alexclaber

[quote name='bassjamm' post='220901' date='Jun 17 2008, 08:02 PM']So in reality, the only way to know whether a cab can handle your amp, bass...and technique, is to try it![/quote] Basically yes! Though on the limited production run I'm commencing of my own designs I've analysed the designs to the extent that I'll be quite happy to supply detailed specs on response and power handling. [quote name='bassjamm' post='220901' date='Jun 17 2008, 08:02 PM']I'm using a an SVT all valve head and i've had that 'farting' sound from my cabs, dispite them being rated 500 watts at 8 ohms, i've had it when i've used them together and seperately...and my amp is 300 watts at 4 ohms...valves though!!! I've just had the pre-amp valves replaced though, so i'm guessing that could also have been cause for 'farting' noises. I pushed the low end and the valves were knackerd, so maybe they distorted, not the speakers?[/quote] Hmmm... It could be your amp, it could be your cabs. The thing about valve amps is that they don't have any more truly clean power than equally powered solidstate amps. But they do sound nice when you push them into clipping, giving you soft compression, then overdrive and eventually limiting when they're really maxed out, by which point they're making a hell of a distorted monster roar. But if you're a player who expects a clean dynamic sound and is playing at the kind of volume where the amp is generally running clean, as soon as you hit a loud low note then bam! you get a sudden dose of farty overdrive. I suspect that may be your problem, especially if it's still happening with both cabs running, which combined one would hope could handle the Ampeg's peak power in the low frequencies. Alex

[quote name='bassjamm' post='220857' date='Jun 17 2008, 07:15 PM']...all i've ever known about is watts, and i think i'd speak for many by saying that's what most people go by. If it's more to do with sensitivity then perhaps that what should be pointed out...i don't know.[/quote] Let me put it another way - amps produce watts, speakers produce sound. Speakers can generally handle far more than their rated power in the midrange but less than their rated power in the lows - fortunately they make quite obvious nasty farting noises of complaint if you push them too hard, long before any damage is done. Just to clarify matters, speakers contain a coil of wire, like that on an electric bar heater or in a toaster, that can handle a certain amount of power before overheating. That is the thermal power handling limit. Fortunately music goes up and down in volume, has rests, has gaps between notes, etc and therefore it is effectively impossible to get any amp to constantly produce anywhere near full power for more than a brief moment. Thus the coil of wire has time to cool down before it's hit with another brief burst of full power. If using no compression or distortion you could very safely drive a 100W speaker with a 1000W amp turned up to clipping on the loudest notes without risk of thermal damage. You cannot usually hear this thermal damage approaching but fortunately it is very rare on bass guitar woofers. The other issue I referred to is one of how far back and forth the speaker can move without distortion and then damage. To produce low E with the same tone and at the same volume as the E an octave higher, your speaker has to move four times as far. Unfortunately because it is expensive to make a speaker that is capable of moving that far, and it usually means the speaker won't be as loud as one with shorter travel. The reality is that if you try to put more than about 300W in the lows into a 4x10" rated at 1000W the speakers will move so far they will distort. If you put even more power into the lows you will either damage the speaker suspension or the voice coil will jump out of the magnetic gap or hit the backplate. This is what happens when you exceed the mechanical or excursion power handling limit. With unEQ'd bass guitar you're usually fairly safe running quite a lot of power into a cab but as soon as you start boosting lows or getting too aggressive on the lowest notes of a 5-string then that nasty farting noise rears its head. With a load of bass boost you could cause nasty damage to a 1000W rated 4x10" with only a 500W amp. Fortunately the sound of the mechanical damage limit approaching is that obvious farting noise. If it were down to me, manufacturers would not quote any power ratings for speakers due to their general irrelevance. A better route would be to recommend how much (solidstate - valve is a different kettle of fish) power is needed as minimum for gigging and as a maximum for safe use without worrying too much about damage, so for instance I would say that my old Acme Low-B2s worked well with amps from 200-800W. Alex

I've always liked Miles Davis's approach to composition and arrangement, of getting the right musicians and giving relatively vague directions for much of the piece ("shut up and play m*****f*****" I imagine) and only writing out or clearly directing the essential parts. Often I'll leave the precise chords up to the guitarist which can end up in all sorts of nice twists on what I've written and only if it's moving in the wrong direction are clearer instructions required. This makes it a lot less painful when you do have be dictatorial and say "this horribly complicated unison line is what we're playing, we need to nail it note for note..." Looking back at the original post I now realise that technically my bandmates are thus co-writers, which I believe is very useful in keeping a financially ineffective project together, but unfortunately makes this post redundant! Sting. Jaco. There, that's more like it. And although Bob Marley wrote the songs, most of the arrangements and many of the key riffs were originated by (but uncredited to) Family Man. Alex

If it sounds good then it is good. But do you have the time to stand in every location vs the cab and in every different acoustic space you could be playing, to test that it remains consistently good? "What is good and what is not good, need we ask anyone to tell us these things?" Alex

[quote name='Mr Cougar' post='220258' date='Jun 16 2008, 10:18 PM']is the wattage being fed into the cab uniform regardless of the volume.[/quote] When you play a loud note the wattage is high, when you play a quiet note the wattage is low, when you 'play' a rest the wattage is zero. The gain and volume knobs simply act as a multiplier of the power your bass is putting into the amp. Therefore a heavy-handed player with a bass with hot pickups will put out much more power at the same volume knob settings as a lighter-touch player with a bass with quieter pickups. And obviously even at full power the only time your amp is putting out full power is shortly after you strike the string, thereafter the note is decaying and the power is diminishing. Alex

Had an awesome gig last night at The Joogleberry in Brighton - great vibe in the room, support act were cool and we managed to bring a good audience! Played two half hour sets, all originals. Photos: [url="http://www.facebook.com/album.php?aid=39387&id=13382252282"]http://www.facebook.com/album.php?aid=3938...;id=13382252282[/url] (Yes, we are a motley crew...) Alex

Action shots! [url="http://www.facebook.com/album.php?aid=39387&id=13382252282"]http://www.facebook.com/album.php?aid=3938...;id=13382252282[/url] Alex

Played a gig with this one-off 3015 cab last night. Remarkably clean, clear, punchy sound and goes loud. My amp hit the limiters a few times and the cab didn't even flinch, no signs of distortion or farting with 550W hitting it. No extraneous rattles and it is SO light, really need to get it on some scales for a definitive answer. Alex

I'm sure it's a great amp for the money and doubtless it will outlast all of us! Alex

[quote name='bottomfeed' post='219864' date='Jun 16 2008, 02:19 PM']The Bergs are ported at the back, which also makes a difference.... where I put 'em on stage, closeness to walls etc...[/quote] It doesn't matter where the porting is, or even if they don't have any porting at all, the positioning on stage and closeness to walls will always make a difference. Output in the lows from both the speaker and the ports is omnidirectional. Alex

[quote name='chardbass' post='219769' date='Jun 16 2008, 12:13 PM']You need to admit that phrases such as "thermally limited power handling" and "excursion limited power handling" aren't used in everyday musician-spiel before coming over as a shade patronising [/quote] I would come across as less patronising if more people bothered to actually think what is going on with amplification rather than just obsessing over headline figures of watts, watts, watts! How am I supposed to know what is not understood if all the response I get is "And when translated into English that means...?" If I can be bothered to put the effort into trying to explain what all this means, then I expect a similar effort to be returned into trying to understand my explanation, which involves asking for clarification in an intelligent way instead of the far cooler but utterly useless "what is that boffin talking about, I'm just a bass player". I shall now wait for bassjamm to rephrase his inane request for translation into something constructive to which I can respond in a useful manner... Alex

So today I have filled all the screw holes, tested the port tuning, glued the port in, fitted the Speakon, glued in all the insulation, done some of the sanding, fitted the grill, sussed out the balance and thus fitted the handles, and given it a whirl. Sounding good, no extraneous noises. I wish I had some scales here because it is insanely light! Am gigging it tomorrow and will report back duely. Then will do the final sanding, painting and carpeting (this is a one off cab for Mr Russ, which matches the dimensions of his Markbass 2x10", and uses a 3015 woofer). Then onto building the first of The Compact cabs. I'm pleased to say that I've sussed out an optional tweeter with two different crossovers (quite cunning ones!) which should work well on both cabs, which gives a line-up thus: The Compact (15" standalone with tight bottom, strong mids and decent highs, <35lbs, 25"x19"x13.5") The Bright Compact (As The Compact plus tweeter) The Big One (15"+6.5" with deep bottom, very clear and punchy mids and good highs, <45lbs, 29"x20.5"x16") The Big Bright One (as The Big One plus tweeter) The Big Deep One (as The Big One minus midrange to add bottom to a rig or for reggae/dub players) Alex

Clearly a man of excellent taste! I continue to be blown away by my RIM Custom 5 and am almost certain it'll still be my main bass come the middle of the century! Alex

[quote name='wateroftyne' post='218813' date='Jun 14 2008, 01:10 PM']I'm being such an anorak about all this. I've put the specs of loads of cabs in a spreadsheet for easy cross-referencing.[/quote] It's a shame that the vast majority of these specs are fictitious, extremely optimistic or carefully incomplete, otherwise that would be a useful document. Whatever you do, don't let the makers' creative writing skills affect your final decision! Alex

[quote name='bassjamm' post='219014' date='Jun 14 2008, 10:26 PM']And when translated into English that means...?[/quote] Just re-reading my post and can't see what's so complicated about it! Could you clarify what you don't understand? Power handling specs are about as useful on bass cabs as are top speed ones on sportcars if you live in London - you will never be able to sustain enough power into the cab to overheat the speakers, just as you will never find a long enough bit of road in the city to reach anywhere near top speed. What matters is how well your speakers will handle excursion (hopefully you've noticed that speakers move backwards and forward to create sound), just as it matters far more how fast your sportscar can take a speedhump wihtout breaking the suspension or bottoming out (if you want to get round London fast, that is). Unfortunately neither cab makers nor car makers respectively tell you this data. Alex P.S. I love you too Robbie, you've made me the best bass ever! x P.P.S. For the money the Dr Bass 2460 totally whips the Whappo Jr on every respect except low frequency extension - and as you say, you can always just turn up the lows and then they're level on that front too.

Bracing! Alex

I remain very impressed by my QSC PLX. Not sure on UK prices as I bought mine used in the US and had it serviced and converted to UK voltage by the factory but they're not hugely expensive for the weight and power. Also the Crown XTi amps are getting very favourable reviews for the price and the onboard DSP is a nice feature. If you limit yourself to 1U amps the choice is much more restricted and often they require a deeper rackcase than a 2U model. Alex

[quote name='bassjamm' post='218051' date='Jun 13 2008, 12:54 AM']I think it's more a question of power though...200 watts @ 4 ohms. I think that's quite poor![/quote] But does it matter? I doubt it. The limiting factor in power handling for bass cabs is not the thermally limited power handling but the excursion limited power handling. That 200W number is the thermally limited power handling. Unfortunately no manufacturers quote the excursion limited power handling but rest assured that it is FAR less than the thermally limited figure (Acme are a unique exception to this). For a 1000W rated neo 4x10" you're probably looking at 300W excursion limited and for a 500W rated neo 2x12" you're looking at 225W excursion limited. All that 500-1000W figure does is sell cabs, it doesn't actually make any difference in the real world. Factor in the high sensitivity of this 2x12" design and the power handling becomes even less relevant. Alex

If you think of the amp as just a voltage amplifer then it makes more sense. Then treat the speaker as a simple resistor. Power = Volts x Amps Amps = Volts / Resistance So: Power = (Volts x Volts) / Resistance So for a 300W into 4 ohm amp: 300 = (V x V) / 4 V = SQRT (300 x 4) V = 35 Volts Then into an 8 ohm load: Power = (35 x 35) / 8 = 150 Watts And into a 16 ohm load: Power = (35 x 35) / 16 = 75 Watts One more thing to bear in mind is that earlier on we stated that Amps = Volts / Resistance. So the lower the resistance, the more amps the amplifier has to supply for every volt it puts out. Unfortunately the power supply in most amplifiers cannot keep consistently increasing the amps as resistance decreases, so you end up getting less than double the power every time you halve the resistance. That's the simplistic view. The real view takes into account that we're dealing with impedance which varies hugely with frequency instead of being a constant 4 or 8 ohms and also because the speaker is a reactive load the volts and amps are rarely in phase which mean the amplifier needs more current capability than you'd expect. So to recap - your amp is simply a voltage amplifer and it does not 'know' what impedance your cab is but it will simply try to supply the current that is required to match the above equation. If it is asked for too much current then it will shut down or die - that's where the minimum impedance comes into it. Valves amps are totally different because they use impedance matching output transformers. Alex

[quote name='ste_m3' post='216749' date='Jun 11 2008, 11:59 AM']Pictures...? [/quote] Good point, shall take some this evening! [quote name='david_l_perry' post='216837' date='Jun 11 2008, 01:24 PM']Have you tried out the cab using an active crossover/bi amped to see how it sounds first, or are you just making the leap of faith...[/quote] Neither! If I can get the cab to plot out pretty flat then I'm very confident that it will sound how I want. I've just done another redesign of the crossover (this is the 6th iteration for this driver combo) and this time I've got the component count down to six with my best response yet - the big challenge is getting the woofer and mid to cross over low enough without having too shallow a slope to protect the mid. The way it's working is that the cap and coil values are such that they actually compensate for the impedance variations to a good degree and I'm just using a small amount of impedance compensation on the mid. By avoiding impedance compensation on the woofer I'm getting greater sensitivity and avoiding adding tens of pounds to the component cost and lbs to the weight. Have also had some thoughts about the build process and thus need to order a large pile of clamps! Alex

Currently in the process of getting a one-off 15" cab completed and also working on perfecting the crossover on the 15"+6.5". I can now say with certainty why most cabs don't take this woofer+mid with true crossover approach - it is a nightmare to get it working without a crazy amount of components - current count stands at eleven and that's assuming I can get caps, resistors and coils in the exact values I want! Alex

And here we have a great example of the thinking of someone that is so convinced his thinking is correct that he is failing to think at all! "Now as a standard bass has four strings and is tuned to a fourth through the strings from E, the gauges or weight between strings should not change. I personaly have about ..20 between strings from .120 on an E to ..60 on my G flatwound." Oh dear... Alex

I'd be happy to go without backline if using really good monitors. But until the venues I play start including big Meyer sidefills and the like then I'd rather have a bass amp onstage. Even though stage monitors don't need to produce a lot of bottom because of the bleed from the main subs, they do need to be able to handle the dynamics of a bass guitar without nasty distortion and few I've heard can. Alex

[quote name='david_l_perry' post='212805' date='Jun 4 2008, 10:20 PM']So Alex, have you changed the cab design or just the crossover ?[/quote] I've changed the port shape - from triangle to slot - and the mid enclosure to a simple cuboid (bit more output from both woofer and mid due to the gain in woofer enclosure volume and loss in mid enclosure volume). And different handles, grill, corners. And I've designed a simple 1x15" which will represent half the cabs I'm building. Alex

So many rectangles of plywood! Now to work out which are which and start drilling pilot holes... Alex