Phil Starr

As you are an electrician I'll assume you know about watts,volts amps and ohms law. the trouble is that speakers and amps aren't rated in the same way because they don't work the same way and the processes by which they fail are different.. Excluding old age speakers fail in two ways. They can be driven so hard that the coil leaves the magnetic field and suffers mechanical damage when it returns, in any case it will sound crap when it reaches this stage. this is the excursion limit Bill talks about and is a real problem with bass speakers. It isn't usually mentioned in any of the cab makers specs. The second and probably most common cause of failure is burning out. With 300W going through a tiny copper wire it gets hot (200C isn't unusual) and eventually the materials in the construction of the voice coil break down. This is the thermal rating, the 600W that Orange rate their cab. The problem is in measurement and interpretation. You can't just feed DC current through the speaker because in real life the movement of the cone creates a cooling effect. For a long time a 1000Hz signal was used as a test signal but this doesn't work for all speakers, like horn drivers which only operate at very high frequencies. Now the most common method is to use some sort of filtered mix of a wide range of frequencies (often called pink noise) as the source. Pump this continuously through the speaker for several hours and, if it survives, that is its rating. There are a number of international and national standards for doing this sort of test but basically this is how they work. The problem is that speakers don't run continuously like electric motors so this isn't a very fair test. Music has loud and quiet bits and in the gaps the speaker cools down. So long as you don't distort the sound speakers will handle short bursts many times their thermal rating. Hence the 'normal music programme' and 'peak' ratings many manufacturers give. So you can use a 1000W amp with a 250W speaker so long as you don't distort and so long as you don't push it beyond its excursion limits, which you probably will as a bassist. Amps are rated differently. By and large it is very hard to break a well designed solid state amp as they have protection circuits built in which limit the power when you push them hard. However they will only swing a certain voltage, just below the power supply voltage and then they run out of volts and distort. Their ratings are then given at the voltage where distortion cuts in. As an electrician you will realise that applying a voltage across a lower resistance will give more current and power, so adding an extra speaker in parallel draws double the power from the amp. In practice the power supply in the amp will be limited to a certain current and so the full doubling won't happen so it is a rare amp that will actually double its power into 4ohms from 8ohms. Just to complicate things a little as the amp warms up the resistances (especially in the power supply) increase so the current available is less in a hot amp than a cold one. Valve amps run at very high voltages and have transformers to match the speakers so provide the same power to any speaker they have a tap in the output transformer for. So, don't get too hung up about wattage ratings, most of the time you will only be operating at a few tens of watts or less anyway, The extra power is only to keep the loud bits clean. It's unlikely you will ever really need more than 200W for bass so any amp that gives at least 200W into 8ohms will do nicely. Most speakers will handle several times their rating of undistorted music but as a bassist you need to be aware of the possibility of over excursion. If you hear your speakers distorting at high levels on the low notes you need to turn down or roll off the bass and fairly promptly. I'd roughly match the ratings of my amps and speakers but I wouldn't worry too much if I had 1000w of amp going through 800W of speaker, frankly at that volume I'd be more worried about my hearing than my speakers. Choose something that sounds good, try it out before you buy.

[quote name='skidder652003' timestamp='1348602618' post='1815917'] purely out of interest!!? if i enlarge the ports to 100mm now whilst waiting for the speaker, do you think it would improve the current ashdown driver? [/quote] You'd only notice a difference at high volumes and you would need to re-tune the cab, the bigger the ports the longer they need to be. In a way it is a little like changing strings, you need to re-tune after you change them! The reason the Ashdown holes are causing concern is that at high volume levels a lot of air needs to move in those ports and potentially that causes noises you don't want. The Kappa is going to be louder and move more air making the problem worse. If you want something to do take the speaker out and measure the inside dimensions and within a day you will have someone calculate the port size for you. If you wanted to you could fit ports that would tune for the kappalite not the Ashdown you have. The Ashdown would probably work OK with these ports so you could put it back in and try it if you wanted.

Should have said that is the only problem with Blue Aran. Good to deal with but a bit slow. You can track the progress of your order on the website though.

Just an update, I wanted to sell this monster for ages but decided to try and get used to its bad behaviour (neck dive and twisting away from you to save anyone from having to search the thread) Less than a week ago I was all ready to sell it out of frustration, the neck is a wonder to play and the sound is fabulous but the playing comfort is maddening. Anyway four days ago I shortened the strap, really silly short, I look like I should be playing in a sixties band. All the problems disappeared pretty much, though it feels really odd changing to the T-bird. Last night I gigged it for the first time, [b]I love it![/b] The sound is just wondrous and strapping it on feels like becoming Jim Carrey in The Mask. So if you have one of these use a wide strap and straplocks, and shorten the strap just like one of the guys said and it cures 90% of the neck dive and twist, then you can enjoy the good bits of this amazing but irritating bass. Thanks for your help everyone.

I think we are all pretty much in agreement. The Mag is the better cab to adapt as the size is a pretty good match but you ought to put in bigger ports. All the air shifted by those big speakers (and remember they move further than the old ones has to exit those tiny ports at resonance and the air will be doing a significant speed and will make chuffing noises. Aren't the ports on the back of the Mag? If so how worried are you about how they look? You could probably find a chippy to cut the holes for you for a few quid if you are nervous about it. Get hold of the porting first though, I use black soil pipe or drain pipe mostly. Still need the internal dimensions ideally.

Good call Steve. Balcro or i will calculate the ports for you, or someone else might. It would be helpful to know the size and shape of the ports in the Ashdown cab Using the smaller cab will give you a little less deep bass but a smoother response, to get an idea have a look at the responses that Eminence give here [url="http://www.eminence.com/pdf/Kappalite_3015_cab.pdf"]http://www.eminence.com/pdf/Kappalite_3015_cab.pdf[/url] the Warwick is nearer Emineces biggest box and the Ashdown is halfway between the large and medium box. Personally I'd adapt the Ashdown rather than the Warwick simply because it is the cheaper cab

I use a Hartke kickback 10. Discontinued but I picked mine up for £125. It's not much bigger than a practice amp but also does for practice with a drummer and the odd gig using a bit of DI. Most of my practice is with a Jam mate hipster headphone amp [url="http://www.boomerangsounds.co.uk/product.php/3196/jammate-hipster-ppgm"]http://www.boomerangsounds.co.uk/product.php/3196/jammate-hipster-ppgm[/url]

thought I'd posted earlier but it doesn't seem to be here. We're looking to upgrade, we have the Laney 12 and our keyboard player had a Laney 10. they are cheap and reliable but the vocal sound is pretty poor to be honest, hence looking to upgrade. I was looking at the Wharfedale EVP's in a shop in Bristol which are well spec'ed for the price but the sales guy said the Alto's sound better, I didn't have time to check this out but if I do I'll get back to you. Our singer uses a Yamaha Stagepas 300 for her vocal monitor. Sounds good and is very compact and comes with useful mixing facilities (4 mics + 2 line) for the smaller gig. The only problem is the output is limited at 112dB which is struggling if you are very loud . Let us know how you get on

[quote name='skidder652003' timestamp='1347780354' post='1804778'] Thanks guys, have emailed blue aran to change order to standard 3015 Bc comes up with the goods once again! Mr Starr see you on Lemonrock! [/quote] Hi, guess you won't want my old Black Widow then. If you can give us the internal dimensions of the cabs you have and the sizes of the ports then we will calculate the sizes of the new ports for you. The Mag looks to be about 100l and the Warwick 150ish so either will be possibilities. You should end up with a good sounding speaker. Phil.

[quote name='Mr. Foxen' timestamp='1347734083' post='1804497'] You'll likely need a crossover and a midrange for a not dull or weird sound from a 3015LF. The 3015 not LF works pretty well in a Mag 15 cab though. [/quote]Sorry but this is good advice, you'll have a much better sound from the non-LF. The LF is really meant as a PA driver to work with a horn. Change it if you can. At least it's a neo if you have to pay postage,

If you can get hold of the 'loudspeaker design cookbook' there's some interesting data as Vance Dickason actually tries out different stuffings and measures the results. The air pressure is essentially what excites the panels and this is largely unaffected by the stuffing. The idea of the knobbly foam is to prevent reflection of sound from the back panel straight back through the paper cone. absorption is meant to work in the same way as the fibreglass wedges in anechoic chambers. The trouble is to work the wedges need to be as deep as the frequencies that they are meant to absorb and they aren't big enough so they only work at relatively high frequencies, though they do this well enough. The trouble is that 'stuffing a cab' describes at least four different techniques of removing distortions and some have probably insufficient research carried out.

Resonance isn't a necessarily bad thing of course. If you are building a double bass then the resonances of the body are all a critical part of the sound and your design philosophy for an instrument amp could quite reasonably regard the cab as an extension of the instrument and a part of the 'sound'. Many older designs did this though newer ones tend to go for a flat response and use electronics to mimic the 'vintage' sounds as well as offering new timbres to play with. However if you don't deliberately want a resonant cab then you really should avoid the middle, Even a slight displacement (11th fret?) will have the same effect of raising the frequencies an octave but there will just be much less of them. The cabs we are talking about are lightweight rigid cabs here and are meant to be non resonant. Stuffing, in the sense of the polyester/fibreglass fluffy stuff doesn't impact on panel resonance at all, it is meant to affect only the transmission in the air in the cab. There are heavy bitumnent or mineral loaded rubber pads that are designed to damp panelk resonance but I don't think you mean these.

[quote name='Mr. Foxen' timestamp='1346952187' post='1795305'] So the idea point for a brace is the same sort of deal as the idea place for a piano hammer to strike the string, where it doesn't hit any harmonic? [/quote] That's exactly right, which is why the advice to put the brace straight across the middle (given by someone who should know better in another thread) wasn't very clever. You don't damp bass string by putting a finger above the 12 th fret after all.

[quote name='alexclaber' timestamp='1346950984' post='1795292'] I have a suspicion that a thin-wall but heavily braced panel can exhibit high rigidity at lower frequencies, thus giving good lows but the sections between the braces can have a degree of damped flexibility at higher frequencies which can absorb unwanted midrange, especially if those braces are positioned to give each part of each panel a different resonant frequency whose harmonics are an non-coincident as possible with each other panel section. Unfortunately I haven't had a chance to scientifically test this but it makes sense from a mechanical engineering perspective and it certainly sounds good in practice! [/quote] I think I agree with this in part. moving resonances up moves them away from the low frequencies where the highest energy inputs are in the cab so the problem is reduced. Critical positioning of the braces to spread the panel resonances has to help too as you won't have a single resonance dominating as with an undamped panel. Having said that we are much more sensitive to sound in the midranges which adds another layer of complexity. The bit I am less happy with is the transmission of sound. My understanding is that the energy is absorbed by the panel and that some of it is converted into kinetic energy in the panel, some will be transmitted laterally within the panel and some vertical movement of the panel will occur which will drive the air outside the panel. This will be frequency dependent so the net effect is that the panel acts as effectively as a frequency dependent filter. The absorption of sound in the panel will depend upon its composition, some will be turned into heat. Ply is quite a lively material compared with MDF or chipboard and is even used in cheap guitars and cajon fronts for this reason. The laterally transmitted energy will either be reflected if it meets a hard junction or absorbed at a soft junction. I would guess that how panels are fixed to each other and how braces are attached is crucial. It's a pretty complex system. I would guess that nowhere near all these resonances would be heard in a real life situation though. A friend of mine has just been appointed to Land Rover to work on this in their cars, I'll have to bore her on this when she gets back to see what modelling they do.

[quote name='JPJ' timestamp='1346779817' post='1793144'] So if rigidity of the cabinet is the goal, why is nobody using ultra lightweight aluminium honeycomb panels? I can vouch for the rigidity of this stuff and you can get it foam filled so no nasty voids to excite. [/quote] It's been done for hi fi speakers the Celestion SL 600 was the first I knew about. Quite a successful design though I found it a little dry sounding, it had an early metal dome tweeter if my memory is good and it cost an arm and a leg. The thing is that you have to eventually engineer to a budget and you rapidly reach the point of diminishing returns. There's little point in spending an extra £1000 to get the ultimate rigid and light cab when the difference on stage is almost inaudible when compared with the best existing conventional speakers. Give most of us £3000 to spend on guitar amp and cab and the bulk would go on the bass, not many of us would spend £2000 of that on a cab however good.

Hi Alex, I don't think we've swapped ideas before but can i add my bit to your fan club here. I have always loved your articles in BGM, intelligent, honest and stimulating. [quote name='alexclaber' timestamp='1345204768' post='1774928'] Phil, if you maintain (or increase) stiffness through bracing, whilst lowering mass, you raise the resonance of the panels to the point that they are no longer excited by pressure but instead excited by the backwave, and the backwave and the resulting panel emittance can be damped effectively, unlike pressure changes which you don't want to damp (as they excite the port).[/quote] [quote name='alexclaber' timestamp='1345204768' post='1774928']Personally I consider panel resonance in a loudspeaker a horrible thing unless it's being used to cancel unwanted energy - the last thing I'd want is significant acoustic energy radiating from a panel, with particular consideration being given to how it screws up transient response. [/quote] I can't disagree with any of this at a factual level and the little science training I have wouldn't let me want to do it any other way anyway. the sound from any panel is going to be distorted in so many ways. [quote name='alexclaber' timestamp='1345204768' post='1774928'] In the process you also reduce the backwave reflection which exits through the cone. [/quote] I'm not sure this is right though, surely an inelastic reflection conserves energy and is the most efficient way of reflecting the sound back through the cone and setting up standing waves.. (Assuming it is parallel to the baffle) A thin flexible panel would radiate some energy backwards and lose some as heat. The best way of avoiding this would be to have no rear panel as in some transmission line cabs or by using an angled panel behind the cone. I think all I wanted to say to the OP was to give some indication of the weight saving to be gained and what significant changes in sound might occur. Using the current drivers and going for the lightest option 12mm Poplar with some judicious lightweight bracing might save 6kg or thereabouts. Panel resonances would be bound to change upwards as you say and would probably clean up the sound a little but I wouldn't expect there to be a dramatic change in sound.

Anything technical has to be sorted by the bassist is the rule, well just about. We use Yamaha S112's and S118 subs. I used to leave the subs behind because of the size but now I leave the bass stack behind and just use a Hartke kickback for monitoring and let the subs do the work Overall the sound is much better with the bass through the PA and the subs though big enough have a smaller footprint than the stands. The compression driver in the S112's is a gem and the vocal quality is really clean and sharp. As an amp I use a Peavey IPR1600 for its light weight but for years I used a Behringer EP2500 which worked without a hiccup and i keep as backup. We use either a Phonic active mixer with the amps driving the monitors or an ancient Yamaha mixer before this we used a Behringer Xenyx which never let us down but we ran out of channels. The vocalist likes a clean monitor and uses a Yamaha Stagepas 300 for monitors with the rest of the band monitoring through some cheap PA speakers. They are the next upgrade I think. Mic's are mainly SM58's but I want to move to AKG's as the none I use sounds so much better than the Shures. I'd really recommend the Yamaha speakers and the IPR1600 Our FOH sound is probably better than most bands I hear especially the vocal sound but we need a little more talent mainly. It really is crap trying to mix from onstage though and my bass playing suffers whilst I try to tweak the balance. It is much better when we have someone mixing from the front.

It's very simple, however cross you are just be factual, If they asked you to hold for an unreasonably long time then just say so. If they delay with someone else then that person is warned by you and they won't be able to do it again. There's no reason to be rude of over the top, one sentence from you will stop them being able to do this in the future and saying nothing means they will do the same again in all probability.

Yep, it is a whizzer cone, they used to be very common in the sixties and seventies and the aim is to increase high frequencies. Speakers used to be much more expensive compared with income and one speaker was expected to cover the full frequency range. They don't have lower mass as one of the respondents says in the above link. The main cone + whizzer obviously weighing more than the cone on its own. Large paper cones flex especially at high frequencies so the middle of the cone may be moving more than the outside. Speaker designers have always exploited this to get a controlled frequency response and the whizzer is a way of trying to get a bit more top end. Other manufacturers do this by adding an aluminium dome to the centre of the speaker or by doping the dust cap with something to make it more rigid. Peavey do this with their Black Widows for bass guitar.

[quote name='stefBclef' timestamp='1345491629' post='1778177'] Well I just bought a Peavey 410 and a Peavey 115 TVX so I think I probably have enough heavy Peavey gear for now! But out of interest, how much is your mate looking for and where are they based? [/quote] He lives just outside Reading, I've no idea how much he wants though only that he sold it on ebay but the buyer didn't turn up. I'll ask though.

If you are interested I have a mate with a Peavey 2x15 which he is trying to sell. I used to use it with the MkIII and it sounded great. Didn't enjoy gigs up a flight of stairs too much though.

Stevie's comment got me thinking, I'm an old fashioned boy and my cabs tend to be made of 18mm birch ply or even high density Chipboard, a much underrated material for cabs. The sound transmitted by the panels of a cab is moderately difficult to predict but will depend upon the mass of the panel, the flexibility, the dimensions and any damping. In the end a high mass will have a lower resonance and move less for the same applied energy so a 3/4" panel will 'sound' less than a 1/2" panel. (I said I was old fashioned) Birch ply has a density of about 690kg/m3 and Poplar about 520kg/m3. If you drop from 18mm to 15mm with birch ply and your cab has about 2m2 of board in it you'll save about 4.2kg if you go as low as 12mm then it will be 8.3kg. Swapping birch ply for poplar (18mm) will save you 3.4kg I haven't checked the Young's modulus for the various plys (Basically how bendy they are) so I don't know which timber will be more resonant. I might look that up too. Using thinner panels would mean you need to add some bracing and this would add more weight to the cab so in practice you wouldn't get the full weight saving unless you were happy to live with a more resonant cab. Cab resonance isn't always a bad thing however; it all adds to the 'sound' of your cab which will change subtly with the use of different panel materials and damping. I think the character of the Hartke drivers would still be strongly evident though.

The problem is that class AB amps produce a fair bit of waste heat and heat causes breakdown of transistors. I used to build amps and a 200W amp needed a 150x100mm heatsink with finned fins to dissipate the heat anything beyond this was pretty difficult to dissipate efficiently. As bass amps have become more powerful passive heatsinking becomes impractical. Class D is more efficient and so produces less waste heat. Combine this with a switch mode power supply and the heat produced inside the amp is much lower. The designer of the Peavey IPR 1600 claims his amp will run without a fan [url="http://www.avsforum.com/t/1150665/peavey-ipr-class-d-amps/420"]http://www.avsforum.com/t/1150665/peavey-ipr-class-d-amps/420[/url] but it is included because the public wouldn't have confidence in the amp without a fan. If he is right we may see a return to passive heatsinking. Perhaps you should use a 100W amp or less for practice at home.

Hi Dave, I used to build this sort of thing and still have some of my old power amps but it doesn't make sense economically any more. You could buy a 100W RMS a side amp for around the £100 mark which is cheaper than the components. For £224 you could buy the Thomann t-amp which is 4x500W to run FOH and the monitors or tops and bass bins with a crossover. Again you can buy a ready made electronic crossover for less than £100. It bugs me to say it but the days of home building to save money are gone except for building high end speaker cabs. If you are home building for fun then go for it, of course.

The truth is that many of the current crop of power amps are fantastic value for money. I ran a Behringer EP1500 for years without a hiccup and then an EP2500 which i still use. the only problem is the weight, but that is inevitable if you have a conventional power supply and want it to meet it's specs. I have a Peavey IPR1600 which I now use all the time simply because of the weight, There is very little difference in sound between these amps and none the Peavey speakers will reveal. The thomann t-amps are well regarded and after sales if anything goes wrong will be better than Behringer's.