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Which watts are the right watts in SS amps?

Hello Sports Fans!

More than a few people over the years on these pages have said only those SS amps which double down in output power as impedance drops are truly special or worthy amps. Eg., 200 @ 8ohms; 400 @ 4 ohms; 800 @ 2 ohms; etc.

Not every SS amp made does this trick. Some very expensive ones don’t quite get to twice their 8 ohm rated power when impedance halves to four ohms. BAT, darTZeel, Wells, and Ypsalon to name just a few.

An amps ‘‘soul’’ or it’s ‘voice’ is the main reason why I would opt in on choosing an amp initially and keeping it. Simultaneously , I’d consider its power and the demands of what ever speakers may be intended to be run with it or them.

I’ve heard, 80% of the music we are listening to is made in the first 20wpc! I’m sure there’s some wisdom in there somewhere as many SS amps running AB, are biased to class A Only for a small portion of the total output EX. 10 – 60 wpc of 150 or 250 wpc.

After all, any amps true output levels are a complete mystery when anyone is listening to music anyhow.

I suspect, not being able to actually measure true power consumption, the vast majority of listening sessions revolve around 60wpc or so being at hand with traditional modern reasonably efficient speakers.

Sure, there are those speakers which don’t fit into the traditional loudspeaker power needs mold such as panels or electrostats, and this ain’t about them.

The possibility of clipping a driver is about the only facet in amp to speaker matching which gives a person pause while pondering this or that amplifier.

I feel there is more to how good an amp is than its ability tou double output power with 50% drops in speaker impedance.

However, speakers are demanding more power lately. Many are coming out of the gates with 4 ohm ‘nominal’ IMPs which lower with fluctuations in frequency. Add in larger motors on larger drivers, multiple driver arrays, and on paper these SOTA speakers appear to need more power.

IMHO It is this note which introduces great concern.

I’ve read every article I can find on Vienna Acoustics Music. Each one says give them lots of watts for them to excel.

Many times good sounding speakers I’ve owned sounded better with more power, albeit from arguably a better amp.

I tend to believe having more than an adequate amount of cap power is indeed integral. … naturally the size and type of transformers in play possess a strong vote for an amps ability to successfully mate with speakers.

Controlling a driver’s ability to stop and restart is as well a key to great sound and only strong amplifiers can manage this feat. Usually this gets attributed to ‘damping’ factor, but damping as I read it is more a shadow than a tangible real world figure as it depends on numerous factors. Speaker cable length alone can alter damping factors.

A very good argument exists about those mega watt amps voices. Each 500 or 600 wpc amp or amps, I’ve heard have had stellar voices too, not merely more watts.

So is it predominately these mega watt power house amps souls or their capacities that fuels the speakers presentation?

Would you buy an ‘uber expensive’ amp based more on its voice or soul, than on its ability to output loads of watts, even if you feel the amp may be somewhat under powered for the application?

Choosing this latter option also saves one money as the more powerful amps do cost more than their lower outputting siblings.

Please, share your experiences if possible.

Tanks muchly!

blindjim
blindjim OP
3,092 posts
 

@almarg
Hi Al. Thank you.

finally I’m able to comprehend fairly well what you said. Almost.

I feel I was already on board with your preliminaries. XDB @ 1w, or XDB at 2.83v.

As for that -3db item regarding 4 ohm impedance speakers, is this attribute a constant with respect to power across the bandwidth?

IN other words, with a 4 ohm IMP whatever speaker will it always be 3db down in SPL at what ever rated amplifier output that it would be if an 8 ohm load was present?

I got the impression making a speaker IMP 4 ohms incidentally obtained automatically about a 2 – 3db gain in response or sensitivity.

Another item has my attention with respect to amplifiers. Gain.

Actually, matching pre amps (lines, DAC, etc) with what ever amplifier. Each amp, has its own amount of gain.

Regularly we see here and elsewhere, output to input IMP should have 1 to 10 ratios. 1K out IMP needs a 10K input or better.

Is there as well a general rule of thumb for preamp gain and amplifier gain one should keep in mind irrespective of the load when choosing a preamp & power amplifier match?EX.
Keep the line stage gain at 25% of the power amp rated gain.
Keep the line stage gain at 50% of the power amp rated gain.
Keep the line stage gain at 75% of the power amp rated gain.

Or this relationship is not how or where to look best for synergistic or electrical matching purposes?

Best regards…
= = = = = =

RE – testing and verifying speaker or amplifier specs
I suppose one avenue is to look towards amplifier & loudspeaker makers individual reps.

Some speaker makers are decidedly making their units aimed squarely at lower powered amps like SET. More than a fair number of monitors stay in a more ‘easy’ range many amps will like to see too.

The rest whose EFF or as they rate them in IMP at 4 ohms or lower, despite their rated sensitivities, are probably saying use decent amplification here. As a fair number of maker spec sheets often include minimum power ratings for their units. Albeit, the speaker makers seldom if ever indicate what listening levels one will derive using an amp outputting their minimum recommended wattage.

Apart from first hand evals a good reviewer will drive what ever speaker with several amps for comparisons sake and detail those desparities in their accounts.

Then too, some are mighty vague saying only “these speakers enjoy power”. Or ABC speakers worked best with a lot of power or a powerful amp. This leads one to believe they MUST employ a substantial power plant and no less, if that speaker is picked for a system.

Of course, one can deny the accounts and reviewer’s reviews as mere advertising and as such all bets are off regarding probative value or integrity contained within the account.

At some point however, we gotta believe someone somewhere on something.

The vast majority of people neither have the inclination, training, or resources to get uot there and test everything, everywhere, everytime. Nor would many want to.

It isn’t wrong to expect device makers demonstrate good faith in the specs they claim either. It does seem a bit naïve to lean more than lightly onto them of late.

almarg's avatar
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almarg
9,670 posts
 
Hi Jim,

As for that -3db item regarding 4 ohm impedance speakers, is this attribute a constant with respect to power across the bandwidth?

IN other words, with a 4 ohm IMP whatever speaker will it always be 3db down in SPL at what ever rated amplifier output that it would be if an 8 ohm load was present?

I got the impression making a speaker IMP 4 ohms incidentally obtained automatically about a 2 – 3db gain in response or sensitivity.
If a 4 ohm speaker is rated to produce the same SPL at 1 meter as an 8 ohm speaker, and both ratings are specified on the basis of an input of 2.83 volts (rather than 1 watt), and the SPL and impedance ratings are accurate, the 4 ohm speaker will require twice as many watts (i.e., 3 db more power) to produce the same volume as the 8 ohm speaker, at a given distance and at all frequencies for which those ratings are accurate.

But also keep in mind that most solid state amplifiers can deliver significantly more power into 4 ohms than into 8 ohms, and in some cases twice as much.

Regularly we see here and elsewhere, output to input IMP should have 1 to 10 ratios. 1K out IMP needs a 10K input or better.
Although that guideline is commonly stated, as you indicated, it’s not that simple. See my post dated 10-3-2016 in the following thread:

https://forum.audiogon.com/discussions/audio-research-ls-25-mkii-compared-to-actual-ar-production

Is there as well a general rule of thumb for preamp gain and amplifier gain one should keep in mind irrespective of the load when choosing a preamp & power amplifier match?
Power amp gains generally tend to be in the area of 25 to 30 db or so, although some are significantly higher and some are significantly lower. The gains of active line stage preamps in recent decades generally tend to be in the area of 6 to 15 db or so, although some are considerably higher, and at least a few are somewhat lower. Differences in gain will affect what settings of the volume control will be used, but of course won’t affect the maximum amount of power that can be delivered to the speakers. Volume control positions will also be affected by speaker sensitivity and the output level of the source components. If any of these four factors is considerably higher or lower than usual attention should be given to the possibility that the volume control may have to be used too close to the bottom of its range, or at the other extreme that it might even run out of range at the top with some recordings.

Best regards,
-- Al

georgehifi's avatar
georgehifi
10,312 posts
 
It's useless to talk about 4ohm speaker and 8ohm speaker, as none are flat at that impedance across the audio band, they are very different. And the best way to treat it is to look at the lowest impedance and - phase angle and base an amp around that.

1: There can be dips in the impedance curve at certain frequencies that can be very low. 
2:There are also negative phase angles at certain frequencies that can be very high.

Combine the one and two at certain frequencies and you have almost a short as seen by the amplifier "usually" in the bass.

EG:
Wilson Alexia is spec'ed by Wilson at 90db and 4ohm

Independent test measured:
I in the power region of the bass between 60hz and 110hz approx it has a nominal impedance of just 1.9ohms!, combine this with the negative phase angle of around -45 degrees and you have an EPDR (equivalent peak dissipation resistance) that the amp sees as just .9ohm!!!!!   

So much for being designated as a "4ohm speaker"!!!
And the Sofia 3 is even worse than this.

Cheers George


   
  
willemj
1,036 posts
 
The conclusion is that good engineering demands speakers that are easy to drive and amplifiers that retain a flat frequency response under varying loads. Combine such units, and you are fine. Combine hard to drive speakers with most tube amps and you have a response that is all over the place.
georgehifi's avatar
georgehifi
10,312 posts
 
good engineering demands speakers that are easy to drive

This would be great, maybe in the future with different construction techniques, motor design, materials ect, but for now easy to drive speakers usually have other permanent compromises, that can’t be fixed driven by the right amp.
At least the expensive hard to drive speakers are just that because they present no compromises except one, being asked to be driven with amps that can drive them with the current that's needed. 

Cheers George
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