Phil Starr

So the graph below is the predicted response of a 12" speaker in a 60litre box, the red line shows a ported cab and the blue line a sealed cab. Same driver same box. The first thing to see is that above 300hz the lines converge and pretty much the whole of the midrange and top end are going to be the same. Exactly as @Twincam discovered when they tried the experiment. Below 200 Hz and for a full two octaves the red line is higher showing that the ported cab is a lot louder and gives a lot more bass. There's an extra 6db at 50 Hz where the port is tuned. That's the same as if you moved from a 200W amp to an 800W amp, and more is better right? It's really hard for a designer to ignore this effect, when you go to try the speaker out in a showroom the ported cab is going to be louder and bassier and sales teams know that this is what sells. It is also what most customers want so why would a designer choose to withhold the extra bass? The sealed cab gives a -3db of 76 Hz and the ported -3db of 50 hz, hands up who will buy the 50Hz cab over the 76Hz cab? OK now move into a gig. Put the cab on the floor and the bottom end gets a 3db boost, back against the wall another 3db. Now you start to notice something else. That sealed cab has a nice flat response that tails off slowly, the sealed cab has a sharp knee and lots of deep bass. The extra 3db makes up for the missing bass for the sealed cab and it sounds a little better. 3db of deep bass isn't so helpful for a cab which already has enough deep bass and it starts to sound boomy/muddy. This is exactly what @BassAdder27 was describing in terms of mid-punch versus fullness or roundness. Extra bass isn't always good, you need to make decisions based on what sound you prefer and recognise that what works in one situation won't sit comfortably in the mix in another. Now there is quite a lot of over-simplification here. I've deliberately chosen a driver which will 'work' in both a sealed or ported cab and which is the sort of speaker you'll find in a lot of mid priced commercial cabs. I've also used the sealed cab size that gives the flattest response, that happens to give the nearly 2db peak for the ported cab. I could have easily changed drivers, porting and tuning to create a flat response ported cab. I've chosen to emphasize difference too but you are always going to get that extra bass from a ported cab all other things being equal. It's the sound coming out of the port that does that and the port does other stuff too. There's a bit of a generic difference between ported and sealed cabs but a good designer can create a good response from either sort of cab with the choice of driver and the careful matching of the cab There's one other thing to think about too. We almost can't hear bass, not the deep stuff. Most of what we hear as bass is the second harmonic, 80-160Hz for a four string so -3db at 76Hz is more liveable with than you'd expect and on top of that what really makes the timbre of your bass is all up in the mid frequencies where the cab makes little difference.

Go for the £50 one, this sort of thing does go for around £100 sort of price, I recently sold my Hartke Kickback for £100 in pristine condition but £50 you can sell it on again for no loss every day of the week once you've had it a couple of years. It's going to be so much better than what you have you won't want to put your bass down once you plug in. that's a really generous offer.

I have two chainsaws awaiting re-built carburettors on mine. Plus the control unit for an Ariston boiler which has been scrapped (but the relays might come in handy)

The pile of tools on the left looks like my workshop, the neatly racked spanners not so much Good to see it coming along

It is, nicely made and the spec is spot on for a portable bass speaker.

As some of you will know we specified this speaker as the basis of the Basschat 1x12 cab and the Mk 2 version with a Celestion Tweeter. The SM212 has since been discontinued but I have contacted Beyma to see if they might make a short OEM run. They aren't interested but they do have 35 SM212's still in stock in Spain, they forwarded me to Blue Aran who have a shipment about to leave the Spanish factory in a couple of days. If anyone is interested it might be worth placing an order. Contact Blue Aran directly or let me know here and I will get back to them. It's a lovely driver and ideal as the basis of a bass cab. Excursion or Xmax is exceptional at this price bracket meaning this speaker handles low frequencies exceptionally well. The designs for both cabs are available here on the BassChat website.

Hi Jon, @stevie might be along later to help but you have two practical considerations. The obvious crossover is to build an identical low pass filter to the one in the cab you are building which will mean both your 12's will be operating over the same frequency so you'll have the same bass but 3-6db more of it. What you will hear on top of the speaker with the horn raised nearer your ears won't have changed much but the audience will be getting a bass dominated sound. The other approach would be no crossover at all. This would mean you'd have all of the sound of a 1x12 without a horn. Up to the crossover this would be good two identical speakers in phase making a noticeably bigger sound but above the crossover point the output of the lower can would overlap with the tweeter so that at some frequencies there would be cancellation and at others reinforcement. All that means that the combination wouldn't sound the same as the original cab and would no longer be FRFR. the only way to find out how it sounds would be to try it. I'm not saying it would be bad, just different. Barefaced and the like often advise the mixing of cabs and some people like it. They probably like making extra sales. I'd wait until you have tried the cab you are building. It will go extremely loud and will comfortably match the drums, you may not need an extra cab. As you are self building you could leave space for the horn in the second cab s you could add it later if you didn't lke the combination or you could build two Mk3's but have a switch to cut the horn when it suited you. But try the cab first, you might be pleasantly surprised at the volume

Hi Peter, one of your posts struck a chord with me, no pun intended. I also started bass late in life later than you in fact and have suffered from imposter syndrome for most of my playing career. I'm slightly older than you too and am usually the oldest member of the band. I've been luckier though as most of the time I've been gigging regularly. You shouldn't feel as if you were 'sacked' just that you stood up for yourself and tried to make the band better. The guy was simply wrong, successful improvisation takes real structure and discipline other bassists may have worked to cover up his issues but I suspect this is just a narcissist and a bully. Just focus on what you really want, to join a band, be part of a group of people working together and who want to gig together regularly. Value your contribution, they can't do it without a bassist and reliable, organised easy going musicians aren't exactly plentiful. You may have to work hard to find people and you may have to compromise on the music played but there are working bands out there for you. I've played hundreds of gigs now but sometimes you spend a few months in the wilderness. Previously I've been through the desperate, needy join any band that will have me process but actually it gets better when you set your own standards and decide for yourself what you need as a minimum and what you are prepared to compromise on. I've just spent four years with a band of lovely people, not the best band in the world but people I've been glad to spend time with who have spread that togetherness to audiences so that we have never had trouble getting re-booked. Sadly our singer has called it a day and I'll once again be looking for a new band. I know what I want; no big egos, 20 gigs a year roughly, people who put the audience first and who are fun to be with and musicians who take the music seriously enough to always want to play their best and who have a professional attitude. Everything else I'll compromise on. Every audition I'll be auditioning them as much as they are auditioning me. It's a dating game and I'm not going to settle on something just for the sake of it, someone out there wants me and someone will want you. have faith and look for that gigging band with confidence and energy. Good Luck

I love a happy ending The test of any cab is how it sounds with a band. It's a shame a new Kappalite is so expensive of I'd be recommending more people to have a go building your design. I've built a similar 15 with a Deltalite that I picked up cheaply many years ago but again financially it's not good value in the UK so I haven't published that design. That doesn't matter to you of course, you've built a fine cab which will last for years and always give you the satisfaction of having worked from scratch and made something great. And you've shared it with all of us. Well done

Thanks guys that's really helpful. I've been looking at smaller speakers and trimming the bass in the cab to concentrate on the second harmonic 80-160 Hz region. From what you are saying that's a good starting point. I'm also looking for a clean neutral sound for an acoustic instrument, it's such a rich complex signal I want to treat it honestly.

I'm still following this with interest as I'd love to design something that was ideal for a proper bass. I came to bass late and probably won't get a chance to play one myself but it poses a different set of problems from designing an electric cab. No one has said anything yet but I imagine an upright would suffer from a lot of problems with feedback and resonances; both in the air in the body of the bass and in the resonances of the large thin panels. It is certainly a problem with acoustic guitars and even hollow bodied electrics. Is this a problem?

Hi John, the plans are in post 2 of this thread. I'll try and get some tips on the build and some pictures up as a priority if you are building soon? I've used the cab a lot now for open mics in rooms which are much bigger than the ones I originally designed the cab for. There are no problems with the rear port unless you literally press the cab against the wall and the bass reinforcement from a wall will really help with the bass in the room, as it does with any cab

double post

Watts clearly do matter or a 1W amp would be as loud as a 1000W amp. It defines the rate of energy transfer https://en.wikipedia.org/wiki/Watt You don't need to get into a technical feeding frenzy however, watts depend upon both volts and current and in a practical amplifier they aren't independent. You don't need to understand that though just read your manual You get 800w at 4ohms and 480 per channel at 8 ohms or 960W in total at whatever distortion level your manufacturer chose to measure this at. Marginally more power using both amps. Not enough to be noticeable soundwise but more. More importantly the current flowing in each amp will be lower and high currents will create heating and other effects within each amp which might mean losing some power over long term high level use. I think your answer is in this part of what you've said "2 x BBII yes they are loud. But I don’t feel the same heft and pure power like you do when playing in front of an ampeg SVT / 810 rig." There are a whole lot of differences between a monstrous wall of cheap drivers driven by an SVT and a modern FRFR speaker system with it's 'hi fi' sound. The 810 is going to be more efficient and highly coloured with lots of frequency bumps in the response which you are hearing as heft. The poor Barefaced had all of that removed to give you a cleaner sound. Finally I wouldn't pay too much attention to the clipping light. It's only showing that you have signal. Your manual says listen to the speaker output to verfy operation

I had a look anyway, this speaker will go in a cab as small as 3l but with the low value for Qts it will have a marked shelving response with the bass down a long way. In this cab it needs tuning differently but the best I could do leaves it with a dip in the 80-160 hz octave where you least want it. It does have a bit more deep bass but the Fane is also 2dB louder at the same power. Having looked i'd only use this as a mid range driver. If you want lightweight the Faital 6PR160 looks a better bet. The other possibility is the Beyma 6CMV2. BTW if you use the I/2 overhang + 1/3 gap depth for the Fane it has Xmax of 4.5mm the Fane is red the Faital 6RS140 green

Hi Al, coincidentally last weekend we put the QSC 12's my band use to the test with some frequency response charts. They are sometimes criticised for their 'harsh' treble and we did measure some problems there. They are still fine speakers but if your RCF 310A's are loud enough for you then with subs they make an excellent system. I use a pair for our duo and as monitors for our band and for an open mic/jam session I used to run. They are really well behaved high quality speakers. There just aren't any sonic nasties there so they can be pushed to really high levels without causing feedback. I've just spent a long weekend this weekend using them for everything for the duo; bass, guitar and two vocals with no backline and they have sounded so good. I'm not a strong singer, plenty loud enough but my pitching isn't secure without decent monitors and these offer the best vocal sound I've ever got from the PA including top quality hired in systems with pro floor monitors. I've never had a better bass sound than I get from these up on poles and the acoustic guitar sounded, well like an acoustic guitar. A pair of these with subs would be a great system but put them in front of the stage if you can and if you have two subs they are better acoustically together as Bill Fitz Maurice has said over and over again. Although I tend to let the practical consideration of stopping drunk punters knocking into stands sometimes override the sound considerations As to crossover why not ask RCF? As a general principle I'd crossover higher rather than lower and as BFM has said a bit of experimentation should guide you. However as a general principle any frequency irregularities related to a compact cab are going to be centred around the 100-140Hz area and excursion limited power handling issues below 100Hz so a 120-150Hz handover of duties looks good to me. The higher the frequency the less power gong to the tops might also be a consideration. But these are general principles/rules of thumb I have no knowledge of the particular characteristics of the subs you are using.

Good news, I had a second look at the Faital last night. the frequency response looks great and the speaker has a longer coil than the Fane with the same magnet gap. I haven't modelled it yet but it looks from Vas and Qts figures to be an OK match for this cab. Maybe even a slightly smaller one. Can you use WinISD or would you like me to have a look

Thanks Steve, that's really helpful. Articulate is a good description and that is exactly what I've found, it's a perfect practice speaker because it brings out your playing but doesn't distract. One reason for this is that you only need a hint of the sub-harmonic bass in most people's living rooms but there are a couple of other things too. A small driver has better dispersion than a large one so in smaller rooms where you are closer and can't always sit straight in line with your amp you'll hear more of what the speaker is doing. More importantly you have a more or less flat response all the way up to 7,000Hz which covers the whole output from the pickups on your bass. No irregularities from a crossover and no need for a tweeter. I initially designed this as practice speaker with a 10-20W amp in mind and something that would boost the sound to the point where I could jam along to a jumbo acoustic guitar. I only tried it with my main amp because, well you have to try your bass with every speaker. It was only then I realised I had something special. I hope you enjoy it with a bigger amp, just remember it's only a 100W speaker

Hi John, you have to look carefully Faital are looking at the coil overhang+ 1/3 of the gap depth as Xmax, I've seen other people use Overhang +1/2 gap depth and some just using the overhang. I think the Fane does this. Also used is the excursion before a specified level of distortion. It's all valid as the magnetic field does extend beyond the gap but for the unwary it can end up comparing apples with pears. Fane and Beyma used to use the less favourable overhang only measurement but with the comparison charts are starting to change to overhang+ Celestion are using overhang only so far. I think Fane used overhang for the Sovereign 6 from memory. Have a look at the top end response also, it's pretty good for the fane. The Faital though gives extra power handling and lighter weight at a price. It's a nice driver though and I'd love to hear how you get on with it if you go ahead

Brilliant, I am pleased you like it, any feedback good or bad would be welcome. I've used the cab again in public this week and it's still doing what it says on the tin for me,

John you've got me thinking, I'm checking out alternative drivers already Shelagh will be pleased! I've been using the House Jam speaker at open mics for the last few days, too loud and a bit bassy at the last gig apparently. Well if they will rush you on with 30secs notice.......

It's not just a had but you might want to look at this https://www.basschat.co.uk/topic/442331-a-house-jam-combo/ coincidentally I revisited it last night, wondering whether to try it at an open mic. The problem is the guitar eq, if you were prepared to tweak that it would be plenty loud enough. If you wanted to start from scratch there are plenty of TDA2020 boards out there and you could run off batteries if you wanted.

Well done, it's great to get to this stage and now you can take an empirical approach of trying things and using that to improve your cab. I like the idea of doubling up the baffle if you are happy with the extra weight. I'm a little worried about that baffle TBH. You have a lot of speaker in a small cab and most of the baffle is cut away leaving it inherently less stiff. Have you just used the bolts to secure the baffle? The foam strip you mention will ensure the cab is airtight but just fixing at the corners isn't enough. At higher power levels the panel will want to resonate and flex. I like a removable baffle but I use screws with a minimum 10cm spacing. That should crush the foam seal and give you a bit more depth for the grille cloth. I'm particularly loving the printed port termination, it looks really good and those small radius cut outs for the port are really hard to do tidily. I'd always go for some wadding on the rear panel and usually do the top bottom and sides as well. Now you have a cab you can add and remove it at will and do listening tests. Keep it away from blocking the port though. You might also want to add some top to bottom and side to side bracing. Again you can do this by testing your nearly finished cab. Well Done

The perfect London cab. You can take it on the tube and at home it won't annoy the neighbours.... well not as much as some others might

You're going to have to do something with that top cab, it's letting the side down