Sonic Sense
SonicSense Logo
Sonic Sense provides pro audio equipment sales and services to both the professional and consumer audio markets. support@sonicsense.com 303-753-0201 Credit Card, PayPal
Find essential pro audio gear including recording accessories, studio monitors, headphones, handheld recorders and purpose-built packages. Find essential pro audio gear including recording accessories, studio monitors, headphones, handheld recorders and purpose-built packages.
Essential Pro Audio Equipment

How Many Watts do my Speakers Really Need?

The amount of watts your PA has probably doesn't matter nearly as much as you think it does.

We often get questions from our customers asking "Should I get the higher wattage amp to power my loudspeakers?" or "This studio monitor only has 40 watts, is that going to be enough?". Many people assume that the higher wattage system is going to sound better or give them significantly more volume. Given this common misconception, I thought I'd write a little about how the output from your power amplifier relates to the performance of your loudspeaker or studio monitor.

Doubling the wattage of your amp will not double the perceived volume of your sound system!

When I was a teenager browsing my local music shop for a PA, I remember looking at the 1000w amplifiers and thinking, "man, if I could just afford to get that instead of this 500w amp, I could really blow em away!" What I didn't know then was that for most common applications, that extra power was going to make a very minimal difference in how loud I could crank it. Essentially, doubling the power output from the amplifier increases the sound pressure level (SPL) output of the speaker by 3dB. For reference, a 3dB increase in output is like turning up your car stereo by a 2-4 clicks, or something said to be 'slightly louder'; not exactly a huge difference.

Without going too far into the details, power (wattage) doesn't translate well to our ears and perceived loudness, which is specifically why the decibel (dB) was created. The dB is a ratio that works on a logarithmic scale. It translates the world of electricity and acoustics into units that we use to better represent differences in volume. While the human ear can hear something as quiet as a 0.000001 pascal (sound pressure units, abbreviated as Pa) to perceiving pain at about 20 pascals, this huge set of numbers is not very practical for simple communication to each other. Rather than saying "Turn up the PA another 35,000,000 micro pascals" its a lot easier to say turn it up by 6dB. Not to mention if we wanted to turn it up by 6dB again, this time we'd have to say "Now turn it up 70,000,000 micro pascals." Put another way, as the power output increases exponentially, our ears hear a steady linear increase in volume!

So how does this relate to your the watts of your PA? Well, since watts increase exponentially for a linear increase in perceived volume, doubling the power output makes only a small notch up the scale our ear hears. So for most consumer level PA systems (i.e. any system that is not installed in a large venue or reinforcing for more than 400 people), the extra cost in purchasing amplifiers with 150%-200% more power is rarely worth it.

So when do the watts make a difference?

If you turn your amplifier up to just before it starts clipping, and you still don't have enough volume, then at that point yes, you might need an amplifier with higher wattage. But in this scenario, as we mention above, you're not going to get much from going from your 500 watt amp to a 1000 watt amp, you'll likely need to upgrade to at least 2000 watts before hearing much of a difference (providing your loudspeakers can handle this increase in wattage). In fact for a perceived doubling in volume, you'll need 10 times the power (10dB increase), or 5000w!  At this point, you'd likely be better off just buying speakers with a better sensitivity rating. Loudspeaker sensitivity ratings tell you how many dB-SPL you can get out of a speaker using 1 watt measured from 1 meter away. These sensitivity ratings can often swing a good 3-6 dB between different models and manufacturers. A loudspeaker that has a sensitivity of 96dB 1watt/1meter, is going to give you 6 more dB of output than one with a sensitivity rating of 90dB 1watt/1meter, given both are receiving the same wattage. These speakers may be in a very similar price range, and could buy you that 6dB increase in volume for much cheaper than upgrading your amp from 500w to 2000w.

On a similar note, if you aren't getting enough volume out of your PA due to not enough wattage, and you try to force it out of your amp by increasing the amp's input sensitivity (volume knob), you may clip the input, causing a square wave to pass on the amp's output. These square waves can quickly destroy a loudspeaker's compression driver or "tweeter". Keep in mind that in this situation, it is not that the amp had too little power that blew your speaker, its that you turned the input sensitivity up until it clipped the signal it was receiving, thus sending out a square wave and frying the tweeter. The only reason this is less likely to happen with an amp with more power is that you are less likely to turn up the input sensitivity that high because its already putting out more volume. I may write a post soon clarifying this misconception of how under powering your speakers can fry them.

What about watts and how it relates to my studio Monitors?

When it comes to active (powered) studio monitors, checking out how many watts it's on board amplifier has is in a large part useless. Given the two topics we talked about above (3dB increase in volume when doubling wattage, and speaker sensitivity ratings) you really can't gather much about the monitor's performance from a watts specification. If fact, here at our office there is a pair of monitors rated at 140w that get significantly louder than a pair we have rated at 180w. I also know that I like the sound of that 180w monitor much more than one of its competitors that is rated at 225w. If you are concerned with how loud the monitor is capable of getting, take a look at its maximum spl rating, or SPL at 1 meter rating. These specifications will provide you much more insight into how loud the monitor will get than will the wattage spec.

Please feel free to leave a comment below if you have any other questions or thoughts related to the topic.

-Preston Smits

Check out all studio monitors compared by Sonic Sense.

46 thoughts on “How Many Watts do my Speakers Really Need?”

  • mike

    Schmuck... this isn't college, people won't understand this. The question was How ''Many Watts do my Speakers Really Need?'' So basically you wrote this complicated article to make yourself feel good by yapping about some random information you are aware of, that others arent. Now its time for you to re-analyze your status in life. Instead of manifesting your egotistical problems by writing pointless articles without any conceptual basis.

    Reply
  • Preston Smits

    Hi Mike, I can understand your frustration. It's hard to boil down complicated topics into easy solutions. But, if we were to try and boil it down even further, I'd say a more simple takeaway of the post would be to not worry too much about what type of wattage you are providing your speakers. If you're amp's wattage is within 50% to 150% of your speakers wattage rating, you'll be okay. ***Just make sure to never let your amp's inputs clip and you won't blow a speaker.*** In the studio monitor world, again, wattage specifications are for the most part unimportant. Let me know if you had any questions and we can dive into them.

    Reply
  • adam mielke
    adam mielke 09/03/2012 at 8:04 AM

    Hi Preston,
    I liked the article, but I'm a little confused. If you're turning up the input sensitivity to get more volume, and the amp clips; wouldn't a bigger amp (within the rule of thumb double the rms rating of the speaker) get more volume safely? If not how would you get more volume? Would you have to add another amp and another set of speakers? I appreciate any input.

    Thanks,
    Adam

    Reply
  • Preston Smits

    Hey Adam,
    Yeah, that's true (within the rule you mention). If your loudspeaker can take more wattage, you may be able to get a little more volume by upgrading to a higher output amp. But like i mentioned, this usually only increases output by 3dB, unless you're upping the wattage 4x or more and your loudspeaker can actually handle that.

    Regarding the input sensitivity, I was trying to say that it isn't too little wattage that blows speakers, it is clipping the input that causes it. You'd be fine running a under powered amp to your loudspeakers as long as you don't clip the inputs (it just may not get as loud as you'd like).

    A lot of loudspeaker manufacturers provide a maximum SPL rating. This rating takes into account the loudspeaker's sensitivity and wattage ratings and provides you an good idea of what it will put out (if you give it all the power it is rated for). Using this max SPL rating is the easiest way to find a loudspeaker that will provide you the most volume.

    Reply
  • JD

    Hello Mr Smits,
    I believe your first post was interpretative. The first comment from Mike......well, let me more succinct.........was obviously generated by an intellectually deprived (I assume) man (probably boy) which needs to disparately have his anger wattage checked soon. I think he may be "clipping".

    Reply
  • lafaunda

    hey i was wondering if i have 400 watt speakers , what wattage amp do i need

    Reply
    • Preston Smits

      What Brand & model are they? That could help determine a pairing for you. In general, a 400-600 watt per channel amp would probably do the job well for you. Per the post above, even 200 watts per channel would likely work fine!

      Reply
  • Barry

    Hi Preston-

    Great read-thanks for all the info. I'm considering buying a vintage B&O amp (the beomaster 2400) and pairing it with a modern set of Klipsch bookshelf speakers. Given older amps are significantly less powerful than modern configurations I'm worried about under-powering the speakers which are rated at 100W. The amp is rated for 30W per channel at 4 ohms and 25W per channel at 8 ohms.

    Also the speaker specs list impedance as "8 ohms compatible." What do you think that means, that it can run off both 4 and 8 ohms? The amp has both a 4ohms power rating and an 8 ohms power rating as mentioned above. Which rating will the speakers function at and do you think they will be under powered?

    Anything else I should be thinking about using a vintage amp?

    Thanks!
    Barry

    Reply
  • Preston Smits

    Hi Barry, First, you should know, I don't know much about the home stereo/hi-fi world and mainly focus in the commercial audio realm, but I suppose the physics still applies :) The “8 ohms compatible” probably just means they have a nominal impedance of 8 ohms. (So they're an 8 ohm box.)

    Like I mention in the post, while you'll be only sending 25w (the 8 ohm rating) to speakers that can take 100w, this is not a problem. The main down site is just that the speakers are capable of getting louder than your amp can provide for them. Since you'd have to double 25w 2 times to get to 100w, you could say 2 doubling of 3db is what you'd be missing (or 6db, not that big of a deal).

    Another thing to be aware of about when hooking a lower wattage amp to a speaker capable of higher watts is that if you clip the amp by turning the input volume up higher than it can take (thus clipping), you could damage the speakers. All you need to do to avoid this is to just turn the volume back if you see the clip LED light up!

    I'd love to chime in more about using a vintage amp, but again, the hi-fi market is not my world so I wouldn't be of much help there.

    Reply
  • Alex

    Hi, I dont want to listen too loud in my small apartment room, but still need the quality of sound.
    So my question is, how loud do I need to turn the volume in order to get good enough level of quality in sound?
    You will probably tell me: it depends on the speaker characteristics.
    Fine, then lets say one speaker has the recommended power wattage between 10 and 70 W, and the other has it between 25-75. Does this mean that, using same amp (and assuming the two speakers are of similar sensitivity & ohms), in order to get the best quality sound I would need to turn the volume higher on the 25-75 Wattage speaker?
    Thank you.
    (Actually, the 25-75W speaker is 6 ohms nominal, and the other is 8 ohms - so you may take that into consideration too)

    Reply
  • Preston Smits

    Hey Alex- Not sure what you're referring to in regards to "quality of sound".

    If you mean equal volume level:
    If they have the same sensitivity, the 25-75 speaker doesn't need more wattage/volume to get the same volume level, it only means that it is capable of taking higher wattage. Given the specs you provided, they're probably have a very similar level when given the same amp power.

    If you mean do they sound better at different levels/volumes:
    This is completely subjective to taste. Many people feel sound systems sound better and higher volumes. This is often because at these higher volumes our ears respond differently than lower volumes. Essentially, or ears have a more flat frequency response at higher volumes (google: Fletcher-Munson curves). Be careful listening at these higher volumes though; the range that our ears response flattens out is the same range that causes hearing loss over extended listening periods! But back to the speakers, as far as I know, they will not produce a different output tonal quality at either low or high volumes (within the range they can handle).

    happy listening...

    Reply
  • Alex

    Hi Preston,
    by sound quality I meant the speakers being able to deliver (and for the listener to hear) all the different instruments/sounds/tonalities, distinctly, at lower volumes as, comparatively, at higher volumes.
    As I said, I will mostly listen at lower/medium volumes, and seldom at high volume.

    So, I was wondering, why the seller would recommend a higher starting wattage (the speaker starting at 25 W) and for the other speaker a lower one (10W)? Notice that figure is not the given RMS power of the speakers, nor the peak (dynamic) one.
    In my view, that recommendation would mean that, for best listening experience/sound quality, the speakers should be given the stated range of wattage. Now, my point was, why would that range start at 10W for one speaker, and at 25 W for the other? So I was asking you: could it be because the speaker with 10W starting point recommendation is a better speaker and so will deliver good/quality sound, even though we keep the volume of sound at low levels (not turning much the volume knob, means that we dont feed the speaker more wattage, right?).

    And, correspondingly, would it mean that for the speaker with the recommended wattage range to start at 25 W, we would need to turn the volume knob more/higher, in order to get a similar quality in sound?

    Because, if your answer is negative, than I would ask: why wouldn't the low end (the starting point) of the recommended wattage be the same for both speakers? And, to differentiate them, it would have been sufficient to mention for one speaker a higher upper end, and for the other one, a smaller one.

    Thank you.

    Thank you.

    Reply
    • Preston Smits

      Okay Alex, I get you now. Sorry I didn't catch the question earlier. When a manufacturer provides a wattage recommendation range, they are not saying that you should always be feeding your speaker with at least 10w and no more than 70w. This 10w - 70w range is instead saying buy an amp that has a MAX output of anywhere between 10 and 70 watts. During typical low-medium volume listening levels, you'll be nowhere near those wattage anyway. When you're listening at low volumes, its likely your amp is putting out only a small fraction of one watt to the speaker!

      So, its absolutely possible to listen to quality sound at low wattage (say 0.25watts) on most every consumer/home speaker. You don't have anything to worry about there.

      The question of why one speaker has a lower MAX power range than the other might be due to speaker sensitivity, and it might just be due to how different manufacturers produce their specifications. One company might say they feel the listener to be able to play back the speaker at at least a max of 102dB where the other company says they feel a 98dB playback level is fine. Something as simple as this might be why one would recommend at least a 25w max power amp, and the other only a 10w max power amp. Manufacturers are too often casual with their specs, or let their marketing department influence how they show specs more than their engineering department. ;)

      But again, if you're listening at low volumes, you likely never push past using 1-2 watts anyway!
      I hope this helps.

      Reply
  • Charles Michael
    Charles Michael 01/16/2013 at 8:05 PM

    Preston you do realize the reason why a 200 watt monitor will sound louder than a 300 watt monitor is because the 200 watt monitor has a higher distortion level than the 300 watt monitor and distortion equals NOISE! That's why you have to be very careful when you listen to really high end monitors because they have very low distortion at high volumes and can be misleading because they don't sound super loud compared to a cheaper system at full blast!

    Reply
    • Preston Smits

      Hey Charles, I totally agree! Distortion can really lead to a higher perceived loudness despite a quieter volume due to a "harsh" quality of sound. Frequency response can also have an influence on our perception of volume. There have been many experiments that showed if you don't have a good balance across the spectrum, it is perceived as sounding louder. For example, listening to a banging cymbal by itself often sounds loud, but get the whole band playing along with that cymbal, and you might not thing things sound so loud anymore. Its a very odd phyco effect. Also, like I talked about in the post, just because a monitor has higher wattage doesn't necessarily mean it is louder since you have to take speaker sensitivity into account. And even if they have the same sensitivity, a 250w to 400w increase is only technically a around a 2dB-SPL increase in volume. So I could see how a the physio-acoustic effect of distortion could cause the lower wattage speakers to sound louder. Thanks for your post,
      preston

      Reply
  • Charles Michael
    Charles Michael 01/16/2013 at 8:11 PM

    A cheap 200 watt monitor compared to a 300 higher end monitor. Just wanted to clear that up! I have a pair of cheap event monitors here that are 250 watts and they sound loud compared to my Focal Twins that are 400 watts!

    Reply
  • Alex

    One more thing: the right front speaker will be placed an inch distance to front wall, while the left front will have half foot behind it, and 3 inches distance to left wall.
    The center will be1 inch distance to front wall, placed right between the window and the radiator(for room heating) - by the way, will this affect it?
    The surrounds will be placed on the left/right walls, right on the corners and at 1 inch distance to rear wall.
    Listening position will be on a sofa against the back wall, between the surround speakers.

    Thank you.

    Reply
  • Francishooper@gmail.com

    I had forgotten about this info from school. Very well said, it really cleared things up for me, thanks!!

    Reply
  • behzad

    hi Mr.Smits

    excuse for my English!
    i have big hall with 20 * 10 meter dimension the height is 3 meter and the wall is woods panel.
    in this room placed 160 chair in 3 row. i want to know how many wattage i need for PA and also how many speaker i need and also the space between the speakers.
    i searching in internet very much but i cant find the formula for calculation these parameters .

    thanks for your help
    behzad

    Reply
    • Preston Smits
      Preston Smits 03/05/2013 at 2:43 AM

      Hi Behzad. It's hard to say without knowing more & seeing the room. If you really want to properly install a PA in that room, I would suggest you hire an audio contractor to help you. If you don't have the money to do it that way or just want some cheap advice, you could probably get away with just using a consumer grade PA system like you'd find at most music shops, such as one of the ones on our store here:
      http://www.sonicsense.com/shop-by/live-sound.html?is_package=sonic_sense_packages&manufacturer=jbl&manufacturer_is_open=true&mic_mono_stereo_is_open=false

      I think the PRX series would be a good bet for you.
      best,
      preston

      Reply
  • Lexxy

    I have been wondering aimlessly in space wondering how in the hell i can achieve 120,000 watts for a pa system for a music festival with an audience of 10,000-
    I am an audio engineer final year student and have been given the following info to try and find appropreate line arrays for this situation-

    12w per person X 10,000 people = 120,000 watts

    Currently i have 22,400 watts only !

    Im already running

    12x600w high/mids
    4x800w mids
    6x2000w subwoofers
    (Rms)

    Do i need more powerfull speakers to reach the 120,000w mark?
    Or am i completley calculating it wrong?

    It seems that to achieve that many watts i will need to bring 5x the amount of equipment i already have!
    Am i at all on the right track-


    I just wanted to mix music, noone said thered be maths involved :(

    Reply
    • Preston Smits
      Preston Smits 05/13/2013 at 6:35 AM

      Hi Lexxy,
      In my experience, when designing systems for 1-10 thousand person audiences, typically it's best to use a max SPL goal through the audience area rather than a watts per person. Max SPL is a more meaningful goal since people hear sound pressure levels, not watts (like explained in this post). Pick a Max SPL goal for audience area and try to stay within that goal plus or minus about 3-5 dB around the goal for the entire audience area. If you are using line arrays, it's a good idea to use the array of choice's line array calculator function (such as JBL's "LAC" or Meyer's "MAPP" software). These programs allow you to set up your configuration and predict SPL level variances across the listener plane. Typically the calculators assume you are providing the boxes their recommended power per channel. So, once you get it looking good in the calculator, you can just add up the boxes, and what they require (spec-wise) per channel in order to get the proper amplifier count (and thus power requirements "wattage count").

      If you're not using line arrays, then you can use the inverse square law in order to calculate the SPL for listeners at different distances from the loudspeakers. For example, if I have a trapezoidal loudspeaker with a Max SPL of 142dB at 1 watt at 1 meter, then add 3dB for each additional watt up to it's max wattage. Then subtract 6dB every time you double the distance from that initial 1 meter to the listener's ear. Also make sure to take into account the 3 or 6dB down points (off-axis levels) of the speaker's horns.

      Best of luck!

      Reply
  • Jay

    hello Mr smits
    I had some Q for a system we need for our temple
    its a donation
    PA system for their live programs
    We have selected the
    2 JBL SRX 725 (RMS 2400W)
    2 JBL SRX 728s (RMS 3200W)
    2 Crown xti 6002 (Stereo, 4 ohms (per ch.): 2100W) for the subs and the tops
    1 - DBX DriveRack PA+
    1 - yamaha 124 cx mixer

    would this amp be under powering the speakers ??
    i dont want them to blow up their speakers with too much power on the amp tht they can use
    is this a good setup?

    Thank you for your help
    JAY

    Reply
    • Preston Smits

      Hi Jay, I think your setup will be fine. Even though the amp is slightly less powerful than the loudspeakers are capable of handling, its a pretty close match.

      Reply
  • Richard

    Hi basically i am trying to make a portable loud speaker system i have a sony car stereo and a 600 watt max p.a yamaha speaker what amp do i need and what sort of wiring do i need and how do i earth it better cus the car stereo keeps turning off and on cause i am running it on a 12 volt battery please let no a.s.a.p thanks

    Reply
    • Preston Smits

      Hi Richard, there's a lot of factors that you bring up that are probably a bit to complex for just a reply in this thread. Although, one of my co-workers is writing a post soon that deals with much of what you're asking about. Check back in a couple weeks, he may have some answers for you.

      Reply
  • danny

    if the receiver has no clipping led, is it obvious by sound alone when its reached that point? also, i have an old powerful pioneer amp rated conservatively at 130 wpc rms but my dynaco a25 speakers are 35 watts on paper. does that mean i should only go about a quarter of the way on the volume knob to avoid blowing the speaker with too much wattage?

    Reply
    • Preston Smits

      Hi Danny, if you're a bit of an audiophile, and listen intently to your music, you'll hear when it starts clipping and be able to back off in time to keep the speaker from getting damaged. Although, since you are using a powerful amp, I would recommend being careful about turning it up too loud to quickly considering you're amp's ability to fry a driver!

      Reply
      • pandu

        HI good mornning I want need your help pls one big hall so 2500 pepole capasite every day some speech progrma going on pls tell me how to setp wich speaker watts beast compny

        Reply
        • Steven Leccese

          Hey Pandu,

          Thanks for reaching out. That's a fairly big space, so you'll want a powerful system. Are you looking at getting passive speakers with power amps or powered loudspeakers? You can check out some of our powered loudspeakers here to compare the sound quality and features. If you have any more questions, one of our in-house engineers may be able to give you better assistance over the phone or e-mail. Give em a call at (303) 753-0201 or send them an e-mail at support@sonicsense.com . Hope this helps!

          Reply

Items 1 to 20 of 31 total

Page:
  1. 1
  2. 2
Leave a Reply