Phil Starr

You've got your advice and I think you realised this anyway from the way you asked the question. Yes you can damage your speakers with an amp even within the specified power rating of the speakers and the enemy is extreme equalisation/fx. There are two ways to break a speaker and they are interrelated. you can do it one way or the other or a little of both. The enemies are overheating the coil and moving the coil and cone past their mechanical limits. The graph below shows the movement of the cone of the same speaker with the red plot at 1/4 of the power of the green plot. You can see tht the excursin rises as the frequency goes down but at 50 Hz the port takes over and the cone movement reduces right down. The horizontal red line is the excursion limit of 6.5mm. You can see that at full power the cab goes outside it's limits between 55 and 90Hz and again below 45Hz. If you put a bottom E at full power with an octaver (41Hz/2 or 20Hz) it would force the cone to travel through a 6cm round trip which would hammer it against the back of the magnet 20 times a second. Not good. So for these frequencies (where the curve goes above the red line) the power handling is limited by the excursion. For the rest of the time the limit is the thermal limit. So there you are the power to any speaker is less than the rated thermal limit at certain frequencies, genrally lower frequencies but there's almost always that dip just above the port frequency too. If you use just 3db of bass boost you will halve the power handling and an octaver is even worse. A decent HPF will pretty much help any reflex(ported) speaker cab by removing that huge spike in excursion below the tuning point.

you've heard my bass playing, I'm saying nothing

I didn't save the data so this is from memory, which may of course be faulty. I agree with you about the potential 'better' performance from the red speaker. That's certainly a cleaner curve and showing 'better' damping of the hi-fi driver. Resonant frequency is lower as you would expect with a slightly heavier cone and a less stiff suspension. The sensitivity was very similar if I remember correctly, at the expense of lower excursion limits. I've met PeaTurgh and he says in this thread some of this stuff goes beyond him so I made the assumption what he wanted was a practical solution and a fun project rather than an extensive breakdown of options. I was concerned about the excessive excursion below 50Hz but wanted to show him the frequency plots so he could see the gains the hi-fi drive potentially offered for himself and ask about that if he wanted to and all of this is there in what I've said. I must admit I had reservations about recommending a £12 speaker with potential reliability issues against a speaker I had actually in a similar cab in my room in front of me. I pm'd him with a recording of my bass through the cab to see if he was happy with the sound I was getting. I'd deliberately tailored the response of my own cab and it wouldn't necessarily suit him. So yes, this was a recommendation based upon practicality. I quite like my little practice amp. the lack of bass means it doesn't annoy my neighbours, the 2db hump at 120hz gives it a gentle suggestion of bass and it sounds OK just plugged and played. Above that it's nice and clean, revealing enough to show up my every mistake which is what I need for practice. Unlike the cheap beginners amp it started out as it now sounds like a bass. The Monacor speaker would probably have sounded great with noticeable extra bass and probably survived quiet practice but i couldn't really recommend something that I thought might not be reliable long term.

I think the tweeter as an upgrade for the Mk1 would be a great idea. It would keep the concept of an easy build but get very close to the performance of the Mk2. I need to redesign the proportions of the Mk1 as it was proportioned to match the old 19" class AB amps people were still using then. It will be a simple job to leave space for a horn unit to be added later. If you could add a horn for between £50-100 I think people would go for it. Building a Mk1 with a horn would effectively reinstate the Mk2 as an affordable two way design with the Mk3 with the Neo/lightweight/top quality tweeter as the state of the art cab.

I've had a word with Ped and Kiwi and the answer is yes. It might take a while for us to get it together as it would make sense for us to put all the designs together in a single thread and just link to the rather extended original diaries.

Hope you love it, I'm quite loving the clarity I get out of mine. good for practice because it shows off your mistakes. Ouch!

here's the original one 1x12" Cab Design Diary - Amps and Cabs - Basschat this is the cutdown sized one Easy 12" cab build - Amps and Cabs - Basschat The only thread I can find so far for the two way design has lost the pictures 12" Cab Diary Continued - Amps and Cabs - Basschat but i'll keep looking unles @stevie or @Chienmortbbfinds it before me

It's really great to see that this design lives on. I still use a variant of the original design without a tweeter and it sounds huge when it needs to.

I had to look that up To be honest it looks too nice to mod in the way I did, though everything I've done is reversible. On the plus side a single EL84 should sound fine through a little speaker for this sort of use. The problem with mine is amp distortion when you push too hard, you can't really over-drive an amp this size without it sounding nasty. I reckon this little amp will sound sweet. I'd go for building something the same size and finish as your little epiphone, something it will sit on and look right. If you give me the measurements I can suggest a speaker that might work

I agree John, I wouldn't personally look past the TPA series at the moment and you can get ready wired boards for all sorts of applications, so you need to do little other than make a case for them. the other issue is heat dissipation which is so much less for class D.

about 9litres the same size as the cab I used though that was luck rather than judgement. I've been wondering about something similar, you can buy an amp based on the TPA3116D2 for around a fiver which will run on a car battery or the TDA2030 if you don't want Class D on eBay TDA2030A Mono 15W Audio Power Amplifier Board AC/DC 12V Assembled Nice UKO FG | eBay

All PA speakers nowadays are designed to be as flat as possible, there is nothing special acoustically about those that are marketed as FRFR instrument speakers. There's no magic to speakers for bass either the rules of physics and economics still apply and cheap small speakers are still limited in their bass handling ability compared to larger and more expensive ones. There are still bargains and good value for money to be sought out but if something looks too good to be true it probably is something to be avoided. All FRFR really means is that they are trying to design something that is flat. You can always tell if music is acoustic or amplified and there will be slight variations in sound between PA speakers, so it is worth trying them and of course deep bass is always problematic at high volumes for any speaker. The fact you are looking for modest volumes with the PA doing the heavy lifting helps of course. Yamaha's active speakers are really highly rated at the moment. In listening tests a couple of years ago I thought RCF's had a slight edge on vocals and QSC make good kit. My current band use them as PA. I'm not sure that the difference between the best brands would be that obvious with bass. Those Yamaha's will tell you straight away if this approach is right for you. The only thing you are likely to find is that we have got used to 'voiced' speakers where someone has tried to make the speaker easily likeable. FRFR can be underwhelming at first, spend some time getting the eq right for you before you make a inal decision.

I don't play upright (wish I did though) but it should be no different from going through the PA. the thing is that plenty of people have PA speakers so it shouldn't be a problem to find one to try out. If you live in Somerset for example.

No experience of the Harley Benton but I've owned a couple of T-Birds. The bridge on my Gibson wasn't an issue, it's a stupidly fiddly design but the action was fabulous no problems with intonation and once set up any fiddling was soon forgotten. The neck dive is just due to the reverse, that's why basses have a horn sticking out on the top, it's the only way to stabilise the bass with a strap. having a horn underneath makes it just a weight to induce neck dive and having the strap mount on the body and not a horn does the same. I too have found that bringing the strap round the front cures the problem but you'll get buckle rash on the front of your bass. Actually I found that the twist of the bass away from the body was more an issue than the dive. I'm wondering if they do a lefty, that would bring the pegs round to the 'correct side' and put the horn in the non-reverse position.

I use the Mk3 version of this, it just does what it says on the tin. I think the OP will struggle to get something FRFR with control over the tweeter though. It's kind of the point of FRFR that it has a flat response, but you'd normally use that system with some sort of modeller or pre-amp.

Coming from you that's a welcome comment. I know you re helping John (Chienmortbb) with his After Eighty project. I'm using this with my Zoom B1ON and I'm thinking of maybe something with little more than simple volume bass and treble and taking advantage of some of the high power chips they make for car audio. I want something simple enough for others to build so if I can use widely available ready assembled boards for the amp that would be good.

Ha ha Al, I thought you were having a pop at Alex for a second.

I think we all might be stuck in the dark ages. I belong to a political lobbying organisation and at a recent meeting we had a discussion on which system we should use to communicate and found that with 12 of us in the room there were 12 preferences for communication. With my current band we have some who use email others texts or messenger and none of the others use all three. Given we are a four piece and I prefer direct phone calls communication isn't great. My daughter considers it 'rude' to use a phone because she is usually with others and relies on what's app most of the time which I won't use because of their attitude to privacy. Each app has a learning curve which means they all feel unsatisfactory at first and you get swamped if you don't. I've seen people with 3000+ unopened emails, why don't they use the filters? I don't use my phone much, I can only read it with glasses which I only need for reading and are often not to hand. Even with glasses I struggle with some of the apps which are all designed by somebody with the eyesight I had 40 years ago. We're stuck here until someone comes up with a killer bit of software that sweeps away the problems or we all decide collectively on a universal system. The tech giants all want us to use only their ecosystems and have no vested interest in making it too easy. With any band you've probably got to go along with whatever they are using, though most bandleaders often seem to be unaware nobody is reading their emails,messenger,What's App etc,etc Thinking about it I prefer actually talking to people over a cup of tea or a pint. Would that those days returned

Bill's right, the other problem is the nature of the suspension, in an instrument speaker the suspension is likely to be progressive stopping the cone from leaving the magnetic gap. The roll surround will be designed for linearity. I've had a look at WinISD and this is the frequency response. I've assumed 9l for the cab volume the same as mine. The green plot is the Fane and the red the Farnell/Monacor. You get a lot more deep bass out of the hi fi speaker and it's flatter in response, what isn't shown here is that below 50Hz and with just 20W input it exceeds the excursion limits by a lot and this would lead to failure of the speaker in short order without an HPF. this isn't a problem with the Fane (or the other PA/bass drivers) I'm guessing that's why they rate it at 35W The Monacor is probably going to sound fine and will be an improvement on what you have which won't handle bass either but i don't think it will last long if you play it at any volume. £28 isn't much more than a set of strings so I'd still go for the Fane.

Is it a Marshall guitar cab shape with just the top two speakers on a slant? In any case just provide the internal measurements and i can work it out. Either give me the depth at the top and bottom if it's a flat baffle (front panel) or the depth and height where it bends if it is a split baffle.

I wonder what's next, should we design something from scratch, use one of the cheaper pocket amps or just persist with simple mods like this? I'm thinking of having a look at my Hartke Kickback, It's been a really useful thing but weighs a ton for it's size bangs your legs when you carry it and falls over in anything but kickback mode.

Hi Peter, this is an odd one, the half roll surround suggests that this is a hifi speaker and that is what it is sold as. However for £12 you could just decide it is worth a try. The specs are a bit odd, for instance the 35W rating for a 1" coil on an aluminium former looks too low. I'd choose a known entity like the Fane 6-100 (£28) that I used or the Beyma CMV6. The Eminence Alpha that Bill suggested would be good too but expensive this side of the pond. However a 4x6 for £50+ some ply offcuts looks like fun, but I digress. I'll put those specs into WinISD tonight and let you know.

This is so true, one of my best friends is a professional opera singer and also a vocal coach. I know she'd love to teach me, she's a generous human and wants to convert the world to singing. I just couldn't cope with feeling that exposed. Not the way I feel about playing bass in front of her even though the musicians she works with are probably just as distantly ahead of me in their skills. There is something uniquely personal about singing.

The Fane 6-100 is on offer at Blue Aran at the moment £28 + a few pence. Another alternative might be the Beyma 606CMV http://www.bluearan.co.uk/index.php?id=BMA606CVM28&browsemode=category If you want I can model the speaker in your cab and give you some port dimensions.

Here you go, this is my 'build'