2 x 210s: Vertical or horizontal stacking?

[Bill Fitzmaurice]

[quote name='ShergoldSnickers' post='1317189' date='Jul 26 2011, 10:26 AM']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]
You can find a basic description of how diffraction works here, in section 1-5.
[url="http://www.jblpro.com/pub/manuals/pssdm_1.pdf"]http://www.jblpro.com/pub/manuals/pssdm_1.pdf[/url]

[quote]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.[/quote]Maybe. An alternative view is that the hole becomes the primary radiating plane for high frequencies, and as its diameter is small the dispersion is widened. The same mechanism is seen in slot loaded tweeters, which also make the slot narrow and high, for both wide horizontal dispersion and tight vertical pattern control. It's an easy enough theory to test, you just make a foam plate with a narrow high slot instead of a hole and measure it on both axis.

Edited July 26, 2011 by Bill Fitzmaurice

[Marvin]

[quote name='JTUK' post='1316568' date='Jul 26 2011, 07:44 AM']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.[/quote]

You seem to be trying to say that Bill and Alex are peddling snake oil, for want of a better analogy.

Neither one, to me, seems to be claiming to have reinvented the wheel. Rather that there are basic principles that are manifestly ignored by the bass cab building industry.

There are numerous examples in all industries where basic principles or best practice is ignored in favour of profit margin. Only when the consumer has become informed do manufacturers change. Most purchases will be made on the basis of brand with little or no thought as to the actual spec of a product.

'The industry' can ignore these so called protagonists as they have the marketing budgets to shout louder in order to maintain their profit margins. Just because you can't buy a Barefaced Cab in your local music store is pretty much irrelevant.

As an aside, but poignant I think, I've noticed that several major bass cab manufacturers have started to boldly place in their spec list that their cabs are made from baltic birch, and that this is a real selling point for them. Considering that most of these cabs are in excess of £500 to £600 I should hope they were made of Baltic Birch given that the wood would account for probably less than 5% of the final retail cost of the cab. I'm more sceptical about the claims made by manufacturers whose product is design within the parameters given to them by bean counters.

Edited July 26, 2011 by Marvin

[Lfalex v1.1]

[quote name='Marvin' post='1316190' date='Jul 25 2011, 08:16 PM']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.[/quote]

Two more practical reasons spring to mind;

1) Lower centre-of-gravity
2) a "square" 4x10 arguably fits in a car boot better, in spite of it being harder to handle than a line array would be.

[JTUK]

[quote name='Marvin' post='1317459' date='Jul 26 2011, 06:57 PM']You seem to be trying to say that Bill and Alex are peddling snake oil, for want of a better analogy.

Neither one, to me, seems to be claiming to have reinvented the wheel. Rather that there are basic principles that are manifestly ignored by the bass cab building industry.

There are numerous examples in all industries where basic principles or best practice is ignored in favour of profit margin. Only when the consumer has become informed do manufacturers change. Most purchases will be made on the basis of brand with little or no thought as to the actual spec of a product.

'The industry' can ignore these so called protagonists as they have the marketing budgets to shout louder in order to maintain their profit margins. Just because you can't buy a Barefaced Cab in your local music store is pretty much irrelevant.

As an aside, but poignant I think, I've noticed that several major bass cab manufacturers have started to boldly place in their spec list that their cabs are made from baltic birch, and that this is a real selling point for them. Considering that most of these cabs are in excess of £500 to £600 I should hope they were made of Baltic Birch given that the wood would account for probably less than 5% of the final retail cost of the cab. I'm more sceptical about the claims made by manufacturers whose product is design within the parameters given to them by bean counters.[/quote]


I'm saying that for every positive review that may be posted here, there are others who think otherwise.
Why they don't post as such, you would have to ask them. Maybe they don't want to cause any agro or whatever, but
certain names are championed and may be in good faith but it would be a mistake to think that everyone on here thinks they are that good.
If anyone..typically, a new poster, asks for cab advice they get the stock answer.

I'd suggest they did some searching and evaluate that for thermselves...but then that is the way I would go about it, maybe others just follow a party line or something.

[Marvin]

[quote name='JTUK' post='1317688' date='Jul 26 2011, 09:54 PM']If anyone..typically, a new poster, asks for cab advice they get the stock answer.[/quote]

Stock repsonse.

'.......I'd get yourself a MarkBass cab....'

[EdwardHimself]

[quote name='Marvin' post='1317700' date='Jul 26 2011, 10:02 PM']Stock repsonse.

'.......I'd get yourself a MarkBass cab....'[/quote]

They are light, and of course they have YELLOW SPEAKERS! After all, let's face it, for all this talk of audio-science, most people just go for whatever looks good. And markbass cabs do look good, even if they sound totally terrible (apparently). Having said that, i did stick mine on the side. That was more to save floor space in my room though. I've not done a direct comparison between the 2 "setups" but I think it sounds pretty good. Of course i've never tried a barefaced or bill fitzmaurice cab before so for all I know it might be totally rubbish.

Edited July 26, 2011 by EdwardHimself

[4 Strings]

I'm not so convinced mass producers of bass cabs are so bound by profit when it comes to varying cab design as they can charge so much anyway. Some Hartke cabs have certainly had unusual formats, but they don't last too long in the range. Not because of sound or margin but just look odd (even horrible - whatever that is) and so don't sell well. If I'm frank, many of BFM's cabs are pretty 'horrible' looking and wouldn't sell in sufficient quantities for mass production.

I'm dying to try one, and also a Barefaced too.

[LawrenceH]

[quote name='Bill Fitzmaurice' post='1317393' date='Jul 26 2011, 05:50 PM']Maybe. An alternative view is that the hole becomes the primary radiating plane for high frequencies, and as its diameter is small the dispersion is widened.[/quote]

But that's not an alternative view that is what was described in the original link and by me. Hence the existence of a hole is essential for the design.

[quote name='Bill Fitzmaurice' post='1317393' date='Jul 26 2011, 05:50 PM']The same mechanism is seen in slot loaded tweeters, which also make the slot narrow and high, for both wide horizontal dispersion and tight vertical pattern control. It's an easy enough theory to test, you just make a foam plate with a narrow high slot instead of a hole and measure it on both axis.[/quote]

Yes, I nearly wrote that before actually but thought that since a lot of slot tweeters are designed with horns/waveguides as well it confuses things. Anyhow a slot design is fine if you want narrow vertical distribution, but for the Beam of Death (which was why I brought up those foam things in the first place), I'd say it's better to have a more uniform dispersion to get it in the guitarist's ears!

[steve]

to get back to the OP's question, I used to have two of the same Hartke cabs, and stacked vertically. I don't know about dispersion in the crowd, but it was much easier to hear myself.

And I can vouch for Bills designs, I have two now superceded Omni 10.5s which always impressed me, and are now being brought back into active service

[LawrenceH]

[quote name='EdwardHimself' post='1317726' date='Jul 26 2011, 10:24 PM']but I think it sounds pretty good. Of course i've never tried a barefaced or bill fitzmaurice cab before so for all I know it might be totally rubbish.[/quote]

That's because it is, the B&C drivers used are very capable indeed and the cab I've seen inside used decent wood. Some people don't seem to like the character of the sound but that's neither here nor there really.

[stevie]

[quote name='Marvin' post='1317459' date='Jul 26 2011, 06:57 PM']You seem to be trying to say that Bill and Alex are peddling snake oil, for want of a better analogy.[/quote]
You're putting words into his mouth, Marvin. What he is saying IMO is that you should think for yourself and not be a sheep. Self-styled gurus are often not quite what they appear to be. To quote Socrates: To find yourself, think for yourself.

[EdwardHimself]

[quote name='LawrenceH' post='1317834' date='Jul 27 2011, 12:01 AM']That's because it is, the B&C drivers used are very capable indeed and the cab I've seen inside used decent wood. Some people don't seem to like the character of the sound but that's neither here nor there really.[/quote]

Oh well that's a relief. I like the sound of it anyway, i think it's very clean and hifi sounding.

[4 Strings]

Here's a photo of the tidal movement through a restriction from above.

Is this what the hole does (seems the opposite of the beam blocker)?

[Marvin]

[quote name='stevie' post='1318067' date='Jul 27 2011, 11:05 AM']You're putting words into his mouth, Marvin. What he is saying IMO is that you should think for yourself and not be a sheep. Self-styled gurus are often not quite what they appear to be. To quote Socrates: To find yourself, think for yourself.[/quote]

Are you suggesting I'm just a sheep? Questioning, asking why and thinking for myself is something I probably do too much. It takes me literally ages to commit to buy anything as I want to make sure I'm buying what I need at the price I can afford. For example, there are a series of reasons why I've got a Fender Rumble combo that included cost, size, features etc. For gigging and practice I tend to place it on a stand to tilt it back or elevate it so it's not just playing to my ankles. I compromised and bought what was best for me.

Unfortunately the detractors, of what is somewhat basic acoustic engineering, put up little in response apart from to say they're talking rubbish because no one else builds cabs like that.

[Mr. Foxen]

[quote name='4 Strings' post='1318340' date='Jul 27 2011, 03:08 PM']Here's a photo of the tidal movement through a restriction from above.

Is this what the hole does (seems the opposite of the beam blocker)?[/quote]

The foam is transparent to big waves, and makes much more mess, because small waves get through, but later or in a different direction and they bounce around the cells in the foam.and all sorts of other stuff depending on frequency. Plus more fun from the inside edge of the hole.

[LawrenceH]

[quote name='Marvin' post='1318382' date='Jul 27 2011, 03:52 PM']Unfortunately the detractors, of what is somewhat basic acoustic engineering, put up little in response apart from to say they're talking rubbish because no one else builds cabs like that.[/quote]

Lots and lots of people and companies build cabinets like the BF ones, ie reflex boxes.
A fair number of manufacturers in the PA world have also build horn-loaded cabinets like the BFM designs. Their strengths and limitations are pretty well characterised - I built a set of Jack 10s, measured them and while I was at it modelled the design in software. The design behaved as the software predicted.

[stevie]

[quote name='Marvin' post='1318382' date='Jul 27 2011, 03:52 PM']Are you suggesting I'm just a sheep?[/quote]
Now you're putting words in my mouth :-)

[Bill Fitzmaurice]

[quote name='4 Strings' post='1318340' date='Jul 27 2011, 10:08 AM']Here's a photo of the tidal movement through a restriction from above.

Is this what the hole does (seems the opposite of the beam blocker)?[/quote]
Yes, though while it seems the opposite of the beam blocker it isn't. It's just two different implementations of the same phenomena.
What the pic shows is what happens to the short wavelengths that lack sufficient energy to vibrate the foam. But since the foam isn't a solid object it's not 100% accurate, as some of the shorter wavelengths will pass through it, some with an alterdd path, some not. And the longer wavelengths will pass through the foam as if not even there.
As for the beam blocker, it acts as much as a phase plug as it does a diffraction lens. That being the case it will be more effective in the upper mids than in the highs.
You can very closely duplicate various diffractive effects with the applets found here, and also emulate side by side sources to see why they should not be so placed.
[url="http://www.falstad.com/wavebox/"]http://www.falstad.com/wavebox/[/url]

Edited July 27, 2011 by Bill Fitzmaurice

[stevie]

I don't know whether to laugh or cry.....

[alexclaber]

If everyone was good at thinking for themselves then I'd never have to say anything and all those strange guitar shop myths would never have proliferated. Nevertheless I shall continue to hope for that utopia!

[LawrenceH]

[quote name='Bill Fitzmaurice' post='1318471' date='Jul 27 2011, 05:35 PM']Yes, though while it seems the opposite of the beam blocker it isn't. It's just two different implementations of the same phenomena.[/quote]

That really depends on the foam used. This 1" thick auralex foam has absorption coefficients approaching 1 above 2000Hz.
[url="http://www.auralex.com/testdata/test/1wedge.pdf"]http://www.auralex.com/testdata/test/1wedge.pdf[/url]

A good acoustic foam at even 1/2" will absorb energy more than reflect or diffract in the mid-high frequencies giving a very worthwhile reduction in output, while as Bill says being essentially transparent at low frequencies. In those cases that image is a good visualisation for a single high frequency wave.

[Mr. Foxen]

Bear in mind in that image, the hole is about one wavelength across.

[Bill Fitzmaurice]

[quote name='Mr. Foxen' post='1318530' date='Jul 27 2011, 01:40 PM']Bear in mind in that image, the hole is about one wavelength across.[/quote]Also bear in mind the saying 'There's no such thing as a free lunch'. When you place a barrier in front of a driver in that fashion you're creating a resonant chamber, and that resonant chamber acts as a low-pass filter, attenuating the same high frequencies that you're trying to improve the dispersion of. With foam as the barrier the effect won't be anything like with a piece of wood, but it will still be there. In acoustics you can never gain in one area without making a sacrifice in another.

[stevie]

No free lunch needed. You are sacrificing the high frequences on axis to bring them closer in level to the high frequencies off axis. Quasi constant directivity. This is a really neat idea, provided free of charge to the guitar playing community and very nicely documented.
I wish I'd thought of it - don't you Bill?

[Mr. Foxen]

Trace already did stuff with front resonant chamber: