matter in a reflection situation.
I have a heavy textured ceiling (not popcorn). I think it would scatter the reflection to at least some degree.

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post #21 of 515 Old 06-04-2015, 02:39 PM
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A Erich H:
any pics of the 6.5 co-ax/CD combo mentioned in post #12 ?

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post #22 of 515 Old 06-04-2015, 02:53 PM
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@ NWCgrad

my wires for the 4 tops come thru the ceiling wrt to placment on the tresatle sysytem and channel in the unistrut for minimum visibility

now back to module constructs

that's trestle system,

FFE

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post #23 of 515 Old 06-04-2015, 02:54 PM
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Quote:
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maybe not flat
just did a little digging, we could get 1/4 inch thick replacement skylight covers in something around 20 inches square for under $50.



could apply some damped mass to the inside to kill any panel resonances.
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post #25 of 515 Old 06-04-2015, 03:12 PM
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^
thanks for the push
there is something about the steep angulation and depth that gives me pause
but you did make me curious
so how about this: Lithonia Lighting Model # DFMLSL14 M4 Internet # 205507200

14 in. Replacement Lens for LED Low Profile Square Flush Mount

14" square, flatter and shallower

this is a re-paste, it may work as a link

http://www.homedepot.com/p/Lithonia-...4-M4/205507200

this unit be a base for attachment of the small slightly angulated speaker array directly to this plastic lens,, if done carefully
a box for this could easily be fabbed for ceiling attachment and then there's "wiring", something else I don't know
but, do go on

still waiting for what erich H may add wrt post #12

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Lithonia Lighting 11 in. Replacement Lens for LED Low Profile Square Flush Mount
Model # DFMLSL11 M4

also in 11" sq.

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post #27 of 515 Old 06-04-2015, 03:26 PM
 
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Speakers actually have a more narrow dispersion when two woofers are placed side by side or top and bottom than a single woofer would have.

Also- for the reflection surface you would not want to use anything curved like a convex or concave - It would either diffuse the sound or focus it narrow. Neither is good.

A flat surface that reflects like a mirror would work. IN fact a mirror might work nice to set it up too- moving it until you can see the Atmos anabled module from the listening position would help get placement right.
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post #28 of 515 Old 06-04-2015, 03:31 PM
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Quote:
Originally Posted by asarose247 View Post
A Erich H:
any pics of the 6.5 co-ax/CD combo mentioned in post #12 ?
I will try to get some photos uploaded tonight.

If there is a group buy for those 6.5" coaxials, I can help or someone else can take delivery of the coaxials and compression drivers and ship them out. I wouldn't mind either way.

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post #29 of 515 Old 06-04-2015, 03:53 PM
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trying to be creatively on topic
not sure (duh!) about upward modules (at all)(never considered it)
but for surface tops
and this is (obviously) impromptu

A truncated version of the Fusion 4 Quad4 :limited to only 2 4" drivers and the 4" EOS waveguide and CD
designed for ported and an xo of 80 or 100
probably still 5.75 hi but maybe not as deep and certainly not 28" long
for comparison, the Klipsch SLX i have for my tops are 5.75 hi and 25" long and about 5-6 deep
but I'm willling to bet that the 2x4's of the quad 4 already kick butt
and i have no basis to know but
I can't believe that the standard (?) Klipsch1" tweeter in that 3" conical "horn/waveguide" remotely compares very well to the output of the 4" EOS /CD combo
Ta-da! easily mountable/aimable/properly guided dispersion

ok
slight pause
vented, this from PE
Vented cabinet: Type: Bass reflex; Size (internal) including volume displaced by driver and port: 0.12 ft³; Internal cabinet dimensions (golden ratio): 9-1/2"H x 5-7/8"W x 3-5/8"D; Port dimensions (with flared exit): 1" dia. x 6"L. Typical results: 3 dB down-point (f3): 73 Hz; Tuning frequency (fb): 69 Hz; Low frequency limit at rated power without exceeding conventional Xmax (i.e. (voice coil length – gap height) / 2)): 55 Hz.

ok so may an xo of 100hz
still 5.75 hi maybe 20" long and depth TBD wrt to needed volume per above tuning, rear vents?

This is techinically WAY beyond little ol' me wrt development/evaluation/feasibility

Once I'm recovered from recent eye surgery to resume the usual crimes against nature and mankind, I'll be taking more naps

Back to you

DIY FAN Denon X4400 , ATI A 2000 for 7.4.6 SCATMOS Sammy 82" 4K/HDR
L/R: Fusion 15 V2 , C: 88 Special , SL/SR: 88 Special(V2) , RL/RR: F-3, TF/TR: Volt 6's TM: SLX, FH: F4Q4
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post #30 of 515 Old 06-04-2015, 03:58 PM
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From Erich H:
I will try to get some photos uploaded tonight.

you have my "lazy man's" full attention

DIY FAN Denon X4400 , ATI A 2000 for 7.4.6 SCATMOS Sammy 82" 4K/HDR
L/R: Fusion 15 V2 , C: 88 Special , SL/SR: 88 Special(V2) , RL/RR: F-3, TF/TR: Volt 6's TM: SLX, FH: F4Q4
SUBMAXIMUS V2, ,Submaximus V3,LOWARHORNCustom Dual Driver VBSS,2 x 6000DSP
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