stupidhead Posted July 26, 2018 Report Share Posted July 26, 2018 Hello fellow members. As many of you know I am a fan of the vintage AR speakers. Let it just be said I have a number of sets to choose from in the various 2, 3, 4 and 5 models. My particular favorites are the AR5's. Over the years I have seen cut sheets for all these models and when looking at amp power ratings 100 watts per channel is generally cited as the max power recommended. Over the past few years I have also been on a quest for some vintage amps and am a bit nervous about a few of them. First off I have acquired a Marantz 2230, 2270 and 2325. All have now been gone through by very qualified techs (2230 Pat Font and 2270/2325 Randy Buckner) and am trying different combinations to evaluate the synergy between the various models. I also have a completely McShaned HK Citation II that I got from Don Sachs. I am actually using that with the 2230 as pre and driving a refurbed set of 4x and the result is sublime. I have been using the 2270 to drive a stacked set of 5's on top of a set of 2ax and have been quite happy with the result. I just got back the 2325 from Randy and this 125 watt per channel beast on paper would have too much power, I think. When he tested it he got 140 per before clipping, yikes. Before sending this out to Randy it cooked a pair of KLH 5s which I had gone through. They sounded quite good at moderate volumes but if jacked up over 12 o'clock the speakers would "snap" on heavy bass notes. One day my wife was listening and had opened the windows to hear the music while she worked in the garden. When I got home the speakers were buzzing and haven't been heard from since. The question is will the 2325 have too much power and is there anything (in line fuse?) I can do to safeguard the speakers? I have also recently gotten two Dynakit ST70 amps which I hope to work on this Winter. I am not too worried about their power being too much, much like the Citation II. Then there is the two (yeah two) Nakamichi PA7 units I fell into earlier this year. I could not pass them up once I did a bit of research on them. The price was right and the one owner (who I know to be a reasonable sort) history was too much to pass up. I am likely sending these to Randy for his magic and a refresh but on all counts would be the same concern I have about the 2325, just too much power for these models. I have seen a spreadsheet someone created that has specs all on one sheet but can't find it anywhere now, Robert you must have it yes? Please post or send if you do. And I do ask myself "My God! What have I done?" thoughts, ideas, whatever. Obviously I need help, maybe a support group if you know of one. Geoff Link to comment Share on other sites More sharing options...
xmas111 Posted July 26, 2018 Report Share Posted July 26, 2018 To much power usually isn't the problem. It's when you don't have enough power and the amp starts to "clip", that's when damage to your speakers can occur. John Link to comment Share on other sites More sharing options...
lARrybody Posted July 26, 2018 Report Share Posted July 26, 2018 Those classic speakers did not have fero-fluid in the tweeters and power handling was a problem. When I was in college and my parents were out of town I fried the tweeter in one of my Dads Large Advents. Fortunately they were under warranty and my Dad didn't ask to many questions. Buzzing is not good, those drivers are old and maybe tired. Take it easy. On the other hand I currently have a pair of AR3a's being powered by a Crown XLS2502. Probably around 700 watts per at 4 ohms. I don't pay them all that loud,but there is a whole lot of headroom. I am not afraid. I am not having a dorm party anytime soon. Link to comment Share on other sites More sharing options...
owlsplace Posted July 26, 2018 Report Share Posted July 26, 2018 Too much power, yes and no depending on source material and listening levels. You can always use the recommended fuses although the slow-blow FNM fuses get expensive if you are fond of blowing them. It may possible to use less expensive fuses and get the same coverage. ADS and Heathkit used the 6x30mm glass fast-blow fuses which are a lot easier on the pocketbook. I generally preferred to not blow the FNMs and play different speakers when the music needed to be loud. Ditto on Larry's comment. Source material and average power levels determine the amount of heat build up. A low powered amp that is clipping will deliver a lot of energy to the tweeters often causing the VC leads to melt and separate like a fuse. I'm sure more than a few people here have put drivers back into service by bridging those gaps. I have powered AR-5's with an Adcom 555 II through a passive pre with the volume at max playing the Simon & Garfunkel "Concert in the Park" cd --- which is the same as connecting a player straight to the amp --- with no issues. The speakers were fused and they sounded great --- thought I was at the concert. This amp puts out 200 wpc into 8-ohms although I'm not sure a cd players output is high enough to drive the amp to full power out. The 5's were always were power hogs. Anyway, the Classic-era tweeters had longevity problems delivering high SPLs without self-destructing, the Teledyne AR-9 era drivers not so much. At least that is my impression. My advice would be to use whatever amp you want but fuse them or lose them if you like the volume set on high or use lots of tonal compensation, i.e. treble boost. JMHO, Roger Link to comment Share on other sites More sharing options...
jessiAV Posted July 26, 2018 Report Share Posted July 26, 2018 Your Nakamichi PA7(Threshold Stasis) amplifiers have channel-independent DC offset and high signal or heat protection circuits that should protect your speakers under most conditions. They shouldn't need fuses but your classic Marantz amps really should have a fuse in each speaker line, if just to protect your speakers from DC damage should the output transistors short. As the guys above point out, an amplifier producing distortion can really hurt a Classic Speaker, and a fuse may or may not help with that. The best protection for your audio system is a sensitive human ear controlling the amplifier. Link to comment Share on other sites More sharing options...
DavidR Posted July 26, 2018 Report Share Posted July 26, 2018 Here's a chart for determining inline fuse size. I use the glass AGC fuse with the two part holder. Download the chart to your computer and then print it out. Link to comment Share on other sites More sharing options...
stupidhead Posted July 28, 2018 Author Report Share Posted July 28, 2018 thanx to everyone, these answers help settle my concerns. the chart for fuses will be helpful for sure. Link to comment Share on other sites More sharing options...
GD70 Posted July 28, 2018 Report Share Posted July 28, 2018 Great info and chart! Definitely will print it for the files. Glenn Link to comment Share on other sites More sharing options...
GD70 Posted July 28, 2018 Report Share Posted July 28, 2018 At the last Frankenfest, I was demoing my 3's with my JVC M-7050 amp, P-L10 pre amp. The 7050 puts out 210 wpc on my techs bench. They were going most of the day at decent volumes and had no problems. I am careful with the volume, but keep the tone settings flat. Monitor the sound carefully when you're listening at higher volumes and you should be good. Link to comment Share on other sites More sharing options...
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