I would like to try switching over to an active crossover. My speakers are nothing particularly special at the moment, Polk RT55 speakers with a Polk PSW12 powered subwoofer. I may get better speakers at some point in the future, but these are good. I recently heard them used with a very fancy biamped setup and they sounded much, much better, so I am going to try going this route.
So the first thing I need is a crossover. It will take some balls to cut the wiring for the passive crossovers in the speakers, but no big. Because of the subwoofer, I believe I want a 3-way stereo crossover. Sub crossing over to mids should be about 100 hz, and mids to tweeters in the RT55s are, I think, set up by the Polk factory at 2.5khz.
I've researched crossovers and the Marchand XM9-3AA would work, although it's quite expensive and changing crossover points entails opening the unit and inserting new circuit cards. Not the end of the world, but I'm wondering if I could just us a less costly pro-/DJ-oriented unit such as a DBX 234s. Obviously you need 1/4"-to-RCA adapters, but that's easy. That unit allows you to change the crossover points right from the front. Is there any reason why it would be a poor choice? ... would it not perform up to the level of a Marchand, and if so in what way? What might prove a better choice?
Many thanks for any advice.
So the first thing I need is a crossover. It will take some balls to cut the wiring for the passive crossovers in the speakers, but no big. Because of the subwoofer, I believe I want a 3-way stereo crossover. Sub crossing over to mids should be about 100 hz, and mids to tweeters in the RT55s are, I think, set up by the Polk factory at 2.5khz.
I've researched crossovers and the Marchand XM9-3AA would work, although it's quite expensive and changing crossover points entails opening the unit and inserting new circuit cards. Not the end of the world, but I'm wondering if I could just us a less costly pro-/DJ-oriented unit such as a DBX 234s. Obviously you need 1/4"-to-RCA adapters, but that's easy. That unit allows you to change the crossover points right from the front. Is there any reason why it would be a poor choice? ... would it not perform up to the level of a Marchand, and if so in what way? What might prove a better choice?
Many thanks for any advice.
No replies yet, so I'll give it a shot.
There are some major advantages to using active crossovers, but there is also a lot of complexity to convert a speaker designed and built for passive xovers to use of actives.
Most passive xovers in commercial speakers, and many in DIY designs, are not a straightforward transfer function. They usually invlolve some other frequency adjusting circuitry. Some of it can be eliminated when switching to active; some of it can't. So be advised that simply unplugging the existing passives and installing an active might not yield better overall results.
First of all, don't cut any wires, and don't throw anything away, and don't change anything that you won't be able to change back if the actives don't work out.
Secondly, you need more information about the passive xover than just its frequency. Do you know the slope? Is there any other kind of equalization in the passive xover, such as baffle step compensation?
Don't spend a lot of money on a fancy active xover. Marchand makes excellent products, but I guarantee that you will not get this right on the first try. It's just not that simple. Buy the cheapest active you can find. Those DBX 234's are okay for experimenting, but they sound like crap. I owned one. I hated it. There are no better cheap ones, so you must accept poor fidelity initially. Mini-DSP (if you don't know what that means, find out NOW) is probably a better choice to begin with, as slopes and xover points are flexible. The DBX uses LR4 (if you don't know what that means, find out NOW) fixed slopes, which work for many speakers but not for all.
Do you have another amp? You need two if you're using a two way active xover, three amps if you're doing 3-way. I recommend starting between woofer and midrange, leaving the tweeter passive.
These are some of the challenges. It can be very rewarding to make the switch, but it can also be a disaster. Not trying to scare you off, but it seems that you need to learn a lot more about crossovers before taking the plunge.
Peace,
Tom E
There are some major advantages to using active crossovers, but there is also a lot of complexity to convert a speaker designed and built for passive xovers to use of actives.
Most passive xovers in commercial speakers, and many in DIY designs, are not a straightforward transfer function. They usually invlolve some other frequency adjusting circuitry. Some of it can be eliminated when switching to active; some of it can't. So be advised that simply unplugging the existing passives and installing an active might not yield better overall results.
First of all, don't cut any wires, and don't throw anything away, and don't change anything that you won't be able to change back if the actives don't work out.
Secondly, you need more information about the passive xover than just its frequency. Do you know the slope? Is there any other kind of equalization in the passive xover, such as baffle step compensation?
Don't spend a lot of money on a fancy active xover. Marchand makes excellent products, but I guarantee that you will not get this right on the first try. It's just not that simple. Buy the cheapest active you can find. Those DBX 234's are okay for experimenting, but they sound like crap. I owned one. I hated it. There are no better cheap ones, so you must accept poor fidelity initially. Mini-DSP (if you don't know what that means, find out NOW) is probably a better choice to begin with, as slopes and xover points are flexible. The DBX uses LR4 (if you don't know what that means, find out NOW) fixed slopes, which work for many speakers but not for all.
Do you have another amp? You need two if you're using a two way active xover, three amps if you're doing 3-way. I recommend starting between woofer and midrange, leaving the tweeter passive.
These are some of the challenges. It can be very rewarding to make the switch, but it can also be a disaster. Not trying to scare you off, but it seems that you need to learn a lot more about crossovers before taking the plunge.
Peace,
Tom E
The above is good advice. I would suggest a lot of reading before doing anything to the passive crossovers.
Also note that going active has certain advantages, but fundamentally, passive can be just as good as active. Active wins in certain areas like crossing to a sub, where crossover components become large and sometimes, cost prohibitive. But a passive crossover for the tweeter is going to be just fine, and in fact, has the advantage of protecting the tweeter from DC.
Also note that going active has certain advantages, but fundamentally, passive can be just as good as active. Active wins in certain areas like crossing to a sub, where crossover components become large and sometimes, cost prohibitive. But a passive crossover for the tweeter is going to be just fine, and in fact, has the advantage of protecting the tweeter from DC.
Linkwitz states..
I have a strong preference for line level active dividing networks ahead of the power amplifiers (Ref. 2, 12, 17). In this approach the power amplifier output is connected directly - except for a very low resistance speaker cable - to the voice coil of the driver. The amplifier takes maximum control over the motion of the speaker cone which gives a greater sense of clarity and dynamism compared to a passive dividing network between amplifier and driver. Active crossovers make much more effective use of amplifier power. A clipping woofer amplifier is not seen by the tweeter, which has its own amplifier. The clipping of the woofer amplifier may not even be noticed in this case. It would surely be heard with a passive crossover, where it might even overheat and damage the tweeter, because of the large amount of high frequency energy in the clipped signal.
Crossover filters for a speaker usually incorporate frequency response corrections for the individual drivers to obtain a desired overall response. The active network has the advantage of correcting easily for different sensitivities of drivers and equalizing not only the individual drivers but the combined response as well. Not having to deal with the interaction between driver impedance and passive filter network gives the designer of an active crossover/equalizer much greater freedom and control to develop a superior product.
The best crossovers ...
The best electrical crossover filter is one that maintains the acoustic polar response of a loudspeaker throughout the crossover frequency range as output shifts from one driver to the next. The sum of acoustic lowpass and highpass outputs must have allpass behavior without high Q peaks in the group delay. The highpass filter section must attenuate out-of-band driver terminal voltages at a sufficiently high rate so that cone excursion decreases with decreasing frequency and nonlinear distortion is minimized.
The crossover must be inaudible
The crossover must be inaudible on program material. This also implies that the power response of the two drivers must be similar in the crossover region, and that requires special attention during the loudspeaker's concept and design phases.
Crossovers may be implemented either as passive RLC networks, as active filters with operational amplifier circuits or with DSP engines and software. The only excuse for passive crossovers is their low cost. Their behavior changes with the signal level dependent dynamics of the drivers. They block the power amplifier from taking maximum control over the voice coil motion. They are a waste of time, if accuracy of reproduction is the goal.
Accurate Stereo performance tests SL - October 2009
I have a strong preference for line level active dividing networks ahead of the power amplifiers (Ref. 2, 12, 17). In this approach the power amplifier output is connected directly - except for a very low resistance speaker cable - to the voice coil of the driver. The amplifier takes maximum control over the motion of the speaker cone which gives a greater sense of clarity and dynamism compared to a passive dividing network between amplifier and driver. Active crossovers make much more effective use of amplifier power. A clipping woofer amplifier is not seen by the tweeter, which has its own amplifier. The clipping of the woofer amplifier may not even be noticed in this case. It would surely be heard with a passive crossover, where it might even overheat and damage the tweeter, because of the large amount of high frequency energy in the clipped signal.
Crossover filters for a speaker usually incorporate frequency response corrections for the individual drivers to obtain a desired overall response. The active network has the advantage of correcting easily for different sensitivities of drivers and equalizing not only the individual drivers but the combined response as well. Not having to deal with the interaction between driver impedance and passive filter network gives the designer of an active crossover/equalizer much greater freedom and control to develop a superior product.
The best crossovers ...
The best electrical crossover filter is one that maintains the acoustic polar response of a loudspeaker throughout the crossover frequency range as output shifts from one driver to the next. The sum of acoustic lowpass and highpass outputs must have allpass behavior without high Q peaks in the group delay. The highpass filter section must attenuate out-of-band driver terminal voltages at a sufficiently high rate so that cone excursion decreases with decreasing frequency and nonlinear distortion is minimized.
The crossover must be inaudible
The crossover must be inaudible on program material. This also implies that the power response of the two drivers must be similar in the crossover region, and that requires special attention during the loudspeaker's concept and design phases.
Crossovers may be implemented either as passive RLC networks, as active filters with operational amplifier circuits or with DSP engines and software. The only excuse for passive crossovers is their low cost. Their behavior changes with the signal level dependent dynamics of the drivers. They block the power amplifier from taking maximum control over the voice coil motion. They are a waste of time, if accuracy of reproduction is the goal.
Accurate Stereo performance tests SL - October 2009
Last edited:
Hi,
Whilst the above is true, its a truism, proper active x/o's done properly.
its not easy to do it properly, and if you can its not necessarily cost
effective, e.g. an expensive stereo power amplifier for tweeters
compared to active active biamping for bass to mid/treble and
a passive x/o for mid/treble.
For most two ways active is a waste of money unless you have
a nice dinky little treble amplifier to use with the main amplifier.
rgds, sreten.
Whilst the above is true, its a truism, proper active x/o's done properly.
its not easy to do it properly, and if you can its not necessarily cost
effective, e.g. an expensive stereo power amplifier for tweeters
compared to active active biamping for bass to mid/treble and
a passive x/o for mid/treble.
For most two ways active is a waste of money unless you have
a nice dinky little treble amplifier to use with the main amplifier.
rgds, sreten.
I doubt the original poster can interpret all that techno mumbo jumbo. I admire Linkwitz, but he's not for the novice. He also happens to sell plans and parts to build active crossovers, so he's hardly impartial.
Here is some simple advice: Polk makes pretty nice speakers for the mainstream consumer such as you. Active crossovers are not a simple way to improve the quality of sound, and they're not for mainstream consumers. They can be complex and expensive and difficult to implement properly. There is no suitably cheap or simple solution, no magic bullet. And then you need amps.
Passive crossovers are not poison, and definitely not a "waste of time". The vast majority of speakers use them, and some are quite stunning. If you are really interested in improving your existing speakers and willing to learn a few things about how they make good or bad sound, read some of the forums about crossovers and parts quality, especially capacitors. You can probably improve the sound of your speakers by merely substituting better quality parts in the existing passive crossovers. It's not difficult, not complicated, can be as cheap or expensive as you want to make it, and can pay modest to considerable dividends in better sound.
Most speaker manufacturers, even Polk, make compromises in the quality of components they use in their crossovers because few people ever see them and don't know or care that better parts might sound better.
Peace,
Tom E
Here is some simple advice: Polk makes pretty nice speakers for the mainstream consumer such as you. Active crossovers are not a simple way to improve the quality of sound, and they're not for mainstream consumers. They can be complex and expensive and difficult to implement properly. There is no suitably cheap or simple solution, no magic bullet. And then you need amps.
Passive crossovers are not poison, and definitely not a "waste of time". The vast majority of speakers use them, and some are quite stunning. If you are really interested in improving your existing speakers and willing to learn a few things about how they make good or bad sound, read some of the forums about crossovers and parts quality, especially capacitors. You can probably improve the sound of your speakers by merely substituting better quality parts in the existing passive crossovers. It's not difficult, not complicated, can be as cheap or expensive as you want to make it, and can pay modest to considerable dividends in better sound.
Most speaker manufacturers, even Polk, make compromises in the quality of components they use in their crossovers because few people ever see them and don't know or care that better parts might sound better.
Peace,
Tom E
I cannot recommend this to beginners.
If the speaker designer has done his job properly then he will have "tuned" the passive crossover components to take account of the parasitics in the components used.
Swap to a component with different parasitics and the beginner ends up with an "untuned" speaker. He should then adjust some or all of the other components and maybe introduce new or additional components to bring the passive speaker back to spec. Then you might get better sound or you might not. It will certainly be different.
As far as Polk is concerned, they do an amazing job with their passive crossovers. There really isn't much left to improve upon. Amazing value at any price point..
http://www.stereophile.com/content/polk-audio-rtiii-a3-loudspeaker
http://www.stereophile.com/content/polk-audio-rtiii-a3-loudspeaker
Last edited:
foodchain,
As the fellas have alluded to, it's not quite straightforward to "switch to an active crossover" with an existing set of speakers. Passive crossovers usually perform a lot of shaping, non-textbook filtering, etc, etc, to achieve the final design.
Generic, active crossovers will most likely have completely different electrical responses than the crossoovers now inside your RT55's. That may be a good thing or it may be a bad thing.
Anyways, you mentioned "I recently heard them used with a very fancy biamped setup and they sounded much, much better." What are the details of that setup? Can you copy it? Did the person who implemented it know what he was doing?
Cheers,
Dave.
As the fellas have alluded to, it's not quite straightforward to "switch to an active crossover" with an existing set of speakers. Passive crossovers usually perform a lot of shaping, non-textbook filtering, etc, etc, to achieve the final design.
Generic, active crossovers will most likely have completely different electrical responses than the crossoovers now inside your RT55's. That may be a good thing or it may be a bad thing.
Anyways, you mentioned "I recently heard them used with a very fancy biamped setup and they sounded much, much better." What are the details of that setup? Can you copy it? Did the person who implemented it know what he was doing?
Cheers,
Dave.
The best situation for actives is when you know exactly what the raw, Psuedo-anechoic driver responses are, like those on the Zaph site.
I also get the feeling that you might be confusing the terms "bi-amped" with active. They are basically two different things..
Last edited:
@foodchain11
As an experiment I 'activated' some two way Mission 702e speakers but made sure I could restore them back to original condition if necessary. The mod involved removing a couple of caps and soldering in a couple of wires. I also fitted a couple of protection caps in series with the tweeters on the existing crossover PCB. (Don't tell anyone but they were 100uF non-polarised electrolytics which cost about $1 each).
Despite the pessimistic comments here, I found it very straightforward to get straight to an amazing sound using PC-based digital filtering and a couple of secondhand Japanese amps. It is strikingly better than the original passive crossovers.
Using digital filtering, you can have linear phase and precisely complementary high and low pass, plus the option to tweak the response to your heart's content, and even incorporate room correction 'for free'. My software was homebrew, but I know there's quite a bit of freeware (and commercial stuff) out there. It's by far the most effective (and cheap) bit of DIY audio I've ever done.
As an experiment I 'activated' some two way Mission 702e speakers but made sure I could restore them back to original condition if necessary. The mod involved removing a couple of caps and soldering in a couple of wires. I also fitted a couple of protection caps in series with the tweeters on the existing crossover PCB. (Don't tell anyone but they were 100uF non-polarised electrolytics which cost about $1 each).
Despite the pessimistic comments here, I found it very straightforward to get straight to an amazing sound using PC-based digital filtering and a couple of secondhand Japanese amps. It is strikingly better than the original passive crossovers.
Using digital filtering, you can have linear phase and precisely complementary high and low pass, plus the option to tweak the response to your heart's content, and even incorporate room correction 'for free'. My software was homebrew, but I know there's quite a bit of freeware (and commercial stuff) out there. It's by far the most effective (and cheap) bit of DIY audio I've ever done.
Hi foodchain11. I am by no means an expert but had a thought about the path you are considering. I had an older pair of Polk Monitor 5s and an even older Polk LF-14 passive sub. While yours are newer and may be more complex, the crossovers in my speakers were a straightforward parallel, second order with no special tricks. No notch filters, no eq… just coils, caps, a resistor and a tweeter protection device. No problem substituting active processes for the passive ones here. This could be determined pretty quickly by inspection of yours. In my first setup, I left the 5s intact but biamped, using two old Yamaha power amps (actually the lf amp was an integrated!) and (this will likely bring big laughs from the other posters but…) a resurrected car audio crossover with a 12V walwart. Turned out great! I could dial in the Monitor 5s / sub combo to sound a lot more like I wanted. Xover point was 60Hz. This junkyard arrangement sounded so much better to me that I trotted off to speaker setup and room treatment games for quite a while. I had this stuff in boxes from my golden days so I just threw it together and wound up having a lot of fun playing with it while I worked on the grander plan. I also found out that the lesser perfect implementations can be fun to play with and am happy to have experimented at this level first. I would leave the RT55s like they are and get the speaker/sub division done. IMO that alone will be rewarding and fun to tweak. While there are lots of viable solutions, I think the MiniDSP and PC crossover options (for the reasons CopperTop gave) are worth considering. ...or play cheap at first and throw $10 at an old car audio one?
Why don't you just bi-amp the speakers. I did it to my speakers and it made a big difference.
If your speakers are not already bi-wire able/bi-amp able then you need to either cut the tracks or reposition the crossover components. I made a new pcb using some existing parts and some newer ones. Capacitors were changed to better types ( same as old value) and coils were made air core types. That alone made a lot of difference.
You then need to connect the terminals to a bi-wire able socket available from many sources. Maybe you should just bi-wire the unit first and check for differences.
Bi-amping is more expensive but is another change that might improve things enough for sometime. The speakers generally sound cleaner and can go much louder without any strain.
Going active after this could be done later if you really want to .As everyone cautions you , the actual slopes may not match with active commercial implementations. You might need to measure the electrical response at the driver terminals to find out what the active crossover has to do. Might mean rigging up your own circuit to match it.
Take small steps at a time . It will involve less effort at a particular time and you can see how the different changes effect the sound. You can also easily go back to the previous configuration if you are not satisfied.
Cheers.
If your speakers are not already bi-wire able/bi-amp able then you need to either cut the tracks or reposition the crossover components. I made a new pcb using some existing parts and some newer ones. Capacitors were changed to better types ( same as old value) and coils were made air core types. That alone made a lot of difference.
You then need to connect the terminals to a bi-wire able socket available from many sources. Maybe you should just bi-wire the unit first and check for differences.
Bi-amping is more expensive but is another change that might improve things enough for sometime. The speakers generally sound cleaner and can go much louder without any strain.
Going active after this could be done later if you really want to .As everyone cautions you , the actual slopes may not match with active commercial implementations. You might need to measure the electrical response at the driver terminals to find out what the active crossover has to do. Might mean rigging up your own circuit to match it.
Take small steps at a time . It will involve less effort at a particular time and you can see how the different changes effect the sound. You can also easily go back to the previous configuration if you are not satisfied.
Cheers.
Rubbish the previous post. I couldn't edit it as the Net connection was lost for too long.
Here is what I wanted to edit it to.
Looks like the RT55 is already bi-wireable.Why don't you just bi-wire it and see how it sounds. Also have a look at the crossover and see if you can upgrade the parts. Better caps and air core coils.
Bi-amping will bring more improvements. The speaker will sound cleaner and go louder effortlessly. Test everything without the sub so that you know what's happening to the main speakers.
You should be able to crossover below 100Hz to the sub. If your main speaker is ducted , you could seal the duct . Measure the Qtc and build an ideal 2nd order active crossover to get a 4th order LR response. You can match that with the sub also.
Cheers.
Here is what I wanted to edit it to.
Looks like the RT55 is already bi-wireable.Why don't you just bi-wire it and see how it sounds. Also have a look at the crossover and see if you can upgrade the parts. Better caps and air core coils.
Bi-amping will bring more improvements. The speaker will sound cleaner and go louder effortlessly. Test everything without the sub so that you know what's happening to the main speakers.
You should be able to crossover below 100Hz to the sub. If your main speaker is ducted , you could seal the duct . Measure the Qtc and build an ideal 2nd order active crossover to get a 4th order LR response. You can match that with the sub also.
Cheers.
I find that bi-amping makes a difference.
The speaker that responded most to this was the Tannoy Berkley.
It was not bi-wireable. I had to go in and alter the crossover PCB slightly. Drilled a couple of tracks and cut another. Brought the extra wire out to the new 4 terminal board.
The change was night and day. The combination of bi-wireabale and bi-amping created a new sound environment that was so good in comparison to what was before that I did not change my system for about 6years, even though I was still going around the good retailers listening to good equipment and "wanting" to spend some money. There was nothing in my price range that I thought could compete.
I will certainly admit that other speakers have not reacted as much, but then I do have some quite good amplifiers. But all sound better when bi-amped, (not active).
The speaker that responded most to this was the Tannoy Berkley.
It was not bi-wireable. I had to go in and alter the crossover PCB slightly. Drilled a couple of tracks and cut another. Brought the extra wire out to the new 4 terminal board.
The change was night and day. The combination of bi-wireabale and bi-amping created a new sound environment that was so good in comparison to what was before that I did not change my system for about 6years, even though I was still going around the good retailers listening to good equipment and "wanting" to spend some money. There was nothing in my price range that I thought could compete.
I will certainly admit that other speakers have not reacted as much, but then I do have some quite good amplifiers. But all sound better when bi-amped, (not active).
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.