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Old 14th March 2010, 03:45 AM   #11
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Quote:
Originally Posted by SDB777 View Post
Exactly how many watts do I need to make some Polk Audio Monitor 40 active? I don't need ear drum splitting SPL, I like quality.
Irrespective of amplifier type, here is an interesting study on the dynamic range of well recorded music and power requirements.
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Old 14th March 2010, 08:27 AM   #12
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Quote:
Originally Posted by Loren42 View Post
Your speakers are 89 db/W/m. That isn't too bad.

You could do with some lower wattage amps, but the reason for having horse power isn't the need for high volume, it is for dynamic range.

Normal listening doesn't require high wattage, but the transients in the music can generate a lot SPL and if the amp doesn't have the reserve available, you get clipping for an instant and you lose that dynamic range.
Exactly. That's why you want to have more under the hood then you're actualy using.

I'm having a 60W PP Amp here with 89dB speakers and I'm staying well within the beginning range of the volume control.

I too think that you're well off with a Dynakit. But if you want to do it from scratch, you might want to take a look at this thread.
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Old 14th March 2010, 01:47 PM   #13
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The best stratergy is to build a pair of fullrange speakers at about 100db efficiency and then build a nice 7watt PP amp to drive them. In the end this will perform better giving you loads of microdetail and punch, and will undoubtedly end up costing less than building something with expensive KT88's and big output transformers. Current production EL84's will fit the bill and sound wonderful. I could do all this for about $400.00.

Shoog
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Old 14th March 2010, 02:00 PM   #14
Loren42 is offline Loren42  United States
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Quote:
Originally Posted by Shoog View Post
The best stratergy is to build a pair of fullrange speakers at about 100db efficiency and then build a nice 7watt PP amp to drive them. In the end this will perform better giving you loads of microdetail and punch, and will undoubtedly end up costing less than building something with expensive KT88's and big output transformers. Current production EL84's will fit the bill and sound wonderful. I could do all this for about $400.00.

Shoog
I wonder. I have a lot more in my speakers than that and as you go up the ladder of SPL efficiency your choices of drivers gets smaller and smaller.

However, I am a fan of high efficiency speakers.
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Old 14th March 2010, 02:07 PM   #15
Loren42 is offline Loren42  United States
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I should add that if you want another, or even better alternative to Dynaco equipment, Bruce's OddWatt kits are available Here. Not as cheap at Dynaco, but this is a modern kit with a high degree of fidelity.

Highly recommended.
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Old 14th March 2010, 02:21 PM   #16
SDB777 is offline SDB777  United States
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This is amazing information! Certainly glad I joined this site!!


The ST70 kit certainly looks to be a wonderful amp....thanks to all!

With that said....
I do not have advanced testing equipment(Fluke 88 is all I own and I don't use it very often). My soldering skills are okay(could always use more practice-but then couldn't we all). And I have no problem following schematics.
Are there any things that I would need to 'know' before ordering this kit? Problems, quirks, etc?


For now, I'll be sticking with the Polks....but I will be making a set of DiY speakers! And I'm sure there is plenty of good reading to be done here!!






Scott (great group here...thank you) B
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Old 14th March 2010, 02:37 PM   #17
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Shoog,
you can build the 'same' amplifier for 100$ or 1000$ without problems and it realy doesn't matter that much whether it has 7 or 20W, much more which components you use. Not everyone necessarily wants to build new speakers around the amplifier, more likely the other way around.
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Old 14th March 2010, 02:45 PM   #18
Loren42 is offline Loren42  United States
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Quote:
Originally Posted by Herr Grau View Post
Shoog,
you can build the 'same' amplifier for 100$ or 1000$ without problems and it realy doesn't matter that much whether it has 7 or 20W, much more which components you use. Not everyone necessarily wants to build new speakers around the amplifier, more likely the other way around.
I would like to know the sources for components for a total of $100.

Just my transformers alone cost me $400 with shipping. Tubes were over $200. By the time I was done with all the rest of the parts I was just over $1,000.

Seems that I overpaid for everything by a factor of 10.
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Old 14th March 2010, 04:09 PM   #19
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Originally Posted by Shoog View Post
The best stratergy is to build a pair of fullrange speakers at about 100db

It's a great strategy provided you like the way the 100db speakers sound. I haven't been able to find such speakers irrespective of price.
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Old 14th March 2010, 06:36 PM   #20
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Of course all this is a matter of personal opinion.
I have some vintage Isophon drivers in BIB cabs which have done me well for about 7yrs now. Detail is where they win over most speakers. The last pair of speakers I owned which I really liked was a pair of Spender BC1's which were really nice.
I have heard some Fostex full rangers in back loaded horns and didn't like how they sounded at all - very forward and a bit grating.
The vintage 50-70's Alnico magnet drivers from old consoles have consistently nice natural sweet sounds in my experience and I think the Grundig,Isophon, Telefunken and Saba are probably the best - and available second hand at very small money. Without the wastage of a crossover they will sing at 2-3watts so 7watts presents plenty of headroom. Not suitable for heavy rock music but capable of most other styles. Mine handle the occasional techno session.
My current 7Watt 6080 amp is a giant killer and cost very little to build. The whole world of sweep tubes open up before you if you can keep the power demand reasonable.

I stand by my recommendation, and my claim that it can be done nice and cheaply. Still its all about the choices you are prepared to make along the way.

Shoog

Last edited by Shoog; 14th March 2010 at 06:38 PM.
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