Which first watt amp is right for my 95dB speakers? - diyAudio
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Old 24th August 2015, 12:56 PM   #1
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Default Which first watt amp is right for my 95dB speakers?

First post here. Amazing community, making me get really excited about starting the build of my first FW amp!

My speakers are the DIY Troels Gravesen designed TQWT-mkIII speakers. They are a 95 dB high-efficiency "tapered quarter wave tube" speaker with a minimum impedance from 100 - 1000 Hz of 7 ohms and 5 ohms above 8 kHz, and described as being an overall an easy amplifier load.

Click the image to open in full size.

Click the image to open in full size.
(Red = impedance, blue = phase)

Click the image to open in full size.
(Red = impedance with higher resolution)

These speakers seem to be a great candidate for FW amps. I listen in a medium sized room and often at loud levels with modern bass-driven music so I would like something that controls the woofers really well.

According to Nelson's guidance from his CAS '15 talk, I would need around 30-40W of power:
POWER CALCULATION
1W = 95dB speaker/normal level/small room
x 10 for loud level
x 4 for big room
= 40 watt
This will be my first project so my preference would go for a simpler design. Based on what I have read I believe the F6 will work best, but I wanted to double check here before moving ahead with the project.

Any advice is much appreciated!

Further info:
TQWT mkII (previous generation mkII version on which measurements were taken)
TQWT mkIII (latest TQWT mkIII version, however this page describes mainly the DTQWT which is a larger variant with an additional bass driver, measurements here are of the DTQWT).
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Old 24th August 2015, 02:02 PM   #2
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Very nice speakers.
With those speakers, the world is your oyster, you can build any amp you desire.
F6 would be nice so would Aleph J, so would F3, so would F5 etc.
If this is your first amp build and want to build something quickly I'd probably go with F6.

Last edited by 2 picoDumbs; 24th August 2015 at 02:04 PM.
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Old 24th August 2015, 02:10 PM   #3
wdecho is offline wdecho  United States
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I'll second picoDumbs. Latest offering and less parts than some but with 95db speakers any Firstwatt should do fine. Tons of support right hear on the forum for your build.
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Old 24th August 2015, 02:10 PM   #4
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Have you actually measured the voltage peaks across your speaker?
I never exceed 4V and that is pretty loud. The only time I could possibly imagine needing more than that if a group of teenagers took me hostage and decided to have a 18th birthday party and wanted everyone in the street know what music they were listening too.

Last edited by 2 picoDumbs; 24th August 2015 at 02:15 PM.
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Old 24th August 2015, 02:30 PM   #5
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You should also consider the choke loaded L'amp. 13 watts of SE bliss. Just need to find two 2sk82 vFets. Hammond 193v choke works fine.

L’Amp: A Simple SIT Amp: Part Deux

I can't stop listening to the 5w CCS version with 94db FR Voigt pipes in a 20'x16' room.
The room opens to another room approx. the same size, so there's no shortage of volume/output. Works best with a preamp with some gain. Using the BA-3 pre at the moment with 15db of gain.

At any rate, Good luck!

Vince
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Old 25th August 2015, 01:17 AM   #6
6L6 is offline 6L6  United States
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I've wanted a pair of those speakers for some time! I would love to hear them, all reports is they are wonderful.

My suggestion? Aleph J or F6. BA-3. Not F5.
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Old 25th August 2015, 01:56 AM   #7
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If this is your first build don't overlook the ACA amp either. Comes in a kit with everything you need to finish it, including chassis and predrilled and tapped heatsink.
It also sounds very nice and will easily drive your speakers.
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Old 25th August 2015, 02:09 AM   #8
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What preamp do you (audioexploration) use?
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Old 25th August 2015, 02:47 AM   #9
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I don't think you will need 40Watts unless you're neighbours call the cops everytime you listen to music.
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Old 25th August 2015, 10:13 AM   #10
Zen Mod is online now Zen Mod  Serbia
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Quote:
Originally Posted by 6L6 View Post
....

My suggestion? Aleph J or F6. BA-3. Not F5.


yup
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