PBSONG.COM SPEAKERS (THE BUSINESS END!)

This is where I post a load of speakers info, X-over & wiring schematics, cabs, and all kinds of useful stuff about what makes you sound good, bad or just plain painful!

Schematics and cabinet designs here are free and offered on the understanding that you do know what you are doing when you take the case apart, or when you put components together! If it blows up,.. don't blame me, I have worked with these diagrams and actually take them out on the road. If it still don't work, you have what is known in my place as a SNAFU! (If it's still smoking after a few seconds,.. it's FUBAR!)

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Courtesy of CELESTION

Click on the pic for the whole book!
The impossible to find "Handbook",.. very useful!

FANE CABINET PLANS
..from the FANE website, these plans for modern cabs are in PDF files to view in Adobe Acrobat reader (download Adobe here) and are pretty strightforward to build, provided you have reasonable woodworking skill and sensible tools. You can make these with only hand tools but I don't suggest you try unless you have a heck of a lot of time to spare!
10" TRAPEZOID CABINET (FULL RANGE)
12" TRAPEZOID CABINET (FULL RANGE)
15" TRAPEZOID CABINET (FULL RANGE)
125 LTR 15" BASS BIN
200 LTR 18" BASS BIN

(I have had so many questions about PIEZO wiring,
here's my page link, works with most designs.)
Wiring PIEZO HORNS & TWEETERS

You might ask why I have only mentioned these two manufacturers. The answer is really quite simple, I've seen their drivers over a number of years in all kinds of kit. Celestion are often found in guitar amps of all makes and types. Remember the Orange 'W'bass cab that was all over stages with bass rigs a few years back? Well it's origial version is in that handbook. Then of course, how many Marshall cabs are out in the wild? (Not to mention the others!)
Fane speakers are and have been for years, the front end of literally thousands of PA and disco rigs. I've put a lot of Fane drivers into a lot of very different rigs and never been disappointed at the results.
There are many more expensive makes out there but to be frank, these two maufacturers are the best at surviving life on the road. Proof of that being the very fact that they are still out there, in much higher numbers than any other maker!
If you are going to make your own cabs, you simply won't beat these designs, or the drivers they were intended for.
You will notice that all of these are, by some standards, 'low power' but remember, it's not the number of watts you put out of the thing, it's the efficiency of the speaker and you will be surprised at the performance from these if you build the cabinets carefully and pay attention to good quality wiring. If you want more power, just add more bins. Putting a much higher rated driver in these cabs won't do anything positive for the sound quality, or the actual sound level for that matter.

Have fun with these and save yourself a wad in the process!

You can always email me and ask for advice,.. provided you have a sense of humour and a thick skin!

I do very occasionally make up binz for people,.. I don't do it for free and I don't cut corners on materials to save costs. Some fairly well known manufacturers have copied my bins in the past,.. still do. I don't really care and I still like mine!

Guy goes into a Hi-Fi shop and buys himself an average stereo system, nice pair of speakers and an amp that puts out a hundred watts RMS on each channel. It sets him back a fair few drinking vouchers and he's quite proud of it so he goes over to his brother's place to brag about it. His brother has also been down the town and got himself a new 5+1 system that puts out a measly ten watts RMS per channel, plus a fifty watt bass bin/amp, which he has hooked up to his old cheap CD player. It has really silly tiny speakers and they are hidden round the front room but at a mere couple of degrees up on the volume control, it sounds ridiculously loud and amazingly clear,.. first brother is actually a bit less than impressed by the fact that this cheap pile of plastic junk sounds so good.

There is a point to this,... I run a PA system that is less powerful than most rigs but I still get enough level to fill a decent sized venue, even open-air gigs. When I say it puts out just over 2K, I sometimes get odd comments from other sound techs,.. most of them not really printable here. I also get a fair few comments on how clear the sound is,... from punters who know nothing about the size or power of the rig (probably don't care either) and the reason is not the number of watts it puts out but the design and type of speakers I use.
Over the past few years, gig sound engineering has fallen prey to the "boy-racer" syndrome in that every upgrade of a rig gets more power added and most rock PA rigs now pack a hefty 5K plus. Five THOUSAND watts of power?? Why? For those of you who have gone out an' blown megga wads of hard cash, or hocked yourselves to the banks, yer favorite auntie/uncle, 'God-father', loan-shark etc., for such massive power,... stop reading here, cos I'm really gonna get up your nose! Raw power is not and never has been the answer for good sound systems. There is a stupid myth going on in the PA world and if you have been really proud of your 1,000 watt drivers,.. you really should have listened to your physics teacher in school, there are some very basic laws that make such speakers a pretty awful waste of money!

I don't suggest you try cutting up your loudspeakers to see how they work, so I have got this pic from Celestion's pages, (well worth a visit) so you can see what's going on inside without an angle grinder!

Still here? OK,.. a loudspeaker coil is made up of fairly thin copper wire, if you pump lots of volts into it, three things happen,..
1, Because it's a coil of wire, it generates a magnetic field of it's own, the polarity depending on which end of the coil is positive.
2, Because it is sitting in a magnet already with a fixed polarity, it moves. and the speaker cone moves with it making the air vibrate and hence it makes noise.
3, Because the wire is thin, the more volts you put into it, the more current will flow and it will get hotter. If you push the volts up too high,.. it will get so hot the copper will burn out and all sound will cease. This usually happens during the most amazing guitar solo with devastating silence following a brief unintentional crunchy sort of noise with,...
"'ot th' 'uc' w' 'at?" from the vocalist

You might also notice that when you switch on a light bulb that puts out very few watts by comparison, it gets really hot. Exactly the same thing happens to your loudspeaker coil, it also gets hot. Ah,... when you heat up a magnet, it's magnetic power falls off quite sharply so that means as your poor little coil heats up it gets less effective. Not only that,.. if you heat up any conductor of electricity, it's resistance goes up. At this point we are out of accoustics (fluid mechanics) and into thermodynamics and the relationship between thermodynamics and fluids throws up a whole rack of interesting maths and technobabble that will bore the pants off you so I'll try to keep it simple.
As your speaker gets hotter, its power handling becomes less to do with sound and more to do with survival. As it gets hotter, its tone quality will alter because the resistance of the coil is changing relative to its now varying inductance and that gives you a rather random tone shift. This means that the money you blew on graphics and a spectrum analyzer is irrelevant now! As it gets hotter, the cone will not move as far for a given input because the magnet is not as effective and less current is flowing anyway. There is a sort of balance point and it starts to come in at around 250 to 300 watts. Over that level, coil survival becomes more important than sound level output (SPL) in the design. Then there is that thermodynamics thingy that also gets into the air round the speaker. As the air heats up, the way it transfers the vibrations of sound alters as it changes density, the density of the air changes quite fast with distance from the coil and thus with changes in air temperature, the resonant frequency can also change. If the air is getting hot it tends to try and travel upwards (convection) and for the speaker cone trying to vibrate it, it's a bit like trying to handle a wet bar of soap underwater in a jacuzzi.
If you want to hear my honest opinion on the sales blurb for these high-power drivers,...
click HERE

"SPEAKER LEVEL COMPARISONS"

Interesting point to note here is that you will see the power handling of a loudspeaker in the specs,.. but the sensitivity is the one you SHOULD look at because that is the one that tells you how loud the thing really is. Funny thing here is the level they test that bit at,.. 1 Watt at 1 Metre, and this gives rise to some very enlightening comparisons. the smallest change in level the human ear can detect is 1dB and when something is "twice as loud" it is only 3dB up on the other level. So here I will show you the characteristics of three speakers you can go out and buy "off the shelf" all are 12 inch drivers.

Speaker A,
Sensitivity: 99dB @ 1 watt @ 1 metre
Power handling: 150 watts
150 watts = 21.8dB above 1 watt
Max output: 99dB + 21.8dB = 120.8dB @ 1 metre

Speaker B,
Sensitivity: 98dB @ 1 watt @ 1 metre
Power handling: 300 watts
300 watts = 24.8 dB above 1 watt
Max output: 98dB + 24.8dB = 122.8dB @ 1 metre

Speaker C,
Sensitivity: 90dB @ 1 watt @ 1 metre
Power handling: 1000 watts
1000 watts = 30dB above 1 watt
Max output: 90dB + 30dB = 120dB @ 1 metre
(this measurement applies in an ideal world,...
in other words it's theoretical and in reality is not quite there!!)

So if you look at those specs, you will see that a very popular 1,000 watt driver is in fact not as loud as it's cracked up to be,.. quieter even than the cheapie 150 watter albeit at a mere dB-ifference only dogs or bats could appreciate, particularly at those levels!
If you add to these specs good cabinet design and by that I mean efficient cabs for the drivers, not just a tarty looking box,.. you will have enough sound level to get praise from the audience and complaints from "neighbours" half a mile away and save yourself a small fortune too! Bear in mind the fact that with that 300 watt driver flat-out, you are actually into the levels of sound that really do damage ears and it's over the threshold of audio pain,..
Oh you just bought the big *** bins,.... oh well, never mind!

I also use a slightly different way to get the sound around a venue,.. I use back-fills, by that I mean having a couple of speakers at the back of the place as well as the main stacks. This gives a better overall cover of sound with far less mechanical effort. (Less watts) It also means that feed-back is not going to be a problem and the graphic doesn't need a couple of octaves of vocals dropped into the mud to get round the screaming banshees in bigger systems.

Help for the wise,.. caution for the not-so-wise!