Powering Inefficient Speakers with Tubes...

isRelative

isRelative

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Hello everyone!

I'm making my first foray into tube audio soon and I'd like to hear some of your opinions. I'm picking up a used Onix SP3 MKII in a week or so and was wondering what kind of tube power I'd need to be pushing to drive my speakers well.

The tube integrated amp is an Onix SP3 MKII which outputs 38 wpc @ 8 ohms.
The speakers are IMF TLS-50's with an efficiency rating of ~84 db/w.

I realize that when tube amps 'clip', they don't run as much of a risk of damaging the speaker drivers compared to damage that SS clipping may cause. Even so, I'd like to hear your opinion on this matchup. Thanks!

Best,
isRelative
 
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I have a Jolida push pull amp with about 20 watts per channel and one time I drove the 85db Advent/3s with no problem
 
I went thru all that a bit back and had some help from a couple of the wizz ... er ... whiz kids here on AK. My speakers are large - McIntosh XR16's - and run 91db efficiency, plus, I like LOUD. Took some SPL readings and I'd be cranking around 95db average with peaks in around 105db.

Eh? What you say?

I said ... I'd be cranking around 95db average with peaks in around 105db. :D

Anyway, we all decided that the standard 20-35wpc wasn't gonna do it and keep me happy, so I decided on a Latino ST-120 kit. That's conservatively rated at 60wpc, and more like 70wpc real world.

Get's rave reviews, and I think it's a right nice piece of kit. Haven't quite got it built yet ... but getting close ... real close ...

wiring-session3-full.jpg


So ... long story short ... depends on what you want to do with it. Room size and your musical preferences are also important and have to be factored in.

Oh. Tube watts ARE bigger than solid state watts because of the soft clipping you mentioned. Where a typical SS will be trashing your ears (and maybe your speakers too) a tube amp properly set up will distort, but not so's you'd notice as much.
 
Of course it all depends on how big a room and how loud you want it. With that caveat in my living room at my levels I don't think I'd have any problem driving 84db speakers with it.
 
I'm in a small apartment room so the loudest I turn my music up to is moderate listening levels, but sometimes when my roommate is out I like to "blast" it (and even then it's not that loud haha). 38 tube watts into a pair of 84 db/w speakers...Hope it sounds alright :P
 
The 97dB sensitivity stated on that page is misleading. It is measured at 40 watts input instead of the usual 1 watt input. That would translate into an effective sensitivity in the low 80s dB at 1 watt.
 
skriefal said:
The 97dB sensitivity stated on that page is misleading. It is measured at 40 watts input instead of the usual 1 watt input. That would translate into an effective sensitivity in the low 80s dB at 1 watt.
Click to expand...

I thought they were 97 db/w when I first got them too. Upon hooking it up to my SS integrated amp, it didn't feel like 97 at all. I asked some knowledgeable people and they said it was closer to ~83 or ~84 db/w, which is fairly inefficient. I'm just wondering if I'll have problems ahah
 
I have the same speakers - I push them mostly with a 50-55W SS receiver.

I've heard, but not sure how true this is - that tube watts are roughly equivalent to 2x SS watts. So my tube equivalent is 25-28 tube watts or your tube amp will be 76 SS watts. IF this correlation were true, you'd be providing more power than I am, and I don't think they're being choked off now - they sound great.

But judge it when you get the amp in house - see what you think.

I see you're selling a nice SX-1050 - if you get the tube amp in before you sell that, you can compare the two and see if you think the tube setup is lacking power. . .
 
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If the speakers have a sensitivity of 83 db, which sounds about right (It would be just 81 db working backwards from the 97 db @ 40 watts they claim if the speakers were 100% linear, which they aren't) Expect about 94 db 10' from 2 speakers. Add 3 db if you put them in a corner. While hardly concert levels, Thats pretty loud, considering in a survey conducted here on AK found most of us, Including myself enjoy music in the 80 - 90 db range. Also they recomend 30 - 70 watts, so I think your good to go.

While Tube watts are the same as SS watts, The Soft Clipping Characteristic's of Tubes, for commercial use allow the Tube amp to play up to 6 db louder than the SS Amp. But I don't recomend clipping a Tube Amp for home use. Still SS Amps for home use IMO should be kept -3 db from clipping to be safe, Giving the Tube Amp 2x the usable power as suggested by captouch in post #9.
 
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isRelative said:
There seem to be some countervailing opinions in this thread :(
Click to expand...

Actually if you read the posts closely, all these posts are pretty much in argeement that you should be fine with 38 wpc for most situations. sKiZo's requirements for more power into more sensitive speakers is justified if you like you music Loud, which might be defined as an extra 10 db. 10 db + the 97 db I estimated in post #10 with the speakers in a corner is more than the 105 db he achieves. And FidgetMaster suggestion of 97 - 98 db SPL's (if he's reffering to SPL's in your seat) is dead on with my recommendations with the speakers in a corner.
 
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charles 1973 said:
Actually if you read the posts closely, all these posts are pretty much in argeement that you should be fine with 38 wpc for most situations. sKiZo's requirements for more power into more sensitive speakers is justified if you like you music Loud, which might be defined as an extra 10 db. 10 db + the 97 db I estimated in post #10 is more than that. And FidgetMaster suggestion of 97 - 98 db SPL's (if he's reffering to SPL's in your seat) is dead on with my recommendations when the speakers are placed in a corner.
Click to expand...

Normal listening is between 90 and 95 dB for most all kinds of music. But do not forget about crest factor. This 90 dB is an average, but to avoid significant distortion you must have at least 10-15 dB of headroom to accomodate occasional peaks. Whatching meters on my power amplifier I saw 3-5 Watts average with peaks over 200. Granted it was a high resolution record (24/192), which was practically a digital transfer of analog master made in early 1960s. With CD you will likely see less demand for peaks. ut still well mastered CDs require enough headroom. With low power tube amps like SET, I wouldn't even look at speakers with less than 95 dB/W efficiency. That excludes most of modern speakers. Another consideration is to require speaker impedance to be fairy even within most of audible range. Tube amps have high output impedance and their interaction with speakers may produce large ups and downs in volume when speaker impedance swings widely.
 
ALL I'D ADD ... (HOLD ON - LET ME TURN IT DOWN)

There ... <bonk bonk is this thing on?> ... all I'd add is that how you measure the room is important too. I find that guesstimating sound pressure levels is hit or miss. If you're seriously into getting it right the first time, you should think of investing in a decent SPL meter so you know EXACTLY what's happening in your room. That's my trusty old BSR bottom left of the monitor ... I like it because it does slow averaging so it's easier to get actual usable data.

monitor.jpg


An indispensable part of any serious listener's kit. For best results, take actual readings right at the listening position(s). Set you back $20-30 on the bay, or get a shiny new one at ratshack for $50. Or maybe borrow one if you know any other audio addicts. Real average measurements will probably surprise you as they do tend to be louder than your estimates.

And yes, DO plan on headroom. Ditto here on the 2-3WPC averages with regular excursions to OMG we're all gonna die! when the meters peg at 200wpc on instantaneous peaks ... Worth remembering, if you get too many watts, you can always turn it down. Not enough, and it's like ... forever not enough.

** Of course, all this measurement stuff assUmes you have an existing system to get sound levels from ... for a newbie with no system, I'm told another trick is to read the manuals on your power tools and vacuum cleaners, and use the db levels listed for those as base reference levels, or just have the SO and so stand across the room and start yelling at you, and make a note where it get's too hard to handle ... then again, for me, that was many years ago ... <G>
 
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