Phil Starr

[quote name='ivansc' timestamp='1447155155' post='2905277'] Depends how you interpret "dud". Presumably you did look at the bass when you bought it but assumed that you could fix the bent neck. Unfortunately in my book that would imply that you were aware of there being a problem and accepted the instrument warts and all. But I would still go back to the bloke, show him the issue and see if he is prepared to make an accommodation with you. Good luck! The sad thing is, he probably sell it like that in good faith. [/quote] this is about right. By examining the bass there is a fair argument you accepted it's condition, or at least that's what he might argue in court. I think he probably did sell it in good faith but it is hard to know. You can't really prove he knew of the fault and he can't prove it was sold as seen, unless he had something written in his ad on ebay. In that situation the best thing is to try and resolve the thing by talking. I had a similar situation when a Takamine I bought through ebay arrived with the pre amp not working. I contacted the seller who insisted it was working when it left. I got quotes for a repair and he paid £100 towards it. It turned out to be a broken connector in the pre amp which I repaired myself but by talking we avoided any dispute. I've also been through the ebay dispute resolution process which was painless and I got my money back from ebay. I assume they then got it from the vendor but that was their business. I got the impression that the right is assumed to be with the seller. Check what ebays conditions are though, there is probably a time limit. Good luck, it is horrible to be in that position.

[quote name='dave_bass5' timestamp='1447081469' post='2904656'] As xgsjx said above, i too always just thought 8 ohms was 2/3 of the full output, but obviously thats not the case. [/quote] It was a good question. obviously the power can be 2/3 or 1/2 depending upon the power supply. I think my old MAG600 was about 2/3 and it isn't a bad rule of thumb but that's why it isn't a fixed proportion. theoretically double but a bit less in practice.

Hi Dave, you have the answer already from Chienmortbb. I'll see if I can explain differently. An amp can only produce a certain maximum voltage into a speaker and that determines it's power output. However if you reduce the ohms the speaker will take more current and more power with the same voltage, so if you have an amp that produces 100W into 16 ohms it will produce 200W into 8ohms. Theoretically this means the amp could go on doing this so 400W into 4 ohms and 800W into 2 ohms. The problem is that this needs more and more power from the amp and the current demand keeps rising. Eventually either the amp gives up and goes up in smoke, automatic protection kicks in, or the power supply inside the stops making extra current. Usually the power supply is the limiting factor. Power supplies are often expensive and if they are transformer based really heavy. This is why most amps don't like 2ohms and why they can't produce twice the 8ohm power into 4ohms. In practice I doubt you'd notice the difference between say 350W and 400W so it doesn't matter. That's another story though. So the answer to your question is 'because they have differing power supplies.' On a practical level I don't think you need to choose an amp on the basis of 25% more power, you just won't notice it. *Valve amps work slightly differently as they have a transformer to adjust to different speakers so they will produce the same power if you have an output for that ohmage speaker.

[quote name='chrisanthony1211' timestamp='1446887181' post='2903127'] I know this will depend upon the size of the speaker, but is there any generalisation about how much lighter neo speakers are? I'm thinking about picking up something like an SWR redhead and making it a little lighter! Would swapping out the speakers make much of a difference? [/quote] I'd think you'd be looking to save a couple of kg per speaker looking at Eminence 10's, actually about a 50% reduction, somaybe 5lbs overall. The Redhead weighs in at 96lb so it is still going to be pretty heavy. The other problem is that speakers may not be a direct swap, in fact probably won't be, so you will get a different sound from the original Redhead. In an extreme case you may even get a sufficient mismatch between cab and speaker for the bass performance to be so compromised the speakers could be damaged. If you decide to go ahead then ask someone here to check for you.

Like the OP I've always been a non singer. Humiliated by teachers at school which didn't help but although I could hear it in my head what came out of my mouth was never what I expected or what I heard. I remember several times people playing a note on a piano and asking me to sing it back, I couldn't get close. A few years back I discovered when setting up the PA I could hold a note and sing along if the monitors were turned up. In other words I could sing in tune when what I normally hear was blotted out by the PA. I genuinely can't hear my own voice. Since then I've been asked to do the odd backing vocal and had a go, Things like the doo-be-doos in Chelsea Dagger. No-one has thrown anything yet. The good news is it is getting better. You really can learn to sing, painfully slowly and with the usual two steps forward one step back but you even have muscle memory, once you've nailed something it stays as long as you keep practising it. It's something that seems to come so naturally to most people that you feel like constantly giving up and I'm sure it still isn't a nice sound but just filling out a chorus helps the band and three of us singing ups the audience response. I have no idea what is going on, why I can't sing without a monitor when everyone else seems to have that trick and I'm so self conscious (a rare and salutary feeling for me) when I sing, but if you want it enough keep trying.

[quote name='Dad3353' timestamp='1446683508' post='2901521'] All precious stuff so far, with the different spotlights on the subject adding to the usefulness. If I may, I'd like to have some expert opinions on the rather modern tendency to use, not simple distortion, but outright fuzz on bass, giving a waveform much closer to square wave than sine. Does this not have a bearing on the cone behaviour, as it is effectively receiving almost a DC element for a good deal of its cycle. Would that increase the heat dispersion problems..? Is this negligible, or something worth considering when estimating power handling requirements for speakers..? Please ignore if too far off topic. [/quote] That's kind of true, and I like the idea of different spotlights, often a difference of technical opinion is down to a different perspective or at least answering a different question. For example what Bill says is true if you have a speaker with a crossover and a tweeter, and is the reason why you need to be so careful running a distorted signal through a poorly rated horn. If however you are putting the whole signal into a single drive unit and the signal is reaching the maximum voltage the amp can produce then the square wave will have 1.414 times the energy of an undistorted sine wave. The Cone and the coil will be travelling the same distance in each case so air movement and air cooling will be similar, depending just a little on frequency. However you can potentially have a little more heat to dissipate with a distorted signal and what actually happens will be down to the detailed design of the speaker and the amplifier in question. In practice of course even if you have a pure square wave you will still be producing notes, which will have a loud start and fade with time and then a gap before the next note, even with metal So you may be producing 300W peaks or whatever but the power averaged over a few minutes will be a lot lower, allowing the speaker to cool between bursts of power. Your poor tweeter though may be rated at 30W thermal in a 300W system and if you have a crossover the extra 0.414 of your 300W will be diverted that way so without some protection it is going to smell of scorching.

There's little point in spending £200 on speakers when you can get a used cab for £100. Everyone is giving you the advice I'd give you. Get a used Peavey, preferably one with the BW drivers in. Peavey bass cabs are great heavy things but sound pretty good and are really reliable and crazy value for money. I've got an old 1x15 BXBW here removed from my rehearsal room, I'd happily sell for £75 if you want but there's loads out there. http://assets.peavey.com/literature/manuals/80300395.pdf carriage looks to be about £35 though buy used unless you have an overwhelming desire to build something.

[quote name='alexclaber' timestamp='1446649486' post='2901137'] It's extremely rare to blow a woofer with bass guitar without it sounding pretty distorted first. If something does go pop without any warning overdrive, especially something fairly new, then it's most likely to be a manufacturing fault. Phil, I'd say you've got things the wrong way around in terms of excursion for most half-decent modern bass guitar woofers. Older designs which don't have vented motors do indeed rely on the magnetic gap removing heat from the coil via radiation but most modern drivers have vented motors so getting the woofer pumping back and forth, even if the coil is moving out of the gap, will remove more heat via convection. Also, most decent modern MI/PA drivers use the suspension to limit excursion to reduce the chance of bottoming out or jumping out of the gap and have a decent margin between Xmax (where distortion tends to rise significantly) and Xlim or Xmech (where permanent damage occurs). Bass boost does tend to cause problems though, because most cabs are quite a lot less sensitive at 50Hz than at 100Hz, so you can put a lot more power in without getting a lot more sound out. Also, most cabs are tuned to the 40-60Hz region, which means the impedance is low so much more power actually flows in that region that at 80-120Hz, so you have a double whammy of it taking more volts to create the sound and more current flowing for the volts, so more true power hitting the voice coil. And at that low impedance region the woofer is moving much less because it's operating against the high pressure load of the tuned port, and the port is creating most of the acoustic output, so there's less voice coil movement to pump the hot air out of the motor. [/quote] I was trying to keep it simple Alex, and I'm making the assumption that an 800W 4x10 isn't using the same drivers you use. There are still a lot of ceramic magnet speakers out there that don't have vented motors, though you'd expect it with neo drivers at least. Even so I doubt that the cooling is improved by the coil leaving the magnetic gap. There's also the behaviour of the speaker below the tuning of the port to consider. Surely you aren't saying the speaker runs cooler when the excursion is pushed up by increased power? The OP asked about how to avoid blowing speakers and the best way is surely to avoid Xlim. I wanted to give a few practical tips which anyone reading could take to avoid having to replace speakers. I'm also not sure most bassists would recognise rising distortion in a gig situation with a set of cymbals by their ear, two guitarists going flat out and all sorts of pedals in their sound chain. I'd want the safety of my rig designed in and not dependant upon my noticing at the climax of a gig.

If you want some practical advice, with a bit of explanation? Understanding why speakers blow helps and there are essentially two reasons why they blow early. One is that they overheat and the other is that you push the sound levels up so high that the speaker moves so far the coil comes out of the magnet. The problem is that speakers are most likely to be damaged by the second problem of over-excursion but they are rated for the first problem by their ability to handle heat. So your 400W cabs should be able to handle a 400W amp all day, so long as you don't put bass through them. Sing as loud as you want or play a skinny string or anything above 7th fret on the A string you'll be fine. The problem comes when you go down an octave, making bass sounds needs you to shift a lot of air so you need more power and the speaker has to pump backwards and forwards more to shift all that air. Eventually it moves so far two things happen, either the delicate coil hits the back of the magnet or it moves out of the magnet gap, either way it gets damaged. Once the coil leaves the gap the cooling fails and the rating of the speaker goes right down. Your 400W speaker becomes maybe a 100W speaker. That's usually why they fail. So apart from using much more speaker than amplifier how do you stop it? You limit excursion. 1. Get a filter that stops the deepest bass (like a Thumpinator) 2. use eq wisely. A tweak on the bass boost (say 2 o'clock) will make your speaker work twice as hard. (10 o'clock half as hard) Never go to full bass boost unless you are absolutely confident you have enough capacity in the speaker. 3. watch the effects, an octaver means you need twice the power handling if you are going to play anything lower than 7th fret E. Amp modelling and quite a lot of effects boost the bass, using two in line can push this to unexpected levels. 4. If you want a bassier sound it is often better to cut treble and mids and then turn the volume up. 5. think about keeping the deepest bass out of your rig and putting it through the PA bins. If you really have to have that trouser flapping, deep bass, distorted sound then you are going to have to have more power and more speakers but the Thumpinator or similar will help a lot and they are far less audible than you might expect. BTW I think BFM was spot on, this failure was down to a faulty component and should have been sorted under warranty.

[quote name='Jono Bolton' timestamp='1446455545' post='2899401'] The cab has side mounted feet as well as the castors but even when I lay it sideways on the floor the vibration was still present. The head has just been cleaned out and all the pots cleaned so it's all working, but the noise definitely comes from the cab. I'll check the metal side stripes on the grille as they don't seem to be secured to anything at the front so it's possible they're vibrating. My head is an Ashdown ABM 300 which is reasonably small and lightweight, when I got the cab I tried it out with a Mark IV which may have weighted the cab to stop it vibrating. [/quote] Ok if I have this straight then your head is moving on the top of the cab and you have an audible vibration? My thought is the two may not be caused by the same problem. They may be of course. I had an unpleasant buzzing noise from mine. Upon examination the dustcaps in the centre of the speaker were loose and there was some separation of the corrugated surround from the cone. Not unusual in speakers of this age as teh adhesive becomes brittle with time. I carefully removed the dustcaps and glued them back down with Copydex, which is latex based adhesive. I then stuck the surrounds back with more copydex and used a paintbrush to then seal the whole circumference to the cone with more copydex. The speaker is still working after several years. You should be able to remove the whole grille assembly including the silver strips and operate the speaker without these. That will eliminate them as a cause. You can also remove the speakers which will allow you to go round tapping bits of cab to see where they are loose, if at all. Whist in there check the speaker cables inside aren't buzzing against anything.

Without any measurements to back this up it is fairly obvious that a lot of commercial cabs have a 'smiley face' engineered in. A typical commercial 12" cab has an Eminence driver, often a 'special' built into a small cab. I'm talking mid-range price here. If you look at the Eminence Beta http://www.eminence.com/pdf/Beta_12A-2.pdf it has a marked (3dB) peak in on axis response between 1 and 3kHz . This is typical of a range of commercial drivers. Put it into a small box (typically 1.25-1.75 cu ft, sorry Eminence use imperial units) and you'll get a roughly 3dB peak between 100 and 200Hz. So the midrange gap between 200-1000Hz is 3dB down from the rest of the speakers response in a 'normal' speaker. If you aren't used to anything else then a speaker without the same midrange dropout will sound middle biased. Which is 'wrong'? Well neither of them, people like the sound of a midrange suckout and if it isn't inherently built into the cabs response dial it in with eq, or with their bridge/neck pickup settings. Other people want to start with a flat response that they are then in charge of. That's what people asked for when we started this project and I think we met the design brief you came up with. I'm not being defensive I hope. The problem with a self build is you don't know what it will sound like until you build it and most people can't 'hear' a speaker from a graph and a set of figures. I want people to have a good idea of what they'll get. I think it's fair to say this will be a very open, clean sounding speaker with a bit more deep bass than most speakers but without the artificial warmth of many commercial units. It'll go very loud without stressing, respond well to eq tweaks and yes, you'll notice some midrange that might not be there in your old speakers. At some stage I'd love to run some measurements on commercial speakers and I'm planning on coming up with an 'old school' speaker at some stage.

My first cab, nice sound, but no fun to carry up a flight of stairs! As I remember they are on castors, check the cab is secure on the floor. You say there is no buzz and mention no unexpected sounds so I'll assume all is working as it should. Are you using a lightweight amp. The amp sits on the smallest most rigid panel so I wouldn't expect it to shed the amp. I never had this problem but was using the Peavey MK 3 amp which was quite heavy itself.

Ma[quote name='Merton' timestamp='1446374376' post='2898808'] Speaking of frequency-related hearing loss I tried that little slider and can hear nothing below about 35 Hz and nothing above 12kHz. I swear I did a similar test last year and still got to around 15 kHz, maybe my memory is also going :/ [/quote] [quote name='Chienmortbb' timestamp='1446378282' post='2898852'] You are lucky mine cars out at 10KHz [/quote] [quote name='Marvin' timestamp='1446388222' post='2898960'] Mine drops away at 8khz with nothing after about 13.5khz [/quote] Makes me feel better about my hearing Seriously though it might be the gear you are using, Proper over ear headphones are usually quite good but computer speakers or in-ears not so much. I use this test at least once a year http://www.actiononhearingloss.org.uk/your-hearing/look-after-your-hearing/check-your-hearing/take-the-check.aspx it does test your ears but there could be problems with the auditory nerves which won't show up in this test. Should wear ear defenders really but it is so hard to mix with them in.

It's probably been said already but If I'm a potential punter I just want to know where you are playing so put your gigs on the front page. If I'm a potential booker I want to know you are a proper band and know how to play. Video with a decent soundtrack is pretty much essential or a decent recording of the band as a minimum. I prefer a mixture of live and studio recordings but if the video is of you live then just studio recordings will show the band off better.

Warm soapy water (fairy liquid is fine) and a soft plastic bristled brush (old toothbrush) for getting into the little crevices, obviously making sure you don't get water inside the case. One trick some of the shops use is a bit of WD40 polished in afterwards. Gives it a nice shine at the expense of a thin film of oil.

[quote name='Mykesbass' timestamp='1446329591' post='2898670'] Yes, taken, and I'm only asking as I find this very interesting. Yes, over 7000 it does start to fade, but my point was, contrary to your statement, that treble seems louder than mid to me. Between 2000 and say 300 there was no real noticeable difference, but over 2000 up to 7000 it seemed to increase substantially. [/quote] there isn't really a definition of bass/middle/treble in truth. For most people the peak in hearing sensitivity is 3-4,000Hz as you see on the curves I linked to. If you are using the sort of Sennheiser in ears I use with my iPod then there are some very sharp resonances that you may be hearing, at the computer I use some fairly pricey Sennheiser HD595's. Funnily enough I was wondering if I ought to pm you to check for hearing loss problems but then thought 'he's using in-ears' I used to do this frequency test with students when I taught physics, and in those days my hearing followed the equal loudness curves curves in textbook fashion. Now there are all sorts of lumps and bumps in my hearing with age related hearing loss.

[quote name='Mykesbass' timestamp='1446326126' post='2898649'] Just tried that link, but it seems to go against your third sentence, as I found around 7000 Hz by far the loudest. almost painful at a volume where the mid range sounded pretty quiet. [/quote] 7000 isn't really between 2000 and 40Hz I trust if you continue going up the sound level fades out again above 10,000Hz. this is also age dependant and to a certain extent an individual thing but here are the curves averaged out for the population. https://en.wikipedia.org/wiki/Fletcher%E2%80%93Munson_curves

Unless you know the cab can be mic'd take the spare amp. You might be loud enough for stage monitoring but it isn't going to fill a big venue if you have a drummer in your band. We don't have enough details to be categoric but 15W?

[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.