i am considering building a guitar cab with one 12" speaker (112) or two 12" speakers. (212)
the fundamental reason for building one rather than buying one is, i cannot satisfied with the cabs on the current market. though i experienced many high-end guitar cabs, they cannot for me.
the one of the key reasons is dispersion. whatever they are 112, 212 or 412, they have very bad dispersion. according to the position relative the the guitar cab, the sound becomes completely different.
especially, because the speaker is big (12"), there is beaming effect. there are too much high freq in front of the speaker, while not much on the side of the speaker.
the typical guitar cab design is like this : 2x12 Vertical Guitar speaker empty cabinet orange tolex | Reverb
they screw the speakers onto the flat baffle, regardless of they are front loaded or rear loaded.
the baffle attached on a little inside of the sidewall. so, the edge that the baffle and the sidewall meet is not smooth.
any idea to get good dispersion to improve the tradition guitar cab design?
here are a few ideas in the market.
<diffuser in from of the speaker>
ToneBra by LA Custom Electric | dbinstrumentamp.com 12" Beam Blocker (4" Dome) What is Deeflexx? | Hoovi
i tested the 3 diffusers above and they can be a little effect on blocking beaming. but not satisfying level at all in terms of dispersion.
<innovative cab design>
XF Guitar Cabs
i haven't tested this cab. but no fave in the market.
the fundamental reason for building one rather than buying one is, i cannot satisfied with the cabs on the current market. though i experienced many high-end guitar cabs, they cannot for me.
the one of the key reasons is dispersion. whatever they are 112, 212 or 412, they have very bad dispersion. according to the position relative the the guitar cab, the sound becomes completely different.
especially, because the speaker is big (12"), there is beaming effect. there are too much high freq in front of the speaker, while not much on the side of the speaker.
the typical guitar cab design is like this : 2x12 Vertical Guitar speaker empty cabinet orange tolex | Reverb
they screw the speakers onto the flat baffle, regardless of they are front loaded or rear loaded.
the baffle attached on a little inside of the sidewall. so, the edge that the baffle and the sidewall meet is not smooth.
any idea to get good dispersion to improve the tradition guitar cab design?
here are a few ideas in the market.
<diffuser in from of the speaker>
ToneBra by LA Custom Electric | dbinstrumentamp.com 12" Beam Blocker (4" Dome) What is Deeflexx? | Hoovi
i tested the 3 diffusers above and they can be a little effect on blocking beaming. but not satisfying level at all in terms of dispersion.
<innovative cab design>
XF Guitar Cabs
i haven't tested this cab. but no fave in the market.
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A vertical line array widens horizontal dispersion while narrowing vertical dispersion.
Two vertically aligned 12" speakers give better horizontal dispersion than one.
A vertical line array of four 8" speakers would give even better horizontal dispersion.
However, the enclosure may be too narrow to place your amp head on!
Two vertically aligned 12" speakers give better horizontal dispersion than one.
A vertical line array of four 8" speakers would give even better horizontal dispersion.
However, the enclosure may be too narrow to place your amp head on!
idnotbe,
One thing you might consider is buried in the text of the 12" beam blocker link that you added to your post. The beam blocker and the tonebra are essentially offering identical solutions. The only difference is how they attach to the baffle. What I'm recommending will either verify that they both will work for your purposes, or that neither one of them will work for what you're trying to accomplish.
Don't know about the third solution, but it appears to "funnel" sound away from the front of the amp and off to the sides.
The buried information that I'm referring to is a historical sentence on the beamblocker site. It mentions that Stevie Ray Vaughn essentially created his own beamblocker / tonebra solution a long time ago, and before either one was ever invented. You can easily duplicate their function if you buy a roll of gaffer's tape and attach circles of varying size to the grille cloth of any amp you own and see how it works. The reason I say gaffer's tape is that the adhesive on common duct tape will stick on the grille cloth after the tape is removed and muck it up. It'll work, but only a good bath in straight alcohol or mineral spirits will clean it off if you do.
You may find that Stevie's tape solution is exactly what you're looking for. The only difference is that both of the commercial solutions use a curved plastic disk. It may or may not make a lot of difference. Try a piece of cardboard, a plastic circle cut out of a milk jug or a 5 gallon plastic bucket, or anything else that you may have on hand.
Stevie is famous for torturing his amps in order to get good tone. Legend has it that he used to lay his Twin Reverbs on their back so the speakers played straight up into the rafters. That's a horrible thing to do, as it traps all the heat from the amp and cooks everything to death. However, if you're using a head and a cab instead of a combo, laying the cab on its back is absolutely fair game.
Try orienting the speaker cab "26 Ways From Sunday" as you experiment -- speakers pointed up, speakers pointed face down (and lifted off the stage a couple inches with some wooden blocks), and even try speakers pointed backwards away from the audience. I've heard that Zepplin used to play amps into the back wall of the stage if the venue was gymnasium - sounding. The purpose was to play to the reflection, rather than the direct sound of the amps. Depending on the sound characteristics of each venue you play, you might have to try them all to accomplish your goal.
Another thing to consider that you may have overlooked is that in an indoor venue, an open backed cabinet is the way to go, as the sound out of the back of the cab goes into the room and smooths things out for you. An outside venue is death for an open backed cab, as the sound in the back simply disappears into the air and never comes back again, so a closed back cab is the order of the day for outside. The problem with closed back cabs is that they are pretty much all guilty of beaming to some extent, but you may be able to mitigate things with patches of gaffer's tape or a tonebra or a beam blocker.
Good luck, and hope this helps.
Dave
One thing you might consider is buried in the text of the 12" beam blocker link that you added to your post. The beam blocker and the tonebra are essentially offering identical solutions. The only difference is how they attach to the baffle. What I'm recommending will either verify that they both will work for your purposes, or that neither one of them will work for what you're trying to accomplish.
Don't know about the third solution, but it appears to "funnel" sound away from the front of the amp and off to the sides.
The buried information that I'm referring to is a historical sentence on the beamblocker site. It mentions that Stevie Ray Vaughn essentially created his own beamblocker / tonebra solution a long time ago, and before either one was ever invented. You can easily duplicate their function if you buy a roll of gaffer's tape and attach circles of varying size to the grille cloth of any amp you own and see how it works. The reason I say gaffer's tape is that the adhesive on common duct tape will stick on the grille cloth after the tape is removed and muck it up. It'll work, but only a good bath in straight alcohol or mineral spirits will clean it off if you do.
You may find that Stevie's tape solution is exactly what you're looking for. The only difference is that both of the commercial solutions use a curved plastic disk. It may or may not make a lot of difference. Try a piece of cardboard, a plastic circle cut out of a milk jug or a 5 gallon plastic bucket, or anything else that you may have on hand.
Stevie is famous for torturing his amps in order to get good tone. Legend has it that he used to lay his Twin Reverbs on their back so the speakers played straight up into the rafters. That's a horrible thing to do, as it traps all the heat from the amp and cooks everything to death. However, if you're using a head and a cab instead of a combo, laying the cab on its back is absolutely fair game.
Try orienting the speaker cab "26 Ways From Sunday" as you experiment -- speakers pointed up, speakers pointed face down (and lifted off the stage a couple inches with some wooden blocks), and even try speakers pointed backwards away from the audience. I've heard that Zepplin used to play amps into the back wall of the stage if the venue was gymnasium - sounding. The purpose was to play to the reflection, rather than the direct sound of the amps. Depending on the sound characteristics of each venue you play, you might have to try them all to accomplish your goal.
Another thing to consider that you may have overlooked is that in an indoor venue, an open backed cabinet is the way to go, as the sound out of the back of the cab goes into the room and smooths things out for you. An outside venue is death for an open backed cab, as the sound in the back simply disappears into the air and never comes back again, so a closed back cab is the order of the day for outside. The problem with closed back cabs is that they are pretty much all guilty of beaming to some extent, but you may be able to mitigate things with patches of gaffer's tape or a tonebra or a beam blocker.
Good luck, and hope this helps.
Dave
A larger version should give you what you want. Not as practical as other solutions.
More fun.
More fun.
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Oh! Forgot to mention one more thing. Based on my own gigging experience, I would be surprised if you see a lot of difference between a single 12" cab and a double 12" cabinet. Partially blocking the center of the speaker, using an open back cab, and / or orienting the cab away from the audience in some way shape or form will make a bigger difference.
Dave
Dave
HAH--Printer2, I love your solutions! As you said, they'll generate a ton of conversation, but maybe not the most practical. Made me smile, though.
Dave
Dave
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Physics does not really care what we want, we still have to play by her rules. Knowing what they are does help. I was trying to find a 8" speaker with a metal cone similar to the second picture (much smaller though). They were used in public addressing in places like hospitals and schools with ceiling speakers. There were acoustic lenses made of perforated metal plates but I can't seem to get Google to realize what I want. This is the best I could find but they were designed with the center free space and the plates angling out.
Oh, if only my brother did not throw out my copy of the Audio Encyclopedia.
An externally hosted image should be here but it was not working when we last tested it.
Oh, if only my brother did not throw out my copy of the Audio Encyclopedia.
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A long time ago, at a public library in the city where I lived as a boy, I found a dusty book on loudspeakers, written by Gilbert Briggs, the founder of the British company Wharefedale Wireless Works. I forget exactly what year the book was written in - it might have been mid 1930s, maybe as late as mid 1940s, but almost certainly not later than that.
The book mentioned the brand-new idea of "stereo" and the brand new stereo-related patents by Alan Blumlein, which also suggests it was written mid 1930s to maybe 1940. (Briggs wasn't terribly impressed by stereo, and contended that "double mono" - two speakers a distance apart, driven by the same identical electrical signal - were almost as good. Nobody else at Wharfedale agreed, though!)
So why am I bringing up this ancient book from almost the dawn of the modern moving-coil loudspeaker era? Because one of the photos in the book showed a technique Briggs had invented to reduce the problem of treble beaming from his speakers.
And what was Brigg's invention? A slightly simplified version of the second photo Printer2 just posted: speaker pointed straight up at the ceiling, and a conical reflector (straight-sided in Briggs case, not parabolic) positioned just above the speaker, point down, coaxial with the speaker, to reflect treble in all directions!
I do not know if Briggs was the first person to come up with this idea - but at the least, we know that Briggs invented it before WWII ended, and most probably even before WWII started.
I also do not know if Briggs idea was picked up and re-used by others after his book was published. It seems quite likely that this may have happened, though.
Finally, I do not know if Stevie Ray Vaughan, in between bouts of substance abuse in which he variously sniffed, snorted, swallowed, injected, or gulped cannabis, methamphetamines, Quaaludes, cocaine, and whisky, actually collected together enough functioning brain cells to re-invent Briggs treble diffuser cone, or whether perhaps he simply remembered having seen the idea in use somewhere before.
Let's leave Stevie in the Happy Snorting Grounds, and come back to Brigg's invention. I was nutty about Hi-Fi as a boy, and having read Briggs book, I immediately tried out his cone diffuser idea with with a full-range speaker of my own. What I found was that it drastically messed up the tonal balance of the speaker, making the treble much weaker (because it was now being scattered in every direction instead of beamed at your ear!)
Also, with the straight-sided cone, the original tight treble beam bounced off the cone and remained tightly beamed in the vertical direction - if you moved your head up or down from the sweet spot, the treble fell off drastically. Presumably this is why the later invention of the flared cone shown in Printer2's pics occurred.
So it seems beam-blockers / diffusers have had a long, and frequently unsuccessful, history.
In Hi-Fi, we all know what the cure for a lack of treble dispersion was: using a small tweeter for treble, instead of a honking big "full range" speaker.
Electric guitar amps, meantime, remain in the dark ages when it comes to acoustic design. Bass guitar amps now often do have tweeters; so do acoustic guitar amps; but electric guitar amps continue to use 10", 12", or worse, multiple 10" or 12" drivers spaced widely apart. Our electric guitar amps are still stuck in 1945, or maybe it is 1935.
Okay, we need a tweeter. Electric guitars don't have much output above 5 kHz, if that. So we don't need a 1" tweeter of the sort used to get to 20 kHz in Hi-Fi. Most likely, a suitably designed 3" or 4" cone driver would be about right for an electric guitar "tweeter".
Add a proper crossover network, and treble beaming problems would be a thing of the past.
There is a catch or two: One, that small driver has to have sensitivity similar to the guitar speaker, and that may be hard to find. Two, you will have to add lowpass filtering to keep the small driver from spitting out harsh and nasty sounds above 4 or 5 kHz - the big 12" guitar speaker does this automatically because it's too heavy and slow to work well at 5 kHz, but this won't be true for the smaller, lighter, nimbler 3" or 4" we're using to solve the treble beaming problem.
Three - and this is a big one - the crossover network designs and theory you find in every modern Hi-Fi speaker design book will not work in a valve guitar amp. Those crossovers networks are designed to work with an amp that has an extremely low output impedance (a tiny fraction of an ohm). Valve guitar amps, on the other hand, have output impedances of at least several ohms, and in some cases, several tens of ohms.
So someone needs to come up with a crossover network that will work with a guitar amp, with its high output impedance.
I have a promising lead: I think a series crossover network will work even with an amp with high output impedance, unlike the traditional parallel crossover network.
If you've never heard of series crossover networks, Rod Elliott has a nice write-up about them: Series vs. Parallel Crossover Networks
So there you go - solve beaming in your guitar amp the same way it was done, many decades ago, in the Hi-Fi world. 🙂
The catch being, nobody seems to have done this for electric guitar yet, so it remains a research project.
I have taken a few steps in the right direction: two guitar amps I built recently use small speakers (about 6.5"), which beam much less than traditional 10" and 12" speakers. I added electronic filtering to keep out the unwanted high frequencies above 5 kHz. It works - but SPL levels are limited, and so far, I've only used these with solid-state power amps driving them. No valves yet.
-Gnobuddy
I just want to put up a beam-blocker idea, that I find helpful on my V30's. Its a 5" to 6" disk in front of the speaker, with
2.5" diameter hole in it. The disc blocks the treble beam and the hole releases it as a point source, letting it spread out evenly. Test it with piece of cardboard!
2.5" diameter hole in it. The disc blocks the treble beam and the hole releases it as a point source, letting it spread out evenly. Test it with piece of cardboard!
i did the same here, lots of fun to experiment with.
its basically a modded shelf. ignore the polycarbonate in front of the cardboard- its only for testing purpose atm because i had it at hand and was interested in the sound.
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Gnobuddy: The first edition of 'Loudspeakers' by G.A. Briggs was issued in May 1948. Your description of Mr. Brigg's design for an omni-directional column speaker is spot on.
Thanks for pointing out the fact that, although smaller diameter drivers would beam less than 12" drivers, they would also produce unwanted frequencies above 5kHz.
Regarding the use of a 'low/mid' driver combination. The presence of a crossover network may hinder the desired 'direct musical communication' between the amp and the speaker cab.
I agree that a series crossover component circuit may be the preferred choice, but it would be desireable to keep it as simple as possible.
Lots to investigate here, hope your research bears fruit.
Thanks for pointing out the fact that, although smaller diameter drivers would beam less than 12" drivers, they would also produce unwanted frequencies above 5kHz.
Regarding the use of a 'low/mid' driver combination. The presence of a crossover network may hinder the desired 'direct musical communication' between the amp and the speaker cab.
I agree that a series crossover component circuit may be the preferred choice, but it would be desireable to keep it as simple as possible.
Lots to investigate here, hope your research bears fruit.
And please never forget the huge difference between guitar amps and hifi amps. Hifi amps and speakers are designed to faithfully reproduce sound. Not add color. Guitar amps are designed to have unique tone, they are intended to be part of the sound creation. That is why one player plays a Fender, and another plays a Marshall. One guy likes Celestion speakers, another likes Eminence.
My experience is that beam blockers work well. They prevent the poor table in front of the guitarplayer having their ears blown off.
My experience is that beam blockers work well. They prevent the poor table in front of the guitarplayer having their ears blown off.
Seems to sound like it. Being a woodworking kind of guy I would make a beam blocker type of plug out of wood to put behind the grill cloth. Another day though, far down on my list of need to do items.
That was exactly my impression -- a [relatively] large circle with a [relatively] small hole cut in the center.
That means you have two variables to work with in your experimentation; a.) The size of the circle and, b.) The size of the hole in the middle. The sizes you ultimately select for each depends on your style of playing, what you play, and the overall sound you're looking for.
You could start with pieces of cardboard and work your way into something more permanent (just like Printer2 mentioned about wood working).
Best of Luck!
Dave
does it spread the sound horizontally or vertically? and why?
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and does the below model work good??
i think i can test it with putting my cab upward and with stacking the circular cone above.
Oh you really want this don't you? The acoustic lense is suppose to spread the sound at the angle of the notch cut out in the fins. The fins delay the sound leaving the lense, it causes the wave to leave in a arch pattern, think of the smallest part as a point source. It usually is fed by a horn that produces a fairly directional wavefront, how it will work with a speaker I can't say.
The bottom one I doubt that you would want to spread out the sound 360 degrees. But you can get an idea on what it could do. Just a big beam blocker or a Leslie speaker that is not spinning.
The bottom one I doubt that you would want to spread out the sound 360 degrees. But you can get an idea on what it could do. Just a big beam blocker or a Leslie speaker that is not spinning.
Thank you!
Keep in mind this is rather easily solved. There are plenty of DI boxes available for feeding guitar to a P.A. system. The P.A. system is designed to produce frequencies much higher than 5 kHz, so every D.I. box includes high frequency filtering to take out guitar harshness above 4 or 5 kHz.
Looking at a few guitar speaker frequency responses, the treble usually falls off with a 4th order (24 dB/octave) at the high frequency end, usually starting somewhere around 3 kHz. If we were to use a small speaker with a wider treble response, we could recreate this treble rolloff with two inductors and two capacitors. Because the frequency is pretty high, the inductors needed are fairly small, and need not be bulky or expensive.
It is much simpler to make an active filter before the signal ever gets to the power amp, which is what I did in my experiments using solid state amps. But there is a catch: if you overdrive the power amp (which we usually want to do with a valve guitar amp), then the power amp itself generates more of those harsh frequencies above 5 kHz. So we have to filter those out between power amp and speaker - meaning it has to be a passive filter, old fashioned inductors and capacitors.
Penny-pinching former accountant Leonidas Fender would never have spent an extra dollar on inductors if he could help it. Multiply that dollar by the thousands of amps he sold each year, and it adds up to a lot of lost money for him. But we DIY types don't have the same problem, so we don't have to be quite as tight-fisted with our parts costs.
Not at all - we have plenty of evidence to the contrary. Every good Hi-Fi speaker on planet earth uses a crossover network. Hi-Fi is a much more critical application - a speaker has to be much more accurate for Hi-Fi. So we have the demonstrated fact that a good crossover network and the use of multiple drivers makes a speaker better, not worse - certainly it doesn't hinder the communication between the amp and the speaker!
As an aside, what does "hinder the communication" actually mean, anyway? Electricity is pretty simple - we have voltage, current, resistance, inductance and capacitance. Nothing else. You can't change the communication between amp and speaker without also changing the voltage across the speaker - which we can measure with a simple frequency response plot. If there were some mysterious process hindering the communication, we would immediately know about it, simply by measuring before and after frequency responses. (In the case of a crossover network, we would measure the summed outputs of the "woofer" and "tweeter" after the crossover network, which is a routine part of all crossover network design by any reputable company.)
Agreed, but we would have to find out what is needed by experiment. It might turn out that a simple first or second order crossover might do the trick, which would be nice.
Probably the crossover frequency would be pretty low compared to Hi-Fi - maybe around 1 kHz or so - which is above almost all the fundamental frequencies you get from the typical 21 or 22 fret guitar. (1st string, 22nd fret high D is 1.17466 kHz.)
Agree, and thanks!
-Gnobuddy
You have pinholes scattered over the entire area of the speaker cone. While any individual pinhole would produce good treble dispersion, the effect of summing all the pinholes spread over the entire face of the speaker is bad: you are back to very poor treble dispersion!
This is the same problem that affects side-by-side speaker layouts. Any time the speaker has a large horizontal dimension, you get very poor treble dispersion in the horizontal direction.
So if you want good horizontal dispersion from your speaker, try a single vertical slot in the middle of the speaker (rather than a circular array of pinholes.) The slot can be the full 8" or 10" tall, but keep it to no more than an inch or two wide.
I tried stuff like this many years ago, and was always disappointed by the results. In the end, I found the old truism to be true - you can't make a silk purse from a sow's ear. (And you can't make a good speaker starting with a bad one; and when it comes to treble dispersion, all guitar speakers are bad ones!)
-Gnobuddy
Yes indeed.
My ones comprise of a circular plastic pot lid, with hole, mounted on a thin metal strip across the speaker, so its sandwiched between speaker and baffle, held by two of the speaker screws. All sprayed flat black. The metal strip has 'U' shaped bends at the edge of the cone so the cone can never touch it even on large outward movements.
Another hidden version would be a thin sheet material lightly stitched inside the grill cloth with matching thread.
Test versions can be whatever, hanging in front on strings.
One other thing these beam- blockers do affect is mic placement, which gets trickier to find the right spot.