If you put two tweeters in the same frequency band, but one of them has a 68uF cap across it to roll off the high end, the cap filter will cause a phase shift relative to the other tweeter, which amounts to a time delay which will vary over frequency. When the two acoustic signals add at your ear, there may be a comb filter effect. the first cancellation will be at the frequency where the time delay is a half wavelength. Another way to look at it is that the signals will cancel when the differential phase shift becomes 180 degrees, and also at all the integral multiples of that frequency. Plus when you're off axis vertically, you'll get comb filter cancellations from the physical displacement differential relative to ear location. Since the second tweeter will have an amplitude rolloff as well, it may not be a big problem. Just something to know about and listen for.
First of all, I would like to say a heartfelt thank you to John and Pano for putting this project together. They were my first build and I have been enjoying these speakers for almost a year now. They have been a revelation and put a smile on my face each time I turn on my stereo. They are quite simply the best speakers I have owned.
I do have a few questions though.
When I went to Solen in Montreal to buy my speakers and cross-over supplies, they had everything on hand except the 5w resistor from the original cross-over list and sold me a 10w resistor. (On it is written Lynk 10w 24RJ).
When I play my speakers, (they are driven by a Cambridge Azur A540 amp) it feels as if that there is something missing in around 200-250Hz. On some recordings it sounds as if whoever is singing is staged 10ft behind the band. Vocals can sound a bit subdued. On other recordings, it is less noticeable.
Could the difference in wattage account for this or is just the woofer and tweeter are doing the best they can and they come up a bit short?
Put another way, If I change the resistor, am I going to fix this dip?
Or can I modify the cross-over in another way to try and boost this range?
Or would I be better off to change to the Vifa driver over the original tweeter and modify the cross-over to suit? (Out of the two versions of the speaker with the Peerless 12in woofer, which is better?)
Thanks in advance.
Andre
I do have a few questions though.
When I went to Solen in Montreal to buy my speakers and cross-over supplies, they had everything on hand except the 5w resistor from the original cross-over list and sold me a 10w resistor. (On it is written Lynk 10w 24RJ).
When I play my speakers, (they are driven by a Cambridge Azur A540 amp) it feels as if that there is something missing in around 200-250Hz. On some recordings it sounds as if whoever is singing is staged 10ft behind the band. Vocals can sound a bit subdued. On other recordings, it is less noticeable.
Could the difference in wattage account for this or is just the woofer and tweeter are doing the best they can and they come up a bit short?
Put another way, If I change the resistor, am I going to fix this dip?
Or can I modify the cross-over in another way to try and boost this range?
Or would I be better off to change to the Vifa driver over the original tweeter and modify the cross-over to suit? (Out of the two versions of the speaker with the Peerless 12in woofer, which is better?)
Thanks in advance.
Andre
Hey Andre - thanks for you post.
I think that going with the Vifa in place of the tweeter is an improvement. Of course, 200-250Hz is the woofer, not the tweeter, so I'm not sure what going on there. I don't think that changing the 5W resistor for a 10W will make much difference at all, unless the 10W is very inductive.
It could be that it's the harmonics of 200-250 that are actually missing in the cross from woofer to tweeter, and your ear mistakes it for the fundamental. That sort of thing has happened to me.
I'll let John take over from here. Hope he gets time as he's busy making his speakers pretty for the trip to LSAF.
I think that going with the Vifa in place of the tweeter is an improvement. Of course, 200-250Hz is the woofer, not the tweeter, so I'm not sure what going on there. I don't think that changing the 5W resistor for a 10W will make much difference at all, unless the 10W is very inductive.
It could be that it's the harmonics of 200-250 that are actually missing in the cross from woofer to tweeter, and your ear mistakes it for the fundamental. That sort of thing has happened to me.
I'll let John take over from here. Hope he gets time as he's busy making his speakers pretty for the trip to LSAF.
Lumpy upper bass lower mid range response patterns
Hello Andre
Thank you for your kind and positive comments. It is gratifying to know you have found the project so enjoyable and worth while.
Concerning your resistor question. I am assuming you are using the Scan Speak 3806 as your mid-tweeter. IIRC, the effective acoustic cross over point is about 1,200 Hz or so with a 2nd order shape.
Pano is correct, a resistor change will have little or no effect relative to the dip you comment on.
There are a couple of things going on and I will try to explain as best I can. And what follows had a lot to do with upgrading the project with the current Vifa driver.
One of the side effects, or should I just say "effects" a relatively narrow Open Baffle (dipole) exhibits are lumpy forward and rear radiation patterns, especially from about 450 Hz down. Adding to that is rear wall frequency and distance dependent reflections. The Manzanita is not a true dipole, it is, with it's shallow wings, a quasi cardioid. Therefore, front and rear radiation patterns are different. The wings help lower the F = value which is a good thing, but you get some cavity and cardioid effects. BTW, fun to measure the differences wing depth and shape can create.
Going to the Vifa has several advantages. The older Manzanita designs employed sealed back H.F. drivers. These drivers, are de-facto monopoles. Forward radiation only. So we have a dipole bass, lower mid range being mated with monopole upper mid range HF. One reason the crossover values are so non traditional. With the Vifa, we have two cardioids, each having a different F = points because of their positions relative to the baffle edge(s). Also the Vifa in the upgraded design reaches more than a full octave lower than the D3806. This is very important. Even with the Vifa rolling off starting around 500 Hz it still contributes all the way down to it's 110 Hz or so resonance. And it's lumpy patterns tends to peak right where the Peerless pattern forms a dips. Wah lah.... a much flatter combined response out 8 to 10 foot in front of the speaker where most listeners sit. I am over simplifying, and the bass and lower mid range patterns are still lumpy, but the 200 Hz suck out is largely filled. Depending on your room size and rear wall distance, you also have another suck out around 70-90 Hz. But that far down, there is enough smearing - room interaction effects that it usually goes unnoticed. Also, as you go down in frequency you lose the ability to locate an exact point source. Up at 200 Hz you can, so you notice a frequency dependent sound stage effect(s). Hope I have not confused the issue! I am obviously not the best at explaining a complex tech issue like this one!
Over all the Vifa version is a better speaker. The Vifa requires a trap to flatten out it's rising response and dampen a peak up around 15Khz. The Vifa with the trap is actually flatter than the D3806, but will not resolve upper mid range detail to the degree the D3608 can.
Hello Andre
Thank you for your kind and positive comments. It is gratifying to know you have found the project so enjoyable and worth while.
Concerning your resistor question. I am assuming you are using the Scan Speak 3806 as your mid-tweeter. IIRC, the effective acoustic cross over point is about 1,200 Hz or so with a 2nd order shape.
Pano is correct, a resistor change will have little or no effect relative to the dip you comment on.
There are a couple of things going on and I will try to explain as best I can. And what follows had a lot to do with upgrading the project with the current Vifa driver.
One of the side effects, or should I just say "effects" a relatively narrow Open Baffle (dipole) exhibits are lumpy forward and rear radiation patterns, especially from about 450 Hz down. Adding to that is rear wall frequency and distance dependent reflections. The Manzanita is not a true dipole, it is, with it's shallow wings, a quasi cardioid. Therefore, front and rear radiation patterns are different. The wings help lower the F = value which is a good thing, but you get some cavity and cardioid effects. BTW, fun to measure the differences wing depth and shape can create.
Going to the Vifa has several advantages. The older Manzanita designs employed sealed back H.F. drivers. These drivers, are de-facto monopoles. Forward radiation only. So we have a dipole bass, lower mid range being mated with monopole upper mid range HF. One reason the crossover values are so non traditional. With the Vifa, we have two cardioids, each having a different F = points because of their positions relative to the baffle edge(s). Also the Vifa in the upgraded design reaches more than a full octave lower than the D3806. This is very important. Even with the Vifa rolling off starting around 500 Hz it still contributes all the way down to it's 110 Hz or so resonance. And it's lumpy patterns tends to peak right where the Peerless pattern forms a dips. Wah lah.... a much flatter combined response out 8 to 10 foot in front of the speaker where most listeners sit. I am over simplifying, and the bass and lower mid range patterns are still lumpy, but the 200 Hz suck out is largely filled. Depending on your room size and rear wall distance, you also have another suck out around 70-90 Hz. But that far down, there is enough smearing - room interaction effects that it usually goes unnoticed. Also, as you go down in frequency you lose the ability to locate an exact point source. Up at 200 Hz you can, so you notice a frequency dependent sound stage effect(s). Hope I have not confused the issue! I am obviously not the best at explaining a complex tech issue like this one!
Over all the Vifa version is a better speaker. The Vifa requires a trap to flatten out it's rising response and dampen a peak up around 15Khz. The Vifa with the trap is actually flatter than the D3806, but will not resolve upper mid range detail to the degree the D3608 can.
For both USA and EU and the rest of the world
This driver : http://www.tymphany.com/files/NE65W-04 Rev 2_0.pdf
It's three time more expensive
John ?
This driver : http://www.tymphany.com/files/NE65W-04 Rev 2_0.pdf
It's three time more expensive
John ?
Man, I'm jealous! I've been considering both of these builds.
How would you compare the Manzanitas with the Plutos? Are the Plutos 2.1?
I like both.
I am not very good a describing how speakers sound and don't comprehend most of the adjectives reviewers use such as bloom and micro dynamics.
The Plutos have more midrange. When you first switch to the Manzanitas from the Plutos, it sounds like there is hole in the midrange. Part of this is from the volume drop when I switch and part, I think, is that there is more bass from the Manzanitas. When the volume is adjusted, the Manzanitas sound well balanced, with lots of detail and a bigger soundstage. A rimshot sounds more like a rimshot, if you know what I mean.
Certian instruments sound a little harsh on the Manzanitas, but not in a negative way. A trumpet is supposed to sound harsh at times. A baroque ensemble with period instruments is supposed to honk at you.
One thing I listen for is how well I can pick out and follow individual voices when a group of people are singing. The edge goes to the Manzanitas. The Vifas are very impressive.
The Plutos have a smaller sweet spot where the imaging and instrument placement stays in focus. The Plutos do not sound good from the couch on the back wall. The Manzanitas sound better, but not great from that position.
The Manzanitas were easier to build, but the Plutos have built in amplifiers.
I also tried to compare the speakers with my Grado headphones. The Grados seemed to be in between the Plutos and the Manzanitas. More punch and bass than the Plutos but smoother than the Manzanitas.
Both are very good speakers. I am sold on open baffle designs, at least in the rooms I have tried them in.
I will say that I am listening to the Manzanitas more than the Plutos. They have a larger soundstage, bass that you can feel and lots of detail. They may not be more "accurate," but in my room, they are more enjoyable.
Next up will be a comparison of the Pluto 2.1s with the Pluto subs (I need another amp to do the test). That should be interesting. I also will experiment with the treble adjustment pot on the Plutos to see if that makes a difference.
John
I am not very good a describing how speakers sound and don't comprehend most of the adjectives reviewers use such as bloom and micro dynamics.
The Plutos have more midrange. When you first switch to the Manzanitas from the Plutos, it sounds like there is hole in the midrange. Part of this is from the volume drop when I switch and part, I think, is that there is more bass from the Manzanitas. When the volume is adjusted, the Manzanitas sound well balanced, with lots of detail and a bigger soundstage. A rimshot sounds more like a rimshot, if you know what I mean.
Certian instruments sound a little harsh on the Manzanitas, but not in a negative way. A trumpet is supposed to sound harsh at times. A baroque ensemble with period instruments is supposed to honk at you.
One thing I listen for is how well I can pick out and follow individual voices when a group of people are singing. The edge goes to the Manzanitas. The Vifas are very impressive.
The Plutos have a smaller sweet spot where the imaging and instrument placement stays in focus. The Plutos do not sound good from the couch on the back wall. The Manzanitas sound better, but not great from that position.
The Manzanitas were easier to build, but the Plutos have built in amplifiers.
I also tried to compare the speakers with my Grado headphones. The Grados seemed to be in between the Plutos and the Manzanitas. More punch and bass than the Plutos but smoother than the Manzanitas.
Both are very good speakers. I am sold on open baffle designs, at least in the rooms I have tried them in.
I will say that I am listening to the Manzanitas more than the Plutos. They have a larger soundstage, bass that you can feel and lots of detail. They may not be more "accurate," but in my room, they are more enjoyable.
Next up will be a comparison of the Pluto 2.1s with the Pluto subs (I need another amp to do the test). That should be interesting. I also will experiment with the treble adjustment pot on the Plutos to see if that makes a difference.
John
Are you sure that your listening placement against the back wall isn't unduly influencing all your listening impressions? Probably the worst possible place to listen to anything.