2 x 210s: Vertical or horizontal stacking?

[JTUK]

[quote name='Marvin' post='1316190' date='Jul 25 2011, 08:16 PM']I think it's more a matter of cost. To make a box like that of Bill's design is probably not cost effective for mass production. I've had a stab at it (my wood work wasn't up to scratch) and a good friend of mine on here has made one. The actual making of the 'box' is quite involved.

Are they better boxes? Well, my friend built a Jack12 and he said it blew the arse off his 4x10. The cabinet design was that efficient. I have no personal experience though.

Why don't we get 4x10's stacked vertically? Probably because as consumers we are very conservative and would rather it looked nice rather than worked effectively.

Major manufacturers would loose a lot of margin to make cabs like the designs of Bill and Alex.

One may like to compare the whole issue to when James Dyson was getting nowhere with his 'cyclone' vacuum cleaner. Now everyone makes one.[/quote]


Or....the marketing and suchlike is poor...?? If companies can't get presentation right, then you might wonder about the credence of the rest of the stuff.

[LawrenceH]

[quote name='ficelles' post='1316280' date='Jul 25 2011, 09:11 PM']I sense a beam blocker discussion approaching...

ficelles[/quote]

Oh dear, I hope not! Because they clearly don't work as designed...

Mr Foxen, what I mean is that the problem of the guitarist not hearing himself is more down to the fundamental limitations/directivity of a single large diameter speaker than the comb filtering effect from stacks. Even if your stack is set vertically the sound will be highly directive just due to the speaker. Btw vertical stacks will still comb filter, just in one plane - but audience members at different heights will get just as different a sound as those in different positions around a horizontal stack. Vertical stacking is not an ideal solution and in, say, theatres or any gigs with balconies then it will actually be more problematic.
Bill makes a very fair point that guitar stacks are overkill and a single speaker would do the job, though personally I think they like them not just for the look but the nearfield sound on stage (very full, bass-heavy and a PITA to mix). You just don't get that with a 1x12".

[Bill Fitzmaurice]

[quote name='LawrenceH' post='1316303' date='Jul 25 2011, 04:23 PM']I think they like them not just for the look but the nearfield sound on stage (very full, bass-heavy and a PITA to mix). You just don't get that with a 1x12".[/quote]More than a few top acts don't have any amps on stage at all. They still have them, backstage. They hear what the audience hears, the PA feed, though both monitors and in-ears. 'Journey' adopted this arrangement at least 12 years ago. Geddy Lee is probably the most obvious proponent. Chicken, anyone?

[LawrenceH]

[quote name='Bill Fitzmaurice' post='1316341' date='Jul 25 2011, 09:36 PM']More than a few top acts don't have any amps on stage at all. They still have them, backstage. They hear what the audience hears, the PA feed, though both monitors and in-ears. 'Journey' adopted this arrangement at least 12 years ago. Geddy Lee is probably the most obvious proponent. Chicken, anyone?[/quote]

Yes and it'll become more and more common for larger acts I think - you need bloody awesome monitoring to pull it off though, way beyond what's 'average' in the UK and it still doesn't sound the same on stage. One functions band I used to do sound for went down this route, but in the end they were never satisfied with the stage sound and regressed back to big amps (sigh)! I suppose those same limitations inherent in a big stack also contribute to a unique stage sound.

[LawrenceH]

[quote name='Bill Fitzmaurice' post='1316285' date='Jul 25 2011, 09:15 PM']It works, but isn't at all a new or novel idea. Earl Geddes has been using foam for quite some time, and without a hole in the middle, as that's not what makes it work. The underlying principle is diffraction; a thirty year old example is the JBL 2301 perforated plate horn lens.
[url="http://www.jblpro.com/pub/obsolete/acoustic_lens_family1.pdf"]http://www.jblpro.com/pub/obsolete/acoustic_lens_family1.pdf[/url]

Beam blockers use the same principle.[/quote]

I didn't claim it was new or novel - just that it works and is quite neat - that one happens to be a good cheap implementation.

But in that design the hole in the middle IS what makes it work, otherwise you just attenuate the sound without modifying directivity. The foam with hole is just an HF absorber to reduce effective cone diameter. Some of the designs use different density foams to alter the speed of sound through the material at different points to make a waveguide but that's not what's going on here.

EDIT - oh yeah and a standard beam blocker doesn't use the same principle at all as it doesn't work, at 'blocking' the beam that is

Edited July 25, 2011 by LawrenceH

[Bill Fitzmaurice]

[quote]But in that design the hole in the middle IS what makes it work[/quote]Not if you do it right, which is with varying foam thickness across the cone. See the Geddes model. [quote]otherwise you just attenuate the sound without modifying directivity.[/quote]The amount of attenuation offered by 3/4 inch of foam is infinitesimal. The diffraction is fairly significant at the shortest wavelengths, enough to cause them to literally bounce off the walls of the foam's individual cells, redirecting their paths, while longer wavelengths pass though unimpeded.

Edited July 25, 2011 by Bill Fitzmaurice

[Marvin]

[quote name='JTUK' post='1316302' date='Jul 25 2011, 09:23 PM']Or....the marketing and suchlike is poor...?? If companies can't get presentation right, then you might wonder about the credence of the rest of the stuff.[/quote]


I'm afraid you just sound like you're on a wind up.

Bill is never going to compete against ready built cabs, they are after all self builds.

And, as Bill has already pointed out, Alex builds cabs that the majors can't as there isn't the margin in it for them. I don't see anything wrong with Alex's presentation and the vast majority of the people who have bought his cabs really rate them.

But you're right, if it ain't broke why fix it? Unless of course it never worked to start off with.

[LawrenceH]

[quote name='Bill Fitzmaurice' post='1316393' date='Jul 25 2011, 10:11 PM']Not if you do it right, which is with varying foam thickness across the cone. See the Geddes model. The amount of attenuation offered by 3/4 inch of foam is infinitesimal. The diffraction is fairly significant at the shortest wavelengths, enough to cause them to literally bounce off the walls of the foam's individual cells, redirecting their paths, while longer wavelengths pass though unimpeded.[/quote]

Sigh...but the Geddes model is considerably more expensive to implement. For all intents and purposes in the frequencies where guitars output this model works by attenuation, and 3/4" of the right stuff is enough to make a worthwhile (ie audible) difference that can be confirmed by measurement directivity plots without creating a bloody great waveguide that adds volume to the cabinet. The main drawback is an overall loss of sensitivity in the HF but you gain a less uneven dispersion pattern. By contrast a 'beam blocker' creates a more complex pattern that when you measure it is all jagged and unven. Doesn't really go towards solving the problem so much as shift it about.

You do like to be difficult sometimes Bill!

[Bill Fitzmaurice]

[quote name='LawrenceH' post='1316415' date='Jul 25 2011, 05:21 PM']Sigh...but the Geddes model is considerably more expensive to implement. For all intents and purposes in the frequencies where guitars output this model works by attenuation, and 3/4" of the right stuff is enough to make a worthwhile (ie audible) difference that can be confirmed by measurement directivity plots without creating a bloody great waveguide that adds volume to the cabinet. The main drawback is an overall loss of sensitivity in the HF but you gain a less uneven dispersion pattern. By contrast a 'beam blocker' creates a more complex pattern that when you measure it is all jagged and unven. Doesn't really go towards solving the problem so much as shift it about.

You do like to be difficult sometimes Bill! [/quote]I think you'd find adding a beam blocker to the hole in that foam thingamajig would get a better result than either alone. The blocker probably works better than the foam if sized properly. I doubt that Weber ever did a thorough study of different sizes and shapes. I might someday if I have nothing else to do, it would only take an hour or so to map polars with different size blockers in different positions.

[LawrenceH]

[quote name='Bill Fitzmaurice' post='1316462' date='Jul 25 2011, 11:22 PM']I think you'd find adding a beam blocker to the hole in that foam thingamajig would get a better result than either alone. The blocker probably works better than the foam if sized properly. I doubt that Weber ever did a thorough study of different sizes and shapes. I might someday if I have nothing else to do, it would only take an hour or so to map polars with different size blockers in different positions.[/quote]

Careful, or you'll reinvent the phase plug With flat reflective blockers though you'll create a horrible mess of variable HF path lengths. With a theoretical totally absorptive round flat blocker you will create a ring-shaped aperture which will give quite a strange diffraction pattern at high frequency but do very little other than a small reduction in volume in the mids and lower.
In the context of the foam donut thing, the opposite edges of the loudspeaker cone are no different to two smaller spaced drivers, with the same solution presenting itself ie get them closer together.

Edited July 25, 2011 by LawrenceH

[Bill Fitzmaurice]

[quote name='LawrenceH' post='1316491' date='Jul 25 2011, 06:53 PM']Careful, or you'll reinvent the phase plug[/quote]
I already have, they're used in the current versions of the OTop and Jack speakers and in the midrange horn of the Omni series. A phase plug is just another example of a diffraction device.

Edited July 26, 2011 by Bill Fitzmaurice

[JTUK]

[quote name='Marvin' post='1316399' date='Jul 25 2011, 10:14 PM']

I'm afraid you just sound like you're on a wind up.

Bill is never going to compete against ready built cabs, they are after all self builds.

And, as Bill has already pointed out, Alex builds cabs that the majors can't as there isn't the margin in it for them. I don't see anything wrong with Alex's presentation and the vast majority of the people who have bought his cabs really rate them.

But you're right, if it ain't broke why fix it? Unless of course it never worked to start off with.[/quote]


No.. it is just..and I've seen this in another thread..that certain people are trying to convince you they have invented the wheel which considering some of the people they are up against was laughable in that particular thread, but there you go.
What I am saying here is, .. if the build is poor, ( conjecture ) the website is even worse, then why on earth would you jump straight out and assume everything else is just wunnnerful..??

So what we have is a couple of protaganists here who are largely ignored or unknown by the rest of the industry.
When you start seeing independant reviews posted ..as opposed to someone who wants to 'review' his latest buy, to a lot of other 'fans', and when you start seeing these sold commercially and in pretty visable places then you might get past forum hype.

[ShergoldSnickers]

[quote name='JTUK' post='1316568' date='Jul 26 2011, 07:44 AM']So what we have is a couple of protaganists here who are largely ignored or unknown by the rest of the industry.
When you start seeing independant reviews posted ..as opposed to someone who wants to 'review' his latest buy, to a lot of other 'fans', and when you start seeing these sold commercially and in pretty visable places then you might get past forum hype.[/quote]
You probably never will see these cabs widely advertised or highly visibly sold, as the mass market isn't where they are targeted. BFM is after self-build, a minor sub-set of bass players, and Alex has neither the time or capacity to manufacture at scale. They are niche products. There are thousands of niche products out there that earn their manufacturers a living, the mass market is not necessarily the place to be. Numbers sold tell you absolutely nothing about the quality, only where a product is on it's design/life cycle at the very best, and only then in comparison with its own historical data.

It's more to do with what other manufacturers don't do, than what BFM or Alex have 'invented' and put in. There is no new wheel, the theory and methods are already out there - they've just been ignored by most manufacturers, due to cost, laziness, manufacturing complexity etc.

Alex does at least have a trial period whereby if you are not satisfied, you can return the cab and get your money back minus carriage costs. Speaks volumes to me. If I've been had, then Alex is far cleverer than I'd imagined, and would be a risky strategy on his part given the scrutiny his claims have already had, and the number of apparently trustworthy ears that have bent his way and been positive.

Having said all that, criticism is good – it may get people who are thinking of buying a cab to do more research, to take their time and try a few extra cabs. Always a good thing.

[xgsjx]

A few manufacturers are stepping away from (or avoiding) the "4x10 & a 15 is the best" regime & building vertical stacking cabs. TC E & Genz Benz are 2 that instantly come to mind & EBS do a vertical array 4x12.

[stevie]

[quote name='Marvin' post='1316071' date='Jul 25 2011, 06:41 PM']Most mass manufactured cabs are simply constructed boxes with drivers in them with little or no acoustic engineering involved in it's design.[/quote]
Most commercial bass cabs I've seen are reasonably well designed. I agree that there is a tendency to cut corners to get the price down. It has to be said, however, that very little acoustic engineering is actually required to knock together a bass guitar cab. The real engineering has been done by the driver manufacturer. This is why anybody who can use a saw and and screw together a simple box can build one and it will work. The hardest part is getting the box to look pro.

[stevie]

[quote name='Bill Fitzmaurice' post='1316462' date='Jul 25 2011, 11:22 PM']I think you'd find adding a beam blocker to the hole in that foam thingamajig would get a better result than either alone.[/quote]
The hole in the foam is an integral part of the design. If you block it up with a beam blocker it won't work properly. Have you read the description?

[stevie]

[quote name='LawrenceH' post='1316247' date='Jul 25 2011, 08:56 PM']but a neater solution (IMO) is Jay Mitchell's 'foam donut'
[url="http://www.stratopastor.org.uk/strato/amps/prii/speaker/foamdonut/foamdonut.html"]http://www.stratopastor.org.uk/strato/amps.../foamdonut.html[/url][/quote]
I've never seen that before, but it's very clever. And it's properly documented with measurements. Excellent.

[Mr. Foxen]

[quote name='stevie' post='1316888' date='Jul 26 2011, 12:24 PM']The hole in the foam is an integral part of the design. If you block it up with a beam blocker it won't work properly. Have you read the description?[/quote]

Think the point is it doesn't work the way you think it works.

[stevie]

[quote name='Mr. Foxen' post='1316899' date='Jul 26 2011, 12:31 PM']Think the point is it doesn't work the way you think it works.[/quote]
It's quite clear how it works. There's a link on the page Lawrence gave that takes you straight to the designer's description. Blocking up the hole is nonsense.

[Mr. Foxen]

I've already read it, and the dissection of it with various engineers, including BFM. Just because something works doesn't mean that the explanation of why it works is true.

[stevie]

OK then. Please enlighten us and explain why blocking off the hole would help.

[Bill Fitzmaurice]

[quote name='ShergoldSnickers' post='1316598' date='Jul 26 2011, 03:32 AM']It's more to do with what other manufacturers don't do, than what BFM or Alex have 'invented' and put in. There is no new wheel, the theory and methods are already out there - they've just been ignored by most manufacturers, due to cost, laziness, manufacturing complexity etc.[/quote]
+1. All Alex and I have done is to design our speakers using proper acoustical engineering principles that have been well known to the acoustical engineering community for decades. If there's a question to be posed it's why has the electric bass speaker manufacturing community in general ignored those principles from day one? Here's a hint: profits.

[ShergoldSnickers]

[quote name='Bill Fitzmaurice' post='1316393' date='Jul 25 2011, 10:11 PM']Not if you do it right, which is with varying foam thickness across the cone. See the Geddes model. The amount of attenuation offered by 3/4 inch of foam is infinitesimal. The diffraction is fairly significant at the shortest wavelengths, enough to cause them to literally bounce off the walls of the foam's individual cells, redirecting their paths, while longer wavelengths pass though unimpeded.[/quote]
Analogy?

Take a torch and a sheet of glass. Clear glass gives a focused beam from the torch, as the beam is relatively unaffected. Frost the glass however and you'll get scattering, widening the beam.

I'm guessing this is something like?

[Mr. Foxen]

[quote name='ShergoldSnickers' post='1317189' date='Jul 26 2011, 03:26 PM']Analogy?

Take a torch and a sheet of glass. Clear glass gives a focused beam from the torch, as the beam is relatively unaffected. Frost the glass however and you'll get scattering, widening the beam.

I'm guessing this is something like?[/quote]

Problem is, see the Dark Side of the Moon cover, different frequencies/colours scatter more than others.

[LawrenceH]

[quote name='Mr. Foxen' post='1316945' date='Jul 26 2011, 01:00 PM']I've already read it, and the dissection of it with various engineers, including BFM. Just because something works doesn't mean that the explanation of why it works is true.[/quote]

Wave transmission through an aperture at different wavelengths relative to the aperture width is secondary school physics, and pretty easy to visualise graphically. The problem in description is not in the foam donut but on the misconception where circular beam blockers are described as 'blocking' a 'beam' from the cone, when there is no such beam but instead a central point of symmetry where wave summation is maximally coherent. They actually 'work' by reflecting and as BFM has said diffracting the sound waves.
The acoustic foam certainly does attenuate at higher frequencies as illustrated by the NRC for good quality 1/2" to 3/4" foam, and a model based on simple absorption predicts well what is observed in practice. The hole is entirely necessary - covering the whole speaker in a uniform layer of foam would do nothing to alter directivity, it would merely attenuate the overall output.
Graded density foam can be used to act as a waveguide but that is relying on wave propagation through the foam and far greater thicknesses are required, ie a stuffed horn, to give sufficient distance for the induced delay to alter directivity appreciably. This however is a refractive effect - as explained on one of Geddes' own patents for a stuffed waveguide. Foam stuffing is also used to absorb sound in waveguides/horns, which [i]corrects[/i] for [i]problems[/i] introduced by diffraction. It is not a diffractive effect in its own right.