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How to lower the resonant frequency of a structure?
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Posted on May 12, 2022 at 21:39:29 | ||
Posts: 12605
Location: Melbourne Joined: September 2, 2000 |
I recently built myself some 'Zero Baffle' spkrs, using: * 4x SB Acoustics 'Satori' 6 1/2" mid/bass drivers * and 1x Satori tweeter. See pic: ![]()
They sound terrific but, as a result of a friend bringing over some CDs to have a listen ... I've been made aware of a problem that I would like to get fixed. I did an experiment - using my sig-gen to feed various frequencies into the mid/bass drivers. Level was set quite high - and, starting with the sub XO set to 90Hz, I slowly wound the frequency up from 80Hz to 400Hz. The steel frame resonated at 130Hz; changing the sub XO to 110Hz reduced the buzz a bit - upping the XO frequ to 130Hz decreased it a bit more ... and increasing the XO point to 150Hz removed the buzz (as 130Hz was now going into the sub). My question to the brains trust is ... what do I need to do, to lower the resonant frequency of the frame which supports the drivers? (Ideally to below 90Hz!) Now, the frame which the drivers are bolted to is as follows - made from 5mm x 13mm steel flat, bolted to a 20mm thick base, which stops them falling over. See here: ![]() (There are 2 of these 'Us' for each spkr; sorry the pic has come out so small. :-(( ) It seems to me I have 2 options: Can anyone suggest the pros & cons of each? Thanks, |
The same way you stop a tuning fork from vibrating. , posted on May 14, 2022 at 04:00:47 | |
Use viscoelastic "rubber bands" - wrap firmly around the structure in several places. Problem solved. |
RE: Thank you Geoff ..., posted on May 15, 2022 at 02:42:37 | |
Hi, it's not an isolation issue, it's a damping issue. Like a tuning fork. |
The only good vibration is a dead vibration. Nt, posted on May 18, 2022 at 15:19:08 | |
Nt |
RE: Mass load the frame, posted on May 18, 2022 at 15:54:11 | |
Posts: 12605
Location: Melbourne Joined: September 2, 2000 |
Thanks, Dave - yes, adding mass is something that occurred to me. :-)) Andy |
To lower the resonant frequency you make them longer, posted on June 18, 2022 at 12:02:37 | |
Posts: 9933
Joined: January 8, 2002 |
mass loading has already been suggested |
RE: "You also changed the compliance of the structure" ..., posted on June 21, 2022 at 05:14:35 | |
Posts: 12605
Location: Melbourne Joined: September 2, 2000 |
Yes, understood. :-) Andy |
How to dampen slender vertical structures using mass, posted on July 16, 2022 at 05:55:11 | |
Mass per se is not dampening. |
RE: Steel vs aluminum, posted on August 10, 2022 at 08:38:55 | |
Posts: 22597
Location: SoCal Joined: October 19, 2008 |
Yet.....NO Aluminum bells... Too much is never enough |
RE: Yikes!, posted on August 12, 2022 at 16:40:19 | |
I have much deeper and broader background in materials than you do. And my education too. This conversation can serve no purpose any more. Ta, ta |
Never?, posted on August 15, 2022 at 14:43:36 | |
Never is a very long time. Mr. Smarty Pants. |
How much?, posted on August 16, 2022 at 12:58:02 | |
How much do I owe you for the physiological analysis? How about ten cents? |
Porpoise, posted on August 17, 2022 at 03:50:23 | |
This conversation can have no porpoise any more. |
RE: An update! ..., posted on July 27, 2023 at 05:15:56 | |
Posts: 1465
Location: USA Joined: August 8, 2014 |
Add mass. |
RE: An update! ..., posted on July 27, 2023 at 07:29:37 | |
Isolation is the new dampening or mass loading. Didn't anyone get the memo? |