More on amps and cabs power balance

[JustFunk]

I think the 112dB sensitivity rating was a typo -- the OP put it at 102 elsewhere in the post. That sounds about right.


Hmmm... I was checking G-K's web site, to confirm that the 1600-watt power handling spec actually was an RMS rating. They do say that, but when I checked out the data on the individual neo drivers, it said they were rated for 300-watts. I'm much better with music than math, but I'm pretty sure four 300-watt drivers only add up to 1200 watts total power handling. Not that it matters much; 4 x 300-watt drivers, driven with a 1000-watt amp. should be plenty for anyone, IMHO.

I am with you in that. Don’t know where they take from those +400 watts? Tweeter? But a 400 watts one?

 

[Wasnex]

The article seemed counterintuitive when first stating that you should be 4 times under the RMS power to avoid clipping, than to pair considering the Program power.

I didn't read the article but I suspect what this means is the average long term RMS power should be at least 6dB below the system's clipping point, rather than you should run an amp rated for 1/4 the RMS power rating of the cab. Keep in mind recordings are likely to be compressed, so running your rig 6dB below clipping is probably inadequate for live bass.

Some of the speaker endurance test are only 2 hours long. AFAIK the drivers are required to still be working after the test, but not necessarily be working to spec. So 2 hours exposed to program power and the drivers are degraded.

PA cab are often protected using a limiter. IMHO the highest I would set the limiter is about midway between the cabs RMS and Program ratings. Safer to limit to the RMS power rating.

But want to try a better exercise:

IMHO try figure out how much SPL you need. This takes time, experience, and a focus on details. Once you figure out your SPL target you buy a rig that exceeds your requirements by a reasonably margin.

My target seems to be a rig capable of at least 124dB calculated. That's not always loud enough, but I am only willing to turn up so much. My last touring rig was rated for 127dB. The power amp was rated 260W RMS and the Eden D210XLT cab was rated for 350W RMS with a 103dB 1W/1m sensitivity rating. Never pushed this rig to clipping.

It can be a good idea to build a modular rig if your volume requirements vary significantly. It's up to you to decide if spending the extra money would be worth it.

For the record I also had a D410XLT and another 260W. In general I did not feel it was worth the effort of using the bigger cab or using both. The D210XLT by itself could play louder than I was willing to play. I did sometimes use both cabs, but that was often to make someone else happy. For low volume requirements I had a second much smaller rig, a GK 700RB/112 combo.

 

[JustFunk]

I didn't read the article but I suspect what this means is the average long term RMS power should be at least 6dB below the system's clipping point, rather than you should run an amp rated for 1/4 the RMS power rating of the cab. Keep in mind recordings are likely to be compressed, so running your rig 6dB below clipping is probably inadequate for live bass.

Some of the speaker endurance test are only 2 hours long. AFAIK the drivers are required to still be working after the test, but not necessarily be working to spec. So 2 hours exposed to program power and the drivers are degraded.

PA cab are often protected using a limiter. IMHO the highest I would set the limiter is about midway between the cabs RMS and Program ratings. Safer to limit to the RMS power rating.


IMHO try figure out how much SPL you need. This takes time, experience, and a focus on details. Once you figure out your SPL target you buy a rig that exceeds your requirements by a reasonably margin.

My target seems to be a rig capable of at least 124dB calculated. That's not always loud enough, but I am only willing to turn up so much. My last touring rig was rated for 127dB. The power amp was rated 260W RMS and the Eden D210XLT cab was rated for 350W RMS with a 103dB 1W/1m sensitivity rating. Never pushed this rig to clipping.

It can be a good idea to build a modular rig if your volume requirements vary significantly. It's up to you to decide if spending the extra money would be worth it.

For the record I also had a D410XLT and another 260W. In general I did not feel it was worth the effort of using the bigger cab or using both. The D210XLT by itself could play louder than I was willing to play. I did sometimes use both cabs, but that was often to make someone else happy. For low volume requirements I had a second much smaller rig, a GK 700RB/112 combo.

thanks for this too. Well I am not free to assemble the rig. First reason is I have a budget, and have to try to get on modern staff leaving behind my old one, at the same time buying staff with the tone I like, at the same time being it loud enough for my needs, at the same time dealing with what I can find in Italy (not much as you may think if you are based in USA, for example no Bergantino here, only new staff from a German retailer but no used staff nowhere).

In addition to this, I have to deal with the fact that 90% of sellers don’t ship the item, and so it may be needed even 10-15 hours travelling to go trying and purchasing (depending on where they are based).

Not the easiest

 

[agedhorse]

I think the 112dB sensitivity rating was a typo -- the OP put it at 102 elsewhere in the post. That sounds about right.


Hmmm... I was checking G-K's web site, to confirm that the 1600-watt power handling spec actually was an RMS rating. They do say that, but when I checked out the data on the individual neo drivers, it said they were rated for 300-watts. I'm much better with music than math, but I'm pretty sure four 300-watt drivers only add up to 1200 watts total power handling. Not that it matters much; 4 x 300-watt drivers, driven with a 1000-watt amp. should be plenty for anyone, IMHO.

Your math matches my math.

 

[agedhorse]

In addition to this, I have to deal with the fact that 90% of sellers don’t ship the item, and so it may be needed even 10-15 hours travelling to go trying and purchasing (depending on where they are based).

Not the easiest

Why don't sellers ship? It's not like shipping is rocket science. Thomann certainly ships all over Europe. Where are you located?

 

[JustFunk]

Why don't sellers ship? It's not like shipping is rocket science. Thomann certainly ships all over Europe. Where are you located?

Talking about private sellers. Don’t know why they don’t ship but I can make some good bet: 1) it’s expensive (> 100 euros); 2) the pack has to be prepared and people are not willing to do that; 3) possible problems between seller and buyer in case of transport damages.

I am in Italy.

 

[agedhorse]

Ok, then maybe you need to consider some new gear that's more available?

 

[Derek Kay]

On my uninformed youthful exuberance I managed to blow speakers I could really afford to replace. I resolved to use double the wattage in speakers than my amp.produced (RMS).

A simple 'rule of thumb' that has proved useful, although over-driving preamps can still cause harm. Use your ears.

 

[JustFunk]

Ok, then maybe you need to consider some new gear that's more available?

I am trying to find a balance. For example, I got to see a mark bass vintage 1000 head, which seems to be pretty interesting, at like 950,00 new, or a ninja 1000 at 750,00 new, + a GK 412 neo 1600 watts at 600,00 used. So I am looking around…

If you have any suggestion feel free to PM me, I would appreciate

 

[Rip Van Dan]

Could you elaborate? Thx

Reading something about what you’re talking about, it seems that loudness human perception doesn’t equal effective loudness db increase. If the latter doubles every 10 db increase, then in my example, 512 watts given to a cab with a sensitivity of 100 db (reaching 130 db) is 32 times louder than one given 16 watts power (reaching 115 db), is not perceived 32 times louder, but “only “ 3.

A 3db increase in SPL is a doubling of energy - twice as loud. That's why it takes twice as many watts to boost the SPL by 3db. But we don't hear it that way. We hear it as louder but don't recognize it as twice as loud. The human ear is not perfect, not by a long shot. So we don't recognize that sound as being"twice as loud" until there is a 10db increase in the sound.

The other condition the human ear is lacking in, is in low level (quiet) playing. When playing music at a low volume, the human ear hears the mids just fine, but doesn't pick up either the bass or treble notes well. That's why stereo receivers always had that "loudness" button. When you push that in, it boosts the lows and the highs and scoops out the mids so you can enjoy an even balance in the music at low levels. At normally higher volumes you don't need it.

A lot of amps have shape switches or adjustable shape controls. That smiley face EQ graphic with the boost in the bass and treble and the scooped out mids in the middle usually sounds good at bedroom practice levels. HOWEVER if you run that same EQ shape live in a group at gig levels, you've just dialed yourself out of the mix. The Sonic space for a bass in a mix lies in the low-mids between about 200Hz and perhaps 600Hz. The Low Bass frequencies are owned by the kick drum and the guitar and keys own the high mids and highs. The bass player owns the low mids and with just a little boost there will get you great presence and definition in the mix. Goldilocks effect again here...boost the low-mids too much and your sound will honk at you. If you hear that just slowly turn the low mids down until it stops honking. I usually run my low-mids boost just up to 1:30 and that does it - doesn't take a lot. For a frequency choice, I like to boost my amps at 250Hz if I can address that frequency, otherwise I'll dial in a little boost at 500Hz. Recording in a pro studio, I will always put the boost at 500Hz. Just sounds GREAT! with my Jazz bass (has an all-maple neck and 70's era pickup spacing of 4" center to center). You might need more or less with your bass. Just let your ears guide you.

I don't have a lot of videos of my playing bass but I think this video defines what I mean by presence and definition. I'm playing in a 5-pc. group with bass, keys, drums, and two guitars. The song is the Jefferson Airplane's "Somebody to Love", which has a pretty active bass line. You don't just see me playing, you can hear every note I play. I'm very distinctly there but I'm not drowning anyone out with volume.

I'm playing through my Eden WT500/800 (400-watts rms per channel into 4Ω or bridged into 8Ω at 800-watts) with two Eden EX-112 cabs. One is plugged into each channel and both are 4Ω cabs (should have bought them in 8Ω). All my EQ settings are flat except for a boost to 1:30 in the low-mids at 250Hz. I'm playing my '82 Jazz with the controls dimed.

For those of you who have seen this video a number of times,..sorry 'bout that. But it does demonstrate what that little boost in the low-mids does for you. This is from a friend's iPhone, so it's not a great recording, but it works. The girl singing is our keys player on the opposite side of the stage. You can get a glimpse of her once in a while between my head and the back of the guitarist hat.

 

[JustFunk]

A 3db increase in SPL is a doubling of energy - twice as loud. That's why it takes twice as many watts to boost the SPL by 3db. But we don't hear it that way. We hear it as louder but don't recognize it as twice as loud. The human ear is not perfect, not by a long shot. So we don't recognize that sound as being"twice as loud" until there is a 10db increase in the sound.

The other condition the human ear is lacking in, is in low level (quiet) playing. When playing music at a low volume, the human ear hears the mids just fine, but doesn't pick up either the bass or treble notes well. That's why stereo receivers always had that "loudness" button. When you push that in, it boosts the lows and the highs and scoops out the mids so you can enjoy an even balance in the music at low levels. At normally higher volumes you don't need it.

A lot of amps have shape switches or adjustable shape controls. That smiley face EQ graphic with the boost in the bass and treble and the scooped out mids in the middle usually sounds good at bedroom practice levels. HOWEVER if you run that same EQ shape live in a group at gig levels, you've just dialed yourself out of the mix. The Sonic space for a bass in a mix lies in the low-mids between about 200Hz and perhaps 600Hz. The Low Bass frequencies are owned by the kick drum and the guitar and keys own the high mids and highs. The bass player owns the low mids and with just a little boost there will get you great presence and definition in the mix. Goldilocks effect again here...boost the low-mids too much and your sound will honk at you. If you hear that just slowly turn the low mids down until it stops honking. I usually run my low-mids boost just up to 1:30 and that does it - doesn't take a lot. For a frequency choice, I like to boost my amps at 250Hz if I can address that frequency, otherwise I'll dial in a little boost at 500Hz. Recording in a pro studio, I will always put the boost at 500Hz. Just sounds GREAT! with my Jazz bass (has an all-maple neck and 70's era pickup spacing of 4" center to center). You might need more or less with your bass. Just let your ears guide you.

I don't have a lot of videos of my playing bass but I think this video defines what I mean by presence and definition. I'm playing in a 5-pc. group with bass, keys, drums, and two guitars. The song is the Jefferson Airplane's "Somebody to Love", which has a pretty active bass line. You don't just see me playing, you can hear every note I play. I'm very distinctly there but I'm not drowning anyone out with volume.

I'm playing through my Eden WT500/800 (400-watts rms per channel into 4Ω or bridged into 8Ω at 800-watts) with two Eden EX-112 cabs. One is plugged into each channel and both are 4Ω cabs (should have bought them in 8Ω). All my EQ settings are flat except for a boost to 1:30 in the low-mids at 250Hz. I'm playing my '82 Jazz with the controls dimed.

For those of you who have seen this video a number of times,..sorry 'bout that. But it does demonstrate what that little boost in the low-mids does for you. This is from a friend's iPhone, so it's not a great recording, but it works. The girl singing is our keys player on the opposite side of the stage. You can get a glimpse of her once in a while between my head and the back of the guitarist hat.

Thanks! Now I am with my mobile only and no bass can be heard, but tomorrow will do with big pleasure and take note of your suggest for my next reharsal

 

[JimmyM]

A little OT from an absolute rookie in this field, but I got caught in this discussion which is interesting for me as well, as I’d like to buy a head and a couple of cabs.
Question is (forgive me, I know that I don’t know anything - I play with my iPhone and my basses only): two cabs are connected in parallel but in which way? The head needs to have to separate outputs?
In case it doesn’t, and they are required, is there a way to connect two cabs to a head supporting multiple load impedance values?
Again, forgive me for what you may think as being a super trivial question

No, the head doesn’t need separate outs. You can use them if it has them but isn’t required if at least one cab has two jacks.

And solid state heads detect the impedance. Many have a 4 ohm minimum, so with them you would want to run two 8 ohm cabs or a single 4 ohm, and not a combination of 4 and 8 ohm cabs, as that gets you 2.67 ohms and an unequal power distribution.

 

[JimChjones]

RMS power, program power, and peak RL unfurl="true"]https://carvinaudio.com/blogs/audio-education/demystifying-power-ratings-rms-vs-program-vs-peak[/URL]

This Carvin article seems to be written in the context of PA systems. That doesn't make it wrong, but it does mean it's not especially helpful when considering bass guitar rigs, which have rather different limitations.

I find the way people talk about clipping very confusing and peculiar. They talk about square waves and so on as if there were magic properties.

@agedhorse can correct me of course, but my understanding is much less complicated than people make out. Clipping is just distortion. An amplifier is rated at say 200W RMS at 1% distortion. AIUI if you drive it beyond that point then it will deliver more power in an increasingly distorted sound, and probably top out delivering something like 400W RMS of what would be quite unlistenably distorted sound in a PA situation, but might well be usable for say solo guitar.

Also the nature of the distortion is that the majority of the extra power will be delivered as artificially generated high frequencies. This is particularly relevant if tweeters are involved, because it means they cop the majority of the extra watts.

Talk about square waves is a major red herring. Just about every analogue synth can generate square waves, and they do no harm at all. If you put 200W RMS of square waves into a 300W rated speaker it will handle it just fine. What people confuse themselves with is that a heavily distorted and clipped sine wave superficially resembles a square wave. But what does the damage is not the shape of the waveform, but the extra watts.

 

[agedhorse]

This Carvin article seems to be written in the context of PA systems. That doesn't make it wrong, but it does mean it's not especially helpful when considering bass guitar rigs, which have rather different limitations.

I find the way people talk about clipping very confusing and peculiar. They talk about square waves and so on as if there were magic properties.

@agedhorse can correct me of course, but my understanding is much less complicated than people make out. Clipping is just distortion. An amplifier is rated at say 200W RMS at 1% distortion. AIUI if you drive it beyond that point then it will deliver more power in an increasingly distorted sound, and probably top out delivering something like 400W RMS of what would be quite unlistenably distorted sound in a PA situation, but might well be usable for say solo guitar.

Also the nature of the distortion is that the majority of the extra power will be delivered as artificially generated high frequencies. This is particularly relevant if tweeters are involved, because it means they cop the majority of the extra watts.

Talk about square waves is a major red herring. Just about every analogue synth can generate square waves, and they do no harm at all. If you put 200W RMS of square waves into a 300W rated speaker it will handle it just fine. What people confuse themselves with is that a heavily distorted and clipped sine wave superficially resembles a square wave. But what does the damage is not the shape of the waveform, but the extra watts.

For the most part correct, but what also happens when an amp is driven that hard is that the crest factor decreases to almost nothing. This increases the average power and thermal energy compared with a sine wave.

 

[HolmeBass]

Wow, the article says that safe from amp clipping is to consider 1/16 of the cab peek power (1/4 of the continuous, which is 1/8 of the Program, which is 1/16 of the peak).

BTW, the article then defines pairing amp and cab as considering the Program power, which I believe now is simply the RMS watts declared by manufacturers

I might have posted a bad article, although I don’t recall 1/16 or 1/8 being mentioned anywhere within that article.

My main point - again - is that program power is not the same as RMS power.

Just use RMS power and forget about program and peak power. I personally won’t use gear that sells itself via program or peak power unless it also includes an RMS power spec. It’s a sign of cheap beginner gear.

Although for home practice I am not all that choosy. That rule is for my gigging rig. That said for most rehearsals in my basement I do use my gigging rig.

 

[HolmeBass]

Whatever you hook to your amp, will receive an equal amount of power, if the resistance matches (8ohm + 8ohm).

You really need to just disregard the watt ratingson your cabinets. You are well under powered to be safe. Don't worry about that anymore. It has nothing to do with your amp at all.

The power is distributed evenly between the cabinets you have attached to it. The maximum power on the cabinet never changes, neither does the resistance. They are what they are. The power rating on your cabs mean absolutely nothing to your amp.

The power is only distributed evenly among the attached cabinets if they have the same impedance rating.

 

[JustFunk]

I might have posted a bad article, although I don’t recall 1/16 or 1/8 being mentioned anywhere within that article.

My main point - again - is that program power is not the same as RMS power.

Just use RMS power and forget about program and peak power. I personally won’t use gear that sells itself via program or peak power unless it also includes an RMS power spec. It’s a sign of cheap beginner gear.

Although for home practice I am not all that choosy. That rule is for my gigging rig. That said for most rehearsals in my basement I do use my gigging rig.

Not mentioned indeed, it’s derived.The article says for not clipping use 1/4 of the RMS power (which equals 1/8 of the Program and 1/16 of the peak).

 

[Fishheadjoe]

This thread hurts my head! If you're a newbie trying to learn, I'd advise that you seek out a different thread!
Fishheadjoe

 

[JustFunk]

Ahah why? It’s been so informative thanks to great pieces of info generously given by expert TBrs, and I believe I can do my math now

 

[Fishheadjoe]

https://www.talkbass.com/threads/amps-faq-info-on-ohms-allsize-rigs-overunderpowercabs-diy-techtalk-links.166225/

Fishheadjoe