Hello,
I finished measuring and found that we speak of a - 0.7 dB level at 20 kHz, so I don’t really think that there is any reason to resort to a drastic solution like cutting with a dremel.
I have chosen (Like Tyler suggested) to mark the boards where the x100 setting is used, and adjusted these boards to have the right gain at 20 kHz using this multiplication setting. This way I will use these boards for midrange and treble, and the others can be used for bas and sub. I think this is the easiest way to get around the problem.
\Jens
I finished measuring and found that we speak of a - 0.7 dB level at 20 kHz, so I don’t really think that there is any reason to resort to a drastic solution like cutting with a dremel.
I have chosen (Like Tyler suggested) to mark the boards where the x100 setting is used, and adjusted these boards to have the right gain at 20 kHz using this multiplication setting. This way I will use these boards for midrange and treble, and the others can be used for bas and sub. I think this is the easiest way to get around the problem.
\Jens
resistor values
Sorry I didn't post this earlier. What is being found is consistent with the summary conclusions found in:
http://focus.ti.com/lit/an/sloa024b/sloa024b.pdf
The recommendation for Sallen-Key filter resistors is in the range of hundreds to several thousand ohms. Capacitance is the culprit.
Regards
Sorry I didn't post this earlier. What is being found is consistent with the summary conclusions found in:
http://focus.ti.com/lit/an/sloa024b/sloa024b.pdf
The recommendation for Sallen-Key filter resistors is in the range of hundreds to several thousand ohms. Capacitance is the culprit.
Regards
since i am finally ordering parts to populate my MOX boards, i had a question regarding values for the main board..
i will be using these exclusively with one pair of speakers, and they will be matched to those speakers. from the manual, i can see that the speakers use a 2-way, 6dB/octave xover at 1100hz.
instead of stuffing the mox board with all the values, i can just use what i need, right? and instead of jumpers, just hard-wire it to the speakers' requirements?
i assumed the above. the real question is what do i do with the q? do i just keep it at 1.0 for both HP and LP? thanks for any answers!
i will be using these exclusively with one pair of speakers, and they will be matched to those speakers. from the manual, i can see that the speakers use a 2-way, 6dB/octave xover at 1100hz.
instead of stuffing the mox board with all the values, i can just use what i need, right? and instead of jumpers, just hard-wire it to the speakers' requirements?
i assumed the above. the real question is what do i do with the q? do i just keep it at 1.0 for both HP and LP? thanks for any answers!
cowanrg said:
Hi,
Theoretically, your conclusions are correct.
However, I would suggest putting such crossover elements that would enable you to choose slope 6 or 12dB/oct and crossover frequency from 800Hz to 3.15kHz. This would allow you to fine-tune the crossover because final crossover frequency in a 6dB crossover will be, in most cases, the result of combining the driver's natural roll-off and the crossover's slope. For this reason, you will occasionally notice that LPF may be set to 1.5kHz and HPF to 2 or 3 kHz, for example.
Besides, a bit of experimenting can't hurt.
Regards,
Milan
im not sure why you are suggesting i experiment? i really dont want to mess around with different settings. do you really think i could improve upon the crossover frequency? these are planar speakers if that makes any difference... i have seen many people build either outboard passive xovers, or active xovers, and 99% of people use the factory xover point (the other 1% im just not sure about).
anyone else see a benefit in playing around with xover points? in the manual they even state if you are going to do an external active crossover to use 1,000 hz, not 1100 like the passive...
anyone else see a benefit in playing around with xover points? in the manual they even state if you are going to do an external active crossover to use 1,000 hz, not 1100 like the passive...
Since it is only a few extra components, I'd definitely stuff enough to try a few things out. I mean, after all the effort it takes to build the speakers, amps, and MOX, don't you want to be sure the sound is the best possible? That is really the entire purpose of MOX, there is no need to say "I've resoldered this circuit 5 times, I give up!"
sorry if i offended you in any way.
i am just ignorant with electronics, and VERY ignorant with loudspeaker design. as i understand it, a speaker has a pretty set crossover point. im just looking to replace the passive xover (with JUNK components) with this active one. thats all. i dont really want to reinvent the speakers. as many of you know, i have too many other half-finished projects
so, sorry if i came across rude, i didnt intend that. i am just unaware of any benefit with tamperint with xover points in a commercial loudspeaker. if there is one, im all for it, i just didnt realize there was.
i am just ignorant with electronics, and VERY ignorant with loudspeaker design. as i understand it, a speaker has a pretty set crossover point. im just looking to replace the passive xover (with JUNK components) with this active one. thats all. i dont really want to reinvent the speakers. as many of you know, i have too many other half-finished projects
so, sorry if i came across rude, i didnt intend that. i am just unaware of any benefit with tamperint with xover points in a commercial loudspeaker. if there is one, im all for it, i just didnt realize there was.
Well, it sounds as though someone may already have done the work of determining the proper Fc, Q, and order for your particular design. If this is the case, and if you trust that person's judgement, then there may not be a lot to gain from expermiementation, although I would encourage it. (as moamps said, this is DIY)
The more typical case, replacing a passive xover with an active one a priori, you cannot assume simply because you know the passive points and topology that you know the proper active parameters. Even proper simulation of the crossover/loudspeaker system does not always reveal the proper design choices.
The more typical case, replacing a passive xover with an active one a priori, you cannot assume simply because you know the passive points and topology that you know the proper active parameters. Even proper simulation of the crossover/loudspeaker system does not always reveal the proper design choices.
For a good example, check out this thread. You can see that the active filter is not quite making it because of the impact of the driver inductance etc.
I made a mistake here, I should have tried higher Q values for a better fit.
http://www.diyaudio.com/forums/showthread.php?threadid=8541
This was the process I went through to create an active filter from a known passive filter. But, it sounds like this work may have been done for you already?
I made a mistake here, I should have tried higher Q values for a better fit.
http://www.diyaudio.com/forums/showthread.php?threadid=8541
This was the process I went through to create an active filter from a known passive filter. But, it sounds like this work may have been done for you already?
well, it just states in the manual that if using an external (doesnt specify whether active or passive), to use a 1khz xover point...
audio research actually did make an outboard active xover that was designed for my speakers, but i think its variable, so it works with different xover points...
now another question... with xovers (regarding active and passive), does the driver type make a difference? for instance, my speakers dont use conventional cone drivers, but are planers. does this change the characteristics at all of the xovers?
audio research actually did make an outboard active xover that was designed for my speakers, but i think its variable, so it works with different xover points...
now another question... with xovers (regarding active and passive), does the driver type make a difference? for instance, my speakers dont use conventional cone drivers, but are planers. does this change the characteristics at all of the xovers?
It should differ because of the effect of the drivers on the passive crossovers. Active crossovers have a power amplifier in between them and the speakers, so the reverse emf and impedences, etc. are not affecting the active xover. The passive is more a part of a complex circuit including the drivers. Just saying it is different, not suggesting how or what to modify to match them. Being able to tweek easily is a good thing. -Marsupialx
OK...
From the dumbest MOX constructor in North America...
I'm ready to fire this up but I don't want to really "fire" it up!
I built the discreet op-amp boards and would like to know which way they plug in? Q1 Does the component side face the power input side of the board or the proto side of the board?
I will be using a 15VDC supply from a wall wart. I recall being told that it has to be AC but that doesn't make sense to me.
Q2 Should be a 110VAC/15VDC transformer, right?
At least smart enough to ask before applying power...
Thanks!
From the dumbest MOX constructor in North America...
I'm ready to fire this up but I don't want to really "fire" it up!
I built the discreet op-amp boards and would like to know which way they plug in? Q1 Does the component side face the power input side of the board or the proto side of the board?
I will be using a 15VDC supply from a wall wart. I recall being told that it has to be AC but that doesn't make sense to me.
Q2 Should be a 110VAC/15VDC transformer, right?
At least smart enough to ask before applying power...
Thanks!
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