mid bass driver repair

[str8fast]

A little while back I had a problem w/a mid bass driver on my Compact 7's. I realized it as soon as it happened although thereafter it was difficult to detect because it seemed to reveal itself at only a certain frequency or frequencies. In any event, I brought it to my dealer and the unit appears to have been repaired, not replaced. I was told it was replaced, but perhaps I misunderstood. I will clarify that, but there are quite a few fingerprints all over it which could conceivably have happened during the installation, but what leads me to believe it was repaired is that the circumference of the cone where it attaches to the driver is not smooth and even like the radial driver in the other speaker and appears to have been glued.

Is this a proper result? Are the fingerprints something to be concerned about and can they be removed? I don't seem to detect any audible problems, but perhaps I'm missing it. Visually it doesn't look right, but its the sound that matters and I'm left wondering if this was correctly done and if performance is degraded.

I'm going to address this with the dealer, but before I do I'd like some additional information.

Much appreciated.

[A.S.]

... there are quite a few fingerprints all over it ...

This is not really an issue for the harbeth User Group as you are already engaged in a dialogue with your dealer who I'm sure is committed to helping you right through.

As for finger marks - they certainly don't degrade the sound and could be cleaned with, I suppose, a mild solution of washing up liquid on a cotton ball, NOT a tissue or kitchen cloth. At Harbeth we avoid touching the cone but would probably use isoprop alcohol and an industrial non-cloth tissue.

WARNING! Do not press the cone! Do not rub the cone or you will introduce micro-scratches.

[miniwatt]

WARNING! Do not press the cone! Do not rub the cone or you will introduce micro-scratches.

Alan, will micro-scratches impact the sound quality?

{MODERATOR'S COMMENT. This is not a question for Alan. What do you think?}

[yeecn]

Alan, will micro-scratches impact the sound quality?

{MODERATOR'S COMMENT. This is not a question for Alan. What do you think?}

I would think that it will have an effect. The scratches will probable break up the surface and affect the sound wave propagation along the cone surface.

But how many scratches/how deep a cut can the cone surface sustain before the sound degradation become audible? I would like to see some sort of experiment where scratches/dusts are introduced to the cone surface, and establish some sort of quantitative measure to a safety limit.

I have been wanting to ask this question for a while. In a normal household there is bound to be aerosol spray and dusts and whatnots that will cumulate on the cone surface over time. I have been wondering at what point it will begin to make a audible difference.

{Moderator's comment: Please forget it. Dust and scratches are relevant to LP records, not loudspeakers. The cone can be cut right through with negligible effect. This is a non issue.}

[miniwatt]

If that's the case, Alan's previous warning is purely for protecting the aesthetic only.

{Moderators comment: Correct: the best tool for cleaning the cones if absolutely necessary is a photographer's air brush}