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jarthel 22nd June 2007 12:01 AM

what speakers do you use?
I am trying to get a "feel" of how much power do you need for speakers. I've only built headphone amps so far.

Could you please:

1. tell me which speaker do you use (maybe a manufacturer link and effiency rating)

2. how much power does your amp produce?

Thank you very much

ps. I created the thread here as the amp i'm thinking of is a tube amp (thinking of SE but I can be swayed to PP if need be)

gingertube 22nd June 2007 02:13 AM

I use VAF Research DC-7 and DC-X from local Adelaide supplier.

These speakers are 95dB/W/m

I use them with the following amps:

Ultralinear Push Pull EL84 - approx 10W per channel (+10dB power)
giving 105 dB SPL at 1 metre max

Ultralinear Push Pull 6V6 - approx 8W per channel (+9dB power)
giving 104 dB SPL at 1 metre max.

845 SET - approx 20W per channel (+13 dB power)
giving 108 dB SPL at 1 metre max

The maths:
dB (power) = 10 log (output power).
Add that to the speaker efficiency in dB/Watt/metre to get max Sound pressure level (SPL) at 1 metre.

And as Eli said in his post you want a minimum of 102 dB SPL for a typical sized room).

Thats why you see you see the guys who build those little "Flea Power" SET amps of around 2 watts use 101 dB/W/m speakers with them.

Aside: The reason I like the VAF speakers is that they have really good self damping characteristic and therefore sound good with low damping factor valve amps. That means I can design the amps with very little or no global feedack because, within limits, the output impedance of the amp is not a problem.


jarthel 22nd June 2007 06:14 AM


Originally posted by gingertube
I use VAF Research DC-7 and DC-X from local Adelaide supplier.

I was looking their website and it seems the DC-7 and X are about at 92+ efficiency.

I've seen your place and I would guess my living room would be about the same size.

How loud can the amp + speakers get?

Thanks gingertube :)

gingertube 22nd June 2007 06:30 AM

With the DC-X (95dB/W/m) and any of the amps (8 to 20W per channel) it gets louder than I can tolerate staying in the same room.
Then 6V6 Ultralinear (the 8 Watt amp) tends to start to grunge up a bit when pushed really hard so I don't use it for really loud listening.

If you are doing nothing tomorrow (Sat) or Sunday give me a buzz to check I'm home (82693539) and pop in for a listen to the 3 amps on the DC-Xs. I also have an AKSA Lifeforce55 SS Amp for comparison (55W into 8 Ohms and 90 W into 4 Ohms) which should deliver around 70 W into the nominal 6 Ohm DC-Xs. I should be around as a another fellow is popping in to pick up a couple of guitar amps I've just finished repairing for him.

Strangely I did'nt really notice the difference in the sound level with the DC-7 although I only had them for about a week. I'm currently contemplating upgrading the DC-X (older model not the new Generation 4) to a pair of I-91.

Keruskerfuerst 22nd June 2007 06:44 AM

1. Loudspeakers: self constructed and self build. Semi-active 4 way. Sensitivity: ?
2. Two power amps: 2x300W and 2x400W into 8Ohm.

arnoldc 22nd June 2007 07:38 AM

Speakers: DIY- 10" Altec 406-8Y + Oxford mid horns + Fostex FT17H, Efficiency ???
Amps: 0.9W 10Y, 1.2W 45, 3W 2A3, 3W 50, 6W 300B
Room: 4m x 4m x 3.5m

Plays LOUD and rocks with a 10Y amp

Klimon 22nd June 2007 09:34 AM

Amps: flea-powered SETS 1-2W: el84 / double dc darling / 6ck4

Speakers: modified vintage two-way bookshelfs: Fisher and Sansui SP-50, both around 89db/W, minimal crossovers components (zobel and cap on tweeter)

Turning the volume all the way up would be deafening in my quite small room BUT at normal listening levels there is some loss of dynamic range when I compare with el34PP (30W) on the same speakers or the tiny sets on 96db/w backloaded horns. Although mighty PP is better suited to drive the bookshelfs I still prefer them with the tiny sets so apparently not all stands or falls with dynamic range.

I think decware puts it about right when they say their <2W zen works with speakers of 90db/W but 96db/W is ideal. (given a not too large room and speaking in real-world terms, not theoretical should-be's)


adason 22nd June 2007 10:52 AM


I am trying to get a "feel" of how much power do you need for speakers.
speakers: 18" cervine vega pa woofer, compression horn midrange, horn tweeter
amp: 2watts el84 se
normal listening level 10-200 mwatts, 0.5 -1 watt way too loud

speakers: line array (8 4" midranges, 6 line source tweeters, 2 15" woofers)
amps: 20 watts push pull 6V6 for mids/tweets, 150 watts solid state for woofers
nornal listening level again 10-200 mwatts, 2-20watts party level

power needed depend on speaker sensitivity and the highest spl level you will eventualy need, for normal listening level less than 1 watt is enough

kstagger 22nd June 2007 12:42 PM

Right now I'm using vintage 1978 era Altec 'Model 15' speakers - nothing all that great - but at least it does use the 802-8G tweeter. I'm not too keen on the WE designed horn (it has a 90 degree turn) or the 12" foam surround woofer... but they are 93db efficient. I'm using a pair of refurbed Dynaco Mark III amplifiers with them... an old Dynaco 70 just didn't seem to cut it with these speakers (I have a large listening area) and a 5W SE or Tri-path amp sounds terrible with any kind of music with big peaks.

For the future? Electrostats? or some type of OB speaker.

Cal Weldon 22nd June 2007 03:28 PM


As discussed in your other thread there different schools of thought on this.

It might help if you were to determine your loudness requirements before we can offer suggestions. For example, depending where I am and what I'm doing, I use anywhere from an inefficient dual 4.5" with 10 watts right up to a large PA system with oodles of watts and drivers.

Have you determined how many decibels you consider loud?

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