Crossover Help
I drew a diagram of the crossover circuit from my Zenith Allegro 3000 speakers. For another project, I want to add a midrange speaker to the circuit with the original tweeter and woofer.
Yfrog Image : yfrog.com/5pzenithallegro3000crossoj
How do I do it?
I drew a diagram of the crossover circuit from my Zenith Allegro 3000 speakers. For another project, I want to add a midrange speaker to the circuit with the original tweeter and woofer.
Yfrog Image : yfrog.com/5pzenithallegro3000crossoj
How do I do it?
Do I just bypass the crossover circuit and just feed the input into the midrange?
And let the crossover tend to the woofer and tweater?
And let the crossover tend to the woofer and tweater?
If it gonna work you're a man of great luck ! Sometimes it happens (it happened to me !)
but that would be the time to investigate in the process that brought you to obtain those results.You're the cook in the kitchen ,those are the ingredients...the ears are yours ,too!
but that would be the time to investigate in the process that brought you to obtain those results.You're the cook in the kitchen ,those are the ingredients...the ears are yours ,too!
Since the circuit is parallel, you are adding a bandpass circuit for the mid and adjusting the crossover points of the woofer and the tweeter to coincide with the start and end of the mid's bandpass.
I may not really understand the question, but if you are talking about taking the existing 2-way system and making a 3-way system, the best way to answer your question is: you start over from scratch.
This is pretty much how I started out with speaker building too. Whilst you may be able to get reasonable results (even with off the shelf crossovers) You will NOT even get close to the results you can obtain if you properly design the system from scratch with custom crossovers.
In 1985 I was given a pair of home made Plessy 2 way Loudspeakers with 12" woofers and a 5" widerange "tweeter". They sounded pretty ordinary. I knew very little about crossovers so decided to buy an off the shelf 3 way crossover some polypropylene midranges and some phillips soft dome tweeters, hooked it all up and it was a LOT better. After a while though I decided the midrange was not as good as it should be and bought some Phillips Dome mids, and a much better quality (still off the shelf) three way crossover, this was quite transforming, but the crossover freq for the woofer to mid was inappropriate at 500Hz. Even later still I bought some Vifa M26WR09-08 woofers made a new front baffle and the improvement was quite dramatic sensitivity went down, and I had to add lpads on the mid and tweeters but overall the sound was much nicer. Even before the Vifa's went in I used to get requests to bring the system to every UNI party that was going on, simply because the sound was very clean and played loud enough without distortion that it made everyone elses systems sound really bad.
I was very happy with it. It wasn't until I heard some high end speakers that I realised just how deficient it really was!! Now bear in mind I'd compared to speaker systems sub $1000 at the time and it was better, when I heard a $35,000 speaker system I was devestated... I'm sure if I'd listened to speakers in the range of $2000 to $5000 I'd also have realised the deficiencies.
I've only in the last month or so stopped listening to the above speakers (that's 25 years!!), mainly because my excessively long overdue MTM project is getting closer to completion, and I have something listenable which in most respects (bass excluded) surpasses the old three ways.
Below is a freq response plot comparing the three ways response curve to the new MTM's I tweaked the LPAD's from what I normally have them set to (tune by ear) to what gave the flattest response. The blue curve is for the Old 3 ways. Note the big dip between 2Khz and 5Khz This is I believe is partially due to the Mids not being sensitive enough, though it could also be phase related. It is no wonder voices sound more natural on my new MTM's where the crossover is still being tweaked).
Note that although the response curve does not show it (as it looks flat at 500Hz) The midrange should not be being crossed that low It's resonant peak is at about 350Hz) and the Vifa's are being pushed to their recommended maximum at that freq, so in all they are really a quite inapropriate driver to be used in this system! A nearfield measurement I did some time ago in speaker workshop of the midrange (in order to get a better understanding of what was happening in the three ways) shows why there is that dip between 2khz and 5khz, I suspect that these units have been partially cooked at a party, as they were removed from the speakers after a party because they sounded "wrong" but put back in later because they were actually still better than the cheap polyprops that replaced them.
SO I guess the point I'm trying to make is, that whilst what you are contemplating doing may give you some speakers you are completely happy with (until you hear some truely good ones), it will be a very hit and miss approach leaving a lot up to luck, you may end up spending more time and money, in the quest to get a good sound than you would if you sit down and design everything from scratch.
Selecting the right drivers with good overlap in their usefull range will be a good starting point, but without proper measuring equipment (for freq response and driver impedance) designing a crossover will be VERY difficult if you want to maximise performance.
I can tell you now that the difference between the two off the shelf crossovers I have for the three ways is quite staggering. I think I was lucky with the second lot, whilst no where near perfect (which would be pretty much impossible with this driver combo) they are not TOO bad.
Tony.
In 1985 I was given a pair of home made Plessy 2 way Loudspeakers with 12" woofers and a 5" widerange "tweeter". They sounded pretty ordinary. I knew very little about crossovers so decided to buy an off the shelf 3 way crossover some polypropylene midranges and some phillips soft dome tweeters, hooked it all up and it was a LOT better. After a while though I decided the midrange was not as good as it should be and bought some Phillips Dome mids, and a much better quality (still off the shelf) three way crossover, this was quite transforming, but the crossover freq for the woofer to mid was inappropriate at 500Hz. Even later still I bought some Vifa M26WR09-08 woofers made a new front baffle and the improvement was quite dramatic sensitivity went down, and I had to add lpads on the mid and tweeters but overall the sound was much nicer. Even before the Vifa's went in I used to get requests to bring the system to every UNI party that was going on, simply because the sound was very clean and played loud enough without distortion that it made everyone elses systems sound really bad.
I was very happy with it. It wasn't until I heard some high end speakers that I realised just how deficient it really was!! Now bear in mind I'd compared to speaker systems sub $1000 at the time and it was better, when I heard a $35,000 speaker system I was devestated... I'm sure if I'd listened to speakers in the range of $2000 to $5000 I'd also have realised the deficiencies.
I've only in the last month or so stopped listening to the above speakers (that's 25 years!!), mainly because my excessively long overdue MTM project is getting closer to completion, and I have something listenable which in most respects (bass excluded) surpasses the old three ways.
Below is a freq response plot comparing the three ways response curve to the new MTM's I tweaked the LPAD's from what I normally have them set to (tune by ear) to what gave the flattest response. The blue curve is for the Old 3 ways. Note the big dip between 2Khz and 5Khz This is I believe is partially due to the Mids not being sensitive enough, though it could also be phase related. It is no wonder voices sound more natural on my new MTM's where the crossover is still being tweaked).
Note that although the response curve does not show it (as it looks flat at 500Hz) The midrange should not be being crossed that low It's resonant peak is at about 350Hz) and the Vifa's are being pushed to their recommended maximum at that freq, so in all they are really a quite inapropriate driver to be used in this system! A nearfield measurement I did some time ago in speaker workshop of the midrange (in order to get a better understanding of what was happening in the three ways) shows why there is that dip between 2khz and 5khz, I suspect that these units have been partially cooked at a party, as they were removed from the speakers after a party because they sounded "wrong" but put back in later because they were actually still better than the cheap polyprops that replaced them.
SO I guess the point I'm trying to make is, that whilst what you are contemplating doing may give you some speakers you are completely happy with (until you hear some truely good ones), it will be a very hit and miss approach leaving a lot up to luck, you may end up spending more time and money, in the quest to get a good sound than you would if you sit down and design everything from scratch.
Selecting the right drivers with good overlap in their usefull range will be a good starting point, but without proper measuring equipment (for freq response and driver impedance) designing a crossover will be VERY difficult if you want to maximise performance.
I can tell you now that the difference between the two off the shelf crossovers I have for the three ways is quite staggering. I think I was lucky with the second lot, whilst no where near perfect (which would be pretty much impossible with this driver combo) they are not TOO bad.
Tony.
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Generally mixing drivers with different impedance values is no problem as long as it's used with a properly designed crossover. Without a crossover the speaker impedance can drop below 2R which is dangerous for most power amps but with a well designed crossover may only drop to 3R5 in the lowest dip but still be a 4R nominal speaker.
What is important is to ensure that the power amp is capable of driving the final speaker impedance.
In the graph pic the top one is with a simple 1st order crossover and the bottom is without and shows the very low speaker impedance without a crossover. This is using 8R drivers with a 4R mid driver.
What is important is to ensure that the power amp is capable of driving the final speaker impedance.
In the graph pic the top one is with a simple 1st order crossover and the bottom is without and shows the very low speaker impedance without a crossover. This is using 8R drivers with a 4R mid driver.
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The actual impedance of any loudspeaker tends to vary with frequency. That nominal 8 ohm driver may reach a minimum of 6 ohms and rise to 50 ohms as the inductance rises.
Rob Elliot has a fairly comprehensive article on passive crossover design.
Passive Crossover Network Design
As long as your amplifier is robust enough to drive the 4 ohm load, the design process for your crossover is not likely to be any more difficult, and time consuming than if all the drivers were of the same nominal impedance.😉
Rob Elliot has a fairly comprehensive article on passive crossover design.
Passive Crossover Network Design
As long as your amplifier is robust enough to drive the 4 ohm load, the design process for your crossover is not likely to be any more difficult, and time consuming than if all the drivers were of the same nominal impedance.😉
OK I took some pictures with my digital camera:
*The left speaker is the original crappy 8" woofer from the cabinet I'm using.
On the right is the Allegro 10" woofer.
Imageshack - im000008c.jpg
*The original Allegro horn tweater I'm going to use.
Imageshack - im000007.jpg
*The nice computer woofers I'm going to use as new midranges
Imageshack - im000006f.jpg
*Better shot of the Allegra woofer
Imageshack - im000004.jpg
*The new Audiospere cabinet with the junky drivers removed and the main woofer hole enlarged with a jigsaw for the new 10" woofer. Its my first use of my new jigsaw I bought that morning.
Pretty good cut for a first timer, yes? The screw holes aren't drilled yet. The Allegro had some steel clips that I will reuse that hold the woofer in.
Imageshack - im000002d.jpg
*The left speaker is the original crappy 8" woofer from the cabinet I'm using.
On the right is the Allegro 10" woofer.
Imageshack - im000008c.jpg
*The original Allegro horn tweater I'm going to use.
Imageshack - im000007.jpg
*The nice computer woofers I'm going to use as new midranges
Imageshack - im000006f.jpg
*Better shot of the Allegra woofer
Imageshack - im000004.jpg
*The new Audiospere cabinet with the junky drivers removed and the main woofer hole enlarged with a jigsaw for the new 10" woofer. Its my first use of my new jigsaw I bought that morning.
Pretty good cut for a first timer, yes? The screw holes aren't drilled yet. The Allegro had some steel clips that I will reuse that hold the woofer in.
Imageshack - im000002d.jpg
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