# Attenuating a Tweeter



## MorfiusX (Sep 4, 2009)

I was going to write a very long winded description of the problem, but instead decided to keep it simple.

I need to attenuate my right tweeter (see Civic link in sig) by 1 or 2 DB. It is a 4ohm speaker running active crossovers. I can not independently attenuate it using my processor. In short, I need a way to attenuate the RCA going into the amp, or after amplification. 

The amp is capable of 150w, but I am only probably pushing 25-50w to the speaker. I would prefer some adjustability. I was thinking a decent quality pot would work, but this is where I need feedback as I don't know what I should look for.


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## Abaddon (Aug 28, 2007)

Lower the gain on the amp?


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## I800C0LLECT (Jan 26, 2009)

Typical gain is for 2 channels. That would resolve the issue for said tweeter but present itself in the other tweeter.


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## Abaddon (Aug 28, 2007)

oh, sorry.. I completely missed the RIGHT TWEETER part..

thought he wanted to attenuate the pair.


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## MorfiusX (Sep 4, 2009)

Abaddon said:


> oh, sorry.. I completely missed the RIGHT TWEETER part..
> 
> thought he wanted to attenuate the pair.


If only it was that easy... 

A resistor would work to, but I don't what values to look for on that either.


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## Patrick Bateman (Sep 11, 2006)

MorfiusX said:


> I was going to write a very long winded description of the problem, but instead decided to keep it simple.
> 
> I need to attenuate my right tweeter (see Civic link in sig) by 1 or 2 DB. It is a 4ohm speaker running active crossovers. I can not independently attenuate it using my processor. In short, I need a way to attenuate the RCA going into the amp, or after amplification.
> 
> The amp is capable of 150w, but I am only probably pushing 25-50w to the speaker. I would prefer some adjustability. I was thinking a decent quality pot would work, but this is where I need feedback as I don't know what I should look for.




L pad calculator - attenuation dB damping impedance decibel loudspeaker - sengpielaudio Sengpiel Berlin

Go to Radio Shack, buy two 10 ohm resistors and four 1ohm resistors. That will be $2.97. A 12ohm resistor and a 1ohm resistor in an L-Pad will attenuate a 4ohm resistor by 2.5db. Be sure to make an L-Pad; simply putting resistors in series doesn't work half as well because of some issues I'm too lazy to type up


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## MorfiusX (Sep 4, 2009)

Patrick Bateman said:


> L pad calculator - attenuation dB damping impedance decibel loudspeaker - sengpielaudio Sengpiel Berlin
> 
> Go to Radio Shack, buy two 10 ohm resistors and four 1ohm resistors. That will be $2.97. A 12ohm resistor and a 1ohm resistor in an L-Pad will attenuate a 4ohm resistor by 2.5db. Be sure to make an L-Pad; simply putting resistors in series doesn't work half as well because of some issues I'm too lazy to type up


Does it matter if I create the l pad at the amp side or speaker side? It would be a lot easier for me to do it at the amp. There is about 10 to 12 feet separating the amp from the speaker.


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## tanakasan (Sep 8, 2007)

^^Should not matter...

Or buy one of those inline RCA level knobs and use only one side? Probably is a voltage divider anyway.

Robert


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## MorfiusX (Sep 4, 2009)

tanakasan said:


> ^^Should not matter...
> 
> Or buy one of those inline RCA level knobs and use only one side? Probably is a voltage divider anyway.
> 
> Robert


I am going to use one of these:
Parts-Express.com:L-Pad 100W Stereo 1" Shaft 8 Ohm | tweeters tweeter stereo pad PA network mounting midrange L-Pads l-pad l pad Crossovers ads 8 ohm 10 ohm

It's an stereo 8ohm l-pad. If I wire them in parallel, it will run at 4ohm and handle 200w.


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## tanakasan (Sep 8, 2007)

I was thinking more like this...works at the RCA/low level. Only need one, correct?!

Robert

PAC LC-1 RCA SUBWOOFER/ BASS LEVEL CONTROL KNOB LC1 - eBay (item 270475936352 end time Mar-25-10 09:06:35 PDT)


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## MorfiusX (Sep 4, 2009)

tanakasan said:


> I was thinking more like this...works at the RCA/low level. Only need one, correct?!
> 
> Robert
> 
> PAC LC-1 RCA SUBWOOFER/ BASS LEVEL CONTROL KNOB LC1 - eBay (item 270475936352 end time Mar-25-10 09:06:35 PDT)


That would probably work. I've already built the l-pad with the PE item. It's on my way home from work, so I picked it up last night. I'll post pics this weekend. It works quite well.


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## benny (Apr 7, 2008)

Whats the problem with just a resistor in series?


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## MorfiusX (Sep 4, 2009)

benny said:


> Whats the problem with just a resistor in series?


First, as Patrick alluded to, just a resistor in series can cause impedance problems. This problem is solved by creating an l-pad. Info can be found here:
L-PADS

Second, a static l-pad makes it difficult to adjust the attenuation. I didn't know exactly how much attenuation I needed and I didn't want to rebuild the l-pad 5+ times.

With the l-pad I linked above, I can tweak until I get it just right without having to rebuild the l-pad.


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## AudioAmbiance (Mar 3, 2010)

What you're proposing would certainly work. I would question the use in a SQ system. One of the reasons for running active is to take away the issues with lower quality passive components (have you priced capacitors lately?). I would use this L-pad or similar pot to get the sound you're looking for, measure the resistance values, then buy Mills resistors to replace it permanently. Lower quality resistors can introduce sibilance and hash pretty easily...something a tweeter can reveal quite easily. Just my thoughts from my experience with speaker building and tweaking.


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## tanakasan (Sep 8, 2007)

So, AudioAmbiance...

Just a question regarding the RCA unit I proposed: would it introduce issues as it is passive? Would it be somewhat cleaner/better since it occurs in the low level realm?

Thanks!

Robert


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## lycan (Dec 20, 2009)

benny said:


> Whats the problem with just a resistor in series?


network impedance has no choice but to increase, with a single resistor. Won't matter, if purely active.

But with a series _and_ shunt resistor, the _two_ degrees of freedom you now have allow you to simultaneously satisfy _two_ constraints : attenuate tweeter by desired amount, keep total network (input) impedance equal to 4 ohms. It's significant if you're using passive xovers.

By the way ... anytime you put resistors in series with tweets, you just may uncover another possible value of a Zobel  The impedance of a tweet rises in the upper treble (due to its voicecoil inductance), and therefore so will the voltage across the driver, if the driving impedance is resistive. Not too many will care, though, if response above say 10kHz rises.


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## AudioAmbiance (Mar 3, 2010)

The PAC LC-1 would work if applied to just the RCA input for the right tweeter. Just keep in mind, the solution is now adding more components that can have significant variance - the RCAs to and from the LC-1 and the LC-1 itself. Ideally, you want to filter in the low level domain to reduce noise as low as possible before amplification, however I would prefer to attenuate a large signal. Again, the quality of components is the largest factor. If the idea was use a Volume Control, I would tie in an ALPS blue velvet for SQ. 

Again, I would stand behind using Mills resistors for the L-pad. I would certainly shy away from sand cast resistors from Radio Shack or anywhere else. You can experiment to get the right value, but they would most likely taint the sound so much, you would end making changes again anyway. I have bunches of sand cast resistors I would happily donate to the cause! Eagle resistors are a decent option as well. For a buck apiece, you can experiment and not break the bank. For simplicity, you can crimp on spades and swap out as much as necessary and then solder your final configuration. 

I guess it all depends on how sensitive and/or "trained" your ears are. What sounds right to you is what you should go with.


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## mosconiac (Nov 12, 2009)

lycan said:


> network impedance has no choice but to increase, with a single resistor. Won't matter, if purely active.
> 
> But with a series _and_ shunt resistor, the _two_ degrees of freedom you now have allow you to simultaneously satisfy _two_ constraints : attenuate tweeter by desired amount, keep total network (input) impedance equal to 4 ohms. It's significant if you're using passive xovers.
> 
> By the way ... anytime you put resistors in series with tweets, you just may uncover another possible value of a Zobel  The impedance of a tweet rises in the upper treble (due to its voicecoil inductance), and therefore so will the voltage across the driver, if the driving impedance is resistive. Not too many will care, though, if response above say 10kHz rises.


As usual, a very informative, complete, & intelligent answer. You are an incredible asset to this forum, sir.


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## benny (Apr 7, 2008)

Thank you for a real answer, WW.


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