Heresy Back stiffness

[Invidiosulus]

About 7 years ago I decided that I didn't like the amount of resonance I could feel on the back of my Heresy 1's.

My solution was to cutout a back piece of 3/4 MDF and sandwich it over the stock back with some long woodscrews into the stock holes with a few pieces of weather stripping between the 1/2" back and the new 3/4" add on so nothing would buzz.

Tonight I did some vibration testing with the Room EQ Wizard Software and a Fishman Piezo Violin Pickup.

Using REW I ran a 40 to 700 Hz sweep with the pickup element taped on the back of the Heresy.

The pickup wasn't calibrated so the actual dB levels on the graph are not accurate but you can still see the difference in output.

The two lines on the graph represent the Heresy with the stock 1/2" thick back and the Heresy with my added 3/4" MDF thickener.

The yellow line is stock and the sort of teal line is with the thickener.

This indicates to me that I really want to build some Heresy cabinets out of double layer 3/4" for a 1 1/2" thickness all the way around.

It also solidifies my resolve to use 3/4" for all the pieces when I build some Khorns.

Peace,

Josh

[ZombieWoof]

About 7 years ago I decided that I didn't like the amount of resonance I could feel on the back of my Heresy 1's.

My solution was to cutout a back piece of 3/4 MDF and sandwich it over the stock back with some long woodscrews into the stock holes with a few pieces of weather stripping between the 1/2" back and the new 3/4" add on so nothing would buzz.

Tonight I did some vibration testing with the Room EQ Wizard Software and a Fishman Piezo Violin Pickup.

Using REW I ran a 40 to 700 Hz sweep with the pickup element taped on the back of the Heresy.

The pickup wasn't calibrated so the actual dB levels on the graph are not accurate but you can still see the difference in output.

The two lines on the graph represent the Heresy with the stock 1/2" thick back and the Heresy with my added 3/4" MDF thickener.

The yellow line is stock and the sort of teal line is with the thickener.

This indicates to me that I really want to build some Heresy cabinets out of double layer 3/4" for a 1 1/2" thickness all the way around.

It also solidifies my resolve to use 3/4" for all the pieces when I build some Khorns.

Peace,

Josh

WoW , U JUST ansewered the nagging questions i'm getting from my wife as to why I'm wrapping the whole CornWall cabinets with 3/4" plywood in Oak & adding 3/4" MDF to the backs & bottoms as I'm upgrading the 4 Cornies to 4 CornSacla's But there was no way I could measure that myself ,just a Gut Hunch ! that it would be better ! Should I also be doing this to the motorboard as well ? as i was gonna just run a few strips of 3" x 1" oak on edge between the drivers to stiffen it up ??

Mike

[Invidiosulus]

Your cornscalas are going to be solid.

I don't really know about the motorboard.

How are you planning on mounting the drivers, front or back ?

I would try and keep from adding too much to the interior so you don't change the volume for the woofer.

In Robi's Italian cornscala thread he was making a square cutout brace that connected the motorboard, back, and sides IIRC.

Hard to say how it would test either way as I've really not done much of this sort of thing yet and I don't plan on building cornscalas.

If it helps you convince the wife then it's worth it.[]

-Josh

[IB Slammin]

In the old Alcorns, (frankinwalls[:'(]) I used 1-1/2" x 1-1/2" steel angle across the motor board not letting it touch the side walls. (note 3/4" ply on the CW back)

Didn't think that there would be much deflection in the 15-1/2" sides. (??)

tc

PS: The use of steel angle changes very little as to the volume of the bass bin and is much stronger than wood. It can also be dampened with rope calk. Not exactly the same, but it is in the context of bracing. Worked well for me.

[ZombieWoof]

In the old Alcorns, (frankinwalls[:'(]) I used 1-1/2" x 1-1/2" steel angle across the motor board not letting it touch the side walls. (note 3/4" ply on the CW back)

Didn't think that there would be much deflection in the 15-1/2" sides. (??)

tc

PS: The use of steel angle changes very little as to the volume of the bass bin and is much stronger than wood. It can also be dampened with rope calk. Not exactly the same, but it is in the context of bracing. Worked well for me.

I added another 3/4 of fiberboard to the backs & gonna over lay that with red oak 1/4" ply ,soo all will match

yeah that steel angle will work for me and seal between the steel & motorboard by using automotive cork gasket material that Bob Critites told the to use for a gasket for the horns to motorboard

that will stiffen it up & not take up any volume ....... great Idea ThanX

Mike

[JohnA]

Some of my Heresies came with risers, but I don't need them. I took pieces of the riser and glued and screwed them to the inside back of each Heresy. I haven't bothered to test them, but it was easy to do.

[cfelliot]

Dup Removed....

[cfelliot]

Some of my Heresies came with risers, but I don't need them. I took pieces of the riser and glued and screwed them to the inside back of each Heresy. I haven't bothered to test them, but it was easy to do.

Same here. I took a piece of 1" oak that I had and screwed and glued it diagonally across and on the inside of the back.