here is one impedance question
Suppose we have one amplifier class AB that is specified to 200w @ 8R
suppose that we load this amplifier with a load that is 64 R ( 8 units of 8R in series )
wiring will be very short
units are relatively small and equal so theoretically 200w of power will be equally distributed to the nod and each unit will handle 1/8 of the power .
So electrically that sounds ok
Question is what will happen soundwise and this type of load effect in the performance of the amplifier
--Will slew rate change ?
--Will damping factor change
--Will frequency response change ?
--Is there a chance that amplifier will oscillate due to load is out of specs ?
--is there anything else that might go wrong with such an arrangement ?
kindest regards
Sakis
Suppose we have one amplifier class AB that is specified to 200w @ 8R
suppose that we load this amplifier with a load that is 64 R ( 8 units of 8R in series )
wiring will be very short
units are relatively small and equal so theoretically 200w of power will be equally distributed to the nod and each unit will handle 1/8 of the power .
So electrically that sounds ok
Question is what will happen soundwise and this type of load effect in the performance of the amplifier
--Will slew rate change ?
--Will damping factor change
--Will frequency response change ?
--Is there a chance that amplifier will oscillate due to load is out of specs ?
--is there anything else that might go wrong with such an arrangement ?
kindest regards
Sakis
No.
Of course. Damping factor is load impedance divided by output impedance of amplifier. You change load impedance and output impedance of amplifier remain same.
Full power bandwidth? No. It is depend on slew rate. The slew rate is same.
If load impedance higher than 8 ohm in solid state amplifier, it won't oscillated, unleash the design is bad.
If your acoustic goal can be achieve, there is nothing wrong with that.
Ok thank you for very detailed answer
can you describe what might go wrong again soundwise when the damping factor change ?
can you describe what might go wrong again soundwise when the damping factor change ?
You are talking about 8 series-connected 8 ohm resistors. Or about 8 8 ohm speakers?
The power of the amplifier with a load of 64 ohms will decrease by about 8 times compared with a load of 8 ohms.
Damping of the speakers connected in series is done through other speakers 🙂
At different frequencies of mechanical resonance at these frequencies, the voltage on the speakers can differ up to 10 times.
Yes! This means interdependence of speakers and the possibility of damage.
The power of the amplifier with a load of 64 ohms will decrease by about 8 times compared with a load of 8 ohms.
Damping of the speakers connected in series is done through other speakers 🙂
At different frequencies of mechanical resonance at these frequencies, the voltage on the speakers can differ up to 10 times.
Yes! This means interdependence of speakers and the possibility of damage.
Last edited:
If the amp is capable of four ohms loads also, it might be preferable DFwise to connect each two speakers in series and the resulting four pairs in parallel.
Best regards!
Best regards!
Speaker specifications are based on voltage control. It is believed that in the medium and high frequency region, better results are achieved with current control.
Better in four series. Two chains in parallel. Get 100 watts (16 ohms) - 12.5 watts per speaker.
If your load impedance increase, your damping factor increase also. Damping factor influence the sound of low frequency. But in most solid state amplifier, you should not worry about damping factor, because they are really high.
I think it is better to connect your speaker series-parallel so the total impedance close to 4 to 8 ohm. So the amplifier can deliver their maximum power.
This sort of system is exactly the reason 70v & 100 v systems with transformers were invented. Besides preventing internal oscillations in the speakers, with cone mass acting as energy storage, those systems save a lot on wiring over long distances. You should try the experiment with an amp & 8 speakers. I imagine the sound has boomy frequencies (local mechanical oscillations) on the speakers in the middle of the chain.
Furthermore, in the used market I participate in, 25 v & 70 v output amps are available operational for $.50 to $.90 a watt, including freight. Example crown S180 and S280 (one & 2 channel 80 watts) and Peavey MMA-875t (one channel 75 watts) and MMA-81502 (one channel 150 watts). As prices of used road veteran 200 to 1500 W PA amps head for the stratosphere, these transformer output amps are heavily discounted. They don't sound bad.
Furthermore, in the used market I participate in, 25 v & 70 v output amps are available operational for $.50 to $.90 a watt, including freight. Example crown S180 and S280 (one & 2 channel 80 watts) and Peavey MMA-875t (one channel 75 watts) and MMA-81502 (one channel 150 watts). As prices of used road veteran 200 to 1500 W PA amps head for the stratosphere, these transformer output amps are heavily discounted. They don't sound bad.
Last edited: