Hole in Dust Cap Affect Sound Quality ??

[excetara2]

Got a hole in my dust cap that is probably about 1/16" inch. The dust cap is really hard plastic. I was thinking about putting an extremely thin layer of glue over the small hole. I don't know if this is necessary.

Is the sound quality affected by the hole usually? Would it be better to try to cover it up?

 

[brianco]

http://www.lampizator.eu/SPEAKERS/PROJECTS/P24/P24_monster_speakers_raal_altec_lansing.html

HAve a look at the section on the midrange.

 

[excetara2]

Are you saying the dust cap extends the midrange. The speakers are cut off at 4K so shouldn't be an issue. Correct?

 

[nigelwright7557]

I would seal it somehow.

The dust cap stops dust getting between the voice coil and the magnet.
The dust would cause friction and affect the sound.

 

[planet10]

Yes, sound quality is affected... often for the better -- sometimes not, but you might need to make it bigger (and do the other driver).

What kind of driver?

dave

 

[excetara2]

The driver is a VIFA D6.8 in a ported 2-way bookshelf system.

I was planning on placing a tiny patch of rubber cement over the hole. Do you recommend leaving it?

 

[CLS]

I'd suggest just leave it. Or, enlarge it!

-- a center hole on the dust cap might look like the lengendary Altec 515

 

[Glowbug]

Excuse to remove both and phase plug 'em?

 

[planet10]

The driver is a VIFA D6.8 in a ported 2-way bookshelf system.

D6.8 sounds more like a HiVi part number...

dave

 

[excetara2]

You are right. The tweeter is a Vifa. The woofer is a hi-vi D6.8.

I guess I'll leave it if that is the rec.

 

[planet10]

Looks like the D6.8 already has a vented dustcap, i'd use a small touch of PVA to seal the extraneous hole just to keep it from growing

An externally hosted image should be here but it was not working when we last tested it.

dave

 

[excetara2]

Yes, that is exactly what it looks like. I don't think it is vented in anyway.

The whole is like 1/4" directly up from the center of the dust cap. Really doesn't seem like it would grow but I will do so.

 

[MisterTwister]

what do you mean it's not vented? I was under impression those holes around dust cap let air flow in/out of 3" coil. is there something else under that cap?

 

[excetara2]

I could be mistaken but if you look at the driver up close. Those are not holes. They go in but plastic appears to be on all sides. I could be mistaken though.

What do you think?

 

[tinitus]

I dont think they are holes
Look at Audiotechnology
They have used the same for many years
I reckon its to achieve at better connection between cone and dustcap
Could be it has some influence on ressonances too

btw, on my 8" woofers I have replaced dustcaps with foamplugs
At the time I thought it was a significant improvement
But may need crossover adjustments
Could be that the improvement was due to dustcaps being inverted, and not attached at voicecoil, but further up on the cone
A better dustcap attached at the voicecoil might be even better
Half a tabletennis ball could be used for smaller drivers
But if you need bigger dustcaps its quite easy to diy
I have used polyurethane glue(foam) and bits of perforated dustcloth, and a mold

 

[Sangram]

The serrated pattern on the dustcap is almost identical to the Dynaudio woofers, and there is no venting on those, FWIW.

 

[tinitus]

On second thoughts
Those poly cones/dustcap are made in one piece, from a sheet of poly baked in a mold
The small "pocketholes" could be to give the voicecoil a good center alignment when glued on, and additionally gives a better/stronger "grip"

 

[MisterTwister]

http://www.audiotechnology.dk/image/8inch_cut.jpg
yes, when I look more closely, it appears those are extruded edges, for greater stiffness I guess.

 

[excetara2]

Since it isn't vented, I am assuming a small dab to patch it up won't hurt.

 

[Illusus]

Half a tabletennis ball could be used for smaller drivers

Half a tennis ball is pretty heavy, relatively speaking, of course. Adding that much mass would significantly change the response. Molding one out of dustcloth is a good deal better, you could also raise the hf response by using thin aluminium.