Speaker Impedance Question

[Speakerguy]

we've already explained to you, a higher impedance is no problem, just that it will be a LOT quieter.

Actually the two in series will be the same volume at the same drive voltage just with half the current You lose 3dB because you're only delivering half the power to the load, but you gain 3dB due to improved radiation impedance of using two speakers (the impedance match of a speaker diaphragm to the air load is horrible due to the relative masses, so doubling the area gives you twice the radiation gain). This is why horns exist - they're basically acoustic transformers. Hence why you see them where high efficiency is needed - stadiums, concert venues, etc. A traditional loudspeaker is so poor at converting electrical energy to acoustic energy that >99% of the power delivered will be dissipated as heat. Horns drop that figure to 90% or less depending on the design by improving the impedance match. (for reference, an acoustic watt is something like 112dB/1w/1meter, a typical loudspeaker will be 90dB/1w/1meter for efficiency).

Also, you get +6dB out of a parallel connection for voltage sensitivity for the same reasons.

I'm sure audioguru will come by and correct me if I'm wrong Which I tend to be a lot of the time...

 

[Speakerguy]

I'm talking about the speaker being damaged because it has a higher impedance than recommended for the amp

No, that won't happen with solid state (transistor) amps. If you see vacuum tubes inside that might not be the case, but I don't know since I don't know a whole lot about valve amp design.

 

[Nigel Goodwin]

I'm sure audioguru will come by and correct me if I'm wrong Which I tend to be a lot of the time...

I'm afraid you are this time as well!.

Assume you have an amplifier that outputs 100W to 4 ohms, and you have two 8 ohm speakers. If you put them in parallel you get 50W out of each speaker, total 100W. If you put them in series you get 12.5W out of each, total 25W - only one quarter of the correct connection. The audible difference is HUGE - I've been there and done it, many, many times - rewiring PA systems to give enough volume!.

 

[De1337]

I'm glad you cleared this up for me, I appreciate it

So, higher impedance means less volume, if you for example use the same amp, same config, but rewire the speakers to series, for whatever reason.

Higher impedance does not damage speakers, only if an amp powerful enough to push more watt through the impedance than the speakers can handle, is connected, and of course, played too loud.

Lower impedance means more power can easier be pushed through the speaker, but hence requires an amp capable of driving at that impedance? (i.e. 4 ohm amp and 2x8 ohm speaker in parallel)

Higher impedance requires you to turn up the volume more to reach same amount of dB as if speakers had lower impedance, and this also requires a more powerful amp than if the same speakers had been of low impedance.

That being said, it all comes down to the power of the amp, and the speakers can never be damaged if not being over-watted (as in turning up the volume too loud, distortion and blown out drivers).

If I got all that right, then...
What's more damaging for the amp? Too low or too high impedance... I'd say too low, but am I wrong?
Edit: Elaboration... You say if the impedance is doubled the amp delivers half the volume at same setting, so suppose you turn the amp up to the level you want, which would be much louder at lower impedance.

Thanks in advance

 

[Leftyretro]

I'm glad you cleared this up for me, I appreciate it

So, higher impedance means less volume, if you for example use the same amp, same config, but rewire the speakers to series, for whatever reason.

Higher impedance does not damage speakers, only if an amp powerful enough to push more watt through the impedance than the speakers can handle, is connected, and of course, played too loud.

Lower impedance means more power can easier be pushed through the speaker, but hence requires an amp capable of driving at that impedance? (i.e. 4 ohm amp and 2x8 ohm speaker in parallel)

Higher impedance requires you to turn up the volume more to reach same amount of dB as if speakers had lower impedance, and this also requires a more powerful amp than if the same speakers had been of low impedance.

That being said, it all comes down to the power of the amp, and the speakers can never be damaged if not being over-watted (as in turning up the volume too loud, distortion and blown out drivers).

If I got all that right, then...
What's more damaging for the amp? Too low or too high impedance... I'd say too low, but am I wrong?
Edit: Elaboration... You say if the impedance is doubled the amp delivers half the volume at same setting, so suppose you turn the amp up to the level you want, which would be much louder at lower impedance.

Thanks in advance

"If I got all that right, then...
What's more damaging for the amp? Too low or too high impedance... I'd say too low, but am I wrong?"

That sounds just right to me. A solid-state class A/B audio amp is a voltage amp using negitive voltage feedback and is very happy working into no load at all (infinite speaker impedeance), while driving too low of a speaker impedenace can drive the amp's output devices outside their safe operation range of current and heat dissapation.

Vacuum tube amps are a different animal and do not like to work without speakers load hooked up as the impedence ratio of the output transformer (if used) will not allow the tube to work at it's attended load line.

Lefty

 

[Nigel Goodwin]

"If I got all that right, then...
What's more damaging for the amp? Too low or too high impedance... I'd say too low, but am I wrong?"

Too low will blow a transistor amp, too high is better than normal for it, as it has to work far less hard.

That sounds just right to me. A solid-state class A/B audio amp is a voltage amp using negitive voltage feedback and is very happy working into no load at all (infinite speaker impedeance), while driving too low of a speaker impedenace can drive the amp's output devices outside their safe operation range of current and heat dissapation.

Vacuum tube amps are a different animal and do not like to work without speakers load hooked up as the impedence ratio of the output transformer (if used) will not allow the tube to work at it's attended load line.

Valve amps use impedance matching (which is one reason why they are so inefficient), it's very important to match the speaker to the output of the amp - most output transformers have different taps so you can select the common impedances. Incidently, back in the valve days, the standard impedance was 15 or 16 ohms - lower impedances only became common with transistor amps, because they need lower impedances to provide more power.

Running a valve amp with no load is a serious problem, and can easily kill the amp.

 

[De1337]

Well, since it takes more voltage to get the same power level, it's possible that to get the volume you want you might have to turn up the amp so high that it clips. Clipping can be damaging to the speaker and possibly the amp, though it's pretty unlikely to affect the amp.

That's what I mean with too high impedance... How much higher impedance, with same output dB is acceptable to most amps? One that's designed for 4 ohm, driving 16 speakers at same output level as it would with 2 4ohm speakers.... how can that not be hard for the amp, if the above statement is right.

edit: sorry if i'm a pain

 

[Leftyretro]

That's what I mean with too high impedance... How much higher impedance, with same output dB is acceptable to most amps? One that's designed for 4 ohm, driving 16 speakers at same output level as it would with 2 4ohm speakers.... how can that not be hard for the amp, if the above statement is right.

edit: sorry if i'm a pain

As you increase the output impedenace load the amp will just not be able to supply the same, as you call it, db power. The amps maximum power capablity is limited by it's DC power supplies rail voltage. Output power delivered is calculated as (voltage X voltage) / impedence, so if the max voltage is fixed (it is by the amps DC power supply voltage) then raising the speaker impedence decreases the power consumed, it's really a basic ohms law thing. It won't hurt the amp but if you do overdrive the amp into clipping you can damage the speakers due to the high frequency harmonics created by clipping. Tweeters are usually the first to fail in that kind of situation.

Lefty

 

[De1337]

As you increase the output impedenace load the amp will just not be able to supply the same, as you call it, db power. The amps maximum power capablity is limited by it's DC power supplies rail voltage. Output power delivered is calculated as (voltage X voltage) / impedence, so if the max voltage is fixed (it is by the amps DC power supply voltage) then raising the speaker impedence decreases the power consumed, it's really a basic ohms law thing. It won't hurt the amp but if you do overdrive the amp into clipping you can damage the speakers due to the high frequency harmonics created by clipping. Tweeters are usually the first to fail in that kind of situation.

Lefty

Thanks Now i think i get it

 

[Hero999]

Connecting speakers in series isn't recommended because it will ruin the damping factor.

 

[De1337]

Connecting speakers in series isn't recommended because it will ruin the damping factor.

damping factor?

 

[Speakerguy]

I'm afraid you are this time as well!

Dude, don't tell someone they're wrong when you don't understand their post.

An 8 ohm speaker will have 'X' output when connected to an amp. Two 8 ohm speakers connected in series will also have 'X' output when connected to the same amp. Two 8 ohm speakers connected in parallel will have 'X+6dB' ouput when connected to the same amp. This is essentially the same thing you posted. We're repeating the same thing.

Another way of looking at it: Both series and parallel systems have +3dB radiation gain. The series connection loses 3dB due to half the current compared to a single driver, and the parallel gains an additional 3dB due to twice the current being delivered relative to a single speaker. So net +0dB gain for the series connection, and +6dB gain for the parallel.

That's all there is to it, and that's what my post above says in a albeit perhaps less clear fashion. You have kind of a crappy attitude that I've noticed in other threads too. If you're a super-mod and this is your habit then I think I'll move on.

Also, there's no need to worry about damping factor in any wiring configuration since the output impedance of solid state amps is so low. Damping factor has essentially become a meaningless spec, whether it is 100 or 1000 it's not that big a deal.

 

[Nigel Goodwin]

Connecting speakers in series isn't recommended because it will ruin the damping factor.

Makes sod all difference!

Almost every band plays through some speakers in series, it's not a concern at all.

 

[audioguru]

Almost every band plays through some speakers in series, it's not a concern at all.

They like the effects that the resonances produce. BOOM, SHRIEK, BOOM, SHRIEK. The effects have no business in a high fidelity sound system.

A resistance of only 1 ohm in the connecting cable of a fairly new high quality speaker produces an audible hump in the frequency response at resonance. A woofer has an impedance of up to 30 ohms at resonance.

Many bands use speakers without a back on the enclosure so they need all the resonance they can get for any bass.

 

[De1337]

They like the effects that the resonances produce. BOOM, SHRIEK, BOOM, SHRIEK. The effects have no business in a high fidelity sound system.

A resistance of only 1 ohm in the connecting cable of a fairly new high quality speaker produces an audible hump in the frequency response at resonance. A woofer has an impedance of up to 30 ohms at resonance.

Many bands use speakers without a back on the enclosure so they need all the resonance they can get for any bass.

Why does a series setup produce resonance?

 

[Hero999]

Because is reduces the damping factor.

 

[Gaston]

what is damping factor? the ability of the amp to control the cone?

 

[audioguru]

Take a speaker that is in a properly designed enclosure, disconnect it from an amplifier and tap the woofer's cone. It will resonate for maybe 1 second and make a "bong" sound.

Then take the same speaker and connect it to an amplifier with an output impedance of about 0.04 ohms or less, or short the speaker, and tap the cone. It won't resonate and will make the sound "thud".

When the output of an amplifier tells the speaker cone to move, it moves. When the output of an amplifier tells the speaker cone to stop, it stops immediately instead of resonating for a while.

If there is the high impedance of a resonating speaker in series then both speakers resonate.

 

[Speakerguy]

Another way of looking at damping factor is that the low impedance of the amplifier output acts as a shunt for any back EMF generated by the moving coil in the speaker motor's magnetic field.

But I still don't think damping factor is a factor at all unless you are running tube amps, which can have output impedances in the several ohm range. I've never seen a solid state amp with an output impedance of >0.1ohm, and those are on the real high side. Several hundred to a thousand is the common range I see for damping factor into an 8 ohm load. In that case, the load impedance wouldn't matter.

Besides, wouldn't a higher load impedance improve damping factor, since it's essentially load impedance divided by the amplifier output impedance? A resistor in series with the amplifier output would have the effect of lowering the damping factor by increasing the apparent output impedance, but a higher impedance due to more drive units itself should work the other way (or at least not raise the damping factor). I don't know offhand if it would improve it or if it would stay the same. Like I said, I never worry about damping factor with solid state amps (which is all I use. Tubes - blech! )

Also sorry to Nigel for my snipe earlier. I'm bipolar and I got all riled up when I thought someone was impugning my audio knowledge. I'm usually pretty good but every now and again something sets me off and internet discussions are a good was to do it for me I'll try and keep a cooler head around here.

 

[ericgibbs]

Another way of looking at damping factor is that the low impedance of the amplifier output acts as a shunt for any back EMF generated by the moving coil in the speaker motor's magnetic field.

But I still don't think damping factor is a factor at all unless you are running tube amps, which can have output impedances in the several ohm range. I've never seen a solid state amp with an output impedance of >0.1ohm, and those are on the real low side. Several hundred to a thousand is the common range I see for damping factor into an 8 ohm load. In that case, the load impedance wouldn't matter.

Besides, wouldn't a higher load impedance improve damping factor, since it's essentially load impedance divided by the amplifier output impedance? A resistor in series with the amplifier output would have the effect of lowering the damping factor by increasing the apparent output impedance, but a higher impedance due to more drive units itself should work the other way (or at least not raise the damping factor). I don't know offhand if it would improve it or if it would stay the same. Like I said, I never worry about damping factor with solid state amps (which is all I use. Tubes - blech! )

Also sorry to Nigel for my snipe earlier. I'm bipolar and I got all riled up when I thought someone was impugning my audio knowledge. I'm usually pretty good but every now and again something sets me off and internet discussions are a good was to do it for me I'll try and keep a cooler head around here.

hi speakerguy,
Stick around!

I have always considered the damping factor as the ability of a system to damp the unwanted oscillation of the system. [not just speakers].

Manually deflect a speaker cone when its not connected to an amp, release it, and it will have a rapid damped oscillation.

As a second check, short out the speaker leads, [no amp of course] and repeat the manual deflection, the cone will not oscillate as its heavily damped.

So the overall damping of a speaker cone is due to low impedance of the driving source ie; the amplifier. [not considering air resistance]

Qt:
I'm bipolar and I got all riled up when I thought someone was impugning my audio knowledge. I'm usually pretty good but every now and again something sets me off and internet discussions are a good was to do it for me. I'll try and keep a cooler head around here.

Its not a bad thing to have one's ideas, opinions or abilities questioned.
A forum, as you know, is place for open and frank debate, what you think you know, means 'squat', its convincing others by logical argument that you are right.

Regards