Which AR speakers sound best with Fisher 500B

[Jasper]

Just got a completely refurbished Fisher 500 b tube amp. My mom had AR speakers  when I was a kid in the late 60s. Thought I might try to match some up with this amp. 
any suggestion for a good match 
 

 

[genek]

You have somewhere around 25WPC of real RMS power. I probably wouldn't try any ARs larger than the AR-2 series or its successors, i.e., a single 10" woofer.

[Jim Pearce]

Pardon me but how does one calculate real RMS power, for example I have a Sansui 8080 that appears to be rated at 80 Watts but has been measured at 85 or 90.

[genek]

If your amp or receiver was made anytime after 1974, its specs will state what the RMS power is. If you don't have a manual for it, check on hifiengine.com.  For older models that give ratings in "IHF power," "music power," "dynamic power," "total power," etc., RMS power will be somewhere between 1/3 and 1/2 of what is claimed.

[Jim Pearce]

The 80 80 is rated at 80 Watts or so period when I had it refurbished and when others have had theirs measured like mine they have measured about 85 or 87. I'm talking RMS.

I have heard that the 9090 measures over 100.

Thatwould probably be about 275 peak or whatever.

I heard somebody say ,,real,, RMS I think.

I may have misread or misunderstood that but that is what I am asking about.

So, is there a real risk of running this at about 50 Watts or over 30 or what?

Hell, I have routinely run it at 70 or 75.

Even with attenuators maxed out and treble control maxed out allbeit for short periods.

Edited October 9, 2020 by Jim Pearce

[genek]

Are you using an actual power meter to determine that you are putting out that much power, or just making as estimate based on where the volume control is set?

Output power is signal-dependent. With music, you probably have a steady output of around 10W or less. 

[lARrybody]

Would real RMS power be stated as "XX wats per channel, 20-20,000Hz with less than 0.XX distortion".  I have a Fisher 400 that I have listened to with some AR2a speakers circa 1962 and also some 1963 KLH Model 6 speakers.  How about some of the 8 in variants like the AR 18, 18s, and AR 25. 

[AR55]

I had my father in law's Fisher 800C (30 WPC RMS) restored a few years back, and tried it out with a few of my speakers before I returned it to him:

AR-15: 2-way speaker with an 8" woofer & 1" dome tweeter. 

AR-14: 2-way with a 10" woofer and the same 1" dome tweeter. 

AR-11: 3-way speaker with a 12" woofer, 1-1/2" dome midrange & a 3/4" dome tweeter.

In my small theater room (12-ft x 14-ft) the Fisher performed well with all of the speakers.  The Fisher didn't show any strain even with the volume was pushed to an uncomfortable volume.  Typically, I listen to my AR-11's in that room and it is rare to see the meters on my amp peak above 10 WPC.  In my larger outer room (24-ft x 17-ft) the Fisher struggled to power the AR-11's if the source material was in the least bit challenging.  Even the AR-14's pushed it if there was a lot of bass energy.  I typically listen to my AR-9Lsi's in this room and they will draw 50 WPC or more at times, although most of the time the amp's meters peak at less than 25 WPC.

Basically, if you going to use the amp in a small, somewhat live-to-average room, your Fisher 500C can probably can handle most any 2-way or even 3-way AR speaker.  However, if your listening room is a larger, less live room, I would stick to a 2-way.  

Below is a graph that AR published for the AR-98Ls showing the relationship between power needs and room size/liveness.  Note that the AR-98ls is a larger 4-way speaker, probably requiring more power than the AR-11.

 

 

 

[genek]

2 hours ago, lARrybody said:

Would real RMS power be stated as "XX wats per channel, 20-20,000Hz with less than 0.XX distortion".  

From 1974 on, yes. Prior to that, power ratings, even in RMS, were usually measured with a 1kHz test tone and not across a frequency range.

In 2000, the FTC caved to manufacturer pressure and reduced the preconditioning requirement for testing. From 1974 to 2000, amplifiers were required to run at 1/3 of their claimed output prior to testing; after the 2000 rule change, that was reduced to only 1/8. So when comparing amplifiers manufactured from 2001 on to ones from 1974-2000, reduce the power of the newer models by about 15%.

Also, FTC amplifier ratings do not apply to multichannel amplifiers, because the rule has never been updated to cover them. This is why many home theater amps and receivers provide power ratings in both stereo and surround mode. You should only trust the stereo ratings, because just as in the old days before 1974 they can pretty much claim any BS numbers they want for the multichannel mode.

[Aadams]

The most demanding recordings need 12 to 15db of headroom.  If your system averages a demand of 2 watts from the amp at your lowest listening level then your 8080 in its current setup has almost 15 db of headroom using the RMS power number alone.  If your average is 1 watt then you have almost 18 db of rms headroom.  If your average is 4 watts then to achieve the same headroom your 8080 must momentarily surge to 128 watts, which it probably can do at 8 ohms, but if you replace your 2ax with a 3a then at 4 ohms you may need a 200 watt peak capability.

A push lawnmower engine is 100db at the push position with no dynamic range, so no headroom required.  You could play that recording all day long and eventually damage your ears but your amp and probably your speakers would be good.

Rock and pop music dynamic range rarely exceeds 6db. 

Some modern recordings of large scale orchestra, big band jazz, movie soundtracks and solo concert grand piano can be 12-15 db.

 

Adams

 

[johnfalc]

AR-2ax are a great choice for this in a smaller room.  I run them on a very similar Fisher 800C.  You would want much more power in a larger room; I run one or two Carver M-1.5t in my living room with AR-9 or AR-3a.