I have taken apart one of my bad 988 speakers. I am in the process of cleaning up the actual panels, getting all the old glue off etc.
One thing that surprised me is the lack of a hard connection between the two Aluminum brackets that the panels are screwed onto and the larger outside frame. The aluminum brackets are attached to the top and bottom plates with hard rubber grommets. Every other connection to the frame is via foam. I am wondering if it is a good idea to make the connection between the inner frame and the outer frame a more solid one? I will add pictures later.
One thing that surprised me is the lack of a hard connection between the two Aluminum brackets that the panels are screwed onto and the larger outside frame. The aluminum brackets are attached to the top and bottom plates with hard rubber grommets. Every other connection to the frame is via foam. I am wondering if it is a good idea to make the connection between the inner frame and the outer frame a more solid one? I will add pictures later.
The stock aluminum frame is built the same way an aluminum window frame is made.
Basically wood style pitch screws into alumium “U” channels butted together.
Anything that would excite a frame resonance would more than likely excite these joints
There was a reason Quad didn’t couple their panels to these, and hence the rubber isolation.
However they did allow an extreme movement of all the panels and the aluminum bracket to vibrate excessively near the middle area. You can feel the movement easily enough
I would change out the long braket for a thicker ‘U’ channel compressed around Sorbthane and pressed inside the channel wihout screwing
Clamp all panels together vertically with stiffer clear thicker double sided tape tape (used in glass display jewelry cases)
Use closed dense cell foam tape aganist the outer frame members.
You will have to glue a wood strip inside the vertical end frame to build up just enough room to compress some closed cell foam against the U channel that holds the panels ( there is some distance away that needs shortening up and you damp the outside frame (glued wood) and sandwich the foam againt it (panels/u channel)
Now you dont excite the cheap frame but at the same time you have stiffened all the panels vertically without a possibility of transmitting vibrations where they dont need to go.
I will wager impulse response might improve but have not tested it as of yet.
Regards
David
Basically wood style pitch screws into alumium “U” channels butted together.
Anything that would excite a frame resonance would more than likely excite these joints
There was a reason Quad didn’t couple their panels to these, and hence the rubber isolation.
However they did allow an extreme movement of all the panels and the aluminum bracket to vibrate excessively near the middle area. You can feel the movement easily enough
I would change out the long braket for a thicker ‘U’ channel compressed around Sorbthane and pressed inside the channel wihout screwing
Clamp all panels together vertically with stiffer clear thicker double sided tape tape (used in glass display jewelry cases)
Use closed dense cell foam tape aganist the outer frame members.
You will have to glue a wood strip inside the vertical end frame to build up just enough room to compress some closed cell foam against the U channel that holds the panels ( there is some distance away that needs shortening up and you damp the outside frame (glued wood) and sandwich the foam againt it (panels/u channel)
Now you dont excite the cheap frame but at the same time you have stiffened all the panels vertically without a possibility of transmitting vibrations where they dont need to go.
I will wager impulse response might improve but have not tested it as of yet.
Regards
David
To answer your question tersely: Yes! That is an issue with all quads. I add extra bracing between the aluminum angles that the panels screw onto and the extrusions outboard of them. On the 63's, a 1/2" long standoff screwed to the angle on one end and to the extrusion on the other end holds the middle of that angle nicely, and makes the panels much more rigidly held. This tightens up the bass a bit. It's not a night and day thing though.
Sheldon
quadesl.com
Sheldon
quadesl.com
It seemed strange that they went to the trouble of adding a brace to the next series of speakers while allowing so much movement internally. Did they change this in the later versions? I have not decided how I am going to modify this. But the idea of using a spacer and tying the inner frame to the outer frame seems like the easiest way to go. I will take my chances that external resonances will not be an issue.
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