overpower or underpower, a hypothetical..

[NickyBass]

Most assuredly. The same would apply to a 1000 watt head into a 600 watt cab.

Thanks for the answer!!

You know, I've gigged for 15 years with a conservative amount of wattage (200-350 watts) and I've never had any issues. In the past few years, I've been looking at 600-1200 watt heads and I feel that---if I keep doing what I've been doing (using the old noggen as more than an anvil) I should be fine.

 

[billfitzmaurice]

But the scope doesn't lie.

Yes, it does. Square waves as seen on a scope do not exist anywhere else but on a scope. They are never manifested in loudspeakers. Audio engineers like Bob and acoustical engineers like myself are well aware of this fact. TV repairmen, and those who spent last night at a Holiday Inn Express, not so much.

 

[Richard Lindsey]

Hey Jimmy, Bob 'don't forget I work for QSC' says that is IMPOSSIBLE. You cannot possibly blow your 8x10 with only 60 watts. He states clearly and with all the authority and expertise of a man of his position that an amp completely overdriven can't put out more that 2x the rated power and overpowering is the ONLY way to blow a speaker, therefore; You and I and everyone else here that's blown a speaker or three that was rated far higher than the amp are all imagining it. Hope this helps clear up the issue.

You might want to search a few more of Bob's posts. IMO you don't quite understand what he is saying. He has explained, on numerous occasions, that there are two ways of blowing a speaker: thermal damage, and mechanical damage from overexcursion. Neither requires clipping, and both are species of overpowering. If you search out some of his comments, as well as those of billfitzmaurice, Jerrold Tiers, and others, you'll find some good explanations that may help clear things up. This stuff has been explained many times by people who know.

 

[aborgman]

Yes, it does. Square waves as seen on a scope do not exist anywhere else but on a scope. They are never manifested in loudspeakers. Audio engineers like Bob and acoustical engineers like myself are well aware of this fact. TV repairmen, and those who spent last night at a Holiday Inn Express, not so much.

Bingo.

Stick a laser displacement probe in front of that speaker you're feeding square waves and see what comes out of it... it won't be a square wave.

 

[JEDBass]

I'm wondering if this thread should be moved in the "Humor" section. I got a good laugh out of some of the posts here!

I guess here's my tale regarding all of this:

When I was young and stupid my first amp was a 40 watt Crate combo with a single 10". Sounded surprisingly decent at low volumes, and as soon as you brought it up past halfway with anything but flat EQ, you could hear something wasn't sounding good. So, I just didn't turn it up that high. Never blew the speaker. Of course, it was next to useless in a rock band situation, so i traded it in for an old Peavey Combo 300.

Again, at low volumes, it was ok, at least for my needs and budget, and loud enough for jamming/gigging. But with me still being young and dumb, I liked to play with the bass knob a bit, and didn't listen for the warning signs. What happened next? Blown driver. Granted, I don't know how badly the driver could have been abused before I got ahold of it, but I finished the job for sure!

Moved up to a Fender 300C. Figured it was better built and could handle some extra lows. At low/medium volumes, fine. But I didn't learn my lesson and didn't adjust my EQ as I cranked it. You can only guess what happened after that.

Simple lesson for me. Always listen, and always be mindful of tone controls (and especially graphic EQ's!). They can greatly affect how much power is really going into your speaker. The master volume setting can be somewhat low/medium, but if everything else is jacked, you're still running a risk of overpowering.

And as an end note....once I realized "how" to listen for possible issues, and was more careful about EQ'ing, I have not blown a driver since.

 

[Richard Lindsey]

Hi Richard, I did re- read all of Bob's posts in this thread and what I quoted above sure seems like his bottom line. His position;
An amp can at best ( worst) puts out 2x the rated power and only overpowering a speaker can blow it, therefore if you use an amp with 1/2 or less the rated power of the speakers, you could NEVER blow them. He speaks in scientific absolutes. He did mention using a high- pass filter to limit excursion which is great for sound reinforcement of course; who the %#@& has a high pass filter on their bass amp? Sheesh!
I take back my comment about square waves. I will say that the original question was essentially "is more power OK/ good" to have and I said 'Yes'. I like the sound of having more amp headroom than less.
I suppose we can expect a tutorial about the term 'headroom' now and how it probably doesn't even exist, etc., etc., blah, blah, blah.

Hi Vail, let me suggest that you search out some of the relevant comments in other, previously existing threads. (I'll warn you--there are a LOT.) You're looking only at one type of overpowering, and as I said there are two of relevance here. A search on "overexcursion" would probably be fruitful.

Agreed that more power is good. Headroom is real, but note that it doesn't have anything directly to do with the ratio between the amp's output rating and the cab's power handling rating. It has to do with the ratio between the power you have available and the power you need to do the particular job you're trying to do. IOW, it's situational.

 

[JEDBass]

Hi Richard, I did re- read all of He did mention using a high- pass filter to limit excursion which is great for sound reinforcement of course; who the %#@& has a high pass filter on their bass amp? Sheesh!

I'm sure Bob will want to speak for himself here, but if I interpreted what he said correctly, he's inferring to something more along the lines of a subsonic filter or something that maybe passes everything above somewhere around 30 Hz or so. The intent of that type of filter is to prevent the speaker from having to reproduce frequencies that the vast majority of us cannot hear, and reduce excess cone excursion that occurs when it tries to push those frequencies at high volume.

Also, remember that most filters out there don't stop all frequencies below the cutoff. They reduce them at a rate that is established during the filter design (the slope).

 

[bongomania]

Actually many, many bass amps include a high-pass filter, but it does not have any knob or label on the exterior--it's just a built-in function, always on. One of the reasons people blew so many speakers with SWR amps back in the day, and the reason they had a reputation for such deep lows, was because they removed the high-pass filter from their amp design.

 

[B-string]

I'm wondering if this thread should be moved in the "Humor" section. I got a good laugh out of some of the posts here!

I guess here's my tale regarding all of this:

When I was young and stupid my first amp was a 40 watt Crate combo with a single 10". Sounded surprisingly decent at low volumes, and as soon as you brought it up past halfway with anything but flat EQ, you could hear something wasn't sounding good. So, I just didn't turn it up that high. Never blew the speaker. Of course, it was next to useless in a rock band situation, so i traded it in for an old Peavey Combo 300.

Again, at low volumes, it was ok, at least for my needs and budget, and loud enough for jamming/gigging. But with me still being young and dumb, I liked to play with the bass knob a bit, and didn't listen for the warning signs. What happened next? Blown driver. Granted, I don't know how badly the driver could have been abused before I got ahold of it, but I finished the job for sure!

Moved up to a Fender 300C. Figured it was better built and could handle some extra lows. At low/medium volumes, fine. But I didn't learn my lesson and didn't adjust my EQ as I cranked it. You can only guess what happened after that.

Simple lesson for me. Always listen, and always be mindful of tone controls (and especially graphic EQ's!). They can greatly affect how much power is really going into your speaker. The master volume setting can be somewhat low/medium, but if everything else is jacked, you're still running a risk of overpowering.

And as an end note....once I realized "how" to listen for possible issues, and was more careful about EQ'ing, I have not blown a driver since.

Don't like paraphrasing BFM but, most speaker until very recently cannot handle much power at the very low frequencies. Either boosting lows or cranking the gain so all the percussive pops from your hitting the strings are to blame here. Good for you, you did learn how to listen to the speakers crys for mercy!

 

[JimmyM]

vail, i think i might have worded it confusingly...my 810 didn't blow with the b-15n dimed. also, you were talking about us blowing speakers...honestly, i've never blown a bass speaker in my life. once blew a small pa speaker, but only because i didn't read the back of the cab that said it was only good for 150w and i had 300w per side in my powered head and i used it

anyway, the folks for whom the 2x power vs. cab thing works are professionals like you, who have the good sense not to exceed what the cabs can take just because you have it on tap. every week on here, though, some kid who sees the 2x thing does it and posts about how quickly he blew his cab. it takes a goodly amount of both discipline and good sense not to blow your cabs with that much power on tap, and i can't in good conscience recommend it to newbies. you, otoh, can do whatever you want because you can handle the responsibility that comes with great power

 

[bongomania]

You and I and everyone else here that's blown a speaker or three that was rated far higher than the amp are all imagining it.

Just curious, but can you say for a fact that you have blown a speaker that was individually rated for say "X wattage", running an amp that puts out a max of less than "1/2 X" wattage into that load?

 

[rpsands]

Displacement limits trump thermal limits for bass, as has been said. But I'll make it simple-like:

Displacement limits are not just a function of a speaker either. Take a 3015LF, in a 6cf cabinet tuned to 100hz, give it 100 watts @ 30hz and see what happens.

 

[JimmyM]

btw, that's another point i missed before...cabs that have blown with 1/2 their rated power only gave you the power handling rating at which the voice coils burn up. but due to the cabs placing its own limitations on the speakers, and because the point where your speakers go into overexcursion is way lower than the point the voice coils fry, it's often very easy to blow up a cab with half its rated power.

EDIT: sorry, didn't notice this was covered before.

anyway, be happy you have a way better gig than most of us, bro, and don't take it personally

 

[jmac]

I have two questions.

1. If a person starts a new thread on a topic that has been discussed the person will be scolded for not first performing a search. If a person does a search finds an old thread and adds to it the person will be scolded for resurrecting a "zombie" thread. So what exactly is the message board etiquette?

2. If underpowering a cabinet isn't a big deal then why do companies like EAW, Bergantino, and Clair Brothers recommend supplying 1.5 to 2 times the rated power of the speaker enclosure?

 

[JimmyM]

I have two questions.

1. If a person starts a new thread on a topic that has been discussed the person will be scolded for not first performing a search. If a person does a search finds an old thread and adds to it the person will be scolded for resurrecting a "zombie" thread. So what exactly is the message board etiquette?

good question. i think it's a little douchey, too. but the fact remains that this topic is covered at the very least once a week, so i understand some folks' frustration with it. to me it's not a big deal...boards would have very little traffic if not for repeat questions.

2. If underpowering a cabinet isn't a big deal then why do companies like EAW, Bergantino, and Clair Brothers recommend supplying 1.5 to 2 times the rated power of the speaker enclosure?

if i had a dollar for every time i've read misinformation from a company that should know better, i'd have at least an extra hundy.

but bear in mind that they recommend having 1.5 to 2x the power to avoid clipping that can damage expensive high freq horns. nowhere in their literature do they recommend using all of it. pros know that...many bass players don't.

 

[wcriley]

Actually many, many bass amps include a high-pass filter, but it does not have any knob or label on the exterior--it's just a built-in function, always on.

Off topic, but doesn't the 4/5 "String" button on G-K amps shift the corner frequency for the high pass filter rather than "boost" the lows?

 

[rpsands]

that is my understanding, but the corner frequency is probably a lot more complicated than that. Most of the better amp companies (Gk, Genz) use a low shelving with compensating boost for the loss at the corner freq.

 

[jnewmark]

good question. i think it's a little douchey, too. but the fact remains that this topic is covered at the very least once a week, so i understand some folks' frustration with it. to me it's not a big deal...boards would have very little traffic if not for repeat questions.


.

" Douchey " ??

 

[JEDBass]

wc, I'm not sure if it does (I did own a 1001RB for a while though), but I am almost positive that the 800RB has a pretty aggressive (for lack of a better term) high-pass filter built into it's circuitry. The reason that amp is quite powerful despite its fairly moderate 300W rating may be attributed to the fact that very little of the amp's power is wasted on the ultra lows.

 

[bongomania]

Exactly--this is part of why some amps are known to be "loud for their wattage"--it's because they roll off ultra-lows that would eat up wattage without contributing to the "loudness".