Same watts at 8 and 4 ohms?

This is the false statement, and is the typical statement of amp manufacturers that can’t double down with their amps.

This statement is false.

I recently serviced out a Realistic receiver with 18 watts. Even though it has no chance of doubling its power at full power, at power levels less than full output, it does so with ease, for the simple reason that despite its inadequate supplies and heatsinks, the amp behaves as a voltage source. Its only that last 3dB into half the impedance that is being touted as such a great thing- and really has very little effect if any on how the amp actually sounds.


Any conversation otherwise really points to not understanding how a voltage source works, and why its important. Now its been pointed out that no amp can really double its power at full output when the load is halved. This is true because of a thing called Ohm's Law. It has to do with the output impedance of the amplifier being finitely more than zero. Whatever that value is, it will always prevent the voltage amp from perfectly doubling power as the load impedance is halved ***at full power***.


Since actually doubling power at full power can't be done, how important is it? If sound quality is your goal, its likely that the amplifier topology will play a bigger factor in the sound of the amp,  on account of how it makes distortion, and how audible that distortion is, especially at lower power levels where the amp spends most of its time with real music signals. Its also unimportant because you can't operate the amp constantly at or near full power due to the dynamic nature of music. 

I bought my big krell amp because my apogee duetta 2 speakers are very inefficient at 80db/w. 

The big Krell current wattage doubling grunt is not really fully utilized here, great sounding amp still with these speakers just a bit of overkill.

Apogee Duetta 2 is one speaker that doesn’t need so much an amp that can "nearly" double all the way down to 2ohms from 8 and 4 ohms.
Because it’s load impedance is very benign lowest at 5ohms,
https://www.stereophile.com/images/archivesart/Duetfig1.jpg

But as you say it’s efficiency is only 80db and this just needs lots of watts, even high wattage Class-D and or linear Mosfet poweramps will suffice into these speakers.

Cheers George

hi,

I have a few thoughts, no answers,

1. consider selling those speakers now, then pick new or used speakers and amp together

I am a proponent of efficient speakers (close to 90db/w/m or above, they are) and nominal 8 ohm rather than 4 ohm, certainly not a fan of even lower (they are low).

Efficient speakers need less power, which puts you in position to need a lower cost amp. If you ever want to try a tube amp, the higher the speaker’s efficiency the better to help keep cost/size/heat down which also increases placement options.

2. features, remote volume and include remote balance. a very small balance tweak can make a surprisingly large improvement. you might want tone controls,

3. low volume listening is likely, so: automatic boosting of bass as volume is reduced is important to retain involvement. Enjoying a Jazz bassist, lower volume, bassist will progressively disappear, unless you compensate for your/our ear’s reduced ability to hear bass tones as volume reduces.

The industry stupidly named this optional control ’loudness’. It should be named ’low volume boost’. It needs to be properly implemented if automatic, or at least have a remote bass control you can adjust (then consider, how does it get back to normal? reset when power off/on? visible indicator?)

https://en.wikipedia.org/wiki/Equal-loudness_contour#:~:text=The%20Fletcher%E2%80%93Munson%20curves%20are,the%20Acoustical%20Society%20of%20America.



4. separate ’control unit’ (similar but not a pre-amp) for remote functions, then use ANY amp.

i.e. I use this discontinued remote control unit to give me remote volume/balance/automatic loudness compensation/input selection.

https://www.usaudiomart.com/details/649391586-chase-technologies-rlc1-remote-line-controller/images/1694271/

that one is sold, they come up for sale occasionally.

note: no pre-amp needed for any line level input. I use my preamp for phono, the preamp is then 1 of the 4 line-level inputs to the remote line controller, and then it outputs to ANY amp with no features. you could simply have a separate unit for phono eq now or in the future.

???? anybody know ??? currently available units available to do this.

Elliott, thank you for the thoughtful response. I will take it all into consideration.

However, right now and against the prevailing wisdom here is what I am going to do and why.

I am going to order the Sonos Amp for my birthday next month. Here is why:

Class D, 125w into 8, 200 into 4 and "4 ohm stable" for whatever that is worth. Right now I'm satisfied with 75w into 8 from an old Onkyo AV unit. The Sonos AMP will be a step up from that I suspect. If so I can live happily with it.

It is small, runs cool, nothing else will need to be attached to it since I can ditch the Sonos Connect and use it elsewhere. That means it will be discrete and out of sight and make my wife happy and be controlled entirely by my cell phone or hers. And that is important! She will use it if it is no more than using the Sonos app. And if she uses it then there is buy-in and that is good.

It comes with a trial period with free return shipping so no risk if it turns out to be a huge mistake.

It has balance, simple EQ and fairly effect "loudness" switch for low volume listening. Even with the Onkyo and even at low volume the bass via Sonos with loudness on sounds very pleasing to me.

If the Sonos Amp plus the Aerial 6Ts just don't work out I can try the Aerial 5Ts plus the JL Audio sub with the Sonos Amp but I would rather not since I'm not fond of subs and that is more room clutter to make my wife unhappy. The 5Ts and the sub are still for sale right now.