Phil Starr

[quote name='4-string-thing' timestamp='1446291071' post='2898357'] I find this quite fascinating, my old Acoustic 220 is only rated at 180w at 2 ohms and only 125 through my 4ohm 2x15 cab. Yet, it as "loud" as my (modern) 575w Ashdown head through the same cab. The cab, which is also a 40 year old Acoustic 402 has a label on the back warning that sound levels may exceed 120 decibels. 120 db from a 125w amp..... Maybe thats just marketing hype too? All I know is, that amp has always been loud enough to cope with most bands I've ever been in (except one who were just ridiculous when it came to levels) And that it got no louder after about 3 on the volume pot! With regard to Phils comments about lumens per watt etc, when I worked for an electrical wholesaler selling LED lamps, people always thought cool white lamps were brighter than warm white, despite the same output. They may "look" brighter, in the same way that some amps may "sound" louder despite the wattages being the same? [/quote] There's a bit of truth in the cool white/warm white analogy. It may explain some of the perceived differences between your amps. Our ears are much more sensitive to mid-range frequencies than extreme bass or treble, they are after all the human voice frequencies. The difference can be more than 12db. I don't know the acoustic amp but I used to have a MAG 600 and it was far from flat with the mids pulled back, even with the controls set for level. If the Acoustic was more mid prominent it would sound louder. If anyone is interested try this. http://plasticity.szynalski.com/tone-generator.htm Use headphones and turn the volume down. You have been warned!! Change the frequency to 2000Hz and turn the volume up so you can hear the tone. Drag the frequency down to 40Hz which is around bottom E and it will get quieter, maybe so quiet you can't hear it any more. The volume hasn't changed it's your ears that aren't working as well with the bass.

[quote name='Twigman' timestamp='1446247406' post='2898160'] The wattage of the amp is irrelevant really. It's down to how efficient the speaker is in converting that electrical power into moving air. [/quote] Sorry that just isn't right. It rouses the science teacher in me. How loud an amp and speaker are together is a very simple equation. Volume increase is a logarythmic scale so to keep it simple you add 3db every time you double the power (the watts) For example if you have a speaker that produces 96db at 1Watt then it will produce 99dB at 2W, 102db @ 4W and so on. For bigger increases in power an even easier figure to remember is that ten times the power gives you an extra 10db. and 100x the power 20db extra. So the same speaker will make 116db @100W If you took a speaker that only turned 1W into 93db of sound then it would take 200W to make the same 116db and if you had an efficient speaker of 99db/W it would only take 50W to make 116dB. You need both the Watts and the efficiency to calculate the sound level. Neither is irrelevant. 120db will make you as loud as almost all drummers. By the way the same law applies to drummers. If a drummer is twice as powerful you will get an extra 3db and an extra 6db if he or she is four times as powerful. you don't often get drummers eight times as strong as other drummers so this is the normal range of the loudest sound difference between them.

[quote name='Grangur' timestamp='1446212524' post='2897778'] +1 A Watt is 1 volt delivered at a rate of 1 Amp. This has nothing to do with output volume. Using Watts as a gauge of volume is like taking the mpg of your car a a gauge of speed. For my job I sell lighting. We always are discussing the output Lumens per Watt. Surely with a stack config we should be talking about decibels per Watt? [/quote][quote name='Grangur' timestamp='1446212524' post='2897778'] +1 A Watt is 1 volt delivered at a rate of 1 Amp. This has nothing to do with output volume. Using Watts as a gauge of volume is like taking the mpg of your car a a gauge of speed. For my job I sell lighting. We always are discussing the output Lumens per Watt. Surely with a stack config we should be talking about decibels per Watt? [/quote] [quote name='razze06' timestamp='1446213412' post='2897792'] I wish people used this metric to describe their products. Got bless science and engineering [/quote] [quote name='Nicko' timestamp='1446214288' post='2897801'] The last thing we need is manufacturers confusing us with decibel ratings. [/quote] Rich is right, that's a good analogy. When lighting a room you don't really need to know the power, you need to know how much light it gives off. The electrician who wired the room might want to know the power so they can calculate what cables to use and the bill payer might want to know what the bills might be but the brightness is the thing you want to know, and then basically 'is it enough?' And if you know how many decibels it produces at one metre you know how much it produces at two or even at the back of the room. It is slightly complicated by the frequencies, it's harder to see in just blue light or just red light and you may prefer warm white to cool white just as you may prefer to emphasize certain frequencies from your rig. So if you want to see if a bulb is powerful enough look first at how many lumens to see if that 5w LED really is equivalent to a 60W incandescent and if you want to see if your stack is loud enough ask how many decibels it produces. It won't tell you much about the colour of the sound but it's the best single measure you can have of how loud it will go. That's why they don't often tell you that figure. Decibels every time before watts, though of course amps alone don't produce any decibels without a speaker on the end.

[quote name='LukeFRC' timestamp='1446163191' post='2897493'] have you got a commercial bass cab to hand that doesn't sound prominent mids? I wonder if you measured that and your cab side by side you would be able to see on the charts what the other cab was doing that made your build seem "middy" [/quote] We are running this on a shoestring budget and this is something Stevie and I have privately talked about doing, but can't afford. It would need the goodwill of some of the Southwest bass players to lend us their cabs for measurement. My theory is that most of the commercial cabs I've heard have a 'smiley face' response but with little deep bass. This cab has a broadly neutral response so someone listening and expecting the smiley face will perceive the difference as a prominent mid, compared with the mid shy cabs they are more used to. Unless we run measurements though we are just guessing, though hopefully intelligently.

[quote name='Beer of the Bass' timestamp='1446123798' post='2897071'] Interesting that you should bring up the Beta 12a, as I picked one up recently that was going very cheaply used. When I get around to it I intend to try it in something close to the cab design being developed here and see it sounds. I have a GK MB200 at the moment and intend to mess around with low powered valve amps at some point in the future, so it may be that the Beta will do a decent job for my needs (and if not, I'm not out by much if I try the Beyma later). Certainly people seem to enjoy them in those TKS cabs, assuming that's what they use. [/quote] If you go back to the beginning of this very long thread you'll find that we modelled the Eminence Beta (and the Kappalite 3012HO) as alternatives to the Beyma. They both modelled very well, the only reason for choosing the Beyma over the Beta was the much better excursion of the Beyma meaning it would handle deep bass at high power better than the Beta. If you could put up with some limitations on the deep bass then the Beta would be an excellent drop in replacement for the cab with no mods needed. I haven't gigged this cab with the Beta The Kappalite HO would be a great speaker to put in but would cost a lot more than the Beyma with the main advantage being weight saving. In the 12mm cab this would give you a truly lightweight option around about 12kg. We haven't tried the HO as yet but I see no reason why it wouldn't work as a great cab.

Hi Stevie, before we get carried away these traces aren't so different. The troughs at 1.1and 3kHz and peaks at 2.1,3,0,3.3 and 4.5khz pretty much align and aren't that big. only the peak at 700hz is above +/- 1dB. Did you try swapping the speakers between cabs? Is it possible the cabs are contributing to the differences in the plots? do we know it is solely down to the drive units? I'm assuming this is the small signal response measured at about 1m? I'm quite willing to believe that either of the drive units does not meet it's spec. or has been damaged during the build process but I'm not completely convinced about this either. What do you think?

I'd start off by looking at the AER combos I love the sound of the AER Amp One when I've heard it live.

[quote name='Thunderpaws' timestamp='1445780134' post='2894072'] Phil, at some point in this thread I remember you hinted you were going to try and drop the volume of the cabs. Did you ever get around to doing this? [/quote] No, but I might try it after I've published this design. I tend to take too many things on, so I've promised myself I'd get this out asap and not start anything new. If Stevie or I come up with anything that improves these cabs we'll simply offer a Mark II design. I may put out the 15 that I've built to use whilst others are trying the prototype 12's too. I also have a 2x10 ready to go. [quote name='JTUK' timestamp='1445781127' post='2894090'] Hmmmm there is where I see a problem with people talking about mids... and they want them as they can actually hear themselves, but then don't actually like the sound solo'd..but hey, that is ok and it works in the mix. I'd be thinking this is masking up a load of masking.....and at some point people will hear the bass on its own..and if at that point the sound is poor or not friendly to the ear..?? To me..wrong way to go about this, definitely. [/quote] There is a lot in what you say, It's been the biggest problem in designing a cab for other people. A PA cab is easy, it just has to put out what you put in so you choose your drivers appropriately and optimise the cab and crossover for flat responses. A single driver instrument cab is much harder. Most people play with highly coloured commercial cabs. Or well voiced if you like the colouring This cab is essentially comparatively flat which is what people asked for, and it has the potential for a lot more high power deep bass, again specified by early contributors. Then people comment about the prominent mids and the boomy sound caused by the flat (ish) mid compared with normal mid suck out and by having more bass at lower frequencies than they expect which then excite room resonances they didn't know about before. The advantage of a flat cab response is that it is highly responsive to eq. Look at the photo and you'll see I've dialled in an old school frequency response on the Hartke's graphic, left since my last gig with the 12's. There isn't anything I'd call right or wrong though. It's OK to go for flat and neutral and then use eq and fx to get the sound you want but just as OK to find the perfect speaker to go with your perfect bass and amp to get the sound you want. The second way will probably take a lot of shopping though before you stumble across the right mix. It might be fun to design an Ampeg voiced speaker from a 2x12 though.

[attachment=203570:1x12 slot port.jpg][attachment=203571:1x12 slot port with amp.jpg] never did manage to figure out how to do this properly but this should be a pic or two of the finished speaker. There will be a proper grille fitted once I've got the speaker back from Stevie which should lose the home build look of it. My goodness it worked even if they are quite small.

There's a parallel thread going on in the Southwest bass bash where the general opinion is that B sounded better because of the extra mids. This is based on people trying it out themselves rather than on the two recorded snippets. As the person who designed the cab I'm thinking 'I should have designed the resonances out' which is interesting. Any engineer is going to be tempted to go on trying to get things 'right' but an instrument cab needs to be 'musical' first and foremost. The differences between the cabs aren't that great and Stevie is continuing to run tests, we are going to fiddle with the cab stuffing a little but I think we are almost there and will start to write up the design this week.

[quote name='Chienmortbb' timestamp='1445727084' post='2893784'] Glad you got Black Velvet fixed. It was always my Bette noir. I know trace liked MDF for cabs as they thought it sounded better than Chioboard or ply. That was from one of the engineers there not the marketing dept. [/quote]It does sound better but it is soooo heavy and if it gets wet it expands and breaks down so it isn't a practical material for instrument cabs really IMO.

You've got me worried about the buzz, I'm hoping it is no more than the leads inside being loose. I didn't notice a buzz on the recordings or at home so I'm assuming that the cabs were moved at some stage and whatever buzzed stopped buzzing. I really had to rush the cabs out of the door to get them to the bash so Its quite possible the cables may have touched against the cone at some stage It's interesting, Stevie and I both preferred Cab A for it's cleaner sound whereas it looks like a couple of people preferred the other cab for its extra mids, which we think is down to cabinet resonances. The bracing shifts resonances upwards in frequency so it isn't too surprising to find this. Stevie is running a few more tests but it looks like we are just about finished with this design. I'll start writing it up so anyone who wants can build a copy.

[quote name='Mornats' timestamp='1445712138' post='2893700'] A great sounding cab that looks cheap with no brand name on it could be ideal for those dodgier venues. I preferred cab B - the one on the right. I think it was the one without the bracing? It had clearer high-mids if I remember rightly. If I needed an extra cab for my MarkBass CMD 121P combo I'd definitely consider that one. [/quote] Was your favourite the one with the slot port or the four round ports? I think they got muddled at some stage in the bash.

A possible solution. Guitar amps are more directional than bass amps and unless he has a decent amp stand his amp will be pointing at his knees. This means he will only be hearing the bass from his amp and not the screetchy high notes. He is probably eq'ing so it sounds good where he is standing and he is turning up so he can hear clearly when well off the axis of the speaker. Explain politely you think this may be happening and ask him to lean the amp back at rehearsals so his ears are in line with the speaker axis. If he balances the sound then it should sound better for everyone. Then he needs to get a stand so the speakers are pointing straight at his ears at gigs too. I've used this tactic successfully more than once.

Thanks for the comments, and thanks to Woodinblack for posting the sound clips. Keep them coming. Sorry about the Barefaced look, (I hope Alex doesn't see this) the 12mm cab was the test bed prototype aand hasn't been finished at all other than a coat of blackboard paint so it could be used at gigs. The other was given one coat of Tuffcab and went out to the bash with the paint still wet! Thanks to GrahamT for transporting it for me. I'll fit a proper grille when it comes home. The point about a homebrew is that you make the choice of finish and handles etc. They can look very professional or as amateur as you like.

If you wanted to use two then you'd have to get a series lead made up so you presented an 8ohm load to the amp. I'm sure you could ask OBBM to make one up for you. Where the volume settings are can bear little relationship to the actual power and Alex Claber has a sticky in the amps and cabs forum that explains this. You can't trust speaker ratings as anything other than a rule of thumb. The speaker designer can't control how you set up your eq or how you play. Your speaker will probably handle 300W at higher frequencies but below 100Hz there may be times when 50W would take it out of it's safe zone. That's normal and true of many commercial bass speakers Whether that would cause a problem is down to exactly how you use your speaker and how you play. If you use a lot of bass boost or an octaver it might well be troublesome. You might get a thumpinator which would make a huge difference to the safe operation of a small speaker like this.

[quote name='pete.young' timestamp='1445687565' post='2893410'] That's triggered an odd memory - I'm sure I read somewhere about some cabs that used MDF for the front panel and ply for everything else, but I'm damned if I can remember where I read it. [/quote] It was common at one point for cabs to have a ply skin (top,bottom, sides) because it was tougher but mdf or high compression chipboard for the baffle and rear panel to save money and get less resonance.

[quote name='tauzero' timestamp='1445678023' post='2893266'] I prefer A from that small sample but I'd want to spend a bit more time with them and try them with songs I do. How heavy did each of them finish up? [/quote] the 12mm was 14.kg ish and the 18mm cab was about 1.5kg more. If I'd made the ports with plastic pipes in both cabs I think the difference migh have been down to nearer a kg. I haven't actually had time to weigh the finished 18mm cab before I sent it off to Stevie

[quote name='Chienmortbb' timestamp='1445601082' post='2892719'] I preferred A in the first two sample. In the rehearsal, I can forgive your hesitation. Black Velvet is a deceptive song in that if is all about the bass and the passages ate the end of the chorus are a B. I read that the bass line on the record was a mixture of real bass and synthesised bass. Or maybe that was my excuse as I found it hard, On second and subsequent listenings the B speaker seems mid heavy or bass light. I am using AKG 450 headphones from an old macbook pro so the quality should be OK. [/quote] you were supposed to be judging the tone of the speaker, not my bass playing And you are right about the end of the chorus, fixed now.

[quote name='Beer of the Bass' timestamp='1445509347' post='2891956'] I like B better out of those recordings, though the difference doesn't seem huge. Both are a more pleasing tone (to my tastes at least) than the recordings of the Markbass combos from the same day. [/quote] You've no idea how encouraging that is. I know these speakers model well and that they are hugely capable of handling bass and high volumes well but the voicing is something else. I'd feel really responsible if no-one else liked them. That's the first ever comment to directly compare them with a commercial cab.

Another sound clip for you. This is me, so forgive the playing, it was our first run through of this particular song so there is some hesitancy but you can hear the tone quite well. It has what I think of as a slight 'thoatiness'. This is using my Hartke HA3500 and I think I had my Fender Highway One Jazz for this. Can't remember all the eq but the deep bass is rolled off at 30hz on the graphic cos i always do that. https://soundcloud.com/philstarr-1/black-velvet-27-april/s-wnPYC

I'd love to hear any comments about the homebrew 1x12's if any of you tried them. Are we in the right ballpark given that these would cost you less than £150 and will go very loud compared with most commercial 1x12's. Any feedback will be used to improve future designs.

Well the OP did start off saying about the drums being miked up, so this is a band that wants to be louder than a drumkit allows, without that you are pretty much stuck at playing at the drummer's level. I feel sorry for drummers, even if you find the fabled drummer who can play quiet I'd still want to use the whole dynamic range of my kit. I'd find it tough if someone told me I could only play bass gently. You could have louder and quieter kits but who has the space to store multiple kits never mind the expense, though I suspect drummers have GAS too. No sympathy for the over loud guitarist though. The rot was there from the start. When I ran sound for bands in the early 70's you struggled to be heard with PA limited to a pair of WEM columns. Instrument amps had to reach the back of the room unaided so the Marshall full stack was born. Singers sang in their higher range just to cut through, a lot of rock norms/cliches were born of necessity. Now gear is cheap and the easy (lazy?) way of playing classic rock is to just copy the gear from your heroes, who would have killed to be able to use the equipment we have now. GAS is a problem too, most bands are amateurs whose hobby it is. Buying the best gear you can afford and lots of it is part of the fun, once you have it you've got to give it a run out haven't you. Even I had a lot of fun at one gig where my drummer shouted at me to turn up and I did. Spent the first half not needing to pick and damping the strings which were singing with feedback, and oh the tone Very gratifying to have said drummist saying he couldn't hear his own snare drum. He hasn't asked me to turn up since strangely. But you can't sound your best at the volumes a lot of pub bands play at and I'm with the people who say you should be playing for the audiences not yourselves, especially if someone is paying you to play. There are lots of good technical reasons why keeping sound levels down is better and really there is no excuse.

[quote name='Woodinblack' timestamp='1445454474' post='2891665'] There was quite a lot of background noise in the recordings, and the first set of recordings weren't flat. Here are two short recordings of the two cabs, playing the same phrase with both on the same amp (markbass set eq flat), played next to each other. There is more but it is very noisy. However, the conditions are very similar (and distances the same) as the test on the somerset bash, so these could easily be compared with the markbass recordings. Anyway: A: [attachment=203220:SpkrA.wav] B: [attachment=203221:SpkrB.wav] [/quote] Ok the two recordings are of two cabs both fitted with the Beymas One has a 12mm wall, tubular ports and is extensively braced and the other has an 18mm wall, slot port and no bracing. Both are 50litre cabs tuned to 50Hz. I don't know which cab is which and embarrassingly I can't be sure from the recordings which is which either. I have gigged the 12mm cab extensively but only had 10mins with the 18mm cab before giving it over to Stevie. I wasn't there when the recordings were made at the Southwest bass bash. The differences aren't huge but I do have a preference. I'm not saying though until I hear what you think. If you can't open the recordings I found Windows Media Player opened them but I'm told you can copy them onto your desktop and rename them as wav files as an alternative. Though weirdly Basschat has done this for you when I used Woodinblacks post as a quote

Use the curtain pole to cross brace and stiffen the cab internally