Increasing attenuation on passive network

[kelossus]

I'd like to increase the attenuation on the HF section of my current speakers. These speakers have a rotary switch on the back with 3 separate positions, -1db , flat and +1db. A rather useless amount of attentuation. I would like to increase attenuation to at least -3db and -6db. Does anyone with passive crossover knowledge know which parts I need to change and to roughly what values?

 

 

 

 

 

[rockeater]

R3, R3a and R3b in unison with C9, C9a and C10 do the trick, but you should not play with them.

 

The amount of attenuation is 1.2dB and not 1dB and it is not useless.

3dB will cut your treble in half and 6dB would reduce it by another half of that, so you would end up with a quarter of original treble.

Do you really want to do this?

Putting a piece cut out from heavy blanket in front of the tweeter would achieve just that - easier to do and you can hear if the result is what you wanted.

In general, playing around with crossover is not a trivial matter if you do not have the equipment to check the results.

 

But if you have to, just insert variable resistor in series with red lead going to tweeter and increase the resistance until the treble is obliterated enough for you.

That way, you will not do any phase shifting which would destroy imaging.

Once the value is known (measured with ohm-meter), you can then buy an audiophile resistor of that value and replace the trimmer with it.

[VanArn]

As has been stated the best position for an attenuation network is between the crossover network and the compression driver. A variable L pad using a (constant impedance) 8 ohm, 50 watt potentiometer would allow for a wide range of level adjustment with minimum of interaction with the HF network which incorporates a great deal of added equalisation.  The original 275 ND titanium diaphragm has a coating applied to smooth its response, if replacements have been fitted they may not have the applied coating.

[kelossus]

14 hours ago, rockeater said:

R3, R3a and R3b in unison with C9, C9a and C10 do the trick, but you should not play with them.

 

The amount of attenuation is 1.2dB and not 1dB and it is not useless.

3dB will cut your treble in half and 6dB would reduce it by another half of that, so you would end up with a quarter of original treble.

Do you really want to do this?

Putting a piece cut out from heavy blanket in front of the tweeter would achieve just that - easier to do and you can hear if the result is what you wanted.

In general, playing around with crossover is not a trivial matter if you do not have the equipment to check the results.

 

But if you have to, just insert variable resistor in series with red lead going to tweeter and increase the resistance until the treble is obliterated enough for you.

That way, you will not do any phase shifting which would destroy imaging.

Once the value is known (measured with ohm-meter), you can then buy an audiophile resistor of that value and replace the trimmer with it.

 

Yes 1db of attenuation is completely useless. These are a 2 way speaker crossing over at around 700hz, it's not just the treble I want to attenuate. These have the typical Japanese JBL voicing and it's incredibly unbalanced IMO. If you heard them as is, I think you would agree.

 

I don't know why you are making so many assumptions like I am obliterating the speaker somehow? You haven't heard these speakers, I am not new to this hobby or tinkering with speakers. I know what a balanced sound is especially in regards to horns and JBLs

Edited February 10, 2024 by kelossus

[kelossus]

25 minutes ago, VanArn said:

As has been stated the best position for an attenuation network is between the crossover network and the compression driver. A variable L pad using a (constant impedance) 8 ohm, 50 watt potentiometer would allow for a wide range of level adjustment with minimum of interaction with the HF network which incorporates a great deal of added equalisation.  The original 275 ND titanium diaphragm has a coating applied to smooth its response, if replacements have been fitted they may not have the applied coating.

 

Would something like the Fostex R100T be ok to insert between the speaker cables and HF terminals?

 

[VanArn]

If you have R 100T,s already they would suit. They are, however, far more expensive than using constant impedance potentiometer controls.  You could use the Fostex attenuator to determine the actual level that suits you and then make up a fixed resistor L pad  to fit to the HF horn speaker's terminals.

Edited February 11, 2024 by VanArn
Typo

[rockeater]

2 hours ago, kelossus said:

Would something like the Fostex R100T be ok to insert between the speaker cables and HF terminals?

I myself would get any potentiometer from Jaycar / Altronics to see what attenuation is needed (one for each channel).

Once you know it, buy the best audiophile resistor you can find of that value and replace the pot with it.

You do not want to add any complexity to he network.

[will robinson]

Hi there, a quick search shows a 2 way speaker with separate HF and LF inputs.

 

If this is the case (and you wish to just reduce the entire HF output) then the easiest way to see if this is what you want I describe below (2 methods).

 

If this isn't what you want you are playing speaker designer and digital manipulation is the way to go.

 

Cheers, will

 

Method 1.

use 2 amps with either different sensitivity or some form of level control to provide different signal level to HF and LF

 

Method 2.

use a tube amp with a range of output taps and use the taps to provide different signal level to HF and LF

 

METHOD 2 REQUIRES A BIT OF RESEARCH

[muon*]

The attenuator sounds like the best option.