Tweeter choise with Fountek FW146

[BrechtVD]

It is really crazy, once you rolled in this diy audio world you can’t get enough of it . Even if you keep on reading and every time you read things you not knew of. Maybe that’s why I can’t get enough of it

So like I said I read some nice things for like a week or so and of course when you are reading you get ideas for new speaker but I still have some questions or things I like to, to hear a second opinion off.

I would like to build a 2-way (MT) design with a Fountek FW146 (I know ZA14W08 is probably a better choise but not avaible in Europe as far as I know). Because of the non-linear distortion of the Fountek rising at 2k it needs to be crossed let’s say a bit over 2kHz 4 th order (read it from other pro’s but I think the same about it since I know what that’s all about, non-linear distortion, really interesting )

http://techtalk.parts-express.com/showthread.php?215217-Zaph-Audio-ZA14W08-VS-Fountek-FW146

Non-lin. measurement at the bottom of this web page

So the most important parameter for my tweeter was a low fs and if it was possible a flat freq.responce and cheap if possible .

I found 2 Vifa tweeters
*BC25SG15-04

http://www.tymphany.com/transducers/transducer-search-results/transducer-detail/?id=12

*DX25TG59-04

http://www.tymphany.com/transducers/transducer-search-results/transducer-detail/?id=568

The first one has a more flat freq. response but the fs will be maybe at his limits, that is what I don’t know for chore. (strange also is that the measurements from Zaph audio are a bit differend??, there the freq. response lowers 2-3db from 8kHz)

http://www.zaphaudio.com/temp/Unisound-BC25SG15-04-FR.gif

The second one has a lower fs but a peak in the freq. response at let’s say 15kHz and is a bit more expensive . But maybe I can take here a lower order in the X-Over.

So which would be the best tweeter to choose, or is there one I overlooked with a low fs and a nice freq (and not to expensive). response to work with??

Thanks in advance!!
Brecht V.D.

[5th element]

I have to say that there is something wrong with the distortion measurement of the ZA14 on the PE forums. I don't know if the driver was defective or if something else was screwing with the performance, but that drastic rise in the third order above 150Hz is clearly not right. Jon Marsh has measurements of the ZA14 that closely mirror Zaph's own measurements as well, but I digress, this isn't about the ZA14, but about the FW146, which actually looks like a very good driver. As you've concluded yourself a ~2k 4th order acoustic cross would be ideal. The trouble is choosing your tweeter correctly.

Absolute tweeter flatness is important, but it's not the be all and end all, just as important is the box design, countersinking of the tweeters faceplate and any box diffraction problems that will occur. No matter how ruler flat your tweeter may be if box diffraction comes along and places a hump in the wrong place it can make xover design more troublesome than you might think. Either way, it's better to start out with silk rather than a sows ear.

It is very possible to cross over a tweeter closer to it's fs than is usually recommended but if you do, you absolutely have to go 4th order acoustic. What's important though is making sure that the tweeters distortion performance allows it to be used in that way. If you look at the distortion performance of the BC25SG you will see that it will handle a 2k cross with no problem. The drooping response in the top octave isn't really an issue but it will require more crossover components to flatten possibly.

Where you are located could possibly determine what tweeters we could recommend as this would affect availability, so where are you in the world? Lots of tweeters will work, it's just which ones might be better than others.

[BrechtVD]

I live in Belgium (Europe).
So the brand that are normally no problem (for tweeters and in my price range ) are Dayton, Vifa, Seas and Monacor.

I was already playing around with the Vifa DX25 and it was not a bad choise because I ended up with a crossover freq. of 1.8Khz and that would be too much for the other one.




The only problem I now have is that my electrical phase is way too much off, a little more than 60° (2khz) . So with my electro mechanic background this means my cos(phi) is 0.5 for that freq. So my amp has to push the double of power I would hear (if I am right).
And now I am trying to get it up by taking a higher value for L3 but it’s much harder than I would thought.

And I just saw the 60° in the lower freq. range is maybe a fault of mine, because in “Frequency response modeller” it is like 45° not 60°.

And for the baffle placement I have a little 3D-model with the program I have avaible because of my studies, but I maybe will make it a bit taller (debt a little to much) like an inch and move everything an inch up so I have the same placement from the top. But I saw that my baffle diffraction chance more than I thaught so maybe leave it like it is now


So In short: much fun but more work than I thought if you want to do it right.
And if you know a nice tweeter with low fs that I overlooked, always welcome but I think I will stick with the Vifa DX25

And off course thanks for the response!! 5th element

[Carl V]

I have had nice results with

http://www.seas.no/index.php?option=com_content&view=article&id=366:e0006-06-t25cf001&catid=50:excel-tweeters&Itemid=360

Good luck.

[5th element]

RE the electrical phase, welcome to the world of xover design and optimising the impedance so that a loudspeaker is easy to drive. It doesn't actually impact on the sound quality of the loudspeaker itself it just makes the amplifiers job harder and in turn will most likely result in reduced linearity within the amplifier during the frequency band that is difficult to drive. The easiest way to combat this is to make sure you use an 8 ohm tweeter, or increase the seen impedance of the tweeter network by bumping up the effective series resistance of the lpad you are using. Of course this requires you use a tweeter of high enough sensitivity so that you've got the freedom to do so. With the FW146 this shouldn't be too much of a problem as after baffle step compensation you're going to be looking at a rather insensitive end loudspeaker.

As you are in Europe you do have access to quite a range of drivers, of course this depends on where you are buying from, but it at least keeps many options open.

Generally speaking SEAS prestige tweeters are very well regarded, are easy to work with and can handle low xover frequencies without any issue. They also come with the excellent SEAS build quality, quality control and you can also buy replacement dome/voice coil assemblies if you happen to toast one. They are a little bit more expensive than the DX25, but imo, worth the extra pennies, the 27TBFCG is one of the better ones along with the DXT. The DX25 is a nice cheap soft dome tweeter with decent low end capabilities, but it's not quite as capable as some of the SEAS drivers.