Phil Starr

OK I said I'd look at choosing a driver. Now I have to be honest and say I don't know exactly what a driver is going to sound like from a spec sheet alone. However having an understanding of the specs and a bit of experience gets me 80% there. A very simple approach will rule out the real duds and that is what I'll try to explain. I'm not going to use algebra but to really get any deep understanding you'll need to get to grips with it or trust the computer to do it for you. Basically if you know how heavy a cone is, how stiff its suspension is and how much air it is pushing against and add in the springiness and mass of air in the box you can work out how far the cone moves for a given force at a given frequency. If you know all about the magnet and the coil you can work out the force so for each frequency you can work out the sound level. If you get it right the box volumes and the speaker match up, called an alignment, and the output is more or less the same at all frequencies. (the engineers and scientists are probably going to shoot me down for over simplifying here ) OK to choose the speakers I'm going to look at four parameters only, Vas which roughly says how hard it is to move the speaker cone Qts which is all the mechanical and electromagnetic factors lumped together, Fs is the resonant frequency and says how low the speaker will go and Xmax which is how far the cone can move before the coil leaves the magnet and is the true measure of how much power the speaker can handle. Now the speakers I am going to look at are the Eminence Alpha, Beta, Delta and Kappa (what happened to Gamma?) Alpha fs-49Hz Qts 0.77 Vas 121.5 Xmax 2.4mm Beta 47 0.46 120.1 4.4 Delta 55 0.43 81.3 2.4 Kappa 45 0.27 112 3.2 All the specs are here http://www.eminence.com/pro-audio/american-standard/?size=12#speakers you need to download the PDF's Now you could just plug the data into win ISD or do the sums but if you can find an alignment chart, I haven't been able to find one on the internet but most books on speaker design have them. Basically for each value of Qts there is a fixed ratio between box size and cut off frequency. Low Q means a smaller box and a higher cut off frequency. Q of about 0.4 is ideal for reflex enclosures. So the alpha has Q=0.77 which is too high because it has a titchy magnet. this means the box needs to be roughly 3x Vas (360l 0r 12 cu ft) for the best response which still has a huge bass hump of over 6dB. You can put it into a smaller box but you are going to make the bass hump even bigger. This speaker just isn't suitable for a reflex design and the magnet is too small to even make a decent sealed cab really. It's a dud. The Beta has been redesigned recently. Q is ).46 which my table says means box size is Vas/1.03 or 120l which is big but practicable. The bass peak is 1dB which you will just notice. The cut of frequency is fs/0.97 or 46Hz which is OK too. Put it in a smaller box and you will get a bigger bass hump and cut off will rise a little but this speaker works for me. The Delta is a missed opportunity for me. They've added a bigger magnet but stiffened the suspension. this has raised Fs to 55Hz. The lower Vas and Q means the box size comes out at 70l with a bass hump of 0.5 dB which yoiu won't notice. The big problem though is Xmax of 2.4mm, this means the coil will move out of the magnet at relatively low powers and the speaker start to distort with any real bass. The kappa has a huge magnet, Q is now 0.27 and my design table says to divide Vas by 3.17 to get box size or 35l. the big magnet means a compact box. Unfortunately making Q so much lower than 0.4 raises the cutoff frequency which is Fs x 2.15 or 97Hz. This is too high for a bass cab where bottom E is 41Hz.. Xmax is 3.2mm which is still fairly poor. This is a speaker which would be much improved by having a longer voice coil and different geometry giving a better Xmax and a better bass performance at the expense of sensitivity. So I've surprised myself by coming down in favour of the Beta, the best of this group though it needs a fairly generous cab and will still have a warm and woolly bass hump. I might put the Deltas into winISD if I was bored but the other two are not worth looking at. I wouldn't buy any of these. So far I've only looked at bass response but that alone has narrowed the search. If Qts is outside of 0.3-0.5 fs is over 50Hz or Xmax less than 4mm I won't look any further because I am unlikely to be able to engineer a decent cab. If Vas is too big then the cab will have to be correspondingly large so that's a side issue too.

[quote name='Mr. Foxen' timestamp='1360376186' post='1969684'] Out of stock mind. Not spotting them anywhere else with half arsed effort. [/quote] Ah, I forgot to mention the other problem, Blue Aran order these from Spain and they take ages to arrive. [quote name='Musky' timestamp='1360395397' post='1969712'] I'm certainly no expert, but doesn't stuffing a speaker into a smaller than ideal box create a hump in the low mids - which seems to be what the OP is looking for? [/quote] If that is what he is looking for then yes it will create a hump. Just needed to mention that when designing the cab it is one extra constraint. Mainly I wanted to give an idea of how to look at T/S parameters in choosing a speaker. Qts of around 0.4 gives you a chance of a flat bass response but Vas of 150l means a bigger cab. My speakers are in a considerably undersized cab which, sure enough, gives the hump you mention.

Just off to bed but OK then. I'm not sure what sort of sound a Berg makes so if you find me a link to a good recording or you or someone else can describe it I'll be able to get close. If you can find a frequency plot that will be perfect. In the meantime there's a 12" speaker that is a real gem for bass that I actually use when I'm not DI'ing, the Beyma SM212. http://www.bluearan.co.uk/index.php?id=BMASM212&browsemode=manufacturer http://profesional.beyma.com/pdf/SM-212E.pdf Why would I go for this? well Xmax is conservatively 7mm, tht's how far the cone will travel without distorting. This means that you won't lose output because the coil has left the magnet gap at high power. 2. there's good output up to 5,000Hz so there's plenty of top end there without a tweeter. This is done without a huge peak in output at 1-2kHz that a lot of the Eminence designs display. (not necessarily bad but it does colour the sound.) 3. Fs is lowish so you'll cover fundamental bass down to 40Hz 4. Qts is 0.38 which makes it relatively easy to tailor the bass to give a flat response. 5. It is nicely made with a cast chassis, sensitivity is OK too The only problem is that for a 12 it does need a fair size box ideally. The sound with bass is pretty open and clean sounding, you hear the strings coming through nicely. Bass is clean and deep without being boomy, just well controlled. Because of the excellent top end response you hear lots of detail too but without the Eminence cone break up the speaker doesn't add too much character of its own. I'll talk you through the Eminence and Fane ranges and try and predict strengths and weaknesses for you tomorrow. I've used both quite a lot but nothing matches the Beyma at this price point at the moment IMO

I feel for you a bit, not that the expert advice is wrong but it isn't very helpful. There's nothing wrong with the up-front recognition that a ceramic magnet is going to be cheaper than a neo for example. First of all there is nothing wrong with 12's but what people are saying is that the sound isn't defined by diameter, 12's, 10's and 15's overlap in sound however you have to start somewhere, so lets assume you will build a 12 and that you aim to learn about speakers by doing this project. we all start somewhere. First of all can I ask a question? Are you doing this because you think you'll get your dream speaker, because it will save money or because you want to learn? You won't get your dream speaker because you won't really know what yours will sound like until you try it out, by then it is too late to change. You might not save money either, you can't source the speakers as cheaply as the main manufacturers or the other parts, the best way of saving money is to buy used, then you can try what you are getting and sell it on if you change your mind. You will however learn loads and end up with a giggable speaker if you listen to some of the advice. I'd advise building a 1x12, if you like it you can build a second, if not you've only paid out for one speaker If you still want to go ahead let us know and we can start looking for what you want.

raising the cab will have two effects. Putting the cab at ear level will mean you will hear more of the upper frequencies and hence tell you more about how you are playing. It will also sound louder to you relative to the rest of the band. Secondly having the speaker on the floor means the floor acts like a big sonic mirror giving you an extra 3dB of bass. Moving it this high will reduce this effect and also cause some frequency dropouts dependent upon the height. Your audience will hear a bit less bass. Probably this will all just clean up your sound but you might need to eq differently and if you lack power floor and wall reinforcement is useful, Try it but as others have said a cab stand may be more practical.

You can definitely do this but you wouldn't expect authoritative bass from any old bass speakers and you shouldn't from any old PA speakers, you have to use something to do the job and choose just as carefully. Generally cheap speakers have smaller magnets which means sensitivity (how loud) and bass handling have to be compromised. you can have loud bass which runs out of steam at really low power or you have a speaker which handles bass but isn't as loud as a fully specced speaker. The amp in this isn't usually the issue, amp watts are cheap. the other issue is sound, some people like the clean sound of bass through the PA and others use a tone where the natural distortion of their dedicated bass speakers is an integral part of what they try to achieve. What's your taste? Decent stage monitors/PA speakers can surely give you a good sound and plenty of volume but I doubt those Behringers will. My 15" Yamaha monitors sound great but they aren't cheaper than a proper bass speaker, just different.

You don't need to worry about a speaker being 'too many' watts, you can drive a 1000W speaker with a 1W amp if you want, it's the same as turning the volume down. I'm not sure you have the speakers right, Eminence don't list a Beta just the beta A. Certainly a beta won't handle 600W. I suspect they are the same speaker and one advertiser is quoting its RMS power and the other its music power. There's lots better speakers out there, though this may be a good enough match for the Ashdown speaker. Are you replacing to upgrade, or has the original blown?

I think icastle has it. jack plugs weren't really a standard size and there used to be considerable variation so some pugs will just make better contact than others, replacing the output socket will help but you might improve things by using a spray of switch cleaner onto the socket contacts, Find a plug that works and make up a speaker cable with that. I find gold plated plugs do often make a cleaner contact but replacing the socket is the cure. If the crackle persists I'm afraid it could be any one of a number of caps or almost any joint inside the amp or even worn or dirty potentiometers.

To find the volume of your cab accurately you need to measure the internal dimensions of the cab and subtract the volume of the port but very roughly it is about 90litres which is about ideal. Unless your cab is really old and battered I wouldn't start using surgery yet. It is worth more second hand as an original cab. If you can get the back off easily you can mount the driver to the rear of the baffle (front panel), you might also be able to fix it (untidily and temporarily) in the hole for long enough to test whether you like the sound of the new driver. To do this just make the speaker frame seal against the cab with draughtproofing foam strip or possibly mastic, though this is messy.. Once you have started cutting the baffle you won't be able to put the original speaker back in if you prefer it to the Faital.

Specs are here http://www.adamhall.com/en/Faital_Pro_Professional_Series_-_15_Speaker_400_W_8_Ohm.html. These are good speakers, best suited to a cab of about 100 litres. The simplest thing to do would be to try them in your cab and if you like the basic sound to build a cab actually designed to go with your speakers. if you think building a cab is beyond you then look for a cab which has a circular port as these are easier to re-tune and it would be best to go for something between 70 and 100l. The Peavey BXBW would be good and you can pick these up for a lot less than a GB cab. (£50-100) You'd probably get £40 for the Black Widow driver on eBay so you'd get a substantial box for probably less than £50. If you decide to go this route I've actually got an old one of these which I'd happily sell empty, though it is up for sale with the original driver at the moment. Ideally I'd put these into a couple of light weight cabs custom designed though and take advantage of these neo speakers.

Sorry, but another vote for the AER Amp One

I used one of these (mk IV) and it gave a great sound.

For Promethean and clones http://basschat.co.uk/topic/168416-another-promethean-clone/page__st__240__p__1886279__hl__promethean__fromsearch__1#entry1886279

Having a back up amp is a great idea for any performing bassist though youcan always go through the PA so taking along a Sansamp or something similar would get you out of a hole. It makes sense for a backup amp to be cheap and light so look for one of the newer switch mode amps like the Promethean. There are cheap clones/rebadged versions of this in europe so look for similar in the States. Behringer is built to a budget, so less attention to detail and cheaper components but good design and value. Their PA amps are well respected though and seem fairly robust, I have two, never a problem. The amp part of the heads will be the same so as long as you don't get the last one made on a Fri I wouldn't worry. If I wanted just a backup amp for less than $200 I'd probably buy a used Peavey. Do the job and bomb proof.

[quote name='aende' timestamp='1358415163' post='1938603'] Interesting - I looked at the eminence beta too. I spoke to blue aran and they recommended a p audio driver..... This may be a suck it and see..... [/quote] Ultimately it always is, the problem with DIY is you can't try before you buy, but the more you understand the better chance you have of being happy with the result. [quote name='Bill Fitzmaurice' timestamp='1358431907' post='1939002'] You're not considering the most important charts, maximum power and maximum SPL. [/quote] Well that's kind of true but if it sounds s**t then being loud and s**t won't help any more than sounding great at one watt but exceeding xmax at anything like stage volume. [quote name='aende' timestamp='1358436333' post='1939108'] This is true - My budget is tight due to an ongoing job/house move - However, I did read this: [url="http://billfitzmaurice.info/forum/viewtopic.php?f=12&t=2357"]http://billfitzmauri...php?f=12&t=2357[/url] on your website Bill. Are Eminence Alpha 10's really a close match to the driver in the Ampeg SVT210HE cab? I am using the SVT210HE at the moment borrowed from my father-in-law. However, my 'new' cabs are similar in size a volume - peavey tx cabs unloaded tuned for 40hz with crossover and horn at 3500hz - 80 liters or 3 cu ft volume - ported at the rear. I have opted for the Eminence Beta as I prefer some low end. However, I am wondering if I could have used the Alpha...... [/quote] So have you ordered the Beta's? I was going to put the drivers into winisd for you but if you've ordered it is too late.

[quote name='aende' timestamp='1358355521' post='1937689'] Thanks Phil - I agree with you. I think I will run up one cab now and see how it goes. My thoughts are more towards the Eminence Delta's mentioned - they seem to be a bit more punchy. [/quote] If you compare the Delta 10A with the Beyma you are going to hear quite a difference. The Delta's have a huge cone resonance which gives a big peak in frequency response centred on 2.7 kHz. and a roll off at 3.7. This upper mid peak is going to dominate the sound and may well come across as punchy. There's a huge magnet for a speaker this size and that gives good control of the cone. On the minus side the cone is quite light (probably why it is peaking in the upper mids ) and the resonance is high for a bass speaker at 66Hz which is about bottom C so little fundamental for anything lower than C. The big magnet will roll off low frequencies too. Again this will give a lighter faster sound to the speaker. Having said that we don't really hear the fundamentals that well and really deep bass can result in a boomy sound in a lot of venues. If you compare this with the Beyma the heavier cone damps the resonance better and the mid range peak is smaller (5dB v's 8) more importantly the bass resonance is lowered to 43Hz, more or less bottom E. This speaker is going to have a modern sound with good control of deep bass, which is actually going to be there. The SM110 also gives more treble output. The biggest difference is in Xmax and Xlim, basically how far the cone can move before distorting and then damaging the speaker. Sadly they use differnt ways of expressing this with Beyma more conservative. I reckon the Beyma would measure about 6.5mm for Xmax compared to the Delta's 3.5mm meaning the Beyma will move twice as much before distorting. I haven't modelled these speakers but I think the Beyma will handle more power than the Eminences despite the thermal rating. The Beyma also has the plus of a cast chassis. There isn't a right choice here though, you just need to decide on what sound you want. The Delta has the sort of response you'd get from a guitar speaker at the top and less deep bass but could well give the sort of 'in your face' sound you want. the Beyma will be better behaved, if my 112's which have similar properties are anything to go by they are subtle and revealing. More Jazz bass than Ricky. Oh be prepare to wait for the Beymas though, they're Spanish and will have to be ordered by Blue Aran.

The problem with the driver you suggest is that it is very low sensitivity, only the same as a hi fi speaker so you'll need a lot of power to get the volume on stage. If you want to keep the costs down then these http://www.bluearan.co.uk/index.php?id=FANSOV10-125&browsemode=category will be louder as a 2x10 than both of your cabs loaded with these cheap speakers. The Fanes do sound good as bass speakers too. You'll spend about £100 on four of these cheapies, Spend £50 each on two better 10's and you'll end up with a better sounding and louder cab for the same price and you'll only have to carry one cab. If you love it and want even more volume then you can go for a second cab when you can afford it. For £50 you can get these. I use the 12" versions and they are fab sounding. http://profesional.beyma.com/pdf/SM-110%20NE.pdf there's also the eminence Deltas and for a little more the basslites to consider.

Oh, I was looking for some monitors on ebay this morning and there are loads of bins on there of all qualities. This is a good time to buy, people are skint after Christmas and the bidding is often quite weak

Punctured? if there is just a small hole in the cone you can repair it by pushing as much of the fibres back into place then layer up a small patch on both sides using Copydex (a latex adhesive) and tissue paper. It won't be as good as new but it does work and lasts indefinitely as a fix. Alternatively this might do the job http://www.faneinternational.com/downloads/FANE_Studio_5FRK_Specs.pdf

First the actual answer to your question is that you will be approximately 2dB louder with the extra 100w, 1dB you will just hear and 2 you will notice but not by much, a bit like just tweeking the telly a little. Generally at any given price point I's go for a 2x10. They are likely to be in a smaller lighter box and two speakers are going to be be lighter than 4 in most cases. If the overall price is the same the two speakers for the price of four are going to be better quality, again most of the time. Knowing the techie stuff helps you home in on what to look at but the most important thing is to try them out and choose the one that sounds best. 200W through a high efficiency 2x10 should be louder than the drummer

[quote name='stingrayPete1977' timestamp='1356785858' post='1913560'] So why does anyone have anything more than 100watts? Why do barefaced cabs get a reputation for being power hungry etc? [/quote] Amplifying electric guitar or bass is a matter of design philosophies and compromises. If you are amplifying double bass or an acoustic guitar then you are usually trying to get a 'natural' sound but there's nothing natural about amplified electric bass. All speaker design is a matter of compromise. For example you can have a speaker that goes deep, you can have a speaker that is efficient and you can have a speaker that goes loud but you can't have all three because they place different demands upon the voice coils, magnets and cones. I'll explain: To make a cabinet go deep you need to add weight to the cone and put in a long voice coil to get the extra movement. A heavy cone is harder to accelerate so the speaker is less efficient. The longer voice coil means most of it will be outside of the magnet gap and you lose more efficiency. To make a speaker more efficient you can make sure all the voice coil sits inside the magnet gap so all the electrical input is used, but as soon as you put a signal in it moves out of the gap and the speaker starts to compress and distort. the deeper the bass the more air you need to move so if you want to get efficiency this way you have to limit the bass response and the power you feed to the speaker. To get the cab to be loud enough you're going to use a lot of speakers or put up with bass being limited. The one positive thing you can do is to increase the size of the magnet, There's a limit to this though, partly because the cost gets to be extraordinary and also the weight becomes significant, Eventually you also have problems with saturation of the pole pieces and so it goes on. The advent of neodymium magnets has given us a bit more wriggle room and new opportunities but at significant cost. Designers like Barefaced have grasped the opportunities of new materials and cheap amplifier power. By using long throw speakers they can get more sound out of single drivers and they can get deeper bass without compression or exceeding the limits of speaker movement but the 'cost' is very good drivers, which are expensive, and long coils which are by their nature less efficient, This isn't a problem in a world where you can buy lots of watts for relatively little outlay. The big plus is a versatile sound and light weight. You could take a completely different design philosophy though. Since the whole sound of electric bass is artificial anyway then go for the distortion, embrace the 'natural sound' of 'under-powered' valve amps driven hard and the 'louder' sound of a short voice coil in a speaker with prominent peaks in the bass and mid-range. Valve amps are pricey so you are stuck with low watts or an overdraft but you can spend on extra speakers to give you more sound for your watts. You'll lose deep bass and your top end will be restricted by the problems of multiple drivers but you'll have the classic sound of rock and incidentally the look which 'modern' designs probably still don't quite achieve. These design philosophies are only two of the options though. BFM designs for example use horns to raise efficiency, which imposes a different set of compromises and there are other conventional designs which just set the compromises in different parts of the spectrum.

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.

[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

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