JBL Cinema Owners - Support Group Thread

[73hadd]

Me: "I bought speakers from an actual movie theater!"
People: "You need help."
Me: "Yes! Thankfully the people on ASR are very helpful."
People: "No, I mean, seek professional help."
Me: "Yes! Many of the people on ASR are professionals!"
People: (back away slowly and leave)

The components are:

2446H https://jblpro.com/en/product_documents/2446-pdf
2380 Horn 90x40 https://jblpro.com/en-US/site_elements/2380a-data-sheet
4648A-8 (Pair of 2226 15") https://jblpro.com/en/site_elements/4648a-information


They're similar to a 4670 in that the top end is a 4670D-HF, but the bottom is 4648A-8 instead of the 4638TH.

No crossovers included.

I bought three of them for LCR in a home theater. The dream would be to have M2, maybe someday.

Here is the goal:

-Not a passive crossover
-Not use my Behringer CX3400 active crossover although I may for temporary setup/testing
-A DSP setup for crossover and eq, that could be used on M2
-Not spend a lot of money on sidegrades (sideways "upgrades.") Preferably only spend money on tech that could be applied to an evental M2 setup.

I am looking for suggestions, example signal chains that might work here. Possibilites:

-Crown amps
-BSS
-JBL Intonato
-Other?

Some other questions:

-I have heard that there can be cancellation issues with the dual 15s so close together (pwns 2.5) Why does this work in a theater but not at home? Is it due to:
--listening distance? (explain to me the math that means you have to be x feet away for the two drivers to behave as one)
--elevation in a theater? they are normally mounted high, mid screen
--Theater uses a "baffle wall" that extends with width of the screen

-I missed out on the 2360 horn. For a 15'x25' room, would there have been any advantages to the 2360 horn over the 2380 horn?


Possible "Upgrades" (although I should rather save for M2, but maybe I can't resist):

Beryllium for the JBL 2446H - https://materion.com/-/media/files/...f?la=en&hash=D29E0232801A737AB38B983CFD5023D6

BMS Driver - BMS 4590 http://www.bmsspeakers.com/fileadmi...s_4590_2011-04_coaxial_compression_driver.pdf

Other projects:


@mitchco has done amazing things to DSP large JBL
@pwnz is working on an interesting 2.5way
@DubbyMcDubs has a very inspiring theater here
https://www.audiosciencereview.com/forum/index.php?threads/jbl-m2-questions.13263/post-659759
@Andysu A serious setup with the electronics too!

List of JBL Cinema model numbers:

8330A - A surround speaker. https://jblpro.com/en/products/8330a
8330 - Surround Speaker https://usermanual.wiki/JBL/8330.948437242 (thanks @Andysu )
4722N - Includes Crossover

I will want to keep this first post updated with lessons learned along the way. I also want to post some component/part numbers for various JBL Cinema setups so it's easy to see what parts apply where.

Thanks in advance!

 

[DubbyMcDubs]

Thanks for the mention! If you have any questions please let me know.

My 4722's are the N version which have passive crossovers. Originally I was going to use Crown amps with the active crossovers but opted out of that. I didn't want the complexity and the hiss reported from other users with similar setups.

They JBL Intonato looks very nice to me.

 

[hardisj]

I use the 2446j/2380 and 2035HPL combo for my HT L/C/R. I actually purchased them from a closed down Cinemark theater a while back.
I built 4 cuft enclosures vented to around 50-something Hz for the 15's.

I run mine active using the built-in DSP of my Crown XLS DriveCore amps. XLS2002 across the fronts. If I had a higher budget, I wouldn't run those amps and would opt for something better wrt noise floor. The SNR of the Crowns is too high with the 2446j as they are incredibly sensitive (as you know). So, that's my word of warning. Alternatively, you can pad them down with a passive crossover. I live with it because I don't want to spend the time building passives, I don't want to buy an amp with a much better SNR, and I dig owning the same speakers I grew up listening to in the theater in town. Nostalgia, if you will. I also don't spend enough time to in my HT to justify the above.

 

[73hadd]

Thanks for the mention! If you have any questions please let me know.

My 4722's are the N version which have passive crossovers. Originally I was going to use Crown amps with the active crossovers but opted out of that. I didn't want the complexity and the hiss reported from other users with similar setups.

They JBL Intonato looks very nice to me.

Nice! Yes, if I already had crossovers like you do, I would use them, one less thing to worry about, complexity indeed! I do have a question about your screen, what got me is that picture of it lit from behind, very cool! Will any acoustically transparent screen work the same way if lit from behind? (Because I want to do that.) I noticed in the actual movie theater that they put a black fabric all over the wall behind the screen. I am guessing it was for light and sound absorption, which is not an issue in HT as there are enough lumens from the front.

 

[73hadd]

I use the 2446j/2380 and 2035HPL combo for my HT L/C/R. I actually purchased them from a closed down Cinemark theater a while back.
I built 4 cuft enclosures vented to around 50-something Hz for the 15's.

I run mine active using the built-in DSP of my Crown XLS DriveCore amps. XLS2002 across the fronts. If I had a higher budget, I wouldn't run those amps and would opt for something better wrt noise floor. The SNR of the Crowns is too high with the 2446j as they are incredibly sensitive (as you know). So, that's my word of warning. Alternatively, you can pad them down with a passive crossover. I live with it because I don't want to spend the time building passives, I don't want to buy an amp with a much better SNR, and I dig owning the same speakers I grew up listening to in the theater in town. Nostalgia, if you will. I also don't spend enough time to in my HT to justify the above.

Thanks! For the 2446j to 2035HPL, are xover at 500hz or what did you like best?

Yes, theater nostalgia is what got me here a bit too. Thanks for the tip on the amps. For the Crown I-tech I saw this spec:
Signal to Noise Ratio ≥ 108dB THD (full rated power, 20 Hz - 20 kHz) 0.35%
Does anyone know if the THD is lower at less than full rated power?

At this point I am leaning towards BSS or Intonato and using separate amps. Or I could ignore the future M2 idea completely and get something cheap/reasonable that will do the DSP for less $$$, not sure what devices would be better measurement wise than the Harman stuff.

 

[hardisj]

I'm somewhere between 500-600Hz, IIRC on the crossover. Mating to the 15-inch doesn't permit much wiggle room in the crossover so the compression drivers have to be crossed pretty low.

FWIW, I have my speakers installed behind an acoustically transparent screen and the front "wall" is a bare frame of 2x4's with 2-inch acoustic foam covering the entire thing to minimize comb filtering from the screen back to the speakers.

 

[DubbyMcDubs]

Nice! Yes, if I already had crossovers like you do, I would use them, one less thing to worry about, complexity indeed! I do have a question about your screen, what got me is that picture of it lit from behind, very cool! Will any acoustically transparent screen work the same way if lit from behind? (Because I want to do that.) I noticed in the actual movie theater that they put a black fabric all over the wall behind the screen. I am guessing it was for light and sound absorption, which is not an issue in HT as there are enough lumens from the front.

Yes, any AT screen should create that effect however some may be better than others because of the weave/perforations. I used LIFX strips and can change it to any colour (shown below). The screen I choose is a Seymour AV Center Stage XD, without the black backing material they offer. It is incredible.

My baffle wall is a stud wall with three layers of 13mm CSR soundcheck plasterboard, then on the face of that wall is 100mm of black CSR Martini polyestester acoustic insulation. The martini is used to absorb energy reflected off the back if the screen, but it does contribute to the overall absorption of the room which should be factored into your acoustic design. The whole wall is black, with no reflective items. The walls of the cavity in the baffle wall are also covered with acoustic polyester insulation.

I have a document I threw together to summarise all the things I thought were important when building the room. I will find it later and send it to you. It has some details about baffle walls that I gathered from various sources over the web. Info on baffle walls is fragmented and there are a lot of opinions.

If you want to see what I think is the best HT on the planet, which also uses JBL, check out these links:

https://keithyates.com/portfolio/hahn-theater/

https://www.avsforum.com/threads/rob-hahn-theater-build.2523385/

Here are some photos of my room under construction and a few once I started using the room. The decorative panels to go around the screen are not done yet.

 

[AnalogSteph]

If I had a higher budget, I wouldn't run those amps and would opt for something better wrt noise floor. The SNR of the Crowns is too high with the 2446j as they are incredibly sensitive (as you know). So, that's my word of warning. Alternatively, you can pad them down with a passive crossover. I live with it because I don't want to spend the time building passives, I don't want to buy an amp with a much better SNR, and I dig owning the same speakers I grew up listening to in the theater in town.

Surely making some L-pads with ballparked resistor values for the 2446Js wouldn't count as an undue amount of effort...?

 

[73hadd]

@DubbyMcDubs .... Wow.... Really nice

 

[73hadd]

I'm somewhere between 500-600Hz, IIRC on the crossover. Mating to the 15-inch doesn't permit much wiggle room in the crossover so the compression drivers have to be crossed pretty low.

FWIW, I have my speakers installed behind an acoustically transparent screen and the front "wall" is a bare frame of 2x4's with 2-inch acoustic foam covering the entire thing to minimize comb filtering from the screen back to the speakers.

Sounds like a really nice build! Have you been tempted to measure these with your new gear? Perhaps the horn and bass bin separately?

 

[Andysu]

There is presently a bargain on ebay usa, JBL cinema professional closed down cinema $3.7k
Quint - "For that you get the head, the tail, the whole damn thing.
x4 QSC amplifiers - x6 JBL 4648 - x6 JBL 2360A - x2 JBL 4645C - x12 JBL 8330 mkI and rack tower with a SRS matrix decoder? I say that is a mega deal sure 3.7k but most JBL k2 is gonna only be two lousy speakers at $30 daylight $k robbery and the parts with cinema JBL will be light-years better for that JBL cinema flashback.

with the x6 JBL 4648 and 2446 CD 2360A horns you can make a five screen matrix and store the extra in the garage wrapped up. Use the x12 surrounds for common atmos placement of 6 overhead and the rest for x2 per side and two for rear. The subs one middle front the other middle back or side by side at the middle front below the JBL 4648 bass cab centre channel. The QSC amps maybe power the surrounds x4 not really enough for a five screen matrix for the bass LF and HF horn, need five matching amps for that. Maybe use the QSC for subs? get some affordable cheap ex used Crown or new Behringer NX3000D for each five-screen matrix channel and for the surrounds? I would recommend Crown CTs8200 as x8 amps would be enough to power the sidewall and rear back with a second 2nd Crown CTs8200 for the overhead surrounds.

 

[Alice of Old Vincennes]

Yes, any AT screen should create that effect however some may be better than others because of the weave/perforations. I used LIFX strips and can change it to any colour (shown below). The screen I choose is a Seymour AV Center Stage XD, without the black backing material they offer. It is incredible.

My baffle wall is a stud wall with three layers of 13mm CSR soundcheck plasterboard, then on the face of that wall is 100mm of black CSR Martini polyestester acoustic insulation. The martini is used to absorb energy reflected off the back if the screen, but it does contribute to the overall absorption of the room which should be factored into your acoustic design. The whole wall is black, with no reflective items. The walls of the cavity in the baffle wall are also covered with acoustic polyester insulation.

I have a document I threw together to summarise all the things I thought were important when building the room. I will find it later and send it to you. It has some details about baffle walls that I gathered from various sources over the web. Info on baffle walls is fragmented and there are a lot of opinions.

If you want to see what I think is the best HT on the planet, which also uses JBL, check out these links:

https://keithyates.com/portfolio/hahn-theater/

https://www.avsforum.com/threads/rob-hahn-theater-build.2523385/

Here are some photos of my room under construction and a few once I started using the room. The decorative panels to go around the screen are not done yet.

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Wowww

 

[73hadd]

Surely making some L-pads with ballparked resistor values for the 2446Js wouldn't count as an undue amount of effort...?

Good idea. Where should I start? I have the 2446H (8 ohm). Trying the Behringer CX3400 I found out that I am using the entire range of level adjustment, just to compensate for the 11db efficiency difference from the 2446H to the 4648A-8. Using the lpad should help with this, and I believe there is similar passive device on the JBL M2, but I am not sure if it is adjustable? It seems I should be aiming for a 500hz crossover point if that is helpful. I am happy to order the parts and assemble but I lack the design experience. Thanks!

 

[mightycicadalord]

I used a stack of the old dual 15" and horn as a bass cabinet once, it was sick