#1
Hi there,

I just wanted to start this thread because there is not much discussion and information about this topic on the internet.
So this is about beamblockers. ...The stuff you put in fromt of your speakers to get rid of the ice-picky treble that is fired off in the very center of your speaker.
What do we want: 1. The shrill heights you hear when the speaker is pointed directly to your head should be nicely attenuated. 2. The sound you hear when you stand off-center, which is more balanced automatically, should not be muffled. 3. Mic'd up sound (nic of course NOT at the center of the speaker) should not be muffled.
Until now, there are mainly three methods of blocking the beam of guitar speakers: The buyable hard-surface beamblocker - which is often seen imitated by DIY solutions such as a CD; The foam-donut which coveres the whole area of the speaker but has a hole in the center; The Foam circle, about the size of a CD, which is placed at the center.
There is a very good comparison video of these three types here: https://www.youtube.com/watch?v=bmECNGU-4HM

My solution combines two of the types tested here...
I have built a 2x12 cab with two Jensen Tornado Speakers (neodymium magnets..very clear but sometimes shrill highs and they beam a lot..may also be because they are back-mounted..never mind..) I have not used grill cloth but metal grills in front of the speakers which does let all the treble pass through.
I've tested the CD and the foam circle made from 2 centimeters (about 3/4 inch) acoustic-foam and came to the following conclusion:
With MY setup, the Foam circle itself does not do that much. There is still a LOT of treble compared to off-center sound. The CD performed better but as the hard surface reflects soundwaves instead of absorbing them, you get the hollow sound you hear in the video. I then had the idea of combining the CD and the foam circle, so the foam is glued to the CD, the foam is ponting towards the speaker. This does attenuate the treble even better than the CD alone, sounds closer to off-center, but I don't get the hollow sound. I've also a-b-tested standing off center, which sounded almost identical with and without the beam blocker. (thx to my sister...le me playing quite loud yelling repetitively "hold it in front of the speaker!" ... "put it away!" )
I guess mic'd up sound will be fine too, like shown in the video (I can't test it because I don't have a microphone, ecxept in my phone...nope).

So, end of the testing; in the next days I'll get a can of black plastic spray paint to give the cds a better look and install the beam blockers behind the metal grills. Pictures will follow.

Let me know what you think
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#2
There's also the THD solution, which involves inclusion of the beam blocker as part of the baffle construction:



All beam blockers are kludges and most treble beaming is related to cabinet design and/or speaker selection.

Speakers "beam" or begin to exhibit beaming characteristics involving treble relating to speaker size. The formula is 13,500 (speed of sound in air in inches per second) divided by the actual cone diameter to give you the frequency where beaming will ordinarily begin. A 12" speaker with an actual cone diameter of around 10.3" will begin beaming around 1300Hz.

A 4x12, however, will act like one large speaker, and begin beaming at around 500hz.

I use a speaker cabinet that uses three sizes of speaker with crossovers between them. Mine has a 15"LF driver, a 6.5" mids driver and a 1" tweeter. A 15" speaker will begin to beam at around 1000Hz. So the first crossover cuts the sound to that speaker somewhere below that point and transfers higher notes to the 6.5" driver. That driver might begin to beam around 2500Hz, so a second crossover component will transfer notes above that point to the 1" tweeter. That won't begin to beam significantly until about 13,500Hz, so you will, in theory, have a single cabinet that will generate all frequencies with as wide a dispersion as possible. Thus:



It's worth noting that in this case, the 1" tweeter is well-balanced with the other two speakers, but that you can order the cabinet with switching that will either L-pad (diminish) the response of the tweeter or delete it altogether.
#3
to be exact, a lot of electric guitar technology used today is a kludge, and I'm not talking about tubes and stuff (..well, I won't change my AMT Stonehead SH-50-4 Solidstate for any tube amp..it kicks ass.) ..What I mean is for example most guitars are passive, unbuffered outputs which has a ton of disadvantages. This is all technology from decades ago but it produces the sound everyone loves. The cab from your post is built like a fullrange PA cab. I have never seen anyone using cabs like that for driving directly from a guitar amp. Would it sound like a guitar? How would you mic this up at a gig? But yeah, of course sound wise, a 2- or 3-way cab will sound much better in general. It seems that bass guitar technology is often more advanced today. Most modern basses are active and buffered, cabs are often 2-way systems with additional bass-reflex. I wonder why all of this is rarely used with guitars.
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#4
Here is a picture, as promised. The foam is glued to the cd with hot gue, the cd is glued to the grill with 3M VHB 5952F Tape (special double sided tape for painted and powder-coated surfaces. rock solid.) It looks OK. Maybe I will buy screw-mounted beamblockers someday and modify them with foam. Click on the picture to viel full-size.
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#5
Quote by offspring93
This is all technology from decades ago but it produces the sound everyone loves. The cab from your post is built like a fullrange PA cab. I have never seen anyone using cabs like that for driving directly from a guitar amp. Would it sound like a guitar? How would you mic this up at a gig? But yeah, of course sound wise, a 2- or 3-way cab will sound much better in general. It seems that bass guitar technology is often more advanced today. Most modern basses are active and buffered, cabs are often 2-way systems with additional bass-reflex. I wonder why all of this is rarely used with guitars.


I have a cabinet from 1971 that has a pair of 15" Altec Lansing speakers in a large ported cabinet with a mids/highs tweeter. This is a guitar cabinet (that, admittedly, could probably handle bass as well). In the late '60's and early '70's, manufacturers weren't locked into 12" speakers for guitar. Since then, however, t's just been easier and cheaper for them to build square boxes and buy speakers in volume and advertise that they're just like folks' guitar heros use. Crossovers and correctly ported cabinets are expensive to design and make. Square boxes with just one speaker size aren't.

You're absolutely correct that the cabinet from my post (I have two like this and two that are a similar design) is built like a PA speaker. It is, in fact, a cabinet originally designed as a flat-response setup for bass. It'll easily do 35Hz and below with no farting out and well past 18Khz on the top. As you note, bass players get the cool tech, while guitar players assume that 50-year-old tech is "good enough."

And yes, it sounds like whatever you actually put through it. And yes, it not only looks like a PA-style cabinet, but can work as one if you need it to.

Aside from requiring no "beamblocker evolution," they deliver a lot more of what modern guitar players are looking for (when it comes to bottom end, particularly). A few years ago Steve Lukather, playing a 7-string, worked with ISP Technologies to produce a powered subwoofer that would work with his 100W tube amp and 4x12. The sub (available from several major online dealers) is called the Vector SL. It's got some slick electronic technology that works with any tube amp head output, feeding the mids/highs to the 4x12 and the bottom end through a 15" subwoofer in a large ported cabinet, powered by a 600W power amp built in. http://www.musiciansfriend.com/amplifiers-effects/isp-technologies-vector-sl-steve-lukather-600w-active-guitar-subwoofer

At one point I used a pair of tube-ported 2x12 cabinets (each fitted with a pair of 1165 tweeters) that were ported and sized for 52Hz bottom end reproduction from Eminence Delta ProA speakers. I started them with a 100W stereo tube amp and moved to a 1500W Carvin DCM1540L power amp. Those cabinets worked pretty well, but they were heavy (very), thanks to the magnet structures on those Deltas and the 3/4" plywood (and brutal LineX coating) used in construction. The current cabinets are half the weight each (everything's neo-based), handle more power, go lower and respond to EQ better.

I don't mike these cabinets. There's no need to. If I'm using a tube amp setup it's usually a separate tube preamp (like a Mesa Triaxis) into a tube or solid state power amp. I can run directly into the board off the preamp. If I'm not using tubes and using a modeler (Axe, Pod, etc.), I can run directly into a solid state preamp and into these cabinets, and why mike when I can run directly into the PA as well? The same goes for if I'm playing keys or bass.
Last edited by dspellman at Jul 18, 2015,
#6
Wow man you got some great knowledge!
As a bass player, I'd be pissed off if my guitar bandmate would bring a friggin subwoofer. I have researched a bit, some say they tried feeding a flat response PA cab from a guitar amp and it sounded flat and lifeless. Electric guitar sound is mostly midrange frequencies. ..Maybe because we are used to this..common guitar speakers pump out mostly midrange. They don't do much "real" low-end, no PA-like high end and some of the extremely populare ones (V30) "color" the midrange a lot. The last thing in particular annoyed me so I got the Jensen Tornados which are more linear. I tried to review them in the Electric Guitar forum here at UG. (not that much experience, as you probably have noticed, so no full UG review) You're right for sure that you could build a fullrange cab which works perfectly with a guitar amp. But I got the weird feeling that the absolutely non-fullrange output of a common guitar head and the non-fullrange response of a guitar cab is part of the soul of this instrument.

I Guess flat response fullrange systems / straight-to-the-mixer-situations are great with good amp modelers. I have tried some at a local music store but I guess I am quite conservative in this area.. Even though I work in an IT company, I don't want to play a computer, I want the stuff that generates my tone as analog as possible. ..that's just me, call me stupid. ah and one thing..I don't trust a computer further than I can throw it. I use a few basic tones, a handful of stompboxes and thats it. I'm pretty lazy in dialing in and saving and using many different sounds.
Speaking of alternatives to miking a cab on stage, which can be a pain in the ass..small stages, lot of noise, cheap mics getting positioned sloppy, get kicked during the show..seen it all.. ...there is something very interesting I might buy and try in the very near furure: the Tube Amp Doctor F.A.N.T.A. ..a small passive box you put between your amp and cab and you get a nice XLR signal from it. Reviews say it sounds great. Most non-modelling amps emulated line-outs suck balls..the good stuff comes out the speaker output. This could be extremely useful at small gigs. I guess this is getting a little off-topic here..just a little....
Right-wing morons, go suck my d#ck!

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#7
The electric six-string has hampered itself sonically due to the sound reinforcement choices made in the 30's that continue today due to manufacturer laziness and an oddly traditionalistic herd mentality on the part of a lot of guitar players. An acoustic six-string actually has a lot more range (and that's why we've seen "acoustic guitar amps" with ported closed-back cabinets and tweeters) and that gets captured with full-range microphones, piezo saddles, etc. In fact, in order to make a solid body guitar sound more like an acoustic, you add piezo saddles and a preamp.

But as extended-range guitars get used more often, the old '50's style speaker setups we call "guitar cabinets" are really showing their deficiencies. The truth is, that's not the "soul" of the instrument's sound. That's just what we have left after we've lost the rest.

The setup I'm using live has a modeler feeding an electronic piece that offers power amp sims (EL34, 6L6, etc.) and IR-based cabinet sims. While the modelers have, so far, tended to copy the old-line sounds popularized in the 60's, the editing software has allowed us to expand things. And guitars like the Variax offer a huge range of guitar (and bass!) sounds that need to be accommodated.

As you noted, there are a lot of variables involved in close-miking setups. Add to that stage volume and the lack of control with amp noises feeding through vocal mikes, etc., and you can guess why modeling solutions are a first choice.

And, as we slowly lean back on topic, you don't have issues with beaming, mechanical and acoustic coupling and phase issues due to timing differences between stage cabinets and PA output, etc.
Last edited by dspellman at Jul 18, 2015,