Increasement in db with extra magnet

[Per Nielsen]

Hi

I have a pair of special versions of the Vifa xt25 tweeters, with an extra magnet on, an a larger rear chamber, but I can't find a datasheet on them...

So what kan i expect in an increasement in db?? the magnet is the exact same size as the original one??

[tinitus]

Hi, my guess is you get maybe one db more - but I am told it will lower Q - and as a result more precision and then maybe the "feel" of a more sensitive driver.

[ShinOBIWAN]

Originally posted by Per Nielsen
Hi

I have a pair of special versions of the Vifa xt25 tweeters, with an extra magnet on, an a larger rear chamber, but I can't find a datasheet on them...

So what kan i expect in an increasement in db?? the magnet is the exact same size as the original one??

I think you'll find that this 'special version' of the XT25 is simply the shielded version They generally come with an extra magnet to cancel the stray magnetic field.

[tinitus]

Shinobiwan might be right - that the extra magnet may be after the poleplate and therefore turned the opposite way to cancel magnetic stray - but nonetheless, even so the driver changes character - allthgough I have only experimented with woofers with two extra magnets

[Per Nielsen]

No the magnet is not there to cancel magnetic strays

this is a special oem version that can't be bought, im testing out for a speaker projekt, unfortunely nobody as a spec sheet on it(they claim it never has been done)

So I was after some more specific facs in, the increasment in db with a extra magnet... I am perfectly aware of that the magnet is there to make the tweeter more precise... the db increasement is a side effect....

I simple dont have measurement equitment to do a scan...... Because my designs is all done by the ear

Just wanted to know before i mocked up a crossover....

but 1db sounds oka so I will try with a attenutation a that amount....

[ShinOBIWAN]

Does the tweeter have any markings or model number?

Here's the shielded XT25SC-30-04
http://www.akkus.com.pl/index.php?gr...20d822d4f68406

And the regular XT25TG-30-04
http://www.akkus.com.pl/index.php?gr...5c4d23eec52a71

Are you really sure this isn't a shielded version? You've got some interesting drivers if they're custom and shame you can't measure them if thats the case. BTW the XT25 is a great tweeter isn't it.

[Salas]

Because my designs is all done by the ear

Can you elaborate?

[Per Nielsen]

No It's not any of thoose versions

It can't be bought in stores... I was told it was the best one they ever did, but it only done in a very small quantaty.... time will tell how good it really is.... right now it sounds like the sensitivty is more like 93db.... I will try a bit more attenuation...

Salas:

Something important i have learned by all my projects is that the best sounding equitment often has the worst specs ever.... so I have gotten rid of alle my measurement tools It's all done by my ears....

Now that the projects has gotten seriuos -I belivede that it's extremly important that i follow my intuition....

[sreten]

Hi,

the tweeter in the image does not have an extra magnet
- well not in the magnetic circuit anyway. It is an expensive
form of providing shielding by using another main magnet.

The two magnets must be joined directly and the pole piece
be at the bottom to have a double magnet driver - which
Vifa do make :



/sreten.

[Per Nielsen]

No your wrong.... it's not a sheilding magnet... It's only a sheilding if it is attached with reverse polarity -this is not...

You also get extra magnet power by glueing one on like this behind the other one... this is what they have done to prevent them from re-designing the chassis because thats expensive....

anyway got the answer from ShinOBIWAN with one db... i simply just didn't knew if we where talking 1 db or 10...

It appears to be 2 db...