Mixing speaker sizes

[Mr. Foxen]

Having a 4x10 and a 1x15 plugged into the same amp is totally incomparable with using different drivers for different frequency bands.

[peteb]

[quote name='chris_b' timestamp='1357863720' post='1929899']


You'd better get on to Alex right away and tell he's doing it wrong.
[/quote]
Actually, it was something that Alex said on here about the success of the design of the old fashioned 810 fridge cab that led me to change to using two 410s!

I've never played thru a BF rig, but unless Alex has found a way around the laws of physics and can make a 12 inch speaker move at the same rate as a 10 inch speaker, there is bound to be a phasing issue (see example of ripples in a pond above). Of course, it maybe that the advantages of the rig outweigh this issue for you, but it is still there.....

Edited January 11, 2013 by peteb

[51m0n]

[quote name='peteb' timestamp='1357894353' post='1930042']
Actually, it was something that Alex said on here about the success of the design of the old fashioned 810 fridge cab that led me to change to using two 410s!

I've never played thru a BF rig, but unless Alex has found a way around the laws of physics and can make a 12 inch speaker move at the same rate as a 10 inch speaker, there is bound to be a phasing issue (see example of ripples in a pond above). Of course, it maybe that the advantages of the rig outweigh this issue for you, but it is still there.....
[/quote]

He hasnt broken any laws of physics, he has designed and implemented probably the most carefully thought out crossover in any bass cab available today, which means that the different speakers are handling totally different frequency ranges. On top of this he has very carefully matched the the speakers regarding their motors etc so thatthey are extrememly compatible. Read his website info.

BTW a long time ago at the dawn of Barefaced he totally redesigned the crossover in the original BigOne design after he got feedback from me when I tried one out: the cab had a hump at 1KHz that was obvious to me but not him as I play with far brighter strings than he did. It turned out it was due to the mid range driver's internal cabinet (yes it has its own internal space in the cab it doesnt share the volume with the larger driver) not having quite the volume he thought it would when all was said and done IIRC. Now that is commitment to product design!

The BigOne has since been superseded by his newer designs which outperform it in pretty much all possible ways, yet still rely heavily on the concept of a dedicated smaller (for better dispersion characteristics) mid range driver. Because this concept is utterly valid and works so well.

[chris_b]

I don't believe crossovers are involved when you add a Midget to a Compact or a Compact to a Super 12.

[flyfisher]

[quote name='peteb' timestamp='1357859412' post='1929813']

Good analogy....
[/quote]

Thinking about this again, won't the ripples from two stones dropped in water always interfere with each other as they spread out, leading to phasing issues, regardless of the size of the stones? If so, that would suggest that any phasing issues is more to do with multiple speakers not occupying the same point in space and might also suggest that a single large speaker would be better than multiple small ones . . . except that's where the mass of the cone might become too detrimental to the speaker performance.

I guess it's all about getting the best trade-off from a number of conflicting parameters.

[chris_b]

[quote name='flyfisher' timestamp='1357899414' post='1930135']
....I guess it's all about getting the best trade-off from a number of conflicting parameters....
[/quote]

That's the point. Speaker design is all about selecting the compromises that get you the sound that you want or can afford. Those compromises will affect the performance of each cab differently and if they don't interfere with what you want out of cabs then there is no problem.

None of this is all good or all bad as some might try to insist.

[51m0n]

[quote name='chris_b' timestamp='1357898550' post='1930116']
I don't believe crossovers are involved when you add a Midget to a Compact or a Compact to a Super 12.
[/quote]

No but specific driver choice is, and that was done very carefully from what I've read and discussed with Alex to minimise the issues as best as possible.

In fact a super12 has two same diameter drivers and one tweeter. The tweeter starts above where the drivers stop. Its a designe whreby you again arent mixing driver sizes in the same frequency range.

Edited January 11, 2013 by 51m0n

[xgsjx]

[quote name='flyfisher' timestamp='1357899414' post='1930135']
Thinking about this again, won't the ripples from two stones dropped in water always interfere with each other as they spread out, leading to phasing issues, regardless of the size of the stones? If so, that would suggest that any phasing issues is more to do with multiple speakers not occupying the same point in space and might also suggest that a single large speaker would be better than multiple small ones . . . except that's where the mass of the cone might become too detrimental to the speaker performance.

I guess it's all about getting the best trade-off from a number of conflicting parameters.
[/quote]

Here's where you should keep the drivers on the vertical. Think of your soundwaves as ripples, following the same patterns.
You have vertical drivers all the same size, then you have soundwaves all the same size moving across the horizontal plane & the vertical plane has a narrower dispersion.

The cone size only determines how much air it can move, not how much of a certain frequency it has. So a vertical 2x15 would be a pretty loud rig.
However, a vertical 4x10 array (2 2x10s) will have a wider dispersion on the horizontal plane (the smaller the driver, the wider the dispersion). How much this matters to you is how well your band & audience are hearing you fully. If you're using PA with foldback, then your cab is just for your personal sound.
An 8x10 (or 4x10) has the same dispersion as using 20" drivers. So the volume drops the minute you're not directly in front of it.

Hope that helps a little.

Barefaced's website is worth a read & he probably explains things much better than I do (I should hope so!).

[chris_b]

[quote name='51m0n' timestamp='1357904295' post='1930241']
No but specific driver choice is, and that was done very carefully from what I've read and discussed with Alex to minimise the issues as best as possible.

In fact a super12 has two same diameter drivers and one tweeter. The tweeter starts above where the drivers stop. Its a designe whreby you again arent mixing driver sizes in the same frequency range.
[/quote]


That's the point.... minimise.

My examples of Alex's cabs ARE mixed sizes, 12's and 15's. And they sound good together, as do Mesa Boogie and Bergantino’s mixed speaker cabs. So, as I said, this blanket mantra of "NEVER mix speaker sizes" because they don’t work, is incorrect.

My point is, it might be easier to stick to the same size speakers, but if the cabs are designed properly and compromises are minimized or aren't sufficiently prominent to cause the player or his audience problems then speaker sizes CAN be mixed.

[51m0n]

I think its fair to say that any company that has specifically designed or tested and approved mixed speaker sizes of their products together (and we have a Berg HT115 + HT210 stack in the house which sounds unbelievablely good).

Where people are led astray is matching unsuitable cabs together (115 and a 410 are hideously mismatched in virtually every case I've ever seen - simply in power handling alone).

Also people make assumptions that the diameter of the driver in a cab defines the role that cab should play in the sound of a rig (how many 115 for more bottom end grunt paired with a 410 adverts or advice snippets have there been now?). Going back to the HT210 and HT115 I have access to at home, the 210 goes deeper than the 115, the 115 has really great mids, the two together work very nicely, and thats because of the similar capabilities of 2 10" cones vs 1 15" cone. But then the configuration was planned to work well by the designer of the entire system, which isnt always the case, and certainly isnt if you start mixing manufacturers gear.

And the simplest rule of thumb that if you want more of something get another one of the same does always bear out.

[Phil Starr]

Sorry the physics teacher in me can't let this go so I'm going to attempt a couple of explanations which i hope will help.

Let's have a go at explaining phase first since we're all bass players I'll try and use bass as the model. Pluck a bass string and release it and the middle of the string moves backwards and forwards tracing a sine wave. It'll also vibrate at other harmonic frequencies but let's keep it simple. Ultimately this will make a speaker and the air trace the same sinewave as the air is made to move back and to, tracing the strings movement. Now if a second string is made to sound a fraction of a second later it will arrive at the speaker out of phase. if both strings are moving in the same direction then the sound will be louder and if they are moving in the opposite direction then their movements will cancel and it will be quieter.

It's really easy to demonstrate this and you've probably done it. Tune the E and A string and play the harmonics on the 5th and 7th frets. A standard method of tuning. If they are in tune you will hear a steady note. If you then slacken one of the strings then you will hear the note start to vary in volume giving a beat frequency. What has happened is that the string you changed has slowed down and the sounds are moving in and out of phase. When you hear the loudest sound the strings are moving in the same direction and when it is quietest they are moving in opposite directions. Anything that delays some of the sound getting to your ears will cause this effect of reinforcement and cancellation.

The pond ripples are good at showing this too, though remember this is just in two dimensions not the three of sound waves in air. The surface of the water moves in sine waves and where two sets of ripples meet they either cancel and the peaks are reduced or they reinforce to give a sharper peak.

Now think of a speaker cone playing a single note. Each part of the cone is radiating the same note at the same time and if you are facing the speaker straight on you'll hear just that. If you move to the side however one part of the cone is now a tiny bit further away from you than the other and the sound from that will arrive slightly later. It will be out of phase and you will get cancellation some of the time. With low notes the cancellation won't matter because the delay is only a tiny proportion of the wave with higher notes the cancellation becomes important.

In practice if the wavelength is longer than the diameter of the speaker the sound will be radiated equally in all directions, above this the sound is radiated in an increasingly narrow beam with lots of side lobes. You can see the effect of this on frequency response in Alex's graphs http://barefacedbass.com/uploads/BGM62%20Jan2011.pdf

Now all this is only down to two bits of speaker cone being a few inches apart and reproducing the same note. It doesn't matter if the cones are 15's 10's or 4's or even if they are on the same cone, All that matters is the distance between them and the relative volumes. You'll get this phase effect upon dispersion whether you use identical speakers or mix them up. It is only in this way that two 10's are like a 20" speaker.in fact because of the gap between them they'll radiate like a 22" speaker.

Now if the speakers in a 4x10 are all in a long line above each other then you have a speaker which is 10" wide and 40" tall so you'll get better dispersion side to side than up and down. If you have a 2x10 and a 15 then it is still better to stack vertically but you have a 15" wide by 35" speaker and that sort of dispersal.

So to sum up the phase and dispersion problems are caused by having multiple drivers of any type or size which are producing the same frequencies and higher frequencies are rolled off compares to single drivers unless you are staring down the barrel.

There are lots of other effects of using multiple drivers and yet more effects of mixing drivers if they are producing the same frequencies but this post is already too long. Hope it helps though

[chris_b]

Phil, so how does this manifest itself when we're playing Staccato funk bass line or an 8 in the bar bass line or a walking 4 in the bar across the whole neck?

How much of the science doe we hear in the sound?

[51m0n]

It depends where you're standing....

And (IMO more importantly) the state of the space you are in acoustically.

By which I mean, in a great acoustic space it will be far far more obvious that there is a dispersion issue at all. In a very poor acoustic space its not (just) the issue with dispersion thats ruining the sound for you, its the scpace you are in.

However, the end result for a punter is only as good as the weakest link in the chain (unless by some miraculous happy occurance all the bad things add up to a decent sound right where they are standing - although their mate standing next to them thinks the sound guy is deaf). If you are using backline for stage monitoring purposes only then the issue is pretty moot FOH and it is only really affecting the other musicians ability to hear you more than anything else.

If the FOH has a pair of big stacks, one either side of the stage, then you have a completely different world of hurt regarding potential oddities and so on as you move around within the audience area, further compounded by the acoustic space. Bill Fitzmaurice recommends subs paired/ganged together in stage center, I cant remember ever seeing it done this way in practice for a live band, but it definitely gives you up to 6dB of extra oomph (with his subs) per pair, and removes/mitigates issues with the cancellayions you get from seperating the subs in the first place. Its a different topic again but definitely has an affect on the outcome of the sound at a gig.

How much you can notice the dispersion issues depends on a lot of other stuff too basically. But if you want to maximise dispersion of your rig, make it one with all the cones in a vertical line.

Edited January 11, 2013 by 51m0n

[JTUK]

[quote name='chris_b' timestamp='1357915228' post='1930537']
Phil, so how does this manifest itself when we're playing Staccato funk bass line or an 8 in the bar bass line or a walking 4 in the bar across the whole neck?

How much of the science doe we hear in the sound?
[/quote]

If it sounds great, then the science is out of the window...and I don't know any proper player who would say otherwise.

[51m0n]

[quote name='JTUK' timestamp='1357919704' post='1930650']
If it sounds great, then the science is out of the window...and I don't know any proper player who would say otherwise.
[/quote]

Heh heh, if it sounds great and you've mixed all sorts of stuff up and its turned out brilliant, then you really need to get a lottery ticket that week

[bremen]

[quote name='51m0n' timestamp='1357918879' post='1930627']
Bill Fitzmaurice recommends subs paired/ganged together in stage center, I cant remember ever seeing it done this way in practice for a live band, but it definitely gives you up to 6dB of extra oomph (with his subs) per pair, and removes/mitigates issues with the cancellayions you get from seperating the subs in the first place.
[/quote]

I saw a noted German industrial metal band at the NEC and they'd done this - flown full-trange speakers either side of the stage, and subs the whole width of the stage (roped together) between the front of the stage and the barriers.

I could hardly breathe, it was most excellent.

[Phil Starr]

[quote name='chris_b' timestamp='1357915228' post='1930537']
Phil, so how does this manifest itself when we're playing Staccato funk bass line or an 8 in the bar bass line or a walking 4 in the bar across the whole neck?

How much of the science doe we hear in the sound?
[/quote]

I'll assume this is a serious comment

first of all I am only answering the OP's question, some people like to know these things and there's a lot of misinformation on the internet. No knowledge is ever completely useless and an understanding of some basic engineering can help shortcut the process of finding the sound that suits you. Equally the science is complex enough that is only gives you part of the answer and you might well be better off just listening to great bass players and learning from them. Each to their own.

If you read all of my posts (and you'd have to be very bored before you did that, you'd certainly be bored after) you'll see that I'm always a great one for saying if it sounds good it is good, and that most of a good tone is in the fingers and mind of the bassist.

My problem is with the 'experts' who come up with "never mix speakers of different sizes" or "15's don't increase the bass" or any other helpful advice which is simply incorrect as stated and not backed up by the science.

Following the 10 pages of this thread I think it would be hard for anyone without some science background to know whether it was OK to mix drivers or to know the likely effects of doing so. Certainly almost all of the posts with any factual content confuse the effects of using multiple drivers with mixed drivers, and they don't have the same effect. I didn't think me saying you're all wrong helps much so I put in a bit of explanation for anyone who cares. I also don't want people to be put off trying things because some so called expert says you can't mix 10's and 15's.

Mixing speakers does have some predictable outcomes and some unpredictable ones. There are bad ways of mixing and better ways.

As you point out there's a lot more to playing bass than the sound the speaker makes, but this is the amps and cabs forum after all.

Sorry this all sounds more serious than I intended

[flyfisher]

[quote name='Phil Starr' timestamp='1357934598' post='1930894']
I didn't think me saying you're all wrong helps much so I put in a bit of explanation for anyone who cares.
[/quote]

That's a great sentiment and thanks very much for adding the background justification.

For topics like this (and many, many others) a basic statement or rule is one thing but the reasons behind it are where the real understanding begins.

I'm not a great one for slavish adherence to 'rules' without fully understanding (or trying to!) the reasons behind them, which leads me to question a lot of things, which sometimes makes me seem awkward and argumentative. One thing I have learned over many years though is that people who really understand stuff rarely mind answering questions and sharing their knowledge whereas the ones who don't understand often resort to 'because it just is' or 'because I say so' replies instead of the more honest 'I don't really know' or 'that's my assumption/guess/understanding'.

So please don't feel the need to apologise for long posts of detailed explanations - not on my account anyway.

[Phil Starr]

Oh s**t after my last post I had better get on with explaining why I think there is nothing in the science to stop you mixing speakers in a stack and why anyone who gives that advice may be well meaning but is fundamentally wrong.

Firstly there are lots of advantages in using a single driver and keeping it small when it comes to the dispersal pattern of the speaker. If you use multiple drivers of any size better to arrange them vertically if you can. I've explained why above or use the link to barefaced http://barefacedbass.com/uploads/BGM62%20Jan2011.pdf This all assumes the single driver has the sound you want and is loud enough.

Using more of the same drivers won't just give you more but louder as some people are saying, There will be cancellation of higher frequencies and the tonal balance will change, by the time this has bounced off the floors, ceilings and walls the audience will hear the difference. However if you want more but louder there probably isn't a better way of getting it.

So, why do I think it is OK to mix drivers and to use multiple drivers, Well first of all lots of famous songs and bands have used 8x10's and 4x10's with 15's and had a great sound. We're not talking about hi-fi speakers and most of what we think of as the sound of a guitar amp or speaker is about inaccuracy in the sound. mixing drivers causes distortion but we don't say "it is always wrong to use distortion on your bass". All cabs distort the sound and whether that distortion is acceptable to you or not is a matter of taste not science.

So what distortions are introduced when you mix drivers in your stack?

If you get time look at the link above, there are three frequency plots for different speakers. The most important bit of the plots in determining the sound of the speaker are the bits between 500 and 5000Hz roughly, because that is where our ears are most sensitive to changes in sound. If you look at the first speaker it has a few peaks in this area (where the speaker is louder) and it cuts off at just over 2000Hz theres another peak at 5,000Hz and lots of lumps and bumps. The cut off at 2000 Hz would mean this would be raqther dull sounding with bass. the second speaker shows a large peak between 2k and 5kHz, up 5dB so it would sound quite lively with bass. Like the other speaker there are lots of minor lumps and dips in the frequency response.. So what would happen when you mix the two. Well obviously where two peaks coincide you'd get a bigger peak and where a peak and a dip coincide you'd find them compensating and cancelling each other. Actually a plot in more detail would show a lot more peaks and dips. They rarely completely coincide and so the overall effect is a kind of leveling down. Rather than getting the character of both speakers you get less of the character of either of them. There are so many irregularities though that it is really hard to control a design by doing this, you just have to try it and listen so designers who are trying to control a sound shy away from this method,

The second thing is the 'sound' of a 15 and a 10. Alex says that they don't have a 'sound' applicable to all 10's and 15's and this is right especially as so much depends upon these higher frequency resonances which are much more individual to each design. It's not even true that 15's go deeper, My 5.25" hi fi speakers go much deeper than any bass guitar speaker. But, and it's a big but, if you took 25 different 15's made for bass and 25 10's you'd find the average cut off frequency was lower for the 15's and the bass efficiency would on average be higher. The average for 25 12's would sit in the middle in all probability.So adding a 15 to get extra deep bass can work and isn't a daft idea, you just need to check it is the right 15. There might also be a 2x10 that will do the job too of course.

So there you are, you can mix speakers and you can get extra bass with a 15, but any old 15 won't do and there are no guarantees how it will sound. The science makes sense but sometimes you just have to try things. Me? I use a single speaker and DI through the PA.

Edited January 12, 2013 by Phil Starr

[xgsjx]

You make some interesting reading there mr Starr & I like that you've backed things up with reasons.
I think when it comes to mixing drivers, you should use your ears & go for what sounds good to you. Some rigs sound good with mixed drivers, some don't. In most instances it is going to be unpredictable (not necessarily in a bad way) whereas from what I've read & heard so far, keeping them the same means that you're most likely going to get a similar sound at each venue.
I'm no expert on speakers, but I do like to know the reasons behind things when I'm setting things up so I can get a good sound & know where to look if it doesn't sound right.

[Bill Fitzmaurice]

[quote name='chris_b' timestamp='1357915228' post='1930537']
How much of the science doe we hear in the sound?
[/quote]Everything you hear can be explained by the science. If you don't think that's the case it's your understanding of the science that's incomplete. The good news is that you can learn the science, should you be so inclined. Or you can ignore it, even deny it. No matter, the science is always right, whether you believe in it or not.

[chris_b]

Thanks Phil, for helping me to understand cabs a little more.


Sorry Bill, that didn't address my question at all. But I think you knew that!

[Mr. Foxen]

You'll probably need to rephrase the question in that case. If you can hear something, its directly observed, and science can cover directly observed stuff pretty quickly, so its going to be all of it. The bit your brain makes up is a bit harder, but the relevant bits are also covered.

[Bill Fitzmaurice]

[quote name='Mr. Foxen' timestamp='1358008915' post='1931799']
The bit your brain makes up is a bit harder
[/quote]A bit, but people have been studying this stuff since circa 1876, so at this point there isn't anything in the realm of audio that hasn't been scientifically explained. But it's not the sort of stuff they teach in secondary schools, nor even at the university undergraduate level at most institutions, not even those with EE programs.

[Mr. Foxen]

[quote name='Bill Fitzmaurice' timestamp='1358009552' post='1931822']
A bit, but people have been studying this stuff since circa 1876, so at this point there isn't anything in the realm of audio that hasn't been scientifically explained. But it's not the sort of stuff they teach in secondary schools, nor even at the university undergraduate level at most institutions, not even those with EE programs.
[/quote]

Meant more the stuff like 'this rig is the wrong colour, therefore it sounds bad' type stuff. Lots of it about, in many minds, the most significant contributor to tone is the name badge.