simple biamp question

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Hi all,
I am building up some 3 way speakers. Decided to biamp them.
This is REALLY diving into the deep end for me but so far so good.
The good news is that I made a power supply that seems to work great. Yea! And I made 4 lm3886 modules that work great. Yea!

Now I'm wondering about something. My mid/high speakers are about SPL 96 or a little higher. My Woofer is around SPL 94 or a bit lower. What are my best options for changing/matching the relative volume/sensitivity? Would it work to just lower the gain a little on the mid/high amps?

MrKramer
 
mrkramer said:
My mid/high speakers are about SPL 96 or a little higher. My Woofer is around SPL 94 or a bit lower. What are my best options for changing/matching the relative volume/sensitivity? Would it work to just lower the gain a little on the mid/high amps?
For a 2 dB difference the gain for the mid/high amps would have to be set to around 80 % of the woofer amp's.

Another simple solution would be to use a voltage divider for the mid/high parts of the cross-over. Either two resistors, e. g. 2k + 8k2 or a potentiometer/trimmer. You should post a schematic of the cross-over to make sure, where to put it without changing the cross-over characteristic.
 
I don't have an active preamp before this, only a stepped attenuator. The XO is just a simple RC filter like the one here:
http://www.t-linespeakers.org/tech/filters/passiveHLxo.html
If I was going to pad down the mid/tweet I thought of putting the 2 resistors after the filter. So Attenuator>XO>Pad>Amp
Since I don't have an active pre, I thought it might be better to reduce the gain a little rather than drop down the signal. Make any sense?
How would I relate gain to DB?

MrKramer
 
Re: Re: simple biamp question

mrkramer said:
If I was going to pad down the mid/tweet I thought of putting the 2 resistors after the filter. So Attenuator>XO>Pad>Amp
Yes, as long as Pad and Amp together have the same impedance as before R2 and Amp.

mrkramer said:
How would I relate gain to DB?
Here is a calculator. Scroll about half-way down the page and use the Voltage V to Voltage Level Lu calculator. Makes it easy to calculate. 0 dB are 1 V and -2 dB are 0,79... V Those numbers are proportional to the gain. So, e. g. if the woofer amp has a gain of 20, the mid/tweeter amp should be set to ~16.
 
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