How to fix a Hi-Vi TN28 tweeter (or - "Why did I buy this tweeter?")

[fjhuerta]

Hi all!

Thought I'd share this very simple mod to the TN28 tweeter by Hi-Vi.

I bought it by mistake ($99 retail price - get it for $14.25 NOW!). And I soon realized it wasn't exactly what it was supposed to be.

Suffice to say, the impedance plot was so strange, so unruly, so misbehaved, so... that I deemed it to be unusable.

FR wasn't that bad, but it was mind-bending, too.

So, I disassembled the thing. I wish I had taken pics, but after breaking apart the tweeter (it comes apart from the junction between the golden "ring" and the black enclosure) I realized it had only just the tiniest bit of polyester batting inside.

I removed all the polyester, and inserted a small piece of cotton on the vent between the dome and the cavity (in the middle of the neo magnet) and then filled the black enclosure with lots of cotton. I reassembled the tweeter.

I'm attaching a couple of plots with the results of my mods. From completely useless to "maybe I can do something with them", for the price of some cotton balls. I wonder - why didn't Hi-Vi did the same out of the factory? I just don't get it.

Anyway, the "Reference" plots come from the modified tweeter, the stock curves are in blue.





Frequency response





Impedance plot


EDIT - I was just taking a look at Zaph Audio's test of the TN28. The graphs look a lot like my own - except that the impedance and FR plot are a lot harder to see due to the scale he uses. I thought it may have had something to do with my personal pair - apparently, his TN28's also have the same problems mine had.

[TurboFC3S]

Interesting, I've always thought those tweets could have some nice applications ... if they just performed decent.

[fjhuerta]

Interesting, I've always thought those tweets could have some nice applications ... if they just performed decent.

I wish I had SoundEasy, so I could find out if their distortion measurements were affected, too. As it is, JustMLS will have to do I'd assume the cotton could have helped there, too.

[Dennis H]

Wow, that impedance curve really tells the story. Nice one, Javier!

[mrogowski]

Yes, very interesting. I find it surprising that a $99 'retail' tweeter can go all the way down to $14, and even at that price point its not worth it.

Best,
Mark

[dlr]

Nice work

Hi all!

Thought I'd share this very simple mod to the TN28 tweeter by Hi-Vi.

I bought it by mistake ($99 retail price - get it for $14.25 NOW!). And I soon realized it wasn't exactly what it was supposed to be.

What merchant listed it at $99????

So, I disassembled the thing. I wish I had taken pics, but after breaking apart the tweeter (it comes apart from the junction between the golden "ring" and the black enclosure) I realized it had only just the tiniest bit of polyester batting inside.

Is it glued together and easily separated? I have one, but hesitated to pry it open. I'm not surprised at what you found inside.

I removed all the polyester, and inserted a small piece of cotton on the vent between the dome and the cavity (in the middle of the neo magnet) and then filled the black enclosure with lots of cotton. I reassembled the tweeter.

I have a single one for testing, I'll have to try this is well, though I may not use cotton.

I'm attaching a couple of plots with the results of my mods. From completely useless to "maybe I can do something with them", for the price of some cotton balls. I wonder - why didn't Hi-Vi did the same out of the factory? I just don't get it.

Given how often this occurs and how much improvement there can be, I've wondered the same thing for a long time. Gotta ask the bean counters, I think.

Anyway, the "Reference" plots come from the modified tweeter, the stock curves are in blue.

How did you mount them for measurements?

[fjhuerta]

What merchant listed it at $99????

I have a Parts Express catalogue from 2004, IIRC. List price is given as $99!

Is it glued together and easily separated? I have one, but hesitated to pry it open. I'm not surprised at what you found inside.

Glued together. It comes together quite easily. Twist it a bit, then pry it open - sloooowly, or else, you risk destroying the leads.

I have a single one for testing, I'll have to try this is well, though I may not use cotton.

I wouldn't have used cotton either - I'd have tried lambswool. But I didn't have any available.

Given how often this occurs and how much improvement there can be, I've wondered the same thing for a long time. Gotta ask the bean counters, I think.

If they really tried selling it for $99 at one point, and now are practically giving it away at $13, I bet they don't care about how it performs. At all.

How did you mount them for measurements?

On top of a 20 x 100 cms square baffle, no rounded edges, completely flat with the baffle. I was actually thinking about using it with some throwaway speakers I had (now that they perform a bit better, I'll be building a small TMM).

[dlr]

The glue on mine does not release

Glued together. It comes together quite easily. Twist it a bit, then pry it open - sloooowly, or else, you risk destroying the leads.

I tried to open it last night. I had tried to open it this way early one, but it gave no sign of coming apart easily. This one won't turn, even a small screwdriver won't budge it at all. The glue on this one must have been applied more liberally. I'll almost have to destroy it to open it up.

[fjhuerta]

I tried to open it last night. I had tried to open it this way early one, but it gave no sign of coming apart easily. This one won't turn, even a small screwdriver won't budge it at all. The glue on this one must have been applied more liberally. I'll almost have to destroy it to open it up.

Maybe heating it would do the trick? I had mine apart in 30 seconds or less. It probaly had a lot less glue.

[Oak244]

I know this Thread is old, However I need to replace the tweeter in one of my Swan Diva speakers. The current TN28 is a flat black color, and my speaker is Piano Black with a gold ring. Will I be able to take the Old and New one apart and swap the new good tweeter inside my old piano black case?