Speaker frequency response measurements

[Guest]

Archived from groups: rec.audio.tech (More info?)

Is there a standard input level(or output level) at which speaker
frequency response measurements are made?
I know that efficiency measurements are made with a standard 2.8 V input
but I have been unable to find a source which specifies a similar
standard for frequency response measurements.
Also,are there any common specs that allow one to get an idea of how
the frequency reponse changes with changing SPL for a given speaker, or
alternatively over how wide a range of SPL's the frequency response can
be expected to be stable?

George Deliz

 

[Guest]

Archived from groups: rec.audio.tech (More info?)

George,

> how the frequency reponse changes with changing SPL <

Theoretically, the frequency response of a loudspeaker will not change at
all with SPL. Whether it actually does in practice is a different matter,
but it's hard for me to see why it would change much if at all.

Far more difficult is to measure a speaker's frequency response in the first
place. As soon as you put any loudspeaker in any room, the room will totally
dominate the response. So you need to measure either in an anechoic chamber,
or you need to use special software like ETF that can apply a "gate" to stop
reading before any reflections get into the measuring microphone.

--Ethan

 

[Guest]

Archived from groups: rec.audio.tech (More info?)

George Deliz wrote:

> Is there a standard input level(or output level) at which speaker
> frequency response measurements are made?

AFAIK there are no generally agreed-upon comprehensive standards for
loudspeaker measurements. However there are some customary ways of doing
things.

For example, 2.82 volts is one common customary input that is used for
speaker testing. I believe it corresponds to 1 watt into an 8 ohm resistive
load.

Output levels are a bit more hard to nail down, because they are affected by
the frequency response of the speaker in the chosen test environment. For
this reason, it can be non-trivial to characterize the efficiency of a
speaker.

> I know that efficiency measurements are made with a standard 2.8 V
> input but I have been unable to find a source which specifies a
> similar standard for frequency response measurements.

One finds measurements made at 80, 90, and 100 dB at some chosen frequency
or range of frequencies.

> Also,are there any common specs that allow one to get an idea of how
> the frequency reponse changes with changing SPL for a given speaker,
> or alternatively over how wide a range of SPL's the frequency
> response can be expected to be stable?

Nonlinear distortion (THD, IM) gives some indication of how stable the
performance of a piece of equipment is as a function of level.

 

[Guest]

Archived from groups: rec.audio.tech (More info?)

"Ethan Winer" <ethanw at ethanwiner dot com> wrote in message news:<3dadnSKtBLKE_E3dRVn-hg@giganews.com>...
> George,
>
> > how the frequency reponse changes with changing SPL <
>
> Theoretically, the frequency response of a loudspeaker will not change at
> all with SPL. Whether it actually does in practice is a different matter,
> but it's hard for me to see why it would change much if at all.

Oh, please. This issue has been EXCEEDINGLY well documented and
and that documentation is readily available to anyone making a
modest effort to find it, Mr. Winer. Consider, for example:

Gander, M., "Dynamic Linearity and Power Compression in
Moving-Coil Loudspeakers," J. Audio Eng. Soc., vol 34,
no 9, 1986 Sept.

You don't have to wade far into this article, because by the third
page, he compares normalized frequency response curves of the same
speaker measured at 1 watt and 100 watt, which show significant
response differences exceeding, at some frequencies, 5 dB.

Consider, as well:

Henricksen, C. "Heat Transfer Mechanisms in Loudspeakers:
Analysis, Measurement and Design,"J. Audio Eng. Soc.,
vol 35, no 10, 1987 Oct.

Showing similar results.

And, in ANY reasonably comprehensive model of speakers accounting
for even first order non-linearities, theoretically, there are
PLENTY of reasons why the frequency response of a loudspeaker
WILL change with power level. Indeed, there is not even a
linear correspondance between input power and output SPL.

Here are just SOME of the reasons why this is true:

1. Since the DC resistance of the voice coils are temperature-
dependent, and the voice coil temperature is input-power
dependent, and since the bulk of the power dissipation in
speakers is in the DC resistance of the voice coil,
the bulk efficiency of the system changes.

2. And since the DC resistance of the voice coil is temperature-
dependent, and the voice coil temperature is input-power
dependent, and since the bulk of the power dissipation in
speakers is in the DC resistance of the voice coil, and since
over most of the range of a driver, the electrical impedance
is dominated by the DC resistance, the load presented to the
crossover changes and thus the crossover transfer function
changes and thus the frequency response of the system changes.

3. And, for all those same reasons, the effective damping of
the drivers at resonance, dominated by the DC resistance of
the voice coil, changes. And since the system response at the
low end is quite dependent upon damping, the response at the
low end changes as well.

4. The suspension compliance is a non-linear function of excursion,
excursion is a complex function of frequency and power, and thus
the suspension compleiance is a non-linear function of frequency
and power. And since the system response is determined, to some
extent, by suspension compliance, there is a dependence on power
and SPL due to suspension non-linearities.

5. The Bl factor is also a non-linear function of excursion, and
as mentioned, excursion is a complex function of frequency and
power, and since efficiency and damping are BOTH dependent upon
the Bl factor, the response of the speaker is dependent upon
power for that reason as well.

> Far more difficult is to measure a speaker's frequency response in the first
> place. As soon as you put any loudspeaker in any room, the room will totally
> dominate the response.

How is this at all relevant? The poster asked about the SPL
dependence of frequency response, which is NOT affected by the
room. Is it because to someone whose only tool is a hammer, all
problems look like nails?

 

[Guest]

Archived from groups: rec.audio.tech (More info?)

"Ethan Winer" <ethanw at ethanwiner dot com> wrote in message
news:3dadnSKtBLKE_E3dRVn-hg@giganews.com...
> George,
>
> > how the frequency reponse changes with changing SPL <
>
> Theoretically, the frequency response of a loudspeaker will not change at
> all with SPL. Whether it actually does in practice is a different matter,
> but it's hard for me to see why it would change much if at all.

Cheaper loudspeakers can become thermally overloaded at higher drive levels
and change frequency response as a result. This is a result of the voicecoil
heating up and becoming overall more resistive. Ussually this is not
blatently noticable. The compression effect that comes with thermal
overloading of the voicecoil is ussually more noticable. Modern, and more
importantly, properly designed loudspeakers should not develop this problem.

Mechanically speakers will also change in FR if you far exceed their linear
excursion but the screaming THD and compression will do more to sound
poorly.

Remember the greatest amount of audible frequency response change with
increasing SPL is your own ears following the Fletcher-Munsen curve.
Cranking up the volume real high destroys high frequency hearing and
compensates for it at the same time.

>
> Far more difficult is to measure a speaker's frequency response in the
first
> place. As soon as you put any loudspeaker in any room, the room will
totally
> dominate the response. So you need to measure either in an anechoic
chamber,
> or you need to use special software like ETF that can apply a "gate" to
stop
> reading before any reflections get into the measuring microphone.
>
> --Ethan
>
>

 

[Guest]

Archived from groups: rec.audio.tech (More info?)

Dick Pierce wrote:

> "Ethan Winer" <ethanw at ethanwiner dot com> wrote in message news:<3dadnSKtBLKE_E3dRVn-hg@giganews.com>...
> > George,
> >
> > > how the frequency reponse changes with changing SPL <
> >
> > Theoretically, the frequency response of a loudspeaker will not change at
> > all with SPL. Whether it actually does in practice is a different matter,
> > but it's hard for me to see why it would change much if at all.
>
> Oh, please. This issue has been EXCEEDINGLY well documented and
> and that documentation is readily available to anyone making a
> modest effort to find it, Mr. Winer. Consider, for example:
>
> Gander, M., "Dynamic Linearity and Power Compression in
> Moving-Coil Loudspeakers," J. Audio Eng. Soc., vol 34,
> no 9, 1986 Sept.
>
> You don't have to wade far into this article, because by the third
> page, he compares normalized frequency response curves of the same
> speaker measured at 1 watt and 100 watt, which show significant
> response differences exceeding, at some frequencies, 5 dB.
>
> Consider, as well:
>
> Henricksen, C. "Heat Transfer Mechanisms in Loudspeakers:
> Analysis, Measurement and Design,"J. Audio Eng. Soc.,
> vol 35, no 10, 1987 Oct.
>
> Showing similar results.
>
> And, in ANY reasonably comprehensive model of speakers accounting
> for even first order non-linearities, theoretically, there are
> PLENTY of reasons why the frequency response of a loudspeaker
> WILL change with power level. Indeed, there is not even a
> linear correspondance between input power and output SPL.
>
> Here are just SOME of the reasons why this is true:
>
> 1. Since the DC resistance of the voice coils are temperature-
> dependent, and the voice coil temperature is input-power
> dependent, and since the bulk of the power dissipation in
> speakers is in the DC resistance of the voice coil,
> the bulk efficiency of the system changes.
>
> 2. And since the DC resistance of the voice coil is temperature-
> dependent, and the voice coil temperature is input-power
> dependent, and since the bulk of the power dissipation in
> speakers is in the DC resistance of the voice coil, and since
> over most of the range of a driver, the electrical impedance
> is dominated by the DC resistance, the load presented to the
> crossover changes and thus the crossover transfer function
> changes and thus the frequency response of the system changes.
>
> 3. And, for all those same reasons, the effective damping of
> the drivers at resonance, dominated by the DC resistance of
> the voice coil, changes. And since the system response at the
> low end is quite dependent upon damping, the response at the
> low end changes as well.
>
> 4. The suspension compliance is a non-linear function of excursion,
> excursion is a complex function of frequency and power, and thus
> the suspension compleiance is a non-linear function of frequency
> and power. And since the system response is determined, to some
> extent, by suspension compliance, there is a dependence on power
> and SPL due to suspension non-linearities.
>
> 5. The Bl factor is also a non-linear function of excursion, and
> as mentioned, excursion is a complex function of frequency and
> power, and since efficiency and damping are BOTH dependent upon
> the Bl factor, the response of the speaker is dependent upon
> power for that reason as well.
>
> > Far more difficult is to measure a speaker's frequency response in the first
> > place. As soon as you put any loudspeaker in any room, the room will totally
> > dominate the response.
>
> How is this at all relevant? The poster asked about the SPL
> dependence of frequency response, which is NOT affected by the
> room. Is it because to someone whose only tool is a hammer, all
> problems look like nails?

Thanks for the references and discussion. I had searched google for about an hour and found nothing very
helpful.

George Deliz

 

[Guest]

Archived from groups: rec.audio.tech (More info?)

Arny Krueger wrote:

> George Deliz wrote:
>
> > Is there a standard input level(or output level) at which speaker
> > frequency response measurements are made?
>
> AFAIK there are no generally agreed-upon comprehensive standards for
> loudspeaker measurements. However there are some customary ways of doing
> things.
>
> For example, 2.82 volts is one common customary input that is used for
> speaker testing. I believe it corresponds to 1 watt into an 8 ohm resistive
> load.
>
> Output levels are a bit more hard to nail down, because they are affected by
> the frequency response of the speaker in the chosen test environment. For
> this reason, it can be non-trivial to characterize the efficiency of a
> speaker.
>
> > I know that efficiency measurements are made with a standard 2.8 V
> > input but I have been unable to find a source which specifies a
> > similar standard for frequency response measurements.
>
> One finds measurements made at 80, 90, and 100 dB at some chosen frequency
> or range of frequencies.
>
> > Also,are there any common specs that allow one to get an idea of how
> > the frequency reponse changes with changing SPL for a given speaker,
> > or alternatively over how wide a range of SPL's the frequency
> > response can be expected to be stable?
>
> Nonlinear distortion (THD, IM) gives some indication of how stable the
> performance of a piece of equipment is as a function of level.

Arny Krueger wrote:

> George Deliz wrote:
>
> > Is there a standard input level(or output level) at which speaker
> > frequency response measurements are made?
>
> AFAIK there are no generally agreed-upon comprehensive standards for
> loudspeaker measurements. However there are some customary ways of doing
> things.
>
> For example, 2.82 volts is one common customary input that is used for
> speaker testing. I believe it corresponds to 1 watt into an 8 ohm resistive
> load.
>
> Output levels are a bit more hard to nail down, because they are affected by
> the frequency response of the speaker in the chosen test environment. For
> this reason, it can be non-trivial to characterize the efficiency of a
> speaker.
>
> > I know that efficiency measurements are made with a standard 2.8 V
> > input but I have been unable to find a source which specifies a
> > similar standard for frequency response measurements.
>
> One finds measurements made at 80, 90, and 100 dB at some chosen frequency
> or range of frequencies.
>
> > Also,are there any common specs that allow one to get an idea of how
> > the frequency reponse changes with changing SPL for a given speaker,
> > or alternatively over how wide a range of SPL's the frequency
> > response can be expected to be stable?
>
> Nonlinear distortion (THD, IM) gives some indication of how stable the
>

Thanks to all respondents. I had searched google for nearly an hour without
finding anything nearly as helpful.
George Deliz

 

[Guest]

Archived from groups: rec.audio.tech (More info?)

Arny Krueger wrote:

> George Deliz wrote:
>
> > Is there a standard input level(or output level) at which speaker
> > frequency response measurements are made?
>
> AFAIK there are no generally agreed-upon comprehensive standards for
> loudspeaker measurements. However there are some customary ways of doing
> things.
>
> For example, 2.82 volts is one common customary input that is used for
> speaker testing. I believe it corresponds to 1 watt into an 8 ohm resistive
> load.
>
> Output levels are a bit more hard to nail down, because they are affected by
> the frequency response of the speaker in the chosen test environment. For
> this reason, it can be non-trivial to characterize the efficiency of a
> speaker.
>
> > I know that efficiency measurements are made with a standard 2.8 V
> > input but I have been unable to find a source which specifies a
> > similar standard for frequency response measurements.
>
> One finds measurements made at 80, 90, and 100 dB at some chosen frequency
> or range of frequencies.
>
> > Also,are there any common specs that allow one to get an idea of how
> > the frequency reponse changes with changing SPL for a given speaker,
> > or alternatively over how wide a range of SPL's the frequency
> > response can be expected to be stable?
>
> Nonlinear distortion (THD, IM) gives some indication of how stable the
> performance of a piece of equipment is as a function of level.

Arny Krueger wrote:

> George Deliz wrote:
>
> > Is there a standard input level(or output level) at which speaker
> > frequency response measurements are made?
>
> AFAIK there are no generally agreed-upon comprehensive standards for
> loudspeaker measurements. However there are some customary ways of doing
> things.
>
> For example, 2.82 volts is one common customary input that is used for
> speaker testing. I believe it corresponds to 1 watt into an 8 ohm resistive
> load.
>
> Output levels are a bit more hard to nail down, because they are affected by
> the frequency response of the speaker in the chosen test environment. For
> this reason, it can be non-trivial to characterize the efficiency of a
> speaker.
>
> > I know that efficiency measurements are made with a standard 2.8 V
> > input but I have been unable to find a source which specifies a
> > similar standard for frequency response measurements.
>
> One finds measurements made at 80, 90, and 100 dB at some chosen frequency
> or range of frequencies.
>
> > Also,are there any common specs that allow one to get an idea of how
> > the frequency reponse changes with changing SPL for a given speaker,
> > or alternatively over how wide a range of SPL's the frequency
> > response can be expected to be stable?
>
> Nonlinear distortion (THD, IM) gives some indication of how stable the
>

Thanks to all respondents. I had searched google for nearly an hour without
finding anything nearly as helpful.
George Deliz

 

[Guest]

Archived from groups: rec.audio.tech (More info?)

George Deliz wrote:

> Arny Krueger wrote:
>
> > George Deliz wrote:
> >
> > > Is there a standard input level(or output level) at which speaker
> > > frequency response measurements are made?
> >
> > AFAIK there are no generally agreed-upon comprehensive standards for
> > loudspeaker measurements. However there are some customary ways of doing
> > things.
> >
> > For example, 2.82 volts is one common customary input that is used for
> > speaker testing. I believe it corresponds to 1 watt into an 8 ohm resistive
> > load.
> >
> > Output levels are a bit more hard to nail down, because they are affected by
> > the frequency response of the speaker in the chosen test environment. For
> > this reason, it can be non-trivial to characterize the efficiency of a
> > speaker.
> >
> > > I know that efficiency measurements are made with a standard 2.8 V
> > > input but I have been unable to find a source which specifies a
> > > similar standard for frequency response measurements.
> >
> > One finds measurements made at 80, 90, and 100 dB at some chosen frequency
> > or range of frequencies.
> >
> > > Also,are there any common specs that allow one to get an idea of how
> > > the frequency reponse changes with changing SPL for a given speaker,
> > > or alternatively over how wide a range of SPL's the frequency
> > > response can be expected to be stable?
> >
> > Nonlinear distortion (THD, IM) gives some indication of how stable the
> > performance of a piece of equipment is as a function of level.
>
> Arny Krueger wrote:
>
> > George Deliz wrote:
> >
> > > Is there a standard input level(or output level) at which speaker
> > > frequency response measurements are made?
> >
> > AFAIK there are no generally agreed-upon comprehensive standards for
> > loudspeaker measurements. However there are some customary ways of doing
> > things.
> >
> > For example, 2.82 volts is one common customary input that is used for
> > speaker testing. I believe it corresponds to 1 watt into an 8 ohm resistive
> > load.
> >
> > Output levels are a bit more hard to nail down, because they are affected by
> > the frequency response of the speaker in the chosen test environment. For
> > this reason, it can be non-trivial to characterize the efficiency of a
> > speaker.
> >
> > > I know that efficiency measurements are made with a standard 2.8 V
> > > input but I have been unable to find a source which specifies a
> > > similar standard for frequency response measurements.
> >
> > One finds measurements made at 80, 90, and 100 dB at some chosen frequency
> > or range of frequencies.
> >
> > > Also,are there any common specs that allow one to get an idea of how
> > > the frequency reponse changes with changing SPL for a given speaker,
> > > or alternatively over how wide a range of SPL's the frequency
> > > response can be expected to be stable?
> >
> > Nonlinear distortion (THD, IM) gives some indication of how stable the
> >
>
> Thanks to all respondents. I had searched google for nearly an hour without
> finding anything nearly as helpful.
> George Deliz

Apparently my newsreader was lying when it said it could not find the mail server.

George Deliz

 

[Guest]

Archived from groups: rec.audio.tech (More info?)

Wessel,

> Cheaper loudspeakers can become thermally overloaded at higher drive
levels and change frequency response as a result. <

Thanks, that all makes sense.

--Ethan

 

[Guest]

Archived from groups: rec.audio.tech (More info?)

Dick,

> Here are just SOME of the reasons why this is true: <

All of that was truly fabulous. Thanks for the detailed explanation. This is
what you do best.

> Is it because to someone whose only tool is a hammer, all problems look
like nails? <

I see you still need to work on common courtesy. :-(

Look, people of all levels come to newsgroups asking for help. Some have no
clue how audio works and ask pie in the sky questions, and others have
questions that are extremely sophisticated. It's often difficult to know
someone's level from their questions. So I contribute what I can - be aware
of the room when measuring a speaker's response - and folks like you
contribute based on their own personal slant and expertise. So lighten up a
bit and we'll all help as we can.

--Ethan