Forgot to mention that it looks as if 2 turns were left off the top layer at the voice coil end opposite the dome. This is trick that produces a more linear motor with a simple magnet structure, however the turns should be left off the dome end - odd.
This is often seen in Audax tweeters.
Pete B.
This is often seen in Audax tweeters.
Pete B.
Re: Re: Re: Re: Re: Re: Good inexpensive tweeter
Two theories, either the fabric pad is rubbing against the dome, or there might be a gap in the ferro fluid allowing the front chamber to vent to the rear chamber resulting in the double bump.
Swapped domes, both domes are good, problem stayed with the magnet structure.
Removed the pad, Fs is now lower, but the double bump is still there and changed very little.
Next to look into ferro fluid issues. Looking carefully under good light it is easy to see that the ferro fluid is there only about half way around the gap. Some fluid was soaked into the fabric pad which probably explains the problem.
I'll see if I can get some light ferro fluid to fix it..
I've gotten into the habit of inspecting even new tweeters after finding several with issues out of the box. I suggest inspecting these before use.
Pete B.
PB2 said:
Two theories, either the fabric pad is rubbing against the dome, or there might be a gap in the ferro fluid allowing the front chamber to vent to the rear chamber resulting in the double bump.
Swapped domes, both domes are good, problem stayed with the magnet structure.
Removed the pad, Fs is now lower, but the double bump is still there and changed very little.
Next to look into ferro fluid issues. Looking carefully under good light it is easy to see that the ferro fluid is there only about half way around the gap. Some fluid was soaked into the fabric pad which probably explains the problem.
I'll see if I can get some light ferro fluid to fix it..
I've gotten into the habit of inspecting even new tweeters after finding several with issues out of the box. I suggest inspecting these before use.
Pete B.
Could be a fluke. At $10 a pop I'd buy another pair just to see. AFAIK they are sold as matched pairs so at one point they must have measured the same.
Willitwork said:
I didn't need the first pair - LOL!
But yes I agree they are inexpensive, still want to fix the old one.
Pete B.
PB2 said:
After hearing a demo DIY speaker based on the Dynaudio Gemini kit that used Hi-Vi drivers instead of Dynaudio (K1 was stand-in for D21) I bought six pairs of K1's that I didn't need... and three pairs of Hi-Vi's massive dome mids even though I had no real intention of tackling a 3-way design 😀
But now that my Behringer electronic Xovers are here the possibilities are endless. 🙂
Try this simple tweak
I've been experimenting a bit with cotton rather than lamb's wool felt that I like to use in tweeters to damp the pole piece vent. When there's no chamber, the wool doesn't work (it's hard to compress enough) as well and the small volume is an issue. Try using come cotton to fully stuff the vent. The easiest and possibly best cotton is what you find in aspirin and other medicine bottles. It's highly processed, is uniform and often similar density from one to the next, even across different companies. It is much easier to work with than cotton balls and stays put in small volumes better than lamb's wool. This will show if there's any influence from the vent area in any odd impedance characteristics.
I also open every tweeter to inspect/experiment. Sometimes a problem is nothing more than bad placement of damping materials.
Dave
PB2 said:
I've been experimenting a bit with cotton rather than lamb's wool felt that I like to use in tweeters to damp the pole piece vent. When there's no chamber, the wool doesn't work (it's hard to compress enough) as well and the small volume is an issue. Try using come cotton to fully stuff the vent. The easiest and possibly best cotton is what you find in aspirin and other medicine bottles. It's highly processed, is uniform and often similar density from one to the next, even across different companies. It is much easier to work with than cotton balls and stays put in small volumes better than lamb's wool. This will show if there's any influence from the vent area in any odd impedance characteristics.
I also open every tweeter to inspect/experiment. Sometimes a problem is nothing more than bad placement of damping materials.
Dave
Yes, I've used cotton also, its used in the North D25-06S. Have you had a look at these?
Pete B.
Pete B.
Thinking ... The voice coil takes significant volume in the gap, and therefore it doesn't have to be full. I'm not sure if the fluid will displace evenly during reassembly and certainly the impedance test indicates that this tweeter is not full. Might help to let the tweeter sit in different vertical orientations so that the fluid can migrate once there is enough in the gap. I also wonder how to be sure that enough is displaced both inside and outside the voice coil. Some is left on the coil itself, perhaps it should be applied to both the coil and gap.
Pete B.
Pete B.
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