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Old 28th August 2011, 03:16 AM   #1
mfaughn is offline mfaughn  United States
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Default What is needed to drive 86db speakers and sound *good*?

Right, here's where I'm coming from. Speakers == Snell Aiii. Lately powered by a modded Magnavox 9303 (PP EL84 pentode connection). Sound is respectable. Tried with my friends Pilot A260 (UL EL34 PP) and that sounded noticeably better -- soundstage wider and closer, bass, definitely more engaging.

The perhaps very naive knee-jerk assumption is that these speakers woke up with more power. However, I've been hanging around here long enough to suspect that there is quite possibly a less than astute assumption. There are several ways I could nuance the question but I'll leave it "dumb"...What will it take to make these speakers shine? I don't need to shake the house, just a good solid room filling spl. The EL84 PP gets loud enough for the most part.

I have several options on what to build next. I have iron for UL EL34 PP, some fairly nice 4.4K PP / 25W iron, a set of Z565 (still in STA35), and have an interest in something like the Engineer's Amp. I have to stay fairly budget oriented, meaning buying iron and tubes for (e.g.) a KT88 PP is more than I can swing at the moment. Would most like to use either of the first two sets of iron mentioned.

I've asked here and there already what I should do with this or that iron but I wanted to back up a bit further away from this in order to perhaps get a better view.


PS -- FWIW a lot of Snell Aiii owners swear by big SS power. I've tried that and though the Nak PA7 sounded nice and imaged well it lacked low end oomph and was kinda lifeless (though less so than some other SS). Other SS has just fallen far short of the goodness of even my humble Magnavox amp.
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Old 28th August 2011, 04:17 AM   #2
jcx is online now jcx  United States
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Default I doubt "tube watts" are enough "bigger"

something north of a kW to reproduce "live" peak dynamic SPL

yes, yes someone's sure to be along with: "you will go deaf at those levels" - it is boring and naive - people saying that simply do not understand live music dynamic peak requirements, the short durations, peak vs average level, live (acoustic) Orchestral SPL...

if you only listen to "Loudness War" dynamic range compressed pop music with 6 dB (or less!) peak-to-ave you can get by with lots less - even your 25 W would be "too loud" with that "music"

Last edited by jcx; 28th August 2011 at 04:24 AM.
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Old 28th August 2011, 04:28 AM   #3
ChrisA is offline ChrisA  United States
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Originally Posted by mfaughn View Post
Right, here's where I'm coming from. Speakers == Snell Aiii. Lately powered by a modded Magnavox 9303 (PP EL84 pentode connection).
Try a bi-amp. Use the el34 iron for the two bass channels and smaller transformers for the two treble channels. I think you'd be best off with an active solid state crossover. Maybe even keep the Magnavox if you like it but power the bass with a new EL34 amp.

Many people who use a bi-amp use the same amp design for both bass and treble. I think that is a bit of a waste. You can build a better amp if you know 100% certain that the freq. range will be limited. Hammond organs were built like that as are most newer studio monitors. A bass amp can stand a bit more negative feedback than you'd otherwise like because those annoying higher harmonics get filtered out. NBF can give very tight bass and you don't need to worry about if it makes the highs sound bad.

Actually, I think this is why like music always sounds better then HiFi. Even live music that is played through amps and speakers like a rock band. My theory is that the band uses one amp and speaker for each instrument and each is a special purpose design just for the sound of one instrument.

Last edited by ChrisA; 28th August 2011 at 04:43 AM.
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Old 28th August 2011, 04:58 AM   #4
ChrisA is offline ChrisA  United States
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Originally Posted by jcx View Post
something north of a kW to reproduce "live" peak dynamic SPL"
I agree 100%.

That was the reason I suggest a bi-amp system. Lets him keep his current amp that he like but adds power from a new EL34 bass amp. His current magnizox amp will sound better if it is not driving the bass, takes a big load off the amp.

But in the end it's just about power. Those old 85db speakers need tons of it. I have a pair of older Infinity Quantum II and they are the same say. I need about 100WPC of very clean power.

That said, it's really about dynamic range. Power is only a means to that end. Another means is to buy some very efficient speakers. I have an 8W all tube guitar amp and a 104db speaker for it. The dynamic range on this is HUGE and puts most HiFi systems to shame. And with only 8W. I think it's because of the speaker.
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Old 28th August 2011, 07:23 AM   #5
data is offline data  Australia
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My Standmount speakers are 8ohm and 86db, I drive them nicely with two EL34's per channel, PP Triode strapped AB circuit.

Sound is very good, and plenty loud enough for a modest sized room.

So,e people think UL has better bass, but I think the opposite is true and UL just has a wow factor initially, and ultimately is just distortion making it sound bigger.

Just my view...
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Old 28th August 2011, 07:45 AM   #6
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I also have a banger set of speakers I use for testing, with an efficiency in the mid 80db's. On 10W it gets loud enough to make me worry about the neighbours, with a 40W amp it is crazy loud.
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Old 28th August 2011, 11:06 AM   #7
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dunno the speakers you name, but if they are a relatively late model they will be built for SS amplification with a good stiff output, close to zero Z and damping to match. They will have a widely ranging impedance across frequencies.

Horsepower (once you have reached the stage of "enough") is not the issue - control is. If you are hung up on retaining the speakers, design your amp to suit.
"It may not be easy for some to not hear differences, even if they are not there." - Vacuphile,
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Old 28th August 2011, 11:54 AM   #8
mfaughn is offline mfaughn  United States
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Thanks for what I've heard so far. Lets focus on the image and soundstaging issues. I will of course try it but if I use my current 18W for the top end only can I expect it to come alive more? We'll see. That would really be an excellent solution.

I have biamped these before. It does seem easier to get them to stay coherent with a single amp but that isn't to say biamping them can't be done right. Snell actually made a specific active XO for these speakers that I'm trying to get my hands on. If I am going to biamp then is there a point to staying with tubes for the low end?

The Snell Aiii are somewhat of a pain in that they are really huge speakers and as we are discussing, not particularly easy to drive (though easier than some). I've owned a lot of other speakers, many quite well respected, and I keep coming back to the Snells. I've finally sort of given up trying to displace them.
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Old 28th August 2011, 09:09 PM   #9
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Given the compression problem of inefficient speakers you may never get what you really want out of them but you never know. Biamping is a good idea (maybe SS on the woofers). You know anyone with a PPP KT-88 amp that you can borrow? You may need something with a &^&*% load of NFB to drive the woofs.
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Old 29th August 2011, 12:03 AM   #10
mfaughn is offline mfaughn  United States
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Let me reiterate...my speakers sounded quite good with my friends EL34 PP UL. If I could get the same sense of space, image, presence, etc. as that amp provided I'd be happy. The question is still -- is this primarily a matter of power (18W vs. 35W) or might it be more a matter of the circuit / tubes / iron that provide the magic. All the answers I'm getting are power, power, power it seems like and frankly I just don't believe that these speakers require mountainous power (see first sentence in this post).

FWIW, Peter Snell reputedly used these speakers with a 40W SS amp.
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