Does the same wattage sound different at 4 vs 8 ohms?

[DuluthDank]

With every other variable remaining the same.

 

[agedhorse]

A little different since the drivers will not have exactly the same performance at 4 ohms and 8 ohms. They may be pretty close but in general the 4 ohm driver will have a little lower sensitivity compared with the 8 ohm version.

 

[el murdoque]

A little different since the drivers will not have exactly the same performance at 4 ohms and 8 ohms. They may be pretty close but in general the 4 ohm driver will have a little lower sensitivity compared with the 8 ohm version.

But how would it sound when you whip up the following scenario:

Solid state amp, obviously 4 ohm capable. You hook up one cabinet with 8 ohm, and set the dials so that on your test tone, exactly 100W arrive at the cabinet input.

Then, you modify the setup by hooking up a second, identical 8 ohm cabinet, but this is acoustically completely isolated from your listening spot, and yet again, you set the dials that exactly 100W arrive at the cabinet input.

 

[fdeck]

But how would it sound when you whip up the following scenario:

Solid state amp, obviously 4 ohm capable. You hook up one cabinet with 8 ohm, and set the dials so that on your test tone, exactly 100W arrive at the cabinet input.

Then, you modify the setup by hooking up a second, identical 8 ohm cabinet, but this is acoustically completely isolated from your listening spot, and yet again, you set the dials that exactly 100W arrive at the cabinet input.

If two identical speakers receive identical waveforms, they will sound identical. But replacing an 8-Ohm driver with a 4-Ohm version of the "same" driver is not this scenario.

 

[Solipsistik]

4 ohm speakers can be more efficient at the same volume level, because they draw more current at a lower voltage. However, they may consume more total power when fully loaded compared to 8 ohm speakers. Generally speaking, a 4-ohm speaker can draw twice the power of an 8-ohm speaker when connected to the same amplifier, allowing it to potentially play louder, especially at a amplifier volume.

These days, the ratings of amps are often significantly higher in 4 ohm configurations than in 8 ohm configurations, because the amps are capable of delivering more current at 4 ohms. So the head does matter in this discussion.

Sound quality has a lot more to do with the cabinet and speaker design than the impedance.

One major reason why you may want 8 ohm cabinets/speakers is because it makes hooking two of them in parallel very easy, since most amplifiers support a 4 ohm load, and that's what you get when you connect two 8 ohm cabinets in parallel. 2 ohm heads are somewhat rarer, more expensive, and run hotter (meaning they need cooling and usually have fans).

 

[agedhorse]

4 ohm speakers can be more efficient at the same volume level, because they draw more current at a lower voltage. However, they may consume more total power when fully loaded compared to 8 ohm speakers. Generally speaking, a 4-ohm speaker can draw twice the power of an 8-ohm speaker when connected to the same amplifier, allowing it to potentially play louder, especially at a amplifier volume.

These days, the ratings of amps are often significantly higher in 4 ohm configurations than in 8 ohm configurations, because the amps are capable of delivering more current at 4 ohms. So the head does matter in this discussion.

Sound quality has a lot more to do with the cabinet and speaker design than the impedance.

One major reason why you may want 8 ohm cabinets/speakers is because it makes hooking two of them in parallel very easy, since most amplifiers support a 4 ohm load, and that's what you get when you connect two 8 ohm cabinets in parallel. 2 ohm heads are somewhat rarer, more expensive, and run hotter (meaning they need cooling and usually have fans).

That’s not the question that’s being asked.

Specifically, the question is about identical POWER, not what you are describing.

 

[Solipsistik]

That’s not the question that’s being asked.

Specifically, the question is about identical POWER, not what you are describing.

It does matter, because at the same wattage, there's more current flowing to a 4 ohm speaker set, and the speakers tend to be more efficient, which means more sound volume at the same volume settings, most noticeable at lower amplifier volume, in comparison.

 

[eniac]

Maybe it would help if the OP could describe what exactly he had in mind, or what he's trying to accomplish.

 

[DuluthDank]

Maybe it would help if the OP could describe what exactly he had in mind, or what he's trying to accomplish.

My favorite sounding amp is my Genz Benz Shuttle 3.0, but at 8 ohms it runs on the low end of the watts I'd want to gig with. I prefer to use a single cab that I can carry in one hand, and was looking at a particular cab that either comes in 8 or 4 ohm versions. Obviously the 4 ohm version would be a bit louder, but I was wondering about any additional tradeoffs in sound. 300 watts into a 210 or 212 is in line with what I'd want otherwise.

 

[Solipsistik]

Obviously the 4 ohm version would be a bit louder, but I was wondering about any additional tradeoffs in sound.

There will be no audible difference between the two in terms of sound quality at a given db volume, if they use similar hardware and design. The 4 ohm version will be a little "louder" at lower volume settings in particular (I suppose you could say it's less linear, in a way). If the cab and the amp are matched in power, there shouldn't be APPARENT volume difference at the high end, because even if the 4 ohm cab was twice as loud, that's only 3db, which you will barely register. It takes 7-9db for a person to really notice a substantial difference, believe it or not.

 

[agedhorse]

It does matter, because at the same wattage, there's more current flowing to a 4 ohm speaker set, and the speakers tend to be more efficient, which means more sound volume at the same volume settings, most noticeable at lower amplifier volume, in comparison.

No sir, that is not how it works.

Into 4 ohms, the current increases but the voltage decreases for the same power.

Using the same volume control position results in TWICE the power delivered to the 4 ohm load, which is why it’s been mentioned adjusting the control to achieve the same power.

 

[Solipsistik]

Using the same volume control position results in TWICE the power delivered to the 4 ohm load, which is why it’s been mentioned adjusting the control to achieve the same power.

You're literally saying the same thing, only in reverse. Good game.

 

[agedhorse]

There will be no audible difference between the two in terms of sound quality at a given db volume, if they use similar hardware and design. The 4 ohm version will be a little "louder" at lower volume settings in particular (I suppose you could say it's less linear, in a way). If the cab and the amp are matched in power, there shouldn't be APPARENT volume difference at the high end, because even if the 4 ohm cab was twice as loud, that's only 3db, which you will barely register. It takes 7-9db for a person to really notice a substantial difference, believe it or not.

No sir, this is not true either.

3dB is EASILY discernible by the average player, even 1dB difference can be heard by many players. 7-9dB is a MONSTROUS difference.

The 4 ohm load, made with single 4 ohm versus 8 ohm drivers may not be louder at the same power, or even double the power depending on the sensitivity of the drivers. Generally, 4 ohm drivers are LESS sensitive, which is the root of incorrect assumptions.

This is not true with multi-driver cabinets made up from 8 ohm drivers though, since the resulting 4 ohm total load’s sensitivity will retain the higher sensitivity of the 8 ohm drivers.

 

[agedhorse]

You're literally saying the same thing, only in reverse. Good game.

No sir, your are not reading my response correctly.

 

[Wasnex]

Into 4 ohms, the current increases but the voltage decreases for the same power.

Yep.

Let's calculate voltage and current for 4 and 8 ohms with the power set to 100W

Voltage

• 4 ohm = sq rt (100 x 4) = 20V
• 8 ohm = sq rt (100 x 8) = ~28.28V

Current

• 4 ohms = sq rt (100/4) = 5A
• 8 ohms = sq rt (100/8) = ~3.54A

Power

• 100W at 4 ohms is 20A x 5V
• 100W at 8 ohms is ~28.28V x ~3.54A = 100W

NOTE: I use "~" here to indicate the figure are rounded to the nearest 100s place.

 

[agedhorse]

My favorite sounding amp is my Genz Benz Shuttle 3.0, but at 8 ohms it runs on the low end of the watts I'd want to gig with. I prefer to use a single cab that I can carry in one hand, and was looking at a particular cab that either comes in 8 or 4 ohm versions. Obviously the 4 ohm version would be a bit louder, but I was wondering about any additional tradeoffs in sound. 300 watts into a 210 or 212 is in line with what I'd want otherwise.

Ok, you need to focus on the sensitivity of the cabinets you are considering, and calculate the SPL from the power into the specific load and the sensitivity.

A 4 ohm, two driver cabinet made up of 2 x 8 ohm drivers will usually be louder than a single driver 4 ohm cabinet got the reasons I mentioned earlier.

 

[DuluthDank]

Ok, you need to focus on the sensitivity of the cabinets you are considering, and calculate the SPL from the power into the specific load and the sensitivity.

A 4 ohm, two driver cabinet made up of 2 x 8 ohm drivers will usually be louder than a single driver 4 ohm cabinet got the reasons I mentioned earlier.

Sounds good, I might understand some of those words. Specifically I was looking at a Tecamp S210 4 ohm cab.

 

[agedhorse]

With a sensitivity of 101dB/1W/1M, this will be higher than ANY single 4 ohm driver cabinet I am aware of. I would expect the performance to be similar to that of the Shuttle 3.0-210T combo.

 

[Wasnex]

300 watts into a 210 or 212 is in line with what I'd want otherwise.

For calculated SPL, you need the sensitivity rating of the cabs you are considering stated at 1 Watt/1 meter and the power rating of the amp at 4 and 8 ohms.

If it's a tube amp with 4 and 8 ohm outputs, the power should be 300W at both 4 and 8 ohms. The decibel change from raising the power from 1 to 300W is 10Log(300/1) = 24.78dB

If the 210 is rated 97dB 1W/1m and the 210 is rated 100dB 1W/1m, you simply add these figure to 24.78dB

210 Calculated SPL at 300W = 97 + 24.78 = 121.78dB
212 Calculated SPL at 300W = 100 + 24.78 = 124.78dB

There is no standard for how sensitivity specs are developed. If the speakers are both from the same product line, the specs should use the same standard and give you an accurate idea for the relative volume of each cab. Specs for same company but a different product line may or may not use the same standard. Specs from different companies probably will not use exactly the same standard.

 

[agedhorse]

There is no standard for how sensitivity specs are developed. If the speakers are both from the same product line, the specs should use the same standard and give you an accurate idea for the relative volume of each cab. Specs for same company but a different product line may or may not use the same standard. Specs from different companies probably will not use exactly the same standard.

Correct.

I generally use a fairly conservative method of average SPL sensitivity, between 50Hz and 5kHz at 1 watt RMS into the nominal impedance, calculated into a 1/2-space anechoic acoustic environment. I have been doing it this way for ~30 years, so when comparing cabinets that I designed over that period, the conclusions will be based on the same methodology and be comparable.

Some manufacturers use peak sensitivity, peak voltage, 1/4-space, etc. to enhance the numbers and make the marketing folks like them better. This makes it almost impossible to directly compare unless you know the conditions that the specs. were developed.