Bill Fitzmaurice

[quote name='fuzzonaut' timestamp='1376680302' post='2178056'] just stumbled across an odd looking cab, it's a 3x15", and the owner claims it's good for guitar [b]or[/b] bass, which I thought can't be the case.. [/quote]Judging by the small dust covers those drivers may be generic musical instrument drivers from the late 60s or early 70s, which were used for both guitar and bass. By modern standards they wouldn't work very well.

Found my schematic, it uses the Alto PM12 Dragonfly power amp module. The input chip is a TDA8929.

[quote name='BassBunny' timestamp='1376501908' post='2175073'] There is also Alto the Italian PA company. they are distributed/repaired by Proel. [/quote]+1. Nearly everything in the Superfly was sourced there. Some of the boards have the Alto name on them, probably shared by Alto branded gear.

[quote name='apl4' timestamp='1376471815' post='2174266'] Does anyone know where I could get a replacement board? [/quote]Try Alto, that's who made them. Once upon a time you could download the schematic from Ashdown, but that was when they were in production and you probably didn't need it, as opposed to now, when you do need it.

[quote name='Ashdown Engineering' timestamp='1376076703' post='2169560'] The published specs are 100% correct(yes the specs are huge)and we are happy for anyone to test and check. We don't overinflate specs like some other manufacturers out there might.. ;-) [/quote]The only specs that matter IMO are a measured SPL chart and the driver displacement. Playing Devil's Advocate, the 25Hz - 20kHz at 98.5dB 1m/1w listed for the ABM210 is impossible to realize, unless said response is at least -20dB at 25Hz. The same applies to the claimed combination of low end response versus sensitivity for the 1x15. And 'front-ported for maximum forward dispersion' isn't a claim that came from the engineering department, or I'd surely hope not, as they should be aware that the radiation pattern of port output is omni-directional. I'd say that the marketing department is writing cheques that the engineering department can't cover. I'd like to be able to take you at your word, but I'm afraid the reality of the physics won't allow for it.

[quote name='grenadilla' timestamp='1375385650' post='2160679'] That cabinet with 4 8s is interesting. I have heard of Sica speakers but not an 8 that can handle hundreds of watts. [/quote]Thermal ratings mean next to nothing. Chances are the eight is this: [url="http://www.sicaspeakers.com/speaker/pl8b25s"]http://www.sicaspeak...speaker/pl8b25s[/url] It will only handle 100w before reaching maximum excursion, and the response plot isn't very good. The ten is likely this: [url="http://www.sicaspeakers.com/speaker/pl10b25s"]http://www.sicaspeak...peaker/pl10b25s[/url] and the the fifteen this: [url="http://www.sicaspeakers.com/speaker/pl15b3s"]http://www.sicaspeak...speaker/pl15b3s[/url] and they're OK, but far from stellar. They're no competition for the Eminence drivers that Barefaced uses. They're much better than the cheap Blue Line Ashdown drivers, but that's not a high bar to clear.

[quote name='Mr. Foxen' timestamp='1375888657' post='2167006'] Watt ratings are meaningless, so its all not worth considering. Its a thermal rating, and thermal has nothing to do with sound, or the point where the cab farts out, or where it breaks. [/quote]+1, useful power handling is determined by the driver xmax, and said useful power handling can be as little as 20% of the driver thermal rating. To find out what a driver can really do you need its T/S specs and then use speaker modeling software to model its capability in the cab that its loaded in. That will give you the displacement limited power handling, which in a perfect world all speaker manufacturers would provide, but the world is far from perfect.

[quote name='xgsjx' timestamp='1374493352' post='2149251'] Foam pads on the walls might help reduce the vibrations as well as a floating floor (Gramma pad, small drum riser, etc). [/quote]Foam will absorb midrange and high frequency reflections within the room, but it will do nothing to stop low frequencies passing through walls, ceilings and floors. Gramma pads don't do anything to stop low frequency passage. The only thing that stops low frequencies is mass, a lot of it.

The output voltage of a loop typically runs 1v at 600 to 1000 ohms. That makes it not a good match for floor pedals that expect maybe 100mv with the 25kohm output impedance of a bass.

Fuzz can kill tweeters, octavers can kill woofers. If you must use an octaver, and I would not, you should have the EQ on your amp pulled down below 40Hz, otherwise the drivers can be damaged by over-excursion.

[quote name='alexclaber' timestamp='1371735588' post='2117519'] Biamping is not going to be beneficial with those cabs. The 15" may go lower than the 4x10" but the 4x10" will move more air and so be better at the lows. The 4x10" probably goes higher than the 15" but has worse dispersion through the mids so will be harder to hear around the room. So neither cab is a specialist at either lows, mids or highs. [/quote]+1. One bi-amps when they have two cabs with distinctly different frequency band widths. Mesas, and for that matter virtually all electric bass cabs, don't.

[quote name='Mr. Foxen' timestamp='1371723848' post='2117311'] Trannies for valve amps don't cost any more to have made than ones for SS. Its still iron and wire, [/quote]Ture, but valve amps need an output transformer as well, SS do not. Valves themselves are very expensive as their manufacture is fraught with environmental issues, high labor cost, and very limited usage/demand.

[quote name='MoJo' timestamp='1371677033' post='2116964'] Why are all valve amps so expensive? [/quote]Because the musical instrument industry is the only one that still uses them. Price is inversely proportional to production quantity.

[quote name='Mr. Foxen' timestamp='1371563394' post='2115556'] How do you predict then? Using phase charts? [/quote]That would be part of the method. But you can't even get SPL charts for cabs, let alone phase charts, so even if you knew how to use them to predict the combined response the necessary tools just aren't available.

[quote name='Chris Horton' timestamp='1371410346' post='2113570'] I do run the 410 & 210 together for bigger gigs but when I do , it feels like the 210 cab is struggling compared to the 410 if that makes sence. [/quote]It does, because both are receiving the same power. For them to work well together the impedance of the 410 would have to be half that of the 210.

[quote name='JTUK' timestamp='1371392503' post='2113252'] I've never seen any value in a 15" cab [/quote]To put it in a historical perspective, once upon a time fifteen inch drivers tended to be better suited to low frequency applications, while twelves and tens were better suited for higher frequencies. Until roughly 1975 for the most part there was no such thing as guitar versus bass drivers, there were only musical instrument drivers, most of them designed for guitar. Some fifteens were designed for organ and PA, and worked better with bass than guitar tens and twelves. The original 1969 SVT was loaded with guitar tens, that's why they needed sixteen of them to handle the 300w head. Taken in that context, circa 1950-1975 there was some benefit to mixing cabs. That benefit went away with the introduction of true electric bass tens and twelves.

[quote name='Mr. Foxen' timestamp='1371384013' post='2113139'] Mixing cabs is a bad plan. The reason it is a bad plan is that the sound of the combination is totally unpredictable, so as soon as you plan on mixing the cab with unspecific different cabs, you can't get any useful suggestions, because nobody can know how they will pair up, the sound isn't a combination of the souds of the two, its another sound again. Do you like the sound of the 10s you have but need louder? Get more the same. If you don't like the sound of them, get rid and get somehting you do like the sound of, then add more the same until loud enough. [/quote]+1. In addition, the usual reason given for adding a fifteen is to get lower extension. The fact of the matter is that the average fifteen loaded cab goes no lower than the average ten loaded cab. As for output capability, the average 1x15 has less output capacity than the average 4x10. Advertisements mixing 1x15 and 4x10 are ubiquitous, as is the use of that by many endorsers. Why? Ads are intended to sell product, as is supplying endorsers with what the company wants to sell. As to what companies want to sell, that's highly driven by what you want to buy. If you think that 1x15/4x10 is a good combination no company is going to try to talk you out of it. They'll give you what you want and take your money, thank you. The more you know about how speakers work, the less likely you'll want to mix cabs. As for what endorsers use, don't assume that just because they're great players that they know any more about speakers than you do. Bottom line, they use what they're paid to use.

[quote name='krispn' timestamp='1371274527' post='2111953'] was wondering if I should be looking for a head which can give the cab more oompf at the rated 8ohm. [/quote]That depends on the drivers in the cab. Some top of the line twelves will take 400w before reaching their excursion limit, but most won't. The average twelve with 5mm xmax reaches its maximum low frequency output capability at no more than 150w, no matter what the voice coil thermal rating may be.

[quote name='malcolm.mcintyre' timestamp='1371155047' post='2110714'] I believe they need a lot of amplifier damping, like a big powerful Crown. [/quote]No moreso than any other cab. They were developed by Voigt/Bailey/Bradbury in the days of valves.

[quote name='JTUK' timestamp='1371138010' post='2110387'] That would be a warning sign to me, tbh.... but as for config, I wouldn't go up against a gtr212 with a bass 210. [/quote]+1. With a one octave drop in frequency range power/driver displacement demands quadruple. A 2x12 guitar versus 2x10 bass cab is a severe mismatch, like a heavyweight taking on a lightweight. Care to guess which one will lose? [quote]They mainly do Guitar Cabs so anything about speaker reccomendations are related to guitars[/quote]With guitar you can literally stick a driver into a box and it will work well, with no engineering whatsoever. That's the complete opposite of what's required for a good bass cab.

[quote name='Mr. Foxen' timestamp='1371049855' post='2109134'] With same power, the PS cab is going to be loads quieter, since you are feeding power to two speaker, but only one of them is moving air. Plus its a smaller speaker. [/quote]+1. Output is determined by driver displacement. The OBC115 has 343cc, the SP212 has 255cc. If you want a lot of output from a small package the barefaced Big Baby has 496cc.

[quote name='helmn' timestamp='1370974349' post='2108193'] I am probably going to line rather than stuff the TL [/quote]That's not a choice you can make arbitrarily. You must measure the response and/or the impedance and use as much damping as is required to suppress the harmonics without over damping. If you don't have the required gear to do so there's no way to get it right.

[quote name='Beer of the Bass' timestamp='1370956913' post='2107906'] I've seen it mentioned that some of the existing cabs labelled as transmission lines (like Euphonic Audio) are too short to be true transmission lines and behave more like ported cabs. What does the port stuffing do in these cabs? Subjectively, the cabs "work" but it would be interesting to know what's going on with this design. [/quote]A true 1/4 wavelength long TL is a resonant pipe. The primary resonance at the 1/4 wavelength frequency is beneficial, being added to the driver front wave radiation. There are also higher frequency resonances at the harmonics of the 1/4 wavelength frequency, and those create undesireable response peaks and dips. The line should be stuffed with sufficient damping to remove the harmonic resonances while leaving the fundamental resonance unaffected. As for the EA, its operation would be identified by an impedance sweep, but I've never seen one.

A useful TL would have to be at least 2 meters long, while low Qes/Qts pro-sound drivers don't work well in TLs. All in all they're just not a good alignment for electric bass, as they don't work any better than much smaller and easier to construct bass reflex.

When the guitar player turned up that should have affected both the mains and monitors, so the engineer should have noticed it. You should have just asked him to turn that monitor feed down between songs. Turning up your amp may or may not affect the volume in the PA, depending how the DI works in your amp. Some are pre-master, some are post-master, some are switchable. Your owners manual will say.