I had a set of these about 20 years ago. They are nice tweeters but I found problems crossing them low enough to match anything but a small woofer. Otherwise the system's directivity would narrow below the crossover and present harshness from the treble.
Allen,
Again thanks for your insight. I'm a speaker building amateur, but isn't the resonant frequency 1700hz. If I cross them at 3500hz wouldn't they work? I pretty sure the Altec woofer can handle it, because they came out with a Series II version of the same speaker and changed the cabinet volume by about +130 cu in and raised the xover from 3khz to 3.5 khz. Wouldn't your 3.3uf cap recommendation earlier work?
Again thanks for your insight. I'm a speaker building amateur, but isn't the resonant frequency 1700hz. If I cross them at 3500hz wouldn't they work? I pretty sure the Altec woofer can handle it, because they came out with a Series II version of the same speaker and changed the cabinet volume by about +130 cu in and raised the xover from 3khz to 3.5 khz. Wouldn't your 3.3uf cap recommendation earlier work?
Jantzen, Dayton Audio, and many others. The brand isn't as important as the type -
Film and Foil Capacitors -
Film and Foil Capacitors in the Speaker Components Department at Parts Express | 295
Metalized Polypropylene -
Metalized Polypropylene Capacitors in the Speaker Components Department at Parts Express | 294
Here is a Dayton Audio 6.2uF for $2.83 -
Dayton Audio DMPC-6.2 6.2uF 250V Polypropylene Capacitor 027-427
And a Dayton 2uF for $1.48 -
Dayton Audio DMPC-2.0 2.0uF 250V Polypropylene Capacitor 027-414
The thing you probably do NOT want is the Non-Polarized Electrolytic -
2.2uF 100V Non-Polarized Capacitor 027-324
For the slight difference in price, there is simply no point in buying the Non-Polar Electrolytic.
Steve/bluewizard
As someone mentioned you have to measure the impedance at the crossover point. Is there an impedance curve for the tweeter you want to use? It sounds like you are hearing the classic problem of a 1st order network namely that whenever the two speakers are reproducing the same frequency at roughly the same levels, there will be interference between them, reinforcing some frequencies or cancelling others.
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There are some things to keep in mind when running a woofer at high frequencies which have small wavelengths compared with the size of the cone. The woofer will produce more sound to the front of the speaker, ie less to the sides. These may sound OK when you sit closer but in a room, you tend to hear all the sound because it eventually bounces around the room and comes back to you. So, if you get the higher woofer frequencies to sound right from the front, they can be less strong in the bigger picture.
If you then cross to a tweeter which has wide dispersion and make it sound good from the front, the treble may sound too heavy in the room and the region of frequencies below the crossover where the woofer is running out may expose a harshness in the treble which is otherwise undeserved (ie no other reason it should be a problem).
One option is to keep the 8" crossed perhaps lower than 2k. You could also use a tweeter with more narrow dispersion and then you might cross the woofer higher (not too high). Such tweeters might be a larger coned tweeter or perhaps one that is waveguided.
Some of this is generalising, of course. You may like the tweeter. If I had some still I'd probably put them into something.
The reason a simple crossover (ie one capacitor total) may work is that the tweeter will be producing more energy at its resonance, which is below the crossover and this might happen to fill in a little for the woofer at its top end.
Since a small capacitor is used to compensate somewhat for the resonance peaking, the tweeter response just above this is normally slightly low. The woofer may tend to have some peaking at its most upper region (called breakup) just above the crossover which may fill in this second hole.
When you use a second order filter (preferrably around an octave or more higher than the tweeter resonance but still maybe lower than for first order) the peaking is not as profound. There is a certain immunity to it compared with the capacitor on its own and the response should be closer to what it ought to be.
When you use a second order on the tweeter you might use one order on the woofer to help keep them in line
Since a small capacitor is used to compensate somewhat for the resonance peaking, the tweeter response just above this is normally slightly low. The woofer may tend to have some peaking at its most upper region (called breakup) just above the crossover which may fill in this second hole.
When you use a second order filter (preferrably around an octave or more higher than the tweeter resonance but still maybe lower than for first order) the peaking is not as profound. There is a certain immunity to it compared with the capacitor on its own and the response should be closer to what it ought to be.
When you use a second order on the tweeter you might use one order on the woofer to help keep them in line
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Allen, this makes sense and keeps it into perspective.
If I go the route of the Vifa d19, which is a drop in w/o cabinet modification, I should consider at least a 2nd order xover. It might be surprisingly good. There is no way for me to do any impedance measuring so it will be hit or miss w/ an online calculator.
Vifa D19TD-05 3/4" Poly Dome Tweeter 264-500
Or maybe just purchase a phenolic ring tweeter, which I've read is a slight improvement of stock cone tweeters w/o any crossover mod other than a new poly cap.
Phenolic Ring Tweeter 8 Ohm 270-252
What you say?
If I go the route of the Vifa d19, which is a drop in w/o cabinet modification, I should consider at least a 2nd order xover. It might be surprisingly good. There is no way for me to do any impedance measuring so it will be hit or miss w/ an online calculator.
Vifa D19TD-05 3/4" Poly Dome Tweeter 264-500
Or maybe just purchase a phenolic ring tweeter, which I've read is a slight improvement of stock cone tweeters w/o any crossover mod other than a new poly cap.
Phenolic Ring Tweeter 8 Ohm 270-252
What you say?
The D19 tweeter if I remember correctly gave a slightly relaxed performance when used without equalising and larger cone tweeters sometimes do the same. This is probably only of interest if you plan to use a straightforward crossover. I probably used it down to 3kHz and I did use it first order sometimes but second fitted better with what I was doing and allowed a lower cross point. I also appreciate a good cone tweeter or small full range driver for what it's worth. Steve (System7) has previously recommended this one.
With a second order filter, the capacitor and inductor have a shared control that gives the impression of partially ignoring the impedance. If you are not doing measurements it can become a sensible choice for this reason.
If you do decide to cross the woofer you should probably use impedance rise compensation with the inductor as shown below if you aren't going to use measurements. The values should be easy enough to work out.
With a second order filter, the capacitor and inductor have a shared control that gives the impression of partially ignoring the impedance. If you are not doing measurements it can become a sensible choice for this reason.
If you do decide to cross the woofer you should probably use impedance rise compensation with the inductor as shown below if you aren't going to use measurements. The values should be easy enough to work out.
Attachments
If you don't mind paying a bit more, the Vifa XT25TG30 is a better choice. You can go 1st order (Red trace below) with this tweeter. More information can be found at SWIFT-IIIb.
An externally hosted image should be here but it was not working when we last tested it.
The XT25 can easily be crossed at 2.5kHz with 2nd order. All in, it's more flexible. The D19 on the other hand, is more suitable for 2nd order at 3kHz to 3.5kHz.
By the way, 8" with a dome is quite difficult. I usually use a compression driver but it's costly and complicated.
I am using the Accuton 3/4" diamond tweeter.
Every sim I did used a higher value cap, 3.6 etc., plus an inductor for a second order crossover.
After finding ALL the x-overs left a distorted sound in the tweeter, I started from scratch.
Final 1st order crossover, 1.5uF. 2.0uF sounds about right.
The lunatic
Every sim I did used a higher value cap, 3.6 etc., plus an inductor for a second order crossover.
After finding ALL the x-overs left a distorted sound in the tweeter, I started from scratch.
Final 1st order crossover, 1.5uF. 2.0uF sounds about right.
The lunatic
When you choose to get the benefit of running the woofer fullrange, you should be ready for the compromises. The benefit of the fullrange is the sonic quality and often the midrange (vocal, soundstage) quality. So what is the compromise? Believe me, even if you measure the drivers, there's no way you can get close to perfect blend of the drivers.
If you choose to run extra filter for the woofer, you have to measure the driver, you cannot do this with calculator because the calculator doesn't take into account the natural roll-off of the woofer.
If you choose to run the woofer fullrange like the original, here is your chance to do it by ears (forget the calculator):
1) Measure the original capacitor (or replace). I have found many old capacitors have reduced capacitance.
2) The Vifa D19 has good highs, but being a small dome it has too good dispersion, the opposite of the large cone woofer. You may get the best axial response but in general listening condition I don't think it is good.
3) The Vifa XT25 likes to be filtered with small cap and it's dispersion matches that of the woofer. I have never tried this but I think XT25 has uncommon phase response where phase is the most critical in this situation. There is a chance tho.
4) Imo and ime, the cone tweeter has the easiest and the best possible integration. I believe that you should try the Visaton (TW-70?) suggested previously. Now how about the value of the capacitor? Forget about calculator here. You are not looking for the correct crossover point but you are looking for the best phase overlap. With first order, the roll-off is far from steep so as far as response is concerned, the value can be anything from 1u5 to 4u7. I think one 2uF plus a few MKPs will do for the experiment. Don't know with you but such capacitors can be found in every trash bins in my house
I hear you all. I hooked up the speakers in another system/another room, and they are really quite nice, though not perfect. I hear you about a dome tweeters possible incompatibility w/ a full range 8" woofer in a sealed box.
I'm waiting for my '66 McIntosh MA5100 integrated amp to come back from Terry DeWick's repair. I bought these speakers to use in a system with this amp and a Dual 1019/Shure M91ED. I should just wait see and then decide. In the meantime replacing the 2uf cap with a Solen may be best. If I upgrade I'm leaning on the Phenolic ring cone tweeter as an upgrade to keep the vintage orientation of the system.
Thanks!
I'm waiting for my '66 McIntosh MA5100 integrated amp to come back from Terry DeWick's repair. I bought these speakers to use in a system with this amp and a Dual 1019/Shure M91ED. I should just wait see and then decide. In the meantime replacing the 2uf cap with a Solen may be best. If I upgrade I'm leaning on the Phenolic ring cone tweeter as an upgrade to keep the vintage orientation of the system.
Thanks!
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