Why do we need so much power?

[SlapbassSteve]

[quote name='Dad3353' timestamp='1403990166' post='2488404']
This is fine [i]if[/i], and it's a big 'if', the band PA cuts the mustard. If my band are playing out with our autonomous PA, it won't carry the bass with anything like the conviction of our Hiwatt 200. If we're playing with a venue FOH, of course, that's fine. We still prefer the Hiwatt, though, for the stage sound
[/quote]

Very true! My last band was a pub covers job, used to use a pair of DB Technologies DVX D15HPs with them, and then now I've only got to keep up with a few ukuleles a pair of Mackie SRM450s are practically overkill for any pub/function we've played.


...That said, as nice as a DI'd bass sounds, there's nothing like standing in front of a big 8x10 and feeling the sound hitting your back and shaking the floor beneath you!

[molan]

I'm sure there is an element of output quotes differering widely from manufacturer to manufacture.

TC Electronic are probably the most often quoted with their 450w heads only being about 235w but there's plenty of other examples too.

I know of one builder who consistently quoted their top of the range heads at 900w whilst the power module was identical to someone else who rated it at just 500.

I also heard an 800w power amp recently that was deafening at about 9 o'clock with a bass plays quietly through it.

[LukeFRC]

[quote name='SlapbassSteve' timestamp='1403989581' post='2488397']
This is why I binned off my Markbass stack and have been DI-ing ever since. A good set of PA speakers will have a much wider range than most bass amps and to my ear they sound much more neutral... a little bit of EQ/gain on the desk and it's all good!
[/quote] woah PA speakers... will be in part be due to the amps and part due to the speaker design... so there are two things going on there. I would agree with you - I'm half tempted to get rid of my rig and just run the preamp into a powered speaker of some kind.

[quote name='molan' timestamp='1403998368' post='2488489']
I'm sure there is an element of output quotes differering widely from manufacturer to manufacture.

TC Electronic are probably the most often quoted with their 450w heads only being about 235w but there's plenty of other examples too.

I know of one builder who consistently quoted their top of the range heads at 900w whilst the power module was identical to someone else who rated it at just 500.

I also heard an 800w power amp recently that was deafening at about 9 o'clock with a bass plays quietly through it.
[/quote] did you read the doc from TC I linked to? it's quite interesting what they've done - also the fact that the RH450 and 750 have the same continuous power rating - but the 750 can have bigger burst peaks.

and was the example of a 800w power amp a good one or a bad one? what was it? (if you can say)

[molan]

[quote name='LukeFRC' timestamp='1404000024' post='2488503']


did you read the doc from TC I linked to? it's quite interesting what they've done - also the fact that the RH450 and 750 have the same continuous power rating - but the 750 can have bigger burst peaks.

and was the example of a 800w power amp a good one or a bad one? what was it? (if you can say)
[/quote]

I have read a lot about TC's measurements and methods. My biggest concern with them are they when I've gigged one it was the biggest sucker of any usable tone I've ever encountered. Literally awful sound in a live band context and yet sounded good when tested in a shop and set up at home.

How much of this was down to the power control and how much to the highly processed tone circuits I don't know but it really put me off them.

The 800w power stage was a Demeter. It was actually installed internally in a Monique pre-amp and we couldn't believe how loud and powerful it was.

Had to get a tech to put some capacitors in the circuitry to lower the pre-amp output (or something along those lines!) because the power was just overkill!

[Phil Starr]

Thanks for the article, should have remembered that really because there was a long thread on this a while ago. It probably wasn't the best example to choose I think the rest of what I said is about right though.

One of the advantages of this DSP approach is that you are far less likely to blow your speakers through over excursion in return for very little signal distortion/loss of sound.

[LukeFRC]

[quote name='Phil Starr' timestamp='1404024595' post='2488528']
Thanks for the article, should have remembered that really because there was a long thread on this a while ago. It probably wasn't the best example to choose I think the rest of what I said is about right though.

One of the advantages of this DSP approach is that you are far less likely to blow your speakers through over excursion in return for very little signal distortion/loss of sound.
[/quote]Phil - as one of our resident experts in all things speakers... what's your opinion on DSP like the active power management in the TC amps?

EDIT: reason asking is I demoed the RH750 yesterday and can't get my head around if I liked it or not.

Edited June 29, 2014 by LukeFRC

[grandad]

Thank you, an interesting article from TC, especially the part on how we perceive bass loudness, the rms level & not peak.

For several years in a 60's cover band I used a Peavey Max160 ss head into an Ampeg 115 cab. With gain & master at about 12ish it had ample headroom for pubs & clubs.

I think conventional amps were rated by the electrical power they drew from the power supply, i.e. a 100 watt power amp could draw 100 watts of D.C. electrical power from the power supply & convert that into A.C. electrical power which is fed to the speaker. That process with a class AB is I think less than 70% efficient.

The conversion of that electrical energy to sound energy via the speaker (2 - 5% efficient) only leaves us a few watts of acoustic power but I believe a whole orchestra might only produce 10 watts of acoustic power at max.

The simple Pout/Pin formula I suspect would not suffice for modern amp design, to much jiggery-pokery going on which would not equate with what we hear.

How much power one might need I suppose depends on the type of music you play & where you play. At the outdoor gigs I've done I was always amused as my watts just disappeared into thin air!

Edited June 29, 2014 by grandad

[chrismuzz]

[quote name='owen' timestamp='1403989007' post='2488389']
You can pluck harder and the amp does not complain or give up, it just gets louder.
[/quote]

Haha, I used the famous Carlsbro Stingray at rehearsal the other day... Whenever I hit a low Eb the inbuilt limiter hit so hard it took about half a second for any sound to come through

[chrismuzz]

Which brings another benefit of higher output power... Dynamics!

(Obviously, with the amount of compression and overdrive I use that makes no difference to me )

[Owen]

[quote name='LukeFRC' timestamp='1404027019' post='2488540']
Phil - as one of our resident experts in all things speakers... what's your opinion on DSP like the active power management in the TC amps?
[/quote]

DSP is everywhere. Everything we listen to unless it is live music in a sub 500 seater venue is processed. When you play through grown up PA systems you have been DSP to the max. DSP done properly is lush. I cannot speak for the TC stuff cos I have not experienced it. I have DSP in my rig and it is super-duper.

[LukeFRC]

[quote name='owen' timestamp='1404059997' post='2488871']


DSP is everywhere. Everything we listen to unless it is live music in a sub 500 seater venue is processed. When you play through grown up PA systems you have been DSP to the max. DSP done properly is lush. I cannot speak for the TC stuff cos I have not experienced it. I have DSP in my rig and it is super-duper.
[/quote] I know your rig has great DSP .... I meant specifically on the tc stuff.

[k50]

The blacksmith works for me Luke.

[Phil Starr]

Sorry, speakers I'm OK with but I'm no expert on any particular bit of DSP. I really can't tell you if one manufacturer has done a good job and another not so much. A couple of observations though.

Signal processing is something we've been doing for as long as there has been amplified music. Doing it digitally should be no different to making the same changes with analogue processing other than it should be easier and cheaper. If some analogue gear currently sounds 'better' than digital then this is temporary, the digital processing will get better and cheaper eventually overtaking it. My taste is for as little processing as possible, nothing on my mixing desk ever goes past 2 o'clock, reverb sparing and little or no compression.

The thing is with digital that once you have a really fast computer controlling your sound your options are almost unlimited. As many channels of eq as you like, all parametric if you want, filter any frequency you want, let the computer kill feedback or do your eq for you, protect the speakers , apply compression to any channel or split the signal and compress each part differntly etc etc. Now this promises sonic perfection, but if the organic bit operating the knobs (or even the software developer) gets it wrong the opportunities to sound nasty multiply as well.

I'm open minded about it really, excited by the possibilities but not yet impressed by the amp/speaker simulations on offer for example. It'll come but I think we aren't quite there so far.

I'd love DSP on my PA though. If I was mixing out in the audience I might be able to out compete the DSP (or not) but stuck up on stage with a bass in hand it's pretty difficult to think I could adjust the eq as the room acoustics change because of the audience coming in or kill feedback effectively. Most of us don't have the luxury of a sound engineer so DSP frees us to concentrate on the music.

[brensabre79]

Here's my take on this.
Actually power is logarithmic, so to get twice as loud (+3dB) as 10 watts, you need 100 watts, twice as loud again and you'll need 1000 watts etc. etc.
However you don't need all those watts all of the time. Look at the sketch below, you'll see the hypothetical bass note being played and the amount of power required for a fixed volume. The 100 watt amp copes with most of the wave, but will clip a little bit at the attack of the note- this is hardly noticable, to some it'll sound a bit dirty (lovely on a valve amp, a bit unpleasant on a SS amp). This is basically what a compressor does too but in a more gentle way, so a SS amp with a well set-up compressor would be passable.

The 10 watt amp is clipping quite a few of the wave peaks so it will just be farty and distorted. The 1000 watt amp copes with all of it, including the attack which is why it sounds super clean, although it's barely ticking over for most of the duration of the note...



PS: the diagram is not well scaled!

Edited June 30, 2014 by brensabre79

[SubsonicSimpleton]

Isn't there a big difference between how an oldschool amp (tranny or valve) can cope with these transients compared to modern class D offerings with switch mode supplies - my understanding is that a well built old school power supply with it's big heavy transformer and enormous smoothing caps can supply the sudden demand for power at the big transients far in excess of it's rated ability to deliver continuous output.

[brensabre79]

[quote name='SubsonicSimpleton' timestamp='1404136185' post='2489582'] Isn't there a big difference between how an oldschool amp (tranny or valve) can cope with these transients compared to modern class D offerings with switch mode supplies - my understanding is that a well built old school power supply with it's big heavy transformer and enormous smoothing caps can supply the sudden demand for power at the big transients far in excess of it's rated ability to deliver continuous output. [/quote]

I think you're probably right there, I know that valve amps tend to naturally compress the signal, which I think is why many modern amps have a compressor / limiter built in to get this desirable squashing of the signal.

There's also the entirely different debate over 'marketing watts'. Some manufacturers give their amps model names that suggest much higher power than they are capable of, some list the Peak power (not RMS). Many rate their wattage under specific conditions (e.g. 1Khz sine wave for no longer than 3 seconds). Some even use their own terminology (e.g. 300 watts Music Power). There's also other ratings to consider (e.g. THD - total harmonic distortion) This is basically a measure of the signal breaking up into distortion, not very desirable from a HiFi, but guitarists love it!

So we're not exactly comparing apples with apples anyway.

Bring in other factors - like with valve amps. I nearly doubled the output of my valve amp when I biased the valves 'hotter' - I was able to adjust the bias so that I was getting around 30W (calculated) out of each tube instead of the conservative 20W per tube it was delivering beforehand. That said, it is rated at 160W on the badge, it was getting 120W max before, but now capable of 180W at full chat. It's nowhere near as clean sounding, or as loud as my 500W Class 'D' amp though.

[grandad]

Yes, hearing is logrithmic.

Starting at 10 watts, +3dB doubles the power output to 20 watts. Another +3dB doubles the power output to 40 watts. Another +3dB doubles the power output to 80 watts.

At this point, (+9dB) we might perceive that the [u]loudness[/u] has just about doubled.

My PA is a Yamaha EMX 5016, (500 watt per channel peak). The led meter has +6dB headroom, (red/orange led's). If I kept the output in the green hovering around 0dB I'm only outputting 125 watt per channel & that seems pretty loud to me FOH.

500W - 3dB = 250W - 3dB = 125W. We only need the larger wattage for headroom.

Some system of limiting/compression would be wise to protect speakers & ears.

Edited July 1, 2014 by grandad

[3below]

Speaking as a bass player who has 2 x 700W amps, I have (re)discovered the secret weapon. Playing quietly (now tell that to the drummer) has paid dividends over last few weeks. I am heading towards small stage kit and stick it all through PA (with DSP).

[Musicman20]

All I can add is from using the TC amps in a band context, they sound even better in the mix (THE best DI I've used) but it all depends if you like the 'sealed 810 being pushed' tone.

[thodrik]

I've never needed more than a 300 watt solid state head, but having a ridiculously loud 400 valve amp is nice too.

[xgsjx]

Isn't all these watts subject to what the cab can do with them?

[Happy Jack]

Just get more watts.

http://www.ebay.co.uk/itm/CHEVIN-A6000-POWER-AMPLIFIER-2x-3-000W-into-2-ohms-/301231406069?pt=LH_DefaultDomain_3&hash=item4622ca7bf5

[Conan]

[quote name='Happy Jack' timestamp='1404287415' post='2491054']
Just get more watts.

[url="http://www.ebay.co.uk/itm/CHEVIN-A6000-POWER-AMPLIFIER-2x-3-000W-into-2-ohms-/301231406069?pt=LH_DefaultDomain_3&hash=item4622ca7bf5"]http://www.ebay.co.u...=item4622ca7bf5[/url]
[/quote]

Pah! With my 8 ohm cab it would only give me 2400 watts...

[LawrenceH]

I think Phil's point earlier, that modern speakers are actually less efficient, is very significant not just in terms of the issue of why we seem to need 'more watts' these days, but for the implications this has for the sound of modern bass guitar.

[razze06]

Because moar is moar. Moar wattz.