Thanks for that link!
The cab design is very interesting, and the description of its working is plausible because it's based on actual science. And the inventor / manufacturer is one of those rare technical people who is also a charismatic and effective communicator. The BBC should hire him to host technical documentaries, he's that good!
In my experience, speaker boxes with non-parallel walls do tend to sound much more neutral and much less "boxy" than the usual brick-shape (or "right rectangular prism", as a mathematician would call it.) While this is always a good thing for Hi-Fi, there seem to be some guitarists who use the boxy tone of the usual guitar cab as part of their sound. Those guitarists might not like the more neutral sound of the Barefaced cab as much.
IMO the only questionable part of the video is the loudness comparison with the Victory cab. Unless you have exactly the same driver (speaker) in both cabs, you really can't make valid conclusions as to one cab design being louder than the other. The Barefaced might be louder only because it happens to contain a more efficient driver, or it might be louder because of better acoustic design. We don't know which.
-Gnobuddy
The cab design is very interesting, and the description of its working is plausible because it's based on actual science. And the inventor / manufacturer is one of those rare technical people who is also a charismatic and effective communicator. The BBC should hire him to host technical documentaries, he's that good!
In my experience, speaker boxes with non-parallel walls do tend to sound much more neutral and much less "boxy" than the usual brick-shape (or "right rectangular prism", as a mathematician would call it.) While this is always a good thing for Hi-Fi, there seem to be some guitarists who use the boxy tone of the usual guitar cab as part of their sound. Those guitarists might not like the more neutral sound of the Barefaced cab as much.
IMO the only questionable part of the video is the loudness comparison with the Victory cab. Unless you have exactly the same driver (speaker) in both cabs, you really can't make valid conclusions as to one cab design being louder than the other. The Barefaced might be louder only because it happens to contain a more efficient driver, or it might be louder because of better acoustic design. We don't know which.
-Gnobuddy
Yeah, I agree & it's so simple it's worth trying to DIY, seen the graphic here?:
Barefaced Upsetter 110
– Barefaced Audio
Might be louder because the their vent is in effect a conical horn, at the frequencies you're gonna notice it most.
Tried to reverse engineer it, but Celestion haven't published complete specs for the G10 Vintage. I don't think the exact numbers would matter much though...
Barefaced Upsetter 110
– Barefaced Audio
Might be louder because the their vent is in effect a conical horn, at the frequencies you're gonna notice it most.
Tried to reverse engineer it, but Celestion haven't published complete specs for the G10 Vintage. I don't think the exact numbers would matter much though...
It might, and that's certainly what the manufacturer claims. I'd love to hear a comparison and SPL measurements with a conventional cab of similar size using the same speaker in both cabs. That would tell the truth, one way or the other.
I expect the "horn" dimensions are not critical, as you say. I suspect the tuning frequency of the slot does matter, though. It will depend on the width of the opening between the two angled vanes, and the volume of the air-chamber in front of it
You could probably get reasonably close by guesstimating the thickness of the wood used in the angled panels, and comparing that with the width of the slot in the photographs and images of the CAD model. If the wood is 3/4 inches thick and the slot is, say, two times as wide as the wood thickness, you know the slot is about 1 1/2" wide...
From what I've seen elsewhere, those meaty 4x12 Marshall cabs are usually tuned to have a bass peak at roughly 100 Hz. With some fiddling, it should be possible to try to tune your reverse-engineered cab to about this frequency.
A cheap electret microphone (One buck at Sparkfun: Electret Microphone - COM-08635 - SparkFun Electronics ) and free Room Eq Wizard software might be all it takes. Temporarily hot-glue the angled vanes into place, move them if necessary to tune to 100 Hz, then glue with wood glue and/or screws.
Interestingly, the back of the 2x10 and 2x12 cabs shows a separate bass-reflex port, in addition to the diffraction slot with its crude horn. This would make it easier to separately optimize the midrange boost from the horn, and the bass boost from the port.
-Gnobuddy
Attachments
Well thank you very much!
I'm just getting rolling with some Barefaced YouTube content and having been banging my head against confusing video editing software for the last few days it's nice to hear good reasons to keep battling the technology!This is a very good point - I can't remember if it was edited out of the video but the Barefaced Reformer 112 has a Celestion Vintage 30, which is the exact same driver as the pair of drivers in the Victory 212. I was SHOCKED at the loudness difference there in the room and very pleased it came across so well on mic when I saw the edit a few days later. I later had an impedance related panic and asked Rob if he'd used the wrong output transformer tap for the 212 (16 ohms) and he's insistent he didn't because he uses that head and cab pairing all the time, so the 112 and 212 should have been receiving equal power.
You're very welcome. Well deserved, I would say!Well thank you very much!
Seriously, if you ever get the urge to be an educator / presenter, I think you may find you're a natural at it. I suspect there would be plenty of schools in the UK who would welcome someone like you to talk to those of their students interested in science, technology, and entrepreneurship.
I don't suppose you have a lot of free time, though, as I'm sure running Barefaced keeps you very busy!
Thanks for clearing that up, and my apologies if that information was on the video and I missed it. I'm quite shocked as well - that was a heck of a lot more than the maybe 3 dB difference I'd been expecting! It must be the magic of that midrange horn!
-Gnobuddy
Actually one of the challenges with this is to avoid noticeable horn loading because of how it messes with the tone - if it behaves like a horn there's a low pass filter effect and there tend to be horn-related distortions in the midrange. Also any loading on the driver will affect the tone out the front, especially if it's increasing the radiation impedance on the back of the cone significantly in the midrange, reducing the cone excursion and thus direct radiating output at those frequencies.
The slot dimensions are critical because if the slot becomes too narrow the AVD starts to behave like a rear-horn, and the large coupling chamber volume means that you get an acoustic low pass filter coming in from the upper bass / lower midrange region, which basically kills the mid and treble rear output.
The bass reflex port is used to adjust the tuning frequency of the enclosure, so it's working in parallel with the air mass / air spring element of the AVD.
So the true innovation in this is that one apparatus is simultaneously allowing reasonably high fidelity dipole mid/high operation from a front firing woofer and monopole bass reflex behaviour.
You have a perfectly good point as far as ear-damaging SPL from guitars goes.
But can you imagine trying to build a business selling less-efficient loudspeakers? It would be like trying to sell sports cars with the slogan "Less horsepower than the competition. We are proudly slower than everyone else!" That would fly as well as the proverbial lead zeppelin.
If history is any indication, the reality seems to be that, no matter how stupidly loud a guitar amp/speaker is, there will always be guitarists who want it even louder. Any number of now half-deaf guitarists from the age of arena rock will confirm that.
For people like you and me, who want less SPL, the Barefaced cabs still have the enormous advantage of having a much bigger sweet spot. We can always turn down the SPL with a speaker attenuator, power scaling, or a custom low-watt amp.
-Gnobuddy
Actually a cheap Radioshack SPL meter would have done more for me rather than waving a mike around the room. An AB box with the two speaker cabs in the same place, a near field mike so you could actually hear what either speaker actually sounds like rather than a far field mush of a sound. A cab at ear level right beside the person playing will sound much louder than the one two to three times the distance.
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It's not making it any louder on-axis, it's just improving the power response by using the rearward output to provide lots of well dispersed output. So you don't have to turn up as loud to hear yourself and you don't end up with a huge spike in output when you're in the line of fire but struggle to hear it when you're off to the side.
Makes everything easier!
Am I thinking that you're missing the point of the demonstration? What use is an SPL meter with someone playing guitar? How does a near field mic show what a cab sounds like at the true listening position?
And obviously a cab close by at ear level will sound louder due to the inverse square law and the directionality of guitar speakers - can you tell me the last time you saw a guitarist with a speaker at ear level?!!
A beam blocker does not do the same thing, not even close! I'd have thought that would be obvious from both mechanisms, if you understand acoustics?
You are missing the point. Have you seen the Youtube vids about getting free energy from a couple of speaker magnets?
Actually I found the sound from your microphone sounded like crap with any speaker being used. But the real reason is that we could compare your peaker to another known quantity under the same conditions. The mic could be four or five feet in front of the speakers, with an A/B switch we could really compare the loudness of them. Youtube does compress the audio in the vids. How do I really know what is going on? While they may raise the level one one as compared to the other with an A/B box at least we would get a better representation than not having the speakers played side by side.
Actually in the vid where you are waving the mic around. No wonder what's his name feels the cabinet on the next sofa cushion sounds much louder than the speaker on the floor. As far as what horns can do and how they work, I messed around with them thirty-five odd years ago. I am sure the guys in the horn building community here in the hifi section might find your cabinet of interest. Not so much about it being used in their application, just that they may know more about what is going on than the present company.
THE CABINET ON THE SOFA IS NOT PLUGGED IN!!!
Sorry but I felt that point was worth shouting. The cabs being compared are underneath the amp, in the exact same position.
Duh...
If you think a single driver monopole with a beam blocker can have comparable power response to a dipole system with a diffracting waveguide on the rear, then I suggest you head over here and start reading:
Linkwitz Lab - Loudspeaker Design
No need to yell, I was polite with my misunderstanding. I thought the whole point was to show off the little cabinet, why bother with it otherwise? I still do not see much value in your waving your microphone around when you have one near field that I guess was there for looks. My comments still stand, an A/B pedal with comparable speakers in each cabinet would have been my way to go showing off my technology if I wanted to be taken seriously.
Linkwitz Lab - Loudspeaker Design
Are we to wade through the whole site? If you do not have the interest in making your point what makes you think we want to spend the time sifting through the site to make it for you?