[WGH]

I was intrigued by Albert's article "How to design a low distortion speaker cabinet by Albert Von Schweikert" and the triple wall laminate construction now used in many of his latest speakers.



Since I have previously reviewed and modified my VR2's as seen in Part 1 and Part 2, I thought adding a high density layer would be the next logical next step in the speakers evolution. While visiting a buddy's woodshop he showed me a sample of the Richlite countertop material made from paper. Let me tell you this stuff is dense and heavy and seemed like the perfect choice for my project plus I could cut it into any shape with wood working tools which would be a lot easier than working with stone.



I cut up the sample pieces with a triple chip carbide blade into 3" x 12" pieces. I had two thicknesses to play with: 3/4" and 1" with each piece weighing an average of 1.25 lbs. each (I did say it was heavy stuff).



The 3/4" thickness worked out best and I used 6 pieces per speaker in between every other brace so each chamber in the VR2's triple chamber design had two pieces of Richlite glued to opposite cabinet walls. I attached the Richlite with Excel XPRESS Gel Polyurethane Adhesive.



Each speaker was removed so the Richlite could be installed, the two bottom pieces were installed through the terminal plate hole. A dab of hot melt glue at each end held the slabs in place until the glue set up and dried. Polyurethane glue expands while it dries so it fills any gaps and makes sure the Richlite panels will not vibrate and become a permanent part of the speaker.

I also re-stuffed the chamber behind the bottom woofer with 1 oz. of Kapok which improves and tightens the bass response and keeps the speaker from becoming too boomy in my small room.

The results are amazing. Sounds now start and stop on the proverbial dime and with cabinet resonances further damped music is now clearer. Once again another highly recommended modification. Owners of the original VR4jr and VR4sr speakers should really do this mod, it is a lot easier then installing braces and it will simply blow you away by what these speakers are capable of achieving once you start eliminating the cabinet resonances.

I got all the Richlite I needed for free from Originate, a local natural building material supplier from samples of discontinued colors they had on hand. Your local Richlite fabricator probably has plenty of scraps so get resourceful and you could probably do this upgrade for the cost of the glue.

Wayne

 

[es347]

Nice move Wayne.  My annies have the bracing in the VSA picture so no need there.  I would be a bit nervous about removing the drivers as they are seated in some sort of world class adhesive and could be easily damaged if one didn't know what one was doing.  I've got a pair of Acoustic Energy bookshelf speaker which are a great little speaker in their own right.  I may see if such a mod would be possible on them.  I also have a pair of ML aerius i's that have a removable panel on the woofer cabinet.  I may have to fire up the old table saw and see what sort of damage I can do.  Great post by the way.

[WGH]

Thanks, luckily the speakers in the VR2's fall right out after the screws are removed.

Wayne

[es347]

Thanks, luckily the speakers in the VR2's fall right out after the screws are removed.

Wayne

You might give Albert a call and see if he could provide some of that super duper adhesive he uses now.  It is used on submarines to help deaden sound for silent running...no kidding.  Not sure if it's strictly BS but another tweak is to use brass screws....or better yet screws made from unobtainium.

[WGH]

I like taking stuff apart too much to glue the speakers in. 

I have heard of using brass screws before, even a guy at RMAF thought they were great too - was that you? I was thinking of using t-nuts with brass screws since the existing speaker screws go straight into the MDF cabinet and tend to strip out the particleboard, then I have to get out my wood glue and toothpicks.

Wayne

[es347]

"the existing speaker screws go straight into the MDF cabinet and tend to strip out the particleboard"...hence, the super duper adhesive.

[rajesh]

I chanced upon this old thread through a link in GR X-LS. It would be interesting to hear some experts take on modifying existing speaker using additional bracing, which I'm sure would modify the speaker charecterstics as it would reduce the speaker volume.

[WGH]

I started my bracing experiments on a pair of JBL L100's, this improved the speakers sound so much that adding bracing to the VR2's was number 1 on my list of things to do once the newness wore off.

The VR-2's have an approximate interior volume of 1.63 Cubic feet. The braces and Richlite take up about .15 cubic feet or about 9%. The positives like better imaging, depth of field, tighter bass, and a clearer mid-range more than make up for any negative changes from the reduced volume. I think deep bass actually increased because the energy is no longer used to flex and vibrate the cabinet sides.

Wayne

[JackD201]

Being quasi-TLs the differences in internal volume can be made up for by changing the density of the stuffing material or changing the stuffing material itself. 

[JackD201]

"the existing speaker screws go straight into the MDF cabinet and tend to strip out the particleboard"...hence, the super duper adhesive.

Actually the putty floats the drivers. The screws are pretty much there for aesthetics. Albert left me some for a pair of rear ribbons I have to replace for a client. They left me the tool to yank the drivers out too. They putty is like clay but it doesn't dry out.

Oh, great job as always Wayne!