Speaker Directivity and Speaker Beaming Issues (Poll)

[rsf1977]

5. centered the foam over the center marking tack and pinned the foam to the grill cloth

There's your likely problem. See: http://thegearpage.net/board/showthread ... 956&page=8 . I quote: "What is important is that there be no flanking path for sound to bypass the absorber around its edges." If your grille cloth stands off the front surface of the speaker baffle at all, there will be just such a flanking path. You need to get a sheet of foam large enough to cover the whole face of the cabinet and cut holes in that or, alternatively, install the foam on the front face of the baffle or in the speaker cutouts.

Ok great! Thanks Jay i'll try it inside. One quick question i just got the #3 density foam too. Is there one that's more suitable for this i know there was some discussion about #3 and #4 being used i have both in 1/2" and 3/4"

 

[jojo]

I've been grappling with "the beam" for a long time. I play wireless and often run around out front (supposedly to showboat, but really just checking the mix since I often run sound from the stage). There's nothing worse than thinking the tone is sweet, only to run out front and pass thru the "cone of harshness" emanating from a 4x12 cab. For some time I've been programming my patches sitting on the floor 10 feet away, to help mitigate this. But I'd love it if my beam tone was closer to my off-axis sound, since that's the sound most of us fall in love with.

I just ordered 10 squares. That should get me thru a couple of cabs, allowing for the inevitable screwups plus at least one for my six year old to play with and probably destroy. :lol: I'll post my impressions once I hear how it goes.

 

[rsf1977]

I've been grappling with "the beam" for a long time. I play wireless and often run around out front (supposedly to showboat, but really just checking the mix since I often run sound from the stage). There's nothing worse than thinking the tone is sweet, only to run out front and pass thru the "cone of harshness" emanating from a 4x12 cab. For some time I've been programming my patches sitting on the floor 10 feet away, to help mitigate this. But I'd love it if my beam tone was closer to my off-axis sound, since that's the sound most of us fall in love with.

I just ordered 10 squares. That should get me thru a couple of cabs, allowing for the inevitable screwups plus at least one for my six year old to play with and probably destroy. :lol: I'll post my impressions once I hear how it goes.

i would love to hear how it goes! Punishment for destroying a speaker donut should be 5 minutes sitting in the treble beam of death, that kid wouldn't go near a Krispie Kream let alone a piece of foam ever again lol

 

[jojo]

:lol: :lol: :lol: :lol:
I don't know if child protective services would approve of that system of "time out". But as an avid lego engineer who spends way too much time on the floor in my studio, Gracie is quite familiar with the beam. It's interesting how her toys and artistic creations tend to be strewn around quite randomly, except for a narrow wedge radiating from the front of the cab...... I guess I'll know that the donuts work if everything becomes totally random. :mrgreen: Before and after pictures of that would be an interesting marketing gimmick for Jay.... :idea:

 

[rsf1977]

:lol: :lol: :lol: :lol:
I don't know if child protective services would approve of that system of "time out". But as an avid lego engineer who spends way too much time on the floor in my studio, Gracie is quite familiar with the beam. It's interesting how her toys and artistic creations tend to be strewn around quite randomly, except for a narrow wedge radiating from the front of the cab...... I guess I'll know that the donuts work if everything becomes totally random. :mrgreen: Before and after pictures of that would be an interesting marketing gimmick for Jay.... :idea:

now that would be real imperical proof

 

[rsf1977]

K so tonight I learned one super important thing about the difference between Mcmaster foam densities. #4 doesn't seem to do much for blocking the beam and #3 seems to work brilliantly!!! It seems once I installed the #3 density mcmaster foam everything discussed about the Mitchell donuts came to be. The beam was gone the tone became even everywhere I stood, within reason of course, but it was like night and day! For those that might think what could possibly be the difference between 1 level of density, let me tell you the materials are immensly different #4 is like the stiff foam you find in a padded metal gear case very stiff and solid. #3 is very mushy soft like what you would find in a seat cushion. Whatever makes #3 work I'm not sure but the results were nothing short of amazing. Thanks jay for all the help! This is the solution I've been searching for for years. Man I'm excited about this lol.

 

[rsf1977]

Mitchell Donut Foam Experiment Update:
So I now installed McMaster #3 Density foam in both my Mesa Standard Recto 4x12 (V30s) and my Voodoo Amps 4x12 (V30s & T75s). Here's how it went.

:arrow: Mesa Standard Recto 4x12 (V30s):
Removing the grill cloth isn't too much work, but you have to remove the back of the cab then unscrew it from the inside front baffle to release the grill cloth and frame. So once I had the grill off I noticed the grill had four neat almost square sections already built into it, 1 in front of each speaker. So I cut the 3" circle in the center of the foams then cut each piece to fit in each square on the grill. I didn't use any adhesive spray they each fit in nice enough to hold themselves in. So first I tried the 3/4" foam i just put the grill in place with out screwing it back and tested it. The 3/4" performed excellently the beam was all but gone and the sound was very even at much much wider radius then without it. So feeling confident I had a winner I tried the 1/2" anyway. I was very impressed with the 1/2" too! The difference between the two of them was very minimal. The 1/2" did the job but let a little more of the high end through so i decided to go with that, I figured it was better to error on the side of effecting the tone less. Also I needed to dial in a touch more presence to bring back the sizzle that got taken away by the foam but just a tad.

:arrow: Voodoo Amps 4x12 (V30s & T75s):
Well this one wasn't as easy to install. Since I had never looked in my Voodoo cab I contacted Voodoo Amps to find out if there was an easy way to get the grill off before I opened up my cab up and start poking around. I was quickly told it's an involved process. So I opened it up anyway lol. First, let me say if you've never seen the inside of one it's probably the cleanest, sturdiest built 4x12 I've seen. It's beautiful and as solid as solid gets. So, after admiring the engineering I realized they weren't kidding this would be hard. I would have to remove the side handles and the front baffle, which has a whole bunch of other precarious issues with trying not to yank wires out during the process etc. So I decided to go the easy route, I would unmount the speakers and put the foam through the speaker cutout in the baffle easy as pie. So I cut the 3" circle in the center and measured the foam to fit the opening and cut the rounds making the outer diameter a 1/2" wider then the opening to ensure no sound could get around the foam. I roughly placed one each of the 1/2" and 3/4" piece in to check the fit. The 1/2" had plenty of space between the baffle and grille and would need to be glued in to stay put, the 3/4" fit slightly snug barely touching both and would stay in place without any adhesive. So I went with the 3/4", I knew already that the Voodoo had more of a beam issue with the 75s so I was completely confident after testing the mesa cab that either foam would be fine and the extra 1/4" might help with the extra beaminess. So I auditioned and same results the beam was almost all gone and the tone was even everywhere. And again, I needed to dial in a touch more presence to bring back the sizzle that got taken away by the foam, but like I said just a tad.

Conclusions:
1. the foam NEEDS to block all paths of the audio no gaps for the sound to get around it uneffected.
2. the #3 density Mcmaster foam seems to perform better in this application then the #4
3. there is a slight loss of presence that needs to be dialed back in after installation.
4. tone became more even at a much wider range of listening positions
5. high frequency beaming was almost completely eliminated

 

[rsf1977_again]

I'm going to try this again. Anyone have anything new to share on the subject?

 

[pawleep]

awful lot of un-likes for these, wondering if maybe there should be a slight gap around the edges to let a little more of the highs through, depending on cab and speaker type?