I use TruRTA for tuning, but mistrust the sensitivity readings because there seems to be a big difference in drive between sine and pink, and I can't check it with the DVM. Am I missing the boat somewhere?

Thanks,
John

with pink noise (equal power in each octave?) you've got a bunch of frequencies, not a single sine wave, so i can't begin to guess how the rms value relates there.

just a little rambling from what little i think i know ;-^

There may be an issue with how the meter derives the rms value. Some use "true rms" others use averaging which will not work for pink noise.

Regards Philip

What are you tuning? Something tasty that might make the Spring New England Valve (Bot) Do? I hope, I hope . . . .

I tried something like that before, at 60hz, and noticed that if I read 108db with sine, pink noise would be maybe 100 or less. I think I was seeing what you said I should see.

What I'm trying to do is be able to answer honestly when someone asks what the sensitivity of my speakers is. In the above case, would it be 108 or 100?

Thanks,

John

How 'bout you Dave - cookin' anything up to spring on us?

I've got two definites, a maybe and a wild card:
The easy definite is that I'm going to tweak one of my AN Kit 4 amps to see how far it will go. The other definite is that I'm building the AN Kit Preamp, and I'll try hard NOT to tweak the hell out of it so it remains a $729 full function pre w/phono, rather than double that with killer caps, resistors and wire.

The maybe is an iron-rich, scratch-built 2A3 stereo amp with AN chokes, OPTs and interstage xfrmrs. I have the schematic, contemplating parts choices and I will build it; I just don't know it will be done for the Spring meet.

The wild card is that I've been thinking of building a pair of speakers - everything from a Fostex back horn to Diatones to revisiting my TAD/JBL/TAD beasts using Bill Martinelli's 22" horn & 2" compression driver and eliminating the JBL mid. The whole thing is crazy since I'm up to my keister in speakers to begin with. Then again, the same is true of preamps and amps.

Timing will be interesting since I've committed to doing the Great Plains Audio Fest and I want to do the Bot Do, which will be within weeks of each other - late April - Early May-ish.

I've just got the build bug. I think I'm going to introduce my son, who turns 12 this week, to the joys of building stuff. I'll ask my daughter, too. She actually learned to solder in a science class in middle school last year. She's probably too busy being an angst-ridden yet aloof teen to be bothered with it, but I'll ask anyway.

What are you doing to set a reference for your microphone level? And are you measuring a meter away from the baffle, the dust cap, the horn mouth or diaphragm? Or are you going far away and then calculating back to get the W/M value?

Lately I've been measuring at 4 meters just because Karlsons don't converge up close, and I don't imagine a reflex does either, even when doing just one driver. I've had the most luck with ground plane, especially indoors, and I've learned to leave the unfixable room anomalies alone, rather than try to take them out with parametric EQ. All of my graphs show a high-Q suckout at 62hz and a broader hump at 160hz even after throwing rolls of insulation, pillows, futon, and a mattress around. Heck with it, it's there.

The best place for measuring in my house is the living/dining area that opens to an upper level, so there are the usual constraints on how long I can leave a rig set up.

You mentioned reasonably assuming the level is unchanged when going to pink noise from sine - I agree, but it's kind of a leap of faith that I'm not willing to take without corroboration, and is really what started this. TruRTA has a calibration routine, but I don't like the way it works - the graphs don't match my SPL meter.