Phil Starr

To be honest I won't pretend the search for a driver was quite an objective trawl through every available 12” speaker. We’ve all built cabs before and between us had a number of 12” drive units sitting around to try. We had a fair idea of what we were looking for, though if we had turned up a speaker dramatically better we would have used it. For clarity I’m making our search look more systematic than the process probably was It makes designing more interesting though when you know you have to justify your decisions to other people who probably know more than you, and who won’t mind saying what they think! The first thing to do is to trawl through the spec sheets, keeping a sceptical eye open for manufacturers over optimistic claims. There are two things to keep an eye open for; the overall ‘sound’ of a speaker is determined roughly by its frequency response, and the bass performance by the design of the motor cone and suspension. Most speaker manufacturers publish the frequency response as a graph http://www.eminence.com/pdf/Kappalite_3012HO.pdf The thing to look for in the frequency response is the shape of the graph above 1000kHz, which is where our ears are more discriminating in what we hear. Below this the shape also depends as much on the box as the speaker itself and they aren’t all measured in the same box. If you look carefully on the spec sheets there’s usually some small print to tell you how the tests were done. The first thing is to see how high the response goes, if you don’t have a decent output (within 6dB) up to 3000Hz then your bass is going to sound as if the tone control is rolled right off before you start. A lot of 12” drivers are designed to be the bass unit in a PA speaker so they don’t need any top and you can reject all of these for a single speaker design like ours. Ironically if the speaker says bass driver or LF it probably isn’t going to work as a bass guitar speaker. Ideally I’d like an output within 6dB up to at least 4K. You’ll see two types of response. All speakers have a fairly smooth responset up to 500Hz ish which we think of as mids then the response starts to wobble. This is where the cone won’t work any longer as a piston, usually starts to flex and and resonate, and more of the sound comes from the central part of the cone. Depending upon the cone design the response will either bulge upwards by a few dB’s falling off at somewhere over 2K or be fairly even, with a bit of a wobble. The bulge is really useful for adding colour to the sound and most commercial speakers have the upper mid bulge, You have to decide early on whether you want a coloured ‘old school’ sound or something more neutral. To predict bass response I like to look at three parameters in the spec sheets, [b]Fs[/b] is the resonant frequency and tells you how deep the speaker will go. It isn’t an absolute limit but once you put a speaker in a cab it will start to droop in bass output around and probably above this point. The next thing to look at is [b]Xmax[/b] (and Xlim if the manufacturer gives it). Xmax is about how far the cone can move before the voice coil moves out of the magnetic field. This is important because the sound will distort and compress at this point. Be careful because different manufacturers have different ways of specifying Xmax. Some simply measure the magnet and the coil which gives a worse case Xmax, others like Eminence give Xmax under a certain level of distortion which makes them look a bit better but, to be fair, a bit more ‘real world’. Where we could we chose to use the voice coil overhang measurements but they weren’t always available. If Xmax is low (3mm or less) the speaker isn’t likely to handle a lot of deep bass without distorting at high sound levels, so we wouldn’t look at these for bass unless we were designing a multiple driver cab. The next thing we looked at is a weird parameter called [b]Qts[/b]. I won’t try to explain it here but a high Q (above 0.5) means the speaker is poorly damped. It will only give a flat response in a big box, in anything of a practical size it gives a big bass hump arund 100Hz and will sound warm, woolly, and very old-school. A low Q speaker (below 0.3) is going to be well damped. Just like a sports car tracking the road it is going to track the bass well, but the bass output will be tight and fall in output from quite a high point above its resonance. Just right for this bear is around the 0.35-0.4 point. By and large a powerful magnet creates low Q and better damping of cone movement so low Q speakers are more expensive and heavier. The last thing to look at when choosing a speaker is the efficiency, how much sound you get for a watt. This is usually given as dB/W. Look at the graph ideally at the flat bit below 500Hz which gives a better idea of bass efficiency. Most manufacturers give an efficiency which includes the midrange humps and bumps, this makes their speaker look better than others that don’t use this trick. Nearly all the speakers we looked at were around the 95-98dB/W mark and there wasn’t much variation in sound levels once we modelled them. So taking all of this into account we came up with a shortlist of candidates, which had to go up to 3kHz, have a Qts between 0.3 and 0.5, an Fs of less than 55Hz and an Xmax of at least 4mm. All the speakers we looked at had an efficiency above 94dB/W. I’ll run through the choices we modeled next time.

Hi, this is a 'diary' of how we are designing our 1x12. It is a bit behind the actual discussions we are having but I'll catch up as quickly as I can. I’ve posted this in response to our earlier thread. Three of us at Basschat (Stevie, LawrenceH and myself) have decided to publish a series of open source cab designs and people asked us to describe how we created the design so they could follow our reasoning. This is going to be the design diary for the 1x12. The first decision was which cab would be first. I initially suggested 1x15, a 1x12 and a 2x10 as initial projects. Stevie and Lawrence were both planning an 8” cab so that will be added in as an early design and there was some discussion about 2way designs. In the end the decision to go for a 1x12 was an easy one. We’ve got a range of 12” drivers around and a single driver in a straightforward box makes an accessible start to home building. We should be able to come up with a design that will keep up with a drum kit on its own and be enough for small-medium gigs. Adding a second cab or building it into a 2x12 would cover most people’s needs. Initially we didn’t have a design spec, but what has arisen through our discussions are these: Capable of keeping up with an unamplified drum kit (120dB across most of the frequency range) Compact (60l or less) Neutral /clean sounding Easy to handle Good low frequency power handling Readily available components, and easy to build Value for money We didn’t specify power handling. The critical thing is not how big an amp you have to use but the actual volume of sound you can expect the speaker to produce before it farts out. If it is loud enough with just 50W then this would be a positive, if it handled 1000W then it would probably be loud enough but fail the value for money test. As it happens nearly all 12's handle about 300W and have similar sensitivity of about 95dB/W. Easy to handle ties in with weight, but also size and proportion. You need to be able to lift your cab, but it also needs to fit through doors, including car doors, and not drag along the ground. We decided that 60l was the biggest our 1x12 should be and this would intrinsically make the weight and size manageable. Good low frequency power handling is a difficult thing to define. Almost no commercial 12” design will go down to low B at -3db or better and be capable of that at 120dB and ours won’t either. ( I don’t know of any commercial bass speaker that will but someone else will) What we are looking for is something that won’t shake itself to bits at high power and reproduces low E cleanly and at a decent level. We also want to see something that can handle a decent proportion of its rated power without distorting . More about this later. UPDATE A lot of information has been lost in the last couple of years with changes to both this site and Photobucket which I put my old pics on. If you want to build these cabs I've retrieved the dimensions below. I need to go back and see if I can come up with something better when I get time but it ought to be possible to build one of these cabs from just the dimensions. If you want to do a build PM me and I'll fill in any details Members 60 2,401 posts Location: Chard,Somerset Report post Posted July 8, 2015 If anyone wants to start a build before I've had time to write this up and get drawings done it shouldn't be too difficult. The cab is constructed out of 12mm ply and fitted with a Beyma SM212 driver available from Blue Aran and others.The external dimensions are 360x424x530mm the baffle front is set back 30mm from the front of the cab so internally the depth is 306mm. The four ports are made of standard guttering downpipe 190mm for a 50Hz tuning, and 260mm for a 40hz tuning. All this information is elsewhere in the thread but it's probably hard to find. I'll cut and paste the important bits later but everything is there below including some frequency plots measured from the prototypes.

OK, update time. We have decided to go for a 1x12 as a first project, a 50l cab, 300W@8ohms, should be capable of producing 120dB@1m across most of its frequency range and hence capable of keeping up with an unmic'ed drum kit. It should be a comfortable one handed carry for most of you. The current design is going to be fairly neutral sounding and should have good control of the lowest frequencies. The design has reached the stage of moving to build a prototype and we have a list of drivers to audition. We are currently looking at the port design and there is some debate about the significance of wind noise (chuffing) in the ports versus the ease of build and overall size and shape. We will resolve this by tests on the prototype as well as deciding on the final choice of driver by auditioning a number of drivers. At the moment we think it should be possible to build a high quality 1x12 for around £150. I'm going to start another thread to talk anyone who is interested through the design process, once I catch up it will develop as we do.

[quote name='skidder652003' timestamp='1390071487' post='2341206'] you've heard the old tosh we churn out Phil, you only need one bass for rock mate, guitards now using a Les Paul as well as the strat and it drives me nuts with the swap overs, we've told him to do it as little as possible and let us (me and drummer) start some intros while he does, but what with his reluctance for a set list ( a whole other thread!) its all becoming a real issue with the tumbleweed blowing between numbers ( I have no stage front craft) [/quote]We all love our guitarists, don't we. I don't play anything that needs a dropped tuning or 5 strings and you are right about breaks between songs. It's going to be one bass for me then with the spare being just a spare, although I've never had a failure.

Just on the physics of the thing heat and temperature aren't the same thing. A bigger amplifier will produce more heat but will be designed to radiate it through a better heat sink so the temperature rise should be the same, it is temperature rise that challenges your components. Any decent amp should handle full power forever, so unless you set it up on an Aussie tennis court they shouldn't blow. If is did overheat the protection circuitry should cut in and limit the power. It won't matter to the heat sink what frequency is using the power and the only problem with lows this deep is that we can't hear them and start boosting the bass, meaning we go right up to the limits. As you normally cut the bass a little this shouldn't be a problem. There's a slight comment about your eq and what you are trying to achieve. If what you want is just a hint of clean lows a thumpinator or other filter works better than a tone control. A lot of these filters work at 24db/octave, most graphics are a lot more gentle than that. Knocking everything below 30Hz will mean your speaker coil stays within the magnet gap which will improve the sound at all frequencies as well as improving its reliability so a sharp filter with your tone control back to neutral may give you more deep bass and a better sound all round. in the end though it is difficult to produce these frequencies without setting off all sorts of room resonances.

Thanks guys, I think you are confirming mainly what I feared, that we are the only ones that really care. I think I prefer playing the Jazz and it sat nicely below the mix in my old pop band, I even used flats then. With the new band the P-bass which is active and has a bridge pup can do most of the tones I need and sits well with the band. looks like I'm a P basser after all.

OK I'm a lucky guy with the luxury of choice. I have two 'good' basses that I'm really comfortable with. A Highway 1 Jazz and an American Deluxe Precision. I had no intention of being a Fender man, if you'd asked me three years ago I'd have said you get better quality £ for £ almost anywhere else, but these two came up cheap, I couldn't resist and they both play and sound great. I'm happy with the basses but my question is what to do live? There's little doubt in my mind that the P-bass sits better in the mix for most of our songs (Indie covers mainly) For a few songs the depth of the Jazz works better. At home the Jazz sounds so much better, to my taste anyway. I take both to gigs, just in case. I take spares of everything critical, even PA speakers. So, should I start swapping basses? I hate it when the guitards swap instruments, particularly when one puts down the acoustic to pick up an electric whilst the the other swaps to pick up their acoustic. How important is having the right tone compared with continuity?

This is the other main supplier http://www.bluearan.com/

[quote name='largo' timestamp='1389622159' post='2336178'] I think a standard "rectangle" box with an upward angled baffle & speaker behind the grill is a great idea and wouldn't affect cab depth too much. It only needs to point upwards maybe 10-20 degrees, not 45 or anything. And a bug bear of mine, a cab that's wide enough to sit flush with a standard 19" rack-mounted amp. That's all, cheers. [/quote] Funnily enough we were discussing the need to match the 19" amps this morning. It's an ideal and it does make stacking cabs easier but tricky to achieve with smaller cabs. If we can we'll do it but how much should we compromise the sound?

[quote name='Beer of the Bass' timestamp='1389620690' post='2336159'] Would that be using the Faital 8" drivers that a couple of the US builders are using? I think my interest was piqued when I saw that the displacement should allow them to get as loud as many 10"s. Given that a 1x10" does me for a lot of my playing, and I use buses a lot, this could be very much of interest to me. [/quote] We're talking about a number of drivers for all the designs, There's the Fane 8-225 and Precision Devices do a lovely 8 with great extension at the sacrifice of sensitivity. the trick is going to be to home in on th best drivers in their class

[quote name='charic' timestamp='1389610388' post='2335992'] How about a home practice cab? Takes the full wattage of a gigging amp (mines 1kW) but is small and doesn't risk damage (dummy load or something may be the easiest way I guess?) [/quote]We're quite keen on a home practice cab, something small and unobtrusive but with a satisfying sound at the sort of levels you will practice at. There is a technical problem with something small built to handle 1000W though. Heat dissipation. Small speakers have small coils and less metalwork so don't handle such high power before burning out. The simplest thing would be to turn down of course, 50W into a decent speaker is going to annoy the neighbours quite enough anyway. It would be possible to wire a 4x6 for example so it ran at 32ohms and your amp would only drive 125W into that or a 16ohm 2x8 could be made to handle 200W easily enough. It's more likely we will come up with a 1x8 design for this purpose, but it won't handle quite that much!

OK to come clean part of the inspiration for this was 6V6's build. You can see it here [url="http://basschat.co.uk/topic/200152-1x12-diy-cab-build/"]http://basschat.co.u...-diy-cab-build/[/url] if you see the thread I gave him some advice and the rest he worked out himself. I have a similar cab myself and with both of us happy with the result I have the confidence to go ahead and recommend it to others. So apologies to 6V6 he'd be better off sticking with his own design. So, the designs I am picking up so far are: 2x12, we'll include dimensions for this in our 1x12, for people who only want to make 1 trip to the car. 1x15 I'll probably do next Vintage voiced/coloured cab we intend giving alternative driver recommendations for all our cabs together with any recommendations about modifications needed to make them work well. Some of these will have a 'modern' smooth voice and others a warmer more coloured voice, so you will make that choice. Really compact practice cab You can see Lawrence is keen on that, so he will probably come up with something fairly quickly. I'm also playing around with some designs based on a 6" driver so that might come to fruition Upright Bass cab, sadly my wife would probably kill me if I started to learn upright as well as waste all my time in the shed, but as a design challenge this looks really interesting and is completely new to me, I'd love to have a go but I'd need an upright player close to me to work with. Then there's a few points I'm picking up about angled cabs, reggae cabs and cabs with deep bass extension. I'm toying with the idea of building a 'bright box' to get the sound to your ears which might be interesting, I have a couple of designs I'm mulling over. Designs for more specialist tastes I'd love to do but they will have to wait. We also have a problem with funding this. We can't develop cabs without the drivers to hand. This is fine if we are to use the cabs ourselves but I personally can't afford to buy stuff I can't use. There's a load of other things you mentioned, Stevie and Lawrence have answered some of it. We'll write up a commentary to help others design their own cabs. I won't be making comparisons with anyone else's work/designs. It wouldn't be a good thing to do and we just want to do some technically competent designs that others can copy. If we get hate we won't respond that's their problem. I'm sure we will make mistakes and if people can correct them then it would be great to work with them. It's the joy of open source. We are deliberately starting off with simple designs, Stevie and Lawrence are keen to get on with multiway designs and they will come but I have no immediate plans for anything with a crossover, we'll see how it goes. Hope this helps

Keep all the suggestions coming in. You'll see by the time that it is late, so detailed responses will have to wait until tomorrow but there is plenty of food for thought here. We won't be able to do everything in a single design but we will be able to say what compromises we've made and why.

A small group of us (Myself, LawrenceH and Stevie) are working together on some cab designs which we will make available free of charge to Basschatters. At the moment we are working on a 1x12 which should be an easy build, cost about £150 and will keep up with an average drummer fairly easily. We will go on to look at other designs. We'd like to open it out to you all, what would you like us to have a go at, what designs would you like to see? What would your ideal speaker sound like?

The clue is in the word .A crossover splits the signal so that below the crossover frequency the sound goes to the bass unit and above crosses over to the tweeter. The system will be 8ohms all the way but you can only do this with a crossover and it has to be the right one. Using the horn you suggest will still make little or no difference to the sound compared to not having a horn, it simply doesn't cover any of the frequencies important to bass. The piezo probably comes in at around 3.5kHz so it does cover some of the top end and will contribute a little to the sound.

There's little point arguing about all this. If any of the places you play are places of work they have to have health and safety representatives by law and these are governed by statute http://www.hse.gov.uk/involvement/whatdoesthelawsay.htm. In addition they have to be covered by public liability insurance and to get this the insurance company may impose conditions like PAT testing. It's all mainly due to fire risks, half the fires in the UK are started by electrical faults. Anyone not fulfilling these duties could potentially go to prison for anything up to life if someone is killed. I'd offer little for your chances if you had stuck a few labels off the internet onto your cables should you end up in court. Faced with criminal liability I'd ask for PAT testing, so someone else took the responsiblity. You can't blame the venues. We don't get our gear tested, I'm not being holy about this. We only do a dozen gigs a year and the cost puts us off. No-one to date has ever asked but if they did then we'd have to do it or turn down the venue. It's a bind but it isn't unreasonable or pointless any more than MOT'ing your car. Like an MOT it's no guarantee the car won't go wrong tomorrow but it's safer than never checking at all. The really bad advice is to fiddle the system or to lie. It's probably something we should all do but to cheat the system is to take all the responsibility upon yourselves, Just as you would driving a dangerous car with a fake MOT.

OK to make it clear, there probably isn't a crossover, it's the main cost saving you get by using a piezo. There probably will be a couple of big white resistors and maybe a capacitor just to match the output of horn and bass unit. To be safe remove the wires that run from either the main speaker or probably the amp itself to the horn and any associated components leaving just two wires going to the two terminals on the speaker itself. Don't leave any loose wires to touch anything and it should be safe enough. If there is a problem then put up a photo and we will advise. Bill is right though about the tweeter, There is virtually no energy at all above 5kHz where the horn you suggested using starts, so little or no point in adding it unless string noise is something you look for!

If you just want to monitor on stage then a little kickback combo will do the job. I use the discontinued Hartke 10 for this and it works well. Roll back the bass a touch on the Hartke and you will get the rest loud enough. A powered wedge will do the same with a lower profile but check it is happy with bass giong through it. If it really is just for monitoring then you don't need to carry anything more than this, a 4x10 would be just too much to carry and why have a separate amp and extra wires? However If you are buying something to do this anyway would it be sensible to buy something more versatile? Something you could use on its own if you get to play in other bands where a stack or a decent combo would be more appropriate. It's a choice only you can make; something small and simple that just does this one job, or something bigger heavier and more versatile. I've ended up with both.

Yep, you can't replace the piezo with a dynamic one, they work entirely differently. the piezo has a high impedance that rises at low frequencies to the extent that it doesn't need a crossover. Put in a 8ohm dynamic without a crossover and it will blow at the first loud note. Disconnecting the piezo is just a matter of cutting a wire or pulling off a spade connector but you need to make sure the wire ends are insulated so they can't short out accidentally.

Funnily enough I've been wondering why more people don't offer something like this. The potential for a smaller cab and better handling of real lows is appealing, at the loss of bass efficiency to be fair, but it is all about trade off. If anyone was interested in building something and wanted help with design then it'd be an interesting project. I'd be happy to be PM'd.

Get a little mono mixer like this [url="http://www.maplin.co.uk/p/3-channel-mini-microphone-mixer-l71ak"]http://www.maplin.co.uk/p/3-channel-mini-microphone-mixer-l71ak[/url] others available including ones in stomp box cases.

First of all don't worry about where the controls are set, Different amps have different levels of gain which have little to do with overall volume. Read this isf you haven't already [url="http://basschat.co.uk/topic/3730-gain-power-and-volume-a-confusing-menage-a-trois/"]http://basschat.co.uk/topic/3730-gain-power-and-volume-a-confusing-menage-a-trois/[/url] If the bass was too loud then it is loud enough. It isn't extra watts you need. I'm concerned that the clipping light is flashing though i do know some amps are set with the light more sensitive than others so check the manual. I don't know the Peavey amp so I'm not clear what the light signifies. One explanation may be that you are using a lot of bass boost. This won't make the amp louder as we judge this mainly by the level of the mids which our ears are much more sensitive to. The deep bass is what eats the power though and just a touch (3dB) of bass boost will demand twice the power from the amp. Bass boost to 3 O'Clock and you might be asking the amp to give 4x the power. This might be a problem. I'd live with the Peavey before you rush out to change everything. Can you get the tone you want? Have you asked your engineer if the bass was just too loud or was it too bass heavy. It's all but impossible for you to judge your tone from the stage area, you need to be out where the audience are.

Wiring live to earth isn't a great idea and you need to get it rewired. It may even have been shorting out internally and confusing the cable tester. I'd also suspect the Di box if it wont clear. If it was all working perfectly up to then it does ask a few more questions and it is difficult to diagnose without the stuff in front of you. However, if one lead was reverse polarity and you had this on one speaker and the other spoeaker is wired normally then they are out of phase. One speaker moves forward at the same time the other moves back meaning at bass frequencies they move no air. One is sucking the other blowing. This does sound weird, completely lacks bass and that may be what you were hearing.

I wouldn't use linseed oil on a bass, it is too sticky really, and forms a gum as it dries. I like the finish but it is strictly for furniture and cricket bats as far as I am concerned. If you do use it then use boiled only and very sparingly, better still use something made for the job with either a lemon oil or a mineral oil base. They will usually have a mix of oils and a drying agent or two in the mix. May cost you £6 for a tiny bottle but it lasts for use as you use so little anyway. I use Dr Ducks and after 6 years it is still 3/4 full.

It would be a shame to ruin a vintage amp by playing bass through a guitar speaker, especially if it is in original condition. You will almost certainly shorten the life of the speaker by playing bass through it and probably destroy it unless you play at very low volumes. Please don't do it.