From passive to active filter

[terry j]

Originally Posted by soren5

But shouldn't we begin to see more active proven designs then?

hey, dunno. good question, never thought about it.

heck, just had a minutes thought, no good answers popped up! History? 'the way things have always gone'?

OR, just take a design that has already worked out a driver selection that would work together, get your measurement gear out and put in the filters that give you what you want? Flat on axis, whatever.

anyway, I think others might have some ideas on that. good question.

[AllenB]

Originally Posted by soren5

Active and passive XO designs work differently and each have their own advantages and drawbacks, I see that now. So duplicating a passive design with an active doesn't make much sense I guess.

From the point of view of this thread, yes... but from mine there is so much else to designing a crossover which is common ground. The question of passive vs active is just one of implementation, like deciding which brand of nails to use when you're designing a house (so I guess MiniDSP is like a gas fired nail gun )

Originally Posted by terry j

See you in oct allen??

I hope so. Could you give me a bell then? (I'm subscribed to your thread)

[terry j]

Not sure which thread you mean allen, but yeah I should remember when we start adding up 'who is coming this year?'. A dim spark should ignite from somewhere.

we usually end up 'testing something' each year, next was supposed to be 'can we really hear cap differences in a power amp', were going to do a blind test with some of the more vocal 'I can hear differences between wire types in an amp' but they seem to have spat the dummy and it's looking tenuous. I'm not that upset to be frank, the idea of having ten golden ears walking around kinda gave me the heebie jeebies.

SO, long story short, if you have any ideas of what might make an interesting thing to investigate this year throw em into the pot. I am thinking 'why not just a good old dac comparison'...but done blind via instant switching from the LP.

That might throw a spanner into the works of the 'oh my god, every dac is sooo different' and the true relative differences start to emerge.

[weltersys]

Originally Posted by soren5

But shouldn't we begin to see more active proven designs then? I mean, there will always be DIY'ers out there with superior measurement equipment and XO designer skills, who will make great filter designs, passive or active. And if more people in the DIY speaker community are going active, then active proven designs should start to show up, no? (Maybe they already are and I just haven't noticed )

A very real problem with active filters is that using different types of DSP results in differing output response even when all the crossover types, slopes, frequencies, and parametric filters are set the same.

As Bennett Prescott puts it, "the DSP tower of Babel".

Simply put, if I design a crossover using "X" DSP, and a DIY uses those settings on "Y" DSP, they will not measure or sound the same.
The differences may be subtle or gross, the more filters employed the farther off the end results will be.

Even different models under the same parent company often don't match up.
In addition to "Q" variations, there are plain stupid design errors- for instance the DBX DriverackPa inverts polarity between input and output, no big deal when used alone, but the DriveRackPA+ inverts only the midrange outputs.

If someone correctly designed a crossover on that unit, the midrange would be reversed polarity using the same settings on any other "normal" DSP.

Art