Impedancias

Fijémonos en lo que puede hacer el selector si lo ponemos en 4 ohmios, este es el resultado de un test a un Denon AVR-X5200W (por suerte no todos los AVRs se comportan igual):

Denon AVR-X5200W Power Measurement Table

* Impedance switch was set to low (4 ohm setting) for these particular tests.

# of CH	Test Type	Power	Load	THD + N
2	CFP-BW	140 watts	8 ohms	1%
2	CFP-BW	205 watts	4 ohms	1%
2	1kHz Psweep	140 watts	8 ohms	0.1%
2	1kHz Psweep	145 watts	8 ohms	1%
2	1kHz Psweep	193 watts	4 ohms	0.1%
2	1kHz Psweep	206 watts	4 ohms	1%
5	1kHz Psweep	97 watts	8 ohms	0.1%
5	1kHz Psweep	101 watts	8 ohms	1%
7	1kHz Psweep	78 watts	8 ohms	0.1%
7	1kHz Psweep	82 watts	8 ohms	1%
*1	1kHz Psweep	24 watts	8 ohms	1%
*7	1kHz Psweep	18 watts	8 ohms	1%
2	Dynamic PWR	200 watts	8 ohms	1%
7	Dynamic PWR	85 watts	8 ohms	1%
2	Dynamic PWR	300 watts	4 ohms	1%

Podemos ver que cuando el selector está en 4 ohmios este AVR sólo es capaz de entregar 24 W con un canal activado y la friolera de 18 W por canal con todos los canales activos (y nada menos que ya con un 1% de distorsión).

https://www.audioholics.com/av-recei...w/measurements

Este es el resumen que se hace en la misma página con respecto al selector de impedancia:

Bottom Line

Budget A/V receivers represent a compromise of features vs. performance. They are typically optimized for 8-ohm loads because of limitations in the power supply and/or the output devices. Unless you are considering one of the mid to high end spectrum of their product offerings, chances are you're not getting an amp section that will adequately drive 4-ohm loads in either impedance setting.
Don't think that flipping the impedance switch in your receiver will be your miracle solution, because in this case it certainly is NOT. What this really is in most of the receivers I have tested is an inexpensive way to claim the receiver is 4-ohm compatible without the manufacturer having to actually spend money on better internal parts in the power supply. In virtually all of the receivers we've tested with impedance switches, flipping the switch to the low setting would put your speakers at risk of receiving dangerously clipped AC signals when attempting high output levels. While it may operate more safely for a steady-state UL heat dissipation test, it's important to note the real world tradeoffs once this switch is engaged in its low setting.

Know the facts when purchasing and setting up home theater equipment. An informed consumer makes smarter purchases. Most importantly, step back and evaluate how you are using your system and make adjustments accordingly and NEVER eat at restaurants that charge you full price for 1/2 the meal! Let the boss pay for those.

https://www.audioholics.com/audio-am...tually-testing