alexclaber

Ampeg made a rather good 4-way cab (true 4-way, not simply four different speakers in a box, all running fullrange) called the Extreme. 2x6.5"2x10"1x18"+tweeter. Most of the enclosure was given over to the 18" which was quasi-downfiring/horn-loaded to acoustically low-pass filter it. The 10"s were in a very small sealed-enclosure to high-pass filter them and then the 6.5"s and tweeter passively crossed over. Good design, only downside was the weight! You could run it fullrange or biamp the 18" and the other speakers separately. Most multi-speaker cabs don't use any kind of filtering so the sound is just the same as if you stacked two dissimilar cabs. Alex

The Big One by barefacedBass - 15" woofer + 6.5" mid with a full crossover. Magic! Alex

If your volume knob is at 5 out of 11 that does not mean that your amp is only producing under 50% of its maximum power, in fact you are likely to be reaching full power quite frequently when playing louder low notes. Even when turned down to 2 out 11 if you slap a low B string note you could easily take the amp beyond its limits. Alex

Tie-breakers - Family Man! And Larry Graham to replace the 5th place posse of close but no cigars... Alex

[quote name='lwtait' post='316167' date='Oct 27 2008, 09:19 PM']whats the point? he might as well keep the g string just in case. its not like it makes a difference to neck width or feel or anything.[/quote] I gather he kept breaking them and couldn't afford to replace them back in the day. I guess if you're almost solely playing constant 8th notes with a thick dirty sound then you're better off going up the neck rather than onto a thinner string and the top frets on the D-string go plenty high enough for that kind of playing. One less string to mute as well. Alex

Completely missed that this was happening! Shame as I'm sure they'd have appreciated hearing the new cabs, I gather GAS is only ever a good thing... Alex

[quote name='BigBeefChief' post='315627' date='Oct 27 2008, 10:42 AM']Played a gig on saturday night (originals band) and realised at the end that I only use the G string in 1 song (our set is only 8 songs), and use it a grand total of 14 times in that song. I'm thinking of getting a 3.[/quote] DIY 3-string: Alex

[quote name='cd_david' post='315513' date='Oct 27 2008, 07:36 AM']Dull and un-inventive album always trotted out by Beatles fans as their primary defence, some decent songs granted but groove????[/quote] Groove is not simply being funky. McCartney's timing is so solid and his control of note lengths spot on. The same kind of skill shown by the great country bass players. Alex

[quote name='Beedster' post='315397' date='Oct 26 2008, 10:14 PM']Must have missed it in the 30,000 or so times I've listened to it [/quote] You too can join the list. Alex

[quote name='cd_david' post='315061' date='Oct 26 2008, 01:59 PM']Light blue touch paper and retire! Come on, I admit the Beatles wrote some good songs but lets not get carried away, McCartney is one of the most pedestrian bass players ive had the misfortune to listen to. It seems to me his "rank"amongst bass players is built more on nostalgia and his membership in a famous band than on his ability. I love SLF but would never state that Ali McMordie is the best player. Yes, I know my opinion is worthless etc but come on, you have to admit there is better than him about??? I await the barrage of "but what about choice of notes" etc LOL Dave, tongue firmly pressed in cheek,[/quote] The reassuring thing when I hear other bassists write off McCartney as a significant player is it means I can ignore their opinions on anything else because they clearly don't get 'it'. I thus won't try to explain why he matters but will recommend visiting Sgt Pepper for enlightenment. 'It' is not that hidden - the combination of groove, tone, melodic and harmonic ideas is up there with the very best. Alex

[quote name='SteveO' post='314710' date='Oct 25 2008, 08:08 PM']yes, thicker strings and higher tension will mean less excursion (displacement/amplitude) we can all agree with this from experience of playing, but how do you make the leap from that statement to say that longer scale length and higher tension also equals less excursion.[/quote] Higher tension equals less excursion however you achieve it, be it through higher tuning, heavier strings or longer scale. Bear in mind that as the string vibrates it transfers energy back and forth between kinetic and potential (as in a spring) states and the higher the tension of the string the less the string has to be stretched to achieve a given rise in potential energy. Once you understand this you start to see why claiming that tension is fixed for a given tuning, scale length and mass per unit length isn't totally correct - static tension is fixed but dynamic tension (i.e. feel) varies significantly depending on how energy moves around the string/bass guitar system. Alex

Your book is definitely wrong is making such a black and white statement, pretty wrong full-stop in fact. Increasing scale length for a given pitch and mass per unit length makes the string act more like a perfect string - i.e. more fundamental and more even distribution of harmonic content. You might call this the 'piano sound' - that huge rich open sound with tons of top but also tons of bottom. Doing the opposite effectively bandpasses the tone, reducing the content of the lowest and highest harmonic. You can easily test this by tuning your A-string down say four semitones and comparing the tone between a 1st fret A# on the standard tuning and a 5th fret A# on the drop tuning. The greater the mass per unit length and the tension, the less the excursion for a given pitch and energy input. So longer scale high tension strings will exhibit less excursion than shorter scale low tension strings for a given player. However the reduction in fundamental and lower harmonic sustain on a shorter scale could mean that by the time the string vibration has rotated from parallel to perpendicular to the frets that the lower frequency content has diminished so much that you can use a lower action without buzzing. Note that the most low frequency energy in a string the more that it moves, and also that when a player with good technique plucks a string it starts moving in the same plane as the frets. Alex

[quote name='escholl' post='314487' date='Oct 25 2008, 01:19 PM']i'm guessing by the octave difference part you mean they're -3dB at 44-ish Hz while they're at their max SPL, or something like that? I don't remember what those graphs were called that you had, something about frequency response at max SPL -- is this what you mean here? [/quote] No, they're actually about -3dB @ 44Hz with 1W, that's their true frequency response. The Beyma 21" is a good driver (though quite expensive) but it is crippled in that relatively tiny cabinet - it needs to be in a box the size of a fullsize 2x18" PA sub to really do what it's meant to do, i.e. something of about twice the volume of an Ampeg 8x10" and far far larger than the AccuGroove enclosure. It's like putting a 1000bhp engine in a super-aerodynamic car to break the diesel engine speed record but only setting the gearing so in top gear it hits the redline at 100mph, not 300mph! Alex

[quote name='bass_ferret' post='314565' date='Oct 25 2008, 04:06 PM']yes there is: [b]You can use any power ouput amp with any power handling cab. If any of these combinations makes bad sounds then turn down and/or stop cranking the bass EQ excessively or damage may occur[/b][/quote] My general guideline works in 99% of cases. The cases where it might fall down are when a bassist is using a deliberately nasty sound and thus can't tell good nasty from bad nasty or where the amp power vs thermal power handling ratio is so large that thermal damage occurs before the onset of mechanical damage - I've heard of this happening once when bridging a large power amp into a single Acme Low-B2 2x10" and EQing down the bottom to get maximum output, the result being a melted voice coil. That takes some doing though! Alex

[quote name='bass_ferret' post='314113' date='Oct 24 2008, 08:13 PM']The 21inch woofer is not a myth. It was an architectural hifi driver made for the US market by Electrovoice.[/quote] I was actually referring to the Whappo Grande made by AccuGroove which uses the Beyma 21" woofer. It does indeed exist but their -3dB @ 22Hz and -6dB @ 19Hz frequency response claims are more than an octave different from reality! Alex

[quote name='Thunderhead' post='313948' date='Oct 24 2008, 04:41 PM']Whatever. Next time you blow a PA cab, don't worry, it couldn't have happened.[/quote] Wow, does my assertion that a clipping amp does not produce DC now mean that no speaker cab can be blown because only DC can blow speakers?! If you've observed my posting elsewhere you will note that I am generally open-minded. The exception is when I am having to defend the TRUTH and FACT from those that insist on spreading inaccuracy and myth. You make some good points and you clearly know your stuff on many technical subjects but that doesn't mean you can't be wrong on other subjects. Alex P.S. I shall now await a post from someone who got told that clipping causes DC which kills speakers by a bloke in a guitar shop... P.P.S. And then later someone who's just discovered a 21" speaker cab which goes to 20Hz...

I love playing chords on the bass - they have their own unique sound, not like a guitar and I'm sure that is maintained even with the thinner strings on an ERB because the scale length has such an effect upon tone. For me five strings and twenty four frets is enough (in fact four strings and twenty four frets is enough for the chordal work though the extra lower string comes in very handy on the groove side of things) but I can see why more strings could be of benefit for some. I also like how an extra-long scale (36" in my case) separates the tone of the bass even further from the guitar allowing you to do guitarry things but maintain a unique identity and sonic position. Alex

[quote name='Balcro' post='313802' date='Oct 24 2008, 01:59 PM']A brilliant exposition, gentlemen and I wouldn't dare to intervene. There are still 2 rounds to go and by my reckoning and a slight "non-scientific feeling" Thunderhead is probably ahead by 15 points to 14.[/quote] Actually by repeatedly repeating the myth of clipping=DC Thunderhead has unwittingly opened himself up to a knockout blow. It's rather disappointing to have to get involved in these arguments but if I don't then everyone who reads this thread will continue repeating the same new bs. Ten years ago I never heard this - just goes to show why a little knowledge is such a dangerous thing. Alex

[quote name='Thunderhead' post='313729' date='Oct 24 2008, 12:49 PM']If the time frame you are looking at is less than half the frequency, the polarity does not change. For the duration of half the fundamental frequency (and remember that clipping the output stage effectively reduces the frequency to that because it obliterates all the higher components) what you have is DC. I agree that what you have is a square AC waveform [i]overall[/i], but it [i]can also be[/i] described as sections of DC separated by transients. The fact that they do alternate in polarity is irrelevant if you consider what is happening [i]in the duration of each section[/i]. Both ways of looking at it fit the waveform but the 'alternating DC' description explains more usefully why a clipped waveform can be so damaging to speakers, especially cabinets with crossovers. It isn't [i]just[/i] to do with the increased power when clipping occurs (although that is significant too).[/quote] You may enjoy throwing away the science to prove your point but it doesn't make you right. If you pass a square AC waveform at 220Hz (so a fully clipped amp with a bassist running extreme feedback on a sustained 14th fret G-string A) through a 2nd order lowpass filter set at ~500Hz the filter will only pass the fundamental and the 2nd harmonic fully, some of the 3rd harmonic, hardly any of the 4th harmonic and so on. It will not pass your claimed 0Hz DC signal because it isn't zero Hz DC. Any crossover (or any reactive component) has a time element in how it works with the input signal and claiming that a snapshot of the signal during a fraction of the waveform is representative of real-world usage is ridiculous. Your 'alternating DC' description of why a clipped waveform can be damaging is totally incorrect and to be perfectly frank I am getting very tired of arguing this with every new forumite who thinks he understands the subject but doesn't. If you pop along to talkbass and do some searches there you will see that I am not the only person telling you that this DC rubbish is wrong. Alex P.S. If you wish to be pedantic there is a minor issue of DC offset affecting cooling but it is nothing to do with your claims of 'alternating DC' and with high Xmax drivers it makes little difference when there is always a large portion of poorly cooled voice coil outside the magnetic gap.

[quote name='Thunderhead' post='313658' date='Oct 24 2008, 11:27 AM']Alex, a square wave IS sections of DC - each the length of half the complete waveform, and of alternating polarity - separated by vertical transients. Just look at it on a scope. Yes, it's [i]also[/i] an AC square wave.[/quote] DC never alternates. That's it, end of argument. [quote name='Thunderhead' post='313658' date='Oct 24 2008, 11:27 AM']A clipped solid-state power section is quite capable of producing this (subject to the slew rate of the output devices, which makes the transients not quite vertical). Again, look at it on a scope.[/quote] Yes it can, where did I say that it can't? I just pointed out that your incorrect definition of there being DC involved is very misleading and incorrect. [quote name='Thunderhead' post='313658' date='Oct 24 2008, 11:27 AM']To the crossover, the sections of DC are 0Hz and so will be sent exclusively to the bass driver.[/quote] The flat top sections of a square are not zero Hz, they have the same fundamental frequency as the unclipped note. See the FFT I posted previously. [quote name='Thunderhead' post='313658' date='Oct 24 2008, 11:27 AM']I know the bass driver cone does not perfectly follow this - it can't due to its mechanical inertia - but it will try, and the lower the frequency the closer it will get. Connect a signal generator to a speaker and watch what happens to the cone as you lower the frequency with a square wave input.[/quote] You may understand the workings of an amp but you clearly do not understand how a speaker works! The voltage applied to the voice coil causes current flow. That current flow generates force in the motor which causes cone acceleration. That acceleration causes velocity. That velocity causes a displacement. Therefore the displacement can be calculated by integrating the current (i.e. force i.e. acceleration) to get velocity and integrating the velocity to get displacement, all the while bearing in mind that voltage and current are related by the variable impedance curve including the reactive elements (the speaker is not a simple resistive nominal load). Integrate a square wave and you get a triangular wave. Integrate a triangular wave and you get a sine wave. Alex

Jaco Jamerson Family Man (Larry Graham and Willie Weeks just missed the cut!) Alex

[quote name='Thunderhead' post='313633' date='Oct 24 2008, 10:49 AM']But in a cab with a crossover driven by a solid-state amp with a full-range frequency response, it's very different. A clipped signal starts to approximate a square wave, which is effectively a series of sections of DC separated by sharp transients - ie entirely composed of extreme low and extreme high frequencies - and a solid-state power section is quite capable of delivering this since there is no output transformer. If the crossover is really efficient, it will then send the full power of the amp alternately to the bass driver and the tweeter, instead of evenly distributing a range of frequencies...[/quote] No. A square wave is not sections of DC separated by sharp transients, it is an AC square wave. The crossover will definitely not send full power alternately to the bass driver and tweeter, it will continue to filter the output as described by its highpass and lowpass functions. This shows the harmonic composition of a perfect square wave (first 20 harmonics shown): Note that the voltage drops with frequency so the tweeter will never receive as much power as the woofer. However tweeters always have much lower thermal power handling than woofers and the increased HF content in a distorted signal can cause overheating. [quote name='Thunderhead' post='313633' date='Oct 24 2008, 10:49 AM']Exactly, but it CAN happen with a 500W PA amp clipping into a 1000W cab, because a clipping 500W amp can be putting out up to 1000W (the energy contained in a square wave is double that in a sine wave of the same peak voltage[/quote] This is the risk with a clipped amp - increased total power output. It isn't as bad as the simple analysis suggests though because of the lowpass function of the woofers' inductance reducing the current flowing at higher frequencies. [quote name='Thunderhead' post='313633' date='Oct 24 2008, 10:49 AM']and even if it's not a full square wave the energy rises drastically as soon as clipping is reached), and the individual drivers in the PA cab won't be able to handle this - especially the tweeter, which will more likely be rated around 300W.[/quote] The energy seen by the tweeter (and/or midrange speaker) increases dramatically at clipping. The energy going into the woofer does not. [quote name='Thunderhead' post='313633' date='Oct 24 2008, 10:49 AM']The bass driver may not like being hit with bursts of DC at that sort of power level either... DC is very bad for speakers because it does not allow the voice coil to cool itself properly as it is not actually moving while it's absorbing the power..[/quote] This is completely untrue. In an amp that is not broken there should be no DC output. A square wave is not DC. Even if a woofer had a square wave applied to it the inductance of the woofer would make the wave less square. The woofer does move during the flat sections of the AC square wave - woofer position does not match the wave shape, it matches the double integral of the current wave (which itself is derived from the square voltage wave applied to the impedance function of the speaker). I agree that if you're into dirty bass sounds and/or use lots of FX pedals it is wise to use speakers with more rather than less power handling. If you prefer clean bass sounds then you are extremely unlikely to ever run into thermal problems. Distorted signals are prone to overstressing high frequency components but a good speaker cab should be designed to handle these signals and if need be should incorporate protection circuitry. Alex

[quote name='Moo' post='313497' date='Oct 24 2008, 05:03 AM']If the amp is rated higher than the cabs, it could in theory sound very clean and 'Hi Fi', but one slip with the volume knob, or one slap too hard will result in fried cabs.[/quote] Nope. Thermal damage requires enough continous power to overheat the voice coil. Bass playing has loud and quiet bits - the only time you might be able to sustain full power for more than a brief moment is when using overdriven feedback or an all-out fuzz pedal. Using an amp with much greater power than your speaker cab is often futile due to the miserable low frequency (excursion limited) power handling of most bass cabs. Having enough power that your amp never clips will reduce the risk of damage to tweeters and midranges. Woofers are not bothered by clipping, only by too much continuous power (thermal damage) or massive spikes of low frequency power (mechanical damage). The vast majority of damage to bass guitar speakers is mechanical, not thermal and can always be avoided by turning down or reducing the bass EQ on your amp in response to farting noises from your cab. Alex

[quote name='EBS_freak' post='312626' date='Oct 22 2008, 11:39 PM']Yeah - the alembic preamps are something special. Based on Fender preamps if I recall.[/quote] And now you can get that same preamp topology in a dead cheap but amazing sounding Hartke! Alex

If the clip light is near the gain knob then it's 99% likely to be monitoring the preamp. In that case, ignore it. Do whatever you like with the knobs to get the sound you want - the only thing you need to worry about is making the speakers make bad noises by turning the volume up too high and/or boosting the lows too much. When that happens you'll hear a distinctive farting sound warning you that they're not happy. At that point either turn down or reduce the lows. The fan should switch on when the amp gets too hot. You're generally fighting a lost cause to be heard with a cheap 2x10" and a low power amp in a teenage rock band - either get your bandmates to turn down or get another matching cab (which will make a huge difference in loudness). Remember that midrange is your friend if you want to be heard! Did you get a manual with the amp? Does it have any useful information in it? Alex