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Old 9th January 2005, 12:21 PM   #1
MlinarS is offline MlinarS  Canada
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Question 89 db is it enough ?

Hi everione,
I'm new to this forum and (almost) new to DIY tubes. I would very much appreciate if you would gave me opinion on the following:

My room is of a moderate size 10' X 24' X 9'. My speakers are old Altecs Lansing 1012 with sensitivity of 89 db. I'm thinking to build SE but I'm not sure if 4-5 W would be suficien to drive this speakers. Altough, I have built a tube preamp before I don't have experiance with tube amplifiers.
Also, if somebody would sugest output tubes for this project. This is my first project so I don't wont to start with something very expensive and complicated. I'm not very much interested in kit building. Thanks for your help.
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Old 9th January 2005, 12:40 PM   #2
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hi and welcome into the DIY-swamp 8-)
i think EL84 would be a good start..
and, yes, 4-5W SE would be sufficient if you don't intend to play at partylevels..
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Old 9th January 2005, 12:42 PM   #3
SY is offline SY  United States
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If you listen to music very quietly, you might get by. But let's see how limited this setup is. Let's assume that when you say "89 dB" you're saying "89dB/2.83V/m." And let's further assume a frequncy region where the impedance actually looks like 8 ohms. In that region, 1 watt will give you 89dB at a meter, 4W will get you to 95dB on peaks. Move away to a more reasonable 2m listening distance, and the peak SPL drops to 89dB. That's not terribly loud and you're running the SE amp in the power range where its distortion performance is likely to be terrible. And remember, these are PEAK sound levels, not average- the average SPL is more likely to be 20dB or more below this, say 65-70dB.

Two solutions: more sensitive speakers (like 95dB/2.83V/m or better) or an amp with decent power and distortion performance (i.e., not SE).
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Old 9th January 2005, 01:19 PM   #4
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Quote:
Originally posted by SY
And remember, these are PEAK sound levels, not average- the average SPL is more likely to be 20dB or more below this, say 65-70dB.
If one listens to mostly modern pop music, you might be able to get away with only 4-5W. The difference between average and peak levels nowadays is strictly much less than 20db and usually less than 10db. I was happy enough with 89db/w/m speakers and 3W 90% of the time. My room is a little smaller and I'd say I listen at a slightly lower level than most other audiophiles.

If you have more omnivorous tastes and in particular if you listen to large scale classical it wont be anywhere near enough - IMO.
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Old 9th January 2005, 03:06 PM   #5
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I've got some slightly "power-hungry" speakers,(not sure of the efficiency,they were homebrewed by my father 20+ years ago,he said the efficiency was kinda low.) and I use a PP 6V6 amp (~8wpc,before any real signs of distortion.) and have plenty of volume.Granted,my room is fairly small,at something like 12'x12',but it can rock the house!
I'm the type of guy who likes to occasionaly listen to Metallica or Pantera at concert-volume,and even with only 8wpc,in a smaller room,it's loud enough to get there! Not to mention it sounds good!
(Yes,even Metallica and Pantera can sound good through tubes!)
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Old 9th January 2005, 03:44 PM   #6
Sherman is offline Sherman  United States
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Default Re: 89 db is it enough ?

Quote:
Originally posted by MlinarS
...My room is of a moderate size 10' X 24' X 9'. My speakers are old Altecs Lansing 1012 with sensitivity of 89 db. I'm thinking to build SE but I'm not sure if 4-5 W would be suficien....

As everyone else has indicated it really depends on how loud you like to listen. My current tube amp is 8W (probably 4.5W RMS) per channel. I initially listened to it using a pair of Advent/1 speakers which I believe are between 87 and 89dB 1W/1M. For me, in my listening room (13' x 18') 8W was plenty.

I'm currently collecting the parts for a pair of SE monoblocs that should have about 4 or 5W (3W RMS). For probably 90% of my listening (maybe more) 4W should be enough if I used the Advents.
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Old 9th January 2005, 05:23 PM   #7
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You'll be happier with 20W. Make a 6V6 class AB PP or 6L6 class A (maybe triode) amp. Although if this is your first project, I would definetly recommend an SE amp. 6V6, EL84, 6L6, all easy to use.

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Old 10th January 2005, 06:45 AM   #8
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Default HOW MUCH POWER?

Let's make things clear -- if your loudspeakers are 89dB/W/m, and the room size is the stated -- 4-5W are quite enough, unless you listen to headbanger music or whatever!

Secondly, let's make things clearer:

Quote:
Two solutions: more sensitive speakers (like 95dB/2.83V/m or better) or an amp with decent power and distortion performance (i.e., not SE).
More sensitive speakers is not the issue here! The guy already said his speakers are defined (maybe one day he will change);
further, more efficient speakers are a compromise road, just like any other.

Decent power and distortion performance? Not SE? What is this about? Do I feel bad vibes about SE? Well, if it was a garden variety SE, meaning 300B with 8-9W per channel, it would have both enough power (more than 4W) and distortion performance (all lovable 2nd order) and a sound better than the guy has ever heard in his room!

What is it that PP could offer, especially to a novice? I know that "de gustibus nihil discutandum est" -- but guys, that was a question from a novice, give him a break... and some credit!

When it comes to 4-5 (and more) W of SE power, with decent distortions etc. -- those who have not yet done it, might take a look at my site (before I close it for renovations, i.e. adding new designs). The site is as listed below the reply.

Regards to all!
Aleksandar
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Old 10th January 2005, 07:00 AM   #9
MlinarS is offline MlinarS  Canada
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Thanks everione for repply. Sorry I didn't mention that I live in the appartment so the loud listening is out of question. The music I listen to is Lorrena McKennit, Diana Krall type and some clasical music.
Quote:
....i think EL 84 would be a good start.....
I was thinking about this tube to.


Quote:
...more sensitive speakers (like 95 dB/2.83V/m or better)....
The speakers I have are temporary solution 'til I faind somebody here in HK to build boxes for a new speakers I'm planing to design. ( I recently moved to HK from Canada, temporary).

Quote:
...If this is your first project I would definetly recomand an SE amp....
This is exactly reason I was thinking about an SE.


Thanks everibody for replies.
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Old 10th January 2005, 09:05 AM   #10
Mike C is offline Mike C  United Kingdom
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Default 89dB etc

I use 89 to 90dB speakers in a room 18ft x 14ft, driven by a 300B SET which gives
6.5watts (measured). This is a bit lower than the normal 8watts, due to having the
OPT set to 5kohms rather than the more normal 3kohms. I believe the gains in
sound quality are a good tradeoff for the minor (in dB terms) power loss.

I have no problem with volume levels at all. In fact, I can listen fairly comfortably
from an adjoining room.

Now my 300B amp was designed to give good dynamics, with a seriously
strong driver stage; I'd say that this makes as much difference as say a doubling
of output power. This amp has its own PSU for the driver; this is a tridoe/pentode
mu stage with low output impedance and wide voltage swing of +/- 150V; and
it has its own PSU of adequate voltage for the mu stage (490V).

I just had to post when I saw you mention Loreena McKennit!
Mmmmm, she is a great favourite of mine.
Please please please hear her though a nice SET amp!
Oh, the lovely delicate subtle nuances to her singing; the expression of her
near whisper; and then when she so smoothly transitions into full singing and
of such quality, it makes my spine tingle!
It just has to be a 300B SET (in my biased personal view) to really get all this ...
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