Speaker Power Handling Explained
ฝัง
- เผยแพร่เมื่อ 6 ต.ค. 2022
- How to measure the power handling of a speaker
DIY Audio courses: audiojudgement.com/courses.html
Music Credits:
"Werq" Kevin MacLeod (incompetech.com)
Licensed under Creative Commons: By Attribution 4.0 License
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Hi, I wanted to let you know that your videos have helped me a ton. Three months ago I began into all of this, I started designing and building a small PA system, two 'column' speakers and two subwoofers. And by now I'm already digging into phase alignment of the whole system in different venues. I want to thank you a lot! Your videos were very helpful along the way and now I got the best sounding system I've ever heard. And this topic was something I haven't had clear, I didn't really know if it would be ok to let the amp run at full gain into these speakers.
Another excellent video, as always! BUT, :) I just wanna point out that Xsim calculates the amp power based on the amp output impedance and is actually a very weird thing to do because its not how it works. For example(and for simplicity) take your first example, where you have a 8 and a 4 ohm resistor. You set up Xsim to output 60W to a 4 ohm load, and it does exactly that, you can see on the 4 ohms resistor, the power dissipation is 60 watts, great. Its 15.49 Volts at the amp output terminals, ohms law tells you that is indeed 60 watts at 4 ohms. You can also see in Xsim, that the 8 ohm resistor gets 30 watts, and that also checks out with ohms law at 15.49V. But, in reality the amp actually sees the two resistors in parallel, and for this example it is 2.67 ohms. It puts out 15.49V, so the total power that is coming aout of the amplifier is actually 90 watts, the power dissipation of the 2 resistors added. I know you know this, but maybe next time when using Xsim in your videos just mention this because it can be misleading for newbies. I don't know why Xsim works like this or why there is no option to see the total output power of the amp but I can't complain as its a free software and I'm very glad that it exists in the first place.
I think the most important thing to realize about speaker power handling in home audio is this: Don't think too much about it.
It's also a way to tell "newb" speaker builders apart from more experienced or knowledgeable ones - the newb will always rave on about power handling, and it will be his first consideration when selecting a woofer, because "more Watt equals more loud, right"?
All the while the "pro" will probably be able to tell you many parameters of his favourite woofer (Fs, Qts, Sensitivity etc.) even when half asleep at 2am, but there's a high chance he won't be able to tell you the power handling figures right off the bat at any time - his response might just be what Rolls Royce tells you about the Horsepower of their cars - It is _sufficient_ .
Pretty much all home audio woofers will mechanically distort long before reaching their own thermal limits, and, given you applied some common sense while selecting it and did not mess up the filter circuit, the thermal limits of the tweeter, or whatever is doing the high and/or mids.
I like that you addressed this age old question! This was a topic of debate as far back as I can remember. Way way back when I was younger, the general rule of thumb was to choose an amp with double the wattage capability of the speakers. The theory being, (as you alluded to), that the amp or receiver needs to have the capability to electrically control the speakers at their max, taking into account plenty of dynamic headroom. In practice, this works and as you also mentioned, speakers are more often damaged by under powered amps.
Taking that practical logic and applying it to building speakers purposely built for high power/high SPL output with low distortion, I've found that the amp can safely be larger than most people's budgets allow anyway.
As an example: A typical high power speaker may resemble something along the lines of a few home speaker projects I've done recently. Take the Jensen CS 315 RestoMod I did... 300 watt RMS/ 600 Max woofer, with a 50 watt RMS / 100 watt max mid-range, and a 30 watt RMS / 60 watt max tweeter... This would seem to be a 380 watt RMS system with max of 760 watts. Or, conservatively 300 watts if limiting the advertised power to the woofer, (because most of the energy is soaked up by the woofer), as silly as it sounds, powering these with my NAD that's rated at 130+ watts per channel RMS, they're technically underpowered. They still sound good, especially indoors at home, but if I were to push these harder, in a huge room or outdoors, I would want an amp of at least 800 watts RMS as a rough estimate.
I know this because I've used similar designs for high output in banquet halls, outdoors, etc. and smaller amps (for example my old Harmon Kardon PM 660 with 80 watts RMS), and they were underpowered and underwhelmed outdoors and in big spaces. Actually what I ran these similar designs with in those applications, were 2500 Watt stereo RMS pro amps, bridged to 4000 watts, 1 per speaker cabinet. With those amps, the speakers would play at or near Max output in the 120+ Db range for as many hours as needed. Just testing them I'd let them play for a minimum of 8 hours non stop at full power, before I'd even sell them to a customer.
In use, even at these relatively insane power levels, they'd run for an entire event at or above these levels, without audible distortion.
With all that being said, I have always been a firm believer in plenty of clean power on tap for speakers. Just a WAG but my pseudoscience theory is that it's because we listen to music, which has continuous deviations across the frequency and output level, unlike running a continuous pink noise tone burst. This allows a speaker to safely operate even at seemingly crazy high power, because thermally and electrically they're very rarely at any given max power state for more than a few milliseconds when playing music.
I wouldn't recommend overpowering them with a continuous full range tone, but with music, which is constantly changing frequency and output level, it's fine. I've done it again and again.
It's ironic, because just within the past couple of days, I was testing some vintage Realistic speakers that have 20 watt woofers and 10 watt tweeters, with my NAD and they sounded quite good despite me operating them with a receiver that's capable of 4 times the speaker's power handling.
The old theory behind this, (and intuitively it seems logical), is that it's more important for the amp to be able to "control" the speaker. Constant musical bursts over and over, and the mechanical limits of the speaker in combination with the speaker always fighting itself to return to its neutral state, requires amplification that can move them in and out as needed, without allowing the speaker drivers to become mechanically unstable during music playback, which leads to clipping and distortion which will absolutely destroy a driver regardless of its power handling.
Whew that was a lot of comments I know... But an important topic. Even if mathematically I'm completely wrong, in actual application, I know this to be true because I've done it over and over. In all the years I've been doing this, the only time I ruined a driver, was from playing it loud while underpowering it.
Thanks for the illustrations and explanations and I agree with you that more power is better than not enough, especially if the drivers have a lot of mass or big motors, (often the case with DIY speakers Vs store bought speakers which employ much smaller motor structures in their drivers).
Maybe a cool idea for a video would be to see what happens when high power amps are hooked up to low power speakers and vice versa.
easy!
1) buy two pairs of the same speaker
2) turn up the volume till it blows the first pair
voilà! you now know the power handling of your speakers
I agree with everything! Good job !
Very helpful, thanks
well done bro
interesting. it looks like xsim uses white noise to drive the drivers (constant power density spectrum wise) which may be good for testing maximum power handling in laboratory tests but music is more like pink noise and so midranges and tweeters are drastically smaller than woofers in power handling.
Life was simpler 10 minutes ago when 50+50 equaled 100 😔
How about a discussion on amp power/sizing when the speaker is to be bi- or tri-amped ? Obviously some of the same criteria hold and some doesn't. Should speaker sensitivity also be factored in ? Perhaps type of music ??
TX for the good work!
Any budget build suggestion for (centre channel speaker 8ohms.) normally all 2 way crossover design ( 2mid woofer , 1tweeter.) are in parallel configuration . can use series configuration and what'd final impedance.
I am trying to drive a Speak from a 1951 phonograph,, the Parts list says 2.5 watt speaker. so would this work with current Stereo at 8 ohms ??
Salutare, ma poti ajuta cu un proiect? Doresc sa imi fac 2 boxe de raft pentru reciverul meu (sony str dg820), din cate stiu are 7 canale a 110w . Ai utea sa imi spui ce difuzoare, crosover si schita pentru incinte, doresc sa le realizez singur.
Speakers are killed by distortion rather than power.
You are right when you say that it is our good judgment that decides this.
My question is if a woofer is rated at 100W RMS, two of them in parallel should handle 200W RMS, true or false?
True. Same thing if you wire them in series. You just need a bigger amp to push out 200W at a higher impedance.
man I got 16, eight ohm speakers 15 watts each...... i need to wire them together to handle at least 100 watts, and no need for less than 16 ohms. so far my math is 8 speakers in series parallel with 8 speakers in series.
theres 16 ohms but im been retired . trade school if I remember loads in series power divides? so each speaker will handle a small portion each?
15 watts 8 speakers in series
is 120 watts total
but 32 ohms.
Best way to test them is to put full power to them on low volume, then slowly turn it up and wait for first sign of distortion. You now know.
𝓅𝓇o𝓂o𝓈𝓂 😂