Bill Fitzmaurice

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.

[quote name='bassman7755' timestamp='1452886862' post='2954526'] .An in line array of small identical ones is generally the next best thing so long as you only need good dispersion at right angles to the array hence the popularity of vertical arrays for pro sound systems [/quote]What works for PA works just as well for bass. What doesn't work well for either is drivers placed side by side, unless a .5 alignment is used, as in some Barefaced models.

[quote name='peteb' timestamp='1452811815' post='2953827'] As I understand it (and I'm not particularly technical by nature) the efficiency gain is because all of the speakers are moving together, [color=#282828][font=helvetica, arial, sans-serif]doing the same thing at the same time and are therefore all the speakers are perfectly in phase with each other. [/quote]That will be the case with identical speakers placed very close together. If they're not identical phase issues are a given. [/font][/color] [color=#282828][font=helvetica, arial, sans-serif][quote] this may not happen if you were to mix 10s with say 15s, you might expect the 10s to move faster than the 15s and with a shorter excursion. [/font][/color][/quote]All driver cones move at the same speed with the same signal applied. The issue with shorter xmax is that it will be the weak link in the chain. Driver size and xmax aren't directly related. You can find tens with 10mm and fifteens with 1mm. [quote][color=#282828][font=helvetica, arial, sans-serif]I would imagine that if cabs with different speakers are made to be used together they are engineered for the different speakers to have a similar [/font][/color][color=#282828][font=helvetica, arial, sans-serif]excursion (assuming that [/font][/color][color=#282828][font=helvetica, arial, sans-serif]excursion [/font][/color][color=#282828][font=helvetica, arial, sans-serif]is the right word).[/font][/color][/quote]That is one concern, but not the only one.

[quote name='peteb' timestamp='1452785475' post='2953504'] I read something on here once about the advantages of using similar cabs with the same speaker size was that all the speakers would be doing the same thing at the same time and therefore you would get an efficiency gain. [/quote]You almost always get a sensitivity gain. That's why so many users of mixed cabs rave about the combination. But the reality is that virtually [i]any [/i]two cabs together will sound better than either on its own, partly due to the sensitivity gain, partly by the upper cab making it possible to hear your mids, rather than have them all pass you by south of your equator. [quote] I'd need it to be proved the cabs [i]didn't [/i]work together rather than the other way around.[/quote]Going by that criteria one can make a solid case that the sun revolves about the earth. In the immortal words of the late President Reagan, "Trust, but verify". Without peer-reviewable data one cannot verify manufacturer claims, no matter who they are.

[quote name='Conan' timestamp='1452777573' post='2953361'] Ah, but were they[b][i] really[/i][/b] "designed" to work together, or do the manufacturers just tell us that so that we'll buy them? [/quote]+1. I've seen a number of manufacturers make the claim, but the supporting data seems to be kept in the same inaccessible (or mythical?) vault as their SPL, polar response and waterfall charts. IME the only effort that manufacturers make to have their cabs designed to work together is making sure that the stacking corners fit together. [quote]Current cab;[list] [*]Woofer: 2-10” Neodymium Magnet Woofers [*]Tweeter: High Intelligibility CN Series Tweeter [*]Impedance: 8-ohms [*]Power Handling: 400W RMS [*]Crossover: Custom Phase-Coherent Crossover w/ Tweeter Control [*]Frequency Response: 40hZ – 15KhZ [*]Sensitivity: 99db @ 2.83v / 1-meter [/list] Proposed addition;[list] [*]1-12˝ Neo woofer [*]High intelligibility tweeter [*]Power handling: 350 watts [*]Custom phase-coherent crossover w/ tweeter control [*]Precision tuned [*]Frequency response: 40hz-15khz [*]Sensitivity: 98db @ 2.83v /1meter [*]Impedance: 8 ohms [/list] [/quote]I see no benefit in adding the twelve. You don't gain any LF extension. The two tweeters will be physically separated, so they'll fight each other more than they'll assist each other. As for the power issue, the thermal power ratings of the two are meaningless. What matters is the displacement limit, which you don't know. The usual reason given for adding a second dissimilar cab is to improve the overall result. IMO if you're not happy with the tone of the cab you have get a different cab. If you're happy with the tone but it doesn't go loud enough get a second identical cab. Doing anything else is like Mamma Gump's proverbial box of chocolates.

[quote name='machinehead' timestamp='1450973799' post='2937559'] I just can't grasp why some posters seem to be so strongly against gaining a little knowledge of engineering and physics to complement their auditory skills. [/quote]Hubris.

[quote name='wateroftyne' timestamp='1450735618' post='2935421'] I wonder if we've all got a bit caught up in the hunt for the perfect flat response [/quote]Flat response is as interesting as driving across Kansas, which is also flat. It doesn't actually take a week to do it, it just seems that way. I chuckle every time I see someone talking about getting flat response. Given that nothing in the signal chain is flat, starting with the bass itself, if they actually managed to get the final result flat they probably wouldn't like it.

[quote name='bassman7755' timestamp='1450535524' post='2933730'] Good find, the schematic actually shows the transformer rewiring necessary for 240v [/quote]It shows that for the export model, but it probably wouldn't be the export model if it's coming from the US. Considering the age I'd replace the filter cap, and upgrade it to at least 4700uF/100v. It's been a very long time since I've done power supplies, but I do recall that the transformer secondary voltage isn't the same as the voltage once rectified and filtered, so it will take some research to find out the required secondary voltage.

With an amp that old chances are the primary is 110v only. You'll need a schematic to determine the requirements to swap in a 220v primary.

[quote name='No lust in Jazz' timestamp='1450348935' post='2931839'] I'm still struggling with the definition of 'boutique' - [/quote]Technically, brands not sold by mass marketers, such as Guitar Center in the States, or Thomann in Europe.

[quote name='Chienmortbb' timestamp='1450122073' post='2929846'] I honestly think it was the look of them that put people off. [/quote]No doubt. If they'd hidden the baffle behind grille cloth people would have been far more concerned with how they sounded than how they looked.

It's called, oddly enough, slot loading. The narrow slot widens dispersion, using the principles of diffraction: http://www.acoustics.salford.ac.uk/feschools/waves/flash/diffractionslider.swf It also adds a bit of acoustic loading to improve lows, but there being no such thing as a free lunch it also costs some high end, as it also works as an acoustic low-pass filter.

[quote name='Tdw' timestamp='1449689058' post='2926034'] i think the "throw" is mainly due to...[/quote]There's no such thing as throw, at least not where bass cabs are concerned. All lose volume at the same rate, 6dB per doubling of distance when room reflections are not present. Variations in that rate are due to room reflections, not the speaker. Line sources behave differently, but we don't use line sources for bass. A vertical stack of tens or twelves will have some line source properties, but only in the upper midrange.

[quote name='PaulWarning' timestamp='1449676017' post='2925878'] the loudest frequency the speaker gives out will be lower in a 15" speaker[/quote]-1. [quote] or of course, I could be talking a load of bollocks[/quote]+1.

[quote name='Chienmortbb' timestamp='1449667418' post='2925747'] If you stack side by side as if it were a 4x10, you will lose more low frequencies further from the stage. if you stack so the drivers are one above the other, they will project the lows further. [/quote]Vertical versus side by side placement affects midrange and high frequency dispersion, but it has no effect in the lows. [quote]must admit I don't get this speaker size doesn't effect depth argument [/quote]There are over a dozen T/S specs that determine low frequency performance. Cone size (Sd) is only one of them, and by no means is it the most significant. The most significant is free-air resonance (Fs). If you look at driver data sheets you'll find that there is only a cursory relationship between Sd and Fs. Examples of some tens with lower Fs than some eighteens abound.

If you're going to do monitors right everyone needs one. I'd get a bass amp w/tweeter to use as a backline amp for the drum machine when needed.

[quote name='MoonBassAlpha' timestamp='1448981103' post='2919766'] Why are these not used in Valve amplifiers? [/quote]Price, and demand, which are closely related. Aside from valve amps high voltage transformers are rarely used, so there's no economy of scale. Take a look here, you can count the number of 400-500v secondary toroids with no fingers: http://www.hammondmfg.com/182.htm