Distortion Talk

Kchill

I have read a lot of concern about distortion on here and it made me wonder about the following. Maybe one of the pro's can chime in on this.

If your amp is underpowered for the speaker, how can you have distortion?

I have heard pops and crackles just from watching tv when the cable seems to mess up. While playing music I have a cut off thing in my reciever that will not allow me to play it for too loud and too long.

So when should I or anyone else should be concerned?

curved

Read this:
http://en.wikipedia.org/wiki/Overdriven

Kex

Kchill wrote: »

... So when should I or anyone else should be concerned?

Your AVR247 is a great receiver, but the RTi10 are hungry speakers (if you had RTi8, I would have said you probably didn't need to worry). If you used EzSet/EQ to auto-calibrate, I would say you're proba bly safe up to the -15dB position for 5.1 listening, maybe even as far as -10db, but I would stay away from anything higher (the scale is probably -60 to +9). It should become obvious in that the sound starts to become a bit "noisy", rather than just smooth but loud.

If you have an SPL, you'll certainly be safe up to 85dB, after 90dB, things might start to get fuzzy. That'll do for a rough guesstimate!

kweb

Not to sound stupid but can someone explain the whole -3db -6db +3db thing thank's Ken

Kex

kweb wrote: »

Not to sound stupid but can someone explain the whole -3db -6db +3db thing thank's Ken

It's not really stupid, but it really doesn't make all that much sense! Most newer equipment uses a volume scale that, when you turn the volume knob, adjusts the display in dB increments. I think the idea is that 0dB would be "reference level" or 85dB, IIRC, on a SPL meter (something to do with THX, AFIK). If you adjust the 0dB setting to reference, using an SPL meter, then that would be a normal listening level for most people, at least for movies, and anything over or below that would be a +dB or -dB of "x". With any decent receiver, any -dB setting should not risk distortion.

That's fine, but some receivers, including harman/kardon, actually adjust the levels automatically when you use the calibration feature included with these devices, so 0dB might not actually be "reference level" , or 85dB, for these devices (that's actually very loud with pink noise, so a PITA to set for all speakers of a surround sound system).

Anyway, I think that's the logic of it, more or less.

curved

Kex....that's probably better than I could do.

Those 10's are power hungry. I wouldn't push it much past -15 to -10 or you could end up damaging the woofers....it's not going to be something that happens overnight, but over time, it's not a good thing.

MillerLiteScott

Actually driving the RTi10 hard, with not enough power, works the mid driver more than the woofers.

And the amp clipping will probably damage the tweeter. IME.

YMMV.

Kex

MillerLiteScott wrote: »

Actually driving the RTi10 hard, with not enough power, works the mid driver more than the woofers.

And the amp clipping will probably damage the tweeter. IME.

YMMV.

Agreed: it's the tweeters that risk damage from a lack of power, not the drivers and woofers ...

Ron Temple

It's the peaks that kill you...

The 10s sensitivity is 89dbs from 1 watt @ 1 meter. At 3 meters (probably about average in most rooms) the speaker will put out 83dbs from 1 watt. It will need 10 watts to play at 93dbs and 100 watts to push 103dbs. this doesn't account for impedence drops, room, boundary and colocation gain, but you get the idea. Reference level is 85dbs average, but allows for 20db peaks for all channels except the LFE (which allows 30dbs). So you can playback at reference using 5 or 6 watts, then a full blown peak comes along and you need an instantaneous draw of 500-600 watts. So playing at 10-15dbs below reference with that HK is probably about right.

Kchill

Always good to see the great Ron Temple chime in. I'm still a little clueless, are people saying that the reciever itself has a distortion level if you crank it up loud. Because that would not make sense to get an amp that cranks loud only to get the same distortion.

To make this clear, if the reciever puts out 100w...and the speaker can handle 350w then what's wrong with cranking it up?

I will say that the tweeter theory makes sense but then I will counter saying that more power should pop them.

Or are people saying that amps give "clean" power, that's cleaner than the reciever built in amp?

Ron Temple

Kchill wrote: »

Always good to see the great Ron Temple chime in.

Thanks...but, I'm just an intermediate in this hobby. There are many far more knowledgeble folks on this and other forums.

I'm still a little clueless, are people saying that the reciever itself has a distortion level if you crank it up loud. Because that would not make sense to get an amp that cranks loud only to get the same distortion.

To make this clear, if the reciever puts out 100w...and the speaker can handle 350w then what's wrong with cranking it up?

I will say that the tweeter theory makes sense but then I will counter saying that more power should pop them.

Or are people saying that amps give "clean" power, that's cleaner than the reciever built in amp?

The power recommendations listed, min-max, are based on minimal performance at reasonable volume to extreme performance where you're reaching the speakers max output, driver xmax capability. Giving it more than 300 watts will probably damage the speaker through overdriving it. Using an amplifier that exceeds 300 watts RMS doesn't mean the amp uses it's max output capability. The amp only uses enough power to drive the speaker at the selected volume. The rest is headroom. In the formula above, a 500 watt amp driving a 10 to 103dbs is still only using around 100w. If a 3db peak comes along in the program it's pushes 200w. The headroom is to handle those peaks cleanly without clipping the amp.

Clipping the amp is bad. The squared off wave distorts the sound coming out of the speaker. A hard clip can damage the amp, blow the tweeters and fry the voicecoils on your drivers.

Your HK @ 50w has some headroom. It's got caps that can deliver up to 35 amps for instantaneous peaks. However, if you're running balls out ~ 100dbs for any length of time, you will clip the HK and distort during peaky passages. Those caps will discharge quickly. No more headroom and probable damage. That's why you don't crank it past it's capability.