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Resistors in series or parallel for a tweeter, discuss?

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nervewrecker
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Resistors in series or parallel for a tweeter, discuss?

Postby nervewrecker » March 1st, 2018, 7:25 pm

I'm crossing a tweeter out of its recommended xover range and wanna attenuate it a bit more than what the 80prs network mode level settings allows.
Bought two resistors and had put them in series to see how it does, allowed a bit more attenuation so I was able to play with the levels a bit more. Well one resistor like it cap out so one tweeter works but that is a next issue :lol:

My question is if putting the resistor in series with the tweeter will affect the sound? Should I Put them in parallel? In my mind it should be parallel but being of a higher impedance (say 16 ohms) it would share less of the load and the tweeter will still receive a lot of power so it wont do much attenuation.

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Brian Steele
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Re: Resistors in series or parallel for a tweeter, discuss?

Postby Brian Steele » March 1st, 2018, 8:29 pm

Stop the guessing, steupps. Use a free software tool like XSim to model the effect on the tweeter. You might actually find that one in series and one in parallel with the tweeter provides the best results :-)

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Re: Resistors in series or parallel for a tweeter, discuss?

Postby nervewrecker » March 1st, 2018, 9:08 pm

Brian Steele wrote:Stop the guessing, steupps. Use a free software tool like XSim to model the effect on the tweeter. You might actually find that one in series and one in parallel with the tweeter provides the best results :-)
Well i learn something today.
Will have to take a look at that.

Much thanks.

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Re: Resistors in series or parallel for a tweeter, discuss?

Postby ruffneck_12 » March 2nd, 2018, 3:27 am

Discovered xsim just last week and I just love it.

But anyhow, If you want attenuation you need a series/parallel circuit as shown below. Aka a voltage divider, aka an L pad
(which Xsim can simulate)

Image

And no it won't affect the sound other than reducing the level. Only caps/coils affect frequency response, resistors just affect level alone.

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Re: Resistors in series or parallel for a tweeter, discuss?

Postby Brian Steele » March 2nd, 2018, 2:28 pm

ruffneck_12 wrote:Discovered xsim just last week and I just love it.

But anyhow, If you want attenuation you need a series/parallel circuit as shown below. Aka a voltage divider, aka an L pad
(which Xsim can simulate)

Image

And no it won't affect the sound other than reducing the level. Only caps/coils affect frequency response, resistors just affect level alone.


Well, technically the series and parallel resistors can effect the "Q" of the resonance around the tweeter's resonance frequency, but usually this a LOT less of an issue with tweeters, particularly as we tend to cross them over quite a bit higher than that.

Using the impedance curve and the frequency response of the tweeter in the sim will indicate if this is an issue.

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Re: Resistors in series or parallel for a tweeter, discuss?

Postby ruffneck_12 » March 2nd, 2018, 10:45 pm

sweeet

by chance, what program do you use to get the frequency response graphs?

Xsim recognises Impedance files from DATS with no problem. But freq response files from TrueRTA is a bit of an issue.

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Re: Resistors in series or parallel for a tweeter, discuss?

Postby Brian Steele » March 3rd, 2018, 12:20 am

ruffneck_12 wrote:sweeet

by chance, what program do you use to get the frequency response graphs?

Xsim recognises Impedance files from DATS with no problem. But freq response files from TrueRTA is a bit of an issue.


If you're going to use an RTA to measure FR (which probably is valid enough for near-field measurements like what you get in a car where all reflections are usually within a small time window), use Room EQ Wizard (REW). REW's RTA feature allows you to capture the response, and then save it as an FRD file. What you won't get with this method though is the phase response, which is important for x-over duty . To get that, you need to use REW's gated sine sweep measurement process. It's fairly simple to set up. Just don't do something silly like feed the tweeter a high-level 20Hz to 20kHz signal for measurement.

REW is an extremely versatile tool It can even be used for impedance measurements and t/s parameter testing, with a simple impedance jig. It might even be better than DATS at this for measuring the t/s parameters of subwoofers, because you can use a larger voltage signal for the measurement. With the jig I have, I can use an amp up to 100W for performing the measurements (of course, at that level, they're no longer SMALL-signal measurements, but still... :) )

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