Sonic Quality of L-pad attenuator for tweeter

[Aucosticraft]

I just want to conform from other members here that does Lpad attenuator affect sonic quality of tweeter. I tried a tweeter with 6db Lpad attenuator another without attenuator. but reduced the same db at amplifier to match the output at tweeters. what I felt was the tweeter without Lpad, Sound better crisp and clearer, and sound more natural.
Just want to know from you all here is , what difference I heard, makes sense or just my illusion. Also is some body can explain how series resister in attenuator makes the difference. resister in series of any driver affects the damping of driver. so how this affects tweeter?

Regds

 

[Helmuth]

It is difficult to judge that way.

You shout compare the one with l-pad to the one with out at the same loudness level.

And then in a blind test say if you really can hear the difference.

My self I do think I hear difference between wire wound resistors and metal film.
To me the wire wound sound brighter but it tents to more aggressive.

So I compared wire wound to metal film and carbon resistors.

 

[LineArray]

Hello,

if you have a passive crossover (high pass filter) for
the tweeter, the L-Pad's effect on the tweeter's
impedance in the resonance region may change the
rolloff behaviour of the high pass because the
tweeter's impedance peak at resonance is mitigated.

Typically the tweeter can have somewhat lower
relative level now around its resonant frequency
if the L-Pad was designed to maintain the tweeters DC
resistance.

Depending on the tweeter and dimensioning of your
L-Pad the slope of the crossover will be closer to theory
- resistive load - now since the padded tweeter is closer
to a resisitive load.

The damping (electro motoric force) for the tweeter at
its resonance might even be higher than without L-Pad,
depending on your high pass filter...

So it may sound different now, but that need not be a
degradation. Maybe the filter should be corrected ...

I do not believe in sonic degradation caused by an L-Pad
if L-Pad and filter are dimensioned properly.

Many in here believe resistors being "sonic poison"
in itself, i do instead believe resistors being the most
harmless components in a passive crossover, as long
as effects on level, damping and the like are accounted
for ...

If you have the possibility of circuit simulation and
your filter is 2nd order, you can try

1)
---ccc----rrr---twt---|
..........|......|--rrr---|
..........|--------llll---|

2)
---ccc----rrr---twt--|
..................|--rrr--|
..................|--llll--|

with
ccc: capacitor
rrr: resistor
llll: inductor
twt: tweeter

option 2) which may provide somewhat more
damping (emf) for the tweeter in the rolloff region
of the filter.


Kind Regards

 

[Helmuth]

The series resistance will also change the TS-parameter of the tweeter maybe this makes the difference.

Also the damping factor of your amplifier reduces due the series resistance.

 

[LineArray]

Yes, option 2) may bring a little damping back,
since the coil can better contribute as a shortcut
across the tweeter's terminals in the lower rolloff
region.

Next option is full impedance compensation of the
tweeter's resonance before applying the L-Pad.

 

[Aucosticraft]

Thank you all for the prompt reply.
I was out of town as my uncle died. Sorry for the delay.

It is difficult to judge that way.

You shout compare the one with l-pad to the one with out at the same loudness level.

And then in a blind test say if you really can hear the difference.

I did so, I guess u missed those lines in my post.

LineArray:

I never thought of what you explained. I mean in this case. Sure L-pad makes crossover resistive load. but in that case, can we say Crossover would perform better?

I never tried but just thinking. what if L-pad is added before crossover and tweeter? any Idea?

I do not believe in sonic degradation caused by an L-Pad
if L-Pad and filter are dimensioned properly.

Many in here believe resistors being "sonic poison"
in itself, I do instead believe resistors being the most
harmless components in a passive crossover, as long
as effects on level, damping and the like are accounted
for ...

I too believe resister in itself is harmless, but I am trying to relate with the theory "why resistor should not be added to driver" . this would change other characteristics of driver.which is also said by Helmuth

"The series resistance will also change the TS-parameter of the tweeter maybe this makes the difference.

Also the damping factor of your amplifier reduces due the series resistance."

 

[Pano]

The L-Pad usually goes after the crossover as it means a flatter impedance curve and damped resonance (as noted above). This is often quite desirable.

But in your case it may not be. Try it the other way around - it may work better with your tweeter and crossover.

 

[LineArray]

...
"The series resistance will also change the TS-parameter of the tweeter maybe this makes the difference.

Also the damping factor of your amplifier reduces due the series resistance."

That is true, but frequency dependent damping factor is
also affected by the series capacitor, which has a much
higher impedance than the tweeters Rg in the crossovers
rolloff range and the crossover frequency is typically fairly
above the resonance of the tweeter.

Every circuit has to be investigated individually,
concerning the resulting Qes ... it depends on the
tweeter's properties and the whole crossover
circuit.

But it is impossible to make the tweeter "see" the
amplifier in the rolloff region of the crossover, there
will always be a high impedance in series,
with resistive component or not.

The question - besides going active - may be:

Where do we get damping ?

One option is to make Qm lower and apply mechanical
damping (e.g. by a large rear chamber and a flow
resistance behind the membrane) to the tweeter to get
the desired effective Qts.

Another option is to provide some low electrical
impedance in parallel to the tweeter especially in
the rolloff region of the crossover, which provides
some damping by back EMF. For purposes of
back EMF solely it is not important, whether the
current induced by the tweeter's moving voice coil
flows through the amplifier
("which is ideally a wire with amplification")
or through a (low) impedance parallel to the tweeter.

But you won't get that impedance very low - just
as low as possible.

If one does not want to compensate the resonant
impedance peak of the tweeter using an LCR in
parallel to the VC terminals, also a resistor
in parallel can be used to make the load more
resisitive and damping more frequency independent.

You can use that even without series resistor, which
means without padding the tweeter down ...

That will cost some efficiency ( not voltage sensitivity)
but the crossover slope will be closer to the "resistive load"
case. Especially with a tweeter of relatively high impedance
this may be an option.


Kind Regards

 

[Aucosticraft]

Guys I am experimenting..... Working on it... Will update you. Thanks for being with me...

 

[tiefbassuebertr]

The usual part therefore in 8 ohms looks like this one under
MONACOR: AT-62H.
Disadvantage is, that this attenuator consists of turns of a special resistor wire - consequence is a lot of crackling and distortion after short using - initially only while turning.
I think this is due temporary overheating during dynamic effects - go to the attached files.

Are there versions on the marked with special kind of resistor wire without this disadvantage ?

I know the best are Caddock resistors - go to
http://www.caddock.com/Online_catalog/Mrktg_Lit/MP9000_Series.pdf
and coding plugs/bridges - go to
Connecting plug KS2-...3
but nevertheless I want to know a solution for stepless attenuation.

Maybe this parts are an alternative:
https://www.fostexinternational.com/docs/speaker_components/pdf/att.pdf