When shopping for speakers, one of the specs normally listed is its recommended wattage. Well, if you are blasting your speakers, how do you know if you surpassed the maximum limit?
I kinda figured that. What was throwing me off is that my amp is rated for 40 Watts of continuous power per channel. Both of my speakers are recommended for 10-80 Watts. I start to hear that strain when the volume control knob is around 40-50% of max setting. I was thinking that if the knob was halfway, then that would be 20 Watts.
What kind of amp is it??? The amp itself may be the item that is becoming strained. Watt ratings dont mean a whole lot. 75 percent of audio equipment have false ratings.
It is an Onkyo TX-900. The speakers are JBL 2500. Fairly old but adequate for the small room they are in. I just would like to blast my speakers once in awhile. The 2500's are only 4.75"
Yeah, I would say the amp is reaching its limit, or the speakers are. An onkyo that claims it does 40 watts wont. It may do 30. The JBL's should be able to handle more than 30-40 watts. How loud is it getting before your hear distortion?
My volume control knob is around 50% of its max setting. I can start to hear the music break up a little. For a regular size bedroom in a duplex house, that is a decent decibel level. But I want to install garage speakers and I will probably need larger speakers, I'm thinking. I was thinking that my current speakers just can't handle it. They are only about 5" diameter. By the way, that's quite a setup you got there.
Thanks Daniele. Im thinking if your going to be putting in larger speakers that you may have to upgrade your amp. Unless you get speakers that have a high Sensitiviy like 94db or something. Even so, if you want to crank them at a garage party level, your going to slam some more power into them. You 40 watt amp will become strained.
NAD is probably out of my range and most amp's I see today are home theater systems. I am only using to play tuner and cd player. Recommendations on a little more powerful amp? I like Onkyo's black and simple look.
What was throwing me off is that my amp is rated for 40 Watts of continuous power per channel. Both of my speakers are recommended for 10-80 Watts. I start to hear that strain when the volume control knob is around 40-50% of max setting. I was thinking that if the knob was halfway, then that would be 20 Watts.
Two things. First, There's little real difference between the 80W max recommended for your speakers and the 40W of your amplifier (3 dB), given that those are coarse numbers anyway.
Second, the relation between the volume dial setting and max output is almost never to be as you say. First, you can reach peak output way before turning the dial all the way. Half sounds about right to me. Second, turning the volume dial down is not proportional to the power output. Turning it down a few ticks might be half power, a few more more ticks would be a quarter, a few more ticks would be an 1/8th. It's a log scale.
Thanks Peter for explanation. I didn't realize that the volume control knob was a logarithmic adjustment of volume. I thought it was linear. It would be nice if you had dB gauges so you can see the power levels transferring to your speakers. The amps that have these gauges are too much for my pocket.
Some, most, volume controls on consumer mass market equipment are log taper or "audio" taper which is not consistent from step tp step. Typically, substantial amounts of increase will be allowed at the lower range for the impression of "lots o' power". However, most higher end equipment uses a linear taper volume control and each step is defined as +1dB or +1.5dB depending on the vc. However, the input voltage is relative to the oputput voltage and this "+1dB" might not be equal on all inputs with a linear taper vc. It will be consistent from step to step however.
I didn't realize that the volume control knob was a logarithmic adjustment of volume. I thought it was linear.
Mr Vigne replied:
However, most higher end equipment uses a linear taper volume control and each step is defined as +1dB or +1.5dB depending on the vc.
So that would be linear in log space (like I said).
Daniel also wrote:
It would be nice if you had dB gauges so you can see the power levels transferring to your speakers.
Modern receivers do have a negative dB scale displayed, where 0dB corresponds to maximum output given a full input voltage. That's when you realise how little power you need sometimes.
Yeah, MAC's do have meters...those blue-lit gauges are really cool. I checked out those already. However, they are very expensive for my pocket. I thought of something simple to just get a rough idea of the power transfer to a speaker at a particular volume setting. Perhaps you could measure the voltage across the speaker inputs that is playing a particular frequency (perhaps an organ note). Power could be determined by calculating voltage divided by impedance squared.
oops...I meant voltage squared over impedance (which is almost an unkown value, since you would need to know the reactance of the loudspeaker coil to a particular frequency - perhaps the nominal 8 ohm value is for a standard test frequency)
Sorry for getting technical here but I am definitely missing something here (feel free to try this at home). I checked a speaker for its resistance and got 5 ohms. So I am assuming that the nominal 8 ohm value comes from the reactance of the speaker coil to a particular frequency. I played a 1kHz sound at 50% on the volume control. I measured 1.2 VAC. Well, apparent power (which won't be that much higher than real power) would then be 1.2 squared * 8 ohms. That only comes out to .18 Watts. Doesn't seem like a whole lot of watts at 50% volume control.
Pretty much what you checked on the speaker was its nominal resistance. You didn't check the impedance of the load at any given frequency I assume. You'll need to run a frequency sweep while watching the Ohmmeter rise and fall with frequency. If all you're using is a test tone sweep from a CD and a VOM, this will be very rough measurement but will give some idea of how much variance there is between high and low impedance points.
To measure your voltage output, the amplifier has to work into a load similar to a nominal speaker load. Your VOM doesn't represent any where near the load of a speaker. Sticking the probes of your VOM directly onto the speaker outputs of your amplifier is a pretty good way to blow up your VOM.
The position of the vc tells you little about the actual amount of wattage the amp is producing.
Jan, I played only 1 frequency to the speaker. I couldn't check impedance of load. But I assume it has to be something larger than the 5 ohms of resistance I measured. I can't imagine it being something larger than 20 ohms. I wasn't using the VOM as a load. I was testing the voltage across the speaker in's while the speaker was acting as a load on the 1kHz sound I was playing.
Please, Peter! If you want to fight again, go ahead and say what you want to say and stop being a child about it. Otherwise, contribute to the thread or shut up.
Well Pete, yes and no. Applying the meter as a load across a 110v outlet is a lot different than introducing the meter to a driven circuit. Amps hate that.
I'm going to put you on notice right here, PG. Though I doubt your comprehension skills will allow you to understand something very, very simple.
I am not going to stretch this thread out to 300 posts just so you can hold your small minded, immature grudges. If you once again start something over a simple phrase, I will end it quite quickly and you will not come out the better for it. I am very tired of your childish behavior on this forum.
I wouldn't put a meter on the resistance setting on the output of an amplifier, but what is wrong with the voltage reading on the output of an amplifier without a speaker load? What can possibly happen to the meter?
I would agree to caution. Sticking metal probes into the amplifier output will be very nasty to the amplifier if the probes touch and the amplifier gets shorted. But your sentence simply said it was a good way to blow up a meter. I don't think it would do much of anything to the meter.
If you wrote too quickly and that wasn't what you meant to write, you had a good opportunity to clarify when I simply posted a question marked instead of "putting me on notice".
When a manufacturer says a speaker is rated for so many 'watts', that is the most meaningless nonsense ever. How is that number arrived at? Music is so dynamic that RMS power doesn't play into it. A speaker that can take 100watts RMS of pink/white noise with certain frequency mix in specified ratios, will take probably 3x or 4x that in music as average power. On the bench, for a single cycle, maybe even more. Unless you must have a system that will go to 11, ignore that number and use your ears. I blitzed the Midranges on my 1st pair of 3-ways this way, and never had above 40rms......
I will admit to smoking my cheapo meter yesterday, trying to measure current....which must be measured in series with the load. For a voltage measurement, which is measured in parallel, I suspect the meter will be protected by its VERY hi (especially compared to speakers) input impedence. Old Simpson 260's, the 'voltohmist' model were 10kohms/volt while modern DVM are something like 11meg.....across the board. Problem is that they don't respond quickly enough for music, but may for sine wave....use the peak hold function. If you GOTTA experiment with current, use the 10amp connections! Best of luck.
To measure your voltage output, the amplifier has to work into a load similar to a nominal speaker load. Your VOM doesn't represent any where near the load of a speaker. Sticking the probes of your VOM directly onto the speaker outputs of your amplifier is a pretty good way to blow up your VOM.
My sentence implied caution. A wise course to pursue.
JV's sentence implies he doesn't really know how to use a meter, since there is no possible risk to the meter, but rather to the amplifier.
With regards to discussion on the use of VOM, I was not checking resistance or current. I was checking voltage across the speaker in's while the speaker itself had a load on it. If I was measuring while playing music, surely there are voltage spikes that might be higher than my setting. For example, I was using a 10VAC range and my deflection was no higher than 2VAC. However, I am sure that it's possible to have spikes greater than 10VAC and that is what could be the threat to the meter. However, my deflection did not vary as much.
"When a manufacturer says a speaker is rated for so many 'watts', that is the most meaningless nonsense ever. How is that number arrived at?"
I wonder if they run tests at certain frequencies. You can monitor the sine wave of the signal in vs signal out and check for distortion, gain, etc. When I played a 1 kHz signal on only one speaker (from some website, unknown volume strength and computer volume controls up), I measured 10VAC at 15 out 40 volume setting. That's about 12.5 Watts using the 8ohm nominal impedance standard. It looks like I could have reached 40 Watts (amp rating) at 20 volume setting. The curve shoots up very fast for one frequency. However, the curve for playing music appeared to rise slower.
Most (many?) DVMs (VOMs are history, by and large) simply won't respond quickly enough for a audio signal. Even a meter billed as 'true rms'. You need a SCOPE, and one with a 'capture' function preferred. I suspect that these days, of cheap, fast memory, you can get a scope that will record several seconds of trace for later playback, but I am sure of that. As for an AMP being a hazard for a meter, this is a non-starter, if the meter is left on the higher voltage ranges......The input impedence is Very high. If it were otherwise, how could you measure the voltage at your outlet? That represents 110 at 15 amps...give or take, that's certainly enough to fry a meter, if were going to happen>> But, music won't give any meaningful readings. Sine waves, using a true RMS meter is probably better. I am on thinner ice, here, never having the cash for a good meter (Keithly / Beckman / Fluke) and not having a sine wave source, either, like a signal generator.
If you want to play, replace the speaker with a good 8ohm, 10 watt wirewound resistor. This sucker is gonna get HOT, so don't set it on the table! try to mount it off the surface. You will have a 'duty cycle' with this setup, so let it cool between tests. You can't leave it on for more than a few seconds at a time, just to see how fast it heats up. Take this one slowly. Ohms law will then allow you to compute watts. The Rives audio CD will provide test tones, as will many other sources.
Be careful with this one, that resistor will get REAL hot. Your amp, may, as well....keep an eye on this, just long enough to satisfy your curiousity. You have no audible means to analyze distortion, unless you can plug some headphones into this, to monitor the output? Just a last thought............
I had a Fluke scopemeter for about 2 weeks, then had it ripped off on a service call and never replaced it, wishing I had have done so now. My 97VI meter not useful as it has a bar graph analog function only.
Somebody here posted about having 10 or so scopes for cheap, did anybody else see that?
Can't find it again.
My Gerard analog meter was great for a long time, and was a vintage piece as well. I never saw it after the divorce all those years ago. Sigh.
I hesitate to contribute to this thread since there are a couple of characters on here who both seem more interested in their own little war than anything else.
Daniel, I disagree with Nick's response to you I'm afraid. You asked:
"if you are blasting your speakers, how do you know if you surpassed the maximum limit?"
And he said:
"Your speakers will start to strain, sound thin and you will hear distortion."
Actually, no, or rather it depends.
If you are truly blasting your speakers and you go beyond their maximum power handling ability, you will hear the speakers 'pop'. The pop is caused by the speakers' drive units hitting their end-stops. Provided the amplifier is still operating within its performance envelope, you will hear no distortion or anything else until the pop since the speakers' drive units should be working correctly (acting pistonically) until they pop.
However, if the amplifier hits its limit before the speakers, then it will start to distort which you will hear in the way that Nick described.
In fact, the more dangerous of the two situations is the latter. So long as the speaker is driven cleanly without distortion it should be alright. If you're driving it so hard that it hits the end-stops and pops, then you will hear that distinctly and most likely rturn down the volume. However, if you simlpy keep turning up the volume and accept the distortion, you are trying to make a speaker do very difficult things - not to act pistonically - and you could break it.
JV: "My sentence implied caution. A wise course to pursue."
PG: "JV's sentence implies he doesn't really know how to use a meter, since there is no possible risk to the meter, but rather to the amplifier."
So, now, rather than being helpful, you'll sit on this forum taking cheap shots at me; eh, PG? All due to your lack of comprehension skills once again and your enduring grudge against me.
If you have an analog meter and you use it on the incorrect setting or range, there is possibility you could damage the meter. Digital, auto-ranging DVOM's minimze the risk. If you are unfamiliar with the meter and how to use it, there is the possibility you could damage the meter - or the amplifier. You've been given examples of how people have blown up their meters by doing something they shouldn't have done. Not enough for you.
You agree to caution but that isn't enough for you. You've got to get that hit in there.
Even Norm Abrams advises caution because he knows people don't pay attention, don't read owner's manuals and think they can do things they can't. And they get hurt or damage equipment. Anyone who is unfamiliar with the equipment they are using risks something. Anyone using a piece of equipment in a less than intelligent manner risks something. That's what you should have added, PG.
JV: "My sentence implied caution. A wise course to pursue."
If you wished to be beneficial to the forum, PG, you might have elaborated on caution. Instead, it's easier for you to take a slam at me. If you agree to caution then the rest of your posts spent trying to prove otherwise are unnecessary.
Grow up, PG.
Now, please, don't take another post to say how horrible I am or how I do this or that. The thread is about an issue other than that. Contribute to the thread or not at all.
Frank, you are very correct. I can drive my speakers to the hard stops without any amp issues. And at that point, the Classe is running 400w advertised, the Psb's @ 3.2ohms rated at 250w. All paper.
The Monitor Audio's Silver 8i are a more benign load, the amp runs 200w into 8ohms, but more responsive. I havn't maxed these out, and don't need to try.
A small amp is a curse without restraint. Never, ever underbuy on power, for listening at any level.
And Frank, if you shy away from posting around the personal issues here, I will be dreadfully disappointed. Ja?
Take Jan's litle setup for example. No max SPL's, little Rogers speakers and Mac 60w monoblocks. Lots and lots of amp for that. And for the Spica's and the Ziggie's.
I have a little more power than that, Nuck, but never needed in my case. The tubes clip graciously and forgivingly when pushed. The 3/5a's are infamous for very quickly sending the user toward the volume control as a big drum thwack will smack the voice coils long before the amp distorts. As in all things, caution is advised and knowing your equipment is essential to not blowing stuff up.
"What are the two of you going to have your own reality show on cable?"
No, just thinking together. Since so far you guys have swallowed all the BS we've posted about improving your system, we were just figuring out what would be the most hysterical thing to suggest next. I'm leaning towards ... plumbing parts!
