Bill Fitzmaurice

[quote name='Magic Matt' timestamp='1410126455' post='2546474'] Ok, so I downloaded WinISD Pro and tried to put the parameters in direct from the spec sheet.... same as I had in WinISD... [url="http://www.eminence.com/pdf/Basslite_C2515.pdf"]http://www.eminence....slite_C2515.pdf[/url] This happens... ...oh. Bugger. Now I don't know what to do. [/quote]That's because WinISD is more accurate in the spec calculation than Eminence, going to more decimal places. Only put in as many specs as required, let WinISD calculate the rest. That means Qes,Qms,Vas, Fs, Re, Le, Sd, Xmax and Pe. As for eliminating the hump, you do that by using the correct size cab. Since you're undersizing the box you'll have to live with the hump.

Why tune so low? Maximum output demands, even for a low F# six string, lie between 40 and 70Hz, so you should be looking at the maximum SPL chart to find the tuning that gives the best result in that range. Tuning lower than 40Hz robs you of maximum output in the 40-70Hz bandwidth, and it makes the cab larger than it needs to be. If you have a 4 string you should be tuning even higher, 45-50Hz.

[quote name='Magic Matt' timestamp='1410084748' post='2545885'] It'll be a simple box, rectangular bass port, 130 litre, tuned to 25Hz Recommendations please? [/quote]How did you arrive at that? The C2515 models to the flattest possible response in 412L tuned to 33Hz. That's silly large, of course, but points out why one should think thrice about using the C2515. It can work in 130L, but you wouldn't tune it at 25Hz. 40Hz is the lowest you'd want to go. 25Hz would make the port unmanageably long, and would cause a serious loss of maximum output, while there's no benefit to be gained from tuning that low.

[quote name='bonzodog' timestamp='1409911065' post='2544474'] Very glad I started this thread as there is clearly difference of opinion which I find interesting. [/quote]Well, there's science and there's speculation. Science will win that battle every time.

[quote name='Marky L' timestamp='1409836488' post='2543796'] I currently run ..a 2x10 cab ...rated at 8ohms. I fancy adding a 4x10 8ohm to the 2X10. I can't see what probs I would have. [/quote]The drivers in the 210 would see twice the power as those in the 410, making the excursion capability of the 210 drivers the weak link in the chain. Looking at it from another perspective, what you'd be able to get out of the system wouldn't be all that much different than what you would get out of a matched pair of 8 ohm 210s. The additional output capability of the 410 wouldn't be of much use with the 210 holding it back.

[quote name='mart3442' timestamp='1406894967' post='2515679'] I'll tell that to my friend with the fried amp...... [/quote]His amp may be fried, but it had nothing to do with the lack of the speaker. When in standby mode there is no current flowing to the tube plates. That's why no sound comes from the amp when in standby. If there's no current there's no potential for damage. He might as well have claimed that he blew the engine in his car by pressing the gas pedal to the floor...whilst the ignition was off.

[quote name='spacey' timestamp='1409599335' post='2541410'] The trouble is a lot of of 2x10 are 4ohm and end up doing the lions share of the work if the 4x10 is 8ohm [/quote]That's because of the manufacturers conceding to the "I want to get all the watts out of my amp" syndrome. A 16 ohm 2x10 would be best, allowing you to use up to four of them if you wish, or to pair one or even two of them with an 8 ohm 4x10. But even though it would be the dodgy amp that couldn't drive a 16 ohm 2x10 to full output no manufacturer is going to produce them, because the average player doesn't know that, and would never buy a 16 ohm cab.

[quote name='budget bassist' timestamp='1409581179' post='2541105'] if I end up with something that sounds similar to my Ashdown kit [/quote]Setting your sights way too low you are. DIY isn't about equalling off the shelf, it's about kicking the snot out of off the shelf.

[quote name='budget bassist' timestamp='1409576681' post='2541035'] If what you're saying is true, then surely I can't do much worse than an ill-considered mass-manufactured box would be? [/quote]True, but what most newbies set out to do is to basically build the equivalent of an ill considered mass manufactured box, with the intent of doing so at a lower cost. In the end they don't save any money, while mass manufactured boxes aren't worthy of emulation. For that matter I can count on the fingers of one hand the number of boutique manufacturers whose cabs that I'd consider owning, and one of those I did the design work for.

[quote name='budget bassist' timestamp='1409524872' post='2540616'] But how are all the manufacturers using such tiny enclosures and still getting a good sound? [/quote]They aren't. One doesn't have to go to the full optimal size for a driver, but one also should be judicious in how small one goes, as it does affect the result. OTOH most manufacturers aren't concerned with getting the best possible result, they're interested in sales. Average customers don't know anything about Hoffman's Iron Law, and think f3 is a note, not a marker of speaker performance. What they've been led to believe is that one gets the best results from stuffing as many drivers as possible into the smallest box, so that's what said manufacturers give them. Since these customers have never used a truly well designed and built cab they don't know the difference, so the cycle remains unbroken. [quote]half the satisfaction will come from having designed the thing myself! [/quote]One might say the same about a hang glider. Making an error with a speaker may not have as disastrous a potential result, but still you are asking questions that one fully prepared to design their own speaker would not be asking. If you're bound and determined to reinvent the wheel, and repeat the same errors made by all those who came before, you should at least avail yourself of resources such as this: http://techtalk.parts-express.com/showthread.php?219617-The-Speaker-Building-Bible

[quote name='bonzodog' timestamp='1409476765' post='2539951'] However i neither have the room in the house or car for another 410 so was thinking of getting a 210TP as its smaller and thommann still sell them cheap. However I am sure i have read on another thread here that this is not an ideal set up due to the fact you are sending the same power from the amp into each speaker but one is half the size of the other even though the ohms are correct. [/quote]That's correct. For each driver to receive the same signal the impedance of the 210 must be twice that of the 410. The problem is that most manufacturers don't make them that way. If the 210 and 410 have the same impedance then the 210s capacity will determine your maximum clean output. [quote]May look for a used 210XL then as they are 200W rather than a 210TP [/quote] Watts are moot. What matters is driver excursion, and you have no way of knowing what that is. The only way to get a perfect match is to use identical drivers with the 210 twice the impedance of the 410.

[quote name='TheDaivisch' timestamp='1409388214' post='2539183'] P.s. 18 inch Peavey mated to a 30 watt Marshall guitar speaker it is then. [/quote]So long as a crossover is employed that's a much better combination than a twelve and fifteen, though an eight or ten inch guitar driver would have better dispersion. I know you were being facetious, but I'm not.

Tube tone doesn't just come from the pre-amp, it also comes from the power tubes and the output transformer, so a tube pre on its own won't give tube tone. A great deal of what contributes to tube tone is compression, so to emulate it you should have a compressor in your signal chain, preferably not a 'one-knob wonder'.

[quote name='chris_b' timestamp='1409144865' post='2536779'] If the cones are moving as much as you say... [/quote]That's usually an indication that the driver is not spec matched to the cab, something which has been totally overlooked so far in recommendations.

[quote name='Chienmortbb' timestamp='1408570103' post='2531524'] Just wondering about the benefits of a cast aluminium basket. Fane make a good looking 10" Sovereign 10-300 and a virtually identical Sovereign Pro 10-300 and virtually the only difference is that the slightly more expensive Pro has an aluminium basket rather than pressed steel. [/quote]Aluminum is stiffer than steel, so it's usually used with heavier magnet structures that might cause a steel frame to warp. Aluminum is also used with higher power neo magnet drivers for its heat sinking properties, as neo is more sensitive to heat damage than ceramic magnets.

[quote name='lefrash' timestamp='1409078467' post='2536138'] I had a cab that was wired up at 16ohm. I then rewired it to 4ohm. The difference in volume was massive, when everything else was the same. [/quote]6dB, to be exact. That's at small signal levels. The difference between 4 and 8 would be 3dB, also at small signal levels. At the full displacement limited power capability of the drivers there won't be any difference, because it's driver cone excursion that limits how loud they can go. So long as you have enough power to push the drivers to full excursion you won't get any benefit from a lower impedance load. As to how much power it takes to push drivers to full excursion, on average only 40% of their thermal rating. In short, a low impedance load is only beneficial if you have an amp that's seriously anemic.

[quote name='aj5string' timestamp='1409063104' post='2535924'] Head gives 250w into 8ohms and 500w into 4ohms. Will it actually much quieter in practice running at 8ohms instead of 4?[/quote]No. The primary factors in how loud a cab will go is frequency response, sensitivity and driver displacement. Power and impedance are only minor players in the overall equation result.

[quote name='weepaul' timestamp='1408889725' post='2534334'] Would there be any issues with the cab ? [/quote]Not as long as you don't crank it to the point of high distortion.

Definition minimum: The [i]lowest[/i] acceptable value. 8 is higher than 4, so no worries.

[quote name='Chienmortbb' timestamp='1408779601' post='2533353'] In my experience it is the same in the UK Bill. [/quote]I'd imagine you mainly have PA in the inner cities where it's a big enough hassle even bringing in amps in your car, let alone a lorry full of PA.

[quote name='Phil Starr' timestamp='1408717314' post='2532911'] Sorry to spoil the party but dispersion isn't the only factor affected by cone diameter. First of all you can't vary cone size without changing either its mass or cone thickness both of which will alter the sound it produces. [/quote]If you look at the Mms specs for various drivers you'll see that they have little to no relationship to driver size. For instance, the LAB 12 is 146g, the Sigma Pro 18 is 130g. By the same token Fs and cone size are far from directly related.

[quote name='HowieBass' timestamp='1408650030' post='2532285'] I always wondered about the reason for the vertical stacking of speaker cabs you see at big gigs, now I know (I think)... [/quote]Read this (and the subsequent chapters). http://www.gtaust.com/filter/05/07.shtml

[quote name='chrismuzz' timestamp='1408646062' post='2532224'] Really? We're very lucky over here! In my current band I've only ever done like three gigs where I wasn't through the PA.[/quote]In the US it's SOP that the band provides the PA. The worse the job pays the more likely that you have to provide the sound. Since most bands don't want to pay for or carry any more gear than they have to the average PA is a powered mixer and a couple of cheap boxes on sticks, hardly something you'd run your bass through. The same applies to sound engineers, if you want one you'd better bring one with you. Consequently most bands mix from the stage. Maybe one in ten venues has PA, and those are mainly larger clubs in major metropolitan areas. Outside of cities you'll be lucky to find one in a hundred clubs that has PA.

[quote name='Painy' timestamp='1408642779' post='2532187'] So out of interest, what effect is made to the dispersion in cabs where you have 2 drivers but positioned across the diagonal rather than immediately side by side or one above the other? [/quote]The overall width of the radiating planne determines the angle of horizontal dispersion. If a diagonal placement reduces that width compared to side by side it's better, but it still won't be as narrow as vertical drivers. [quote]Dispersion be damned; there's a PA for that..! [/quote]On this side of the pond I doubt that one in ten bass players is in the PA.

[quote name='chrismuzz' timestamp='1408626296' post='2531952'] This might be a ridiculous question, but if you filled a cab with like 32 tweeters would you get good low end response with better dispersion on the highs? [/quote]No, because tweeters are made with specs optimized for the band width that they operate in. You can get a very good result with a large grouping of smaller drivers which do have specs appropriate for electric bass. But they must not be placed side by side, or the dispersion angle shrinks back to that of a single driver of the same width. The right way to do so is to have them in a single vertical line. For that matter that's how a 4x10 should be made, but they aren't, because what sells cabs isn't technology, it's how they look. [quote]I sort of thought that would be because the 10" cone can react quicker.[/quote]All drivers 'react' with the exact same 'qiuckness', as that 'quickness' is determined by the speed at which an electron wave passes through the voice coil, about 0.7 times the speed of light. What does tend to be different with smaller drivers is their transient response, which is related to the inertial forces of the moving mass. But as you can find somes tens with higher moving mass than some eighteens here again you can't judge the end result by size alone. Your wife/girfriend will give you confirmation on that.