Car amp for 4 ohms to 8 ohms?

[barber02]

Aren’t passive impedance compsesation networks available for home stereo amplifiers so the amplifier sees an 8ohm load no matter how low the impedance is of the speaker load. I used to use one on my amplifier when I was running 4 or more speakers. A car amplifier would do the job but is more costly and requires more equipment than the alternative I suggested above. Maybe I misunderstood the question. IDK

Just my two cents,

David

 

[Gioba]

A 2 channel stereo receiver. No FM or am tuners. The audio sources is turn table and CD player and TV with 2 channel duties. I have looked at the recent market and I have seen 2 channel reciver's from 6 ohms to 8 ohms but, not 4 ohms to 8 ohms? My friends tweeters are vifa ring radiator tweeters rated at 4 ohms. Last time I tried running my magapan MG 12's on Marantz integrated amp rated at 8 ohms only ( years ago ?) So the amp was popping fuses and the company said it was my speakers ohms load doing it. So I ended up selling both due to miss information on the amps ohms out put. So I put a post on here to see where it would go and if I was heading in the right direction? I hope this helps? Jeff

The difference on the load seen by the amplifier 8 ohm to 4 ohm and reverse it isn't a mathematical formula.
The nominal impedance is different to a real impedance in both cases.
So 2W at 4 ohm not get 1W at 8 ohm precisely and the other way around, and with bridge configuration get quadruple power extremely rarely.

It depend each situation, how many speakers, the nominal impedance each, module with frequency, passive filter type, series or parallel...
At same way i don't think the 4 ohm tweeter can be an issue for an 8 ohm amplifier, because it works on a frequency range not critical about impedance module.
I think to a different problem for the Marantz amplifier.

With a power supply 12v you can use the car amp you want with the suitable power.
In domestic use the polarized AB class is the better choice for me.
Hope to aid you.

 

[steveu]

Aren’t passive impedance compsesation networks available for home stereo amplifiers so the amplifier sees an 8ohm load no matter how low the impedance is of the speaker load. I used to use one on my amplifier when I was running 4 or more speakers. A car amplifier would do the job but is more costly and requires more equipment than the alternative I suggested above. Maybe I misunderstood the question. IDK

Just my two cents,

David

A transformer/auto-transformer can convert impedance with minimal loss but the load impedance is always reflected, ie the transformer applies a multiplication factor. It does not limit the impedance range, except to the transformer limitations like wire resistance. Defining impedance requires adding resistors and wasting output power. And hi-fi quality transformers are large, ie 5Kg+. A small transformer will suffer from core saturation and inductive shunting, ie a short at frequencies below, say 100Hz, depending on how big the transformer is. The result is that amplifiers with VI protection go crazy trying to drive a transformer, and ironically may be damaged.

At issue is that an amp designed to deliver the voltage required for a given power onto 8 Ohms will either have to deliver twice that power into 4 Ohms or else misbehave when the current limit is reached.

Distribution boxes will first convert the amplifier load by times root👎 where n is the number of speakers. For example, a transformer that reduces the amplifier voltage by 1/2, changes the amplifier load impedance by 4x, so 4 speakers appear the same impedance as one. This creates a 6dB loss, 1/4 power to each speaker, but 6dB is not as obvious as you might expect. A 100W amp can be split down to a couple Watts per speaker and still be a good listening level.