Active crossovers

Any chance of the "why" to that? I understand as much as to know that 6db of change is a voltage doubling, so for 16 bits, which is 16 possible doublings, there are 6*16=96db of dynamic range. Similarly, for 24 bits, there is 6*24=144db. So this means there's 48db available to attenuate the signal without any loss right?

So, in practice, does that mean the first 48db of attenuation is totally 100% lossless, or is the loss "spread" over the total range of possible attenuation, so you lose a bit of dynamic range even at 99% output?

Also, I'm confused as to working out how the attenuation works, the following rough working out is clearly totally wrong, so can you tell me where I'm going wrong?

I'm going to assume the average good home system needs to go from around 40db to 100db SPL, is that reasonable? So thats 60db of attenuation needed, which assuming each 10db decrease in SPL needs 1/10th as much power means we need 10^-6 = 1 millionth as much power delivered at minimum volume as we do at maximum.

But now I'm completely confused, since there's no way we can throw away 20 bits (2^20 being approx 1 million).

Can someone set me straight or point me in the right direction to correct my obvious buffoonery?

Thanks.

Paul

 

You are right about the first part and 46dB attenuation is pretty much all you need in reality. Once you are below that you probably won't notice the difference in dynamics anyway. My transformer attenuators offer 52dB max attenuation.

I got confused myself reading your stuff and posted a rubbish answer... I think your calculations are pretty much correct but we don't really need -60dB attenuation. -10dB is perceived as about half as loud so the difference from my -52dB attenuation and your -60dB is almost half as quiet again.

Not sure what you mean by the 'spreading it out' thing. You either have 16bits or more of data or you don't!

 

Attenuate volts rather than power. So it's more like a signal ratio of 1/1000.

Paul

 

You didn't understand the point I was making about the Behringer. It isn't completely flexible - sure there are a large number of options, but it cannot implement all transfer functions - should you need a curve it cannot replicate, you compromise with what it can do. [ie. When you only have a hammer everything looks like a nail...]

I suspect you've yet to run out of "FREE" space (see the EQ menu for example). Also, you might want to try creating a -3dB "shelf" from 2-4Khz (with the EQ's you have) while you are there

I can equally well say, that you will find it easier to get the settings you want with a DEQX than with a DCX

 

Okay I see your point but most of the time (unless you have a very strange or badly designed speaker) if you can't do it on the DCX there no way you will want to do it on a passive Xover. To do all the DCX can do in passive would require a hideous number of components.

The DEQX is another step up again but it costs like it too!

I have yet to need anything the DCX can't do because I design the speaker right in the first place

 

xover design 101

xovers need to use the drive unit resistance to work into

this is 8 ohms, however,

the voice coil is an inductor and the resistance/ impedance rises with frequency around the xover point.

also, inducance changes with frequency, current and volts, too!!

and the capacitors can resonate/ring with voice coil inductances and get all sorts of lumps and bumps in the response.

active xovers don't suffer with that. and they also can give more level, as 25% gets lost in the passive xover.

but, due to sound diffraction, you lose some bass level, or alt., gain some mid. level from the bass unit, called baffle step, this can't really be compensated for, unless the active is custom designed for the speakers.

finally, drive unit phase matching, again, most actives don't give anywhere near enough adjustment hear, 180 deg. or so, you need continuous variable phase, as drive unit location, see my other post on that, causes comb filtering and response variations

https://www.audio-forums.com/as-rediect/showthread.php?p=182275#post182275

so conclusion, a good passive is better than a bad active, a proper active is better than a good passive, but, you have to get a custom design, that takes all design factors into account.

by all means try and active, but you don't know the full story, hopefully, you do know a bit more now...

 

70sman, I am pretty sure Bitmonkey has been convinced to just buy a ready-made pair of active speakers.

 

Yes, I can confirm. PMC AML1s are on the horizon. Still going to do a little reading anyway, but more out of interest than any urge to tweak.