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first rig purchase - check my thinking

#41
Tusec said:
3 dB is generally considered the smallest increment that most people can clearly discern. It's pretty subtle.

Here's the thing about speakers. Let's say you have a 100 watt amp and you've got it cranked through a single speaker. In this case the speaker is delivering 100 watts. Now let's say you crank it through two speakers. The 100 watts is now divided between the two speakers so that each is delivering 50 watts. Yes, you have two speakers now, but the total power delivered is the same: 100 watts. So there's no reason to expect an increase in volume based on power alone.
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i don't know exactly how it works, but it doesn't work that way. if it did, a 110 cab with 300w going through it would be as loud as an 810 with 300w going through it, and we all know that a 110 doesn't have nearly the output of an 810.

But what this doesn't take into account is acoustical coupling -- in other words how well the speaker(s) are actually able to get the air moving. At typical guitar frequencies, I think a single speaker is able to transfer the amplifier's power into the air very effectively. The reason 4x12 cabinets were invented back in the day wasn't to create more volume, but rather to keep speakers from blowing by dividing the power between multiple speakers.
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sorry, not true. the positive difference in tone between a single speaker combo and a double speaker combo is tremendous, even with guitar (i play it, too).

But at bass frequencies, things are different. The long wavelengths require serious surface area to get the air moving. So the number of speakers actually does factor directly into the volume equation.
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another "sorry, not true." i've seen small single speaker bass cabs with every bit as much measured low end response as any large cab with more speakers. it's all in the design.

Or at least that's my non-expert take on it. You start getting into concepts like acoustical impedance matching (which is distinct from electrical impedance matching) with this stuff, at which point I only know enough to be dangerous.
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ok, well there's one thing you got right ;) fortunately, tb is full of very scientific minds who not only know this stuff way better than us, but can explain it better than i can. i'm not near at their level, but i have gotten past the dangerous stage ;)
 
#42
Jim, I think you may have mistaken Tusec's first point. Take your first two quotes from his post and merge them into one. (I took that) he meant 'you can't expect an increase because of more power ('cos there isn't any) but having more speakers does make a difference.'

When you double speaker surface area and keep all other factors the same. Ie. you have a hypothetical 12" driver with a certain set of of T/S parameters that is 4ohms as rig A. Rig B is two of those EXACT same drivers but with an impedance of 8ohms each (so amp power is that same). Because rig B has physically twice the 'push' on the air in front of the speaker cab, there is a slight (3dB) gain in sound pressure. This is the same effect as doubling the power output of a theoretically-perfect amplifier.

In practice, because often cabs are different and because SPL=/=volume, you get a volume boost as well as tonal changes*. But nowhere near 'double' the volume. SPL is a logarithmic scale, by it's very definition 1 bell (10 decibels) is double the sound pressure. To the gigging musicians like me this might as well be French though. No-one (at least that I've met) has either of those two rigs above and even if they did most pubs and clubs aren't designed to be anechoic chambers. More speakers or more cabs means your pants will flap more. Whether you get 2.8 or 3.9dB at 541Hz isn't really of too much concern. Hook up a bigger cab and see if that is loud enough then. If not, add more of something 'till it is.


* = This has something to do with loss of high-end as drivers couple and interfere and such. BFM keeps explaining it, and I keep getting lost off.
 
#43
JimmyM, I'm going to have to disagree with your disagreement some, so brace yourself. ;)

JimmyM said:
i don't know exactly how it works, but it doesn't work that way. if it did, a 110 cab with 300w going through it would be as loud as an 810 with 300w going through it, and we all know that a 110 doesn't have nearly the output of an 810.
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Well, I was talking about a guitar cab there. Volume is less dependent on surface area at guitar frequencies, especially at the upper end of the guitar range where a lot of its perceived volume is. A bass cab is a different story.

sorry, not true. the positive difference in tone between a single speaker combo and a double speaker combo is tremendous, even with guitar (i play it, too).
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I just have to disagree with you here. When I was building a 2x12 cab for my Bassman and fiddling with different speaker combinations, I was impressed with how undramatic the difference in one versus two speakers was.

another "sorry, not true." i've seen small single speaker bass cabs with every bit as much measured low end response as any large cab with more speakers. it's all in the design.
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Yeah, you can do some things with cab tuning to make a small speaker pump more air. In those cases you're overcoming its smaller surface area with the resonant characteristics of the cab. Basically there are two ways to increase the displacement of a piston -- either by increasing bore or stroke. A tuned cabinet lets you increase stroke by allowing greater speaker excursion.

But the limitation is that a speaker can only have so much excursion before it tears itself apart, and also that the longer excursion only occurs around the resonant frequency of the cabinet. To get higher volumes with a flat response across a broad range of bass frequencies, you have to have more surface area.

ok, well there's one thing you got right ;) fortunately, tb is full of very scientific minds who not only know this stuff way better than us, but can explain it better than i can. i'm not near at their level, but i have gotten past the dangerous stage ;)
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I hear you. Maybe one of those guys can chime in and enlighten us here. And actually, since this is probably an ancient and long-settled dispute, I'll bet some strategic forum searching or googling would pull up the answer. If I get a chance, I'll see what I can dig up.
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#45
Jack said:
Because rig B has physically twice the 'push' on the air in front of the speaker cab, there is a slight (3dB) gain in sound pressure. This is the same effect as doubling the power output of a theoretically-perfect amplifier.
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I guess my basic point is that there isn't any free lunch when it comes to power and volume. I don't think you put any more power into the air by increasing the number of speakers while keeping the amplifier power constant, assuming you have good acoustical coupling between the speakers and the air.

By analogy, I don't think a truck with an engine of given horsepower will accelerate any faster if you switch it from a standard axle to a dually axle (i.e. if you double the number of tires on each side), assuming in both cases that you have good traction between the tires and the road.

I think at bass frequencies, though, the assumption of good acoustical coupling becomes shaky. At those frequencies, more speaker area is required to get good "traction" on the air. In the case of bass, adding speakers actually does gain you something, by decreasing acoustical slippage, so to speak.

Same caveat as before -- I could be way off track with this reasoning.
 
#46
kevin newsham said:
C'mon guys! Rebecca's head is going to explode! This is a first rig question, let's keep it to that.

It is simple, more quality power, and more quality speakers make for more volume and dispersion of sound. Not scientific, but Rebecca wasn't looking for a scientific disertation.

Keep
It
Simple
Stupid
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:rolleyes:

Trust me, it'll be okay.

Rebecca's head isn't going to explode. The basic answer was given upthread and now we're boring a little deeper into it. This happens all the time in forums like this where people are interested in, you know, discussing things?
 
#48
I don't think this has been discussed (maybe I missed it) but, the sound you like when playing by yourself is seldom an ideal sound onstage with the full band.

When you are playing by yourself, at home or in a store you may dial in a very pleasing tone. Once you are at the gig, you may find that same tone just can't be heard.

In the context of playing with the full band on a gig there are a lot of tones coming from other instruments and that can make your "home tone" disappear.

Low end (bass) is what it is and does not greatly affect your tone as much as mids do. Just because you play bass doesn't mean you should focus only on the "bass" tone controls. Mids are where it's at. It's the mids that define your tone. Typically what sounds kind of "honky" or sterile at home makes your bass sit perfectly in the sound of the overall band live.

As many have mentioned, start with all of your controls flat and adjust from there. But I would suggest that you do this at a band rehearsal instead of playing by yourself.
 
#49
Tusec said:
:rolleyes:

Trust me, it'll be okay.

Rebecca's head isn't going to explode. The basic answer was given upthread and now we're boring a little deeper into it. This happens all the time in forums like this where people are interested in, you know, discussing things?
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Yeah, it's OK. Actually the theory side is kind of interesting, although I don't understand it all. It's the shopping side that I have little patience for - almost wish there were fewer choices. But I've got some good ideas and am allowing myself a budget of about $1000 for the whole thing (ideally less, if I can get something used), so I should be OK.

But I am wondering now about whether there is some other reason people favor different speaker sizes. I see a lot of people using 2X10 and 4X10 - is there some reason, other than volume, size, weight, etc, that one might prefer 10" vs 12" vs 15" speakers? Is there a tone/taste component as well? Or perhaps, something related to fitting in the mix? Or something else?

And is there some advantage to more than one speaker, other than surface area alone? I mean the surface area of two 10" speakers is very close to the same as the surface area of one 15" speaker. All things being the same (which I know they never are), would one expect roughly the same volume from each? (Maybe this was addressed and it flew by me)
 
#50
Yes, it does happen all the time. People make a simple question as complicated as they can. Then twenty pages of point-counter point later, with the OP checking out long ago, the thread fades away. Mental masterbation, like other types, always ends messy and pointless.

Keep it caveman simple. More quality power, more quality speakers, more quality sound and volume.

Too simple for you?
 
#51
Rebecca said:
I see a lot of people using 2X10 and 4X10 - is there some reason, other than volume, size, weight, etc, that one might prefer 10" vs 12" vs 15" speakers? Is there a tone/taste component as well? Or perhaps, something related to fitting in the mix? Or something else?

And is there some advantage to more than one speaker, other than surface area alone? I mean the surface area of two 10" speakers is very close to the same as the surface area of one 15" speaker. All things being the same (which I know they never are), would one expect roughly the same volume from each? (Maybe this was addressed and it flew by me)
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This is quite a complicated subject in itself, Rebecca. Many people (rightly or wrongly) associate the smaller speaker sizes with a brighter, punchier, more in-your-face type of sound. As speakers get bigger, they expect more of a fatter, rounder, thumpier type sound.

Now, there's no reason for this to be the case, but as it's what most people expect then it's the stereotypes a lot of companies will play up to and many design their cabs this way. I would caution you to never, ever buy an amp without playing through it with your bass first. Loudly.

If you like the sound of the GB stuff then I would recommend the 6.0 and either a 2x12" or 2 of the 1x12". If you have to skimp somewhere buy the less powerful head but keep the speakers. That would be my advice.

In response to your other question, in theory the best way to see how loud a given speaker cabinet is is to look at the sensitivity rating on the spec sheet. This tells you how loud the cabinet will get at a given frequency with 1 watt. In practice though many manufacturers tend to either bend the truth or downright lie so you can't trust these numbers. In general I'd say a good 2x10" could hang with a good 1x15", with a 4x10" being a little louder. (3db if it was perfect!:D)
 
#52
Kevin: It's not really 'point counter-point' though is it? It's pure, demonstrable physics.

Tusec: Acoustic coupling happens at every frequency and is not just a function of low-frequency drivers. TB's very own Bill Fitzmaurice sums it up brilliantly in the second post of Invalid Link Removed thread. And it just gets better from there.
 
#53
Jack:

I think the problem a lot of people have is understanding the dB thing. I know it's not a simple extrapolation and is non-linear - but that too may cause consternation to people who don't know about dBs in relationship to perceived volume and frequency responses. (I know - that's just not so, I can hear you saying). Unfortunately not everyone has a degree in acoustic engineering.

But a lot of the things spoken become voodoo-logic to persons who are just starting and even to people who just know that they know these things - [However] incorrectly, that is.

I checked the search engine and older posts and cannot find a simple chart without a lot of scientific notations and techno-buzz words - or one that makes a simple comparison available to a neophyte to envision. I know it's not that cut-n-dried, but perhaps some simple white board presentation would be nice to have about now.
 
#56
Jack said:
with a 4x10" being a little louder. (3db if it was perfect!:D)
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Why do you think doubling the speakers would double the power? All that happens is you divide the power between the speakers. You don't get more power.

If I'm in the back yard filling a bucket of water with a hose, the job doesn't go twice as fast if I connect one of those Y connector things to the end of the hose. All that happens is half the water goes down one branch of the Y and half down the other branch. You don't miraculously get twice the water.
 
#57
2670777710_7c7c8111d6.jpg


Uh huh.
 
#58
Rebecca,

These days a good pro tone is relatively easy to obtain. Here are some pairings I could gig for a long time:

Virtually any head made by one of the reputable manufacturers will get the job done. The magic is learning how to eq - once you get that down, the world really opens up. It is a valuable skill, as once you're gigging a while you'll get to the point where you'll have to deal with a supplied backline. If you are good at eq'ing, this is fun.

As far as speakers, the work you're looking to do will need either 2 12's, a 410 or maybe a 215. I'm a fan of 2 112 cabinets, I can get away with one for practices, and tote both when the room calls for it.

Jim
 
#59
Interceptor said:
Rebecca,

These days a good pro tone is relatively easy to obtain. Here are some pairings I could gig for a long time:

Virtually any head made by one of the reputable manufacturers will get the job done. The magic is learning how to eq - once you get that down, the world really opens up. It is a valuable skill, as once you're gigging a while you'll get to the point where you'll have to deal with a supplied backline. If you are good at eq'ing, this is fun.

As far as speakers, the work you're looking to do will need either 2 12's, a 410 or maybe a 215. I'm a fan of 2 112 cabinets, I can get away with one for practices, and tote both when the room calls for it.

Jim
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+1...I'll add my favorite cabs, "two" 210's for the same transport and coverage reasons Jim stated.
 
#60
Tusec said:
Why do you think doubling the speakers would double the power? All that happens is you divide the power between the speakers. You don't get more power.

If I'm in the back yard filling a bucket of water with a hose, the job doesn't go twice as fast if I connect one of those Y connector things to the end of the hose. All that happens is half the water goes down one branch of the Y and half down the other branch. You don't miraculously get twice the water.
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that isn't accurate... To make the analogy work, it is not like adding a Y to the hose but by using a hose that has twice the diameter and then adding the Y. When you change the load on the amp, the number of ohms, you change the amount of power the amp puts out. In general, if you drop from 8 ohms to 4, you more or less double the power in addition to adding more speaker surface area to move the area. All things being equal (which they wouldn't be), double the power and you get 3db more volume. To have twice the volume you need to multiply the power by 10. Again, adding more speakers changes these numbers because you're also moving more air with the additional surface area.
 

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