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pforeman 9th August 2009 11:13 PM

Full Range Open Baffle and 5W triode
Six months ago I built a set of Open baffle 10" audio nirvana full range speakers with a 15" H frame speaker powered with a parts express 250 watt plate amp.
My intention was to then build a 5-7 watt single ended triode amp to power the speakers. I settled on design by Tubelab.
Since the beginning I was very worried that it wouldn't play loud enough (amongst other worries-building it all).
I have it all together. without ultra-linear or cathode feedback, with el34's I am getting 104 dB peaks, with little or no distortion (could have gone louder- but I'm too chicken as of yet, it is the first time on for this amp.
I would also like to say that I have the plate amp up about half way on the gain, and am only using one 15" speaker in the H frame. I am quite pleased with the combination.
Listening room 24' X 13' X 8'.
dB measured at the chair 7.5 feet from speaker.
Audio nirvana high frequency tamed with a coil/resistor-Thanks to Mr. Pass
And thanks to everyone else with either your ideas or your responses to my questions.

human.bin 10th August 2009 07:23 AM


khundude 10th August 2009 09:04 PM

Any details of the coil and resistor because I plan on using the 10" or the 12"?

pforeman 11th August 2009 02:56 AM

In this forum, Nelson Pass answered my question. He has a program, and kind of offered me a student version (no charge) Regular version was many thousands of dollars!!
I didn't take him up on that! But he did recommend a coil and resistor in parallel both of which are in series with the speaker.
Coil 5 mH
Resistor 8 ohms
I used a wirewound resistor 5 watt, and a solen perfect lay 22 guage
(as it won't be seeing much or any bass, I thought the larger guage was a waste)

pforeman 11th August 2009 03:36 AM

2 Attachment(s)
sides and top of h frame are solid maple. "Baffle" is 3/4 maple plywood
FR baffle is 1/2 in plexiglass mounted on a strip of maple with a dado cut at about 10 degrees (so that it leans back and doesn't fall).
Sorry only one pic as it took me forever to resize it so I could post it

human.bin 11th August 2009 02:41 PM

nice works :) how did you mounted the drivers onto the plexiglass?

pforeman 12th August 2009 01:18 AM

bolts, with a gasket of silicone "caulk"

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