What makes a bass amp?

[Stidder]

Haven't found a definitive answer to my question.

What makes a bass amp, specifically a combo, different from a guitar amp? Is it just a case of a different speaker or are there intrinsic differences in the wiring and/or other circuitry components?

 

[BadExample]

Your suggestions would barely touch the surface.

 

[two fingers]

Pretty much three biggies.

1) Beefier speaker.

2) The cabinet is tuned to bass frequencies. If you put a beefier speaker in an open-back cab (the kind quite often used for guitar) it will likely still sound like garbage. Bass frequencies rely on cabinet physics heavily. (Over simplified but true.)

3) In most cases, the frequency ranges of EQ knobs are "optimized" for bass. So, for instance, the bass knob on a guitar amp will cut and boost a higher frequency range than the bass knob on a bass combo. This requires different values of internal components.

The other factor that affects most bass amps is that they generally require more power to obtain the volume level needed for bass to compete with drums. But not every bass combo is designed for that so I left it out of the big three.

 

[soulman969]

Pretty much three biggies.

1) Beefier speaker.

2) The cabinet is tuned to bass frequencies. If you put a beefier speaker in an open-back cab (the kind quite often used for guitar) it will likely still sound like garbage. Bass frequencies rely on cabinet physics heavily. (Over simplified but true.)

3) In most cases, the frequency ranges of EQ knobs are "optimized" for bass. So, for instance, the bass knob on a guitar amp will cut and boost a higher frequency range than the bass knob on a bass combo. This requires different values of internal components.

The other factor that affects most bass amps is that they generally require more power to obtain the volume level needed for bass to compete with drums. But not every bass combo is designed for that so I left it out of the big three.

That pretty much covers it but essentially the power output of a bass amp needs to be much greater if it's to be used in band to gig with. Whereas a 40w guitar amp would be more than loud enough for most club gigging and suitable bass amp would typically have 5x to 10x that much power.

You might think of it as somewhat like comparing a sedan to a pickup truck. Each one is designed and optimized for a different role. Their speakers, cabs, circuit design, and EQ are much different. In addition playing a bass through a guitar combo at volume would likely damage the speaker.

 

[Jack]

Both guitar and bass combos are amps and speakers in boxes. As for what's different? Almost everything about the amps, the speakers, and the boxes.

 

[fdeck]

In strictly technical terms, going an octave lower requires the amp to move 4x as much air, in order to reach the same sound pressure. That's before considering the relative audibility of guitar and bass, and how they should sit in the mix.

As a result, bass speakers have to be designed for a tougher job, without becoming ridiculously large.

On the amp side, just look at what controls are offered by the mainstream gear makers. And listen to guitar and bass in typical recordings or live performances. That will tell you all you need to know.

 

[Drgonzonm]

....

As a result, bass speakers have to be designed for a tougher job, without becoming ridiculously large.
....

Class D amps have changed the question. Amps are capable of exceeding the frequency capablites Iof the speakers.
Historically guitar amps specifications are lower than bass amps. Dave Zimmerman of maven peele an electrical engineer makes that statement. Stating that bass amps need a greater frequency response than guitar amps.
I may be taking liberty with @fdeck comment that bass need larger speakers. I offer the Paul Jones combos that have multiple 5 inch speakers.
If one looks at the Ampeg 810 cabinet, lmo, the cabinet is a dinosaur. Frequency limited but still a huge favorite of many a bass player .
@agedhorse, has different opinion on whether the amount of iron in the output transformer affects bass frequency. There are enough variables in ot design, that some designs of bass OTs are smaller than some guitar OTs. The manufacturers of OT's hold their designs close to their chests. It would not surprise me that @agedhorse employer has bought some of their competitors amps and disected the different components. That would make both good engineering and business sense.
Under the assumption that you take an ot design and change the amount of iron, and nothing else, Then test for frequency. There are number of conditions necessary to meet the bass frequency response. Any company worth its salt will optimse their designs on their ots, it would not be surprising finding that a guitar ot and bass ot's are different designs.
If one is looking for an indication of frequency dependencies are se (single ended ) ots. You don't find many se bass amps. Ime, Some of the common se amps will not play bass at all.
If you seek tube se amplifiers that that handle bass frequencies, you need to look at the audiophile amps. Some the audiophile have OTs that handle double digit wattage.
I remember seeing a picture of an 85kg OT, that was designed to handle 15hz.

 

[agedhorse]

Class D amps have changed the question. Amps are capable of exceeding the frequency capablites Iof the speakers.

Incorrect, this happened decades before class d was much of a commercial product. Class D has nothing in the world to do with exceeding frequency capabilities of a speaker... just look at the Crown DC-300, was responsible for destroying plenty of bass drivers in its day.

Historically guitar amps specifications are lower than bass amps. Dave Zimmerman of maven peele an electrical engineer makes that statement. Stating that bass amps need a greater frequency response than guitar amps.

I disagree, guitar amps tend to focus (primarily) on what is happening from about 100Hz up to 10kHz and what happens when the signal overdrives various stages in the amp. Bass amps tend to focus (primarily) on 50Hz - 5kHz.

I may be taking liberty with @fdeck comment that bass need larger speakers. I offer the Paul Jones combos that have multiple 5 inch speakers.

I think you mean Phil Jones, and I'm going to defend Francis' comment because the entire point of using multiple 5" speakers is to increase radiating area and total displacement, you you are taking quite a liberty.

If one looks at the Ampeg 810 cabinet, lmo, the cabinet is a dinosaur. Frequency limited but still a huge favorite of many a bass player.

It is still popular because it does what it does very, very well. It represents an iconic tone family that is both important and still relevant in today's music.

@agedhorse, has different opinion on whether the amount of iron in the output transformer affects bass frequency. There are enough variables in ot design, that some designs of bass OTs are smaller than some guitar OTs. The manufacturers of OT's hold their designs close to their chests. It would not surprise me that @agedhorse employer has bought some of their competitors amps and disected the different components. That would make both good engineering and business sense.

Output transformer (and power transformer for that matter) design is a complicated topic, one that I have done quite a few times. Of course manufacturers protect their R&D interests as there are a lot of costs that go into developing something that pushes the boundaries of performance. While I didn't design the transformers in the Strategy and Prodigy, they too are very low size/weight for their power bandwidth at low frequencies. It would me a lot more accurate to say that a surprising number of our amps have been acquired and reverse engineered by competitors rather than the other way around. This has happened to some of my earlier (pre-Mesa) products as well. Copying somebody else's product rather than doing your own work is a bit distasteful to me, especially whey you are unable to do it on your own.

Under the assumption that you take an ot design and change the amount of iron, and nothing else, Then test for frequency. There are number of conditions necessary to meet the bass frequency response. Any company worth its salt will optimse their designs on their ots, it would not be surprising finding that a guitar ot and bass ot's are different designs.

Of course they will be different, not just for power and bandwidth, but for phase response, hysteresis, linearity, and how they respond under heavy output stage clipping. Also, rarely will you see an ultralinear connection in guitar amps but you do see in in bass amps.

If one is looking for an indication of frequency dependencies are se (single ended ) ots. You don't find many se bass amps. Ime, Some of the common se amps will not play bass at all.
If you seek tube se amplifiers that that handle bass frequencies, you need to look at the audiophile amps. Some the audiophile have OTs that handle double digit wattage.
I remember seeing a picture of an 85kg OT, that was designed to handle 15hz.

This is a bass guitar forum, not an audio-fool forum. None of this makes for a hill of beans here.

 

[Stumbo]

What's difference between an electric guitar and an electric bass?

 

[Downunderwonder]

Just don't ever be accused of playing bass like a guitarist.

 

[Drgonzonm]

Incorrect, this happened decades before class d was much of a commercial product. Class D has nothing in the world to do with exceeding frequency capabilities of a speaker... just look at the Crown DC-300, was responsible for destroying plenty of bass drivers in its day.



I disagree, guitar amps tend to focus (primarily) on what is happening from about 100Hz up to 10kHz and what happens when the signal overdrives various stages in the amp. Bass amps tend to focus (primarily) on 50Hz - 5kHz.



I think you mean Phil Jones, and I'm going to defend Francis' comment because the entire point of using multiple 5" speakers is to increase radiating area and total displacement, you you are taking quite a liberty.



It is still popular because it does what it does very, very well. It represents an iconic tone family that is both important and still relevant in today's music.

I never said class D amps are blowing up speakers. I just said class D amps have a better frequency response than available cabinets.
You can go back further than the crown dc300, to the fifties. By the way thanks for the info on the dc300. O riginally the fender bass man came with 15" speakers after a few failures fender went with 410 combos. It's my opinion that the 15" speakers failed when trying to amplify uprights. Technology has improved,
It apparent that you and Dave Zimmerman have different design philosophies. Your employer is happy with your philosophy. Maven peele is no longer in business, mesa is. I will defend your right to have a different opinion than mine.
I personally, find bass amps inadequate, that stems from my upright days. Theres more money designing amps for bass guitars than uprights.
If I am in the minority that ampegs 810 is a dinosaur, then so be it.
Regarding the pj 5" are tiny speakers i agree it takes roughly 4 5" speakers to replace a 10" speaker, 6 speakers to replace a 12", 9 for a 15", and 13 to replace an 18. However the 5 inch, has better high frequency response than 12s, the 15s and 18s.

 

[knumbskull]

There is no difference, it’s all a marketing scam.

 

[BadExample]

@agedhorse, has different opinion on whether the amount of iron in the output transformer affects bass frequency. There are enough variables in ot design, that some designs of bass OTs are smaller than some guitar OTs. The manufacturers of OT's hold their designs close to their chests. It would not surprise me that @agedhorse employer has bought some of their competitors amps and disected the different components. That would make both good engineering and business sense.
Under the assumption that you take an ot design and change the amount of iron, and nothing else, Then test for frequency. There are number of conditions necessary to meet the bass frequency response. Any company worth its salt will optimse their designs on their ots, it would not be surprising finding that a guitar ot and bass ot's are different designs.
If one is looking for an indication of frequency dependencies are se (single ended ) ots. You don't find many se bass amps. Ime, Some of the common se amps will not play bass at all.
If you seek tube se amplifiers that that handle bass frequencies, you need to look at the audiophile amps. Some the audiophile have OTs that handle double digit wattage.
I remember seeing a picture of an 85kg OT, that was designed to handle 15hz.

Let it rest, man. We already know you have your own opinion on OT's. Off Topic again and nothing less than harassing @agedhorse I'm not trying to be a moderator, or the thread police, but a third attempt at this topic would be very, very annoying. Your point of view is respected.

 

[byacey]

I never said class D amps are blowing up speakers. I just said class D amps have a better frequency response than available cabinets.

I personally, find bass amps inadequate, that stems from my upright days. Theres more money designing amps for bass guitars than uprights.
If I am in the minority that ampegs 810 is a dinosaur, then so be it.
Regarding the pj 5" are tiny speakers i agree it takes roughly 4 5" speakers to replace a 10" speaker, 6 speakers to replace a 12", 9 for a 15", and 13 to replace an 18. However the 5 inch, has better high frequency response than 12s, the 15s and 18s.

Many AB2 amps have frequency response that far exceeds what a class D will do, but that has nothing to do with the cabinets. How much upper frequency extension do you think a bass guitar cab requires?

Regarding the speaker sizes, your statement is very generalized. More important is the excursion and power limits of the individual drivers when you want to start comparing speakers and their capabilities for moving larger masses of air. Smaller size drivers may have better high frequency characteristics individually, but combining them into a cabinet with multiple drivers introduces phase issues as frequency goes up.

Class A single ended outputs were more or less relegated to bedside clock radios and simple phonograph record players. Any instance where more than 5 watts or so is required, class A is a poor choice of output topology.

 

[agedhorse]

I never said class D amps are blowing up speakers. I just said class D amps have a better frequency response than available cabinets.
You can go back further than the crown dc300, to the fifties. By the way thanks for the info on the dc300. O riginally the fender bass man came with 15" speakers after a few failures fender went with 410 combos. It's my opinion that the 15" speakers failed when trying to amplify uprights. Technology has improved,
It apparent that you and Dave Zimmerman have different design philosophies. Your employer is happy with your philosophy. Maven peele is no longer in business, mesa is. I will defend your right to have a different opinion than mine.
I personally, find bass amps inadequate, that stems from my upright days. Theres more money designing amps for bass guitars than uprights.
If I am in the minority that ampegs 810 is a dinosaur, then so be it.
Regarding the pj 5" are tiny speakers i agree it takes roughly 4 5" speakers to replace a 10" speaker, 6 speakers to replace a 12", 9 for a 15", and 13 to replace an 18. However the 5 inch, has better high frequency response than 12s, the 15s and 18s.

How does class D have a wider frequency response? The Crown DC-300 has a MUCH wider bandwidth, especially on the low end where with the proper jumper setting will amplify all the way to DC. This is the opposite of what you said.

There are plenty of bass amps that make outstanding upright amps. Maybe if you go back to the days of heavily voiced old tube (and solid state for that matter) amps, sure, but not with many of today's amps.

Multiple 5" speakers CAN have a better high frequency response, but can also have a very inconsistent radiation pattern and resulting in comb filtering at the higher frequencies. Not a problem for some players and a big problem for others.

 

[Drgonzonm]

Many AB2 amps have frequency response that far exceeds what a class D will do, but that has nothing to do with the cabinets. How much upper frequency extension do you think a bass guitar cab requires?

Regarding the speaker sizes, your statement is very generalized. More important is the excursion and power limits of the individual drivers when you want to start comparing speakers and their capabilities for moving larger masses of air. Smaller size drivers may have better high frequency characteristics individually, but combining them into a cabinet with multiple drivers introduces phase issues as frequency goes up.

Class A single ended outputs were more or less relegated to bedside clock radios and simple phonograph record players. Any instance where more than 5 watts or so is required, class A is a poor choice of output topology.

@agedhorse provided information, on a power amp whose frequency response is dc to 20khz, it's ab-b design. The amp is the crown dc300.
Regarding speakers, I have no idea what the t&s parameters of pj 5" speakers are, nor do I know the t&s parameters of my fender rumble amps. I can find and read the t&s parameters of a select speakers. Without decent information, it's almost impossible
I know of the design of some 80w triode tubes, expensive big boogers. The triodes are used in class a amps.

So if I am not interested in efficient amplification, class A is available. If I am interested in class B amps, there designs out there.
Your comments on phasing are true, but even the famous Ampeg 810 has it's phasing problems.
Dave Zimmerman' s design for bass amps is 25hz to 16khz. Now if i can find a one way speaker for that range, I'd be set.
To me guitar amps are crude amplifiers. Bass amp design approaches audiophile designs. But I am only one voice.

 

[byacey]

mispost

 

[byacey]

@agedhorse provided information, on a power amp whose frequency response is dc to 20khz, it's ab-b design. The amp is the crown dc300.
Regarding speakers, I have no idea what the t&s parameters of pj 5" speakers are, nor do I know the t&s parameters of my fender rumble amps. I can find and read the t&s parameters of a select speakers. Without decent information, it's almost impossible
I know of the design of some 80w triode tubes, expensive big boogers. The triodes are used in class a amps.

So if I am not interested in efficient amplification, class A is available. If I am interested in class B amps, there designs out there.
Your comments on phasing are true, but even the famous Ampeg 810 has it's phasing problems.
Dave Zimmerman' s design for bass amps is 25hz to 16khz. Now if i can find a one way speaker for that range, I'd be set.
To me guitar amps are crude amplifiers. Bass amp design approaches audiophile designs. But I am only one voice.

I'm not sure why you have a fixation with class A; class AB2 is much more efficient and offers far more power output potential.
I doubt anyone could hear the the difference between class A and AB2 in a blind listening test.

 

[Drgonzonm]

How does class D have a wider frequency response? The Crown DC-300 has a MUCH wider bandwidth, especially on the low end where with the proper jumper setting will amplify all the way to DC. This is the opposite of what you said.

There are plenty of bass amps that make outstanding upright amps. Maybe if you go back to the days of heavily voiced old tube (and solid state for that matter) amps, sure, but not with many of today's amps.

Multiple 5" speakers CAN have a better high frequency response, but can also have a very inconsistent radiation pattern and resulting in comb filtering at the higher frequencies. Not a problem for some players and a big problem for others.

In the realm of bass amps and guitar amps, the crown dc300 is an outlier. It was designed for other purposes. Fortunately for crown, not only did bass players like the power amp, but so did audiophiles.
Regarding frequency response, of the class D amps, that comment is in relationship to cone speakers. I can find car audio cone speakers which handle the range the b0 fundamental frequency, but to handle the range of a bass, I would probably have use a two way speaker cabinet.
I don't have a problem with the amps, it's the speakers

 

[agedhorse]

Most linear amps have a frequency response that extends well below 20Hz IF that's what the designer intends. In fact many topologies can in fact extend to D.C., but smart designers know that this is a very poor thing for audio power amps and high pass filter appropriately.

Car audio speakers like that do not have the sensitivity nor the high frequency response necessary in a bass guitar speaker.

You are barking up another obtuse tree.