Cabinet ressonance on JBL LSR 305

[Exprymer]

Hello, guys, I've been hearing the ~240hz ressonance on this LSR305 MK1 cabinet for years now and today i found the culprit.

Turns out it's not the cabinet, but the plastic holder around the speaker that vibrates.

Method of testing:
I pick up an oscilator from the DAW and swept the frequency until the cabinet started emitting high frequency content because of the plastic holder. When i put my fingers on the plastic the noise would go away.

Simple solution:
Take the correct tool for the screws and instead of tighten them, loosen them a little bit until the ressonance goes away. The noise is entirely correlated to how tighten or loose the screws are.
Difficult solution: Maybe i will design another holder or put some neoprene stuff behind the original holder to mitigate completely the vibration.

This problem has been going around since the first years of production as the link below suggests and i don't know if the MK2 still has the same problem. Still i Hope this little fix can solve it for you too.

See ya!


https://gearspace.com/board/so-much-gear-so-little-time/912092-jbl-cabinet-resonance-anyone.html

 

[ernestcarl]

Hello, guys, I've been hearing the ~240hz ressonance on this LSR305 MK1 cabinet for years now and today i found the culprit.

Turns out it's not the cabinet, but the plastic holder around the speaker that vibrates.

Method of testing:
I pick up an oscilator from the DAW and swept the frequency until the cabinet started emitting high frequency content because of the plastic holder. When i put my fingers on the plastic the noise would go away.

Simple solution:
Take the correct tool for the screws and instead of tighten them, loosen them a little bit until the ressonance goes away. The noise is entirely correlated to how tighten or loose the screws are.
Difficult solution: Maybe i will design another holder or put some neoprene stuff behind the original holder to mitigate completely the vibration.

This problem has been going around since the first years of production as the link below suggests and i don't know if the MK2 still has the same problem. Still i Hope this little fix can solve it for you too.

See ya!


https://gearspace.com/board/so-much-gear-so-little-time/912092-jbl-cabinet-resonance-anyone.html

For some reason, mine's right around 210 and 220 Hz -- been a long time since but I used a non-drying viscous acoustic sealant to completely fill in the trimming area -- but now loosened the screws per your suggestion just a tad bit for some "extra" good measure.

*I would suggest making sure the screws in the back are not loose, though -- mine were, and found them audibly vibrating.

 

[Exprymer]

For some reason, mine's right around 210 and 220 Hz -- been a long time since but I used a non-drying viscous acoustic sealant to completely fill in the trimming area -- but now loosened the screws per your suggestion just a tad bit for some "extra" good measure.

*I would suggest making sure the screws in the back are not loose, though -- mine were, and found them audibly vibrating.

Yeah man, the Back Screws should be tightened indeed. Try to play a song that you know that causes these types of noises or even a oscillator, and with the sinewave going on try to loose the screws a little bit, but put your finger on the plastic parts around the driver first to make sure it's from there. The Noise goes away.

 

[ernestcarl]

Yeah man, the Back Screws should be tightened indeed. Try to play a song that you know that causes these types of noises or even a oscillator, and with the sinewave going on try to loose the screws a little bit, but put your finger on the plastic parts around the driver first to make sure it's from there. The Noise goes away.

Yep, I just use REW's noise generator. But, also, that cheap cone driver certainly is nowhere near perfect, and has its limits. I find that it just distorts more (esp. the at higher SPLs) than speakers I have currently (or speakers listened to in the past).

 

[Slayer]

Hello, guys, I've been hearing the ~240hz ressonance on this LSR305 MK1 cabinet for years now and today i found the culprit.

Turns out it's not the cabinet, but the plastic holder around the speaker that vibrates.

Method of testing:
I pick up an oscilator from the DAW and swept the frequency until the cabinet started emitting high frequency content because of the plastic holder. When i put my fingers on the plastic the noise would go away.

Simple solution:
Take the correct tool for the screws and instead of tighten them, loosen them a little bit until the ressonance goes away. The noise is entirely correlated to how tighten or loose the screws are.
Difficult solution: Maybe i will design another holder or put some neoprene stuff behind the original holder to mitigate completely the vibration.

This problem has been going around since the first years of production as the link below suggests and i don't know if the MK2 still has the same problem. Still i Hope this little fix can solve it for you too.

See ya!


https://gearspace.com/board/so-much-gear-so-little-time/912092-jbl-cabinet-resonance-anyone.html

I would think the best long term solution would be to simply remove the plastic housing, tape off where needed and use a spray can of rubber coating. Dry and reassemble. This technic is often used on plastic waveguides and works out quite well.