[[email protected]]

geoff wrote:

===========

Actually I'm repairing a Bose 1800VI power amp that is reputed to be
quite good. But when you pull it apart it turns out to be Carvin.


** Yep, a PM1400 " magnetic field " job.

Tip from an expert:
Be very wary of any amplifier that has speaker maker's name on it.

Bose, JBL, AR, Renkus-Heinz, EV, Altec ......



...... Phil

[Don Pearce[_3_]]

On Sun, 21 Feb 2021 21:14:14 -0500, Neil
wrote:

On 2/21/2021 4:03 PM, Don Pearce wrote:
On Sun, 21 Feb 2021 14:35:29 -0500, Neil
wrote:

On 2/21/2021 9:29 AM, Don Pearce wrote:
On Sun, 21 Feb 2021 09:09:40 -0500, Neil
wrote:

The _acoustic damping_ makes the headphone shell surface non-reflective.
The side of one's head is both absorptive and not flat, so it is also
non-reflective. There are anomalies, but they are small in relation to
the headphone's non-linear response.

The side of the head is actually very reflective. And you are going to
have to explain this non-linear response. I've never seen it.

d

the non-linear response of headphones
https://www.rtings.com/headphones/tests/sound-quality/raw-frequency-response

Now, you explain your very reflective head.

Again, not a word about non-linearity. And the reflective head. You
are going to have to explain how it could not be - you are in the land
of ducks having no echo here.

d

Sorry that you didn't understand the curves in the tests, since they are
the definition of audio linearity.

I have no idea what you're talking about regarding duck echos.

Those curves are frequency response - also known as flatness.
Linearity is a quality of the transfer function - distortion to you.
Please try to use the right words.

d

--
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

[Don Pearce[_3_]]

On Sun, 21 Feb 2021 14:54:02 -0800 (PST), "
wrote:


I did not write what you are responding to, above.

** OK, Don Pearce did.

That is a trivial error while the post is correct and needed saying.


I did, and I should have caveated it by adding that it applies down to
the lower operational limiting frequency of the absorber. The idea of
anechoic is that nothing comes back. You can achieve that by either
having infinite space or perfect absorption.

d

--
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

[geoff]

On 22/02/2021 6:17 pm, wrote:
geoff wrote:

===========

Actually I'm repairing a Bose 1800VI power amp that is reputed to be
quite good. But when you pull it apart it turns out to be Carvin.


** Yep, a PM1400 " magnetic field " job.

Tip from an expert:
Be very wary of any amplifier that has speaker maker's name on it.

Bose, JBL, AR, Renkus-Heinz, EV, Altec ......



..... Phil




I was thinking about a different amp entirely, which was internally
Carvin - not Carver.

This says Bose on the PCBs - I wounder what the Carver one says. It is
a 'straightish' Class AB power amp with a touch where DC rails are
monitored and a triac momentarily switches in an extra section of mains
transformer primary if they dip. Nothing to do with Carver's sonic
holography magnetic field amp mumbo-jumbo, unless that's all it is ....

Had failed because the inside of the casing was essentially a solid
block of fluff and dust (pub).

geoff

[[email protected]]

geoff wrote:

=============

Actually I'm repairing a Bose 1800VI power amp that is reputed to be
quite good. But when you pull it apart it turns out to be Carvin.


** Yep, a PM1400 " magnetic field " job.

Tip from an expert:
Be very wary of any amplifier that has speaker maker's name on it.

Bose, JBL, AR, Renkus-Heinz, EV, Altec ......

I was thinking about a different amp entirely, which was internally
Carvin - not Carver.

This says Bose on the PCBs - I wounder what the Carver one says.


**Err - it says "CARVER"

https://audiokarma.org/forums/index....oes-on.776885/


It is
a 'straightish' Class AB power amp with a touch where DC rails are
monitored and a triac momentarily switches in an extra section of mains
transformer primary if they dip.

** Bit like the Carver then.



....... Phil

[geoff]

On 23/02/2021 10:23 am, wrote:
geoff wrote:

=============

Actually I'm repairing a Bose 1800VI power amp that is reputed to be
quite good. But when you pull it apart it turns out to be Carvin.


** Yep, a PM1400 " magnetic field " job.

Tip from an expert:
Be very wary of any amplifier that has speaker maker's name on it.

Bose, JBL, AR, Renkus-Heinz, EV, Altec ......

I was thinking about a different amp entirely, which was internally
Carvin - not Carver.

This says Bose on the PCBs - I wounder what the Carver one says.


**Err - it says "CARVER"

https://audiokarma.org/forums/index....oes-on.776885/


It is
a 'straightish' Class AB power amp with a touch where DC rails are
monitored and a triac momentarily switches in an extra section of mains
transformer primary if they dip.

** Bit like the Carver then.



...... Phil




You conveniently snipped the "Nothing to do with Carver's sonic
holography magnetic field amp mumbo-jumbo, unless that's all it is ...."
from my post, eh Phil.

Actually Class G or H apparently. And apparently the little mains kick
*is* all the 'magnetic field' mumbo-jumbo was about. No big deal at all.

And the 'sonic hologram' was something else entirely.

geoff

[[email protected]]

geoff wrote:
============



** Yep, a PM1400 " magnetic field " job.

Tip from an expert:
Be very wary of any amplifier that has speaker maker's name on it.

Bose, JBL, AR, Renkus-Heinz, EV, Altec ......

I was thinking about a different amp entirely, which was internally
Carvin - not Carver.

This says Bose on the PCBs - I wounder what the Carver one says.

**Err - it says "CARVER"

https://audiokarma.org/forums/index....oes-on.776885/


It is
a 'straightish' Class AB power amp with a touch where DC rails are
monitored and a triac momentarily switches in an extra section of mains
transformer primary if they dip.

** Bit like the Carver then.


You conveniently snipped the "Nothing to do with Carver's sonic
holography magnetic field amp mumbo-jumbo, unless that's all it is ...."
from my post, eh Phil.

** Yep - cos it had SFA to do with the topics or Carver amplifiers.


Actually Class G or H apparently. And apparently the little mains kick
*is* all the 'magnetic field' mumbo-jumbo was about.

** It was a lot more in Carver amps.

The transformer based PSU was voltage regulating with up to 8 DC rails.

And the 'sonic hologram' was something else entirely.


** A big, smelly red fish.


..... Phil

[Scott Dorsey]

Don Pearce wrote:
What do you use you blend it in so the sound is seamless? An equaliaer? The sub controls?

You start with the crossover, and then you consider equalization on top of
the crossover filters. The dbx DriveRack system is intended for PA
applications but can work okay in the studio too.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Scott Dorsey]

In article , Trevor wrote:

Actually the acoustic space within headphone earcups do cause problems
too. Even the space within your ear canal! And problems in rooms can be
reduced by acoustic treatment.

The interesting thing is that because the volume (AND the volume of your
ear canal) are much smaller than a room, the chamber resonances that were
bass problems get moved up and turn into upper midrange problems. The bass
becomes easy since the volume is too small to have resonance issues, but
other things get harder.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[[email protected]]

Scott Dorsey wrote:
===============

Actually the acoustic space within headphone earcups do cause problems
too. Even the space within your ear canal!

The interesting thing is that because the volume (AND the volume of your
ear canal) are much smaller than a room, the chamber resonances that were
bass problems get moved up and turn into upper midrange problems. The bass
becomes easy since the volume is too small to have resonance issues, but
other things get harder.

** There is no problem, other than how to sensibly measure the response of a headphone.
Using an imitation head with a tiny measurement mic buried inside the ear hole is ********.

The outer ear and ear canal does NOT create response anomalies for the * owner * of that ear.
The person's brain tunes them out so we hear sounds correctly.

FYI:

ES headphones are almost acoustically transparent, creating no trapped space for resonance to exist.
Other types having a weak air seal are not very different.



....... Phil

[Scott Dorsey]

wrote:
Scott Dorsey wrote:

Actually the acoustic space within headphone earcups do cause problems
too. Even the space within your ear canal!

The interesting thing is that because the volume (AND the volume of your
ear canal) are much smaller than a room, the chamber resonances that were
bass problems get moved up and turn into upper midrange problems. The bass
becomes easy since the volume is too small to have resonance issues, but
other things get harder.

** There is no problem, other than how to sensibly measure the response of a headphone.
Using an imitation head with a tiny measurement mic buried inside the ear hole is ********.

This is true, but there are standard methods to measure them. There are a
bunch of standard ear simulators which might not emulate my ear or your ear.
But if I see a plot made with a Zwislocki coupler or a Keller coupler, I know
I can compare it with other measurements made with the same coupler.

But... headphones are designed with those resonances in mind. And it's hard
for headphone designers to work around some of those resonances.. if it were
easy, there woudn't be so many different-sounding headphones out there.

The outer ear and ear canal does NOT create response anomalies for the * owner * of that ear.
The person's brain tunes them out so we hear sounds correctly.

Right. That's the problem. When you put on headphones, it's like putting
on someone else's ears and all of that brain training goes out the window.

For example, you're used to having a notch caused by reflections off your
shoulders. You use that to some extent to judge height of a sound source.
Where that notch is depends on your shoulder and neck geometry. So if you
try to emulate it in headphones to make the headphones sound more natural,
the place to put it is different for you and for me because our brains are
adapted for different bodies.

ES headphones are almost acoustically transparent, creating no trapped space for resonance to exist.
Other types having a weak air seal are not very different.

Yes, it's MUCH easier to do if you can go with an open-back design. This
leads to much more consistent measured response from person to person.
But it also kind of defeats much of the purpose of headphones.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[[email protected]]

Scott Dorsey wrote:
-----------------------------

** There is no problem, other than how to sensibly measure the response of a headphone.
Using an imitation head with a tiny measurement mic buried inside the ear hole is ********.

This is true, but there are standard methods to measure them.

** Shame they all make the same mistake.

But... headphones are designed with those resonances in mind.

** No they are not - cos it is not possible.

And it's hard
for headphone designers to work around some of those resonances..

** The word is "impossible".
There are no such design features.


if it were
easy, there woudn't be so many different-sounding headphones out there.

** They are way closer to each other than speakers.

The outer ear and ear canal does NOT create response anomalies for the * owner * of that ear.
The person's brain tunes them out so we hear sounds correctly.

Right. That's the problem. When you put on headphones, it's like putting
on someone else's ears and all of that brain training goes out the window.

** This is just plain nonsense, based on your previous nonsense.

Fraid you are using "wall to wall " thinking when every idea backs up the others in a crazy loop.

For example, you're used to having a notch caused by reflections off your
shoulders. You use that to some extent to judge height of a sound source.
Where that notch is depends on your shoulder and neck geometry. So if you
try to emulate it in headphones to make the headphones sound more natural,
the place to put it is different for you and for me because our brains are
adapted for different bodies.

** Shame that is worse nonsense.

ES headphones are almost acoustically transparent, creating no trapped space for resonance to exist.
Other types having a weak air seal are not very different.

Yes, it's MUCH easier to do if you can go with an open-back design.

** Most hi-fi head phones are open types.

But it also kind of defeats much of the purpose of headphones.

** It does not.



........... Phil