How many watts?

[anthonyTD]

With any class of amplfiier other than class A, power supplies, and their ability to deliver instant current at a sustained constant voltage becomes all important!

[Edward]

I find the online calculators useful to give a ballpark amp wattage required.

such as https://www.extron.com/calculators/a...wer/?tab=tools

[Filterlab]

8 watts then.

[anthonyTD]

Mine was around 15 watts for 93db, with 6db headroom!

[Edward]

8 watts then.

So 400 W into 4 Ω will be enough then?

[Filterlab]

I think it should suffice.

[Pharos]

I used to run a 10W class A amp at just below clipping and get 103dB. I think that this factor is exaggerated in importance, but some headroom id needed.

If the speakers are a difficult load, for example one which produces such a difficult phasing of current that it becomes very high, current delivery is a factor. But this is a different consideration from having enough power to follow peaks.

I went in the 70s for an interview with Redifusion, Orpington, and they said that their headroom was running only 1dB higher than the program peaks.

[Barry]

Slight calculation error above: 95dB@1=89dB@2m=83dB@4m= 85.6dB@3m so max from a pair is 85.6+17.8+3=106.4dB. Even more reasons to look after your hearing.

Oops! - my mistake . You are correct, a factor of 1/9 (= 1/3²) correspond to -9.54dB.

Moral: avoid doing mental calculations after half a bottle of wine!

[Macca]

I used to run a 10W class A amp at just below clipping and get 103dB. I think that this factor is exaggerated in importance, but some headroom id needed.

If the speakers are a difficult load, for example one which produces such a difficult phasing of current that it becomes very high, current delivery is a factor. But this is a different consideration from having enough power to follow peaks.

I went in the 70s for an interview with Redifusion, Orpington, and they said that their headroom was running only 1dB higher than the program peaks.

I don't think it is exaggerated, although I have noticed that people don't seem to notice when their amp is clipping on peaks. I notice and when I had the cat, who would sit and listen with me, he would react to the clipping. I'd say 10-14 dB of headroom is needed for hi-fidelity.

I'd guess 1970s analogue TV sound was heavily compressed, back then you had one little elliptical speaker in a TV and about a 4 watt amp so it needed to be.

[Pharos]

I used that Nelson-Jones amp with Tannoy Gold Lancs, and had a PPM, so peaks were accurately measured, and the Quad 33's volume pot was at just over 8 1/3, if I went higher it got rough. So as long as clipping is avoided there is enough headroom.