gainclone / active xo combination??

[timsch75]

I've decided to go active with my two-way speakers. I have one gainclone and will need to build another. I'll also have to build a box for the xo. I'd rather not build both, so I've been considering either putting two more monoblocks in my case with the dual monos and building a separate box for the xo, or putting the individual crossovers in with the monoblocks and building another dual mono / xo box.

Question is, which is the better decision (if each are bad, please let me know). If I go quad mono, I have four transformers in one box and I'm not sure if there is a problem having them that close to each other. I also don't know if the electric field from the transformer will adversely affect the xo if they are somewhat close together.

I'd prefer to have a quad mono box so that I can fiddle with the xo without having to go into two boxes.

thanks.

tim s

[MBK]

I'd say the 4 mono X-F's are OK in a single case. The X-O I would put it in a second case.

Me though I chose the full monty, I am just building 4 separate monoblocks for my active system and one x-o box per side. The PSU chassis are also separate from the amp chassis. This is more for convenient experimentation though - to have a separate PSU allows to mount any future amp circuit on top easily. You might consider though to put the X-O and the monoblocks close together and to make one x-o per side. This way you have just one long signal cable going to the speakers, rather than 2 speaker cables or more.

[Nuuk]

It is also worth remembering that removing the passive crossover components alters the alignment of your speakers which may result in a change of the box volume (and port dimensions)!

[tiroth]

I say quad mono.

1. You'll be doing a lot of xover fiddling, and you won't have to worry about breaking/disturbing the amps in the process. You can even try out new xover topologies in the future without messing up your main system.

2. The amps are general purpose and can be adapted to another use in the future. Once you integrate the crossover into the amp you'll be loathe to rebuild it for another purpose.

The downside is you need more cables and connectors.

[roddyama]

Originally posted by Nuuk
It is also worth remembering that removing the passive crossover components alters the alignment of your speakers which may result in a change of the box volume (and port dimensions)!

Good point Nuuk. As an extension of that thought, by removing the passive x-over, the tweeter loses the protection from DC and hum from the amp provided by the hi-pass series cap. You may think about adding one to the tweeter to provide a hi-pass cut-off 1 or 2 octaves below the active x-over point.

[MBK]

Rodd,

True, and the tweeter gets the full turn on and off plops as well...

I have some thoughts about having part of the LP implemented passively as well, say, doing 24 dB/oct L-R crossovers, where half the filter is done actively and the other half passively. My thought is that this way, you elegantly filter out any higher order distortions that your amps may create... The mid and the woofer will reproduce only a fraction of their amp's high order distortions.

Corollary: Most people use the "best" amp for the mid, means the woofers get a nasty one. I'm no exception . Problem is, many woofers are perfectly capable to reproduce say, the 5th harmonic of a 100 Hz wave. In a fully active X-O, these go straight to the woofer. Due to Fletcher Munson they should then be disproportionately more audible than the fundamental. With a partly passive LP however, these distortion products are attenuated. And the Mid has its own amp, so the distortion simply goes into heat... Similar for the mid to tweeter. For the tweeter, which has no LP, the trick doesn't work, but again due to Fletcher Munson, it doesn't have to - high order distortion above 3000 Hz has less and less subjective loudness...

I just don't crave for the calculations necessary to split the X-O into active and passive...

[timsch75]

A tweeter cap has already been planned. Concerning box volume, I'll just add some material to compensate for the lost components. Oversizing the box a bit more just lowers the overall Q, right (it is a closed box)? If so, that will be alright with me. With alignment, I'm not sure what to do about it. My knowledge is limited. I thought time alignment had to do with the driver centers being aligned vertically, and as long as the drivers were in phase, then alignment is fine. Will going active alter the phase if the xo order is kept the same?

thanks

[Nuuk]

If your speakers are the closed box type, the problem with the change of alignment is much less significant than with the ported types.

I always ran my active speakers with a Velleman speaker protection module - just to be on the safe side.

[planet10]

If the case i have, has enuff heatsink to support it, i plan on putting 4 channels with 2 trafos into it, to biamp. I hope to have enuff room for the active XO as well.

dave

[timsch75]

I just looked into the Velleman speaker protection kit and have a couple of questions. I'm not familiar with "burn out" of an amp, and google hasn't shown me much. does it occur when the amp is turned on/off? The gainclone I built seems pretty constant at 20mV cd measured at the speakers, but I don't know if there are times when it may be more. What does it do to speakers? How can I tell if my drivers have been affected?

The kits are for speakers, but with each driver being driven by a different amp, do I need two kits per speaker?

thanks

tim s