Amp Power vs Speaker

[Clive Hugh]

I have a solid state amp that is 70 watts. It is used mainly for keyboards and I decided to put in a new speaker that could handle the lower end. I was advised that a Eminence 200 watt spkr would handle all I could throw at it and it does.
However it seems to lack volume, I can remember it being far louder. I am wondering if the speaker is too much for the amp and is draining too much power to drive it? It is a sealed and ported cab.
Any suggestions/solutions?

 

[Farview]

Speakers that can handle a lot of power tend to be stiffer and require a lot of power to move. Another thing that could be going on is; the speaker just sounds different. If it is more low-endy, it will sound quieter because midrange cuts better. If you have changed your EQ settings to accentuate the low end, you are eating up much more power than you might have in the past. 70 watts doen't move a lot of air.

 

[ggunn]

I have a solid state amp that is 70 watts. It is used mainly for keyboards and I decided to put in a new speaker that could handle the lower end. I was advised that a Eminence 200 watt spkr would handle all I could throw at it and it does.
However it seems to lack volume, I can remember it being far louder. I am wondering if the speaker is too much for the amp and is draining too much power to drive it? It is a sealed and ported cab.
Any suggestions/solutions?

If the replacement speaker is of higher impedance (like if you replaced an 8 ohm speaker with a 16), then the amp will deliver less power to it. It also may be that the new one is less efficient, which is sometimes true of higher wattage speakers.

 

[Clive Hugh]

Gordon and Jay,
The speaker is the same impedance, It definately does not have the same volume, I will replace it with a 75 watt one. Thanks for that.
Clive

 

[cubanorocker316]

its because your 200 watt speakers is trying to suck 200 watts from the amp, and thats not happening so it can only be as loud as the amp's wattage lets it.....

hope this helps

 

[ggunn]

its because your 200 watt speakers is trying to suck 200 watts from the amp, and thats not happening so it can only be as loud as the amp's wattage lets it.....

hope this helps

There's a couple of explanations which might explain it, but that isn't one of them, unless it's an odd way of saying that higher wattage rated speakers are often less efficient. Two different speakers with the same impedance will "suck" the same amount of power from an amp; it's just that some speakers turn more of that power into sound.

 

[Farview]

its because your 200 watt speakers is trying to suck 200 watts from the amp, and thats not happening so it can only be as loud as the amp's wattage lets it.....

hope this helps

Speakers don't 'suck' power out of an amp. The amp drives the speaker.
The amp does the pushing, the speaker can not pull.

 

[ggunn]

Speakers don't 'suck' power out of an amp. The amp drives the speaker.
The amp does the pushing, the speaker can not pull.

Not quite true, actually. An amp produces an AC voltage across the load, but the current drawn is inversely proportional to the magnitude of the load (I=V/R). The power goes up as the square of the current (P=I^2R=V^2/R). The lower the impedance, the greater the power; an 8 ohm speaker will draw approximately twice the power from an amp than will a 16 ohm speaker, assuming that the amp is not current limited.

Now, I know this is true for solid state PA amps; many of them will have printed on the back near the speaker terminals what power it will deliver into what loads, usually double the power for half the impedance. However, there may be some differences in a tube guitar amp which drives speakers through an output transformer (solid state amps usually pull the output directly from the output transistors) which would limit the current and reduce the output voltage for a lower impedance load.

But the OP said that the impedance of the new speaker was the same as for the old, so that's not a factor here.

 

[Zaphod B]

It may be due to the speakers having different SPL (Sound Pressure Level) ratings which is kind of measure of the efficiency of the speaker. These numbers should be included with the speakers specifications.

Bingo.

Assuming equal impedances, it's not the wattage rating but the efiiciency of the speaker in SPL that determines how loud the speaker will be.

That said, speakers with the same nominal impedance rating may exhibit very different impedances at varying frequencies, which will affect their outputs throughout the frequency range and "colors" their sound.

 

[Farview]

Not quite true, actually. An amp produces an AC voltage across the load, but the current drawn is inversely proportional to the magnitude of the load (I=V/R). The power goes up as the square of the current (P=I^2R=V^2/R). The lower the impedance, the greater the power; an 8 ohm speaker will draw approximately twice the power from an amp than will a 16 ohm speaker, assuming that the amp is not current limited.

Now, I know this is true for solid state PA amps; many of them will have printed on the back near the speaker terminals what power it will deliver into what loads, usually double the power for half the impedance. However, there may be some differences in a tube guitar amp which drives speakers through an output transformer (solid state amps usually pull the output directly from the output transistors) which would limit the current and reduce the output voltage for a lower impedance load.

But the OP said that the impedance of the new speaker was the same as for the old, so that's not a factor here.

The speaker still doesn't pull any power out of the amp. The different loads allows the amp to push more or less.

 

[ggunn]

The speaker still doesn't pull any power out of the amp. The different loads allows the amp to push more or less.

Semantics.

 

[Zaphod B]

Semantics.

Probably based on the the amp being an active device, and the speaker being passive.

But hook 'em together and they both become part of a network so I don't think it's worth quibbling over.

 

[ggunn]

Probably based on the the amp being an active device, and the speaker being passive.

But hook 'em together and they both become part of a network so I don't think it's worth quibbling over.

Right. When you break a light bulb, does the vacuum suck the air in, or does the positive pressure push its way in? Is that glass half empty or half full? What is the meaning of life? ;^)

 

[Zaphod B]

Right. When you break a light bulb, does the vacuum suck the air in, or does the positive pressure push its way in? Is that glass half empty or half full? What is the meaning of life? ;^)

That's what I'm talkin' about!

 

[bongolation]

Assuming the information we've been given is correct, this seems to be very clearly a case of a less efficient speaker (check SPL ratings) being used as a replacement.

Happens all the time, and the audible difference is very noticeable and very real.

 

[Farview]

Is that glass half empty or half full?

The glass is too big.

 

[boingoman]

Assuming the information we've been given is correct, this seems to be very clearly a case of a less efficient speaker (check SPL ratings) being used as a replacement.

Happens all the time, and the audible difference is very noticeable and very real.

Yep. If speaker A is 3db less efficient than B, A will need twice as much power to get as loud as B. If A is 6db less efficient, it will take four times as much power as B to get the same volume.

 

[Ed Dixon]

When it comes to speakers, there are a number of factors that affect the resulting volume. These include power handling, efficiency, impendence (ohms), preferred cabinet design, and frequency range.

The number of watts a speaker can handle is more a measure of power ability than volume. Running 100 watts into a 75 watt speaker will likely result in less than desirable sound, and perhaps speaker damage. A speaker than handles 200 watts may or may not be, on average, louder than a speaker that handles only 100 watts.

Speaker efficiency, usually referenced in Sound Pressure Level (SPL), is usually a better measure of expected volume. Most SPL measurements are done using a standardized sound input (usually white or pink noise) with 1 Watt of power and measures at 1M on axis with the speaker (and usually cabinet).

A typical speaker cabinet will have a SPL rating of perhaps 96db. However some may be lower, and some considerably higher. Note that the difference between two cabinets that rate 96 and 99db in SPL is a factor of two when it comes to power in watts.

Speaker impedance is also a factor as is cabinet design. Most amps will deliver more power to a 4 ohm speaker than to an 8 ohm speaker. Amp specs are the key thing here, and determine how the pair will perform. The amp drives the speaker, which provides the load. A 4 ohm load will tend to draw more power than an 8 ohm load. A 200 watt speaker does not want more power, it simply can handle more power if provided.

It’s also worthwhile to note that cabinet design is a factor in overall speaker performance. There are many types of cabinet design (open back, closed back, ported, etc). Given the same amp and speakers, the cabinet design can significantly affect the resulting sound. The same speaker may perform differently in different cabinet designs.

Frequency range is also a factor here. Most speakers do not have a flat response, but instead perform differently at different input frequencies. Some may accent the bass area where others midrange or higher frequencies. Matching speaker and cabinet design to the desired range is usually a good thing to consider.

As a number of others have already said, speaker efficiency is the most likely issue here. The owner already stated that the impedance was the same, and likely the same cabinet. He took one speaker out and put a different speaker in. He seemed to notice lower volume. My guess is that the original speaker has a noticeable higher SPL rating than the new higher power-handling speaker.

Ed