Phil Starr

Looks like I'm going to have to make some sawdust. My wife will be pleased.

The original cab was built just because I needed something I could build live for the bass bash. I used the Beyma SM212 because I had one laying around and because it is a decent driver. The main reason I went for a 30l cab is because I'd been gigging the original BassChat Mk1 design for a while and the extended bass was proving a problem in a lot of small venues. Not a problem with my Hartke where I could use the graphic but not good with other amps. I was regularly dialing down the response 10db at 50Hz and then adding something extra at 120Hz. I already knew that by putting the SM212 in a 30l cab I could engineer that response and have a smaller lighter cab. It worked better than I expected and it was a bit of a 'wow' moment when I played it at the end of the demo. It's been my go to speaker for pub gigs ever since. The B&C 12CL64 looks like an interesting speaker and I had considered it myself. It's engineered slightly differently from the Beymas with a lower excursion and higher efficiency. It has a lower thermal limit and that with the lower Xmax will mean less ability to handle deep bass. On the plus side it's a really affordable lightweight neo speaker. If you wanted to build something with it and share your build here then I'd be happy to do some modelling and design a cab for you. Welcome to BassChat

I allowed for the driver, the ports and a little left over for any bracing. you'll find that a similar amount is also allowed in the 50l enclosure

Just for interest these are the predicted responses of the two speakers at 320W, the thermal limit of the 12CMV2. You can see that the response below 100Hz is pretty nearly identical, above that the SM212 has about an extra db which is just about noticeable in A/B listening. Subjectively the volume levels are the same as the 12CMV2 has a broader midrange peak and of course that is where our hearing operates best. As i said above I think this is why it sounds more agile and detailed. The -10db point is around 50Hz which is quite good for a little cab like this and both speakers manage 120db levels across most of the range which was the original design target and should be enough to work for most bands.

Hmm could it be worse

I wonder if this was more to do with faint praise, you dissed his new love maybe. Tried her out and found the bass of his dreams somehow lacking?

Hi Dan, what do you like, the look or the sound? Changing speakers can be fraught. First of all the cab is or should be designed to work with specific speakers, changing for other speakers will probably change the bass response, if there is a severe mis match it will reduce the power handling from the listed power handling, in the worst case down to a few tens of watts and people have lost speakers because of this. I don't want to over- exaggerate though most speakers are similar but is is best to check than to find out the hard way. Secondly even if you get a match the frequency responses may be very different so the bass tone will change, it could be better or it could be worse but you won't know until after you've shelled out. Finally it's unlikely you'll save much weight the neo speakers will weigh a couple of kilos give or take so you'd be doing well to save more than 4-5kg that's a lot of wood you have there

Not really, cone area is related to dispersion and to efficiency. Like going into a pub and ordering on the basis of hop variety perhaps? Though in this case the radiating area is little different so it isn't going to be much of a factor.

UPDATE It looks like Beyma are about to pull the SM212. Coincidentally I've just been given a Beyma 12CMV2 (thanks to @Chienmortbb) to try in this cab, it has the same magnet but with a heavier cone, stiffer suspension and a new voice coil. It also has a pressed steel chassis and is considerably cheaper. The good news is that in this cab it actually sounds better. The bass response is basically unchanged, but one of the frequency anomalies of the SM212 has gone and there is a broad boost in output in the upper mids which makes the sound lighter and more detailed. I'm still investigating and haven't tried it at a gig for COVID reasons but I'm happy to recommend this speaker if anyone is thinking of a build. If I get more information I'll put it here.

Like everyone else I think you need to try them. Two eights have a slightly lower cone area than one 12 but not by much. The smaller speakers also mean they might beam the mids a bit less but we don't know the crossover frequencies for either cab so who knows. Their ads boast a lower frequency response for the 2x8's and the 2x8 is lighter but the 12 is advertised as noticeably louder by a couple of db's. the 2x8 looks an easier shape to carry on public transport. Only you can decide what is most important to you.

Just thought I'd finish off this little project. I left it with leads coming out of the port, good enough for testing and sitting in the corner but not very practical, not least because the mains switch was only available by reaching through the port. First thing I decided was to have the possibility of adding another 8ohm speaker, 20W would be better with an 8x10 Then I added a new switched IEC socket. I wanted to be able to remove my mods in the future so I wired up the IEC plug cut off from one of those Thomann euro plug jobbies This and the spade connectors can just be unplugged to return the amp to original. Bit of black paint and the job is done

ignore this

Hiya, well I'm having fun. Not least because your enthusiasm drove me to complete my own version of a baby combo. Fun playing it last night and I didn't wake the neighbours Don't worry about the 4ohm thing, it will give you an extra db but that's about it. You'll get around 10W into 8 ohms and if your amp uses the same chip as mine it will give roughly the same power into either impedance as it is current limited into lower impedance speakers. In any case the speaker you swapped to is * ohms and you know how loud that is. You lucked out with that port unless you did some calculations/mods as it is tuned almost exactly to the frequency I used in my modelling of your cab. If you swap to the Fane then a 4cm tube will lower the tuning of the cab to suit the new driver. I've assumed a port of 1.5mm wall thickness fitted inside the existing port with an internal diameter of 40mm. Your maximum sound output is going to be around 105dB, 106 in the midrange and 104 in the bass.

Well done, I was looking at one of those little amp modules myself to beef up my lockdown combo. I was looking to cheat even more and use one of the ready made pre-amps. Following with interest.

Is it hypercardioid though? If it is picking up sounds from all around then it's omnidirectional by definition. There is no strict definition of what cardioid, super-cardioid and hyper-cardiod means anyway and my experience is that the actual directional nature of mics described as cardioid varies a lot. If it's part of a cheap set shipped out of China quality control can be problematic and who knows what capsule is inside. It's also possible that part of the mic is broken, directionality is achieved by cancellation. The omni directional part of the mic is joined with a bidirectional signal and the sound from behind in the bidirectional element cancels the rear sound from the omni part. If the capsule is broken or blocked by damage/poor manufacture then the cancellation won't happen. You can test the directionality by talking your way around the mic and checking the sound level falls off at the sides of the mic.

so this is what effect the extra 2litres make. I've tuned the cabs a little lower to give the nearest to flat response you can get with these speakers and the extra cab volume does give more flexibility. I don't mind a coloured cab but for me that peak is a little too big and a little too high with the current speaker. Actually the volume change has moved the peak and the -3db point down roughly 10Hz which is quite nice. The Fane will give quite a grown up tone for such a small speaker, a 4x6 might be quite interesting. However if sheer volume is the thing then there is no point in changing. If you send me the port dimensions Michael I can optimise them for you.

Hi, I've just run some modelling but this is based on the 9l volume of my cab. The Fane I mentioned and used myself comes out better slightly than the Beyma so if you want to go ahead I'd buy that. The blue is your current speaker in a ported cab and the purple is the same speaker in a sealed cab of the same volume. as you can see they all meet at the higher frequencies but low down the ported cab gives a lot more bass than the sealed cab down to about 70Hz where they cross over. As you can see there is a huge +4dB peak at around 160Hz in the low mids. Your speaker is underdamped (Americans use this term differently I think) and normally this much of a hump would be undesirable distortion. In practice this will be extra volume and a warmer sound which might be the fun factor you like about the way it is set up at the moment. Your speaker models better in a much larger sealed box, you can see the sealed box response is flatter but rolling off at 200Hz isn't any good for a bass player. For comparison the green response is the Fane, as you can see the volume peak is lower, just under 2db, and at a lower frequency around 110Hz, quite a good place to have a peak for a bass especially if it is bass light. there is also an extra 2db of bass below this point. All this means is that you have struck lucky with the speaker you have in terms of volume, that huge hump is giving you a lot of extra sound in the low mids. The other speakers will be subjectively quieter. In terms of sound quality the Fane will sound better for bass guitar. It has a flatter response and a touch more deep bass below 100Hz, the 2db boost at 110Hz is well controlled and in a nice place to give a subjective impression of real bass. All this is in a 9litre box yours may be a bit different.

OK it looks like we have a fun lockdown project to find how far the envelope can be pushed. Having had a lot of fun with my version I've ended up with a usable practice amp in a tiny practical box with very little effort. Actually it's better than that; it's good enough that I can get enough volume from my electric bass to do what other people do with double bass, play with other acoustic instruments and singers. That Beyma is just slightly better than the Fane 6-100 that I used too. I had the Fane kicking around from another project so I didn't have to spend anything which was a bonus but £33 for a weekends entertainment and the possibility of something satisfying to play with your family sounds like it's worth a try.

It's an OK speaker but designed for car use, the specs are bit dubious as they quote sensitivity as both 98dB which is high and 91.5 in the T/S parameters which is what you'd expect from this sort of unit. It probably has higher output at higher frequencies which is where they get the 98db figure from. They quote Fo as 114Hz which is well above bottom E at 41Hz so this is going to be well down on bass output but as Bill says it's not all that bad. You aren't going to get something that matches your double bass in terms of volume out of a 15W amp in a small box like this. You could get a little more output and slightly better bass response out of the Beyma I linked you to. The beyma would be suitable for a ported cab which would also help a little. None of this is going to be dramatic though. I think at this point you need to decide if you are driven enough by curiosity and the need for a project to want to see how good this little amp can be and then decide if £33 is worth it to satisfy the question. This is a bit like adding a second carburetor to a Morris Minor, it will go faster but it'll still be a Morris Minor

just to keep the conversation going I had a quick look. The Beyma 6cmv2 Beyma : Beyma 606CMV28 :: £33.29 IN STOCK (24 Jan 2021) (bluearan.co.uk) at £33 looks about as good as you can do in terms of value for money, unless you want to really spend, in which case there's a BMS driver you could buy at £110. I can't imagine why you would do that though you'd still be limited by the size of the cab and the 15W maximum output from the amp. If you want to do some irreversible surgery then you might be able to squeeze in an 8" speaker. As @Balcro says what do you have now? Are there any ports? There may be marginal gains here but don't expect miracles.

I don't know if this will be helpful but I recently knocked my old practice amp about in just the way you are proposing, the details are here A House Jam Combo - Build Diaries - Basschat I'm coincidentally currently eyeing up my Harke Kickback with the intention of seeing what can be squeezed out of that, mainly to see if I can save some weight as it's a heavy little thing for it's performance. It has a 100w amp though and a 10" speaker. I swapped the internal speaker for a Fane 6-100 which I had bought as a mid range driver. 6" 100W. You have two problems; using a 6" speaker means limited cone area so bass output and efficiency are traded and a tiny cab volume. Using a low power amp means you need very high efficiency to get adequate volume. I think I've got close to the limits with my build and so will you. The tone I've got is very bass light, much better than I started with but much less than my live rig, the volume is adequate for practice with an acoustic jumbo guitar and unamplified singing indoors. With a bit of compression of the signal and some fierce bass filtering below 80Hz you can get some extra volume and you might do an open mic night with it but that's it really. you might be able to get an extra couple of db from a better speaker but you'd be into something esoteric and costly to do that. As a practice amp though it's now great, enough bass not to sound tinny but loads of low mids and plenty of detail to show up every error I make with quite an aggressive but satisfying sound. It just won't go loud enough. With a double bass, I'm not sure if you'd add anything to the acoustic sound, probably a subtle enhancement of the mids but that would be it. It was fun to do but not for the uses you want to put it to.

just been on the phone with my friend who is a doctor in A&E. She's just treated a 55 year old in difficulties who contracted COVID by sharing a car with someone. 'We only shared a journey for 15 minutes so we didn't think masks would be necessary'!!! You can't make it up.

Wait until he adds the x32 We did get some great sounds out of a borrowed X32 though

The base of this is really very simple and always has been. This is a respiratory virus basically spread by breathing in viral particles that someone else has breathed out. It isn't safe to breathe in the air someone else has already shared. Of course washing hands and surfaces makes sense but you can't 'clean' the air. The public have been misled by politicians spreading the concept of Covid secure areas. Going into an enclosed space with an infected person is how we spread the disease however otherwise clean the area is. You can't have a pissing area in the corner of a swimming pool or a smoking corner of a crowded pub without sharing something unpleasant. Outdoors the air dilutes smells and viruses fairly quickly and the evidence is that there is little transmission. It has never been Covid safe to be indoors with other people and the more people and the smaller the space the more dangerous it is. The most dangerous thing is to be with young people who are more likely to be asymptomatically infectious. Your risk of spreading the disease increases logarythmically with the number of contacts you have. Schools, hospitality/mass indoor entertainment, shopping, public transport and indoor work are the biggest spreaders and you can't make them totally safe. The other myth is that disease is mainly spread at home, you can only spread disease at home if someone takes it home, these things aren't independent events. Our government policy of trying to keep the economy going by managing an 'acceptable' death rate has failed as it always would have and has merely prolonged the emergency and led to an increased death rate. to be fair most of the 'Western' countries have followed the same policies with similar results. Eastern and Australasian countries have made different decisions with better outcomes. It finally seems that with hospitals on their knees and death rates soaring that governments in Europe including our own are starting to 'get' it. Our media, democracy and our personal levels of education have let us down and collectively we have failed to show the political will to deal with this. All we can do now is to keep restrictions in place and monitor the infection rates as we gradually relax them. If we keep the infection rate below one then the disease will have a halving time, the better we behave and the tighter the restrictions the sooner we will be free of this thing. The economy and any mental health issues aren't helped by prolonging this or increasing the death toll.

Yeah the router is what's putting me off the Behringer. It's the sort of stupid short cut that would bug me even if the solution is cheap and obvious. I love things that are well designed and just work, and am stupidly irritated by a foolish short cut. The question is how irritated I'd be if I move on and want to mic up the drums or want to do some live recording.