Phil Starr

Sounds interesting, It's amazing how little real bass you can get away with sometimes.

Ha ha I shouldn't have gone to the gym, now it's got complicated, but everything people are saying is about right. mains in this country (UK) and across the EU is 230V nominally, but that varies depending upon where you are along the power line. Our house averages at 242V. So theoretically 230w is 1A but the general calculation that 250W is 1A is good enough. There's two considerations here; you don't want to trip the fuse and you don't want to set the internal wiring alight! Most household fuses are slow blow to avoid them going every time we turn something on, most stuff in a house takes less power as it warms up. Steve browning has asked the crucial question, what is my amp using when it is on 3? That's amazingly tricky to work out. If you are damping your strings properly there's a lot of time you aren't putting out any sound, all your notes start loud and then decay etc. The 300W or whatever are simply the top limit you hope to never get near. Then again the amp isn't 100% efficient. Switch mode power supplies are better than transformers, transistors better than valves. Modern electrical appliances now have to have an estimate of average power, have a look on the back of your amp if it is recent. My 500W Peavey says 160Wh electrical consumption so that's an average of 160/230 of an amp when it is run quite hard, about 1/3 of the 500W max output. The next issue is the inflated watts that are advertised, for calculating currents you need good old RMS watts (that's where the square root of two comes in, RMS=root mean square) Most single speakers only handle 300W as a rule of thumb so that 1000W Yamaha PA speaker is actually only 500W at best and needs less than 200W of electricity an hour. SO add up all the watts of all your amps/lights and so on and allow 4amps for every 1000W. If you are using solid state amps class D or otherwise and LED lighting then I really doubt most pub bands will be using more than 3000W. You don't need a lot of headroom, as in my Peavey I doubt you'll be running at more than 30% for anything longer than a few microseconds. You only need a second socket if you go over 3000W and that gives you a big safety margin. If i have to go for a second socket I look for a twin socket. In a double socket the two sockets are connected by big copper/brass strips so they are properly earthed to each other by design. I don't trust electricians I haven't met as I've worked on building sites. Most are safety conscious but people make mistakes. If I have to split then I run one circuit for the amps and a separate one for lights and make sure no-one can touch the lights. Your mics are earthed through the PA so you need that plugged into the same earth as the back line. The final thing is to make sure your mains leads are in good condition. There's no point in trusting a single socket if anything you bring in has a broken earth. That's where a circuit tester will help, and use the RCD on your single socket if you think there isn't one elsewhere, though most venues will have regular checks for insurance purposes.

I always plug everything into a single socket. I've had problems in the past with floating point earths. This is where different circuits in a building are poorly earthed or sometimes not at all. That leads to the earth connections of some of the wall sockets being at a different voltage to other sockets. Since the outer metal parts of our gear are often/usually connected to earth that touching the metal parts of your bass and another metal object like a mic can lead to quite an unpleasant shock. It's relatively common in old buildings but I've even had the problem in new buildings. If your own gear is all sound and plugged into a single socket you know everything is at the same earth potential. With modern gear you are really unlikely to be drawing 13 amps (3000W) so overheating shouldn't be a problem so long as your cable reels are unwound.

For those looking for a really tiny speaker for home practice with lots of detail and a satisfying sound without neighbour annoying deep bass I built a 6" speaker. The details are here, it was just a bit of fun but if you live in a tiny flat it might just be interesting

This is probably the outside dimensions? What you need are the internal ones, I've never seen an Elf in the flesh (!) so I've no idea what those are but my best guess was the internal volume is nearer 27l allowing for the wall thickness and the baffle being set back. I normally just take a notional figure for the intrusions into the cab so I've been working on a nominal 25l as the volume of the Elf. I don't see a lot of point in designing a 40l cab for what you want. The 10CMV is fairly tolerant of cab sizes and you might as well stick to the BC Easybuild cab which is just over 35l. You need to decide the driver you want to use and how important size is to you. When you have a better idea I'll do a more detailed design. We ought to start a new thread though.

Hi John, this is the Fane (purple) in a 25l cab against the Beyma in the same cab tuned slightly differently to get the flattest response. The Fane actually 'needs' a smaller cab to get the flattest response, around 20l. -3dB is 10hz lower and there is an extra 3dB at 50Hz so noticeable extra deep bass. There's a ripple I couldn't design out but no real peak. Which would sound best would be a matter of taste I think.

OK as a starting point here are the responses of the 10" Beyma CMV in a variety of cabs. 50l which is WinISD's first suggestion (green) the 12" Easybuild/110T cab (red) and the 25l cab you were hoping for (blue). You can see the 50l cab gives you a lot more bass and the flattest response the 35l cab gives -5dB @ 50Hz and the 25l cab significantly less bass and an audible extra warmth at 100-120Hz. If you went for this speaker in the smaller cab it is flat down to 80Hz which is important as it is the second harmonic that we mainly hear as bass. It's going to sound like a bass speaker but bass will sound light and fast if that makes sense. The Beyma also has a slight peak in the upper midrange so it should cut through quite nicely with a bit of 'old school' sound about it. The Eminence Legend would show a similar pattern of responses but it has a more significant upper mid boost which would give a genuine old school feel about the response. Essentially if you want extended bass in a small package you need a more powerful magnet system than these speakers have. hence the iron law about you can have small, cheap and loud but not all at the same time. However if you you don't mind compromising on the deep bass I think any of these cabs would 'work' especially for home practice where deep bass isn't really helpful. The SM110 was a better driver but as they don't make them....

here's the drawings of the 10.

The cab is essentially the same for both projects, there's a difference in the porting because I prefer the build simplicity of using downpipe which is so easy to get hold of. Stevie who designed the lockdown 10T prefers a bigger diameter (ooh err) to reduce port noise. The dimensions are deliberately small to restrict the bass out put for the 12 but Stevie always said the cab would suit a 10. The tuning of the 12 is also slightly higher. As to writing it all up properly, I agree but I already spend too long on bass chat and not enough time playing bass I'll get on to it but it might take a while.

Since it is you I'll have a look at the Beyma 10CMV. I was toying with the idea of designing a 2x10 as a next project and if it needs to be low cost then those Beymas look to fit the bill. It's little extra effort for me to give you a set of designs for a 1x10 and a 2x10 so you can then make your own choice as to what you want to build. The only thing you need to do is to put up plenty of pictures of the build and then to tell us what you think of the sound at the end. I know you'd do that anyway and it will be good to share another design without having to fill my house with yet more speakers and sawdust. I'll get back to you tomorrow hopefully.

Phase is a moderately complex idea, so for anyone not familiar. Speakers (anything making a noise actually) move backwards and forwards travelling fastest in the central position then slowing at the ends of travel before turning round and going back the the other extreme where they slow and return. That creates pressure waves in the air that radiate out into the room. At the back of the speaker the pressure wave is reversed and the air is pushed in the opposite direction. It is 180 degrees out and if you let it mix with the air at the front you get cancellation and no sound. Many other things can delay the sound including distance and the air can be any amount 'out of phase' or not at all so you can get anything from double the sound from an in-phase sound to complete cancellation (which is what sound cancelling headphones do) Any time delay in the sound leads to phase cancellation but the 'phase' is dependent upon the frequency of the sound. Higher frequencies go through more phase change than low frequency ones in the same time. In a ported speaker the mass of air in the port is bouncing on the air in the cab; it is resonating if it is in action and like a bass string it only does this at one frequency (sort of) The trick of the designer is to set this up so it does this just as the speaker is dropping off in its frequency response. Once the port starts vibrating it pushes back at the air inside and if you get it right the cone of the speaker stops moving and all the sound output is coming from the port. So at the tuning frequency you aren't going to get cancellation/phase issues. The speaker isn't making much sound at that frequency. Above that frequency the port output falls really rapidly so phase cancellation ceases to be an issue. Finally all this is happening at the very lowest frequencies the cab can realistically reproduce so the phase shift isn't great and frankly our ability to discriminate sound at those frequencies is really poor. Any issues would be swamped by room acoustics as the bass bounces off every hard surface (floors, ceilings and walls) and takes many differing routes to your ears, each far greater than the distance from rear port to the front of the speaker. That's why I don't think you can hear a difference and I'm completely with Bill on this one; if you want to sell a speaker put the port where people like to see it. People buy with their eyes. That's the simple picture (I'm sure the experts are wincing here at some of the generalisations but I'm trying to be clear)

I hope people building their first cabs at home aren't being put off having a go at building by this It's great to see a range of opinions though. You'll see different designers have differing opinions and the truth is many of us have 'go to' ideas we tend to repeat. The reality is that all speaker cab design is a matter of balancing differing concerns. In the case of port designs it is pretty much impossible to design a really compact high power cab with deep bass that won't have higher port velocities than you'd like. For high power, high excursion speakers you need a wider port to allow it to 'breathe'. Increasing port area for a particular tuning means the port needs to be longer and that both increases the volume of the port and takes it closer to the back of the cab. If you are aiming to have a compact cab then a port of several litres is obviously something to avoid. so you have to compromise. Equally if you have a small cab then the places to put a large port are limited, more compromise. Just look at the RCF PA cabs; generally recognised to be one of the best sounding units available at the moment. Every spare bit of space at the front is either port or speaker. This is just the port of course, there are other tweaks and compromises to be made: weight, portability, target response and so on. then there are practical considerations like the cost of production for commercial designs and the availability of parts for the home builder. If you buy a cab then you are stuck with the compromises chosen for you, if you self build you can add your own tweaks or accept the tried and tested designs so you have a bit more choice. You can see the difference in approach even in this cab. I designed the original box which had a 12" speaker and two smaller ports. That design choice was based upon having a lot of 68mm pipe to hand and the availability of a 68mm hole saw at a price home builders could afford. I check them but I'm not particularly concerned about port velocities as I rarely if ever find they are a problem with bass guitar. My design does chuff with test signals but has never made unpleasant noises with me at gigs (apart from my playing of course) even though it has a 12" driver with greater excursion and power handling. Stevie chose the most widely available and affordable ready made port and that won't exceed unacceptable port velocities under any conditions within the pass band. It's on the big side for a single 10 but it fits and it works. The tuning isn't an issue as that was done by measuring after the cab was built.

That's one of the reasons we use tube ports. It's a lot easier in the prototyping phase. Otherwise it's probably better to make the shelf undersized and add on rather than have to cut bits off. I prefer round ports anyway. The walls of any port are where there is resistance to air flow and where non-linear air flow starts to cut in. The way to have the least air in contact with the walls is to have a circular cross section. We also found that multiple small ports demonstrated earlier chuffing than a single large one. Not very scientific as it was a sample size of one but it was a very obvious effect. Having said that other considerations come in to play. I often use whatever port material I have to hand, either plastic plumbing pipes or cardboard tunes from carpet warehouses.. Some designers have used triangular ports in corners. They'll experience more turbulence but it's a really convenient place to put them and the triangular bracing of the panels will be significant. Stevie really doesn't like chuffing so uses large ports for preference. I don't mind high port velocities on the basis of the absence of much fundamental coming from the pickups. It's hard to say any particular design choice is the 'one' as all speaker design is a matter of weighing gains in one area against compromises elsewhere. We are really happy to go off topic, lots of people read the answers and learn stuff and it keeps us on our toes for the next design.

When I wrote that it was just clean , plugged straight into a high impedance input in the mixer with no EQ. The mixer is an RCF M18 so it has amp emulation built in but I wasn't using it. Today i was playing with my Zoom B1ON in the line and that sounded great too. I hope you love the C2

Well done, nice to see it is coming along.

where did you source the grille?

that looks great, I should have gone for the silver corners.

Hmm bathrooms are a good place for stinky poo

What we are trying to do is to introduce people to all sorts of ways of building cabs and encouraging them to experiment. At the same time we want to offer designs that will be satisfying to own and will work first time. We're also trying to give enough information that people can do their own adaptations. If somebody wanted to there is no reason not to build the 50l MK3 cab with the drivers and crossover Stevie designed but using the 'easy build' technique. Or you could build the cab we are discussing here with a circumference brace borrowed from the MK3, or indeed a rear port. If you keep the overall volume and the port dimensions the same you preserve the tuning so if you wanted a taller cab or one that matched your amp dimensions that's all possible. Everything we do on here is creative commons, we're happy for people to build the cabs for their own use or to build one for a friend so long as it is done on a not for profit basis. If anyone wants to put together a small run of CNC flat pack kits for BassChatters on a not for profit basis that's good too from my point of view. I'm not sure what the next project will be, I've got all sorts of plans but I need to clear some of my stinky poo out of the house to make some space. I'm also being reminded I have to fit a new bathroom

I've just spent the day playing through my RCF ART310s on poles they do just what you want, they sound like huge headphones. Nothing in the chain other than the mixer.

Back on track, thanks for this John, it's really useful to have an independent personal opinion. I have to say that this pretty much matches my own experience. I also rolled off the bass a tad and found the cab perfectly adequate for rehearsals. the basic sound is just a lovely open honest sound of the bass but I also added a little compression (and grit also). The band loved it. I'd also pretty much agree with the assessment of it's capabilities, 100+ would be beyond it as would anything outdoors. You'll find when you have two for PA it will sound a lot better than the single speaker. I do a lot of critical listening when testing speakers and listening in mono often shows up things you don't notice with a stereo pair and of course the imaging will do so much to the experience. This little speaker has given me a little doubt as to what I'm doing next. I've got the parts to build the 12" BC Mark3. I've been using bits and bobs of prototypes I've been taking to gigs for years and I wanted to have a go-to set up for important gigs. I've been using a couple of Beyma 12 based BC Mark1's for years. This BC 110T is so much better than it has a right to be and is so portable I'm now thinking of just having a second. Then I'll have two speakers I just won't touch for gigs and I can experiment freely with whatever else I have. For £125 and less than a days work it's tempting. Just a question of which one to build next.

Honestly I doubt that they do sound better, I can think of at least one good reason why they ought to sound worse but none which would make them sound better. There is no theoretical reason i know of that would suggest a difference and i doubt you'd measure any difference at a decent distance from the cab. You are then down to subjectivity/listening tests. The problem is proving a difference one way or the other. You'd need to build identical cabs with identical drivers and then carry out multiple double blind tests where neither the listener nor the operator knew which cab was which. The big problem is that our ears are connected to a big organic computer which processes the input from our ears and often functions to make us hear what we expect to hear. I've spent many hours doing listening tests when designing and building speakers and you'd be amazed how often you can fool yourself that you can hear something that isn't there or fail to spot something that is obvious. My wife assures me that i often fail to hear things which are important to her but rarely miss something important to me It isn't just our sight that is subject to illusions. To me ports on the back look wrong and I tend to avoid them even though I know there is no good reason to do this. The reality is that I've never actually listened to the same driver in a box identical except for the port placement. Maybe you just prefer some speakers to others and as not many have ports on the back it's just coincidence that you didn't like those as much as your favourite cabs So what could make it sound different but objectively worse? Firstly cutting a hole in the baffle weakens the part of the cab you have already weakened with the speaker cut out and the bit you need to be most rigid, you end up with a big heavy magnet fixed to a wobbly board. A weak baffle isn't good secondly the port itself has a series of resonances where the wavelength is a multiple of the port length. These are going to be more directional and could be audible.

If you don't mind building one of these would be ideal We've been looking at a lot of bass speakers and the crossovers are rarely done with a lot of care so that's probably what you are hearing. If you want to buy then it's probably best to skip bass amps most of which are 'voiced' in some way and go for a PA speaker. I use my RCF ART310's sometimes and they work well with bass up to quite a reasonable volume. Depends upon what your budget is of course.

Brilliant, I think this will be ideal for you.

Hi Bert, I would have thought it would be great for what you need. I designed it to cut the low bass and emphasize the upper bass/low mids. I think it would certainly do the Motown sounds quite well. However I'm not the words greatest tone freak or the best musician in the world (by quite a distance). I notice you are in Somerset so maybe you should come over and have a try sometime. I live just the other side of Chard