|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
128.125.179.129
In Reply to: Speaker load vs. Sensitivity with a tube amp posted by gnugear on March 31, 2007 at 09:30:36:
8 Ohm speaker must be connected to 8 Ohm tap, and 4 Ohm speaker to the 4 Ohm tap. Any attempt to use mismatched load will cause not only loss of power, but significant change in frequency response.
Follow Ups:
Mismatch what?Speakers impedance vary and will never match rating on the amp, and you will always have frequency variation due to mismatch.
One 8 ohm nominal speaker may have minimum that drops way down at one frequency to lets say 4 Ohms and may go way up at other frequency to let's say 12 Ohms. So which tap are you going to connect?
Other 4 ohm nominal speaker may have minimum that drops down at one frequency to let's say 3 Ohms and may go up at other frequency to let's say 30 Ohms). So which tap are you going to connect now?
Than some manufacturers mark tap as 8 ohms but in reality it is optimized for lets say 5 Ohms since they expect speakers to drop to below 8 Ohms?
Amp will controll better speakers from lower tap. With 6 ohms nominal speakers I would go with 4 Ohm tap.
There will be power loss no matter which one he chooses but is usually negligible from the SPL point of view.
Blah-Blah:From what you say, speaker impedance value has no meaning because it varies so much.
Yet all the manufacturers provide impedance ratings for their speakers, and there is not much concern that this parameter cannot be precisely defined.
Rated impedance is a prevaling value across the frequency range. It means that 4 Ohm speaker, for example, will have about 4 Ohm impedance from 200 to 12,000 Hz. Although this speaker may have impedance of 6 Ohm at 20,000 Hz and 30 Ohm at main resonance, it has to be connected to the 4 Ohm tap.
Your statement that amp will control speaker better on the lower tap is incorrect. Tube amp will better control speaker on the nominal tap. 6 Ohm speaker should neither be used on 4 Ohm nor on 8 Ohm tap. Tube and SS amps are very different with regard to their optimal load.
No, that is not what I said,"From what you say, speaker impedance value has no meaning because it varies so much."
Where did I say that speaker actual impedance (not claimed nominal speaker impedance) has no meaning?
"Yet all the manufacturers provide impedance ratings for their speakers, and there is not much concern that this parameter cannot be precisely defined"
Wishfull thinking, CLAIMED NOMINAL manufactureres speaker impedance has questionable meaning in this case as it may vary widely over the range (that is why speakers used with tube amps need to have fairly smooth impedance curve).
"Rated impedance is a prevaling value across the frequency range. It means that 4 Ohm speaker, for example, will have about 4 Ohm impedance from 200 to 12,000 Hz. Although this speaker may have impedance of 6 Ohm at 20,000 Hz and 30 Ohm at main resonance, it has to be connected to the 4 Ohm tap.
That is where your logic falls apart. Most of the power and speaker controll is needed in below 200 Hz range. And that is USUALLY where impedance dips (and peaks at tuning resonance) are (plus peak at the crossover to mid/tweeter. So although speaker may be listed as 8 Ohms overall, in that region it may actually be closer to 4 Ohms. So, is it still better to use 4 Ohm or 8 Ohm tap? Probably 4 ohms, but only his ears can tell.
"Tube amp will better control speaker on the nominal tap."
It seems that you are mixing up nominal and actual impedance.
"6 Ohm speaker should neither be used on 4 Ohm nor on 8 Ohm tap."
Complete and uter nonsence. According to that logic that means that Manley Stingray can not be used with any of the manufactured speakers since it has only one 5 Ohms tap.
VTL amps also use all of the windings for a single tap optimized for 5 ohms. My speakers are also nominally 8 ohms, but rise to about 20 ohms at the bottom and 2 ohms at the top!
This post is made possible by the generous support of people like you and our sponsors: