Hi Guys and girls.
I've been thinking of my next project. I have some drivers lying around and I'm going to sus up a box for them. I don't really know too much about them except thier size so I'm going to use an electronic cross over (crossover?) and tune them up that way. I know that is probably herasy but I figure if I use some pleasing proportions on the box and make it look nice I can always give them away as a present!
Bi amping/tri amping: Is this when you put an electronic cross over in between the source and the amp(s)? Then you run seperate channels to each driver?
Is there a benefit to separating the signal before the amp vs after? Because all things being the same, I think using one channel per driver is a lot of channels.
I'm thinking of putting the electronic cross overs in the boxes. I have some 8 inch speakers, some 4 inch speakers and some 1 inch silk tweeters somewhere.
Do electronic cross overs allow you to adjust the volume to each driver as well as cross over points? That would totlally negate the need for impedence matching.
I've seen a bunch of electronic cross overs on ebay from $20 on up to $80. Is one better than the other? Anyone care to discuss merits of a brand or type?
I'll take some photos of the drivers tomorrow and post them so you can see what I got and talk me down.
Thanks for your input.
Best regards,
Spencer
www.emergencydpt.com
I've been thinking of my next project. I have some drivers lying around and I'm going to sus up a box for them. I don't really know too much about them except thier size so I'm going to use an electronic cross over (crossover?) and tune them up that way. I know that is probably herasy but I figure if I use some pleasing proportions on the box and make it look nice I can always give them away as a present!
Bi amping/tri amping: Is this when you put an electronic cross over in between the source and the amp(s)? Then you run seperate channels to each driver?
Is there a benefit to separating the signal before the amp vs after? Because all things being the same, I think using one channel per driver is a lot of channels.
I'm thinking of putting the electronic cross overs in the boxes. I have some 8 inch speakers, some 4 inch speakers and some 1 inch silk tweeters somewhere.
Do electronic cross overs allow you to adjust the volume to each driver as well as cross over points? That would totlally negate the need for impedence matching.
I've seen a bunch of electronic cross overs on ebay from $20 on up to $80. Is one better than the other? Anyone care to discuss merits of a brand or type?
I'll take some photos of the drivers tomorrow and post them so you can see what I got and talk me down.
Thanks for your input.
Best regards,
Spencer
www.emergencydpt.com
What Bi-/Tri-amping is
Hi!
For a very good explanation of what bi- and tri-amping is about, see:
http://sound.westhost.com/bi-amp.htm
... and ...
http://sound.westhost.com/bi-amp2.htm
These two articles got be convinced, and when I heard the results later (after DIYing amps and x-overs for two years), it was the largest improvement in audio quality I've ever heard. I didn't even use expensive drivers or components, just "decent" stuff.
Hi!
For a very good explanation of what bi- and tri-amping is about, see:
http://sound.westhost.com/bi-amp.htm
... and ...
http://sound.westhost.com/bi-amp2.htm
These two articles got be convinced, and when I heard the results later (after DIYing amps and x-overs for two years), it was the largest improvement in audio quality I've ever heard. I didn't even use expensive drivers or components, just "decent" stuff.
I also prefer active. For main to sub XO it is the only way to go as inductors for an <80Hz XO are hard to source. Yes, it costs a bunch to get going but once you have 6-8 channels of amplification experimenting and/or new project becomes a matter of minor inexpensive tweaks.
Theoretically, active and passive crossovers with the same transfer function will sound identical. This doesn't consider the headroom improvement that Rod Elliot talks about in his article.
You can also go mixed mode. Active XO woofer to mid, and passive mid to tweeter. This would allow a 3 way with only 4 channels of amplificaiton.
It is smart to have a cap in series with the tweeter to protect it from DC on the amp's output. You could make this cap part of the XO or just make it big enough that it is a DC blocker. I cannot hear a difference with or without the cap (2 x 12 uf Axon) using Focal TC120 tweeters, so I left them in for peace of mind.
Most of the inexpensive ready made active XO's are pretty basic - textbook symmetric slopes and no eq, delay or baffle step compensation. If you are crossing at the baffle step you can use the level adjustment to compensate, but that limits you. Also, see Mark K's pages for the impact that this scheme has on power response.
If you want a relatively inexpensive full featured crossover, take a look at the Behringer DCX2496. I haven't used one but plenty of folks around here love theirs.
For DIY analog active crossovers, the best reference around is http://www.linkwitzlab.com/filters.htm Adding phase compensation to my XO (correcting for XO phase shift and mid/tweeter acoustic offset) made more difference than anything else. Transients suddenly became precisely focused. My teenage son even noticed the improvement without my pointing out I'd made a change.
It is possible to build an active crossover on perfboard, but it takes a lot of time and attention to detail.
Sorry, I don't have any XO boards leftover from the group buy. There were over 1,500 sold, so I bet if you ask in the thread there will be someone willing to part with the boards that they bought for the project that never happened.
Theoretically, active and passive crossovers with the same transfer function will sound identical. This doesn't consider the headroom improvement that Rod Elliot talks about in his article.
You can also go mixed mode. Active XO woofer to mid, and passive mid to tweeter. This would allow a 3 way with only 4 channels of amplificaiton.
It is smart to have a cap in series with the tweeter to protect it from DC on the amp's output. You could make this cap part of the XO or just make it big enough that it is a DC blocker. I cannot hear a difference with or without the cap (2 x 12 uf Axon) using Focal TC120 tweeters, so I left them in for peace of mind.
Most of the inexpensive ready made active XO's are pretty basic - textbook symmetric slopes and no eq, delay or baffle step compensation. If you are crossing at the baffle step you can use the level adjustment to compensate, but that limits you. Also, see Mark K's pages for the impact that this scheme has on power response.
If you want a relatively inexpensive full featured crossover, take a look at the Behringer DCX2496. I haven't used one but plenty of folks around here love theirs.
For DIY analog active crossovers, the best reference around is http://www.linkwitzlab.com/filters.htm Adding phase compensation to my XO (correcting for XO phase shift and mid/tweeter acoustic offset) made more difference than anything else. Transients suddenly became precisely focused. My teenage son even noticed the improvement without my pointing out I'd made a change.
It is possible to build an active crossover on perfboard, but it takes a lot of time and attention to detail.
Sorry, I don't have any XO boards leftover from the group buy. There were over 1,500 sold, so I bet if you ask in the thread there will be someone willing to part with the boards that they bought for the project that never happened.
Thank you for your responses Pelle, Frank, Bob, and Dave. The reading material is interesting if on the heavy side. I wish I had paid attention in speaker building class.
Now I'm left to muddle through. Dave, how would you modify this unit or is there something else that you have listened to? These units are selling for $269 on fleabay.
So I would put this before the amps in the signal path then bi or tri wire the speakers? We are getting to the point of having a lot of wires here. Not to say that I don't like wires and gagetry but I have to be convinced of a benefit.
I enjoy the conversations I have on here. This is probably one of the nicest forums I've had the pleasure of posting on.
Thank you.
-Spencer
Now I'm left to muddle through. Dave, how would you modify this unit or is there something else that you have listened to? These units are selling for $269 on fleabay.
So I would put this before the amps in the signal path then bi or tri wire the speakers? We are getting to the point of having a lot of wires here. Not to say that I don't like wires and gagetry but I have to be convinced of a benefit.
I enjoy the conversations I have on here. This is probably one of the nicest forums I've had the pleasure of posting on.
Thank you.
-Spencer
So, Dave, you are the exception that proves the rule 
Empirically, it is a pro-sound piece, so it expects to see a signal that is hotter than what we are likely to feed it in home use. The less than full scale signal is then digitized using less than the 24 bits available. An unbalanced to balanced converter might help.
Another possibility to keep the DCX2496 running at higher levels would be to feed it an unattenuated (digital?) signal and attenuate the output for volume control. Of course a six channel balanced attenuator becomes expensive in a hurry.
Edit: The first link Pelle gave you has a diagram that shows how the connections are made right at the top of the article. Collectively the los pass and high pass filters are the active XO, which could be the Behringer.
Empirically, it is a pro-sound piece, so it expects to see a signal that is hotter than what we are likely to feed it in home use. The less than full scale signal is then digitized using less than the 24 bits available. An unbalanced to balanced converter might help.
Another possibility to keep the DCX2496 running at higher levels would be to feed it an unattenuated (digital?) signal and attenuate the output for volume control. Of course a six channel balanced attenuator becomes expensive in a hurry.
Edit: The first link Pelle gave you has a diagram that shows how the connections are made right at the top of the article. Collectively the los pass and high pass filters are the active XO, which could be the Behringer.
EmergencyDpt said:
Crossover design is one of the most complex, yet most important elements of speaker design. Don't expect to master it in one go, but don't be intimidated by it either. I think that one of the inexpensive behringer units is a very good idea. It will allow you to quickly try different crossovers, including delay and level setting. Only through some trial and error and experience through your own ears will you get a grasp of how different elements affect the sound.
I think that the sound qualities that Dave perceives as being deficient with the unit will not prevent you from hearing the differences in different crossover designs. Once you have narrowed in on basic parameters, you can either build analog versions with high quality op-amps or discreet components, or a combination of the two. In the meantime you can look into improving the behringer unit. But if you like the convenience of a digital device, rather than modding that unit, you might consider using a PC with a good sound card and as your source. Some very powerful crossover and EQ design programs are now readily available. But they have a learning curve if you are not a PC jock.
Sheldon
Mods for DCX
Regarding mods for the DCX 2496.
There are many threads on this topic in this forum and some very good advice in a Yahoo forum. Search the threads.
My quick suggestions.
1. Do NOT buy a used unit. Get one new from a vendor who has a good return policy (Same Day Music or Musician's Friend etc). The quality control is not great, so you may need to exchange the unit, hence my advice above.
2. Keep you expectations reasonable. These are inexpensive units (less than $300), so the idea of spending a thousand to perform upgrade modifications is very questionable. This is especially true since the reliability may not be the best to begin with.
3. Do not use the the ADC on the unit. Use the digital output from your source (I assume you are using a CD player). Avoid this extra conversion, since there are many ways to do this incorrectly (i.e., maximizing the bits to the voltage range).
4. A good mod is replace the analog output section with transformers (many threads on this topic). In order of cost (descending): Jensen, Cinemag, and Edcor would be good candidates. Yes, you can always spend more but those other alternatives can be quite expensive. They probably sound better, but again this is a $300 unit. You will also need a simple RC filter to help with anti-aliasing - not a big deal.
The output section is the weak link on this unit. Others will do mods on the clock & power supply. But those should come second in my opinion. Try the transformer trick first. The Edcor transformers will only cost about $8-15 per channel and it is not very difficult for a DIYer. This will make an audible improvement. Again you can always spend more... but I will not enter into that debate.
To get an electronic crossover from another manufacturer that has the same functions and that is also of better build quality and reliability will be substantially more expensive. However, in terms of value per dollar, the Behringer is pretty good, especially with some minor mods.
Good Luck.
Regarding mods for the DCX 2496.
There are many threads on this topic in this forum and some very good advice in a Yahoo forum. Search the threads.
My quick suggestions.
1. Do NOT buy a used unit. Get one new from a vendor who has a good return policy (Same Day Music or Musician's Friend etc). The quality control is not great, so you may need to exchange the unit, hence my advice above.
2. Keep you expectations reasonable. These are inexpensive units (less than $300), so the idea of spending a thousand to perform upgrade modifications is very questionable. This is especially true since the reliability may not be the best to begin with.
3. Do not use the the ADC on the unit. Use the digital output from your source (I assume you are using a CD player). Avoid this extra conversion, since there are many ways to do this incorrectly (i.e., maximizing the bits to the voltage range).
4. A good mod is replace the analog output section with transformers (many threads on this topic). In order of cost (descending): Jensen, Cinemag, and Edcor would be good candidates. Yes, you can always spend more but those other alternatives can be quite expensive. They probably sound better, but again this is a $300 unit. You will also need a simple RC filter to help with anti-aliasing - not a big deal.
The output section is the weak link on this unit. Others will do mods on the clock & power supply. But those should come second in my opinion. Try the transformer trick first. The Edcor transformers will only cost about $8-15 per channel and it is not very difficult for a DIYer. This will make an audible improvement. Again you can always spend more... but I will not enter into that debate.
To get an electronic crossover from another manufacturer that has the same functions and that is also of better build quality and reliability will be substantially more expensive. However, in terms of value per dollar, the Behringer is pretty good, especially with some minor mods.
Good Luck.
Making an active crossover or filter is not that complex; an op amp, a few capacitors, a few resistors...done.
The problem is making a variable adjustable crossover. If you are going to use this to test some unknown speakers (unknown parameters) then you need a range of selection of crossover frequencies, slopes, levels, as well as, possibly, 'Q'. It is these features that raise the cost of a variable multi-channel active crossover.
Now, if you know precisely what you want, then you can pre-determine the frequency and slope of the crossover. But other factors come into play as well. What if one of your speakers has a slight peak in the frequency response, then you have to add a circuit to tune down that peak.
Also, baffle step correction comes into play, rarely is baffle step at the same location as the low crossover frequency, so you either need to attenuate the upper aspects of the circuit to balance the sound or you have to boost the bass below the baffle step.
Whether buying or building, crossovers are not easy. Though, if you have the skill at electronics, active crossovers, in one sense, are easier and more flexible since the components are cheap and easy to change, and the circuit is relatively easy to add to.
Even the easiest path is still not that easy.
Of course, that is just one man's opinion.
Steve/bluewizard
The problem is making a variable adjustable crossover. If you are going to use this to test some unknown speakers (unknown parameters) then you need a range of selection of crossover frequencies, slopes, levels, as well as, possibly, 'Q'. It is these features that raise the cost of a variable multi-channel active crossover.
Now, if you know precisely what you want, then you can pre-determine the frequency and slope of the crossover. But other factors come into play as well. What if one of your speakers has a slight peak in the frequency response, then you have to add a circuit to tune down that peak.
Also, baffle step correction comes into play, rarely is baffle step at the same location as the low crossover frequency, so you either need to attenuate the upper aspects of the circuit to balance the sound or you have to boost the bass below the baffle step.
Whether buying or building, crossovers are not easy. Though, if you have the skill at electronics, active crossovers, in one sense, are easier and more flexible since the components are cheap and easy to change, and the circuit is relatively easy to add to.
Even the easiest path is still not that easy.
Of course, that is just one man's opinion.
Steve/bluewizard
http://t-linespeakers.org/tech/filters/passiveHLxo.html
Note: if your HF amp has input impedance <50K you may well need to buffer that section.
dave
Here is a preamp schematic for my amplifier. It has a adjustment pot for cross over frequency attenuation but the idea behind it should be transferabe to almost anything.
I find BiAmping to be a very versitale feautre on my Bass Guitar rig as long as drive and cab selection is setup around the same concept. I get much more solid lows with far great power handling and the same is siad for the highs. It all seems to work better when the speaker are kept closer to their natural voicing.
Alot of the newer full range cabinets just sound mudy and confused to me. Maybe some guys like that??
I find BiAmping to be a very versitale feautre on my Bass Guitar rig as long as drive and cab selection is setup around the same concept. I get much more solid lows with far great power handling and the same is siad for the highs. It all seems to work better when the speaker are kept closer to their natural voicing.
Alot of the newer full range cabinets just sound mudy and confused to me. Maybe some guys like that??
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