Minimum recommended amplification requirements and amplifier matching

Thanks!

No, I know what the designer of my speakers think, Alan Shaw. He thinks for my SHL5 and his other speakers, 100wpc is more than enough. He does not say you need to get 100wpc but 100wpc is a good power if you want some reserve power. I agreed with him before now I have experienced it. My 70wpc Naims although play really good with my speakers, when/if I want to go LOUD (rare but I do), the Naims cannot handle (understandably so) it.

This "wanting more power" thing started when my brother brought his 200wpc (8 ohms) Hypex NC400s to my house. The SHL5s showed me that they can go LOUD without any problem as long as you give the power. This romantic/lush sounding speaker turned into a monster with more power.

There is a video on Youtube at a Harbeth dealer in the Netherlands where Alan Shaw tests the 40.1s and I think they receive up to 700 watts at one point!

All I want to do is to be able to have that reserve power when I want to go loud like I did with the NC400. Though, I need to mention, the NC400 is a very good amp but I still prefer the Naims instead for listening longer periods of time. It is more enjoyable to listen to IMO.

So, is there a speaker made today that is 16 ohms, 90db+ in sensitivity that is not a horn type that would be considered a high end home speaker below $10,000? 
I haven't been able to find any.

ozzy

You're welcome, celo.

IMO there is a little more to it than the numbers you've mentioned. For instance, how loud do you typically listen? The efficiency of the speaker would also play a role as to an accurate answer to your question. The fact that the wattage output capability is doubled when the impedance is halved is usually a sign of a high quality and power (current) capable device. The idea though is simply to avoid clipping. In general, if you're not listening at loud levels you would be fine.

@cleo  Have you asked the speaker designer/ manufacturer/ importer/ dealer?  I'm sure they will answer your questions with more specificity and accuracy.

Thanks @gdhal 

So, if I buy an amp for my 6 ohms speakers with recommended minimum power of 50wpc and if the amp has a power of 50wpc in 4 ohms and 25 wpc in 8 ohms. Am I meeting the "technical" recommendation?

I know what matters is whatever sounds good to us regardless of the specs (as long as you do not know want concert levels in your room) but I am just trying to learn the technical aspect of it.

If a speaker manufacturer has the following specs; do they mean the recommended power in 8 ohms or 6 ohms?

Neither. I'd imagine the particular speaker manufacturer is providing a spec for minimum amplification because they are wanting to avoid clipping, which occurs more easily when lower powered amps are driven hard (played loud).  

I asked this question in another discussion but this one suits better.

If a speaker manufacturer has the following specs; do they mean the recommended power in 8 ohms or 6 ohms?

Specs:
Impedance: 6 ohms
Recommended power: Minimum 50wpc

Thank you
@atmasphere

You mentioned in your 12:16pm post "...all other things being equal". Am I correct that you are also speaking of the *sound pressure level*? I ask because if so, again it would seem to me that higher speakers impedance (say 16 ohm instead of 8) would mean that one would need to raise the volume/power to achieve the same SPL, and hence in so doing could increase distortion if the amp is not operating in its "comfort zone".

The 'all other things being equal' is meant to suggest that if you could magically have the same exact speakers, differing only in impedance.

16 ohm speakers do not need more power. Impedance and efficiency are two different issues; a watt into 4 ohms is the same sound pressure as a watt into 16 ohms 'all other things being equal'.

If you are used to the sensitivity spec rather than efficiency, then the 16 ohms speakers might seem harder to drive. This is because the sensitivity spec is based on voltage (2.83 volts) rather than power (1 watt). Into 8 ohms the two are the same; into 4 ohms the power is 2 watts if the voltage is the same, and into 16 ohms the power is 1/2 watt if the voltage is the same.  This can make the higher impedance speaker appear harder to drive, but if we are talking about tube amps, they are no different; in fact quite often a tube amp will make more power into 16 ohms rather than less.

The volume (power) level and the impedance of the speaker are different. For a given impedance regardless of the power, if the impedance is raised the distortion will be lower. So ideally the speaker would be of the efficiency and impedance that you can take advantage of both.

Very appreciative of the clarification @atmasphere 

One last question on this if I may. You mentioned in your 12:16pm post "...all other things being equal". Am I correct that you are also speaking of the *sound pressure level*? I ask because if so, again it would seem to me that higher speakers impedance (say 16 ohm instead of 8) would mean that one would need to raise the volume/power to achieve the same SPL, and hence in so doing could increase distortion if the amp is not operating in its "comfort zone".

Thanks again, atmasphere.

For years I drove Proac Response 2.5's with a Cary CAD-301, a rare SE triode 300B beast putting out a max rated 14W.  See the Stereophile impedance plot of the 2.5s, definitely an 8ohm speaker.  Definitely plenty loud enough when required.  Reinforces my belief that not all watts are the same.

In other words, it was/is my understanding that what you’ve stated elsewhere is that if an amps volume is *to low*, that also creates unwanted and excessive (relative to its least possible) distortion. If that is true, then it seems conceivable that a 16 ohm load could cause an amplifiers volume control to be *to low* and create more distortion than it otherwise would if operated into a lower impedance.

The volume (power) level and the impedance of the speaker are different.

For a given impedance regardless of the power, if the impedance is raised the distortion will be lower.

So ideally the speaker would be of the efficiency and impedance that you can take advantage of both.

To this end generally speaking, an 8 ohm speaker will sound better that 4 ohms and a 16 ohm speaker better than that, all other things being equal. This is simply because no matter the amp, it will make less distortion into higher impedances, and that is audible because the amp will sound smoother and more detailed.

Hello @atmasphere

Please excuse me for asking, and I believe you already know my question comes with the utmost respect for your subject matter knowledge, but given your statement quoted above, aren’t you contradicting what you’ve stated in at least one other thread here on the forum?

It was/is my understanding that you’ve stated (paraphrasing) that *all* amplifiers have a "zone" within which they must operate to achieve lowest distortion. In other words, it was/is my understanding that what you’ve stated elsewhere is that if an amps volume is *to low*, that also creates unwanted and excessive (relative to its least possible) distortion. If that is true, then it seems conceivable that a 16 ohm load could cause an amplifiers volume control to be *to low* and create more distortion than it otherwise would if operated into a lower impedance.

Thank you.

I like to run tube amps, and while 30 watts or so will make tunes on a speaker of 90 db, I think you will need more power. If it were my room, there would be no doubt. My speakers are 98 db and 16 ohms, and I really think 30 watts is about the minimum on them!

If you really want to work with tubes or even if you want your solid state to sound better, you're always better off not making the amp do something hard, like drive a difficult load. The amp will make less distortion!

To this end generally speaking, an 8 ohm speaker will sound better that 4 ohms and a 16 ohm speaker better than that, all other things being equal. This is simply because no matter the amp, it will make less distortion into higher impedances, and that is audible because the amp will sound smoother and more detailed.

So the takeaway here is if you like the tube amp- get a speaker that is more efficient/easier to drive.

I once drove a pair of monitor audio silvers with EKCO  integrated.  This is a very good tube amp indeed but with this pairing in triode the bass was very bloated.  Much better in UL mode.  I really wonder if the MA silvers aren't better off with SS gear. (Having said that I sold this to a gentleman who was very happy with this amp paired with guess what--Monitor Audio!)  Just be aware the pairing is critical.  It's often not the power that's the issue as much as the complexity of the load a given speaker presents to a tube amp--especially in triode or SE designs.  UL with a bit of negative feedback will be more predictable.

I tried a Line Magnetic with an older Gallo speaker 4 ohm 90 dB sensitivity.  It did not work well at all.  I concur with the other posts.  It’s the impedance not the sensitivity that matters.  Line Magnetic does not like low impedance speakers, but check with the distributor, Tone Imports.

+2 @willemj , agree completely. 
I used a 300W/Ch/4 ohms with Monitor Audio Silver 8s with good results.

+1 lowrider,
Impedance, not sensitivity is a more important value.
Should your speakers dip below 4 ohms, you little amp is going to have a hard time keeping up.
When in doubt, call the manufacturer.
B

More importantly, can you audition those speakers with your amp?    Specs are great but don’t always tell the whole story.  I was driving a pair of 87dB eff speakers with a 40 watt el34 amp and it was plenty loud for me in a 17 x 15 x 9 room.   Current speakers are 99 dB eff and it’s ridiculous with just 40 Watts.  

I would recommend a preamp with a gain of over 20 with a tube amp. My CAT preamp with a gain of 26 drives my 3 watt 2A3 amp to realistic levels connected to a pair of 86 db Thiel 3.6's. Of course that applies to things like solo instrument and chamber music. When it comes time for a Mahler 8 or a Bruckner 9 the Levinson beasts get called up to the plate.

It most likely will sound "loud enough", but, with respect to the referenced speaker and amp, 3 important questions:
1.  Was it designed/voiced for a solid state or tube amp and particularly what does the impedance curve look like at the frequency extremes. 
2.  What is the dynamic range of the music you listen to?  Power requirements rise exponentially on peaks. 
3.  Do you plan to run it in triode or ultra-linear mode? 

If it’s a "recommendation" and a "requirement" at the same time, I’d consider this "unusual". Typically this should be something like "recommend amplifier power", etc.

I agree with Willem and hifiman. There's more to driving speakers than the 90dB spec, and we don't know if the stated sensitivity is rated for 8 ohms or 4 ohms.
In addition to sensitivity, the impedance curve is an important factor; how much power will be required to satisfactorily drive the load throughout the frequency range; eg, does the amp have the power to drive the bass frequencies or react to peaks and transients without clipping.

@willemj  +1  My experience agrees with your's.  The old audio axiom that you can't have too powerful of an amplifier is true.  Your system can find itself in peril when it is underpowered and the sine wave is being clipped on musical peaks.  The only way an amp can be too powerful is if your two year old grabs your preamp volume knob and decides to engage in a lesson on clockwise turning!👶

I know many here disagree with me, but I am a strong advocate of powerful amplifiers for much better dynamics and less distortion on music peaks. It does depend on the size of the room, of course.

Thank you for your responses. Yes, it’s the Monitor Audio silver series with 4 ohms impedance.

90 db and 80 to 200 watts?  Is this a 4 ohm speaker? 

the line mag amp will not have a problem running 90db speakers. I have 92db speakers that provide a decent volume with a 4 watt tube amp. Not concert loud but loud enough in a 12 x 22 room open on the long sides.

more important is a speaker that doesnt have a wide impedence range