Impedance Question

[Skribbles]

I just purchased a Yamaha RX V2500 receiver and am connecting a set (5) of speakers to it. The speakers are from a DVD Package (a temporary setup till I can buy a good set) and have a 4 Ohm impedance. My receiver can only be set to 6 or 8 ohm. Is this going to damage my speakers or receiver? Will the sound be horrible? I know that it won't be high quality by any means, but it should be better that just the TV.


Thanx very much.


Edit: I am a complete newb when it comes to stereos.

[thekid]

I just purchased a Yamaha RX V2500 receiver and am connecting a set (5) of speakers to it. The speakers are from a DVD Package (a temporary setup till I can buy a good set) and have a 4 Ohm impedance. My receiver can only be set to 6 or 8 ohm. Is this going to damage my speakers or receiver? Will the sound be horrible? I know that it won't be high quality by any means, but it should be better that just the TV.


Thanx very much.


Edit: I am a complete newb when it comes to stereos.

I am new myself but from what I understand by using the 4 ohm you will make your Yamaha work harder than it was designed and risk damaging the unit. Sound quality will probably diminished because of not getting enough power to the speakers but this I think will be the least of your worries. I think you need to find some other speakers that match what your Yamaha was designed to power.

[kexodusc]

I am new myself but from what I understand by using the 4 ohm you will make your Yamaha work harder than it was designed and risk damaging the unit. Sound quality will probably diminished because of not getting enough power to the speakers but this I think will be the least of your worries. I think you need to find some other speakers that match what your Yamaha was designed to power.

Actually, with lower impedance, the power to the speakers actually INCREASES. That's why it's hard on amplifier, the current draw is higher than the amp might be made for, and it works overtime. Speakers aren't 4 ohm for the whole range of frequencies, and I'm guessing here that the manufacturer conservatively rated these, most DVD or home theater packages are considerably higher in impedance.

Skribbles,
For your Yamaha, I wouldn't worry too much, I answered your post in the other thread, but just make sure you have the 6 ohm switch set, and if things start to sound bad, turn the volume back down.

[Geoffcin]

I just purchased a Yamaha RX V2500 receiver and am connecting a set (5) of speakers to it. The speakers are from a DVD Package (a temporary setup till I can buy a good set) and have a 4 Ohm impedance. My receiver can only be set to 6 or 8 ohm. Is this going to damage my speakers or receiver? Will the sound be horrible? I know that it won't be high quality by any means, but it should be better that just the TV.


Thanx very much.


Edit: I am a complete newb when it comes to stereos.

Yamaha uses a current limiting feature that makes it nearly impossible to overload them.
That being said, you could overheat one. Make sure that your receiver has good ventilation to avoid this.

[thekid]

Actually, with lower impedance, the power to the speakers actually INCREASES. That's why it's hard on amplifier, the current draw is higher than the amp might be made for, and it works overtime. Speakers aren't 4 ohm for the whole range of frequencies, and I'm guessing here that the manufacturer conservatively rated these, most DVD or home theater packages are considerably higher in impedance.

Skribbles,
For your Yamaha, I wouldn't worry too much, I answered your post in the other thread, but just make sure you have the 6 ohm switch set, and if things start to sound bad, turn the volume back down.

Kex
Thanks for the save.
I need to leave the technical stuff to the experts.
For my own education here would running your receiver with speakers with lower impededence than recommended cause any problems over the long run?

Also based on part of your answer; are speakers with lower impedence neccessarily more efficient speakers?

[kexodusc]

For my own education here would running your receiver with speakers with lower impededence than recommended cause any problems over the long run?

This depends on the receiver and speaker (and impedance) in question. I wouldn't run a 20lbs, $200 receiver of any brand, Yamaha, Pioneer, Sony, etc, with 4 ohm speakers at high levels and expect to be fine.

We worry about current levels being delivered by the amplifier, whether the power supply unit can keep up, how much energy the caps can store and recharge, clipping etc. 8 ohm rated amplifiers can safely drive 4 ohm rated speakers at pretty low levels. For all intents and purposes, this would be no different than running an 8 ohm speaker at double the current level.

Volume and power are related logarithmically, which means that you soon have to use a ton of power to get a bit of extra loudness. This is where we run into problems. A +9 dB peak (not uncommon) could send the amp into clipping, overtax the power supply etc. Additionally, as Geoffcin alluded to, running a receiver at high current levels creates more heat, which can be bad if the unit can't dissipate fast enough.

Most efficient speakers, I'd say, 88 dB or better that are 4 ohm should be compatible with 8 ohm receivers of sufficient size (power). You just won't have as much maximum volume. In small/medium rooms this isn't too bad, in larger rooms it could be disastrous. And if you like your music loud, you'll want a better amp.

Other problem. Like I mentioned, impedance isn't constant at every frequency a speaker produces. It swings a lot. On 4 ohm speakers, I've seen the impedance as high as 30 ohms at higher frequencies and as low as 1.5 ohms in the midbass area. At 1.5 ohms, an amp will send over 5 times the amount of power as a speaker at 8 ohms. Suddenly your receiver with a max of 40 watts/channel when all channels are simultaneously driven can max out pretty fast at the 200 - 500 Hz range at even modest volumes.

If you have an idea of how loud (in dB) you listen, and knew the impedance minimum of your speakers, you could make a determination of appropriate minimum receiver size. Many people can't say for certain how loud they'll want their system to go for as long as they own it, and speaker companies don't tell you the impedance minimums (which really mean a lot more than the nominal 4 or 8 ohm ratings).



Also based on part of your answer; are speakers with lower impedence neccessarily more efficient speakers?
No. Not necessarily. If you use the 2.83 volts RMS figure for determining sensitivity/efficiency then the dB number will appear higher, but this is because you're actually feeding the 4 ohm speaker more watts than the 8 ohm speaker with the same 2.83 volts. If you use 1 watt @ 1 meter as the test for efficiency, then the impedance alone doesn't determine efficiency.

[zepman1]

I'd say you'll be OK. Set your receiver to the 6 ohm setting and you should be able to run them as loud as you want. Just monitor the heat produced by the amp at first to make sure it is OK. As mentioned, make sure there is adequate ventilation.

I've run 6 ohm speakers on an crappy 8 ohm amp now for over 3 years with no problems whatsoever and I listen at loud volumes. Sure it isn't ideal, but eventually I will be getting a new and better receiver anyhow.

[Skribbles]

Thanks very much guys, much appreciated. I've heard conflicting things about this but you guys have settled my worries.

[thekid]

This depends on the receiver and speaker (and impedance) in question. I wouldn't run a 20lbs, $200 receiver of any brand, Yamaha, Pioneer, Sony, etc, with 4 ohm speakers at high levels and expect to be fine.

We worry about current levels being delivered by the amplifier, whether the power supply unit can keep up, how much energy the caps can store and recharge, clipping etc. 8 ohm rated amplifiers can safely drive 4 ohm rated speakers at pretty low levels. For all intents and purposes, this would be no different than running an 8 ohm speaker at double the current level.

Volume and power are related logarithmically, which means that you soon have to use a ton of power to get a bit of extra loudness. This is where we run into problems. A +9 dB peak (not uncommon) could send the amp into clipping, overtax the power supply etc. Additionally, as Geoffcin alluded to, running a receiver at high current levels creates more heat, which can be bad if the unit can't dissipate fast enough.

Most efficient speakers, I'd say, 88 dB or better that are 4 ohm should be compatible with 8 ohm receivers of sufficient size (power). You just won't have as much maximum volume. In small/medium rooms this isn't too bad, in larger rooms it could be disastrous. And if you like your music loud, you'll want a better amp.

Other problem. Like I mentioned, impedance isn't constant at every frequency a speaker produces. It swings a lot. On 4 ohm speakers, I've seen the impedance as high as 30 ohms at higher frequencies and as low as 1.5 ohms in the midbass area. At 1.5 ohms, an amp will send over 5 times the amount of power as a speaker at 8 ohms. Suddenly your receiver with a max of 40 watts/channel when all channels are simultaneously driven can max out pretty fast at the 200 - 500 Hz range at even modest volumes.

If you have an idea of how loud (in dB) you listen, and knew the impedance minimum of your speakers, you could make a determination of appropriate minimum receiver size. Many people can't say for certain how loud they'll want their system to go for as long as they own it, and speaker companies don't tell you the impedance minimums (which really mean a lot more than the nominal 4 or 8 ohm ratings).


No. Not necessarily. If you use the 2.83 volts RMS figure for determining sensitivity/efficiency then the dB number will appear higher, but this is because you're actually feeding the 4 ohm speaker more watts than the 8 ohm speaker with the same 2.83 volts. If you use 1 watt @ 1 meter as the test for efficiency, then the impedance alone doesn't determine efficiency.

Kex
Thanks for the education. I always wondered why different speakers were built with a variety of impedence levels and your post clears it up for me.

[spacedeckman]

Leave it in the 8 ohm mode. Change it only if you have problems.

Easy.

[kexodusc]

Leave it in the 8 ohm mode. Change it only if you have problems.

Easy.

You could do as spacedeckman says and leave it at the 8 ohm setting. The 6 ohm setting just limits the voltage so you won't overload your receiver if you get a bit carried away. I'm guessing you'd have to be pretty freakin' loud to engage this protection anyway.

[kexodusc]

Kex
Thanks for the education. I always wondered why different speakers were built with a variety of impedence levels and your post clears it up for me.

Voice coil contributes a lot to the impedance, so cost often comes into play. You see a lot of 6 ohm drivers, 12 ohm drivers, some 10 ohm, some 16 ohms as well.

4 ohm and 16 ohm drivers are great for making multi-woofer speakers. You wire two 16 ohm drivers in parallel, and impedance drops back to 8 ohms. Wire to 4 ohm drivers in series and the impedance reaches 8 ohms.

Throw in 3 or 4 or 5 drivers in a speaker and it can get pretty complex. Hence one need for different impedances.

[Kam]

Voice coil contributes a lot to the impedance, so cost often comes into play. You see a lot of 6 ohm drivers, 12 ohm drivers, some 10 ohm, some 16 ohms as well.

4 ohm and 16 ohm drivers are great for making multi-woofer speakers. You wire two 16 ohm drivers in parallel, and impedance drops back to 8 ohms. Wire to 4 ohm drivers in series and the impedance reaches 8 ohms.

Throw in 3 or 4 or 5 drivers in a speaker and it can get pretty complex. Hence one need for different impedances.

can the comparison of wattage/ohms be made to water/pipes? i.e. if the pipe has a bigger diameter it would need more water to fill it up to produce pressure? so a speaker with a lower ohm ratings (bigger diameter to the pipe) would need more wattage (water) from the receiver to produce the same dB levels (water pressure coming out of the pipe) as a smaller diameter pipe would? is that backwards or is this just a totally asinine analogy and should be forgotten immediately?

[GMichael]

can the comparison of wattage/ohms be made to water/pipes? i.e. if the pipe has a bigger diameter it would need more water to fill it up to produce pressure? so a speaker with a lower ohm ratings (bigger diameter to the pipe) would need more wattage (water) from the receiver to produce the same dB levels (water pressure coming out of the pipe) as a smaller diameter pipe would? is that backwards or is this just a totally asinine analogy and should be forgotten immediately?

I remember my college electronics teacher using an analogy like this. But that was in 1979. I'm a little fuzzy on it now. I would think that it's not a bad analogy if all else remains the same (such as speaker sensitivity).

[Geoffcin]

can the comparison of wattage/ohms be made to water/pipes? i.e. if the pipe has a bigger diameter it would need more water to fill it up to produce pressure? so a speaker with a lower ohm ratings (bigger diameter to the pipe) would need more wattage (water) from the receiver to produce the same dB levels (water pressure coming out of the pipe) as a smaller diameter pipe would? is that backwards or is this just a totally asinine analogy and should be forgotten immediately?

But not exactly.

You've mixed up dB in there, and it's not in the current/resistance equation. Some pro sound equipment has huge SPL/watt numbers @ 4 ohms(107 dB per watt is not uncommon, and some hi-fi gear has huge SPL/watt numbers with high resistance (one horn loaded speaker has 109 dB/watt at 27 ohms!)

It's been a while since I was in school, but I seem to remember that it's 1 watt = 1 volt × 1 ampere. A watt is a unit of power, it doesn't depend on the resistance. Resistance DOES come into play when you want to crank up the amps. A lower resistance allows more current to flow easier. Amps that are not "high current" capable can have a problem with speakers of low resistance as they sometime have a hard time slewing the necessary current, even when they are not pushed to overload. Also nearly all receivers are protected in some way, and when a low resistance is detected the amp goes into protection mode.

Good "high current" amps besides having wattage ratings, will also state how much amps peak current they can deliver like; "160 Amps peak current delivery"