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Can we address the low power amp again --?


richieb

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Thinking hard on a 2a3 or 45 single ended for the KHorn and/ or LS. For those with experience will these kind of watts drive these speakers Properly and with Authority. Will they dig down with appropriate bass and control? My KHorns have the Fastlane top hat and ALK AP12/5800 extreme slope networks if that makes a difference in and if power to the drivers would be affected. When I owned Belles I remember a friend brought his Sun Audio 2a3 and we both were of the opinion that the sound was very thin, lacking both mid and bottom - all bones, no meat. With that in mind maybe I should know better than to address and even chance it although it seems many are satisfied with the results they get. The 45 would be a Dennis Had custom build and the 2a3 from Arte Forma which looks to sport superior build/ component quality and massive iron which I believe can be the key to the drive a lower powered amp provides.

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I dunno about that...richieb is using Khorns.  A single watt should bring plenty of weight and authority, provided a little loudness compensation or other eq has been appropriately applied.  I do that using considerably less sensitive speakers and it has weight and authority galore.  The only drawback, if it really is a drawback, is an inability to achieve painfully loud spl levels.  

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I dunno about that...richieb is using Khorns.  A single watt should bring plenty of weight and authority, provided a little loudness compensation or other eq has been appropriately applied.  I do that using considerably less sensitive speakers and it has weight and authority galore.  The only drawback, if it really is a drawback, is an inability to achieve painfully loud spl levels.  

Agree completely.  SETs and SEPs can both provide a very full bottom end and, with speakers like the K-horns and LSs, power isn't usually a big issue unless one wants to shatter glass.  I'm not familiar with Al's crossovers and don't know their effect on efficiency.  Perhaps one of the speaker guys can answer that question.  More info about your listening environment, habits, and so on may help to determine just how much power you are likely to need, and whether it can be provided by a 45 or 2A3.

 

Maynard 

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I have a pair of Dennis Had designed Cary CAD 45se. I have used them with my Belles - which are in a very large room - and have to say they wouldnt be my first choice for the speakers in that room. I have them in a bedroom system driving single driver speakers and they are remarkable for the speakers and the room. Kind of depends on the music you prefer, the size of the room and how loud you like to listen!

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Thanks for the early replies - the speakers are 23ft apart, I sit 15ft back at the point of the triangle, and there is another 15ft behind me. A rather large finished basement with open rafter 8ft ceilings, partially carpeted. Volumes are moderate+ at best, never really "loud". My current Had KT66/88 SE at 6 and 10 watts really drives them nicely with good bottom, maybe a tad loose but very pleasant. I have tried a 200 watt hybrid, 4x 6922 in the pre section and while it is an excellent amp the KT88 sounds better, fuller at the volumes I listen.

Thanks Joshnich for the Had 45 opinion. I have spoken with Dennis a few times on his new 45 amp/pre design where he says it may well be the most musical he has ever put together and I do not doubt him. But as my question suggests I am very unsure about 2 watts bringing true full range authority even to efficient KHorns although Dennis says they fill a room like 20 watters.

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I respect Dennis' work going back to when he started the ham radio company Dentron back in the 70s.  As to a 2 watt amp filling a room like a 20 watter, I'm a bit skeptical.  A simple experiment which you can try if you happen to have a peak-holding multimeter is to set it to a low voltage AC range and clip its leads across one of your speakers.  Put on some music and turn the volume of the system up to the loudest level at which you listen and note the highest voltage recorded.  Square it and, for the sake of convenience, divide it by 4 (close enough to the speaker's minimum impedance) and you will have a very approximate idea of how much power you're using to achieve that level.  If it turns out to be 4 or 5 watts you will know that 2 watts won't suffice.  Again, this is a rudimentary measurement, but it will give you some idea about power needs.

Maynard

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I would like to submit that output power capability (as in wattage) is not the only consideration in determining the kind of control a given amplifier will have over a woofer, horn-loaded or not. I have a class A OTL amplifier that is good for about 1.5 watts/channel that has a better grip on low end response than a couple of PP valve amps with significantly higher outout ability. There are reasons for that.

Al makes quality passive networks that are excellent in terms of both design and craftsmanship. The high order (Extreme Slope) networks can also be very good under the right conditions. The drawback is that higher order passive networks require heavy amounts of inductance and capacitance in order to achieve their design goals. High series L and C introduce insertion losses that for a low power amp (as with the one mentioned above) are considerable and amount to significant attenuation where headroom is already in short enough supply. There are other networks available for these big horns that IMO are much better suited to such low output (but exceedingly good sounding) amplifiers -- my favorite being the 6dB/octave slope type A network.

Edited by erik2A3
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I use a 1.8 watt per channel 45 Amp (Welborne DRD Starchief) on my 114 db Oris Horns. I also use 400 watt per channel Class 'D' amps on the Khorn Bass Bins. For most of my Jazz Music the 45 amps were plenty good for me. When I had a friend over that wanted to hear 'Chest Thumping Bass', he would send my 45 amps into clipping. So then I started Bi-amping which was a relatively cheap tweak. The Class D amps only cost $800 and included an active X-over. Now when he comes over, I have plenty of Bass. That being said, I could live with just the 45 amps which gave me plenty of music in the upper 80dbs in my 28 x 21 room.

Edited by Cut-Throat
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It's not the WPC, it's the huge power supplies, caps, and quality that give big amps real beef. Personally, I like small amps, I run small tube amps in 3 of my best systems but it can't match my highpower system in weight and slam, even at low volumes.

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The only drawback, if it really is a drawback, is an inability to achieve painfully loud spl levels

 

Not the only drawback. While a Khorn will produce 104 dB 4 feet from the front of the horn, that will drop to 98 dB 8 feet away. Approximately 92 dB at 16 feet, depending on the room. Then there is the matter of the peaks - The SPL peak will be about 13 dB higher than the average SPL, depending on the dynamic characteristics of the particular recording being played. 13 dB = 20 times the average power, so if you want to reproduce a recording that takes 1 watt average to produce a given SPL it will take 20 watts to reproduce the musical peaks without distorting the amplifier.

 

So, in short, an amplifier of 20-35 watts should work well for you in a room the size of yours.

Edited by Don Richard
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20 to 30 watts might be fine, and also might not be what this individual is looking for in terms of the KIND of sound and or sound QUALITY he may be seeking. Wattage alone is nothing more than a quantitative value. Moreover, I don't think we have knowledge of this person's listening preference as far as desired listening levels, music genres, and so forth -- all of which are important considerations.....in my view.

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Great answers/info from all - thanks. And much of what I suspected.

I think I will pursue an integrated, I'm an integrated fan, using the big Russian 6c33 power tube for18 big SE watts. Using this tube before on both LS and Cornwalls provided a huge stage, deep yet tight low end, a totally enveloping sound. The downside can be drifting bias until the glass has settled and heat. Extreme heat. But since moving the main rig to a recently finished basement the heat and open equipment rack will be perfect for these miniature reactors.

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Nelson Pass definitely has made important contributions over his many years as an engineer. In this particular case, a single-ended 45, 2A3, PX25, 300B, EL84/6BQ5, etc., on its own, can be magical with Klipschorns or La Scalas. Both are relatively easy loads in terms of nominal impedance, and without a doubt, efficiency, that small amplifiers based on SE triodes (or pentodes) can be in my experience remarkable -- again relative to the listening habits and preferences of the user.

As Kevin mentioned, which is something I have also done, is biamp with the single ended triode for middle and high frequencies, only.

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I'm listening to my 45/2a3 and it cruises around mid 90's db just fine. Sounds great.  If I am going to be acting a fool and cranking it I biamp put my 2a3/45 on the HF and my PP triode Luxman 30wpc on the LF. Or I just hook up the luxman.

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