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Topic: Meyer Sound Acheron Designer vs. JBL M2

Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999

posted 02-15-2018 06:59 AM

Why not? Have you looked at the plot of the 2269 in a sealed box? With a single filter, one could pretty much choose their LF response. Sure, it will take substantial power at those low frequencies but that is something that the 2269 can do quite well and with a 3 cubic foot enclosure, it would be tiny. in fact, with the 12.5" driver depth, it almost a challenge to make the box that fits it. You, pretty much, need the face of the box be just the driver. With two of them and enough power (which I don't think will be a problem), I could have it go as low as the room would allow and given the size of the room, one couldn't hear the 18Hz, if the movies actually had it recorded. Given it is just a six sided box, I'm tempted to try it just to see how it goes.

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Marcel Birgelen
Film God

Posts: 3357
From: Maastricht, Limburg, Netherlands
Registered: Feb 2012

posted 02-16-2018 02:46 AM

We did do a quick plot with the port holes closed, although it was not really a sophisticated test. The enclosure has more headroom than the one you envision, so the results won't be exactly the same. What I remember is that there was a difference of roughly +6 dB at 20Hz between the port-holed end-result and the one with the ports closed. At 30Hz, the difference would be about 2 dB and at 40Hz it would be about the same.

Besides the increased frequency response in the LF part, one of the concerns of a sealed box we had also was the cooling of the voice coil. Although we're not using it anywhere near maximum, you're still putting quite some energy into it. With the two port holes, you at least create a limited amount of circulation.

I'm eager to hear about your results in a tight fitting sealed enclosure though. I don't consider any design final and a sealed box design could definitively save some space and increase the accuracy of the bass even more.

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999

posted 02-16-2018 06:49 AM

Since it is essentially a zero cost option (for the box, presuming I have th drivers), I'm going to give it a go.

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999

posted 08-29-2018 11:28 AM

quote: Marcel Birgelen
I'd prefer a JBL SCL-2 compared to an M2, simply because it's better suited for a baffle wall setup. The form factor of the M2 is more suited for a classical studio setup. If you're not planning a baffle wall and just want to put your speakers on a stand behind the screen, I guess the M2 is fine though.

The baffle wall for my "M2s" going in. SUB18+ also won the subwoofer selection. I'm not clustering them since I have way more sub than the room needs and will use them to augment the front row of Atmos surrounds in addition to LFE.

The M2 has REALLY impressed me. When the final version of "our" M2s were done and I was able to finally put a pair up and do some more critical listening to them. They are pretty incredible. You'll hear EVERYTHING that was put into the recording. Every detail or flaw. Listening to some CDs was an entirely new experience. I've never had speakers that imaged as well as these and all five of them have that characteristic. Until now, my L250s were the best speakers I had heard (liked them better than the later 250Ti so I never updated them) but the M2s have proven their ability to me. I've never heard a better speaker than them.

The SUB18s are just frightening. I'd need a much bigger room to really get the most out of them yet they sound awesome outside too!

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Marcel Birgelen
Film God

Posts: 3357
From: Maastricht, Limburg, Netherlands
Registered: Feb 2012

posted 09-01-2018 05:50 AM

Looks like a pretty nice buildout for a private screening room.

With so much firepower in that space, I hope you don't have picky neighbors or they're sufficiently far away. [Wink]

Just out of curiosity, how are you going to mount the five custom made M2s?

Also, have you settled on a screen yet? I guess you'll be going for a microperf screen?

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999

posted 09-01-2018 06:10 AM

If you look at the bottom of the cutouts in the baffle wall, you'll see it is a platform so the M2s will sit on that. The whole face of the baffle wall will have duct liner attached, natch.

As for screen, it is a Severtson SAT-4K (woven) with the proper black backing fabric to prevent re-reflects and be acoustically transparent.

The room is being built to be as soundproof as practical. It is in the basement so it is entirely below grade so the outer-most walls are foundation cement. All of that will or is lined with fiberglass. Any inside wall will be thick with 2x6/2x8 studs and lined with fiberglass and I'm going for asymmetrical drywall layering too. The ceiling joist bays have Rockwool (by Roxul), two layers deep to help it from transferring to the floor above. The HVAC vents that feed the room above are being replaced with insulated versions to cut down on them being a "microphone" from downstairs. Then a drop ceiling with fiberglass above that. In fact, there will be so much sound absorption that I'm going to experiment once the drywall goes up on the inside as to how much/thick fiberglass to use on the walls to get the RT-60 times desired. I'm NOT seeking an anechoic chamber. One can have too-dead a room and make hard to listen to things. The back wall will get 2" of fiberglass and then the side walls will be adjusted until the right RT-60 range is achieved and then the fabric will be applied.

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Marcel Birgelen
Film God

Posts: 3357
From: Maastricht, Limburg, Netherlands
Registered: Feb 2012

posted 09-01-2018 04:10 PM

On the picture it's hard to see how deep the platform is. Did you connect it to the baffle wall? And aren't you afraid about vibrations being transferred to the baffle wall construction that way?

Besides loads of mineral wool, we've ended up putting in a bunch of mass-loaded vinyl as sound barrier. The problem with mass-loaded vinyl is though, that it reflects sound back to quite some extend, even if you're going to put it in between two layers of drywall. In order to get the RT60 timings right we covered large parts of the walls and especially the back wall with melamine foam panels, which we itself covered with permanently flame-retardant fabric.

In order to stop the sound from traveling via the HVAC system, simply installing "sound proofed" flexible ducts wasn't enough, we installed special noise dampening couplings, which effectively did the job of entirely eliminating any audible sound coming via the HVAC system. The great thing is, it worked both ways. You don't hear the HVAC system or any noises coming via it, in the room either, or you must put your ears almost besides a vent.

Do you have sufficient height and room in the back to build a proper projector room?

I'm pretty interested in your opinion on the Severtson SAT-4K screen. We've tried a woven screen before (don't know the brand anymore, but it definitly wasn't Severtson), but the results were less than stellar. On the first row, during bright scenes, everything looked like a painting. [Wink]

What's the planned distance between the screen and the first row?

And... are you planning to install a movable masking system?

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999

posted 09-01-2018 08:17 PM

The speaker platform was actually the first part of the "wall." The rest of it was built from that and there is sufficient room behind that for servicing the speakers/wiring and such.

As for vibrations, not a chance. A) These M2s were made extra dense so they don't (or barely) vibrate to begin with...even playing painfully loud. To keep the M2 specs, one only need keep the internal volume the same...these are wider/taller (and heavier) due to the extra density. But, as if that wasn't enough, they have rubber feet to isolate vibrations from/to them. I could have put in the genine spikes but opted for rubber vibration isolators.

We'll see how well things isolate and adjust accordingly. There is a tremendous amount of potential SPL in the theatre and, after hearing the M2s, I intend to listen to music in there too. They are pretty spectacular. We'll see what comes up and from where. The realities are, while we watch a lot of movies, it isn't like it is going to be in use all of the time and if everyone in the house is watching the movie, who cares if it leaks some audio. I'll also have a night-time mode to cut back on the bass and cap the level. We're going to make a good-faith effort at sound control and see where we are.

There are two I-beams whose bottoms are 8-feet above the floor and they are 8-inches tall. The rear 1/3 of the room will be 1-foot above the front so that leaves about 7-feet to the ceiling in the rear.

Projection room? None. The projector will hang in unfinished space behind the theatre and project through the rear wall.

As for masking...of course. Why would I want to lower myself to commercial level? [Wink]

I also plan on a grand drape. The masking will likely be manual while the grand drape I hope to motorize. With both, it won't be the cost but the space for the motor.

Distance from screen to front row is about 10-feet.

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Marcel Birgelen
Film God

Posts: 3357
From: Maastricht, Limburg, Netherlands
Registered: Feb 2012

posted 09-03-2018 01:24 AM

quote: Steve Guttag
I could have put in the genine spikes but opted for rubber vibration isolators.

I prefer some good rubber pads. The higher friction will ensure your speakers remain where they are.

quote: Steve Guttag
We're going to make a good-faith effort at sound control and see where we are.

In our case, we had to consider the nearby office spaces. Also, we've taken it on as a challenge, which isn't easy, since you're looking at enormous SPLs and an extremely broad frequency range. We also have a nearby train track, which produces some interesting vibrations and noises at all kinds of frequencies.

quote: Steve Guttag
Projection room? None. The projector will hang in unfinished space behind the theatre and project through the rear wall.

So, that automatically makes the unfinished space the projection booth? [Smile]

I think it is paramount to keep the projector out of the screening room. The amount of noise and heat is otherwise difficult to get rid off.

Are you going for a full DCI system or are you settling for some non-DCI projector and playout system? I guess there are no plans to support film?

quote: Steve Guttag
I also plan on a grand drape. The masking will likely be manual while the grand drape I hope to motorize. With both, it won't be the cost but the space for the motor.

We've decided not to install a drape or curtain, simply because it would become a too tight fit with our rather bulky masking system. We've got individual motorized masking for the top and bottom, the left and right share one motor as they're always symmetrical. Our screen is roughly 2:1, it maximizes the potential of the room regarding sight-lines, but I like to move scope a bit "up", so the bottom masking extends more than the top masking.

quote: Steve Guttag
Distance from screen to front row is about 10-feet.

I'm really interested if it works out for you. I'd prefer to replace our screen with a woven screen too, but the weaves really need to be invisible, otherwise the picture will be more horrible than on a vinyl screen with visible perforations.

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999

posted 09-03-2018 10:40 AM

The system will not be DCI at all, though, at this point, I probably could put together a DCI compliant system...I'm not exactly "Belair" material. As for as sources, strictly consumer (Laserdisc, DVD and Blu-ray). The sound system will be cinema-esq. If the movie has an Atmos mix, I'll be able to decode it to its fullest. For the rest, 5.1/7.1. It is a QSYS sound processor for getting everything where it belongs and manipulating as I see fit. I even "built" a 3->5 channel "spread" decoder in QSYS. Preliminary tests were promising.

I don't know if the curtain will make it at first but that is definitely in the plans. A theatre looks so unfinished without one. Plus I don't like showing a naked screen like that. Also it will reduce HVAC born dirt when the space is not in use.

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