THD percentage and dialogue quality

joeygrand3

I have *85 Watt RMS@8 ohms Yamaha A/V Receiver where the specs read THD of .06%. After doing some research comparing other receivers I find that .06% is a good spec. My problem is that when I go to listen to Systems at Circuit city or Fry`s, the set-up that they have, which is similar to mine always sounds better. I have Polk Monitor 30`s for my mains and surrounds and a Polk CS1 center. I`m also using a Velodyne woofer. I spoke to the sales rep, who sounded like he knew what he was talking about. He said to get a clearer dialogue from your home theatre, I would need a receiver with a low THD. Isnt .06% a good THD spec. Please advise, I`m starting to think that I may have to upgrade the speakers. Maybe a better center. Thanks for any advice.

Ricardo

I've never paid attention to the specs of my receiver, and have no idea what THD means.....I'm sure that sales rep doesn't either.

If your problem is with dialogue, you can try a beefier center, and maybe some external amplification.

Willow

Have you calibrated your system ?

Specs....hmm what are those ... I say don't worry about specs unless they are those of dust and very large !

bknauss

Specs can vary widely from company to company due to no real set of standards on how to measure those specs. Sure, I can have a really low distortion measurement, but I might have cheated in one of several ways. As just about everyone here suggests, demo and let your ears decide.

On another note, 1% THD is about the threshold where most people can start hearing distortion on a sine wave. If you're listening to music, the threshold can jump up to 10% based on the listener.

joeygrand3

Thanks for your input. I feel that I may get better results on the quality of dialogue by upgrading my center.

RuSsMaN

The human ear cannot discern any less than .5% THD, anything under that is irrelevant. One half of one percent.

Usually amps with REAL low THD have TONS of negative feedback in the circuit, which is NOT a good thing.

Midnite Mick

Doesn't most distortion occur at the speakers anyway?

Mike

Jstas

WARNING: Super Nerd Content contained below! (Stop crying and read it, you might learn something.)

Read this link:
http://www.dogstar.dantimax.dk/tubestuf/thdconv.htm

Also, check out this link:
http://en.wikipedia.org/wiki/Total_harmonic_distortion


The problem with THD is not in the measurement itself but how it's measured like what was already said. With just a number to go by and a percentage at that, you don't really know what you are looking at even if you know what it means. That is why if you are going to buy equipment based on specs, you need to understand what all the specs mean and how they relate.

A low THD tells you nothing without looking at the other specs. Companies can cheat on the measurements but you can see where cheating happens. If you look at something like slew rate (http://en.wikipedia.org/wiki/Slew_rate) in reference to THD, you can get a fuzzy picture of efficiencies with the amplifier. Slew rates are measurements on the input side of the amplifier and THD is pretty much on the output side. If you have a high slew rate and a high THD then the amplifier is not necessarily efficient and may not have a whole ton of overhead left for extreme musical transients and peaks. If the slew rate is high and the THD is low, the amplifier may have alot head room but may be inefficient as the power goes up. If you look at intermodulation distortion (http://en.wikipedia.org/wiki/Intermodulation_distortion) in reference to slew rates and THD, you can see how a high slew rate and ultra low THD can look spectacular on the side of a box but are really hiding how sloppy an amplifier really is. IMD is important to look at in reference to THD because if the THD seems too good to be true, it may be because it is. One way to measure THD is with a straight sine wave and minimal harmonics. Looking at the IMD will show that the THD may be great but once you try and play music, the amplifier will start to lose control of the signal reproduction as the power creeps up.

It is entirely possible to buy equipment by looking at specs and never listening to it. If you have an experienced ear and a good understanding of what the different specs mean, you can get a good idea of how the system will sound, it's good spots, it's bad spots and where it might be bright or mellow. Does it replace your ear? No, not by any means but if you don't have the opportunity to listen to gear before you buy it, knowing what all those numbers mean can help you out. It's also good to know because it will give you a more complete picture of what your stereo is doing when you are demanding music from it. It makes you a more informed hobbyist and a more informed buyer. That way, when you are looking for new equipment, you aren't Dependant on what everyone else says sounds good, you can go and look for yourself.

phuz

Get a cheap-o SPL meter and calibrate your system with it, then tell us how it sounds....

frreo1

A couple of things to look at:

1. Do you have a large/small setting on your center speaker selection from your receiver (I think you do). If so, try selecting small for the center.

2. How are your front speakers hooked up in relation to your sub? If you are using the LFE out to the sub, try setting the fronts to small, and let the sub reproduce the bass.

Most amp power is consumed reproducing the bass. If you relieve the receiver of that job by setting the speakers to small, that may improve your clarity.

Last but not least, check the nominal impedance of your speakers. If they are 4 ohms, check if your Yamaha has a 4/8 ohm switch. If so, while the receiver is OFF, select the 4 ohm option.

Hope this helps.

Spacedeckman

Unless it is broken, your problem isn't on the amplifier side. You are suffering from a substandard center channel compared to your right and left, or have it set up incorrectly.

Don't get hung up on specs, they almost never do you any good, and often work against you. To understand specs, you need context, and you won't find that in any owners manual.

Mark

joeygrand3

I have received some great info from this forum and have determined that the specifications do not tell the entire story. I have decided to get a beefier center. I will advise as to the result of that upgrade. Thanks for your input.