Bill Fitzmaurice

[quote name='The fasting showman' timestamp='1457648371' post='3000715'] I've owned a few Bassman 135s and a 100 and I seem to remember from the circuit diagram that the '70s Fenders break from the convention of parallel outputs (tweeds etc) and are wired in series but with a switching jack on one of the outputs [/quote]The 135 may be different, but the standard Fender arrangement used a switched main speaker jack which shorted to ground when there was no plug inserted. This prevented damage that would occur if the amp was used with no load. It also caused consternation if you plugged into the extension jack and not the main jack, as the amp wouldn't work. We didn't know at the time why they did that, but you didn't have to make that mistake very many times before you learned not to do it.

[quote]Does this mean each output is 8 Ohms?. [/quote]It means the transformer tap is rated for 4 ohm operation. Since it's a valve amp you may use a 4 ohm OR LOWER load. For that matter you may use an 8 ohm load, the Fender output transformer and power valve circuitry is very robust. I wouldn't use higher than an 8 ohm load though, while 2 ohms is perfectly OK. Back in the day when we didn't know better we ran Fenders day in,day out with 1 ohm loads with no ill effect. As for the previous replies, they would be accurate if the Bassman was a SS amp, but it isn't.

[quote name='ebenezer' timestamp='1455030634' post='2975194'] I think this is a great idea! you could eq the 15 combo to deal with the lower frequency and eq the 210 for mid and above....a basic bi-amp system if you like and better than just adding a 210 cab!! [/quote]That would make sense if a 1x15 and 2x10 had dissimilar response, but they don't. For what you suggest a 1x10 guitar combo atop the 1x15 combo would work better. For what the OP suggests adding a 1x15 extension cab would be best, and a lot less expensive than a second combo.

[quote name='MoonBassAlpha' timestamp='1456407455' post='2988663'] Presumably the tweeter or horn would take care of the highs and the band pass response might even enable the use of a less complex crossover [/quote]Only if the crossover frequency is low enough. The lower the crossover frequency the more expensive the HF drivers and crossover components. That's probably the main reason why slot loading isn't common.

[quote name='MoonBassAlpha' timestamp='1456389960' post='2988444'] Strange that no one else used the vertical slot if it is a sound idea acoustically [/quote]TOA did. But slot loading comes at a price, that being a reduction in high frequency sensitivity, as the result is a band pass alignment.

[quote name='gapiro' timestamp='1456236672' post='2986882'] I can think of a tiny stupid reason - is it you have a right angled jack for the kettle lead then it is nearer the speaker for all of a few inches...... maybe a tiny bit more 50hz hum? Surely nothing noticable though. [/quote]Speaker leads are immune to hum pickup. You can only get hum pickup on leads which carry signal that's subsequently amplified, like your instrument lead. [quote]I'm intrigued as to why, I can't find anything using the good ol google[/quote]The angle of dispersion is inversely proportional to the size of the radiating plane, as demonstrated by this: [media]http://www.acoustics.salford.ac.uk/feschools/waves/flash/diffractionslider.swf[/media] This specifically shows the effect of a diffraction grate, but the same physics apply both to the size of a driver and what happens when multiple drivers are placed side by side. If you've ever wondered what was the deal with the vertical slot on some old Trace Elliot, now you know.

[quote name='Bigwan' timestamp='1456223958' post='2986704'] I think perhaps that has been copied and pasted from one of the Orange valve amp manuals. I've yet to see a modern solid state (or hybrid) amp that couldn't be run without a load. [/quote]+1. Here's why: With valves signal always passes through the output valves, because their load is the primary winding of the output transformer. If there's no load on the secondary winding of the output transformer bad things can ensue. With SS if there's no load no current passes through the output transistors, so there are no worries. Once upon a time first generation SS amps used output transformers, but I haven't seen that done since the late 1960s.

[quote name='Gottastopbuyinggear' timestamp='1456147751' post='2985840'] From the brief messing I've done with WinISD I'd expect to be able to get 3dB down at around 60-70Hz, and maybe 10dB down in the mid 40s Hz area. Is this a reasonable expectation for what I'd get from a fairly good quality commercial cab, and hence a good target for a DIY build? [/quote]Yes and no. Yes, that's typical of a commercial cab. No, it's not a good target for a DIY cab. Using tens a 50-55Hz f3 and 35-40Hz f10 is a reasonable target, easily achieved. You'd need to go around 40-45L per driver, but the external dimensions will only be a few cm larger than 25-30L per driver, and with properly braced 12mm plywood construction and neo drivers the weight won't be bad. The Deltalite II 2510 is my go-to electric bass ten.

[quote name='chris_b' timestamp='1455756295' post='2982245'] Unfortunately a lot of people around the world didn't get to survive the legacy of that particular idiot. And Americans can be that stupid. They didn't learn anything the first time around and voted him in for a second term. That was unforgivable. [/quote]How long did Tony Blair serve as PM? There's plenty of blame to go around for that cock up.

[quote name='Chienmortbb' timestamp='1455745146' post='2982128'] Don't joke Bill, that is too frightening to joke about. [/quote]I believe that Trump will get the Republican nomination, but that he won't win the election. On the whole Americans aren't that stupid. Besides, it wouldn't be the first time we elected the village idiot, and we've managed to survive it.

[quote name='Merton' timestamp='1455654440' post='2981253'] Horizontal, in a wooden box 6 feet under [/quote]Redundant, he's already brain dead. Think the Prince Regent in [i]Blackadder the Third[/i]. He shows what any moron can accomplish when his daddy leaves him $100 million.

[quote name='fretmeister' timestamp='1455649490' post='2981166'] There's a guy on another forum who claims he can hear the difference in his hifi depending on whether the IEC power cable is straight or curved. [/quote]No doubt. The things some people will believe defies explanation or logic. Donald Trump as President, for instance.

[quote name='fretmeister' timestamp='1455610092' post='2980562'] Vertical is actually better for dispertion in the room. [/quote]+1. Intuition says that horizontal drivers will give wider dispersion, but the opposite is true. Where the behavior of sound waves is concerned intuition is usually wrong. That's why acoustical engineers aren't born, they're made, through education.

It depends on the cab construction. A well braced cab made of 12mm plywood will perform better than a poorly braced cab made of 18mm plywood. Most manufactured cabs are made of 18mm not because it's better, but because it's cheaper. Installing proper bracing increases labor costs. [quote]Possible daft but has anyone seen if you can gain anything from having the cab vibrate somewhat?[/quote]Energy expended vibrating cabinet walls is energy that doesn't get translated into sound output.

Break in only takes a few hours of normal playing.

Not all drivers have the same suspension stiffness.

Without a schematic one can't be sure. Typically you want the output impedance of a line driver to be no more than 1/10 the impedance of the driven input.

[quote name='Yawn_Blah' timestamp='1454049351' post='2965723'] thanks a lot now i have a picture of what's happening. search results too technical for a noob so i need you guys to confirm that i can ask a tech to reduce the output impedance on the pre? [/quote]That's not something you can do with a screwdriver. I don't see an output transformer, so my guess is that it was designed to operate like a pedal into the bass amp input, rather than driving a power amp. One would have to see the specs to be sure, but if it works OK that way it's a safe assumption that's the case.

[quote name='dincz' timestamp='1454011816' post='2965477'] Effects returns are generally lower impedance than instrument inputs. Not a problem for most preamps but maybe yours has a fairly high impedance output. [/quote]+1, it's probably a loading issue related to the output impedance of the pre.

[quote name='gjones' timestamp='1453639478' post='2961246'] Is the DI signal on these amps THAT high, that they need to cut it by 40db? [/quote]That's the difference between mic level and line level. The board should have the ability to switch the XLR inputs between mic and line level, but not all do.

[quote name='JohnFitzgerald' timestamp='1453570380' post='2960685'] Why is it we need amps of several hundred watts or even thousands and, more to the point, why do we need higher SPL from the speaker than that very modest amp will provide? [/quote]If you have proper PA support, you don't. For that matter with proper PA no guitar player needs more than a 50w 1x12 combo. Gear excess in the backline is the #1 complaint of every soundman I've ever talked with, from those in 100 seat clubs to those in 20,000 seat stadiums.

[quote name='Twigman' timestamp='1453335953' post='2958639'] They couldn't....why do Americans use this phrase? - it means the opposite of what they want to say. [/quote]Why do you spell color 'colour'? And it's not a boot, it's a trunk.

It's a lot less work and expense to simply tilt your cab back so you can hear the mids and highs.

[quote name='JapanAxe' timestamp='1453323201' post='2958510'] Also worth considering that a frequency of 19Hz has been found to cause feelings of fear and anxiety. I got this from a TV programme about how natural phenomena give rise to 'supernatural' effects. [/quote]The TV show didn't examine it in depth. Women are genetically pre-disposed to not like low bass effects. In the wild low frequency vibrations tended to be harbingers of nastiness, like earthquakes and stampedes. Men are the opposite, as said stampedes were a sign of lunch approaching on the hoof. This to a great extent explains male fascination with big subwoofers, explosive effects and loud cars and motorcycles, whereas women could care less. What explains the female infatuation with shoes is anyone's guess.

You need not be concerned about the fundamental, only the second harmonic. A speaker with solid 40Hz response will suffice.