Using a 550w amp with 250w cab...

[alexclaber]

[quote name='ThomBassmonkey' post='1199451' date='Apr 14 2011, 02:34 PM']Ultimately I'm just asking "if you play quietly, even if your amp's wattage is higher than the speaker's rating, then you won't be pushing too many watts through it?".[/quote]

Yes. But conversely if you turn your amp down but still play loud through it you can hit full power. Lots of amps hit full power with a typical bass and player at less than half volume.

[Darkstrike]

Reading this thread has been interesting, just want to ask if this plan of mine is safe.

I plan on using a Genz Streamliner 600, which is 375w at 8ohms, with a TC RS-112 cab, which is a 200w 8ohm cab.

From what I'm reading, I believe this is pretty safe, as long as I'm playing clean? Would it be so if I was planning on overdriving the pre-amp tubes?

I don't plan on using it really loud, no more than jamming levels really, and most often probably lower.

[pantherairsoft]

[quote name='alexclaber' post='1199653' date='Apr 14 2011, 05:28 PM']Yes. But conversely if you turn your amp down but still play loud through it you can hit full power. Lots of amps hit full power with a typical bass and player at less than half volume.[/quote]

Alex, thanks for your input. Am I correct therefore in saying that my concearns of blowing my cab are quite just... As even playing with the amp turned low could push it to clip or produce way more than the 250w my cab is rated at.

I appreciate this has been answered both by members here and by EA, the general consensus is that unless I'm 'abusing' the amp I'll be fine - however your facts and figures seem to imply (at least in the way I've understood them) that my cab is at considerable risk.

Regards

Shep

[ThomBassmonkey]

I think that from what I've seen here and elsewhere, if your cab sounds alright, then it's probably doing alright. You're just walking a finer line than you would be with a more evenly matched head and cab.

[Bill Fitzmaurice]

[quote name='alexclaber' post='1199073' date='Apr 14 2011, 04:41 AM']Read this: [url="http://barefacedbass.com/technical-information/mythbusters1.htm"]Amp mythbusting![/url]

The Wizzy cabs have very low excursion limited power handling so you'll hear the increasing distortion (with clean sounds) well before thermal failure occurs. The risk from slap is causing such high excursion that the speaker doesn't just distort but completely runs out of travel, thus creasing the cone, buckling the voice coil or damaging the suspension. I think that's fairly unlikely to happen with that woofer but to be sure see if EA can tell you the ratio of Xlim to Xmax.[/quote]The xlim to xmax ratio is important, but a high one is by no means a guaranty of driver durability. When pushed past xmax additional power applied doesn't give more output, it just adds more heat. That tends to result in thermal power compression, which actually reduces output, which one may compensate for with more power, which means even more heat, and so on until the voice coil is toasted. And if the xmax is small this can happen well below the actual thermal rating of the coil. This is in fact the usual reason for blown guitar drivers, which have both very small xmax and high xlim to xmax ratios.
It still boils down to if it sounds bad turn it down. If it sounds clean chances of damage are very slight.

[Monckyman]

Hah! > Just been baffled by bullsh*te.
Ok as you like.

[thinman]

To the OP:

Say you have the amp volume, input gain etc set at something more than 0. With no signal from your bass the amp's power output is 0.

Hit the string and the output from the amp will be something proportional to the level of the signal from your bass and the volume control (including anything else that affects the gain such as input gain, eq etc).

Say then that you have a 250W amp and the input signal and the various gain settings cause the output to need to be more than 250w for the signal from your bass then the amplifier output itself will start to distort. If you had a 500w amp and everything else being equal the output signal would not be distorted.

So, from the speaker's point of view the signal received from the amp is no different from the two amps until the lower power amp is over-driven.

For speakers with a low power handling it could be possible for the sound to be distorted by the speakers themselve even if the amp is not being overdriven - it depends on whose limits you reach first - the amp of the speakers.

And just to re-iterate - amplifer power ratings represent what they can deliver (generally in a short burst). For bass usage the actual output is almost never continuous but variable with the music, i.e. twanging a string hard results in a burst of power from the amp through the speakers that drops down to almost nothing between notes.

I hope that's not patronising - I get the impression that it's a mystery to some what goes on electrically between an amp and speakers.

[Merton]

[quote name='Monckyman' post='1199791' date='Apr 14 2011, 07:19 PM']Hah! > Just been baffled by bullsh*te.
Ok as you like.[/quote]
Not bullsh*te but fact, probably

[Monckyman]

Sorry, I wasn`t responding to the last post,that made a lot of sense. I was referring to Alexclabers superior declamation.

Edited April 14, 2011 by Monckyman

[Merton]

[quote name='Monckyman' post='1200043' date='Apr 14 2011, 10:26 PM']Sorry, I wasn`t responding to the last post,that made a lot of sense. I was referring to Alexclabers superior declamation.[/quote]
So was I

[Bloc Riff Nut]

[quote name='alexclaber' post='1199634' date='Apr 14 2011, 05:18 PM']And they are talking about PA speakers! As someone who designs and builds BASS GUITAR speakers I'd contend that my advice is more relevant and thus more accurate. If you take the time to read everything here:

[url="http://barefacedbass.com/technical-information.htm"]http://barefacedbass.com/technical-information.htm[/url]

and here:

[url="http://barefacedbass.com/bgm-columns.htm"]http://barefacedbass.com/bgm-columns.htm[/url]

you may then understand what I'm talking about.

If you already know all about power density, the lowpass filtering of voice coil inductance and the crest factor of typical bass guitar vs typical program material then my apologies for wasting your time.[/quote]
I thought I was English, but after reading that last sentence I'm having doubts...

[chris_b]

[quote name='Monckyman' post='1199791' date='Apr 14 2011, 07:19 PM']....Hah! > Just been baffled by bullsh*te.
Ok as you like....[/quote]
Just because you don't understand something that makes it bullshit?

[Monckyman]

OK guys enough, if the mad proff gets a lot of luv round here thats ok, but there`s no need for him to make what I thought was a quite rude statement.
Clipping amps is not recommended by anyone I know in the industry,not P.A amps, not guitar amps,not bass amps.
OVERDRIVING them is different, that`s pe-amp stuff, not OUTPUT amp.
If the barefaced stuff is different then ok,happy days and i want one. But no need for the complete "you may not actually have a brain so I`ll try to explain in monosyllables" stuff I got from him. right. Done.
Have a nice day

[lemmywinks]

[quote name='Monckyman' post='1200382' date='Apr 15 2011, 10:30 AM']OK guys enough, if the mad proff gets a lot of luv round here thats ok, but there`s no need for him to make what I thought was a quite rude statement.
Clipping amps is not recommended by anyone I know in the industry,not P.A amps, not guitar amps,not bass amps.
OVERDRIVING them is different, that`s pe-amp stuff, not OUTPUT amp.
If the barefaced stuff is different then ok,happy days and i want one. But no need for the complete "you may not actually have a brain so I`ll try to explain in monosyllables" stuff I got from him. right. Done.
Have a nice day [/quote]


You've been a member here for 5 minutes.

Pipe down.

[alexclaber]

[quote name='Monckyman' post='1200382' date='Apr 15 2011, 10:30 AM']OK guys enough, if the mad proff gets a lot of luv round here thats ok, but there`s no need for him to make what I thought was a quite rude statement.
Clipping amps is not recommended by anyone I know in the industry,not P.A amps, not guitar amps,not bass amps.
OVERDRIVING them is different, that`s pe-amp stuff, not OUTPUT amp.[/quote]

Dear Mr Monckyman,

The only reason I'm saying anything is because what you're saying is wrong. I totally agree that it's not a good idea to clip the amps driving PA tops or full-range cabs. (It's fine clipping PA subs). However, you are way off the mark regarding guitar amps - all the classic rock guitar sounds are derived from clipping the output stages of valve amps. Bass amps live along a continuum sitting between PA stuff and guitar stuff whilst he input signal is much more like than from a guitar than that from recorded music.

Many classic OVERDRIVEN sounds are the result of overdriving OUTPUT amps. And not only valve amps, solidstate amps too (GK stuff being a notable example).

If you remain convinced that you must never ever ever clip the output stage of your bass amp then you will either have to use a ton of compression and limiting or you will end up taking a rig to your gigs that is about four times as large that it needs to be.

Constant clipping is rarely a good thing - but frequent clipping is perfectly normal and should be expected unless you're playing a quiet gig with a big rig.

Best regards,

Alex

[Monckyman]

Right, I had to delete my first reply to lemmy, and chill a bit.
Please don`t be telling me to "pipe down" have a little respect this way eh?
New or not I have an opinion, it`s a forum for exchanging those, and I gave mine.
If you think I have said anything the mods may take umbrage at, then notify one and put it to them.
Thank you,
MM

Edited April 15, 2011 by Monckyman

[Monckyman]

OK Alex, thank you for your reply, it was very enlightening and provides food for thought.
MM

[lemmywinks]

Apologies for the "pipe down" bit, probably a bit unneccessary.

One of the best things about this forum is that we have quite a few genuine experts who offer advice you just can't get at your local guitar shop. I would hate to think they might not post as much because of umpteen challenges from people who just don't possess equivalent knowledge.

It's not so much that Alex and BFM et al get "a lot of love", nobody sucks up to them. It's just that they're the most qualified people to answer questions on this subject, they are well respected for a reason.

I for one have found their presence on here extremely beneficial.

[pantherairsoft]

Glad this is back on track.

All my questions have been answered from both a rational and technical angle. Cheers guys

Shep

[Monckyman]

Thanks for the reply,Lemmy.
What I meant by " a lot of luv" was respect.I didn`t intend to imply any sucking up.
I agree with the expert thing also,Alex is clearly well qualified in his area. I just thought at the time the way he replied was a little condescending.
Once again I apologise for any offence given to anybody, I`m quite an opinionated 47 year old and don`t really have enough patience for forum arguments.
I`ll have to look at the clipping thing again, maybe it`s my P.A background, but it makes me uncomfortable thinking about it.
More research needed by me.
MM

[lemmywinks]

No need for an apology, also i wasn't referring to you in my previous post either, it was mainly an observation of many previous threads where that has happened.


I should probably re-read my posts before clicking the mouse button!

[Bill Fitzmaurice]

[quote name='Monckyman' post='1200382' date='Apr 15 2011, 05:30 AM']Clipping amps is not recommended by anyone I know in the industry,not P.A amps, not guitar amps,not bass amps.
OVERDRIVING them is different, that`s pe-amp stuff, not OUTPUT amp.[/quote]Clipping and over-driving is exactly the same thing. As for clipping power amps, that's precisely what one does with cranked guitar amps, and damaged drivers do not ensue. The Martin document unfortunately is very flawed, as it doesn't distinguish between the potential for damaging tweeters (high frequency devices) with clipped waveforms versus woofers, which are completely and totally immune to damage. This document does make the distinction, though more than a few wags have managed to overlook the specific reference to [i]high frequency components[/i] and pronounce that 'clipping kills drivers', giving rise to the myth of underpowering:
[url="http://www.jblpro.com/pub/technote/lowpower.pdf"]http://www.jblpro.com/pub/technote/lowpower.pdf[/url]

Edited April 15, 2011 by Bill Fitzmaurice

[Monckyman]

Thanks for that Bill, I`m starting to realize that guitar amps useage can be a lot different than power amp useage.
Then again, with statements like " Do not drive the amplifier into clipping, Clipping sounds
something like a stylus mistracking. and generally occurs on
loud passages when the system is played at loud volume levels.
If clipping occurs regularly, turn down the volume level or
install a larger amplifier that can deliver the required power
without distortion. "
From documents like that and you can see why it`s easy to confuse the issue.
MM

[thinman]

[quote name='Monckyman' post='1200727' date='Apr 15 2011, 02:23 PM']Thanks for that Bill, I`m starting to realize that guitar amps useage can be a lot different than power amp useage.
Then again, with statements like " Do not drive the amplifier into clipping, Clipping sounds
something like a stylus mistracking. and generally occurs on
loud passages when the system is played at loud volume levels.
If clipping occurs regularly, turn down the volume level or
install a larger amplifier that can deliver the required power
without distortion. "
From documents like that and you can see why it`s easy to confuse the issue.
MM[/quote]

Alex alluded to this but think of it this way: Say you had a synth set to produce a square wave then to reproduce that sound the amplifier has to deliver that same waveform to the speaker or it wouldn't be a faithful reproduction. OK, that's not the same as clipping the amp but it's producing a waveform with a flat (ish) top - from the speaker's point of view it matters not whether that's coming from a clipped power stage or not.

[pantherairsoft]

After a few hours of running said amp with said cab I can report they sound amazing together with no worries.

All good