Audiophile03 Posted November 21, 2011 Report Share Posted November 21, 2011 Whats the lowest wattage tube amp that I can comfortably run my AR-2A's with? Thanks for any info! Link to comment Share on other sites More sharing options...
JKent Posted November 21, 2011 Report Share Posted November 21, 2011 This B.A.S. article on speaker efficiency may or may not be useful:http://www.bostonaud...-01-11-7308.pdfIt does not list the 2a but it does include the 2ax and shows them to be pretty inefficient, requiring 60w for 100db. My guess is there are a lot of other factors to consider. I used to drive my AR4x's perfectly well with a dyna 17wpc tube amp. YMMV. A lot depends on the source, room size and volume. For heavy metal head-bangin' music you'll want an amp that goes up to 11 *What size amp do you have/are you considering?Kent*Spinal Tap reference Link to comment Share on other sites More sharing options...
Steve F Posted November 21, 2011 Report Share Posted November 21, 2011 The 2a and 2ax have essentially the same sensitivity.I have AR-3a’s in a small 11 x 13 room. First, consider that the sensitivity specification, as measured one meter on axis for a 1-watt input, will yield a figure of about 86dB for an AR-3a. That’s considered “inefficient.” The 2's are similar (but their higher impedance will draw less current from a solid-state amp, so they may appear to be of "lower efficiency" at the same physical setting of the volume control compared to the 3/3a).But 86dB is really a pretty healthy level, much more than background listening. It may not be loud enough in a dealer showroom, but in your quiet listening room, you’d have to turn it down to answer the phone. I regularly use a Radio Shack SPL meter to check the playback levels in my room, and it's amazing how loud low-mid-90's dB SPL is.Now, you’ve got two speakers, so there’s some addition to the 86 SPL figure because of that. You are also about 8-10 feet away from the two speakers (and somewhat off axis, to boot), so there’s some reduction because of that (the inverse square law, which says that SPL reduces by -6 dB as the distance doubles). Throw in your room’s absorptive characteristics, any open walls that lead to the next room, etc, and what you’re left with is that the raw sensitivity figure for one speaker is a pretty decent number to work with as to how loud two speakers will sound from your listening position with a one-watt input. There are a LOT of variables, obviously, but 86dB for 1 watt for a pair of 3a’s from your listening chair is not a bad estimate. The 2a will be very similar, within a few dB.Every doubling of power is another 3dB of loudness. So:2 w = 89 dB4 w = 92 dB8 w = 95 dB16 w = 98 dB32 w = 101 dB64 w = 104 dB128 w = 107 dB256 w = 110 dBI’m not even sure how cleanly the 2a can play at or above 110dB, but any competent amp has enough juice to push the 2a to 95-100dB in a normal listening room. And that is very, very loud. As mentioned in previous posts, make sure you’re using a good amp that’s not apt to be driven into distortion. The 2a doesn't have a ferro-fluid cooled tweeter, so be careful not to abuse the speaker by pushing the amp into gross audible distortion.Caution and common sense are always the guidelines when using 30-50 year-old classic speakers that have irreplaceable parts.Steve F. Link to comment Share on other sites More sharing options...
Audiophile03 Posted November 21, 2011 Author Report Share Posted November 21, 2011 Wow, lots of science and math involved! I don't have a particular amp I am looking at quite yet. Most of them have been the the 15w rms per channel range. I mostly listen to classical and am radio with a bit of country and classic rock tossed in between. I don't listen at loud levels, mostly slightly higher than background volume. I am not sure of the room size but it isn't very big. Link to comment Share on other sites More sharing options...
Steve F Posted November 22, 2011 Report Share Posted November 22, 2011 My gut tells me that based on your listening habits and room, 15-20w will be fine. That will get you into the 90 dB range without any problem, which is plenty loud and definitely louder than 'background level.'Steve F. Link to comment Share on other sites More sharing options...
genek Posted November 22, 2011 Report Share Posted November 22, 2011 It is worth noting that:85-95 dB is the range in which sustained exposure begins to cause permanent hearing loss. Real-world examples include a garbage disposal or blender or a passing big rig truck.60-70 dB is the range of normal conversation.45-55 dB is the level of background noise in an average residence.30 dB is the level of your public library's reading room. Link to comment Share on other sites More sharing options...
Steve F Posted November 22, 2011 Report Share Posted November 22, 2011 Agreed--hence my observation that mid-90's on my SPL meter is extremely loud and that in the mid-80's, you'll have to turn down the system to answer the phone. As I said, 15-20 watts will drive the 2a to very nice levels, and as long as you don't push the amp into gross audible distortion, both your speakers and your ears will be fine.Steve F. Link to comment Share on other sites More sharing options...
Audiophile03 Posted November 23, 2011 Author Report Share Posted November 23, 2011 Great news! Thanks for the info everyone. This will aid in my decision on a tube amp. Link to comment Share on other sites More sharing options...
fordf250 Posted November 23, 2011 Report Share Posted November 23, 2011 Give "tubes4hifi.com" a "look-see"! Link to comment Share on other sites More sharing options...
Audiophile03 Posted January 13, 2012 Author Report Share Posted January 13, 2012 I just received a refurbed Maggy tube amp and a refurbed Heathkit AA100 today. I tried both out on the AR's and all I can say is WOW. It is a night and day difference from running them on a solid state amp. I will never go back to solid state for my TT system again, the tubes have me hooked now! Link to comment Share on other sites More sharing options...
Audiophile03 Posted January 17, 2012 Author Report Share Posted January 17, 2012 And here is the Maggy amp running them.. Link to comment Share on other sites More sharing options...
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