Dispersion in Bass Cabs. Is it really important?

[Jus Lukin]

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Edited February 24, 2022 by Jus Lukin

[stingrayPete1977]

I did a gig last year with no monitoring at all for the first 7 or 8 songs, when I say no monitoring I'm taking no bass amp, no guitar amp and no wedges (which were going to be our sole monitoring), nothing for vocals at all! Oh dear that was tricky

Edited May 23, 2017 by stingrayPete1977

[Beer of the Bass]

[quote name='stingrayPete1977' timestamp='1495570735' post='3305012']
I did a gig last year with no monitoring at all for the first 7 or 8 songs, when I say no monitoring I'm taking no bass amp, no guitar amp and no wedges (which were going to be our sole monitoring), nothing for vocals at all! Oh dear that was tricky
[/quote]

Aargh, sounds horrible! I played a festival gig a few years ago where the supplied bass amp crapped out three songs before the end of the set with nothing in the monitors, so I feel your pain. Apparently it sounded fine out front, but I don't think I've ever looked at the fretboard quite so intensely. Glad I wasn't on double bass.

[Phil Starr]

[quote name='stingrayPete1977' timestamp='1495570735' post='3305012']
I did a gig last year with no monitoring at all for the first 7 or 8 songs, when I say no monitoring I'm taking no bass amp, no guitar amp and no wedges (which were going to be our sole monitoring), nothing for vocals at all! Oh dear that was tricky
[/quote]

Been there too, we had a second gig two hours after appearing at a beer festival so it suited me to use the floor monitors and save time so we could scoot off. The sound tech set the monitors up perfectly and then switched them out once we started, she put them back on after the first song but well down compared with the set up levels. Like playing with your pants round your ankles!

[Phil Starr]

[quote name='Jus Lukin' timestamp='1495564374' post='3304913']

It's probably more a question of dispersion in any speaker system, and how much one actually needs​ to hear the full range of any signal for a gig to work. And also whether​ one brand can improve on dispersion over another, or whether dispersion is a fixed factor of, say a 12" driver, regardless.

I'd love to have some kind if solid answer, but as in your OP, it's pretty hotly contested!
[/quote]

Actually this thread has been quite civilised. I'm quite keen to hear people's actual experiences about what problems they've had so I can get a feel of how much they need to hear the full range of signal.

I'll stick my neck out and try to explain the technical side of things, I declined to have a bash at that on the other thread when it all got a bit heated. The techies amongst you will see where I've glossed over a bit of detail and I'll be as accurate as I can but it'll be simplified.

All the classic experiments on dispersion have used a rigid transducer (posh word for speaker, but think more like a tiny horn driver) which acts as a piston. They did this with the 'speaker' mounted at the end of a long tube the same diameter as the speaker and repeated it in free air and with it mounted in a large flat plate. That was to show what effect a speaker cab would have (sort of). What you find is that as the frequency goes up the radiation of higher frequencies narrows once you go past the point where the width of the speaker becomes a significant fraction of the wavelength. What is happening is that from the front all of the sound from the speaker reaches your ears at just about the same time. From the side some of the sound from the other side of the speaker takes a little longer and this interferes with what you hear. (I'm happy to explain this cancellation process but let's keep it short)

In practice what this means for a 12" speaker is that up to around 500Hz gives a fairly flat radiation response and even at 1000Hz there isn't going to be too much loss of high frequencies 30degrees off axis. (This will vary with the cab a little) above 2000Hz in a practical speaker cab the response begins to be lobed and an off axis response will show quite big irregularities in the frequency response. If you go to the Faital site you can see this for yourself with the regular bumps in a falling response off axis http://www.faitalpro.com/en/products/LF_Loudspeakers/product_details/datasheet.php?id=101050110 If you are as nerdy as me you can compare speakers ad they do this for all their drivers. You can see they all have the same rough pattern but there are differences between drivers.

Of course this is all theory, in practice practical speaker cones are made of paper and have to be light or they wouldn't make much noise. This means they bend. A typical 12" speaker will have a 2" voice coil, a corrugated surround at the edge and the cone will weigh about 40g. At 2000Hz it has to move forward then backward then return to zero 2,000 times a second. That initial push from the centre takes a fraction of a second to travel through the paper so there will be a time lag before the edge moves and there will be resistance to the movement at the edge, and a limit to how fast that 40g can be accelerated and decelerated.

So the cone starts to flex and effectively only the middle of the cone keeps moving in time with the signal. Martin Colloms describes the cone vibration as contracting to the driving point with increasing frequency and offers an equivalent circuit diagram which is how speaker designers mathematically model speaker behaviour. (Win ISD works on a model like this) If you are really into this stuff then I'd recommend High Performance Loudspeakers by Martin Colloms pub Wiley as a good read. (how sad am I )

Speaker manufacturers have exploited this for years with hard metal domes and little 'whizzer cones' stuck straight onto the voice coil; used to extend frequency response. Cone materials are used to vary and control the flexing (Mark Bass use banana fibres in their pulp mix for example) and the thickness of the cones across their width is finely controlled, along with tricks like flared cones, conical cones and ribbed cones. The problem is that if you stick with pistonic cones you'd need to crossover at 500Hz, then you'd need to crossover again at 5,000 Hz as that speaker ceases to be pistonic, if you want to make a full range speaker. The holy grail of cone design is to have something that is well behaved enough under cone breakup to take you to the halfway frequency point where you can have a 2 way speaker to cover the whole range. It's what the cones do around that point which make a 2 way speaker design great or not. (maybe I've over simplified there)

So to summarise, all 12's (all speaker sizes really) follow the same pattern of radiation but there are thing we can do to make crucial modifications and they don't all have the same off axis response.

Edited May 24, 2017 by Phil Starr

[cheddatom]

[quote name='Bill Fitzmaurice' timestamp='1495562463' post='3304891']
It's actually important to put drums in the PA, the snare in particular. Even a ham fisted troglodyte's snare doesn't carry all that well throughout most rooms. Having the bass in there as well doesn't hurt, but not for the lows that carry well, for the mids and highs that don't. Just be sure to high pass the channel at 100Hz and/or roll off the bass EQ so it doesn't stress the PA. The same applies to guitar, for the same reason. It's not about volume, it's about dispersion.
[/quote]


It depends on the style of music, the size of the room, and the overall level of the mix. I'm talking about very small pubs. I have an extra heavy beater for the kick drum, and I actually have to take it easy on the snare to get the mix right

[Bill Fitzmaurice]

[quote name='cheddatom' timestamp='1495629316' post='3305411']
I'm talking about very small pubs. I have an extra heavy beater for the kick drum, and I actually have to take it easy on the snare to get the mix right
[/quote]I run everything in the PA no matter the size of the room. The difference is akin to listening to a small table radio versus a decent stereo system. Management might not care about how it sounds, the audience might not care about how it sounds, but no matter. I care about how it sounds.

Edited May 24, 2017 by Bill Fitzmaurice

[Count Bassy]

Apologies if I'm being stupid, but unless playing in large venues, isn't the bass reflected around the room so much that the original speaker dispersion has very little effect?

[Conan]

[quote name='Bill Fitzmaurice' timestamp='1495630312' post='3305427']
I run everything in the PA no matter the size of the room.
[/quote]

Most bands round our way only have quite modest PAs, and they would not be able to add much to the bass response - especially if the tops/"full-range" cabs are up on stands. Too much decoupling surely? As I understand it, wouldn't you at least need a decent sub woofer and/ or really good full-range cabs to make it worth putting any meaningful bass through the PA? Either that or EQ all the bass response out of the bass signal...

Either way, it would seem to my (inexperienced) ear that it is only really worth putting bass through a decent (and therefore expensive!) PA?

I may, of course, be wrong on any or all of this...

[fretmeister]

In the last rock band I played in I used a full stack of Marshall VBC412 cabs and we only had a small PA.
The PA was vocal only. 6ft of cabs was plenty for most pubs though.

These days I'm playing jazz / big band / orchestra sort of things and often there is no PA at all - many acoustic instruments.

Getting a good bass sound that everyone can hear, but at the same time not overpowering woodwind instruments is a bit of an art in itself. In rehearsal I often sit far away from the cab and pretty much have the cab pointing at the rest of the band. Lowish volume but everyone can hear it.

Gigs are a bit more difficult so I try and put the cab right on the edge of the stage, almost in a corner of the room, to split the cone shape between audience and band. But sometimes there will be a drum kit in 1 corner and a full set of timpani in the other...

[cheddatom]

[quote name='Bill Fitzmaurice' timestamp='1495630312' post='3305427']
I run everything in the PA no matter the size of the room. The difference is akin to listening to a small table radio versus a decent stereo system. Management might not care about how it sounds, the audience might not care about how it sounds, but no matter. I care about how it sounds.
[/quote]

There's a pub I've done a few times, the room we play is probably 15ft long, 10 ft wide. The bar runs along the length on one side. There is very limited room for the band and their equipment. We can just about fit in some PA tops on stands. The (cut down) drum kit goes in the corner, the bass amp squeezes in beside it, the guitarist DIs through his Pod, and vocals go through the PA.

I guess you're thinking we could fit some subs in too to make a nice full range PA, and put some of every instrument into it, at a very low level, and this will be nicer tonally, than just the vocals in the PA? I have to disagree. I mean, I wouldn't mind some kick drum in the PA but the snare is already too loud when played at regular velocity. I'm having to play the snare very quietly for it to be the right level at the back of the room WITHOUT any PA support. You would prefer I play even quieter and mic it up?

[Bill Fitzmaurice]

[quote name='cheddatom' timestamp='1495637460' post='3305511']
There's a pub I've done a few times, the room we play is probably 15ft long, 10 ft wide.
[/quote]My living room is larger than that. Maybe I should start charging my guests for their drinks? I can't imagine a room that small being able to pay me enough to leave the house.
As for subs, read what I actually posted. Low tend to make their way throughout the room no matter what its size. It's the directional mids and highs that need spreading about.

Edited May 24, 2017 by Bill Fitzmaurice

[Phil Starr]

[quote name='Bill Fitzmaurice' timestamp='1495641564' post='3305548']
My living room is larger than that. Maybe I should start charging my guests for their drinks? I can't imagine a room that small being able to pay me enough to leave the house.
As for subs, read what I actually posted. Low tend to make their way throughout the room no matter what its size. It's the directional mids and highs that need spreading about.
[/quote]It's a cultural thing Bill, a lot of our pubs are in very old buildings, often converted domestic houses completely unsuitable for live music, but we go ahead anyway. It's more common for drums being too loud than needing any extra help, hence the pragmatic approach. Ideal isn't available to us so we do what works. My local dates back to the 14th century.

[cheddatom]

[quote name='Bill Fitzmaurice' timestamp='1495641564' post='3305548']
My living room is larger than that. Maybe I should start charging my guests for their drinks? I can't imagine a room that small being able to pay me enough to leave the house...
[/quote]
We can't all be rock stars Bill

[markstuk]

[quote name='cheddatom' timestamp='1495698273' post='3305886']
We can't all be rock stars Bill
[/quote]


+1

[bassjim]

From personal experience, in my current regular band playing in pubs and clubs pretty much every weekend and wedding venues that are converted barns to halls. Usual stuff nothing out the ordinary. We use our backline and just keys,bass drum and vocals into tops.
9/10 we get compliments on our overall sound. I'm usually a bit too loud or just right at a sound check and adjust accordingly. Im using a 2x10 plus a 1x12 but sometimes take away the 1 x 12.
We dont go for a wall of sound thing. Last week my 2x 10 was facing front yet a good bass player I know that came along to watch,was standing off to the right of the stage/band area and said it (my bass) sounded excellent over where he was. The 2x10 was, in this venue, more than adecuate.

I'm not against it all going through a PA as long as the whoever is doing the sound knows exactly what they are doing. Done it in the past with excellent results but for my current regular band this would involve more gear, unessaccary extra stress and possibly extra personel that want paying. We dont really need it to be honest.

So dispertion and omnidirectional stuff. If these things are present when I'm playing most of the gigs I do, then they certanly are doing good work and I would say important. My gear is designed, I'm guessing, to do just this and give me and the audience within the area I'm playing in,ie ; a pub club senario, the bass sound I want and they can reconise by what they hear its a bass been played. I'm relating to what I know here so I'm refering to playing in pubs and clubs that hold upto a a max of say 250?

Bigger places that require the big PA we get a sound guy in that supplies the whole rig. In these cases I'm still using at least a 2 x 10 on stage but may position it up higher to ear level if nessaccary. Happy to point it across the stage or what ever works for the good of all.

If I turned up at a venue where the deal was you go through the house mains and this is your sound guy and thats how we do things round here then like the OP I would have to get on with it. I wouldn't be happy on the gig though.
Some sound guys rule the roost in some venues and you are stuck their opinion. I have had in the past ,where its been an in house PA, a sound guy tell me hes taking me out of the FOH as the sound from my rig sounds just perfect in the mix. He will give me sign if it needs more or less so look out. The dispertion definitley was a good thing there.

If all venues were like the one described by the OP with the volume rules set by the sound guy, and it was my experience week in week out that my rig was now a visual aid then the whole dispertion thing wouldn't matter at all. If you cant use the cab or get a smaller one that works in these situations,then it doesn't matter what the paper work says about dispertion as its become irelivent to the situation in which the cabs been designed for.

At this point I'd be looking at in ears

[Bill Fitzmaurice]

[quote name='Phil Starr' timestamp='1495646885' post='3305611']
It's a cultural thing Bill, a lot of our pubs are in very old buildings
[/quote]I know that pubs tend not to be on the dimensions of the Royal Albert, but 10x15 feet? Meters yes, but feet? My car wouldn't fit in a garage of that size.

[mcnach]

[quote name='Bill Fitzmaurice' timestamp='1495804735' post='3306756']
I know that pubs tend not to be on the dimensions of the Royal Albert, but 10x15 feet? Meters yes, but feet? My car wouldn't fit in a garage of that size.
[/quote]

yeah, 10x15 feet was probably a way to say "it's small" rather than the actual measurements of the bar. If you have the band playing, there would only be room for two customers at a time

[Jus Lukin]

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Edited February 24, 2022 by Jus Lukin

[Bill Fitzmaurice]

[quote name='Jus Lukin' timestamp='1495817800' post='3306874']
I seem to remember drinks and tickets​ were dispensed through a hatch- perhaps the missing part of the rectangle housed the office and storeroom!
[/quote]Years ago in some of the seedier sections of New York City, and I'm sure other cities as well, there were bullet proof perspex dividers over the counters at McDonalds and other fast food shops, where the orders were passed through small revolving doors. Banks in the same neighborhoods had less security.

[Jus Lukin]

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Edited February 24, 2022 by Jus Lukin

[Bill Fitzmaurice]

[quote name='Jus Lukin' timestamp='1495819948' post='3306897']
Money- no longer worth it's weight in burgers!
[/quote]I'm sure they're no longer like that. The reason: credit and debit cards. Before the barriers went up fast food joints were easy marks, and cash heavy, as that's what everyone paid with. Nowadays cash is a thing of the past. Banks were less likely to be robbed, having armed security guards. You never saw Ronald McDonald packing heat.

[Jus Lukin]

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Edited February 24, 2022 by Jus Lukin