Phil Starr

Sorry but that is the wrong set of plans, there are plans for the Beta 10 and Beta 10B on the Eminence web site so if you want to assume that your speaker is one of those then that's the way to go. I did think of pointing you in that direction but you'd still be guessing as to which of the two speakers you might have or if Ashdown specified any changes other than the colour of the cone. What I suggest you do is build the cab but make the baffle/front panel removable. As you say this is a project and if the baffle is screwed but not glued then you can make changes to the cab more easily as you experiment. So the simple answer would be to build the BC110 30litre cab which is tuned fairly close to the original Ashdown cab. One 30l cab is much the same as any other and the only advantage of the BC110 is that it was designed to be easy to build and that makes is a good basis for building and experimenting within a project. in this case it's almost finished so no point in changing tack now. It'll work and do the job you have planned for it. You can then modify it if you think it has shortcomings you can fix. As an engineer you probably can glimpse the theory behind the design and probably want to start to get to grips with it. I'm sure we'd all enjoy discussing that with you but that'sa whole other thread

I modelled the cab with 50,40 and 30 Hz tuning, all f them work with the standard Eminence Beta but with slightly differing frequency responses. Because speakers in roughly similar price brackets tend to have reasonably similar performances it often happens that they will 'work' when swapped even if a little more performance could be gained by proper matching. Without proper specs I'm guessng of course but in this case I can't really expect problems.

Great advice:)

As you point out there is only one place where the fundamental makes the greatest string movement and that is the antinode. That's at the 12th fret for an open string but as you point out the middle of the string is different for each fretted note. (I realise you know this of course but others may not have looked at it this way) That made me ask the question: are there any notes where the fundamental sits directly over the pickups so I took a ruler to my bass. The answer was interesting: the 22nd fret on my Jazz bass is 28cm fom my bridge so the bit of vibrating string fretted there has the antinode/loudest point 14cm from the bridge and that is exactly where the neck pickup sits. It's more or less where the pickup is on my P-bass too. Coincidence or did Leo know something?t Anyway for any point along the sting we can work out how far the stiring will move for the fundamental and all the harmonics and you can work out a 'frequency plot' for every pickup position. We all know that there's less bass from the bridge pickup and you can get a bassier tone by picking strings further away from the bridge. To save anyone doing the maths there are bits of software on the web which will allow you to slide the pickups closer to the bridge or away from it and they will calculate and print out the signal. https://till.com/articles/PickupResponseDemo/index.html

Bill is well informed on this sort of thing so I'd be reasonably confident that this is a 16ohm beta. If you check the magnet size that should tell you if it based on the Beta. They'll work Ok in the 30l cab but with that tuning they are going to have a pronounced peak in output at 120Hz, 2-3db extra wich will give a very old school bass sound.The betas also have a pronounced upper mid peak so this is going to make a sound in the classic smiley face/midrange suckout territory. If you want that artificial warmth tamed a bit you can tune the cab a bit lower. That would entail using longer ports than that specified. Without reliable specs though we are in the realm of guesswork. It could be that you have one of these

I've probably said this before but I'd challenge anyone to listen to Feel It Still on that recording and say you can't do bass properly without backline. You really nailed that tone, and live too.

It's never going to be easy to get right if you are mixing from on stage. You can set levels on a sound check and as soon as the adrenaline sets in as the set starts the singer will up their volume. I've rarely met a singer who doesn't up the db's once the gig starts so you are always guessing when you set the levels. Volume for bv's also depends upon the song, there are parts when you want your singers to be the same volume and parts where the lead vocal needs to be heard over the backing. You might be doing call and return on one part of the song and want equal volumes, harmonies in another part and gentle oohs and aahs in the background later. Your singers need to practice their parts and control their own volume which is also an artistic decision. We rehearse sometimes with the PA pointing back at us so we hear the front of house sound and you have to practice and listen to get the relative volumes right. You also have to get monitoring right, if you can't hear what each other are doing then you can't really match volumes appropriately. I aim to set the gain so everyone is equal on the loudest parts and let the singers sort out for themselves who should be the loudest in any given part of the song. I like to record the perfomances from time to time, You soon pick up who is hiding in the mix and who is too fond of their own voice and can make necessary adjustments, In the end though there is nothing much you can do with people who don't practice singing together unless you are sitting at the desk out front, even then some bands are a dream to mix and others are just hard work. If it's any consolation @Chienmortbb in your opening few songs on Saturday I commented to Mike that the harmony parts were working well until your PA meltdown.

Yeah we noticed your bv's weren't coming through, shame really because some of the harmonies in the first few songs were quite nice, lifting the songs. I'll PM you

Oh John, it would have been a comedy if it had been at an open mic. The speaker stands had been set up with the legs splayed little more than the width of the speakers and then had been placed on an uneven bit of field which ws sloping. His eq was all over the place, just at random it seemed, and he'd turned the mids right down at some point and was then complaining of no volume. Someone with a bit of sense set the eq to flat and bingo you had volume. At one point he switched the output to the monitor channel and couldn't understand why the master volume wasn't working! Total panic. Btw there are line level outs on the front of the amp but you'd ideally want to use TRS to XLR leads. Anyway I'm glad we got it working and it turns out that through decent speakers your guy has a good voice. It might persuade him to let you in if you reassure him he'd sound better with someone else operating the PA. Your bass sounded great by the way. Was that the Monza?

OK lower tuning it is, I'll have a look at tunings between 45 and 30 and base the design on that and flattest response. Did you manage to take any internal measuremnts yet?

So this is the excursion of the speakers at 300W. The horizontal red line is where the excursion starts to distort. If the excursion reaches 0.09 (9mm) the speakers will be damaged and eventually stop working. You can see the lowest excursion is at high frequencies and at the tuning frequencies of the ports 30,50 and 60hz in this case. The only tuning that runs into distortion at high power is the green/lower tuning. They all go into damage levels below 40Hz/bottom E at full power but it's a lot lower in the lowest tuning. Even if you are reading this and have no intention of building a cab it's worth knowing that this shaped curve is the same for every ported cab and your bass cab almost certainly can be forced into damage mode at low frequencies!!!! However don't panic. There is almost no fundamental coming out of your bass pickups. they are placed well away from the middle of the string and that reduces deep bass. Most of us don't have amps that go down to 40hz without rolling off either. There isn't any reall evidence of a lot of broken Ampeg VB212's or any other cab of this type. For me this graph shows that any of the tunings will work without issues but it's not a bad reminder of using an HPF if you have one.

At this point we have a design brief ready and the parameters are loaded into the computer so now it is simply about tweaking the design. I'm looking for a roughly 90l cab for two Eminence Basslite 2012's, the shape will be determined by the needs of the user so now all I have to do is tweak the design and see what I can squeeze out of the cab. I'm starting out by looking at the tuning. I've bracketed my 50Hz tuning in blue with 60hz tuning in red and 30hz tuning in green. I'm quite liking 50Hz tuning. Theres a 2db hump of extra bass at 100Hz which will warm things up a bit and give that old school thump. 60 hz increases the hump to 3db which I would find intrusive and would be hard to tune out. 30Hz tuning gives a flatter response and a slower roll off (but from a higher frequency) but is more like the measured bass response of the 2x12 Ampeg SVT cab. This is down to Martin's taste I think, so the question is: In your face bass warmth, Ampeg like gradual roll off from fairly high up or a compromise somewhere in the middle? Before you choose there's another consideration, how does this load the speaker cones and will this affect power handling?

OK one last thing to bring everyone up to date, @police squad asked about a sealed cab. Once you have the speaker's mechanical and electrical properties loaded into WinISD it's a matter of seconds to model a range of cabs so I sent him this: The purple line is the sealed cab, the red line is a 90l cab and the blue and green lines are for 200 and 300l cabs. I actually quite like the sealed cab, it has the flattest response and -3db is around 75Hz so all the second harmonics of a 4 string bass will be accurately reproduced and Eminence also have this design which they describe as "ultra clean" which is probably a very fair description of how this would sound. However you can see how much bass is lost compared with the three ported cabs and the bass hump at 100Hz will also warm up the sound and add a bit of thump which is what Martin wanted. I'd had the other two cabs there to play with different cab volumes to see if I could squeeze a bit more bass out of the cab. The 300l cab in green has a whole lot more bass and a flat response but 300l is an absurd size for a cab if you have to transport it. I'm only showing this to demonstrate that all cabs are compromises of practicality cost and sound and I suppose to say that I did look to see if there were any advantages to a slightly bigger cab.

Thanks David. Martin @Mottlefeeder managed to find them too. The "small vented cab" is 45l and to 55Hz for a single driver. My first guess was to use a 90l cab tuned to 50 hz which is the approximate volume of the Ampeg cab we are copying so in this case it's reassuring to know I've come up pretty much with the same design as Eminence. It may even be that Ampeg knew of this design when it developed the VB212 but to be fair there are only so many sensible solutions for any given driver.

This is interesting, it's the measured response curves of the SVT212. Obviously ignore the top end because we won't be using a tweeter but the bottom end shows a similar roll off to your speakers in a 90l cab, It rolls off really quite high from 150Hz but also quite gradually so it is around -10db @ 50Hz. There's a big drop in everything at around 1300 Hz, which I'm guessing is the crossover. The red line is the response straight ahead and the colours are off axis. You cvan see how much the mids are lost off axis and this is increased because of the sideways displacement of the speakers. You get quite a lot of off axis fall off anyway due to the size of the 12" drivers but the cab is over 600mm wide so it's like having a 24" driver rather than a 12. Above 2,000Hz you are looking at the response of the horn which isn't relevant if you are building a tweeterless cab. I'm not a purist in these things, if you've tried the SVT and love the sound then you can build something like a horn free SVT. Without a horn the off axis problems will be worse but if you tried it with the horn turned off and still liked it then that's clearly somethign that doesn't worry you. If you want a cab the same width as your amp but with the speakers in line then you can do that too and it will be slightly easier to hear yourself on stage.

You could go for this shape

OK a bit of a recap. on our discusion so far. This is the cab Martin wants to copy but he won't use the horn driver so we are leaving that out. I suggested that he would be better with a taller cab and putting the two 12" drivers in line to improve dispersion and the audibility on stage. Anyway this is the cab we are 'copying'

That's my fault, I'm a details person and I just assume everyone is as fascinated as I am about loudspeakers. I'm a riot at parties 😂

Hi, I've put in the speaker parameters and run a quick check. Get ready for a blizzard of graphs. The first thing is that these speakers are underdamped, basically the magnets/motor systems are small giving a very 'American' approach to bass. The sort of warm/bloated sounded you might expect from Ampeg To get lotsof deep bass extension and a flat response they would need a huge cabinet. This is a pair of them in a 100,200 and 300litre enclosure The one in bold is the 100l cab which is roughly the size you are planning. The 300l cab gives you output down to roughly 33Hz -10db and the flattest response but you wouldn't want to fit a 300l cab into a car never mind carry it. However you probably wouldn't want that much bass anyway in a gig situation. I just want to show you the choices you are making

Hi Martin, I've had a quick look on the Eminence website and these speakers look like they would work in a 50l cab or 100l for the pair. They are very high efficiency and have Eminence's typical midrange peak so good for creating an old school sound. Eminence used to offer cab designs for all their speakers but I can't find them as they have re-built their website. The designs may still be there of course. In performance the basslites will be very similar to the ceramic magnet Beta12-2A as used in dozens of commercial cabs so you'll end up with something sounding like TC/Markbass etc etc. Not exactly, but in that sort of ball park If you are a valve man you'll probably be looking for that sort of sound rather than FRFR anyway so they could be a great match.

Hi all, I had a recent request from @police squad for help with a 2x12 design. I've started to do this via PM but thought other people have asked for similar designs and people might like to follow the design process. Basically it involves me asking a series of stupid questions to home in on exactly what he is going to try to achieve. Then I run computer models and ask more questions to home in on what I hope will be his best speaker. Anyway this was his initial question

Not by one of the mods I hope? I'm kind of surprised that when people ask for help and others offer to go over to help out in person that there isn't a response, but I've also posted questions myself and fogotten the thread for a few days because I've solved the issue. I always feel as if I've been unintentionally bad mannered but it's never intentional. I do like a happy ending though, so it would be nice if @proy900 did come back and tell us it's all up and running

It's the amp @stevie uses

The system you’ve got is easily enough for your needs. As Dad has said you will have feedback problems way before damaging the speakers. The amp is excellent, the mixer is fine and the speakers will probably be reliable though the vocal sound will need some tweaking. They’ll do a job for you but might be the first things to replace if you are unhappy with the sound. You might need to address the room acoustics too but you’ve nothing to lose by just setting up and giving the system a try. Again once you let us know where you are based I’m sure someone will help you do the basic set up

Maybe we need to run a wiki of some sort on routers, they are probably the most difficult power tool to use. It's much safer all round to only use them with a jig or mounted on a table. I have a 1/2" router that I use for cutting kitchen work tops and any big jobs I do like shaping architraving or skirting boards. I pretty much won't/can't use it freehand for anything I have router tables so the machine is static and I move the workpiece, I also have an ELU 1/4" router which has a bit of a soft start but even so you can't start it enywhere near the workpiece as it still needs a lot of strength and skill to manuvre. It's roughly 1HP so it's literally got a kick like a horse and routers operate at really high speeds so it's like guiding a gyroscope, it wants to go it's own way. I round all my edges with it in mounted in the router table and move the cabs. I'm wondering about getting one of the little trimmers for the odd small job.