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Old 5th May 2011, 10:40 AM   #1
Jens A. is offline Jens A.  Denmark
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Default NAKSA 100 output inductors necessary for sub-250 Hz use?

Hi Hugh,

Would it be possible to omit the output inductors for the N100 when used below 250 Hz (which is what I will do)?

IMHO an inductor in series with the speaker affects dampening factor. Now, the effect of dampening factor is debatable, but still?

Cheers,

Jens
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Old 5th May 2011, 11:35 AM   #2
AKSA is offline AKSA  Australia
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Hi Jens,

No, I would NEVER delete them. They are a necessary part of the stability matrix for any PP AB SS amp, and deleting them because the amp is passing only low frequencies does not preclude instability under certain high signal conditions.

HOWEVER, at low frequencies, and indeed at audio frequencies, I would defy anyone to hear a difference. They measure just 1.4uH, which is well below the 2uH thought to be of influence at frequencies beyond about 15KHz.

You mention damping factor, which is interesting. There is absolutely no point in going beyond about 100 for domestic high end. IN truth, I've found that too high a damping factor tends to reduce reverberation, leading to a very dry, uninvolving bass without the subtle loose effect that can really be very satisfying to listen to. I try for a damping factor in the 50-200 range, no higher.

Hope this helps!

Hugh
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Old 5th May 2011, 03:05 PM   #3
Jens A. is offline Jens A.  Denmark
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Originally Posted by AKSA View Post
Hi Jens,

No, I would NEVER delete them. They are a necessary part of the stability matrix for any PP AB SS amp, and deleting them because the amp is passing only low frequencies does not preclude instability under certain high signal conditions.

HOWEVER, at low frequencies, and indeed at audio frequencies, I would defy anyone to hear a difference. They measure just 1.4uH, which is well below the 2uH thought to be of influence at frequencies beyond about 15KHz.

You mention damping factor, which is interesting. There is absolutely no point in going beyond about 100 for domestic high end. IN truth, I've found that too high a damping factor tends to reduce reverberation, leading to a very dry, uninvolving bass without the subtle loose effect that can really be very satisfying to listen to. I try for a damping factor in the 50-200 range, no higher.

Hope this helps!

Hugh
Hi Hugh,

I am not quite sure I agree about the reverberation part. What you are saying is actually that the speaker should get a bit out of control. I don't believe this should happen ...

When measuring dampening factor, is that done with or without the inductor for your amps?

Cheers,

Jens
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Old 5th May 2011, 11:38 PM   #4
AKSA is offline AKSA  Australia
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Jens,

I won't get into debates here!! What I say is based entirely on empirical experience, and yours may well differ.... the old YMMV adage applies, of course.

PMA in the SS section recently did analysis on this very issue, which I suspect you've read. He measured 0.02dB increase in level at 20KHz with a simulated speaker load, using simulation certainly, but I think he corroborated his results empirically as well. I measure DF with the inductor in place, however.

This is NOT audible, Jens, and as some wag responded, it is not worth possible stability issues by omitting this component. As you can see, I'm deeply conservative in my design approach; this is because most courageous experiments end in tears, and I'm not happy about the risk of blowing up other people's speakers!!

Ciao,

Hugh
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Old 6th May 2011, 01:13 AM   #5
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I hate crossovers, they do all sorts of horrible phase shifting.

I run a 600 watt Eminence sigma pro without any crossover with a anotehr pair of full range 12 inch speakers. Sounds great.

I run a disco so dont want any cancelling of sound due to phase shifts.
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Old 6th May 2011, 12:46 PM   #6
Jens A. is offline Jens A.  Denmark
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Originally Posted by AKSA View Post
Jens,

I won't get into debates here!! What I say is based entirely on empirical experience, and yours may well differ.... the old YMMV adage applies, of course.

PMA in the SS section recently did analysis on this very issue, which I suspect you've read. He measured 0.02dB increase in level at 20KHz with a simulated speaker load, using simulation certainly, but I think he corroborated his results empirically as well. I measure DF with the inductor in place, however.

This is NOT audible, Jens, and as some wag responded, it is not worth possible stability issues by omitting this component. As you can see, I'm deeply conservative in my design approach; this is because most courageous experiments end in tears, and I'm not happy about the risk of blowing up other people's speakers!!

Ciao,

Hugh
What! No debates? I thought that was what this forum was for!

However, I absolutely agree about the stability issues, and I believe the inductor is by and large inaudible. In fact, it may even make the amp sound better - exactly because it is more stable ....

One thing, though. Over the years I have tested many different types of inductors and can vouch for the fact that they do not sound the same at all. From listening tests, my preference is very tightly rolled foil inductors, as these have a much more open sound than traditional inductors. They also have considerably less resistance, although I do not think the latter is an issue in this connection.

So, I might try foil inductors instead of the standard inductors you supply with the N70 and N100 kits. What are the exact values of the inductors used?

Cheers,

Jens
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Old 7th May 2011, 08:03 AM   #7
AKSA is offline AKSA  Australia
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Default Output Inductors

Hi Jens,

No problem, I do like a debate, as long as it's civil, unlike many other forums where differences of opinion all too often turn into slanging matches!

Foil is fine.....

You should wind for a value of 1.4uH, nice and small, well below the unwritten 2uH 'limit'.

You may hear a difference, but that may depend on how much work you have to put into the inductor!!

Cheers,

Hugh
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Old 10th May 2011, 12:26 PM   #8
Jens A. is offline Jens A.  Denmark
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Originally Posted by AKSA View Post
Hi Jens,

No problem, I do like a debate, as long as it's civil, unlike many other forums where differences of opinion all too often turn into slanging matches!

Foil is fine.....

You should wind for a value of 1.4uH, nice and small, well below the unwritten 2uH 'limit'.

You may hear a difference, but that may depend on how much work you have to put into the inductor!!

Cheers,

Hugh
Hi Hugh,

Hmmm - standard values for the foil inductors are 1.2 uH and 1.5 mH. If need be, could I go as low as 1.2 mH?

I have quite a few foil inductors lying around from speaker development projects, so I may even have a couple of 1.4 uHs ...

If and when I get the time to try this out, I will post my findings here

Cheers,

Jens
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Old 12th May 2011, 05:54 AM   #9
rabbitz is offline rabbitz  Australia
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Remember we are talking about uH and not mH as normally used on crossovers.

1.4uH is 0.0014mH which is not standard in foils as far as I know.

Best to wind your own. Look at item 26 on this page for some winding details.
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Old 12th May 2011, 10:58 AM   #10
Jens A. is offline Jens A.  Denmark
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Remember we are talking about uH and not mH as normally used on crossovers.

1.4uH is 0.0014mH which is not standard in foils as far as I know.

Best to wind your own. Look at item 26 on this page for some winding details.
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Thanks, Rabbitz!

I entirely overlooked that. No, not standard on foils, but I can order the correct size

Cheers,

Jens
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