Do I need more than a 1 watt speaker amplifier?

[marksquared]

In my den I typically listen to the speakers at a volume of around 65 to 75 decibels on my couch about 2 meters from the speakers. I rarely, if ever, hit 80 or 85 decibels. Since my KEF LS50s have a sensitivity of 85 dB/W/m, and my listening volume is always below 79 dB at 2 meters, would I gain anything (pardon the pun) by using an amp that delivers more than one watt? On paper it seems like even these "hard to drive" KEF LS50s wouldn't need more than 1 watt to deliver 82 dB at 2 meters? Is there more to it than just the sensitivity, listening volume, and wattage?

In the manual, KEF says I should use an amplifier that can deliver between 25 and 100 watts. Is that just because the average user is further away and/or listens at louder levels?

I currently use a pair of monoblock Amp Camp Amps (a wonderful little DIY Class A amp designed by Nelson Pass), and they deliver 8 watts per channel. Is there any chance that I could damage the tweeters by using these "under-powered" amps, or is 8 watts per channel more than enough power for my listening levels? Even if they're safe from damage, would a more powerful amp sound better? People always use words like "authority", "grip", etc. to suggest that more watts equals better sound. Is there any science behind that?

Photo attached in case anyone would like to see the current setup.

 

[RayDunzl]

On paper it seems like even these "hard to drive" KEF LS50s wouldn't need more than 1 watt to deliver 82 dB at 2 meters? Is there more to it than just the sensitivity, listening volume, and wattage?

Play a full-scale test tone and adjust the volume to 82dB SPL.

Now play music.

Report your results.

 

[andreasmaaan]

On paper it seems like even these "hard to drive" KEF LS50s wouldn't need more than 1 watt to deliver 82 dB at 2 meters? Is there more to it than just the sensitivity, listening volume, and wattage?

In general, you want quite a bit of "headroom" to handle peaks in the program. 1W may be enough to get you to 85W continuous, but music may contain peaks up to 30dB higher in level. Perhaps counter-intuitively, classical recordings are likely to require the most power, as these tend to be far more dynamic than rock, pop and electronic recordings. So it partially depends on what you listen to. THX recommends 20dB of headroom, and this seems to me a reasonable starting point. This would imply that to achieve 85dB continuous, you would want an amp capable of of 105dB peaks, which in your case would mean a 100W amp.

(The calculation is complicated, however, by the fact that 85dB continuous at the listening position is likely to result from a combination of direct and reflected sound, and that beyond about 1m this is likely to be predominantly reflected sound. So if you're measuring 82dB at the listening position taking into account reflections, chances are you're using far less than 1W continuous into each channel, but probably more than 1W on peaks. Also note that most of the power is going to be going into the bass, as music contains a lot more bass content than midrange, and even less treble again.)

People always use words like "authority", "grip", etc. to suggest that more watts equals better sound. Is there any science behind that?

Only if you're exceeding the limits of your current amp. In other words, a lower-powered amp will not lack all these things in relation to a higher-powered amp within its comfortable operating range. Push the lower-powered amp into clipping and it will miss these things (if it doesn't just sound plain awful) in comparison to a higher-powered amp.

In summary, it's hard to answer your question for sure because it depends on your room, your music choices, and how you're measuring SPL at the listening position. My general advice would be that, if you're happy with how your current amp sounds and have never driven it into audible clipping doing what you're doing, it's probably adequate. But it certainly wouldn't hurt to move to a higher-powered amp either.

 

[garbulky]

Note: these are my personal subjective impressions, no dbt performemd.

Note 2:
I apologize because it probably is about to sound like I dissed your speakers personally. Not my intention, just giving you the best opinion I have. With that being said...
I wouldn't spend more money on LS50's, After matching them with a variety of different amps. Its quality is not worth going "up the ladder" in amps and source. Not saying it's not enjoyable of course, because it certainly is! But it's just not worth it for me.

Ok, so in terms of watts - as you have probably realized you are able to play music at lifelike volumes with your current amp. The LS50s are a little inefficient but if you are getting as loud as you listen to, I wouldn't worry.

I use 1000 watts@ 4 ohms per pair of Emotiva XPA-1 monoblocks on axiom m80s which are more efficient than the LS50s. There's no doubt that the amp does grip very nicely and evenly top to bottom without appearing to falter in the bass or midrange. It has a good low end extension and its unflappable at any volumes I care to play. It is the best amp I've heard.

Having said that I've also heard several very powerful solid state amps - I'm talking 200 to 500 watts per channel @ 4 ohms (my speakers are 4 ohms). Also I've heard 30 watt tube amps and even a 7 watt tube amp monoblocks. To my shock, the 7 watt tube monoblocks are at nearly the same level of musical enjoyent as my XPA-1 monoblocks. It cost a fraction of the cost - being a cheap integrated Heathkit kit from the 1960's that were modded to become monoblocks. Now it had different stregnths but it sounded nearly just as good producing a massive realistic soundstage with lovely dynamics and admittedly a colored tube sound. And more importantly it sounded better than alomst all of the way more powerful solid state amps. I'm not saying this to tell you that tube amps are better because I don't think they are - at all. In fact I'm not a fan of tubes in general. But what I'm saying is that it's not necessarily the wattage of the amp that's going to make a difference for you - at least based on my subjective listening. Now if you are audibly clipping the amp or it sounds like you are straining - then sure. But I think we use less power than we think.

 

[marksquared]

That's very helpful, thanks everyone!

Andreas and Ray, when I measure with my sound meter 1m away and play a few tracks at a louder than normal volume, I see a max of 83.6 dB. Does that mean I do have enough headroom?

 

[D700]

That's very helpful, thanks everyone!

Andreas and Ray, when I measure with my sound meter 1m away and play a few tracks at a louder than normal volume, I see a max of 83.6 dB. Does that mean I do have enough headroom?

Yep, sure does. I have same speakers have done same measurements.

https://myhometheater.homestead.com/splcalculator.html

 

[Blumlein 88]

The Dolby reference level is to play a -20 db pink noise track and set to 82 db at the listening position. There is a little quibbling about whether this is 82 or 83 or 85. We'll go with 82 db SPL at the listening position, and this is for one speaker (or 85 db SPL for two speakers). The idea is to give you 20 db of headroom for musical peaks, and that the pink noise frequency vs power spectrum is similar to music.

Now in addition this is for large theaters or venues. Some recommend lowering this for smaller domestic listening rooms. Sounds like maybe you don't listen all that loud. So try setting this reference level at 75 db SPL for two channels. Without changing volume try playing some music and see what you think about the volume. If this is close to what you normally listen to in terms of volume, you still need 10 watts for momentary 95 db peaks. If this is louder than you would listen, you might be okay. Honestly, I don't see how 1 watt is going to be enough. But you have 8 watts. If the music at the 75 db reference level is loud enough you probably are going to be barely okay.

OTOH, having heard the LS50, even at moderate volume it surprised me how much better it sounded with some real power behind it. Then again I really think they should be used with some powered subs. The reason I think it needs an amp with extra power is the up and down impedance curve and the reactance involved. Reactance can cause an amp to need quite a bit more current than measurements thru a plain resistive load would imply.

 

[solderdude]

In my den I typically listen to the speakers at a volume of around 65 to 75 decibels on my couch about 2 meters from the speakers. I rarely, if ever, hit 80 or 85 decibels. Since my KEF LS50s have a sensitivity of 85 dB/W/m, and my listening volume is always below 79 dB at 2 meters, would I gain anything (pardon the pun) by using an amp that delivers more than one watt? On paper it seems like even these "hard to drive" KEF LS50s wouldn't need more than 1 watt to deliver 82 dB at 2 meters? Is there more to it than just the sensitivity, listening volume, and wattage?

When you 'hit' 85dB is that actual peak value or average value displayed by some dBA weighted meter ?

In the manual, KEF says I should use an amplifier that can deliver between 25 and 100 watts. Is that just because the average user is further away and/or listens at louder levels?

The 100W limit is to protect the woofer which can easily handle short peaks that are even higher but won't survive a party when exposed to longer periods of much higher power. Lower power amps can possibly damage the tweeter when playing louder at higher levels. When the bass clips people generally aren't very concerned after all it isn't very loud yet the tweeter can receive more 'power' than it is designed for.

I currently use a pair of monoblock Amp Camp Amps (a wonderful little DIY Class A amp designed by Nelson Pass), and they deliver 8 watts per channel. Is there any chance that I could damage the tweeters by using these "under-powered" amps, or is 8 watts per channel more than enough power for my listening levels? Even if they're safe from damage, would a more powerful amp sound better? People always use words like "authority", "grip", etc. to suggest that more watts equals better sound. Is there any science behind that?

The benefit of more power becomes obvious at louder listening levels. At the onset of clipping we start noticing a lack of 'dynamics' but the amp is already clipping. More power will prevent this.
Sound becomes more 'tactile' at higher powers and impresses more when turning up the volume for short moments when listening to your favorite song. Bass also becomes relatively 'louder' (Flecher-Munson) and thus changes the sound signature usually for the better.

You can safely use an 8W amplifier as long as you don't hear degradation of sound quality or distortion. The same is true when connecting it to a 500W amp. In that case I would not use all that power when throwing a party when people want to dance.

When you never play loud and/or use them as near fields or for soft/normal background music there is no need for more power.

The 'authority' remark has to do with the amount of volume created in the room. The 'grip' story is nonsense. An 8W amp and 1kW amp with the same output resistance and both playing at the same volume well below the clipping level of the 8W amp will sound the same (providing distortion is equally low and FR range is the same). One does not have more 'grip'.
Above clipping levels of the lower power amp the sound becomes less 'dynamic' and starts to 'lose definition' in the bass which some interpret as less 'grip'.
Also, as mentioned above, due to how our hearing works, bass 'quality' changes at higher SPL (Fletcher-Munson) which makes bass sound 'better' and brings the illusion of more bass and tactile response of the body also contributes.

At my PC I use small Dali speakers that sound quite impressive at a short distance but used them in a much larger room (with a sub) and failed to impress me. Having speakers close by drastically reduces the 'need' for a high power amp.
Larger rooms require factors more power.

 

[RayDunzl]

Andreas and Ray, when I measure with my sound meter 1m away and play a few tracks at a louder than normal volume, I see a max of 83.6 dB. Does that mean I do have enough headroom?

Assuming it's a common handheld SPL meter, it averages the SPL over a short period of time. The peak unweighted unaveraged SPL is likely to be 15 to 20dB higher.

https://www.noisemeters.com/help/faq/min-max-peak/

I'm quietly listening to TV. This display uses a UMIK-1 feeding REW on the PC.

More Sound Level descriptions

http://www.acoustic-glossary.co.uk/

More to the point: http://www.acoustic-glossary.co.uk/definitions-l.htm

 

[restorer-john]

Quality power is cheap in this day and age. There is no reason not to have at least a nice clean 100W/ch on tap.

Flea-powered amps (the 8W/ch ACA) are fun to poke around with, but you can forget rocking a room full of people or actually being able to get the hairs standing up on the back of your neck.

Anyway, the KEFs need the spiders blown out of the ports every now and then.

 

[Willem]

Some time ago Harbeth´s Alan Shaw demonstrated his top of the range M40.1 speakers in Hilversum in the Netherlands, using a pair of powerful monoblocks with fast responding output meters: from time to time he needed more than 500 watts per channel.
Until a few years ago I used a 2x45 watt Quad 303 power amplifier to drive my ESL57s. Shortly after moiing to a bigger house I also upgraded the speakers to a pair of less efficient Quad 2805s. The new set up gave me the distinct feeling that the sound was getting coarse on more dynamic music, so I bought a refurbished 2x140 watt Quad 606-2. Playing softly, there was no difference between the two amplifiers. Playing at more realistic levels, there certainly was, with more dynamic range and no longer any harshness.
When I later also updated my desktop system with a pair of Harbeth P3ESRs, I also added a refurbished 2x100 watt Quad 405-2. I will never again use underpowered amplifiers. These days power is cheap, both new and second hand: I paid 350 euro for the Q 606-2 and 175 europ for the Q 405-2, both completely refurbished. I recently bought a new 2x250 watt Yamaha P2500s for my son, for only 300 euro.

 

[restorer-john]

I paid 350 euro for the Q 606-2

A bargain if I may say so.

I really like the Quad 606-2.

 

[Willem]

Yes it was an attractive price and it is a truly very good amplifier, I think. Are there any recent measurements? Both Quad amplifiers were refurbished by a retired Quad Netherlands service engineer. His policy was to essentially replace all capacitors and resistors rather than worry about which ones were still OK after all these years and which ones were not. A few years before he had done the same with my Quad 33/303 combo.
I have always used Quad amplifiers because of my love for Quad's electrostats. Since these present such a vicious load, it seemed best to stick with Quad for the amplifiers. Peter Walker's own designs must be a good bet to use with his stats.

 

[Eurasian]

I hope some of you enjoy this tubes vs. solid state amplifier article by Roger Sanders. He touches on the difference in the way amplifiers clip and corresponding power requirements to avoid same.

http://sanderssoundsystems.com/technical-white-papers/172-tubes-vs-transistors

 

[marksquared]

Assuming it's a common handheld SPL meter, it averages the SPL over a short period of time. The peak unweighted unaveraged SPL is likely to be 15 to 20dB higher.

Thanks Ray, this is very enlightening! Based on the information everyone has provided, it sounds like I need to upgrade to 100W/ch since my peaks are probably as high as 105 dB at 1 meter.

Is there a standard issue AudioScienceReview speaker amp? It seems like there's a general consensus in the forum around the JDS Labs Atom and the Topping DX3Pro, but I haven't found anything similar for speaker amps. Amir gave the $1500 Hypex NC400 kit an enthusiastic recommendation, but, if possible, I'd love to find something under $500.

I'll also post the pair of ACAs in the Swap Meet section in case anyone is in the market.

 

[andreasmaaan]

Is there a standard issue AudioScienceReview speaker amp? It seems like there's a general consensus in the forum around the JDS Labs Atom and the Topping DX3Pro, but I haven't found anything similar for speaker amps. Amir gave the $1500 Hypex NC400 kit an enthusiastic recommendation, but, if possible, I'd love to find something under $500.

So far, there has been no DX3 or Atom equivalent in terms of amplifiers unfortunately.

There's another quite recent thread from someone looking for a similar amp here, I can't remember exactly what it's called but you should be able to find it quite easily - IIRC it's been active in the past couple of days...

A good option might be to buy a used integrated AB amp. Another idea might be to find an implementation of something like the ICEPower ASX125SE or Hypex NC122, which are basically high-performance class D modules that are re-sold by some manufacturers in a case with connectors for little more than the value of the parts. These would be a fairly safe bet, as there are extensive manufacturer measurements of the modules available online, and the finished products add nothing but connectors and a case, i.e. the same performance can be expected. I know that Audiophonics does one, but they're in France. Not sure about the US. @March Audio in Australia also does affordable Hypex-based units (amplifier module in a nice case with connectors) that would definitely fit the bill, and may just sneak within your budget when released in the very near future, I think.

 

[daftcombo]

Here you go:
https://www.audiosciencereview.com/...o-what-are-recommendable-amps-below-200.7400/

 

[Blumlein 88]

Thanks Ray, this is very enlightening! Based on the information everyone has provided, it sounds like I need to upgrade to 100W/ch since my peaks are probably as high as 105 dB at 1 meter.

Is there a standard issue AudioScienceReview speaker amp? It seems like there's a general consensus in the forum around the JDS Labs Atom and the Topping DX3Pro, but I haven't found anything similar for speaker amps. Amir gave the $1500 Hypex NC400 kit an enthusiastic recommendation, but, if possible, I'd love to find something under $500.

I'll also post the pair of ACAs in the Swap Meet section in case anyone is in the market.

Did you try the -20 dbFS pink noise at 75 db SPL test? With pink noise there will be limited fluctuations and you have a reference level to work from. I do think you need at least 100 watts, but you can test with what you have.

 

[marksquared]

Did you try the -20 dbFS pink noise at 75 db SPL test? With pink noise there will be limited fluctuations and you have a reference level to work from. I do think you need at least 100 watts, but you can test with what you have.

Thanks Blumlein, I'll run the test this evening and report back.

 

[daftcombo]

Audiophonics Hypex:
https://www.audiophonics.fr/fr/amplificateur-de-puissance/audiophonics-pa-s125nc-rca-amplificateur-stereo-class-d-ncore-2x75w-8-ohm-p-12756.html
I hope @amirm will scrutinize this one!