Recently I decided to build my own pair of speakers using the Planet_10 mini onken design with alpair 10 drivers. Since this is my first pair of real speakers, I need to get an amplifier.
After looking at some thrift stores (seem to have cheep stuff), I remembered that my dad had an old tube amplifier from my Uncle that he is not using (a Grundig Stereomeister 300). I believe it was a high quality amplifier back in the day, and my dad said it sounded good with his speakers (I have included a link to the model below).
My concern is that this amp only outputs 7 watts per channel. Would this be enough to drive the alpair 10s (87db efficiency)? I live in an apartment and do not need a lot of volume, but don't want to have to strain to hear the speakers either. The room the speakers will be in is ~20' by 14'.
Any insight you could provide will be appreciated.
Stereomeister 300a Radio Grundig Radio-Vertrieb, RVF, Radiow
After looking at some thrift stores (seem to have cheep stuff), I remembered that my dad had an old tube amplifier from my Uncle that he is not using (a Grundig Stereomeister 300). I believe it was a high quality amplifier back in the day, and my dad said it sounded good with his speakers (I have included a link to the model below).
My concern is that this amp only outputs 7 watts per channel. Would this be enough to drive the alpair 10s (87db efficiency)? I live in an apartment and do not need a lot of volume, but don't want to have to strain to hear the speakers either. The room the speakers will be in is ~20' by 14'.
Any insight you could provide will be appreciated.
Stereomeister 300a Radio Grundig Radio-Vertrieb, RVF, Radiow
Listening room size and musical taste definitely have an impact on power requirements. Having said that, Paul Joppa has provided us with a useful rule of thumb, for assessing amp/speaker combos. Joppa's rule states that in a "typical" listening space and amp/speaker combo should be capable of producing 102 dB. SPL peaks at a 1 meter distance. Unfortunately, it's quite obvious that 7 WPC will be grossly inadequate in combination with 87 dB. sensitive speakers. Mid 90s sensitive speakers are an appropriate match for a 7 WPC amp.
Boy, back in the day when the tube really was just another ugly piece of electronics to hide in a case. Now we like out tubes on display.
I think eli's point is good, but you may be able to get away with it if you really don't crank it. Your room isn't too big.
If you listen at 3 meters, you may only get 78 dB with 1 watt at the listening position, not accounting for any room gain. 2 watt = 81dB, 4 watt 84dB, 8 watt only 87dB. If you want 20+ dB headroom for a well recorded piece of music with a good dynamic range, you can't turn it up too loud. Average 65-70 dB at listening position. Higher if you listen to highly compressed modern music.
That being said, I find, in a 10' x 12' listening room, at 6' listening, I don't put it up much beyond 63 dB, I find it loud enough.
I think eli's point is good, but you may be able to get away with it if you really don't crank it. Your room isn't too big.
If you listen at 3 meters, you may only get 78 dB with 1 watt at the listening position, not accounting for any room gain. 2 watt = 81dB, 4 watt 84dB, 8 watt only 87dB. If you want 20+ dB headroom for a well recorded piece of music with a good dynamic range, you can't turn it up too loud. Average 65-70 dB at listening position. Higher if you listen to highly compressed modern music.
That being said, I find, in a 10' x 12' listening room, at 6' listening, I don't put it up much beyond 63 dB, I find it loud enough.
I'm using my 300B amp which delivers 10 W per channel. I have no trouble driving it to ear-splitting volumes (>100 dB SPL at the listening position 1.5 m from the speakers) even with my 87 dB efficient speakers.
Recall, you have two speakers (+3 dB) and the room has some reverberation ("room gain" +4-5 dB) so it only takes about 2-3 W to drive the SPL to 100 dB(A) with those speakers. 100 dB SPL is enough to make my ears ring for hours. I tend to listen at around 80 dB SPL when I'm enjoying the music. Lower for background noise.
~Tom
Recall, you have two speakers (+3 dB) and the room has some reverberation ("room gain" +4-5 dB) so it only takes about 2-3 W to drive the SPL to 100 dB(A) with those speakers. 100 dB SPL is enough to make my ears ring for hours. I tend to listen at around 80 dB SPL when I'm enjoying the music. Lower for background noise.
~Tom
It all comes down to: "How loud is loud?" I'm sure it will be adequate for background music, but beyond that is subjective. I have a little PP EL84 amp that puts out only 7-10 watts a side. Right now it's powering a pair of "Overnight Sensations" which is a speaker kit put out by Parts Express. Supposedly, the 4" woofers only have a 83 db efficiency and it's more than enough volume for me. They're in a medium sized bedroom.
Definitely take the Grundig and do everything necessary, including obtaining appropriate speakers, to put it back doing what it should, playing music. Fine "vintage pieces, like that, do not belong on museum shelves. They were built to play music, not be gawked at!
The ELL80/6HU8 O/P tubes the Grundig uses are scarce. Scrounge up at least 1 set of spares and more sets would be better. At least 1 unit I've seen (by Fisher) competes for the limited stock that's available.
The ELL80/6HU8 O/P tubes the Grundig uses are scarce. Scrounge up at least 1 set of spares and more sets would be better. At least 1 unit I've seen (by Fisher) competes for the limited stock that's available.
That may be true, but Beethoven's 5th will not thunder properly.
Match amps and speakers sensibly.
Like so many considerations in tube audio, the question of so-called speaker efficiency ( a misnomer at best as loudspeakers are hardly efficient at all at converting input energy into output energy...in most cases 10 percent or less...if memory serves) is a bit of a red-herring.
Some notoriously inefficient? (I call them, insensitive) loudspeakers such as the Rogers LS3/5 a and variants as well as numerous KEF, Celestion loudspeakers with 90db/( at 1 watt at 1 meter) and under published sensitivity ratings turn out to be extremely well-suited even for low-powered tube amplification be it SE or PP topologies.
Here's an interesting link and read that provides some insight into the matter:
http://komkris2000.webs.com/The story of Tube Friendly Speakers.pdf
As regards the ability of the Planet 10 Onken designs...there must be plenty of fellows here at DIY with real-world experience harnessing these loudspeakers to low power-tube amplification who would be able to tell you what they are capable of in terms of SPL...(Cal? Dave..et-al?)
Published speaker sensitivity specs IMHO are not usually sufficient in my experience to automatically preclude the use of low-power tube amplification to drive them to sufficient listening levels...I currently use a small 4.5 watt SET amp (EL84 based ) and have yet to encounter an electrodynamic loudspeaker it won't drive to sufficiently LOUD levels...mind you AlNiCo based drivers do produce higher Spls on average over their Ceramic brethren.
In addition to room size, room treatment, the ability of the tube amp in question to deliver dynamic reserves, signal source etc etc...all contribute to the ability/or inability of a low-power (indeed, of any amplifier) to deliver SPL sufficient for your taste or habits...how loud is loud? is a very good question.
Although my experience is purely anecdotal and subjective I find that that the beauty of low-powered tube amplification is its ability to maintain the musical detail of the source signal at very low volumes...best regards. Leon
Some notoriously inefficient? (I call them, insensitive
) loudspeakers such as the Rogers LS3/5 a and variants as well as numerous KEF, Celestion loudspeakers with 90db/( at 1 watt at 1 meter) and under published sensitivity ratings turn out to be extremely well-suited even for low-powered tube amplification be it SE or PP topologies.Here's an interesting link and read that provides some insight into the matter:
http://komkris2000.webs.com/The story of Tube Friendly Speakers.pdf
As regards the ability of the Planet 10 Onken designs...there must be plenty of fellows here at DIY with real-world experience harnessing these loudspeakers to low power-tube amplification who would be able to tell you what they are capable of in terms of SPL...(Cal? Dave..et-al?)
Published speaker sensitivity specs IMHO are not usually sufficient in my experience to automatically preclude the use of low-power tube amplification to drive them to sufficient listening levels...I currently use a small 4.5 watt SET amp (EL84 based ) and have yet to encounter an electrodynamic loudspeaker it won't drive to sufficiently LOUD levels...mind you AlNiCo based drivers do produce higher Spls on average over their Ceramic brethren.
In addition to room size, room treatment, the ability of the tube amp in question to deliver dynamic reserves, signal source etc etc...all contribute to the ability/or inability of a low-power (indeed, of any amplifier) to deliver SPL sufficient for your taste or habits...how loud is loud? is a very good question.
Although my experience is purely anecdotal and subjective I find that that the beauty of low-powered tube amplification is its ability to maintain the musical detail of the source signal at very low volumes...best regards. Leon
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Thank you all for your responses.
It sounds like it might be on the edge.
As Johnny said "How loud is loud." I wish I had an answer to that question. I know 90db at the listening position is way too loud and would cause my neighbors to hate me. I do not have good references for for other decibel levels, though it would seem like a max somewhere between 70db and 80db at the listening position would be reasonable (~3m away).
How important is the 20db headroom? is it reasonable to cut it to 15db for most music? If this were ok and the fact there are two speakers and room gain were considered, I think it may be acceptable. And I can always pick up a cheap solid state receiver if there is the need to play loud (I may have to anyway, as I suspect that my girlfriend will have limited patience for letting tubes warm up).
The problem is the amplifier would have to be shipped to me unless I want to wait until July (and I don't). Thus, I would have to commit a bit of money to try it out (the reason for the forum post).
It sounds like it might be on the edge.
As Johnny said "How loud is loud." I wish I had an answer to that question. I know 90db at the listening position is way too loud and would cause my neighbors to hate me. I do not have good references for for other decibel levels, though it would seem like a max somewhere between 70db and 80db at the listening position would be reasonable (~3m away).
How important is the 20db headroom? is it reasonable to cut it to 15db for most music? If this were ok and the fact there are two speakers and room gain were considered, I think it may be acceptable. And I can always pick up a cheap solid state receiver if there is the need to play loud (I may have to anyway, as I suspect that my girlfriend will have limited patience for letting tubes warm up).
The problem is the amplifier would have to be shipped to me unless I want to wait until July (and I don't
). Thus, I would have to commit a bit of money to try it out (the reason for the forum post).
It depends a lot on your hearing. Older people have -6dB at all frequencies and -40dB at the upper frequencies, so they need 4x to 10x the power output. If you are younger, then 7W is enough. If you are old, then you need 25W.
I drive my Alpair 10.2's with 45's (single ended), and I don't even use full output, because that would be too loud. My room size is smaller, however.
I drive my Alpair 10.2's with 45's (single ended), and I don't even use full output, because that would be too loud. My room size is smaller, however.
Just to quantify my statement, my listening distance is ~6m, and my room (which I've never actually measured) is about ~11m x ~15m.
I agree with Eli.
I just finished building a 7W RMS (measured) amp and am using it with 97~98dB loudspeakers. It is "just" loud enough for my taste.
Of course I don't listen to it full out all the time.
Scott
I suppose the other option would be to switch to a different speaker design. It would be unfortunate because the alpair 10s just got shipped, and I was looking forward to building the mini onkens.
Are there any other speaker designs that I should consider that would be approximately bookshelf size, stand on their own without needing a subwoofer, and be more efficient?
Are there any other speaker designs that I should consider that would be approximately bookshelf size, stand on their own without needing a subwoofer, and be more efficient?
I suppose you've seen the voltage test mentioned in my sig line? All you need is some form of digital playback (CD, DVD, computer, iPod) and a voltmeter with a 2V or 20V AC scale.
The test will at least tell you were you are. I suggest using a more powerful amp for the measurement, that way you know you aren't clipping it a top levels. What you measure there will apply to your 7WPC tube amp.
The test will at least tell you were you are. I suggest using a more powerful amp for the measurement, that way you know you aren't clipping it a top levels. What you measure there will apply to your 7WPC tube amp.
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