Guitard Centre for mental health question...

[xOriginalNinjax]

So, I was at GC yesterday, just perusing the store, and was playing an OLP MM2 through a GK 1001RB and matching 410 (very nice btw...loved the tone) and the sales rep is talking to a guy. The guy asks about playing guitar through bass stuff, and the rep says the usual "no, guitar stuff is for guitar, bass stuff is for bass, you mismatch and you'll blow stuff" routine. To which the guy basically calls his BS and says something about frequency and yadda yadda. Then the guy starts asking about heads for cabs, and if he should under or overpower his cab. The guy goes, "You should ALWAYS overpower your cab, if you underpower it, it will destroy the speakers in the cab and you'll have to replace your speakers." Which I replied kindly with some of the things people have said here about speakers and clipping and such, and about how Hasbeen and AgedHorse both said stuff about how overpowering and clipping can do damage and he shrugs me off like I'm a pest, so I just turned up and kept playing. I was right wasn't I? It's always better to underpower a cab rather than over power it, because otherwise you risk blowing the drivers...I mean, from what I understand it'd be better to get a high power handling cab(s) and find a head that you can run that's under that power rating and thus not have to worry about over-driving your speakers...but am I wrong? I mean, headroom is never bad, but on a 200-300w cab like they were talking I'd rather underpower...have I been mistaken?

[B-Bottom]

it was always my understanding that it's better to overpower your cab (to a degree) rather than underpower it.

[thelurker]

The long and short of my understanding (I'm a recording guy, not P.A.)

 

Overpowering is based on the idea that, by using more powerful amps, you can run them at lower volume to get the same sound. This in turn lets the amp have more headroom, resulting in less distortion from the amp. Distortion from the amp is bad for speakers, and should be avoided.

 

The logic behind this is that music can be very peaky, with peaks of more than 10dB possible. There are theorists that believe that there are transient peaks that are extremely short but also extremely high (in dB) that won't register on any kind of normal meters.

 

When you have an amp running at 10% of it's output, you have plenty of headroom for those peaks, and should get a very clean signal. Theoretically, 10% of your amps RMS could match the RMS rating of your speaker, which could get you like a 10:1 ratio of power to speaker handling. I think most people shoot for a much lower ratio, though, maybe 2:1 or 4:1.

 

Underpowering your cab causes other issues, mostly harmonic distortion caused by pushing the amplifier (to make enough sound) you eat up it's available headroom, and get distortion on the fundamental notes, as well as in any harmonic content of the signal. As I said before, amp distortion is bad for the speakers.

[mike fitzwell]

Use your ears: if the cabinet starts to make strange noises, turn the amp down or at least roll off the bass. It's one solution that works for any amp & cab combination. Remember--the numbers are just a guideline.

[xOriginalNinjax]

so I was wrong...dang...that sucks...oh well. But say, running 2 cabs, one rated 700w the other 1000w @ 4 ohm, and running 1000w through em at 4ohm, that's not gonna kill anything right? Cuz at that much power you're not gonna really need to dime it anyway...but that's fine right?

 

and since I don't hear any distorting or farting from my speakers..I'll assume it's fine...

[miles to go]

The important thing is to have enough power and enough speaker for the SITUATION. As long as you do, and you run everything cleanly, you'll be fine.

 

As TheLurker stated, the problem arises when you run out of power and drive your amp into clipping. This actually causes the signal to peak at higher than rated power, possibly damaging the speakers.

[Narcosynthesis]

I always thought it was to choos an amp with enough available power and headroom for your uses (so enough to get a great clean sound with preferrably some headroom to spare), then a cab with a higher rating than your amp so that it can easily cope with any transients or a volume war with the guitard

 

You could run a cab with lower rating than your amp, but I would always be worried that you might end up pushing it a bit too far someday and damaging the cab, if it was higher rated it could cope with anything your amp could throw at it (even if you are only using it at 10% of its capacity)

 

David

[Craig Vecchione]

It's really simple....if you apply more power than the speaker can handle, it will fail.

 

A 100w amp can deliver much more power if it's overdriven...perhaps as much as double the rated power. So you match this to a 75w speaker, following the "don't underpower" rule. You push the amp hard, and the 75w speaker sees 150w or more. Even with instrument service which isn't continuous, that's more than the speaker can handle for very long, and it will fail.

 

If you match that 100w amp to a 200w cabinet, how will you damage the speaker? Even pushed as hard as possible, you won't apply more than the speaker's rating. It'll last much longer and work just as well.

[i_wanna_les_paul]

 

Originally posted by Craigv If you match that 100w amp to a 200w cabinet, how will you damage the speaker? Even pushed as hard as possible, you won't apply more than the speaker's rating. It'll last much longer and work just as well.

 

 

This idea is something that I've seen mentioned as a real concern in the audiophile realms. The idea is that if you're pushing an amp to hard it'll clip with square waves. Supposedly, the more-fragile tweeter voice coils might not be able to handle the square waves and it could possibly fry.

 

Some dispute this, however. As bass players, we're messing with woofers which are much more robust.

 

I'd rather have more amp than speaker handling. In the end, if it's getting the job done, it's fine. If you're farting out, upgrade.

 

Dustin

[Craig Vecchione]

 

Originally posted by i_wanna_les_paul This idea is something that I've seen mentioned as a real concern in the audiophile realms. The idea is that if you're pushing an amp to hard it'll clip with square waves. Supposedly, the more-fragile tweeter voice coils might not be able to handle the square waves and it could possibly fry. Some dispute this, however. As bass players, we're messing with woofers which are much more robust. I'd rather have more amp than speaker handling. In the end, if it's getting the job done, it's fine. If you're farting out, upgrade. Dustin

 

 

A clipped signal is not a quare wave. And square waves are fine too, as long as the continuous average power they contain is less than the speaker rating.

[walkerci]

My take on this is that you want your power amp section to have lots of headroom so it doesn't clip.

 

IMHO, you don't want to dime the Master with a non-tube power amp.

 

So I am buying the argument that your amp should be rated at least as much as the continuous power rating of the biggest speaker load you intend to run.

 

I am also buying the argument that to increase your volume, you need lots of speaker surface area.

[Craig Vecchione]

 

Originally posted by walkerci My take on this is that you want your power amp section to have lots of headroom so it doesn't clip. IMHO, you don't want to dime the Master with a non-tube power amp. So I am buying the argument that your amp should be rated at least as much as the continuous power rating of the biggest speaker load you intend to run. I am also buying the argument that to increase your volume, you need lots of speaker surface area.

 

 

You're almost there. It's a package deal...you need sufficient power to avoid clipping, but you also need sufficient speaker to deliver that power safely.

[xOriginalNinjax]

 

Originally posted by Craigv You're almost there. It's a package deal...you need sufficient power to avoid clipping, but you also need sufficient speaker to deliver that power safely.

 

 

 

Then from what you all do say, I'm right and wrong and that my setup is fine. At 3/4 on master and 1/2 gain I can run enough volume to overpower two 150w tube guitar amps near dimed and a VERY loud drummer, as well as keep up with a 4700w PA system, without any distortion or breakup or excessive cone excursion. One MORE question I do have though is since I daisy chain my cabs, is it better to run the first cable to my Ampeg, since it's rated at 1000w @ 4 ohm, and then chain it to my Fender since the Fender is 700w @ 4 ohm? I was thinking it was safer, since the Ampeg could handle all 1000w if something were to happen to the Fender, or if the cable were to short out or something. Maybe I'm wrong though...eh, who knows?

[BassDemon]

Every amp I've every used (whether bass head or PA) has had a clip limiter.

 

Clipping really should not be such a concern.

 

If you are lighting the clip lights and still aren't loud enough then more power is not going to do much for you, you need more speakers first, more power second.

 

If a cab is rated for 500w RMS then it will most likely work just fine with a 200w head and an 800w head.

 

However - you run more risk of damaging the drivers by overpowering them.

 

Given the multitude of rating systems plus the marketing trend of overstating power handling I'd always err on the side of caution.

 

If a cab is rated for 500w then try and stay close to that rating.

[misterhinkydink]

Originally posted by xOriginalNinjax so I was wrong...dang...that sucks...oh well. But say, running 2 cabs, one rated 700w the other 1000w @ 4 ohm, and running 1000w through em at 4ohm, that's not gonna kill anything right? Cuz at that much power you're not gonna really need to dime it anyway...but that's fine right? and since I don't hear any distorting or farting from my speakers..I'll assume it's fine...

 

No, you were correct. The GC dweeb obviously slept through most of that class.

[Funkee1]

Originally posted by xOriginalNinjax so I was wrong...dang...that sucks...oh well. But say, running 2 cabs, one rated 700w the other 1000w @ 4 ohm, and running 1000w through em at 4ohm, that's not gonna kill anything right? Cuz at that much power you're not gonna really need to dime it anyway...but that's fine right? and since I don't hear any distorting or farting from my speakers..I'll assume it's fine...

 

As long as both are the same impedance (ohms) you're ok. In fact, it's even Ok to mismatch the impedances, as long as you don't go lower than the amps capabilities!

 

Wanna know the sad secret? In most cases, the power rating of the speaker is a made up number anyway.

[walkerci]

Originally posted by Craigv You're almost there. It's a package deal...you need sufficient power to avoid clipping, but you also need sufficient speaker to deliver that power safely.

 

Craig, thanks for the advice on the Putnam hitch for my E350!

 

We got everything from NJ to Florida successfully!

 

If you are ever in Orlando, PM me.

[SB]

I found that I get the least clipping when I turn the master on full and adjust the volume with the gain control. It seems that the less gain I have, the more clean, dynamic and responsive the amp gets! Could just be my amp though....

[walkerci]

 

Originally posted by xOriginalNinjax Then from what you all do say, I'm right and wrong and that my setup is fine. At 3/4 on master and 1/2 gain I can run enough volume to overpower two 150w tube guitar amps near dimed and a VERY loud drummer, as well as keep up with a 4700w PA system, without any distortion or breakup or excessive cone excursion. One MORE question I do have though is since I daisy chain my cabs, is it better to run the first cable to my Ampeg, since it's rated at 1000w @ 4 ohm, and then chain it to my Fender since the Fender is 700w @ 4 ohm? I was thinking it was safer, since the Ampeg could handle all 1000w if something were to happen to the Fender, or if the cable were to short out or something. Maybe I'm wrong though...eh, who knows?

 

 

If something shorts anywhere in the signal chain, you are going to have a problem. Short = path of least resistance. Literally.

Guess where all the amperage is going?

 

I use only 4 X 13 gauge cables and Neutriks to connect my cabs. All other things being equal, I want the cabinet with the highest load to use the shortest and largest cable to the amp.

 

I haven't checked this, but I believe my cabs are ranked in this order by load: 215, 212, 410, 115. The middle two are probably so close as to be interchangeable.

 

That said, if you are daisy chaining your cabs with different connector and cable types, you want the cable with the largest conductors (cable gauge) and the largest connector contact area (Neutriks) first in the chain because they will have to carry the highest load. This should reduce the amount of signal turned into heat and increase the amount of signal getting to your drivers.

 

Regarding the head settings...

 

I have a tube pre-amp with solid state power amp section.

I like to dime the pre-amp to bring out the tubiness.

 

It's pretty easy to add Neutriks to a cab.

Amps are to much effort to add Neutriks (not enough real estate)and an amp without Neutriks probably doesn't put out enough current to make it worthwhile anyway.

[NineMinuteNap]

 

Originally posted by xOriginalNinjax Then from what you all do say, I'm right and wrong and that my setup is fine. At 3/4 on master and 1/2 gain I can run enough volume to overpower two 150w tube guitar amps near dimed and a VERY loud drummer, as well as keep up with a 4700w PA system, without any distortion or breakup or excessive cone excursion. One MORE question I do have though is since I daisy chain my cabs, is it better to run the first cable to my Ampeg, since it's rated at 1000w @ 4 ohm, and then chain it to my Fender since the Fender is 700w @ 4 ohm? I was thinking it was safer, since the Ampeg could handle all 1000w if something were to happen to the Fender, or if the cable were to short out or something. Maybe I'm wrong though...eh, who knows?

 

 

When you daisychain cabinets, it doesn't make any difference which one you connect first. Daisychaining connects your cabinets in parallel, so both cabs receive the same signal from your amp.

 

I'm assuming the amp you're talking about is the Ampeg B4R in your sig, and both your cabs are 4 ohms each.

 

How do you have your cabs connected to your amp? Are you running it bridged mono, or using only 1 of the 2 channels?

 

Placing two 4 ohm loads in parallel results in an overall impedance of 2 ohms.

 

If bridged mono, you're running at less than your amps rated minimum impedance, and probably pumping a good deal more than 1000 watts through your cabinets. If using one side of your amp, you're only sending 500 watts through your cabs (250 watts to each one).

 

If it's the first case, you're more likely to damage your amp than your speakers. If it's the second case, you aren't getting the most "bang for the buck" out of your setup.

 

If the cable between cabinets develops an open (or gets disconnected), the load seen by the amp drops in half, cutting the power received by the remaining cab. If it shorts, your amp will see a zero (or near zero) ohm load, regardless of which cabinet is connected first, so damage may or may not occur however you have things connected.

[walkerci]

Well, kind of. Except that cable has resistance and that resistance is a function of length and diameter amongst other factors and then there is connector surface area to consider.

 

So assuming that all your cabs are chained in parallel...

 

In a high power situation, you would want the cabs drawing the most current on the shortest and fattest cables to the amp.

 

At the end of the day, the reason for having larger gauge cables is to reduce resistance for higher powered loads. We want that power turned into mechanical force moving a speaker cone, not turned into heat.

 

Meh, there are probably better people to explain than I.

It's time to hit the sack.

 

[xOriginalNinjax]

Ok, here's how everything's setup...

 

I have a Furman Power Conditioner that my head and only my head goes to.

 

I have my head run mono-bridged full range, not biamped, with a banana cable, because it doesn't have the Speakon capability. That cable is, I want to say, either 12 or 10 gauge. Fairly hefty but soon to be replaced by a matching Monster banana-1/4" to match the other Monster.

 

I run that to my Ampeg SVT410HEN which is 500w at 8 ohm, 1000w at 4ohm capable. I use a 1/4" jack on the cab side, because that's all they had for use with a banana.

 

I run my Monster Cable 1000 series 1/4"-1/4" cable out of the Ampeg into my Fender Bassman 410 which is 350w at 8 ohm, and 700w at 4 ohm.

 

Both cabs are 8 ohm standard, so in parallel they're a 4 ohm unit, and thus running my head at 1000w.

 

Both cables are 6 feet btw too. And I believe they're both the same gauge, if not, they're soon to be.

[walkerci]

Pretty hefty stuff.

 

So if you like the sound and it's reliable, then you're done!

 

Everything else is theory and real life trumps theory.

 

If it works for you, leave well enough alone.

[Craig Vecchione]

Originally posted by walkerci Craig, thanks for the advice on the Putnam hitch for my E350! We got everything from NJ to Florida successfully! If you are ever in Orlando, PM me.

 

Wow, that was a while ago wasn't it? Glad it all worked out!

[Craig Vecchione]

 

Originally posted by misterhinkydink No, you were correct. The GC dweeb obviously slept through most of that class.

 

 

He may actually have been awake and taking notes. GC and MF have some f'd up advice on their websites that supports his erroneous notions. There was some discussion/mocking of this a few months ago in the Live Sound forum, but I can't find that thread to post the link.