I’m sure all DIY speaker builders are familiar with the concept, “the (passive) crossover makes or breaks your DIY speaker.” I’ve always wondered, why even use a passive crossover at all? Why not go active?
A little background:
I had an interesting experience with my speakers a few years ago, a somewhat unique two-way design from the now-defunct Genesis Physics brand. The tweeter has a huge magnet which allows it to run a very low crossover point of about 1200Hz. However, it wasn’t hard high-level, sustained use to burn out the tweeters, and after blowing a couple they gave me a diagram showing how to raise the crossover point to 1800Hz.
Well, immediately I noticed that more than the crossover frequency had changed. The bass sounded different – a little tighter, and the tweeter sounded a little shrill. I eventually traced that problem to a 3-4dB spike centered at about 6kHz.
Another thing: Years earlier I came across a white paper from Harrison Labs (the company that makes those “F-Mod” in-line filters) that said if you took a passive three-way speaker system that was being powered at about 200 watts and switched it to active, you could get the same output levels with a trio of 25-watt amps! Yup – a total of 75 watts active would perform like 200 watts passive!
These two things were enough to convince me that passive crossovers are basically so much crap: They suck out amplifier power and audibly change the sonic characteristics of a driver.
You can see the difference an active system makes at this on-going thread at the Home Theater Talk Forum. The originator of the thread is experimenting with modifying an Adire speaker kit to active, and reports the improvements:
Sure, the cost of hardware is a factor, but all the money saved by going the DIY route would cover most of that outlay. So that shouldn’t even be a concern. Why not just bite the bullet and go all the way? It only makes sense, if the desire is to get the best performance for the money. As we’re already seen, you don’t need expensive high-powered amps; new or (even better) used high-quality, low-powered amps sell pretty cheap. Note that the DIYer from the HTT thread is only using an Audio Source amp, not exactly the vanguard for top-flight fidelity.
Once you have the hardware, you can use it forever with any future DIY speaker venture you might want to undertake. Each new project would be virtually “plug and play” – just change the crossover frequency as needed. No endless futzing around trying to come up with an all-new passive crossover design.
So let’s hear it, all you DIY speaker builders. Why do you choose to mess around with bogus passive crossovers when you could go active and leave all that behind?
Regards,
Wayne A. Pflughaupt
A little background:
I had an interesting experience with my speakers a few years ago, a somewhat unique two-way design from the now-defunct Genesis Physics brand. The tweeter has a huge magnet which allows it to run a very low crossover point of about 1200Hz. However, it wasn’t hard high-level, sustained use to burn out the tweeters, and after blowing a couple they gave me a diagram showing how to raise the crossover point to 1800Hz.
Well, immediately I noticed that more than the crossover frequency had changed. The bass sounded different – a little tighter, and the tweeter sounded a little shrill. I eventually traced that problem to a 3-4dB spike centered at about 6kHz.
Another thing: Years earlier I came across a white paper from Harrison Labs (the company that makes those “F-Mod” in-line filters) that said if you took a passive three-way speaker system that was being powered at about 200 watts and switched it to active, you could get the same output levels with a trio of 25-watt amps! Yup – a total of 75 watts active would perform like 200 watts passive!
These two things were enough to convince me that passive crossovers are basically so much crap: They suck out amplifier power and audibly change the sonic characteristics of a driver.
You can see the difference an active system makes at this on-going thread at the Home Theater Talk Forum. The originator of the thread is experimenting with modifying an Adire speaker kit to active, and reports the improvements:
- “My friend just came over and we watched the "Brain Damage + Eclipse" music. The MPEG compressed music... was apparently clearer and more open than [with] the regular Kit281 in the next room hooked to my nice CD player and amplifier. I'm starting to become more convinced that the active approach itself is responsible for gains in sound quality that don't have to do with frequency response.”
- “...even considering the slight difference in the crossover, the active speaker still has the basic tone [compared to the un-modified one]... of the other one. It's still a Kit281, just better. It has clearer treble and smoother midrange. The disadvantage is this smoother midrange pushes certain singer's high notes back from a prominence in the soundstage. I appreciate the more pleasant sound and lower distortion, but it's a little less "unrestrained" and I'm going to try and correct it towards more upper midrange excitement, despite maybe a little harshness. It's a defect I don't mind living with.”
- “Each range of sounds is improved in some way. The bass has more "punch" and transparency, the midrange seems smoother (though it still has some of the characteristic AV8 coloration) and the treble is way clearer. In general the speakers maintain the same unrestrained quality I liked so much, but are less distorted sounding than before.”
Sure, the cost of hardware is a factor, but all the money saved by going the DIY route would cover most of that outlay. So that shouldn’t even be a concern. Why not just bite the bullet and go all the way? It only makes sense, if the desire is to get the best performance for the money. As we’re already seen, you don’t need expensive high-powered amps; new or (even better) used high-quality, low-powered amps sell pretty cheap. Note that the DIYer from the HTT thread is only using an Audio Source amp, not exactly the vanguard for top-flight fidelity.
Once you have the hardware, you can use it forever with any future DIY speaker venture you might want to undertake. Each new project would be virtually “plug and play” – just change the crossover frequency as needed. No endless futzing around trying to come up with an all-new passive crossover design.
So let’s hear it, all you DIY speaker builders. Why do you choose to mess around with bogus passive crossovers when you could go active and leave all that behind?
Regards,
Wayne A. Pflughaupt