View Full Version : Speakers' "Suggested Minimum Amplifier Power"


JRSBat
07-29-2011, 04:32 AM
I've read several threads with questions about the speaker manufacturer's suggested maximum amp power. I could not find any discussing the manufacturer's suggested minimum power rating. If the speaker mfg suggests using an amp with 50-300 watts, does that mean I can get the speakers' best performance starting with a 50 watt amp or does it mean I need 50 watts just to get the speakers moving but substantially more watts to get the best sound out of the speaker?

My situation - I recently purchased a Jolida JD302BRC tube amp with a 50 watt rated output and 75 watt maximum power output (my 35 year old HK330C finally died). It has 4 ohm and 8 ohm speaker outputs. I am looking at some Wharfedale speakers with a suggested amp power of 50-300 watts, have 89db efficiency and are rated 6 ohms. Can my 50 watt amp get the best out of this kind of speaker or should I look for speakers with minimum power ratings of say 20 watts and above?

I am also looking at some Klipsch speakers with suggested power range of 50-150 watts, rated at 8 ohms and have 98db efficiency. Will the higher efficiency impact the answer or do I simply focus on the minimum suggested power level?

I appreciate your help.

sansui9090
07-29-2011, 05:46 AM
Hi JRSBat,
From what I have experienced is that if you have an amp that is able to produce 50watts Max, then you will need to get speakers that are efficient to get the best out of them.
I have found that it is all about matching the best gear that compliments each component, and to get gear that can produce the best sound for the type of music that you enjoy listening to.
Also you have to factor in the Room Size that you are putting them in as well.
For me, I am not a fan of small bookshelf speakers, as they can't deliver the Bottom end range that Large Floorstanding Speakers can produce.

Hope you find the sound you are looking for.
Cheers!

JRSBat
07-29-2011, 05:56 AM
Hi JRSBat,
From what I have experienced is that if you have an amp that is able to produce 50watts Max, then you will need to get speakers that are efficient to get the best out of them.
I have found that it is all about matching the best gear that compliments each component, and to get gear that can produce the best sound for the type of music that you enjoy listening to.
Also you have to factor in the Room Size that you are putting them in as well.
For me, I am not a fan of small bookshelf speakers, as they can't deliver the Bottom end range that Large Floorstanding Speakers can produce.

Hope you find the sound you are looking for.
Cheers!

Thanks - I am looking for tower speakers for the same reason - wanting more bass. I know I have to take a lot of things into account - budget, type of music I like, room size, etc. That is why I am asking about the minimum power requirements. I am guessing I have to meet that requirement before considering the other factors.

saea501
07-29-2011, 06:32 AM
The extremes of the frequency spectrum require more power to reproduce. In buying a speaker that has the ability to respond flat to 30 cycles you are creating a demand for more power from your amplifier. Whereas a speaker that cannot reproduce a 30 cycle frequency does not present as great a demand for power.

Efficiency is certainly a factor in your particular situation as you are coming into this with an amplifier that has a limited power output. Highly efficient speakers were popular before high powered amplifiers for this very reason.

You are probably going to want to look at speakers with an efficiency of 90+db if there are times when you think you might want to listen at a little higher volumes. If your listening is going to consistently be below 80db or so then your speaker selection could be opened up to a less efficient system.

John James
07-29-2011, 07:21 AM
I don't think you've gotten your answer yet. I don't have it either. I do know that I have a 50 watt amp (MC 2505) and high efficiency speakers (Cerwin Vega) and I can reach insane volume levels. It doesn't take truck loads of power (watts) to achieve "normal" listening levels. Extra power is useful for headroom so you don't drive the amp into clipping.

I'm sure someone with more knowledge will chime in soon.

pcb121055
07-29-2011, 08:04 AM
in the 15 years I spent as a retailer, I heard this question a million times. and for good reason. it's a lot like “how much horsepower do i need”. I do know that I don't like taking a trip in a car with a 60 mph top speed. It’s always working hard and feels like it. I believe we have a sense of how hard things are working and can appreciate when the device is at ease... and i believe that (in audio) this translates to sound quality. each speaker has a behavior as does each user and between the two, there is a requirement but it varies too much to have a single number describe it usefully. I can say that a good quality 50/ch amp would do a solid job on most and a reasonable job on all but a few of the rest assuming that you don't need to really throw down. my desire was always for headroom (reserve power) because in my mind, it was responsible for a sense of openness and of bass detail. for that reason, I say get the most quality power you can afford and learn the boundaries of that amplifier's/speaker’s "good performance" range. One noteable low power entry would be the nad 3020 integrated amp, which at 20wpc, really seemed to handle a wide range of speakers well, Akers might be able to point out other such hidden gems. I must qualify my experience as being from the typical solid state, tubes might sing a different story numerically.

ferninando
07-29-2011, 08:14 AM
the better the spkr efficiency the less power needed to drive them to high listening levels without amp clipping. think about some klipsch Heresy or KG4s or Forte. you'll be a happy kamper.

JRSBat
07-29-2011, 08:21 AM
the better the spkr efficiency the less power needed to drive them to high listening levels without distortion. think about some klipsch Heresy or KG4s or Forte. you'll be a happy kamper.

How about the new Klipsch versions such as the kf-28 at Best Buy, F-30 at HH Gregg or the RF-82 II at Crutchfield? They all have similar stats. Do you know how they stack up to the classics you mentioned? I can deal with Best Buy and HH Gregg locally - easy returns, etc.

One interesting note, a pair of Klipsch La Scala LS-BR Speakers were listed a day or so ago on the local CL for $1,000. They are big but efficient. If in good condition, how do they stack up to the ones you or I mentioned?

ferninando
07-29-2011, 08:37 AM
way over what I mentioned but 1000 is tooooo much. they are 500 in my area. and they are BIG. Only klipsch I suggest are the discontinued vintage. BB sells ??? I wouldnt buy there but thats me. If you can return what you dont like with NO PENELTY maybe ok. otherwise forget it. IMO
PS: nobody in BB knows anything about anything IMO. just ask what the spl is at 1 watt 1 meter, and watch their eyes glaze over.

JRSBat
07-29-2011, 09:01 AM
way over what I mentioned but 1000 is tooooo much. they are 500 in my area. and they are BIG. Only klipsch I suggest are the discontinued vintage. BB sells ??? I wouldnt buy there but thats me. If you can return what you dont like with NO PENELTY maybe ok. otherwise forget it. IMO

Wow, I thought $1,000 was good considering there is another pair for sale for $1,500 in a fancier local neighborhood.

I think BB has a penalty free return - not sure about HHG. They are about 3 miles from my house, so very easy to buy/return.

Copa1934
07-29-2011, 03:00 PM
the better the spkr efficiency the less power needed to drive them to high listening levels without amp clipping. think about some klipsch Heresy or KG4s or Forte. you'll be a happy kamper.
Finally an answer on the right track. Clipping is the larger issue here since it damages both the amp/receiver and the speakers. Minimum suggested power is with the assumption it's honest clean power. One thing I don't believe was touched on was impedance variations. At different volumes and different frequencies impedance can drop. Having sufficient head room in the components means less likely damage of components and speakers. So having the minimum recommended power is comforting, but no guarantee. Going with 1000 clean watts won't harm the speakers, more likely your ears first, as you likely won't be able to stand it once you reach around 50-60 watts anyway. Heck, at one watt I'm good. At 5 or more the wife is ready to throw me out.

JRSBat
07-29-2011, 03:26 PM
Finally an answer on the right track. Clipping is the larger issue here since it damages both the amp/receiver and the speakers. Minimum suggested power is with the assumption it's honest clean power. One thing I don't believe was touched on was impedance variations. At different volumes and different frequencies impedance can drop. Having sufficient head room in the components means less likely damage of components and speakers. So having the minimum recommended power is comforting, but no guarantee. Going with 1000 clean watts won't harm the speakers, more likely your ears first, as you likely won't be able to stand it once you reach around 50-60 watts anyway. Heck, at one watt I'm good. At 5 or more the wife is ready to throw me out.

Clipping was one of my concerns. I don't want to get speakers that will kill my amp - or my amp kill the speakers.

So is this summary correct? Please have patience if I am not getting this - just finished a full day of reviewing tax returns.

The minimum suggested power assumes "clean watts".
Clean watts occur at a lower point of an amps capabiltiy - say at 1/4 to 1/3 of rated total power
Therefore, if I have a 50 watt amp, I should look for speakers with a suggested minimum amp power of around 20 watts so I do not have to push my amp to its limits just to power up the speaker.

grey
07-29-2011, 03:28 PM
I took this from a speaker manufacturer's manual that is known to have well built components.

example: Maximum power input with continuous sine wave = 200W

Note: Power amplifier headroom recommendation is 3 dB minimum; i.e., for a 100~watt
rating. use a 200.watt amplifier.

For the example above, they are recommending a 400W amplifier.

JRSBat
07-29-2011, 03:47 PM
I took this from a speaker manufacturer's manual that is known to have well built components.

example: Maximum power input with continuous sine wave = 200W

Note: Power amplifier headroom recommendation is 3 dB minimum; i.e., for a 100~watt
rating. use a 200.watt amplifier.

For the example above, they are recommending a 400W amplifier.

That is consistent with some stuff I have found on the web. What is confusing is that I hear completely different opinions from audio sales reps (imagine that!). One rep said "Don't worry about minimum power recommendations - your 50 watt amp can power any tower speaker". Another was saying my amp could easily power the speakers with 50 watt suggested minimums he wanted to sell me.

I get the feeling that modern towers generally do not have the efficiency to work well with my amp. Seems I might need to stay with older Klipsch type speakers or modern bookshelf speakers/sub.

JRSBat
09-18-2011, 06:40 AM
Just a quick follow up - I purchased a demo pair of Focal 816v tower speakers. The speakers are 8 Ohm (4 Ohm minimum) with a published minimum power requirement of 40W and an efficiency of 91.5dB. I was able to audition them for a couple weeks with no strings attached just in case my 50W amp was not up to the job. Short answer - the amp was more than enough to power the speakers - and get them to produce very clear, beautiful sound.

If you want more details:

Variable 1 - this maybe skews the numbers to my benefit. I have a PS Audio phono amp with adjustable gain. I do not know how much this impacts the final answer. It seems the phono amp is contributing a lot more than simply stepping up my medium output cart.

Variable 2 - my amp has 4 and 8 Ohm speaker posts. After trying both, I wound up attaching the speakers to the 4 Ohm posts.

I set the gain knob on my phono amp at around 1 or 2 O'clock and the amp volume knob at around 9-10 O'clock (around 1/3 power). With these settings, the speakers produce a clear strong sound. The free Sound Meter app on my Droid says the dB level is in the 80's - I usually turn it down a little for normal listening.

Maybe the textbook answer of doubling the minimum watt rating would produce an even better sound - I don't know. In the unscientific world of my equipment and room size (20' x15' x 8') the 50W amp easily covers the speakers' 40W minimum rating.

Now, about acoustic treatments..........

whoaru99
09-18-2011, 08:41 AM
IMO, the range of power given for any speaker really doesn't mean that much. Ever notice the range of power given for most speakers seems to encompass a fair number, maybe even a majority, of the amps out there? Coincidence?

Besides, the VAST majority of time spent playing the speakers will be WAY under the "minimum recommended power".

Also, not convinced that clipping in any but severe cases may actually damage the amp. Worst that probably would happen is a thermal shutdown due to higher power dissipation if the clipping was really bad for a long time.

.... the amp volume knob at around 9-10 O'clock (around 1/3 power).

Unless you have measured the output or the system has been calibrated in some way to indicate this, it's a risky and probably false assumption.

BMWCCA
09-18-2011, 08:59 AM
I've never found it possible to use too much power on my speakers. You just have to remember, if it sounds bad, turn it down. :dunno:

JonVH
09-18-2011, 12:04 PM
I've read several threads with questions about the speaker manufacturer's suggested maximum amp power. I could not find any discussing the manufacturer's suggested minimum power rating. If the speaker mfg suggests using an amp with 50-300 watts, does that mean I can get the speakers' best performance starting with a 50 watt amp or does it mean I need 50 watts just to get the speakers moving but substantially more watts to get the best sound out of the speaker? What they want is for the end user to have enough headroom available that they won't clip dynamic crescendos, which could cause a sonic degradation and driver safety issue. You don't need to run them at that level, many people run their 90dB speaker around 2W for normal spirited listening. It depends on the efficiency and room too. 85dB speakers will usually be in the 7W range for the same level listening, and it doubles every time the efficiency drops by an additional 3dB.

Renzor213
09-18-2011, 01:06 PM
If you've got an amp putting out an honest 50w rms/channel, you should be fine with just about any speaker. If you look back over time, with some of the exaggerated wattage ratings once used, truth is there were many sytems running only 15-20w rms/channel. Saying that, I've been running amps of several hundred watts rms/channel for years, and never going back. Just really seems to bring the dynamics to life.