Gap between coil and pole piece

[tech.knockout]

I just bought a pair of 15" coaxial speakers with 4" voice coils. I notice that the gap between the coil and the middle pole piece section (containing the horn mouth of the tweeter) is about 2mm, which I think is rather large. There is no rubbing and the cone seems to be centered.

Would this large gap pose problems?

[devilsindetails]

Pics?

[Tomom]

If sensitivity of speaker is to spec, why would that pose a problem...

[VaNarn]

A precision machined magnet assembly can have a clearance of around 0.16mm although if a high power/long throw coil is used,a 0.2mm spacing between the voice coil former and the centre pole could be expected.As Tomom says,if the sensitivity is o.k.then there is not a problem with the speaker.Copy paper is 0.1mm thick;you could double check your clearance estimate by sliding a few strips into the gap as an indication

[devilsindetails]

Pics would be helpful as would type, manufacturer and any other specs on the driver itself. Vintage? or New?, for example.

[tech.knockout]

Actually I just found out that the gap narrows down at some point. What I thought was the centre pole piece is simply a piece of metal for the horn throat that is glued down on top of the centre pole piece. Tight clearance is not required for this piece. Case solved.

The coaxials are from some chinese factory, I purchased them via alibaba. http://huiyinaudio.en.alibaba.com/pr...l_speaker.html

They seem pretty well made other than from the fact that the transition from the non-moving part of the coaxial horn to the cone part of the coaxial horn isn't perfect. The solid throat ending juts out at about 2mm above the cone. I will make another thread asking for some ideas to tackle the diffraction issues from this, plus piccies.