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Hi, I'd like to boost treble a little (2 dB). Now what resistor should I alter? R4 or R5? Both?
Thank you !
Damn, I've lost my stars! I'll do that later
Jacques
3dB is the smallest difference in sound pressure an human ear can recognize.
//Bo.A long list...
Yes, some physical experiements, say that human ear cant hear difference in less then 3dB, but i reality, my experience is the oposit. Less then one dB differnce is difficult for my ear, but I tune equalizers dB by dB thousands of times a day in my work and to me a 2dB change is dramatic. I guess this is different for people.I am not super expert in crossover but my suggession would be for you to soldier a 7 or 8 Ohm resistor parallel with R4, to achieve a 2dB boost.Smart thing with soldier parallell is that by two cuts of the pliers you are back to orginal if you are not happy with your mod.
My re-capped M75 are my precious diamonds.
chartz:Damn, I've lost my stars! I'll do that later
Try to get at least 5 stars, you deserve it.
Collecting Vintage B&O is not a hobby, its a lifestyle.
Christian Christensen:I am not super expert in crossover but my suggession would be for you to soldier a 7 or 8 Ohm resistor parallel with R4, to achieve a 2dB boost.
I suspect it will also alter the crossover frequency of the tweeter network (more so than a larger R5 would). Modifying the original design will mess up the crossover somewhat anyway, so I don't suppose that would be any issue in practice, and the way you suggest is easier.
--mika
Mika, yes I suspect a slight differnce aswell, being not the bigest expert on crossovers, but in state of capacitors passing through, you can see the as a resistor network and thats how I see it.
Then how much this small change of change would affect the filter frequence and steep is for people with more knowledge then I to respond.
Anyone here for an qualified answer ?
chartz, tryIts not gonna kill your speakers, even with a slitght change in crossover point.
I did similar change to my M75, and the reslut was wonderful
Thanks for the answers!
I would like to achieve that treble boost and not change the crossover low cut frequency.
And the MC120 being a pain to open...
I have now talked with a friend that has designed crossover for years.He has read the thread.As R4 is in direct serie with a capacitor, yes changing R4 will also change the filter frequence, but its a matter of only a few procent .His answer is that you increase the value of R5 with 50-100% which will force enough more current through the tweeter, to achieve what you need.
Thank you very much!
I will do the mod, measure output and tell you whether it is an improvement.
Consider that the tolerence of the capacitors in the filter by orginal is 10 to 20 %. imagine how how filter frequence could change from intended point ?, unless they were manually matcing capacitors a the factory, which we dont know.
So a few procent impact is really nothing.