what does ohms and db mean?

[richteer]

Originally Posted by NJMetsFan

http://www.surrealmirage.com/subaru/tip.html#thd

I just found this site...and I quouted some info.

I'd ignore most of what that page states; it's hopelessly confused...

[richteer]

Originally Posted by gargantuo

Not to change the subject, but all the impedance talk makes me ask this question:

Does anybody have any old school tube receivers?

No tube receiver here--but I do have a pair of PrimaLuna ProLogue 7 tube monobloc power amps, driven by an Audio Research SP9 Mk 2 tube preamp. Together they sound wonderful. :-)

[jomari]

Originally Posted by saprano

yea i know, but i never had the slightist idea what these things ment, now i somewhat do.

thus my editing on my original posting...

see my first post for future reference.

[richteer]

Originally Posted by d_rob1031

I'm really glad someone brought THD up. To me, it is the most important rating on any amp.

Example: If you have 1000watts @ 10% THD, which is what most HTIB run at, you lose a lot of that 1000watts (which is peak, mind you, something else I'll touch on) that is used up by the amp.

Take that same 1000watts @ < 0.05% THD, which is what a lot of amps run at, better ones run even lower, you're going to break every window in the house. Which is why they don't run at 1000 watts

I just looked up the Onkyo 805 and it runs at 130watts per channel at 0.05% THD. If you took that same 130watts per channel at 10% THD you would have horrendous sound with crackling and loss.

The HTIB also are rated at peak power whereas real receivers are rated at RMS (root meat square). RMS is the wattage at which it's able to consistently do over a stated period of time. Peak power is the max it will do before it blows its self up, in other words, it never makes its peak power.

Hope this clears up why HTIB's usually suck (there are decent ones out there) and explains THD and how it's used.

THD means almost nothing. What matters most is how good an amp sounds, and unfortunately we haven't developed an objective measurement for that. Loads of cheap, crappy, amps and receivers have negligible amounts of THD, but they sound terrible.

I do agree, though, that as far as power ratings are concerned, the RMS value is the only one that's relevent. (In the UK, all amp power ratings must be in watts RMS into 8 Ohms @ 1KHz, to keep the manufacturers honest...)

[Deciazulado]

Originally Posted by musicman1999

Ten DB is not a doubling of volume, nor is 3 DB a doubling of power. It takes double the power to increase the volume by 3 DB and every further 3 DB increase requires double the power,

Uh? you just said it, mate.

3dB is a doubling of power, and it takes double the power to increase the volume by 3dB and every further 3 dB increase requires double the power

*scratches head

Originally Posted by musicman1999

example 1 watt=78db, 2 watt=81db, 4 watt=84db, 8 watt=87db, 16 watt=90db, 32watt=93db, 64watt=96db, you get where i am going,

yes those 3 dB's increases take a doubling of power.

Originally Posted by musicman1999

so doubling the volume 156db would require thousands of watts.Of course 156db you could not stay in the room and your speakers would explode.

bill

err "doubling the volume 156dB"? That's not the way you double the volume. 156dBs is NOT double the volume of 78dBs. it's 78 dBs MORE. (Almost 256 times (2 raised to the 8th power) louder!).
Doubling the volume (making the perceived sound twice as loud roughly) is 10dB so it would go from 78dBs to 88dBs which would take in your example going from 1 watt = 78dBs with your speaker to 10 watts = 88dBs with your speaker. If you want it to be again twice as loud, (98dBs) you go up to a 100 watts, and so forth.

[saprano]

Originally Posted by jomari

thus my editing on my original posting...

see my first post for future reference.

now THAT i could understand i still like everybody posts even if its hard to understand. it makes me want to get into this type of thing and learn more about it. and like you said, i think iv been enlightend

[jomari]

Originally Posted by richteer

(In the UK, all amp power ratings must be in watts RMS into 8 Ohms @ 1KHz, to keep the manufacturers honest...)

of course, this is subjective. i cant really find a manufacturer who can claim to be '100%' honest, especially with confusing 'high output' ratings as well.

it was great participating in this thread...

[saprano]

Originally Posted by jomari

of course, this is subjective. i cant really find a manufacturer who can claim to be '100%' honest, especially with confusing 'high output' ratings as well.

it was great participating in this thread...

are you leaving this topic?

[Deciazulado]

logarithms are cool. they're everywhere in audio video.

Just look at film's ISO speeds or musical octaves, specially thirds of octaves frequencies, or power rating increases. Is as if everything was cosmically connected

[jomari]

Originally Posted by saprano

are you leaving this topic?

in essence, yes. considering that ive given my input on certain matters, this gives others the chance to involve themselves in the participation as well. these discussions normally digress in nature, and require more than just a quick conversation to clearly understand more about impendance, sensitivity and THD levels.

hopefully my knowledge (as well as my colleague) has given substantial information regarding your inquiries.

THD, tubes and 2 channel amplifiers are yet another discussion.

my best suggestion is getting a good sound meter (found at your local radio shack) and play around with it.

as i mentioned, there are other variables more important imo than 'just the components'... as my colleague would bet his setup on, acoustics are the most underrated part in the scheme of things.

get some mopads to decouple your speakers, acoustic treatments, and a fair amount of calibration glued together with patience and research, would drastically improve your current home theater setup.

[saprano]

Originally Posted by jomari

in essence, yes. considering that ive given my input on certain matters, this gives others the chance to involve themselves in the participation as well. these discussions normally digress in nature, and require more than just a quick conversation to clearly understand more about impendance, sensitivity and THD levels.

hopefully my knowledge (as well as my colleague) has given substantial information regarding your inquiries.

THD, tubes and 2 channel amplifiers are yet another discussion.

my best suggestion is getting a good sound meter (found at your local radio shack) and play around with it.

as i mentioned, there are other variables more important imo than 'just the components'... as my colleague would bet his setup on, acoustics are the most underrated part in the scheme of things.

get some mopads to decouple your speakers, acoustic treatments, and a fair amount of calibration glued together with patience and research, would drastically improve your current home theater setup.

i dont think i need or can get any acoustic treaments done being that im in a small room with alot stuff in the way, still im sure im awaiting some amazing sound ether way. when i move out then i can get thoes stuff done deffinitly. untill then all i can do is play around with the sound to see what i like best, thanks for the info(everybody) tho. and like i said before, i will be learning more about this stuff, and this is the best topic that i ever started and im gald i did.