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View Full Version : low power amplifier on efficiency spkrs.



Bruno GINARD
05-26-2004, 02:58 AM
A lot of member in this forum own high efficiency speakers ( + 100 Db/W/Meter).
Therefore, for a domestic use the power of the amplifier could be limited to 15 or 20 watts.
So watt is your views and personal experiences with single ended valves amplifiers using 300B,2A3, 211,845….. and with low powered class A amplifiers in relation to high power amplifiers ( Crest,Mc Intosh, Crown….) ?

Robh3606
06-03-2004, 09:47 AM
In theory maybe but in application I think that is a mistake. That's at 1 meter now move out to 3 meters figure 10-12 ft. You just lost 10 dB. So your sensitivity at your listenning position is 93dB for the pair NOT the 103db, for the pair, sensitivity rating at 1 meter. If you plug in 20 watts you can hit 106db peaks without clipping at 3 meters. That clearly is not good enough. If you try to reproduce well recorded drums or large orchestral works at a realistic levels you will be clipping on the peaks. Why hamstring one of your speakers greatest assets by underpowering them. JMHO but that is one of the major advantages with the speakers we enjoy. The dynamic presentation you can only get from horns or high efficiency direct radiators. Play with the calculator. That is what we should be using to determine how much power we really need.

http://www.doctorproaudio.com/doctor/calculadores_en.htm

Rob:)

Ian Mackenzie
06-03-2004, 01:53 PM
So watt is your views and personal experiences with single ended valves amplifiers using 300B,2A3, 211,845….. and with low powered class A amplifiers in relation to high power amplifiers ( Crest,Mc Intosh, Crown….) ?

Bruno,

I have tried a 300B SE, I recall about 7 watts or there abouts, it was nice but only for acoustic guitar. I then used a JLH 15 watt better.(the Lowther folks with 100 db sensitivity love the 300B SE's)

I now use a 100 watt class A Passlabs amp.

If you only play classical music, 15 - 30 watts and need only modest levels then go for it... very nice, but for pop forget it.

Ian

scott fitlin
06-03-2004, 05:21 PM
I have always thought, because I have heard it done with my own ears, that if you have very high efficiency horn loaded speakers, with compression driver horns you can use great sounding, solid state high current drives for the woofers, and SET,s for the horns and tweeters.

This way you have the sweetness and liquidity tubes are known for along with the balls, extension, and definition solid state can do on the bottom end!

Bruno GINARD
06-04-2004, 02:44 AM
I am totally all right with Rob... But with a 105DB/W/Meter loudspeaker ( Hartsfield) in a 30 M² lounge, it remain approximately 95 db at 3 meters. In addition, the neighbours will be in the front of my door beyond 100 db !

I actually use a valve amplifier, based on a 6550 PP Williamson circuit ( approximately 2 x 50 Watts), and the position of the pot in my passive preamplifier do not exceed the 12 O'clock position.That's why i think that a 10 / 15 Watts S.E. amplifier is sufficient in 90 % of my listening session. As Scott Fitlin suggest,
i will consider ,if 10 or 15 watts will not be sufficient , a SE amplifier above 500 Hz for horns, and a SS amplifier ( DEnon POA 4400 Mono-blocks that i own since 10 yars).

I'have made this reflexion after using a 110 Watts Pionner Home Theater ( with THX agrement) instead of my valve amplifier. Sound was hard, constrained,and the stage was anormaly reduced. THe most significant modification was the disappearance of the low frequencies ! Then, i understood that for my personal use, quality was more important than power ...

Amplifiers operating in A , like PASS Labs models, class must be a good compromise.

In the next months, i will try 300 be Se and PP amplifiers, and clas A SS amplifiers to confirm (or invalidate !) my opinion. In a parallel direction, a friend of i will test his 4350 spkrs with a 250W BGW for the low, and with an old 25 Watts Class A ELECTROCOMPANIET for the highs, instead of an Harman Kardon in the highs.

Mr. Widget
06-04-2004, 10:22 AM
Originally posted by Bruno GINARD

I'have made this reflexion after using a 110 Watts Pionner Home Theater ( with THX agrement) instead of my valve amplifier. Sound was hard, constrained,and the stage was anormaly reduced. THe most significant modification was the disappearance of the low frequencies ! Then, i understood that for my personal use, quality was more important than power ...



Most people these days do feel that different amps do in fact sound differently. I certainly feel this way.

That said, I wouldn't be as bold as to recommend as widely as "Class A", or "Mosfet", or "300B". Every amplifier has the output devices as well as power supply design, biasing etc.

I had Pioneer's Elite M91. It was their statement amp designed to appeal to those fans of McIntosh both with it's polished black face and it's use of output transformers to couple the amp to the speakers. It is a significantly overbuilt beast of a 100wpc amp. I tried it with several speaker loads. I thought it sounded hard, metallic, and lacking in open airiness at the top end. I was very happy to sell it!

I have heard and owned very good and not so good "Class A" ss amps. I have played around with tube amps but have been disappointed with all of them that I could afford. There are some wonderful tube amps out there, but to really get a stellar one, they tend to be pricey.

As for super low power "300B" and "2A3" type amps, they typically have a great midrange with soggy bass and variable top end (depending on the skill of the designer).

I do agree, if you are using a 100dBw speaker at sub 100dB levels more than 10 watts is not essential, but the >10watt amps I have heard have other sonic problems anyway. I have heard wonderful 25 watt ss amps from Electrocompaniet, Bedini, and others.

Widget

Ian Mackenzie
06-04-2004, 04:58 PM
Bruno,

105 db is quite sensitive.

How do you control your S/N in quiet tracks?

Regards the Willamson I built up the Linsley Hood 15 watts SS SE equivalant version of the Willamson a few years ago......very very nice....from the WW article circa 1969. The JLH has been compared to the Hirago monster and others.

I am thinking about those foran active version of my 4345 system.
ie An X 600 for the 2245 woofers, a AX 100 for the 2122 mids and some JLH 15's for the horn and slot.

Linlsey Hood passed away recently which is sad. He worked as a consultant to Hitachi and others when the 1st mosfets came on the scene and published a number of audio amplifier designs that remain classics to this day. He remains an engineer without peer when it comes to amplifier designs that not only measure but also sound good.

The Pass stuff is contemporary of this area using IRF240 mosfets which are biased with sheer brute force using simple two stage designs without feedback. The most recent version, the AX 200, a 200 watt mono block has been refered to by Absolute Sound as having the best of Tubes and Solid State when reviewing the Tad M1 in a recent issue.

Many on these forums are wedded to big muscle pro amps for the dynamics. But the idea of using small class a amps for the highs at least makes alot of sense.

The highs are an area where the human ear is most sensitive to 3rd, 5th, 7th etc odd harmonics distortions. These are a problems for typical A/B amps especially at low power levels. As it stands the highs use very little power and a small class A amp can be biased sufficiently to ensure no such harmonic distortions.....thats why they sound better.

Please let us know how your system develops.

Ian

spkrman57
03-06-2005, 08:13 AM
I run my Edgarhorn system with 45 SET power(2 watts/chnl) and find it good for classical/jazz/acoustic music.

If I need to run things harder, I use a alternate system with more watts, and more durable drivers as the Edgarhorns are 1st order crossover.

Ron

Ian Mackenzie
03-07-2005, 02:46 PM
Ron,

Let us more about your Edgar horn system

Ian

spkrman57
03-08-2005, 09:00 AM
Ian,
I hope to post pics in the near future when I re-assemble the horns. I have made a change in the midbass horn driver(horn is 80hz), I originally had a JBL 2205A driver in them and Bruce optimized the back cover over the driver(sealed back), but I was unable to sit back 1 wavelength from the midbass horn to the seated position(13,500 / freq = wavelength(80hz =14 ft)).

I took the E-130 reconed to 2225 and using that in the midbass horn, the midrange horn is a round wooden tractix 350hz horn(crossed over @ 500hz) 40 ufd oil in metal cap, the midbass inductor is a 2.5mh laminate with serious guage wire for low DCR. The tweeter currently is a Fane ST-5022, but will be replaced with a pair of JBL 075 bullets from my 2-way(D123/N2400/075) system.

I run this with a Yamamoto SET 45 amp (2 watts/chnl) which does quite a bit, but unlike some of you folks, my house is small, so anything more than flea power will just hurt your ears.

Currently due to space limitations, the Edgarhorns are not assembled, but soon will be with 2242 18" JBL subs(9 cubic ft tuned to 30hz thread) run on PE sub plate amp.

More to follow later....have to get back to work now......

Regards, Ron