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FDP Forum / Non-Fender Gear Reviews / Beam Blockers

gdw3
Contributing Member
**

LA-la-land, CA

Insert clever comment here
Oct 14th, 2011 06:09 PM   Edit   Profile   Print Topic   Search Topic

Apparently, these have been around a while, but I hadn't hear of them until recently (from this forum, of course!)

For those that don't know, it's a simple device that is shaped sort of like the center of a speaker cone. It's a round piece of light-weight material, mounted on a piece of metal that attaches underneath the mounting screws of the speaker. Easy even for a tech klutz like me.

The idea is to block the beam (hence the name!) of high frequencies that come from the center of the speaker that make it very directional.

It actually doesn't block the sound as much as spread it out. You can actually hear yourself when you're standing next to the amp. I tried the 10" version on my SCXD -- pretty loud with my upgraded speaker and power tubes, but very directional -- and WOW what a difference! I can really be heard now in a jam situation. So I put the 12" version on my Rivera Quiana, and boy, does it sound full. A very pleasing, wide field of sound. The drop-off as you walk to the side is very gradual. Love it.

And they're cheap! Like, $16 for the 12". Small money for a huge improvement!

Peegoo
Contributing Member
**********
*********

That chicken

is WRONG, baby.
Oct 14th, 2011 07:16 PM   Edit   Profile   Print Topic   Search Topic

I love them. They make a beamy amp (or speaker) sound a lot wider. And it prevents your amp from popping eyeballs in the crowd directly in the line of fire of your amp.

Bubbalou
Contributing Member
*********

USA

THE LOW END OF UPPER TEJAS
Nov 12th, 2011 04:44 PM   Edit   Profile   Print Topic   Search Topic

gdw3, is the disk 3", 4", or 5" on the 12" speaker's Beam Blocker? Also, where did you get them and are their any vibration noises with it?


Steve Dallman
Contributing Member
*****

Merrill, Wisconsin

Dangit! Hot weather.
Nov 12th, 2011 04:57 PM   Edit   Profile   Print Topic   Search Topic

I've built beam blockers since I first read of the principle in Kevin O'Connor's book, "the Ultimate Tone" which I believe preceded Weber's version.

It need not be complicated. Here's one take on the principle.

Blocker

Steve Dallman
Contributing Member
*****

Merrill, Wisconsin

Dangit! Hot weather.
Nov 12th, 2011 05:02 PM   Edit   Profile   Print Topic   Search Topic

An alternative is the "Mitchell Donut" which uses foam which covers the speaker hole in the baffle, with a hole cut in the center. Here's Al Mitchell's explanation...

"Here's how to make your own speaker directivity modifier:

Cut out a doughnut-shaped piece of acoustically absorbent foam. The diameter should be the same as the speaker cutout in the baffle in your cab, and the diameter of the center hole should be ~3". Attach it to the rear side of your cab's grille using spray contact adhesive (e.g., 3M Super 77, available at Lowe's). Spray a light coating of adhesive on the foam only, and press it against the grille cloth within about 30 seconds of spraying it. You can easily remove the foam with no ill effect on the grille material, if you decide you don't like the effect.

The material you want is open-cell polyurethane foam in sheet form, and there are a number of sources for it. McMaster-Carr is one. I use acoustic foam that the company I own purchases for use in my loudspeaker designs, but that is a matter of convenience. I have tested and subjectively evaluated two thicknesses: 1/2" and 3/4". The limit on maximum thickness is the thickness of your baffle, so make sure you don't exceed that.

With the material I use, the 3/4" doughnut produces the most consistent response at different angles. A 12" speaker has huge variations in its response above ~1200 Hz within just 10 degrees of the speaker's axis. With the 3/4" foam doughnut in place, the on axis response and the response at 40 degrees off axis are almost identical. This is a huge improvement.

If you think about the subject of directivity, you'll easily recognize that there are two ways of saying the same thing: when you say a speaker becomes "beamy" at high frequencies, you're also saying that its on axis response is much brighter than its off axis response. For example, if you equalized the response to be flat on axis (a hypothetical exercise, as that's never what you actually want from a guitar speaker), you'd find that the response off axis falls off pretty rapidly at higher (> 1200 Hz) frequencies.

The reason for the preceding paragraph is to point out that making directivity more consistent over frequency requires that either the on axis or off axis response change. The foam doughnut causes a change in the on axis response, while leaving the off axis response alone. This means that, if you've tweaked your tone with the speaker aimed at your ears, it's now going to sound darker, and you'll need more treble, presence, and/or midrange, depending on the design of your amp's tonestack and other tone-altering circuits. If you're placing your amp on the floor facing the audience, the response you hear will change little or none, but the response the audience hears will now match what you've been hearing all along."

Do a search on "foam beam blockers" and/or Al Mitchell's Donut and you'll get all sorts of info.

I haven't tried it yet.

RDR
Contributing Member
***

I tried to think

but nothing happened!
Nov 13th, 2011 07:53 AM   Edit   Profile   Print Topic   Search Topic

"An alternative is the "Mitchell Donut" which uses foam which covers the speaker hole in the baffle, with a hole cut in the center."

I've used this foam on my PR, DR, SCXD, and even my Microcube (with 6" Weber). It is effective in reducing the beamyness.

Peegoo
Contributing Member
**********
*********

That chicken

is WRONG, baby.
Nov 13th, 2011 07:59 AM   Edit   Profile   Print Topic   Search Topic

Players in the 60s and 70s were aware of beaminess, and some used duct tape/gaff tape patches right on the speaker grills of their amps and speaker cabinets. Not a new concept at all.

But the Weber product is top quality and doesn't buzz at all when properly installed.

The only thing you have to modify (or be mindful of) is mic placement when close micing a cabinet, because if the support strap is in front of the mic, it can affect the tone getting to tape.

Bubbalou
Contributing Member
**********

USA

THE LOW END OF UPPER TEJAS
Nov 25th, 2011 11:38 PM   Edit   Profile   Print Topic   Search Topic

I recently ordered a 5" Weber Beam Blocker from Musicians Friend. At high volume there was some buzz coming from it. I took it out to be sure it wasn't the speaker and no buzz so I took an ~12" piece of 1/2"x3/4" stick of trim molding cut to tightly wedge in the speaker baffle's hole then used some White pliable liquid nails on the speaker side and put the Beam Blocker in place held by a speaker mounting screw at each end. When dry I installed the speaker and no vibrations.

rfrakes331K
Contributing Member

USA

RonHalen Jokingly He Says
Nov 28th, 2011 03:35 PM   Edit   Profile   Print Topic   Search Topic

I am confused. We sart out with post where center blockers are used and then to foam rings with the center open. I have seen the duct tape Xs on grills. Probably SRV's.

Steve Dallman
Contributing Member
*****

Merrill, Wisconsin

Dangit! Hot weather.
Dec 3rd, 2011 10:47 AM   Edit   Profile   Print Topic   Search Topic

Our guitar player's Hot Rod Deville (4X10) is terribly beamy. We tried duct tape X's one gig. He left them on.

KA
Contributing Member

Born to be Retired!

ME
Dec 4th, 2011 07:57 PM   Edit   Profile   Print Topic   Search Topic

I tried the plastic lids from a oatmeal boxes in front of the speakers (center of speaker) on a 4x12 cab I had.
It worked.


gdw3
Contributing Member
**

LA-la-land, CA

Insert clever comment here
Dec 15th, 2011 05:00 PM   Edit   Profile   Print Topic   Search Topic

Ha! That's hilarious.

Sorry, I haven't looked back at this post in a while.

Bubbalou, in answer to your question from over a month ago, the product is from Weber, the famous speaker maker. You install them between the speaker and the frame of the cabinet, and there is absolutely no vibration. I'm not sure of the size of the disk off-hand, as I am at work, but it is basically the same size as the center of the speaker itself.

And by the way, it's more than a disk. It's dome-shaped, and so diverts the sound more so than blocking it completely.

Used my Rivera w/ the 12" blocker at high volumes the other day, and it makes the amp seem like it's more efficient, because you can hear it better throughout the room. I can also do some wonderful controlled feedback without having to stand right in the "sweet spot". An added benefit I hadn't considered!

vegetablejoe

Manila

Dec 21st, 2011 09:40 PM   Edit   Profile   Print Topic   Search Topic

Would a cd be large enough to use as a beam blocker?

Fritz_D_Cat
Contributing Member
**********
*

better living

through chemistry!
Dec 28th, 2011 04:28 PM   Edit   Profile   Print Topic   Search Topic

probably so

Bubbalou
Contributing Member
**********

USA

THE LOW END OF UPPER TEJAS
Feb 22nd, 2012 01:31 AM   Edit   Profile   Print Topic   Search Topic

I bought a Weber Beam Blocker and had to reinforce it to cut the buzz from vibrations. Once I did that it worked fine.

jay1vinton

Hawaii, USA

Perfect is the enemy of good enough
Jan 22nd, 2013 04:54 PM   Edit   Profile   Print Topic   Search Topic

I unwittingly made one for my amp and wondered why it sounded better...

I have a VOX Da-15 practice amp, granted not a Matchless or anything, but it was sounding a bit thin.

There is a Mexican restaurant out here named Cholo's that gives away a sticker that features a bandana and sunglasses wearing cholo, I thought it was cool and put it dead center in the grille, never for anything other than the sticker is cool.

However, I noticed a different range, depth and fullness that I had not heard before..I thought, hum, maybe the sticker is acting as a beam blocker... apparently it is. When it wears out, that's it, but the concept is sound.

Dadical
Contributing Member
**********
**

I am not a complete

idiot - I have several pieces missing!
Feb 28th, 2013 12:03 AM   Edit   Profile   Print Topic   Search Topic

Venue to venue, setup to setup the need (or not) for beam correction will change. Rather than mess with any of my amps at that level, I'll drape a spare guitar strap over the amp at the center of the speaker. Works great.

Grubby

Australia

....feet
Sep 22nd, 2014 02:10 AM   Edit   Profile   Print Topic   Search Topic

i got a 12" weber version for my Fender 75, but it really seemed overly large for a 12". its 11cm in diameter, and with a mounting strap of 25mm width, its like half the speaker cone is covered! sounded like it too. I think a block about the size of the dust cover would be more useful.

FDP Forum / Non-Fender Gear Reviews / Beam Blockers




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