DIY JBL 4645 Sub project - AVS Forum
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post #1 of 47 Old 01-03-2013, 11:48 AM - Thread Starter
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So Where I work we have 4 of these used in a large theater, I fell in love with them, so I spent the better part of the day dissecting one and getting all of the measurements from it.



Built mine based on the JBL 4645 THX certified Movie theater sub.

" 800 Watts Continuous Pink Noise, 1600 Watts Continuous Program Power Handling
Usable response to 22 Hz (-10 dB, no EQ), flat to 22 Hz (-3 dB) with External EQ
2242H SVGTM Super Vented Gap Cooled Driver- High Sensitivity- Minimal Power Compression- Highest Maximum-SPL Capability- Extremely Low 2nd and 3rd- Harmonic Distortion- Symmetrical Field Geometry SFGTM- Magnet Structure- Extended Excursion Capability
Approved by Lucasfilm, Ltd. for THX installations

Specifications:

TRANSDUCER: JBL Model 2242H 460 mm (18 in) Low Frequency Transducer
SYSTEM:
Rated Impedance: 8 ohms
Minimum Impedance: 7.2 ohms
POWER HANDLING CAPABILITY:Continuous Pink Noise: 800 wattsContinuous Program: 1600 wattsPeak Power: 3200 watts
OUTPUT CAPABILITY:
Axial Sensitivity:50 Hz to 500 Hz; 99 dB, 1W @ 1m40 Hz to 100 Hz; 97 dB, 1W @ 1m
Power Compression:At -10 dB power (80 W): 0.6 dBAt -3 dB power (400 W): 2.0 dBAt rated power (800 W): 3.3 dB
"


So one entire sheet of MDF later and a few days I have this,



~10 Cu ft. box tuned to 30Hz single 18" JBL pro sub weighs in at 131lbs.

At 1,200 Watts program thing rocks the house!

Hard to capture scale in the pic, but it is the size of my fridge minis a few feet in height.

Here is an older pic of my sound rack ( Yes I still rock the tape player )



The lower JBL UREI Amps are the ES600 model, I have one bridged running the single 18'

I used a slightly different driver, I went with the 2241h JBL Driver.



Long story short, I corner loaded it and I am in love! feeling the room shake was a surprise for the low end response of that driver rolls off around 25Hz with a EQ i was able to boost it slightly. but I feel the low end is more than enough.


Just thought I would share, I will be painting mine soon and may even put the JBL logo's on the side... and may even build another in the future...
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post #2 of 47 Old 01-03-2013, 11:57 AM
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Looks cool! A lot of people really like those jbl setups, the are time tested and proven performers.
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post #3 of 47 Old 01-03-2013, 07:18 PM
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congratulations.

should you decide to pump movie content through the sub, be sure to plop a high pass filter on there.

Listen. It's All Good.
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post #4 of 47 Old 01-04-2013, 09:15 AM - Thread Starter
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Originally Posted by LTD02 View Post

congratulations.
should you decide to pump movie content through the sub, be sure to plop a high pass filter on there.

I have it on its own EQ and active crossover, I also have (2) 15" Mid-bass cabinets mounted behind the screen smile.gif

I like movies as well biggrin.gif
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post #5 of 47 Old 01-04-2013, 09:16 AM - Thread Starter
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I did make some changes to the cabinet while building it, I flared both ends of each port, with a nice round edge, as well as shifted the ports up away from the driver some more, I also rounded the edges of all internal bracing.
Did it help? Honestly can not tell.
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post #6 of 47 Old 01-05-2013, 05:47 AM
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I am just curios as to why you would want one of these for theater if they only go down to 25hz to 30hz? Do you like them mostly for the mid-bass output? Are you using anything else for the ultra low frequencies?
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post #7 of 47 Old 01-05-2013, 08:18 PM
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Looking good , we are just finishing up a 12.4 cu version tuned to 23hz.
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post #8 of 47 Old 01-07-2013, 11:19 PM
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lol. 25-30hz is not midbass...
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post #9 of 47 Old 01-08-2013, 12:31 PM - Thread Starter
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"Usable response to 22 Hz (-10 dB, no EQ), flat to 22 Hz (-3 dB) with External EQ"

22Hz is low enough for what I need it for smile.gif

with a slight EQ boost I was able to get a bit more low end. I will get the spectrum analyzer on the room soon to see.
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post #10 of 47 Old 01-25-2013, 05:44 PM - Thread Starter
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Update,

Took some time and EQ'd all 10 channels today in the theater,



I used a DBx RTA-M Mic

I have some strange harmonics in the room and odd shaped hard surfaces. But I feel this is pretty good for my use.

Was able to get the Sub about as flat as I can given the EQ I have and the restraints on the driver.

What are everyone's thoughts? Ways I can improve the above room response?
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post #11 of 47 Old 01-25-2013, 06:10 PM - Thread Starter
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So my next goal is the 'tilt' the response like below,



To give it a more 'warm' sound with a slight bass 'bump'

But I needed a flat clean slate to build from first.
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post #12 of 47 Old 10-19-2013, 06:50 PM
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How have you been enjoying your sub? Any new things to report?

JBL Pro Cinema
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post #13 of 47 Old 01-12-2014, 12:11 PM
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Quote:
Originally Posted by DJDAudio View Post

So Where I work we have 4 of these used in a large theater, I fell in love with them, so I spent the better part of the day dissecting one and getting all of the measurements from it.



Built mine based on the JBL 4645 THX certified Movie theater sub.

" 800 Watts Continuous Pink Noise, 1600 Watts Continuous Program Power Handling
Usable response to 22 Hz (-10 dB, no EQ), flat to 22 Hz (-3 dB) with External EQ
2242H SVGTM Super Vented Gap Cooled Driver- High Sensitivity- Minimal Power Compression- Highest Maximum-SPL Capability- Extremely Low 2nd and 3rd- Harmonic Distortion- Symmetrical Field Geometry SFGTM- Magnet Structure- Extended Excursion Capability
Approved by Lucasfilm, Ltd. for THX installations

Specifications:

TRANSDUCER: JBL Model 2242H 460 mm (18 in) Low Frequency Transducer
SYSTEM:
Rated Impedance: 8 ohms
Minimum Impedance: 7.2 ohms
POWER HANDLING CAPABILITY:Continuous Pink Noise: 800 wattsContinuous Program: 1600 wattsPeak Power: 3200 watts
OUTPUT CAPABILITY:
Axial Sensitivity:50 Hz to 500 Hz; 99 dB, 1W @ 1m40 Hz to 100 Hz; 97 dB, 1W @ 1m
Power Compression:At -10 dB power (80 W): 0.6 dBAt -3 dB power (400 W): 2.0 dBAt rated power (800 W): 3.3 dB
"


So one entire sheet of MDF later and a few days I have this,



~10 Cu ft. box tuned to 30Hz single 18" JBL pro sub weighs in at 131lbs.

At 1,200 Watts program thing rocks the house!

Hard to capture scale in the pic, but it is the size of my fridge minis a few feet in height.

Here is an older pic of my sound rack ( Yes I still rock the tape player )



The lower JBL UREI Amps are the ES600 model, I have one bridged running the single 18'

I used a slightly different driver, I went with the 2241h JBL Driver.



Long story short, I corner loaded it and I am in love! feeling the room shake was a surprise for the low end response of that driver rolls off around 25Hz with a EQ i was able to boost it slightly. but I feel the low end is more than enough.


Just thought I would share, I will be painting mine soon and may even put the JBL logo's on the side... and may even build another in the future...

Looks nice! Bet paint will really make you feel proud. Curious why you chose the 2241 over the 2242?

Have a Happy and safe New Year!!!
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post #14 of 47 Old 01-12-2014, 07:12 PM
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I am also curious as to why you went with the 2241 over the 2242? Are they close enough in performance that you can substitute one for the other? I know that the 2242's are hella expensive! Is the 2241 cheaper?
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post #15 of 47 Old 03-14-2014, 04:59 AM
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HI DJDAudio.
I do admire your built. The sub looks like exact clone of the jbl pro sub.
I am thinking to do same but cant get the drawings of the sub. I would like to ask you if can give me a copy of your plans that I can cut the mdf perfectly.
I am thinking to use JBL 2242h.
Thanks for help and good luck
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post #16 of 47 Old 03-14-2014, 06:12 AM
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You can figure it out from the specs.

http://www.jblpro.com/pub/cinema/4645c.pdf

Good luck!
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post #17 of 47 Old 03-14-2014, 11:10 AM
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Quote:
Originally Posted by Martycool007 View Post

I am also curious as to why you went with the 2241 over the 2242? Are they close enough in performance that you can substitute one for the other? I know that the 2242's are hella expensive! Is the 2241 cheaper?

Here's a link that outlines how the drivers were designed for specific applications from a guy that works at JBL: http://www.livesoundint.com/lab/lab/messages/archive2/36039.html

Physically they are identical as far as bolt pattern and cutout.

I was one of first guys here running the big JBL Pro Cinema gear. I run JBL Cinema speakers at all 7.1 ch's. For subs I run a pair of JBL 4645b's plus a JBL 4642a. I actually swapped the oe 2241's out of the 4642 for a set of 2242's. I run my hpf at about 18hz and they sound great. As to the sound difference i noticed after the swap...i pretty much agree with the guy at JBL in the link above when he says the 42's have a nicer upper end and the extra xmax helps with the low stuff.

The JBL gear is actually quite a bargain if you can find it preowned like I did. I'm lucky in that i have a dealer of USED pro cinema gear(JBL, EV, etc) about an hour away in Memphis. Also the drivers can be bought on ebay preowned at decent prices.

-Ken
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post #18 of 47 Old 03-14-2014, 04:14 PM
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Can anyone give me drawings of this subwoofer please. I understand the dimensions can be obtained on jbl website but I want to know what is inside the box etc. I would like to make a great clone of the real thing for a bit less as in Europe they charge around 1500 euro. Thank you guys
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post #19 of 47 Old 03-14-2014, 04:44 PM
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About all that is inside the box is some fiberglass lining the walls and probably a single 2x4 (actually closer to 1.5" x 3.5") brace between the front and and rear baffle. I've never looked in one so I am basing this assumption on my similar JBL 4647A cabinet. A little extra bracing would be a good thing. I would say are on your own for picking a port...whatever you like. Nothing magical about 1x 8" or 3x 4" or whatever.
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post #20 of 47 Old 03-14-2014, 06:22 PM
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Thanks for the advice mobeer4don. I'll try to follow this steps and see how it goes.
I'm going to use jbl 2242 driver for this cabinet.
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post #21 of 47 Old 03-15-2014, 07:16 AM
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Quote:
Originally Posted by KenWH View Post

Here's a link that outlines how the drivers were designed for specific applications from a guy that works at JBL: http://www.livesoundint.com/lab/lab/messages/archive2/36039.html

Physically they are identical as far as bolt pattern and cutout.

I was one of first guys here running the big JBL Pro Cinema gear. I run JBL Cinema speakers at all 7.1 ch's. For subs I run a pair of JBL 4645b's plus a JBL 4642a. I actually swapped the oe 2241's out of the 4642 for a set of 2242's. I run my hpf at about 18hz and they sound great. As to the sound difference i noticed after the swap...i pretty much agree with the guy at JBL in the link above when he says the 42's have a nicer upper end and the extra xmax helps with the low stuff.

The JBL gear is actually quite a bargain if you can find it preowned like I did. I'm lucky in that i have a dealer of USED pro cinema gear(JBL, EV, etc) about an hour away in Memphis. Also the drivers can be bought on ebay preowned at decent prices.

-Ken

I read the link you posted with regards to the differences between the 2241 versus the 2242, but, I believe that the JBL guy was commenting on the differences in a more pro-type sound situation, and although I am now aware that the 2242 has a better top end and a better low end, I am still interested in knowing what real-world, actual differences in sound quality you observed between the two?

In other words.....can you elaborate a little more on the perceived differences in sound quality that you observed between the 2241 versus the 2242? Thanks!
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post #22 of 47 Old 03-15-2014, 08:25 AM
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Quote:
Originally Posted by Martycool007 View Post

In other words.....can you elaborate a little more on the perceived differences in sound quality that you observed between the 2241 versus the 2242? Thanks!

I had actually bought the two 2242h's off of ebay as back up drivers for my 4645b's. I got to thinking why not swap them into the 4642a cabinet and keep the 2241 woofers as spares. I didn't notice a night and day difference and didn't really expect to since the cabinet and amp were the same. Also the 4642a cabinet is designed for the 2241's so it's probably not getting the most out of the 42's. Even still, dropping in the 2242's I noticed a bit more detailed upper bass and I think the 42's do the low freq's a little better than the 41's. By better i mean more forceful "thump" and ability to discern subtle note changes in a constant bass line. The 42's just somehow feel like there's a bit more muscle and substance behind the sound.

I've said it for years but i still feel that from 20hz and up the big JBL sub systems are hard to beat in terms of sound quality and dynamics.

For years JBL has been using the 2242h's in their higher end Synthesis home audio system also. They basically use a retuned and dressed up 4645 in the Synthesis systems. It's called the S1S: http://www.jblsynthesis.com/downloads/products/prod_110_634485073314299583_S1S-EX%20ts.pdf

For anyone interested in JBL drivers and sub/speaker systems head over to http://www.audioheritage.org/vbulletin/ and have a look around. These guys/gals eat, sleep, & breath all things JBL and there's some serious knowledge in that forum.

They helped me design my wall mounted diy rear surrounds which each use a single JBL 2225 15" woofer and 2445 compression driver.
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post #23 of 47 Old 03-15-2014, 09:02 AM
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NIce. I want to see some pics of your HT room, Ken. I have thought a couple times about doing surrounds like you have but I think my room is just too small for something like that... maybe. biggrin.gif

Check out the new system I just built in my sig pic.


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post #24 of 47 Old 03-16-2014, 09:33 AM
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Here's a few pics Scott...


Front Stage consisting of JBL 4675 mains and a semi custom 4670 center:

For size scale...the screen is a 133" DaLite HP


4670 side surround and the dual 4645b's. Woofers for my next project chilling out on the floor next to them.smile.gif






4642a sub loaded with the 2242's


Diy surrounds using the same 15" 2225 woofer and 2445 comp driver the other JBL's use:



Some may not like the flat paint and exposed drivers but I actually like and embrace the stripped down industrial look of the JBL's. They look like they mean business and they do. wink.gif


-Ken
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post #25 of 47 Old 03-16-2014, 01:03 PM
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That looks awesome. I do actually like the almost deconstructed look of your surrounds. Beautiful
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post #26 of 47 Old 03-16-2014, 03:53 PM
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It is the the 5749 that was designed for 2x2242's. I found mine locally for $450 in great shape.
http://www.jblproservice.com/pdf/Theatre%20Series/5749.pdf

I use it up front behind the screen in conjunction with a DTS-10 (from 13 to 50 hz). The side walls are flanked by a 2245 and an AETD-18H, both in their own ported 8 cu. ft. cabs.

Incredible bass is what really makes the experience! And no need for fake feeling bass shakers (been there).
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post #27 of 47 Old 03-16-2014, 06:02 PM
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"Thanks for the advice mobeer4don. I'll try to follow this steps and see how it goes.
I'm going to use jbl 2242 driver for this cabinet."

nichol97 built something tuned a little lower:

http://www.avsforum.com/t/1363719/jbl-2242h-build-thread/0_50

Listen. It's All Good.
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post #28 of 47 Old 03-16-2014, 06:13 PM
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i've mentioned it before, but that is one heck of a theater.

for some reason, i kept going back to the picture of the screen because it looks like your screen is glowing...then i see it is a retroreflective hp, so it is! any issues with it at that large size and material type?

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post #29 of 47 Old 03-17-2014, 04:26 AM
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KenWH, wow! That is a pretty sweet looking all JBL setup! Very impressive looking! What horns do those huge JBL-4675's use, and also what CD? Those horns look massive! Also, I see where you said that the surrounds use the 2225 woofer, and a 2445 CD, but, I am also curious as to which horn is used in your surrounds?

Just out of curiosity, have you ever considered upgrading the diaphragms in your 4675's to Be diaphragms? I bet that would be a really nice step up in the sound quality department! (I am assuming your 4675's are 2-way, but, if I am wrong & they do in fact utilize a super-tweeter, can you post up the model of the tweeter CD & the horn used for it?)
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post #30 of 47 Old 03-17-2014, 08:44 AM
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Quote:
Originally Posted by Martycool007 View Post

KenWH, wow! That is a pretty sweet looking all JBL setup! Very impressive looking! What horns do those huge JBL-4675's use, and also what CD? Those horns look massive! Also, I see where you said that the surrounds use the 2225 woofer, and a 2445 CD, but, I am also curious as to which horn is used in your surrounds?

Just out of curiosity, have you ever considered upgrading the diaphragms in your 4675's to Be diaphragms? I bet that would be a really nice step up in the sound quality department! (I am assuming your 4675's are 2-way, but, if I am wrong & they do in fact utilize a super-tweeter, can you post up the model of the tweeter CD & the horn used for it?)

Thanks Marty,

All woofers are 2225's, cd's are 2445's. Crossover from the woofers to the cd's happens at 500hz.

Mains use the 2360 lens which are 90*x 40*. Center uses 2385 lens which are 60*x 40*, the surrounds all use 2380 lens which are 90* x 40*. I'd like to swap the the rear surrounds to the 2382 lens which are 120* x 40*. All of my JBL's are 2-ways oe but i changed them all to 3-ways by adding Selenium ST350 super tweeters which are passive crossed around 10khz. Even though JBL says the big cd's are good to 20khz... I added the ST350s just to add a bit of sparkle as the big cd's response falls off above 10khz. They sound better than trying to boost the cd's high end with an eq.

I've not really thought much about switching to the Beryllium diaphragms due to cost...installing 7 Be diaphragms gets pricey quick. Plus, i'm really happy with the sound as they are now...the mids and upper mids are so effortlessly clean with beyond lifelike dynamics it's just nuts really. Movies are great but a good surround SACD or DVD-A disc with all these bad boys firing hi rez tunes at you is truly an assault on the senses. smile.gif
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