audio-talk

Since upgrading the baffles I have noticed a touch of hardness and or distortion on some female vocals. I first noticed it on one of Siri's tracks but it has now been noticed on others.

Most of my female vocal is played through the SB Touch, and it does not seem to be DAC dependent. I only notice this problem after the system has been playing a while, so it may be heat orientated ?

I must try the KT66 (as a triode) monoblocks in place of the GK-71 to see if it is amp related, and if not perhaps try the Pre 3 again instead of my Audionote copy pre-amp.

Perhaps the problem has been there for a while and now the more revealing speakers are showing it up ?

Once you notice this, it can only get more irritating.
Only thing I can suggest, is that since the problem appeared when you changed the main driver on the baffles, then it is either the driver itself, or its position on the baffle that is causing it.
One easy thing to try would be to make a new top sheet of wood, with the driver in the centre, then compare the two configurations.

I have been through this syndrome phil, amd still are going throuh it to a small degree

Is is the new speaker revealing some thing that the electronics is creating, or just the speakers ?

Some Paper cone speakers take a lot of running in to be totally clean, those aplairs have the recommended running in period in lowther territory... So as steve said its more likely the speakers,
offset speakers in baffles where always regarded as the correct way for an open baffle, the first couple of baffles i built where the offset, but there was not any distortion that i was aware of, never the less steve could have a point, you could clamp a piece of wood to the existing baffle to give the speaker a even load

Lesser valves tend to taketh away finer parts of the music, not usually cause distortion (providing they are ok of course)
Best of luck...

Thank you Steve & Steve,more to think about.

I've been wanting to try the Pre3 and KT66 amps anyway, so it will be an interesting thing to do, and help identify the "problem".

I had considered the speakers might be the "problem", the offset is a tad drastic, but they were run in before I got them.

I'll let you all know how things go.

Another possibility to think about, is an impedance correction network, I have to use them on my Audax units because the voice coil reactance is so high, if I don't I literally get earache!

Unfortunately the component values need to be worked out mathmatically, and needs the voice coil inductance value. The network is CRL (capacitor, resistor, inductor) in series, and the whole is wired in parallel with the voice coil. There is or was a calculator on the net somewhere...

If your amp doesn't have NFB, the peaky affect of voice coil reactance is not suppressed because the amp has very low electrical speaker damping. The result is that output increases with rising frequency, as the reactance increases.

If you got or can get hold of a soild state amp, having high open-loop gain and NFB (and hence high damping) you could try them with the speakers, which may prove whether that's what's going on.

HTH

Thanks Mike.

I've still got an old QED A240CD sand amp (40W from memory), so might try that as well.

Worth a go, to see what difference if any.

Mike H wrote:
If your amp doesn't have NFB, the peaky affect of voice coil reactance is not suppressed because the amp has very low electrical speaker damping. The result is that output increases with rising frequency, as the reactance increases.


HTH

Thats a fair point mike. My understanding is that low damping factor amps work better with speakers that are completely or close to being self damped, in this case i would hazard a guess these alpairs are not completely self damped... Just based on the efficiency ?
As such should they be treated as more of a normal speaker with regard to its needs.. rather than how we consider a full range unit ?
Never the less a peakyness assuming its not excessive should not create a harshness or the likes, It will be interestiing to know the true cause once phil gets there...

Been busy today but should have time tomorrow (Wednesday).

Not urgent is it?

Mike H wrote:Not urgent is it?

Not at all, but I'd like to get to the bottom of it.

When I purchased the Audionote copy pre amp from Philip Ramsey some years ago he did tell me he was not 100% happy with the SQ, but the price reflected that.

I've never had any problems until now, so as a first step I put the World Designs Pre3 back in the system.

So far the hardness/distortion has not occurred.

The Pre3 had a problem on one channel when last used, but so far all is well.

pre65 wrote:

Mike H wrote:Not urgent is it?

Not at all, but I'd like to get to the bottom of it.

Know what ya mean.

I had a word with Nick, and he suggested trying a new pair of valves.

I had several new 6463 and managed to find a used ECC82 that had previously lived in the Pre3 (or Phono3).

Fitting them and trying it on the same tunes as before seems to have eliminated the hardness/distortion. Thanks Nick.

The rectifier that came with the pre was a 5Z4G, but it flashed over on start up. I tried an old Mullard GZ32 out of one of my Quad 11 and that has never flashed. Just tried a Russian version of GZ32 and that flashes as well.

Seems the Mullards must be made better ?