Loudspeakers quality... you've got what you payed for ?

[silverprout]

Hello !

Here is a cheap Fountek loudspeaker (FW168), the cone is so much bad centered that it touch the center pole piece at full excution.



You should perhaps say... you've got what you payed for !

Here is a top of the line Seas Excel magnesium driver.
The cone is bad centered about one full millimeter.



There is a gap of 0.4mm between the magnet and the pole plates.




No conclusion.

 

[dragonweed]

It is likely that not the center pole piece that is offset, but the phase plug, which is either glued, or - the better case- fastened to the pole piece with a bolt. (going through the center pole piece). In the second case you can try to loosen the bolt a bit, [if it is accessible on the back plate] and center the plug manually. In the first case... well, you are screwed D), because the glue they use won't let it go easily.

 

[silverprout]

It is likely that not the center pole piece that is offset, but the phase plug, which is either glued, or - the better case- fastened to the pole piece with a bolt. (going through the center pole piece). In the second case you can try to loosen the bolt a bit, [if it is accessible on the back plate] and center the plug manually. In the first case... well, you are screwed D), because the glue they use won't let it go easily.

Thx for you trick.
I've already try to loosen the screw and re center the phase plug... but there is no margin at all, the plug is touching the aluminium coil support all the ways.

 

[dragonweed]

Upon looking at the photo of the FW146 , now I think that the entire cone with the surround is glued offset to the frame. (The gap between the edge of the rubber surround and the frame is not even around the perimeter)
If you are brave enough to do it, you can try to peel off the rubber surround from the frame (you can do it with a sharp flathead screwdriver and a tweezer -but very slowly, and carefully, few mm at one time- then "re-center" and re-glue it with slow setting contact glue (test it, it should not dissolve rubber....).
I've done this a few times with about 80% success rate.

 

[dragonweed]

You can get the idea how to do the centering on the attached picture.
Try different thickness paper strips, until you can move the cone up and down (but not too stiff) , then do the surround glueing. After the glue set, remove the strips, and it is done......
The gap between the upper pole plate and the cast frame is due to the manufacturing technology used (stamping), whereas the edge of the stamped iron ring is somewhat curvy, but it should not affect parameters and performance at all.

 

[dragonweed]

One more thing...I think that the price/quality ratio of the Fountek woofer is much better that in the case of the Seas. The FW 168 in the right size reflex box (cca. 18 liters) with the right crossover (resonance peak compensated 2nd order at 2 kHz) can perform excellently.
I happened to know, because I've built a pair with Neo X2 ribbons for a friend of mine, and he says it is overall better than the SF Concertos he had before.

 

[silverprout]

You can get the idea how to do the centering on the attached picture.
Try different thickness paper strips, until you can move the cone up and down (but not too stiff) , then do the surround glueing. After the glue set, remove the strips, and it is done......
The gap between the upper pole plate and the cast frame is due to the manufacturing technology used (stamping), whereas the edge of the stamped iron ring is somewhat curvy, but it should not affect parameters and performance at all.

You are right about the bad centering of the rubber suspension... but the motor is also misaligned.

The motor/coil alignement seem pretty good.


No comments... hum hum

 

[Bill poster]

Cool thread! Diy Detective work

 

[ShaneF]

Yeah, this is pretty bad.

 

[silverprout]

Yeah, this is pretty bad.

It is a small semi-artisanal production, i was aware.
But quality issues with my very expensive and very high quality loudspeakers have convinced me to give them a chance.
It seems not catastrophic :
- The worst solution is gluing the phase plug directly on the pole piece but it is irreversible.
- The best solution is to use an threaded adapter with a smaller diameter screw that offer more adjusting margin.

 

[eriksquires]

we are cometely sure that is a seas? sometimes chinese factories sell seconds through the back door too.

 

[TMM]

The fw168 I purchased recently have similar build issues - mine don't rub but are mighty close. T/s Parameters are also way off - Fs 20hz too high, vas halved, qms too low.

I didn't notice you could unscrew the plugs, might try that!

 

[Bare]

Sure reads like ; Refund! is in order.

 

[TMM]

Removed the phase plugs from mine - one had enough slop due to the raised part being smaller than the recess on the pole piece that I was able to center it properly and tighten it down. The other didn't have any slop but by rotating it the alignment is now much better than it was.

 

[silverprout]

we are cometely sure that is a seas? sometimes chinese factories sell seconds through the back door too.

I've bought them at Madisound in 2005 and finally decided to keep them because of the return shipping fees.
I'm satisfied of my Seas loudspeakers drivers despite their imperfections.

Sure reads like ; Refund! is in order.

I'm not a cosmetic perfectionist and they are cheap enough to tempt the adventure. A lower VAS and a highest FR is not a problem for my application, it is a advantage !

Removed the phase plugs from mine - one had enough slop due to the raised part being smaller than the recess on the pole piece that I was able to center it properly and tighten it down. The other didn't have any slop but by rotating it the alignment is now much better than it was.

You are a lot more lucky than me, i'm building a M6 to M4 thread adapter, the two poles pieces should be perfectly centered with a margin of +-2mm.

 

[xrk971]

https://www.thorlabs.com/thorproduct.cfm?partnumber=AP6M4M

 

[Eldam]

Go with EMS Speaker, they made a speciality of their ability to center voice coil and it is local production around Fertin family.

Artisanal french price unluckilly for our wallet, but dunno if Mister Fertin is retired but you have a lot of advices which come with the price of the drivers : an other world than the off the shelves drivers of biggest brands !