"High Output" Amp Selection

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mrvco

"High Output" Amp Selection
« on: 16 Sep 2016, 04:11 pm »
Being that the new "High Output" models are rated at 4-6 ohms instead of 8 ohms, does this change anything with regards amp selection as compared to the single driver models?  I've never owned anything other than 8 ohm speakers and my Omegas are my first single driver / high efficiency speakers.  While most amps have a higher power rating at 4 ohms, do you give up sound quality at lower impedance / higher wattage, particularly with a high efficiency speaker?

RDavidson

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Re: "High Output" Amp Selection
« Reply #1 on: 17 Sep 2016, 03:57 am »
I may be wrong, but in this case, while impedance decreases I think sensitivity increases. If so, a low powered amp might still serve well, as long as it has a stout power supply.

JLM

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Re: "High Output" Amp Selection
« Reply #2 on: 17 Sep 2016, 11:48 am »
Don't know what "high output" models you're thinking of mrvco, could you specify?  For higher efficiency speakers marketed for home use (that often have limited power handling capacity) and single driver designs (best suited for small ensemble genres at limited sound pressure - volume levels) most listening is done at very lower power levels.  Keep in mind that wattage versus dB is logarithmic, so it takes 10 times the power to sound twice as loud (a 10 dB increase).  Such genres are normally enjoyed at say 85 dB for "spirited" listening.  If the speaker is rated at 95 dB/w/m (another issue with vendor honesty) you'd be using 0.1 watts per channel is a small room and maybe 0.5 watts per channel in a large room.

On the other hand music is made up of peaks and it's those peaks that demand lots of power, due again to that logarithmic relationship.  Classical music can exhibit 30 dB peaks, jazz 20 dB, and rock 10 dB.  Live performances can peak at 105 dB for classical or jazz (more steady) and rock at 110 dB (nearly constant).  So that same 95 dB/w/m speaker could need 100 watts per channel or more to reach live classical/jazz peaks and 325 watts to reach live rock levels.  Thankfully speakers handle peaks rather easily (as long as the signal isn't distorted). 

Traditionally solid state amps don't handle peaks as "cleanly" as tubes that ordinarily have big/heavy power supplies, but nowadays are easier to find at higher power ratings.  On the flip side tube amps excel at lower levels where we typically listen. 

Speaker impedance varies with frequency.  The more benign designs vary less, but all rise steeply as it's lower frequency limit is reached and also commonly gradually rise at treble frequencies.  If you look at several speaker impedance graphs you'll discover that impedance ratings are painted with very wide brush strokes (highly generalized outside midrange frequencies).

Typically amps handle higher impedances better than lower (especially tube amps).  The mark of a "good" amp (stable, beefy, not fussy design) is one rated at double the wattage at 4 ohms versus 8 ohms.  Lower impedance loadings can cause "weaker" amps to become unstable and be prone to overheating.  In fact many tube amps have 8 and 16 ohm binding posts.  If the amp doesn't mention 4 ohm output it's probably because it's not recommended.  Note that historically Decware amps have been the exception, they thrive under low impedance loads. 

Impedance versus wattage is a simple electrical phenomenon.  If the amp is stable at 4 ohms, it's output will be doubled at 4 ohms versus at 8 ohms.  Sound quality shouldn't vary for a given amp regardless of the load impedance.

opnly bafld

Re: "High Output" Amp Selection
« Reply #3 on: 17 Sep 2016, 12:24 pm »
Is your question about tube or solid state amps?

opnly bafld

Re: "High Output" Amp Selection
« Reply #4 on: 17 Sep 2016, 12:35 pm »
For higher efficiency speakers marketed for home use (that often have limited power handling capacity) and single driver designs (best suited for small ensemble genres at limited sound pressure - volume levels) most listening is done at very lower power levels.  Keep in mind that wattage versus dB is logarithmic, so it takes 10 times the power to sound twice as loud (a 10 dB increase).  Such genres are normally enjoyed at say 85 dB for "spirited" listening. 

Completely wrong IMO and IME.
In a home 85dB is spirited listening no matter the genre for me.
Of course if you listen a lot louder all the time, 85dB will seem really low (or if you have major hearing loss).
Have fun listening in your home at the 100 dB and over numbers JLM always goes on about, not me I like my hearing too much.

opnly bafld

Re: "High Output" Amp Selection
« Reply #5 on: 17 Sep 2016, 12:39 pm »
Don't know what "high output" models you're thinking of mrvco, could you specify?   

http://omegaloudspeakers.com/superalnicohigh1.html

http://omegaloudspeakers.com/superalnicohigho.html

Possibly more on the way?

JLM

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Re: "High Output" Amp Selection
« Reply #6 on: 17 Sep 2016, 01:37 pm »
Thanks for the links O.B.  Didn't recall Omega had developed additional 2-ways.
 
But you continue to misunderstand me.  I'm hardly a headbanger.  Rarely listen at over 90 dB.  Own very few rock albums.  Been over 20 years since attended a rock concert (if you call Amy Grant rock).  Currently listening to "Bach for Breakfast" at 70 dB.  And constantly rant about potential hearing loss/tinnitus from continued exposure to 85 dB or higher (I wear protection around heavy equipment and own/use a spl meter).

I bring up spls, dB's, and watts because much confusion exist.  And I believe hi-fidelity audio systems aught to be able to recreate all aspects of the original performance, including spls.  It's an individual choice of how loud to listen (as long as you're not imposing on others).


A bigger concern with the new high-output speakers would be system self-noise due to the higher efficiency.  At 99 dB/w/m the speakers will be very revealing of any distortion, interference, or grounding issues.  Solid state does best at higher power levels but tubes can have more distortion challenges.

jorgen

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Re: "High Output" Amp Selection
« Reply #7 on: 18 Sep 2016, 10:34 am »
Reading up on these issues, but have no electrical background, though understand a few basics. I'm interested in these new high output speakers to go with my Decware miniTori. My amp is 8ohm swell as my current 7" Alnico floorstanders from Omega. Very happy with combo. If introduced a more sensitive set of speakers, with 4-6ohm. What could or should I think about could be downsides.  They will match the ohm my amp has taps for? I have a low hum hear able only when very close, not from listening position. I heard almost the same hum with 87dB speakers from BW.  I heard a Decware select with 3xrs speakers and heard the same him, but far from problematic. Today the hum isn't affected by volume at all.

opnly bafld

Re: "High Output" Amp Selection
« Reply #8 on: 18 Sep 2016, 01:11 pm »
jorgen,
My guess is the older MT loses power as you go away from 8 ohms, so you would get some increased output in the passband of the lower driver on the high output versions, but no overall increase.

All Decware amps now have 4 ohm and 8 ohm outputs so there is more flexibility with regard to speaker load.

jorgen

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Re: "High Output" Amp Selection
« Reply #9 on: 18 Sep 2016, 06:32 pm »
Hi Lin
I checked the Decware site, and for the MT there isn't any ohm options, seems like 8 is standard. BTW mine is a late 2014 model.

opnly bafld

Re: "High Output" Amp Selection
« Reply #10 on: 18 Sep 2016, 06:52 pm »
I should have said they come with switches to select impedance.

MINITORII-III - New in Oct 2015

Installed UFO output transformers for nearly 400% wider bandwidth and an impedance switch that lets you hear your speakers on both a hi and low impedance settings.  An ultra serious upgrade to an already incredible amp.

jorgen

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Re: "High Output" Amp Selection
« Reply #11 on: 18 Sep 2016, 09:54 pm »
So it might be an idea to send the amp to Decware for an UFO upgrade? Any idea what that cost? I will have two setups running soon though, the new mono Zen amps are very tempting. If priced not to much more than 2500*USD it's pretty much a done deal.. A shame our currency at the moment are worth less than spare button at the moment.

opnly bafld

Re: "High Output" Amp Selection
« Reply #12 on: 18 Sep 2016, 11:24 pm »
Not worth it for you; just keep a pair of good ~8 ohm speakers around.  :)

G Georgopoulos

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Re: "High Output" Amp Selection
« Reply #13 on: 18 Sep 2016, 11:44 pm »
I may be wrong, but in this case, while impedance decreases I think sensitivity increases. If so, a low powered amp might still serve well, as long as it has a stout power supply.

this is true with ss,but with tubes dont think so