Responsible use of amp power

[Wasnex]

So I’m hearing you say (not putting words in your mouth) that a 500 Watt Fender Rumble solid state amp matched with a cabine bearing a 225 Watt Eminence 15 Speaker is the right match without overdrive and a volume set reasonably low - maybe 4 or 5 on a scale of 10?

I'll say it again. The amp settings don't tell you how much power the amp is making. Many amps reach their max clean power at 4 or 5 out of 10. In addition to how the controls are scaled on your amp, the power level varies with how hot of a signal your bass sends to the amp, and how hard you play.

IMHO, a 500 Watt rumble could easily destroy the 225W speaker if you crank up the lows. There is no easy answer because there are a lot of different interrelated variables that have to be considered. If you want an absolute answer, you need to model the speaker in the cab, find the excursion limits, determine what the lowest frequency you will play, and then keep the power at the lowest frequency under the level where the driver exceeds it's excursion limits.

One way to protect the speaker is insert a limiter in the signal path and then calibrate the limiter to engage when the amp is asked to produce too much wattage. The way this is done is you find the minimum impedance of the speaker and use the figure to calculate the voltage that will produce the wattageyou want to limit the amp at. Send a signal through the amp and measure the output with a voltmeter. Then dial back the limiter threshold until the output of the amp is at the desired voltage.

The speaker will still be exposed to a short transient that exceeds the limiter threshold because it takes a split second for an analog limiter to engage. Some speaker controllers use the inherent delay in digital processing to look ahead, so essentially the limiter can lock down the outputs before an overload occurs.

 

[pcake]

So I’m hearing you say (not putting words in your mouth) that a 500 Watt Fender Rumble solid state amp matched with a cabine bearing a 225 Watt Eminence 15 Speaker is the right match without overdrive and a volume set reasonably low - maybe 4 or 5 on a scale of 10?

https://www.sweetwater.com/store/de...2x10-inch-700-watt-bass-cabinet-silver-grille, you're looking for a simple answer where there is none.

you can fry a cab easily if you play hard with lots of distortion or lots of lows or mids. for that matter, lots of drive can change things, too. the settings you show would work as long as you don't do anything crazy, but playing with serious attack and heavy mids or some effects could make that risky.

i wouldn't use a 225 cab with that head at all. i'd replace that 225 watt cab with one of these
Robby Sturgis (there's also a version with a black grill). will it hold up to everything you can do to it with a 500 watt rumble head? probably not, but it will handle a lot more, and that's a good start.

a friend of mine - let's call him chris because that's his name - is a bass player. his rig was 300 watts, and it served him well. then he played with my future husband, who at that time played rehearsals and jams at full punk rock / death metal concert hall volume. chris tried to keep up, but instead of saying "hey, dude, you need to turn down", he tried to turn up to get over the mighty 100 watt ampeg V4. the bass was never audible, but he destroyed pretty much everything - his head as well as his cab.

i mention this because since you're new to separate components, not only do you always want headroom when possible, but you want a speaker that can handle more just in case. especially if you're unsure if your ears can tell you when something is wrong.

and please re-read Wasnex's post until you understand it. ask about the parts you don't understand or google them.

I'll say it again. The amp settings don't tell you how much power the amp is making. Many amps reach their max clean power at 4 or 5 out of 10. In addition to how the controls are scaled on your amp, the power level varies with how hot of a signal your bass sends to the amp, and how hard you play.

IMHO, a 500 Watt rumble could easily destroy the 225W speaker if you crank up the lows. There is no easy answer because there are a lot of different interrelated variables that have to be considered. If you want an absolute answer, you need to model the speaker in the cab, find the excursion limits, determine what the lowest frequency you will play, and then keep the power at the lowest frequency under the level where the driver exceeds it's excursion limits.

One way to protect the speaker is insert a limiter in the signal path and then calibrate the limiter to engage when the amp is asked to produce too much wattage. The way this is done is you find the minimum impedance of the speaker and use the figure to calculate the voltage that will produce the wattageyou want to limit the amp at. Send a signal through the amp and measure the output with a voltmeter. Then dial back the limiter threshold until the output of the amp is at the desired voltage.

The speaker will still be exposed to a short transient that exceeds the limiter threshold because it takes a split second for an analog limiter to engage. Some speaker controllers use the inherent delay in digital processing to look ahead, so essentially the limiter can lock down the outputs before an overload occurs.

 

[Downunderwonder]

You will feel the punch at more reasonable sound pressure levels,

you need to stop giving advice. To go from not feeling it to feeling it takes a jump in low end SPL.and a lot more power.

 

[projectapollo]

you need to stop giving advice. To go from not feeling it to feeling it takes a jump in low end SPL.and a lot more power.

No problem.

 

[ThisBass]

Everyone who has followed my posts know I really get into numbers, specs, etc. As far as this thread, however, "responsible use" is more subjective.

Yes, I used to be in a band that when we got a new piece of equipment that advertised (fill in the blank) capability, we pushed it until it either performed as advertised or broke in the warranty period, because we pushed hard on stage. Is that "responsible use"? Well, maybe. For example, we didn't purposely short out an amp with a two-ohm load, for example, but we would test the limits of its advertised capabilities.

Fast forward to present: 600 watts will fry a 225 watt speaker if pushed. That is because the speaker is being fed more power than its advertised power handling limits. In this particular case, "responsible" may mean are you listening closely to the speaker when it is getting towards its limits, with either heat, cone excursion, or audible raspiness or distortion, or extreme amp settings (bass control dimed out, for example).

There is an very interesting thing that happens along with different music genres.
Different music genres demand for different considerations how much amp power a cab system actually can handle.


So its an "engineering" consideration and responsibility rather than a "subjective" uncertainty.
Those folks who can't predict the demands in a more technical view may use common sense just to not overload the drivers over time.

 

[spentron]

There's 3 ways to make sure you don't exceed a power level other than the amp simply not being capable of it:
1. Learn the knob settings with a speaker that can take it and then switch (e.g reduce cabinets).
2. Use in a situation where it would simply be too loud to turn it up.
3. power meter

 

[iiipopes]

There is an very interesting thing that happens along with different music genres. Different music genres demand for different considerations how much amp power a cab system actually can handle.

So it's an "engineering" consideration and responsibility rather than a "subjective" uncertainty.
Those folks who can't predict the demands in a more technical view may use common sense just to not overload the drivers over time.

Forgive me, but your reply makes no sense. Yes, engineering changes as the demands of genres change. Jim Marshall is the primary example of that, taking the Fender Bassman circuit and hot rodding it. If we are talking about the same company designing the amp and the speaker cabs to work together, and working with the outside suppliers to make a system, then that makes sense. For example, Fender worked out of the RCA circuits book, and contracted with Jensen, Utah, CTS, etc., most famously JBL, for the speakers and designed the cabinets accordingly. Jim Marshall's work with Mullard and Celestion is legendary. But in today's world, there are so many manufacturers of equipment that unless you are devoted to a single manufacturer, everything is going to be "mismatched" "hit-and-miss" or whatever else you want to call it to some degree using one manufacturer's amplifier and another manufacturer's speaker cabinet. This destroys the objectivity of matching beyond looking at the numbers on the back panel or in the owners manual, and even then, depending on the different voicings different manufacturers give their amplifiers and speakers, that is no guarantee anything will truly work together. For example: many PA speakers have a built-in rolloff at @ 50Hz in order to truncate the bass response, driver excursion, and by extension, warranty claims from blown speakers. So your average PA cab with a 1X15, a tweeter, and possibly a midrange, will only make a mediocre bass cabinet, no matter how much power it is rated to handle. Because of all these variables, subjectivity in matching equipment and using equipment plays a larger role than in the past when, again for example, If you got an Ampeg SVT head, you got the matching 8X10" cabinet as just about the only cabinet that could handle the power with tone designed to make the most out of a Precision Bass.

 

[ThisBass]

Forgive me, but your reply makes no sense. Yes, engineering changes as the demands of genres change. Jim Marshall is the primary example of that, taking the Fender Bassman circuit and hot rodding it. If we are talking about the same company designing the amp and the speaker cabs to work together, and working with the outside suppliers to make a system, then that makes sense. For example, Fender worked out of the RCA circuits book, and contracted with Jensen, Utah, CTS, etc., most famously JBL, for the speakers and designed the cabinets accordingly. Jim Marshall's work with Mullard and Celestion is legendary. But in today's world, there are so many manufacturers of equipment that unless you are devoted to a single manufacturer, everything is going to be "mismatched" "hit-and-miss" or whatever else you want to call it to some degree using one manufacturer's amplifier and another manufacturer's speaker cabinet. This destroys the objectivity of matching beyond looking at the numbers on the back panel or in the owners manual, and even then, depending on the different voicings different manufacturers give their amplifiers and speakers, that is no guarantee anything will truly work together. For example: many PA speakers have a built-in rolloff at @ 50Hz in order to truncate the bass response, driver excursion, and by extension, warranty claims from blown speakers. So your average PA cab with a 1X15, a tweeter, and possibly a midrange, will only make a mediocre bass cabinet, no matter how much power it is rated to handle. Because of all these variables, subjectivity in matching equipment and using equipment plays a larger role than in the past when, again for example, If you got an Ampeg SVT head, you got the matching 8X10" cabinet as just about the only cabinet that could handle the power with tone designed to make the most out of a Precision Bass.

Honestly, I would not try to call on Jim Marshall or Leo Fender.
These guys desigend amps based on RCA schematic principles and it all happened at a time way back in the past when science of

system and information theory

just was at its beginnings.

I'd be very doubtful that Leo or Jim had ever sufficiant basic knowledgement to comprehent.

edit,
just for example I'm pretty sure that Jim and Leo (and you) didn't know that in the frequency domain there is lots of difference between a steady state sine wave and a sine burst.

 

[Wasnex]

Forgive me, but your reply makes no sense. Yes, engineering changes as the demands of genres change. Jim Marshall is the primary example of that, taking the Fender Bassman circuit and hot rodding it. If we are talking about the same company designing the amp and the speaker cabs to work together, and working with the outside suppliers to make a system, then that makes sense. For example, Fender worked out of the RCA circuits book, and contracted with Jensen, Utah, CTS, etc., most famously JBL, for the speakers and designed the cabinets accordingly. Jim Marshall's work with Mullard and Celestion is legendary. But in today's world, there are so many manufacturers of equipment that unless you are devoted to a single manufacturer, everything is going to be "mismatched" "hit-and-miss" or whatever else you want to call it to some degree using one manufacturer's amplifier and another manufacturer's speaker cabinet. This destroys the objectivity of matching beyond looking at the numbers on the back panel or in the owners manual, and even then, depending on the different voicings different manufacturers give their amplifiers and speakers, that is no guarantee anything will truly work together. For example: many PA speakers have a built-in rolloff at @ 50Hz in order to truncate the bass response, driver excursion, and by extension, warranty claims from blown speakers. So your average PA cab with a 1X15, a tweeter, and possibly a midrange, will only make a mediocre bass cabinet, no matter how much power it is rated to handle. Because of all these variables, subjectivity in matching equipment and using equipment plays a larger role than in the past when, again for example, If you got an Ampeg SVT head, you got the matching 8X10" cabinet as just about the only cabinet that could handle the power with tone designed to make the most out of a Precision Bass.

FYI, I thought the post made perfect sense, especially this line, "Different music genres demand for different considerations how much amp power a cab system actually can handle."

I believe @ThisBass 's native tongue is Deutsche, so try to read through the awkwardness of the language. FYI, he is a very capable engineer.

Here's what I think he means in simple terms: Some music is very bass heavy and some music is super compressed. Each of these characteristic would challenge a system that is pushed to it's limits in different ways. Of course there are other characteristics as well, but hopefully you get the idea.

For something that is more relatable, consider the tweeter in some bass cabs. They typically work fine for clean bass, but are prone to blowing if heavy distortion is run through them at relatively high SPL levels. The tweeter in a typical bass cab probably has about a 25W power rating, which is plenty for clean bass because the instrument does not generate a lot of content about 3.5khz. But distortion creates harmonics; essentially shifting power to higher frequencies. This can cause the tweeter to receive more power than it is designed to handle...POOOF!

 

[Downunderwonder]

Distortion only came about because some guitarist simply HAD to be 10dB louder than than everyone and everything. Then EVERY guitarist HAD to be...

 

[iiipopes]

Honestly, I would not try to call on Jim Marshall or Leo Fender.
These guys desigend amps based on RCA schematic principles and it all happened at a time way back in the past when science of

system and information theory

just was at its beginnings.

I'd be very doubtful that Leo or Jim had ever sufficiant basic knowledgement to comprehent.

edit,
just for example I'm pretty sure that Jim and Leo (and you) didn't know that in the frequency domain there is lots of difference between a steady state sine wave and a sine burst.

Your comment insults the intelligence of Leo Fender and Jim Marshall. They knew more than we will ever know.

 

[iiipopes]

FYI, I thought the post made perfect sense, especially this line, "Different music genres demand for different considerations how much amp power a cab system actually can handle."

I believe @ThisBass 's native tongue is Deutsche, so try to read through the awkwardness of the language. FYI, he is a very capable engineer.

Here's what I think he means in simple terms: Some music is very bass heavy and some music is super compressed. Each of these characteristic would challenge a system that is pushed to it's limits in different ways. Of course there are other characteristics as well, but hopefully you get the idea.

For something that is more relatable, consider the tweeter in some bass cabs. They typically work fine for clean bass, but are prone to blowing if heavy distortion is run through them at relatively high SPL levels. The tweeter in a typical bass cab probably has about a 25W power rating, which is plenty for clean bass because the instrument does not generate a lot of content about 3.5khz. But distortion creates harmonics; essentially shifting power to higher frequencies. This can cause the tweeter to receive more power than it is designed to handle...POOOF!

If the cabinet has a proper crossover, it is usually the crossover that will take the current first and blow when overloaded.

Generally, over the past 45 years, I have used, abused, flown and blown all types of speaker cabinets, from paper cone Jensens to surrounds in home stereo speakers that were supposed to have a "lifetime warranty" but spontaneously deteriorated, having nothing to do with how much power they were being fed. I also do know what it is to drive different cabinets in different genres, having played all styles from Thursday night to Sunday morning. Right now, I am working on installing a new crossover in an SWR Triad - one of those cabinets which was advertised as "unblowable." Well, something let go in the crossover. I am just glad it was at a rehearsal and not a gig when the horn cut out and that unmistakable acrid aroma of fried electronic parts started to fill the rehearsal hall.

By the way, the clipping harmonics are odd order harmonics that result in essentially DC current feeding a coil, which can induce heat, which is a major factor other than exceeding the limits of a coil suspension in blowing a speaker.

 

[JimmyM]

Distortion only came about because some guitarist simply HAD to be 10dB louder than than everyone and everything. Then EVERY guitarist HAD to be...

The first recorded distortion was (so the story goes) Roy Buchanan, who accidentally poked a hole in a cone and played through it just to see what would happen. He liked it so much that he would slit speakers to get that sound. It took guitarists a little bit to realize they could get distortion by cranking the volume, too, but Roy's sound wasn't about volume back then.

 

[Downunderwonder]

The first recorded distortion was (so the story goes) Roy Buchanan, who accidentally poked a hole in a cone and played through it just to see what would happen. He liked it so much that he would slit speakers to get that sound. It took guitarists a little bit to realize they could get distortion by cranking the volume, too, but Roy's sound wasn't about volume back then.

Every day a school day!

 

[JimmyM]

If the cabinet has a proper crossover, it is usually the crossover that will take the current first and blow when overloaded.

Generally, over the past 45 years, I have used, abused, flown and blown all types of speaker cabinets, from paper cone Jensens to surrounds in home stereo speakers that were supposed to have a "lifetime warranty" but spontaneously deteriorated, having nothing to do with how much power they were being fed. I also do know what it is to drive different cabinets in different genres, having played all styles from Thursday night to Sunday morning. Right now, I am working on installing a new crossover in an SWR Triad - one of those cabinets which was advertised as "unblowable." Well, something let go in the crossover. I am just glad it was at a rehearsal and not a gig when the horn cut out and that unmistakable acrid aroma of fried electronic parts started to fill the rehearsal hall.

By the way, the clipping harmonics are odd order harmonics that result in essentially DC current feeding a coil, which can induce heat, which is a major factor other than exceeding the limits of a coil suspension in blowing a speaker.

Dang man! That's a lot! I've also been playing 45 years, and I've blown exactly one bass speaker in that time...the stocker from my little 25w 108 practice combo. I should have known better than to turn the bass knob all the way up and kick on a fuzz. Live and learn

 

[Wasnex]

If the cabinet has a proper crossover, it is usually the crossover that will take the current first and blow when overloaded.

Generally, over the past 45 years, I have used, abused, flown and blown all types of speaker cabinets, from paper cone Jensens to surrounds in home stereo speakers that were supposed to have a "lifetime warranty" but spontaneously deteriorated, having nothing to do with how much power they were being fed. I also do know what it is to drive different cabinets in different genres, having played all styles from Thursday night to Sunday morning. Right now, I am working on installing a new crossover in an SWR Triad - one of those cabinets which was advertised as "unblowable." Well, something let go in the crossover. I am just glad it was at a rehearsal and not a gig when the horn cut out and that unmistakable acrid aroma of fried electronic parts started to fill the rehearsal hall.

By the way, the clipping harmonics are odd order harmonics that result in essentially DC current feeding a coil, which can induce heat, which is a major factor other than exceeding the limits of a coil suspension in blowing a speaker.

Pretty sure the SWR Triad actually has a reputation for blowing drivers. I believe the problem is something like the 10" is run full range instead of being crossed as a mid range.

Edit: Triad Schematic Attached. Looks like the 10" has a 6dB HPF at around 40hz.

 

[Redbrangus]

The first recorded distortion was (so the story goes) Roy Buchanan, who accidentally poked a hole in a cone and played through it just to see what would happen. He liked it so much that he would slit speakers to get that sound. It took guitarists a little bit to realize they could get distortion by cranking the volume, too, but Roy's sound wasn't about volume back then.

I'd put this in the category of Urban Myth, Gee-tar Division. Long before Roy Buchanan was recording, there were plenty of old blues and R&B records where the guitar sound is characterized by an over-driven amp/speaker combination. Not to mention the distortion of the old tube-type mic pre's they were recording with. I think it would be hard to accurately place what the first recorded intentional guitar distortion was, but it's bound to predate Roy Buchanan, who didn't start recording until the late '50s, I don't think. IMHO, of course.

Edit: And not to slag Roy B... I was a big fan. I was the monitor engineer on those old Austin City Limits videos featuring Roy that now turn up on YouTube. From back in 1977...great show!

 

[iiipopes]

Pretty sure the SWR Triad actually has a reputation for blowing drivers. I believe the problem is something like the 10" is run full range instead of being crossed as a mid range.

Edit: Triad Schematic Attached. Looks like the 10" has a 6dB HPF at around 40hz.

Thanks. I downloaded the schematic, crossover specs, driver specs, and owner's leaflet years ago, and have been very careful to find a new crossover that is compatable. In my case, I am lucky. I have checked the drivers, and they all show good. In my cab it is the crossover, which you can see the burn traces along with that inimitable acrid aroma of burnt electronics.

 

[Wasnex]

Dang man! That's a lot! I've also been playing 45 years, and I've blown exactly one bass speaker in that time...the stocker from my little 25w 108 practice combo. I should have known better than to turn the bass knob all the way up and kick on a fuzz. Live and learn

I've been playing for almost as long, and I have also never blown a speaker in a bass amp. I did buy an intermittent bass speaker once at a going out of business sale that eventually stopped working. That was disappointing and frustrating.

I have also blown a couple of horn drivers on PAs. A few seconds of HF feedback is all it takes. Sometimes the feedback is supersonic or at the edge of perception so you barely hear it. But you can feel the pressure and there is a pop and then the pressure goes away.

In a biamped rig, if the LF and HF share a power amp, you may hear some power supply hum in the woofer as the HF amp hits the rails. Also I believe the pressure I felt was partly the woofer amp going into oscillation because I could see the grill moving and the amp showed a huge amount of power being developed. A couple of times I saved compressions drivers by recognizing the symptom and yelling at the audio tech to kill the send.

 

[el murdoque]

'Responsibly' is simple enough. It means that you know the weakest link in your chain and will not push the level past that links comfort zone.
When you have a head that does 350W and a speaker that is rated for 225, it's like having a car that can go 180, but sits on tires that are rated for 140. Your car will SAFELY do 140. There might be more in it, but that also might include a wheel flying off at speeds where that is not even remotely funny.

Both the rating on the head as well as the rating on the speaker are rough guidelines:
-There are companies known for writing more than twice of the actual continuous output on their amps.
-There are companies that understate that number, sometimes by a few hundred watts.
-Most speakers are rated for how much juice the voice coil can take before it melts - the speaker itself will usually not die the thermal death of a melted voice coil, but die a more violent mechanical death well before the coil melts.


So, in a nutshell:
Some amps have way more or way less power than advertised which is irrelevant because the figures that are printed on the cabs are no way near exact as well. You will have to use a combination of your ears and your common sense.