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B&C 21-IPAL Driver and Measurements Discussion

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Ok so about the ticking noise...I have a plethora of 21's in house from 4 different mfgs. Its not just the Ipals. One of the Lavoce 21's exhibits it and the other does not. And one of the Eminence 21's exhibits it and the other doesn't. It isnt audible in the sealed cab unless I put my ear right up to it. I dont think this is related to the spider gluing. It is present even with less than a few mm excursion. I almost wonder if it is the shorting action of the inductance rings even though that seems really far fetched but it does sound like a small spark jumping a gap. Really odd that Ive seen the same thing from 3 different major mfg's from 2 different continents on drivers with similar motor designs. That many unglued spiders out of such a small sample of drivers from multiple big name mfgs just doesn't seem possible.

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Can anyone link a video of the sound? My hypothesis is that the shorting ring or rings are loose, and moving in response to forces generated by the coil. I should check my recently purchased 21DS115 for extraneous noises before building a cabinet.

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First of all, wow, you already have that Eminence driver to test? I want a set of 4 but I have to wait for 4 moths at least. 

Second, that's odd, I have drivers from 4 different manufacturers, but only those from B&C make that noise.

I'll post a video on YouTube to for you to hear it and relate with.

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6 hours ago, Ukko Kari said:

 My hypothesis is that the shorting ring or rings are loose, and moving in response to forces generated by the coil. 

Thats another option. Might be the correct one too. It is present even with nearly imperceptible excursion levels. It is almost non existent once loaded in a cab and doesnt seem to affect the performance otherwise. 

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3 hours ago, radulescu_paul_mircea said:

First of all, wow, you already have that Eminence driver to test? I want a set of 4 but I have to wait for 4 moths at least. 

Im a 50min drive from them and they are production samples. Full production is a ways off still. Results are very encouraging so far.

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7 hours ago, Ricci said:

Im a 50min drive from them and they are production samples. Full production is a ways off still. Results are very encouraging so far.

That's awesome!  That's a factory I think it'd be a lot of fun to visit.

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15 hours ago, Ricci said:

Im a 50min drive from them and they are production samples. Full production is a ways off still. Results are very encouraging so far.

Yes, I've seen that. The overhang is 21 mm, pole piece is 19 mm so the coil length should be 61 mm, huge. Probably the best 21 pro driver for vented alignment. Also, the BL^2/re product is around 330 and and that double separated suspension should make a very good sound 

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6 hours ago, radulescu_paul_mircea said:

Yes, I've seen that. The overhang is 21 mm, pole piece is 19 mm so the coil length should be 61 mm, huge. Probably the best 21 pro driver for vented alignment. Also, the BL^2/re product is around 330 and and that double separated suspension should make a very good sound 

Coil overhang is 14.63mm. Xmax including 1/3rd of the gap is 21mm. It does that easily. Spiders are mirrored and large enough to maintain linearity. Big shorting ring, etc...Very similar to 21Ipal gap and coil specs. 1mm longer gap and just 0.3mm longer coil wind.

For comparison the coil overhang on a RCF 551 is 10.5mm and a 1/3rd gap xmax spec of 16.5mm.  The  DS115 is 11mm overhang and 15.67mm including 1/3rd of the gap. 

I think you may have had a different issue with your drivers. That's not what mine sound like. What I've been seeing is a higher pitched "ticking". Could be the video recording quality though. I'll see if I can get something to upload. 

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What you hear in the video is the noise I get that keeps getting louder with time. It certainly is a suspension and glueing problem.

 

Very similar on the coil and gap but not magnet and coil material. If the coil is copper it means it is thinner for the same Re if the length is the same. This might mean that the gap width could be smaller so even if the amount of magnet is not the same, it might have a similar magnetic field inside. But that's just speculation.

 

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16 hours ago, radulescu_paul_mircea said:

What you hear in the video is the noise I get that keeps getting louder with time. It certainly is a suspension and glueing problem.

 

Very similar on the coil and gap but not magnet and coil material. If the coil is copper it means it is thinner for the same Re if the length is the same. This might mean that the gap width could be smaller so even if the amount of magnet is not the same, it might have a similar magnetic field inside. But that's just speculation.

 

That's reasonable speculation about the motor / coil specs. There are some differences, but the gap and coil overhang geometry is very similar. Weight is almost exactly the same. I like the spider setup with a spacer ring on the Eminence better though.

Did you recone a 21Ipal yourself? I'd like to see pics of the guts if you have them.

Your video does sound like a suspension issue. I'm hoping to be able to put up a video showing what I'm seeing on the Lavoce driver and the others this Thursday night. I won't have time until at least then. BTW the Lavoce driver seems to be quite capable so far.

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Could be a leaking surround, you would be surprised what they sound like. A ticking noise is not out of the question here. I can't say anything for sure but I do know if there is not enough glue on the pro cloth style surround, it can permeate air. It can be fixed with more glue applied right on top with a brush.

This might be the right stuff. I just did a quick google search so don't take my word for it! You need a little painters brush to apply on top.

https://www.simplyspeakers.com/speaker-repair-adhesive-mi-1291.html

 

 

 

 

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On ‎4‎/‎6‎/‎2019 at 1:46 PM, Kyle said:

Could be a leaking surround, you would be surprised what they sound like. A ticking noise is not out of the question here. I can't say anything for sure but I do know if there is not enough glue on the pro cloth style surround, it can permeate air. It can be fixed with more glue applied right on top with a brush.

This might be the right stuff. I just did a quick google search so don't take my word for it! You need a little painters brush to apply on top.

https://www.simplyspeakers.com/speaker-repair-adhesive-mi-1291.html

 

 

 

 

In my case it is definitely something inside the motor under the spiders. Driver in free-air. It's not really audible once in the cab. Eminence is replacing the woofer that ticks and want to diagnose the issue. The Lavoce driver exhibiting the same thing I haven't contacted them about yet.

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Ya, gonna be hard to guess at what that might be. Report back if they tell you anything.

Good news about your replacement.

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Speculation is it might have been the not enough glue on the joint at the former.

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