Magic Matt

Ok, I totally get that when you drive a low powered amp up high, it clips. I've seen it on a scope, it looks ugly, heard it, and it sounds ugly. Here's the thing though... if the speaker can handle more power than the amp can put out, how is that any different to playing music through it that's been hard-limited, or a sound from a keyboard that's basically a square wave? Seems to me that this whole under-powering thing is just a load of nonsense... so what I am I missing? ...or aren't I?

One of the main objectives of the self-build is to come up with something lightweight. I already have a 1x15" combo (Peavey 115S) that I like, it's just a bit heavy carrying up the steps to the flat after a gig. I'm not expecting to best it, but I'd like to at least equal it in sound, just lighter. I also fancied giving it a go and making something totally unique looking. Anything else I can achieve with the cab is a bonus. The local timber merchant stock Birch Ply. I asked if they stocked "void free Baltic Birch or similar" and got this as a quote... 12244122BIRPLY 12mm 2440 x 1220 Birch Plywood BB/BB £31.49+VAT Not sure if that qualifies as really cheap stuff, but the ends looked pretty good. I've not bought it yet - I probably wont until I know what size panels I need, as I'll need them to slice it down to get it in the car. I've bought a set of Mr. Fitzmaurice's rather excellent looking Simplexx 12 plans. I will probably follow those, but possibly vary a little to add batons in the corners, just purely for the sake of compensating for the lower quality ply. His plans have bracing on the panels already and use 12mm (1/2") ply. The main issue I'm going to have is cutting 45 degree angles on the ducts... just have to practice on some scrap with the hand tools! [Quote] [indent=1]Do not use ¾ inch plywood, or MDF. Commercial cabs use ¾ inch material with no bracing, as that reduces labor costs, and MDF, because it’s cheap. The S12 built from ½ inch plywood with bracing is 30% lighter than an un-braced cab made of ¾ inch, but is as vibration resistant as one made of 2 inch. MDF is heavy and not durable, so it has no redeeming qualities.[/indent] [indent=1][/quote][/indent] I think I'd add to that in that MDF is also butt-ugly, annoying to work with, and toxic. The only good thing I've seen with MDF is the "Bendy-MDF" that I thought might be good for flares on bass ports, but even then I'm doubtful.

I'll take a Peavey over a Laney every time if it's for gigging. Peavey stuff is damn solid. The two Laney amps I've had (all valve small guitar amp, and a PA floor monitor) both needed repairing withing a few years... the Peavey amp I have and PA mixer have both been going 14 years now and never had a single problem, even after dropping the amp down two flights of concrete steps (I think my nerves suffered more damage than the amp, which just needed a new handle).

Yes... they are blue lights.... ....you're not helping! LOL!

[quote name='Bill Fitzmaurice' timestamp='1410301793' post='2548095'] None, until you have the plans in hand and are able to weigh the options. There's very little difference in the cost of two 112 versus one 212, the only major one being the need for more jacks with two cabs. [/quote] Well the amount of learning in the plans is probably worth their weight in gold at this point, so I shall order some right now!

[quote name='Balcro' timestamp='1410292765' post='2547974'] In your last post (with the two graphs) You've set the input to 200 watts. [/quote] Yes, I forgot to set it back to 100 watts before I took the screen shot, lol However, at 200 watts, the 2x12" setup actually copes, which is pleasantly surprising. [IMG]http://i.imgur.com/wRrexwF.png[/IMG]

I had a look at - [url="http://billfitzmaurice.info/Simplexx.html"]http://billfitzmauri...o/Simplexx.html[/url] - sorry if I'm being an idiot again, but I couldn't see what drivers I'm supposed to buy for them...? I'm basically trying to stick to Neo drivers simply because I live on the first floor and have to carry the things up and down stairs all the time. Is there much cost difference in building two 1x12" rather than one 2x12" ? ...and the only power tools I have take batteries, so the idea of the plans being simple is VERY appealing! lol

That's what I was thinking - certainly on a first build anyway. I think the time to be looking at expensive grades of ply etc. is probably second or even third build, if I decide to, when I've got a better idea of what I'm doing. If it were a big cab. where there's larger panels to resonate I can understand it might make a little difference. Gold plated plugs just look cool... that's the only reason I buy them, lol

I've never tried to use a fridge as a speaker cab... if I ever joina punk band I'll give it some thought! Got me rethinking now... 2 x 12" might be better? - smoother overall response in a small cab than a single 15"? [IMG]http://i.imgur.com/YuSx3sM.png[/IMG]

Not boring at all - I'm finding it all fascinating (even if I'm not any good at it yet).

I've seen everyone recommending "void free Baltic Birch" plywood, but this seems to be hard to get hold of, and very expensive. This is my first build, and I've never done a cabinet before, so I expect to make a mistake or 10 along the way... hence I'm a little concerned about spending a fortune on wood. If this is a relatively small cab (120 Litre) will it make much difference to the sound if I were to use relatively cheap plywood, 12mm, and brace it? I was thinking of putting a + across each face (except the font obviously) and possibly ++ across the back. I realise the finish may not be as good, but then with my currently very novice skills I'm expecting to cover or paint the cab anyway, hence the wood itself wont really be visible.

Ohhh boy... for somebody about to try building their first cab who has a fixation with LEDs, this is NOT the thread I should have started looking at... That speaker cab is fantastic! (Might be a little out of place in our blues band though)

Ok (feel free to call me an idiot any time you like, lol) ... at least I'm trying though! So, I'm looking to get the most output I can over 50Hz, but avoid getting the 41Hz low E dropping too far down that steep slope, otherwise it will be much weaker than the other notes... yes? That's making more sense... as now I'd be tuning the box to 46Hz, which is as high as I can go before the 41Hz starts to massively drop off... [IMG]http://i.imgur.com/O3dGVIr.png[/IMG] ...am I making a bit more sense?

Try replacing the stock valves with some nicer ones. I replaced the valves in my Traynor YCV40 with some GEC tubes (new old stock) and it sounded much better. They were relatively new Sovtek valves I was replacing, so I do wonder if some of it may be down to simply valve characteristics. Even though the valves are rated the same the output jumped up a little bit and it sounds a bit punchier - maybe a little better response in the mid-range? Whatever it is, I like it. As for the link... I'll pop off and shoot myself later, lol

Now I have WinISD Pro working, it makes more sense! The normal WinISD doesn't have Maximum SPL etc. so the only thing I had to look at was what thisseems to call "Transfer function magnitude". I can see how the tuning is affecting the Maximum SPL now - makes far more sense! So my bottom E (which in some blues numbers is played a lot) is 31Hz fundamental. Having done some more reading that seems to be saying that the main amount of energy is at 2x fundamental (62Hz) with the "definition and punch" being somewhere up in the low kHz range. I sometimes tune down to D (28Hz) so that would mean most energy at 56Hz.... alarmingly close to the 45Hz-50Hz you recommended. I then played around with the tuning, looking at cone excursion and Maximum SPL, and it seems as if 38Hz isn't that much different to 47.5Hz overall, except the 38Hz produces more at the fundamental for the bottom E. [IMG]http://i.imgur.com/Po4sHgl.png[/IMG] [IMG]http://i.imgur.com/ibV59T3.png[/IMG] Is it just the slightly higer Maximum SPL that makes the higher Hz a better choice, or would the 38Hz be better? Also, looking at the somewhat alarming cone excursion graph, should I be putting a passive highpass filter on the speaker to protect against any very low frequencies (thud from an amp etc?) ?

I freely admit the whole "match the amp watts and speaker watts" thing has had me confused for a long time. I never seemed to get a conclusive answer to whether you should have speakers more powerful than amp, or match, or amp more powerful than speakers... This link suddenly turned a light on for me - I think I get it now! - so I'm sharing in case others find it helpful too. http://brain21.net/blues/blog/?p=432

Ok... but if tuning the cab lower gets rid of the hump, and doesn't seem to make a huge difference to SPL on the graph... why is that bad? ...can't I just turn the amp up a tiny bit more to compensate? (I expect I'm missing something crucial here, but I don't know what)

I tried to enter the params from the spec sheet into WinISD Pro, but it doesn't like it... [IMG]http://i.imgur.com/2woU7wn.jpg[/IMG] Does anyone have the correct parameters please?

Ok, so I downloaded WinISD Pro and tried to put the parameters in direct from the spec sheet.... same as I had in WinISD... http://www.eminence.com/pdf/Basslite_C2515.pdf This happens... [IMG]http://i.imgur.com/2woU7wn.jpg[/IMG] ...oh. Bugger. Now I don't know what to do.

[quote name='Bill Fitzmaurice' timestamp='1410121810' post='2546410'] Why tune so low? Maximum output demands, even for a low F# six string, lie between 40 and 70Hz, so you should be looking at the maximum SPL chart to find the tuning that gives the best result in that range. Tuning lower than 40Hz robs you of maximum output in the 40-70Hz bandwidth, and it makes the cab larger than it needs to be. If you have a 4 string you should be tuning even higher, 45-50Hz. [/quote] I freely admit this is because it's my first time trying to build a cab, so I'm not that sure of what I'm doing. I thought I was supposed to be trying to eliminate the "hump" on the gain chart? I've obviously confused myself somewhere... point me to something that I should be reading?

[quote name='Bill Fitzmaurice' timestamp='1410094346' post='2546001'] How did you arrive at that?[/quote] Well unless I'm using it wrong, WinISD.... I've since been playing with it and now I have a 120L box (50cm wide, 80cm tall, 30cm deep) and it seems to say that to tune to 30Hz I'd need 4 vents, 10cm wide, 3cm high, and 28cm deep (most of the depth of the box)... hence I thought I could just put a false bottom in with a 2cm gap at the back and a hole at the front for the bass port, and just use some 32mmx32mm batons to split the port into 4 channels. Am I wrong? The only reason I'm aiming for that sort of size is that I know it can fit into the boot of my car without having the seats down, which is extremely useful.

I've moved, and as a consequence, I actually have some space to build the DIY cabinet I wanted to make a year ago! Hooray! My plan is to start simple - I'm thinking good quality driver, simple cabinet, make it look nice, and enjoy it. If it works well, I can always think about building a better one, and transfer the driver. It'll be a simple box, rectangular bass port, 130 litre, tuned to 25Hz (hopefully), built with 15mm void-free ply, braced, and lined inside with 26mm dacron. Fingers crossed! However, I don't really want to build a combo (although that's what I'm still using now), and the idea is not to have to take my existing heavyweight amp. I need an amp head! I like fairly deep bass tones - I mostly play blues and soul, so it's not thunderous loud rock. I would like a head that's going to make the most of that driver, and give me a nice wide range of bluesy, jazzy tones to play with, dipping into the odd bit of funk/slap or rock for the odd number we do. My current Peavey 115S combo seems to manage pretty well across the board for this, but I'm hoping I can at least match it if not better it with my first build (too ambitious?) I want to spend as little as I can get away with, and I'm happy to buy second hand, but not sure what to look for. Recommendations please?