dasdoing
Major Contributor
that shows you did excellent
actually side-fills rely on the Haas effect. the delayed sound wont sound like reflections, but the direct sound will dominate the localization
-
WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!
JBL CBT 70J-1 Review (Constant Beam Transducer)
- Thread starter amirm
- Start date
that shows you did excellent
actually side-fills rely on the Haas effect. the delayed sound wont sound like reflections, but the direct sound will dominate the localization
I'm considering the CBT 70J-1 as surrounds (side) in a living room 7.2.4 system. If anyone with practical experience with these in a home environment has feedback, that would be welcome. I can post at AVS Forum as well if that is more appropriate.
Our front speakers are conventional (KEF Reference 3 Meta & 2 Meta). The room has architectural limitations impacting surround placement. Will the CBT 70J-1, mounted high on a side wall, seem like they are elevated with respect to the LCR? Will the radiation pattern of the array make them hard enough to localize that they work well when combined with the shorter standard design front speakers?
I haven't made a detailed room drawing yet, but here are some basics.
We have some flexibility on height of the surrounds, they can be anywhere from 74 1/2" to 88" to from the floor to the top of the speaker (which is 27 1/2" tall). This puts the bottom of the speaker 47" to 60.5" from the floor. I'd be mounting them with the MTC-CBT-FM1 low profile bracket, so these locations allow for 5" ceiling clearance to slide the speaker into the mount. The bracket provides 0 degrees of tilt & I could probably add a little tilt with the use of spacers at the speaker to bracket interface.
My reasons for considering the CBT:
I'm hoping these goals might be met based on what I've read (including the system design by @Archaea). This is not a dedicated theater room, but we've had enjoyable living room surround for years, understanding that there are some compromises inherent to our space. Multichannel music, both native and upmixed, and video content are equally important.
Our front speakers are conventional (KEF Reference 3 Meta & 2 Meta). The room has architectural limitations impacting surround placement. Will the CBT 70J-1, mounted high on a side wall, seem like they are elevated with respect to the LCR? Will the radiation pattern of the array make them hard enough to localize that they work well when combined with the shorter standard design front speakers?
I haven't made a detailed room drawing yet, but here are some basics.
- MLP to front L & R distance is about 10 feet.
- The KEFs are a little short with the UniQ at 34" from the ground for LR. I'll get the center as high as I can, but will be below a conventional TV (not projector).
- The main listening area is a standard 3 seat sofa which is approximately 7 1/2 feet wide.
- The room width has some asymmetry so the seating area and speakers are confined to a 16'7" wide area. The right surround will therefore be 8' 3 1/2" from the MLP and the L surround is slightly further at 9' 7".
We have some flexibility on height of the surrounds, they can be anywhere from 74 1/2" to 88" to from the floor to the top of the speaker (which is 27 1/2" tall). This puts the bottom of the speaker 47" to 60.5" from the floor. I'd be mounting them with the MTC-CBT-FM1 low profile bracket, so these locations allow for 5" ceiling clearance to slide the speaker into the mount. The bracket provides 0 degrees of tilt & I could probably add a little tilt with the use of spacers at the speaker to bracket interface.
My reasons for considering the CBT:
- Surface mounting (wall has mechanicals precluding the use of in-wall).
- Possible option for elevated speaker mounting with reduced perception of elevated source as compared to conventional speakers (this is really what I'm asking about).
- More even sound level across the width of the sofa to reduce speaker localization from leftmost and rightmost seats (I reserve MLP
).
I'm hoping these goals might be met based on what I've read (including the system design by @Archaea). This is not a dedicated theater room, but we've had enjoyable living room surround for years, understanding that there are some compromises inherent to our space. Multichannel music, both native and upmixed, and video content are equally important.
Last edited:
I have used the 50LA-1 as a front wide speaker. For that purpose it worked very well. Speaker just disappears. Wondered what they would sound like with stereo/subs and was suprised that it sounded quite good crossed with subs at around 100hz FWIW
Archaea
Active Member
I posted this on my CBT 70J-1 thread at AVSforum, and post it here too for those that might benefit.
This is a fix to address the 70j-1 resonance that @amirm found in his review.
Pro Audio often uses plastic cabinets. It's cheap, it's light, it can be molded into complex designs that would be far more expensive if made of wood. The negative side is that since it's light, it can be prone to resonances.
I've had these CBT 70j-1 for about 5 years now, and over that time I occasionally have heard a resonance in the CBT 70j-1 plastic cabinet. Whenever I heard something odd, a buzzing or a resonance, I put the track I heard it on in a "Fix" playlist in my Apple Music playlist. There's a half-dozen songs in that list where I can reproduce a resonance on demand with these 70j-1s. On the whole, the resonance issue is so infrequently encountered that I always backburnered the project of trying to solve it. I noticed in testing when I've heard that sound if I went to the speaker and applied compression pressure to the cabinet, the resonance would stop. So I was thinking I either needed to take apart all the cabinets, and layer them inside with dynomat to increase the mass of the cabinet, or alternatively, I was thinking I could drill a hole in the speaker width wise, and use some threaded rod to span the width of the speaker and then a use a washer and nut on each side to tighten until needed -- those were my two leading ideas, but I hadn't gotten around to trying either. Good enough is the enemy of perfect.
Most recently when I heard it on a new song, I started pushing on the tweeter array in way of quick troubleshooting, and realized that it seemed to be originating from the tweeter array vibration against the cabinet. When I pressed on the array from the front of the speaker, the resonance stopped. So I took off the tweeter array, there are 10 screws, and between the tweeter array and the cabinet I installed some P6 Nitrile washers on each screw mount. (5.8mm ID x 1.9MM). This keeps the tweeter array plastic from its plastic on plastic contact against the main cabinet, and I'm happy to report on all my test tracks the buzzing resonance is now gone -- entirely (at least to reference volumes which is where I limit my system to protect my ears. I did not try louder). I replayed all 7 tracks on my list and not one of them had the resonance now, and they all had the resonance before. SOOOO I wanted to share this, in case others have encountered this resonance issue and were plotting a path forward.
You can buy these nitrile washers for next to nothing on Amazon. 3 cents each. It's a cheap fix, and probably worth it for peace of mind. Some of my 70J-1 are brand new out of the box and they have shown the resonance issue, so if you haven't encountered it, then good, but keep this in mind in case you do.
Here is the track list where I've catalogued the resonance issue in my HT listening.
Here are some of the washers that are similar sized to the ones I used that should be able to resolve the problem. $6 shipped for 200 washers. That's enough to fix 20 CBT 70j-1 speakers. (10 rubber or nitrile washers per speaker)
Just a single washer between these contact points (shown in red circle in the picture below)
Let me know from those of you who try this, if it resolves your resonance issue.
NOTE:
You'll have to remove your grill to do this. To remove the grill simply pop off the press fit JBL logo on the front of the speaker grill and there are two eyeglass type Philips head screws holding the grill in place, and once those two screws are removed, it's just press fit with a rubber gasket around the perimeter. Fair warning: it is not easy to put the grill back in. These things are meant to be water resistant for outside commercial use in the rain and dust, so that rubber seal is tight and putting the grill back on is a challenge. It can be done, I've done it several times, but it isn't a walk in the park. It's TIGHT.
So maybe do one, see if you think the effort is worth it. In the end, you may find you like your steel grills off better. Like I do.
At which point you can install some cool AMC Prime inspired RGB 5050 lights! mmmmmmmm
https://hardforum.com/threads/rgb-5...ater-speakers-to-look-like-amc-prime.1967358/
hehe......see how this project could escalate?
This is a fix to address the 70j-1 resonance that @amirm found in his review.
Pro Audio often uses plastic cabinets. It's cheap, it's light, it can be molded into complex designs that would be far more expensive if made of wood. The negative side is that since it's light, it can be prone to resonances.
I've had these CBT 70j-1 for about 5 years now, and over that time I occasionally have heard a resonance in the CBT 70j-1 plastic cabinet. Whenever I heard something odd, a buzzing or a resonance, I put the track I heard it on in a "Fix" playlist in my Apple Music playlist. There's a half-dozen songs in that list where I can reproduce a resonance on demand with these 70j-1s. On the whole, the resonance issue is so infrequently encountered that I always backburnered the project of trying to solve it. I noticed in testing when I've heard that sound if I went to the speaker and applied compression pressure to the cabinet, the resonance would stop. So I was thinking I either needed to take apart all the cabinets, and layer them inside with dynomat to increase the mass of the cabinet, or alternatively, I was thinking I could drill a hole in the speaker width wise, and use some threaded rod to span the width of the speaker and then a use a washer and nut on each side to tighten until needed -- those were my two leading ideas, but I hadn't gotten around to trying either. Good enough is the enemy of perfect.
Most recently when I heard it on a new song, I started pushing on the tweeter array in way of quick troubleshooting, and realized that it seemed to be originating from the tweeter array vibration against the cabinet. When I pressed on the array from the front of the speaker, the resonance stopped. So I took off the tweeter array, there are 10 screws, and between the tweeter array and the cabinet I installed some P6 Nitrile washers on each screw mount. (5.8mm ID x 1.9MM). This keeps the tweeter array plastic from its plastic on plastic contact against the main cabinet, and I'm happy to report on all my test tracks the buzzing resonance is now gone -- entirely (at least to reference volumes which is where I limit my system to protect my ears. I did not try louder). I replayed all 7 tracks on my list and not one of them had the resonance now, and they all had the resonance before. SOOOO I wanted to share this, in case others have encountered this resonance issue and were plotting a path forward.
You can buy these nitrile washers for next to nothing on Amazon. 3 cents each. It's a cheap fix, and probably worth it for peace of mind. Some of my 70J-1 are brand new out of the box and they have shown the resonance issue, so if you haven't encountered it, then good, but keep this in mind in case you do.
Here is the track list where I've catalogued the resonance issue in my HT listening.
Here are some of the washers that are similar sized to the ones I used that should be able to resolve the problem. $6 shipped for 200 washers. That's enough to fix 20 CBT 70j-1 speakers. (10 rubber or nitrile washers per speaker)
Just a single washer between these contact points (shown in red circle in the picture below)
Let me know from those of you who try this, if it resolves your resonance issue.
NOTE:
You'll have to remove your grill to do this. To remove the grill simply pop off the press fit JBL logo on the front of the speaker grill and there are two eyeglass type Philips head screws holding the grill in place, and once those two screws are removed, it's just press fit with a rubber gasket around the perimeter. Fair warning: it is not easy to put the grill back in. These things are meant to be water resistant for outside commercial use in the rain and dust, so that rubber seal is tight and putting the grill back on is a challenge. It can be done, I've done it several times, but it isn't a walk in the park. It's TIGHT.
So maybe do one, see if you think the effort is worth it. In the end, you may find you like your steel grills off better. Like I do.
At which point you can install some cool AMC Prime inspired RGB 5050 lights! mmmmmmmm
https://hardforum.com/threads/rgb-5...ater-speakers-to-look-like-amc-prime.1967358/
hehe......see how this project could escalate?
That’s awesome. I wonder if the CBT 1000 has the same mounting resonance issue and fix.I posted this on my CBT 70J-1 thread at AVSforum, and post it here too for those that might benefit.
This is a fix to address the 70j-1 resonance that @amirm found in his review.
Pro Audio often uses plastic cabinets. It's cheap, it's light, it can be molded into complex designs that would be far more expensive if made of wood. The negative side is that since it's light, it can be prone to resonances.
I've had these CBT 70j-1 for about 5 years now, and over that time I occasionally have heard a resonance in the CBT 70j-1 plastic cabinet. Whenever I heard something odd, a buzzing or a resonance, I put the track I heard it on in a "Fix" playlist in my Apple Music playlist. There's a half-dozen songs in that list where I can reproduce a resonance on demand with these 70j-1s. On the whole, the resonance issue is so infrequently encountered that I always backburnered the project of trying to solve it. I noticed in testing when I've heard that sound if I went to the speaker and applied compression pressure to the cabinet, the resonance would stop. So I was thinking I either needed to take apart all the cabinets, and layer them inside with dynomat to increase the mass of the cabinet, or alternatively, I was thinking I could drill a hole in the speaker width wise, and use some threaded rod to span the width of the speaker and then a use a washer and nut on each side to tighten until needed -- those were my two leading ideas, but I hadn't gotten around to trying either. Good enough is the enemy of perfect.
Most recently when I heard it on a new song, I started pushing on the tweeter array in way of quick troubleshooting, and realized that it seemed to be originating from the tweeter array vibration against the cabinet. When I pressed on the array from the front of the speaker, the resonance stopped. So I took off the tweeter array, there are 10 screws, and between the tweeter array and the cabinet I installed some P6 Nitrile washers on each screw mount. (5.8mm ID x 1.9MM). This keeps the tweeter array plastic from its plastic on plastic contact against the main cabinet, and I'm happy to report on all my test tracks the buzzing resonance is now gone -- entirely (at least to reference volumes which is where I limit my system to protect my ears. I did not try louder). I replayed all 7 tracks on my list and not one of them had the resonance now, and they all had the resonance before. SOOOO I wanted to share this, in case others have encountered this resonance issue and were plotting a path forward.
You can buy these nitrile washers for next to nothing on Amazon. 3 cents each. It's a cheap fix, and probably worth it for peace of mind. Some of my 70J-1 are brand new out of the box and they have shown the resonance issue, so if you haven't encountered it, then good, but keep this in mind in case you do.
Here is the track list where I've catalogued the resonance issue in my HT listening.
Here are some of the washers that are similar sized to the ones I used that should be able to resolve the problem. $6 shipped for 200 washers. That's enough to fix 20 CBT 70j-1 speakers. (10 rubber or nitrile washers per speaker)
Just a single washer between these contact points (shown in red circle in the picture below)
Let me know from those of you who try this, if it resolves your resonance issue.
View attachment 328187
NOTE:
You'll have to remove your grill to do this. To remove the grill simply pop off the press fit JBL logo on the front of the speaker grill and there are two eyeglass type Philips head screws holding the grill in place, and once those two screws are removed, it's just press fit with a rubber gasket around the perimeter. Fair warning: it is not easy to put the grill back in. These things are meant to be water resistant for outside commercial use in the rain and dust, so that rubber seal is tight and putting the grill back on is a challenge. It can be done, I've done it several times, but it isn't a walk in the park. It's TIGHT.
So maybe do one, see if you think the effort is worth it. In the end, you may find you like your steel grills off better. Like I do.
At which point you can install some cool AMC Prime inspired RGB 5050 lights! mmmmmmmm
https://hardforum.com/threads/rgb-5...ater-speakers-to-look-like-amc-prime.1967358/
hehe......see how this project could escalate?
Ziofrenko
Member
I had the opportunity to use them in a theater here in Italy, together with its companion to strengthen the low frequencies.
Unfortunately the DSP was set to "talk" but I went looking for the manual and found what I was looking for so I corrected the EQ from the mixer.
Then I listened to my usual songs to understand how much I could push with the show and to correct the other things I was hearing both due to the environment and the speaker.
It was a play, a tragedy, about the last days of Amy Winehouse, with the actress singing live both on backing tracks and aided by the other actors on acoustic guitars, flute and French horn.
Definitely not suitable to withstand the type of pressure that the show required in that environment but certainly more suitable than the speakers supplied by the company... but all in all they defended themselves decently and we enjoyed the evening.
EAW recently released a similar but much more advanced speaker with 6 6" woofers and 30 1" dome tweeters!
The incredible thing is that all transducers are amplified separately so as to have maximum control over the required coverage.
it will be a revolution (EAW AC6).
Unfortunately the DSP was set to "talk" but I went looking for the manual and found what I was looking for so I corrected the EQ from the mixer.
Then I listened to my usual songs to understand how much I could push with the show and to correct the other things I was hearing both due to the environment and the speaker.
It was a play, a tragedy, about the last days of Amy Winehouse, with the actress singing live both on backing tracks and aided by the other actors on acoustic guitars, flute and French horn.
Definitely not suitable to withstand the type of pressure that the show required in that environment but certainly more suitable than the speakers supplied by the company... but all in all they defended themselves decently and we enjoyed the evening.
EAW recently released a similar but much more advanced speaker with 6 6" woofers and 30 1" dome tweeters!
The incredible thing is that all transducers are amplified separately so as to have maximum control over the required coverage.
it will be a revolution (EAW AC6).
Ziofrenko
Member
to find resonance is very simple: you have to reproduce a full spectrum frequency swipe, better if is slow.
no more, no less... no music.
Similar threads
- Poll
- Poll
- Poll
