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Old 25th July 2011, 05:53 PM   #1
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Default Tapped Horn Tearing Speaker Cones

I have used my pyrobox tapped horns a few times now and have had some interesting speaker cone damage on two of the 8 boxes I made. Thay have creased and delaminated on the inside of the box only. That is to say the damage is on the side of the cone that is closest to the end of the horn.
I dont think thay have been over powerd but thay had the shortest speaker wires run to them.
Maybe I execeded Xmax?
Maybe not having a tapered throat is not such a good thing?
At this point I would like to rule out the TH box design.
Any thoughts?

Here is the box;
The throat is 3-3/4" on both ends.

And here is the damage;
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Old 25th July 2011, 06:07 PM   #2
badman is offline badman  United States
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Sure looks like you're exceeding Xmax- have you highpass filtered these?
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Old 25th July 2011, 06:18 PM   #3
Xoc1 is offline Xoc1  United Kingdom
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What Crossover settings are you using?
How much power per driver?
Is that the Eminence 3015LF driver in the photos?
Regards
Martin
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Old 25th July 2011, 06:25 PM   #4
Djim is offline Djim  Netherlands
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Good example of partial movements...
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Old 25th July 2011, 06:29 PM   #5
18Hurts is offline 18Hurts  United States
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So it tore at the closed end of the horn so maybe there is uneven pressure at the end? Very interesting, maybe a leak in the path might create uneven pressure across the cone which creates havoc and excessive stresses at that point. Since your area right in front of the cone is not tapered, it would seem (in theory) that should be a more stable air mass to push. The closed end would create different pressures but it should be OK.

I'd measure out the path with a micrometer on the blown woofer boxes then measure them out again on the boxes that have no damage. Maybe something slipped, is leaking or myriad of other issues when playing with wood. If you want to get crazy, seal off the woofer holes and pour in water to see if the throat is leaking.

Fix the cones with a 50/50 mix of Elmers Glue and stiff paper (I've used layered brown paper bags in a pinch) Test the boxes at low power to see if there is a very large difference in frequency response. Say the SS15 normally does 45Hz and now it's peaking at 65 Hz...you are losing pressure in your horn path and the box is unloading rapidly and exceeding Xmax before the high pass filter kicks in.

You stated that it was two boxes out of eight. I'm assuming you have all 8 of them hooked to a two-channel amp in some configuration to operate. That should rule out amplifiers, too much power, too much Xmax and other variables.

If you're running two amps and 4 channels into 8 boxes, it might be one channel on the amplifier feeding those two boxes. One of the channels could be passing a very low signal to that pair causing damage from excessive Xmax.

Had a ripped Cerwin Vega 15" woofer and fixed it with Elmers/paper patch on the cone forward side and covered the back of the rip with finger nail polish. It has been running fine in isobarik configuration for the last 10 months without issue. Can't see it because it is the inner woofer of the Iso group.

Just a shot in the dark but testing them with patched woofers might be able to help troubleshoot. After you're done, get the recone kits installed to keep everything standard.
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Old 25th July 2011, 06:59 PM   #6
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Quote:
Originally Posted by 4pyros View Post
I have used my pyrobox tapped horns a few times now and have had some interesting speaker cone damage on two of the 8 boxes I made. Thay have creased and delaminated on the inside of the box only. That is to say the damage is on the side of the cone that is closest to the end of the horn.
I dont think thay have been over powerd but thay had the shortest speaker wires run to them.
Maybe I execeded Xmax?
Maybe not having a tapered throat is not such a good thing?
At this point I would like to rule out the TH box design.
Any thoughts?

Here is the box;
The throat is 3-3/4" on both ends.

And here is the damage;
It looks like the speakers not only exceeded Xmax, but Xlim.
The speaker with the shortest speaker wire will have the most damping factor, exerting the most control over cone movement, the magnet can push or pull the cone more effectively with the short cable.

Unfortunately, even the undamaged cones may be stressed, I have seen many progressive failures looking like what you show, the cone gets "tenderized" over a period of time then starts to buckle.

What HP filter are you using?

Have you ever measured peak to peak cone movement with similar program to what kinked the cones?

What power amp, how many drivers per side?

Were there any open microphones while fireworks were discharged?

Not sure what you mean "damage is on the side of the cone that is closest to the end of the horn" was the position of the damage in relationship with the cabinet, kink towards the grill, or towards the back ?
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Old 25th July 2011, 07:00 PM   #7
epa is online now epa  Netherlands
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is the hole in the bafle a slot or circular 14.03" ?
edit/found the answer in the ss15 topic .
but it seems to me a combination of overexcursion and uneven loading.
i fixed an 18"beyma once with carbon fiber treads spreaded out and wood glue (verdunt)mixed with water)
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Last edited by epa; 25th July 2011 at 07:12 PM.
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Old 25th July 2011, 07:39 PM   #8
Djim is offline Djim  Netherlands
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Old 25th July 2011, 08:05 PM   #9
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WOW you guys are fast.
Quote:
What Crossover settings are you using?
How much power per driver?
Is that the Eminence 3015LF driver in the photos?
Regards
Martin
I have them crossed between 40 and 120 Hz.
Yes thay are kappa Lite 3015LFs
At the time those tore I was running 2 per channel off a QSC PL380 with 1/2 gain. Its rated at 2500 watts per channel at 4 ohms. At half gain it should be 1250 per channel and 625 max per speaker. So yes the amp could have over powered them.
Andy
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Old 25th July 2011, 08:16 PM   #10
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Quote:
maybe a leak in the path might create uneven pressure across the cone
Quote:
Maybe something slipped, is leaking or myriad of other issues when playing with wood
I dont think it could be a construction issue. I made the throats separately as a sealed box with a removable speaker mounting plate and then installed the hole assmbly into the horn. I used 3/4 poplar hardwood for the sides and 3/4 birch ply for the panels put together with PL glue.
I can look again to see if I see anything out of sorts but doubt it.
Andy
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