Beam Blockers & 410/810?

[Grissle]

Just throwing this out there for discussion. Using Beam Blockers on one side of a 410 or 810, might it help dispersion or not? This is different than a .5 Alignment setup obviously, but how different?

 

[CL400Peavey]

It is a mechanical filter versus an electrical one. similar results to a point I would expect.

 

[will33]

Could help some. You'd still have combing/beaming with side by side drivers though I think it'd be moved higher in frequency.

Beam blockers work, though they reduce sensitivity some I think. They damp the highs radiating from the outer areas of the cone but allow them through the hole in the middle, essentially creating a smaller radiating surface for the highs (less beaming).

They might be used to better effect on vertically aligned large drivers, like a 115 or 215 cab.

 

[Scottkarch]

Cool. I've never heard of them. [Invalid or Expired Link Removed]
Would you have to worry about high excursion speakers bumping the mount at the speaker edges?

 

[xk49w]

Now that is an interesting idea for beaming reduction. Rather than use a series inductance to electrically low-pass one vertical pair of the 410 (for a 410.5 alignment), use a frequency-selective acoustic absorber in front of one vertical pair to achieve the same goal. The unmodified pair would produce full range and the modified pair would pass lows but attenuate highs.

The electrical low-pass method causes a phase shift in the low-passed pair causing a slight response dip due to cancellation. The acoustic absorber however is purely resistive - no phase shift.

The material to use is open-cell polyurethane foam in sheet form such as McMaster-Carr 8643K512.

(Ref. Link Removed.

 

[xk49w]

Cool. I've never heard of them. [Invalid or Expired Link Removed]
Would you have to worry about high excursion speakers bumping the mount at the speaker edges?

Those do not work as advertised. The cause of beaming is not due to highs radiating from the center of the cone, rather from the large radiating area (from the entire cone surface).

 

[will33]

Cool. I've never heard of them. [Invalid or Expired Link Removed]
Would you have to worry about high excursion speakers bumping the mount at the speaker edges?

That looks like the opposite of what I think of as a beam blocker.

What I'm thinking of is a foam disk the size of the speaker with a small (3"-4") hole in the middle. It damps the highs from around the perimeter of the cone so they just "escape" through the small middle hole. Sort of like having the highs radiated by a small 3 or 4" speaker rather than the whole larger 10-15" cone.

 

[kennyZ]

Hi. So, I've been lurking a bit. Saw this and the 4x10.5 threads... As ugly as it might be, a little acoustic treatment placed between vertical pairs might be a very simple, completely reversible, totally portable idea that can cut down on midrange frequency phasing issues. Placed perpendicular to the cabinet surface, of course _|_

I'm not ready to give plans or details on construction, but we're a crafty, creative bunch here. I know you'll do fine while I play board games with the kids before the basketball game.

 

[will33]

What would that do exactly?

You mean a partition extending out from the front of the cab?

That could have some benefits in a recording environment. Not seeing it when the cab is driving a bar room/club though.

 

[kennyZ]

Game over...

Yes, like a partition. It would be of the sound "absorbing" type of material, where the longer(lower) sound waves continue to pass but the shorter waves become quite attenuated. Even if the material is mostly reflective of higher frequencies, bonus=dispersion. Also the possibility for higher frequency diffusion...

I confess to thinking out loud, not always a finished product.