Tapped Horn Tearing Speaker Cones

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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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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. :eek: 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.
 
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 ?
 
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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WOW you guys are fast.
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
 
maybe a leak in the path might create uneven pressure across the cone
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
 
Unfortunately running the amplifier at half gain does not restrict the power output.
Transients must be hitting those Eminence drivers quite hard!
Depending on what crossover you are using, you may be able to set limiters to restrict the output power.
(I aways run my PA amps wide open so that no one can turn them up:D)
Given the robust way you made the cabinets, and the amps you have, a driver upgrade might be in order.:eek:
Regards
Martin
 
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.
Yes the damaged part of the cones is now very flimsy.
Have you ever measured peak to peak cone movement with similar program to what kinked the cones?
No I have not meashured the speaker travel. Is there a good tutorial on how to do it?
Were there any open microphones while fireworks were discharged?
No Mics even hooked up at the time of damage, I fould the damage before the fireworks show after setup and testing.
Andy
 
Hi Andy, partial movement is nothing else than the resonance(s) in material, in this case the resonance in the cone. In post # 8 you can see how the circle gets 'deformed' under this resonance. You see two different deformations since the circle represents a flat surface. The cone’s form makes only one deformation possible.

In your picture you can see the 'cracks' leading from the outside to the bobbin (Voice Coil Former). Also in your picture you can see it only happened in one half of the cone structure. That means the partial movements were suppressed in one side of the cone. My question is, how these drivers were mounted, or in other words, to which point the cracked side of the cones were pointing?

If you decide to repair the woofers make sure you mount them back the other way around because maybe the cracks can be repaired, but these spots will stay the weak point in the cone structure. Therefore after repairing you have to make sure the cracked sides are pointing to the other direction.

As Martin already pointed out, you have to use limiters in your setup. I thought the Behringer limiters in their crossover are so called “brick-wall” types, which means they don’t allow any dB beyond the setting of the limiter value (threshold). These limiters should do the job.

About the High pass setting, if you are going to use TH’s in stacks, the acoustic coupling of the horns (tapped pipes as some prefer) makes the excursion go higher compared to TH’s in single use. This is not the same as acoustic wavelength coupling you see in normal horns since the 1/4WL of a TH will not drop much. Always make sure the low-cut filters are set at or above the 1/4WL of the total horn path. In case you are going to use big stacks change your 24dB slope into 18dB or even 12dB slopes (all @40Hz) to compensate for the extra excursion (or lower the input power per cab).
 
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My question is, how these drivers were mounted, or in other words, to which point the cracked side of the cones were pointing?
The damaged part (or half) of the speaker is at the vary start of the horn between S1 and S2 locashoins used in hornresp.
If you decide to repair the woofers make sure you mount them back the other way around
Thay are getting reconed.
As Martin already pointed out, you have to use limiters in your setup. I thought the Behringer limiters in their crossover are so called “brick-wall” types, which means they don’t allow any dB beyond the setting of the limiter value (threshold). These limiters should do the job.
Yes I will have to look into how to properly set them. Up untill now I have been using the default parameters for evey thing exept the crossover settings. I am gessing that I will need differant setting depending on weather I use 1,2 or 4 speackers per channel.
About the High pass setting, if you are going to use TH’s in stacks, the acoustic coupling of the horns (tapped pipes as some prefer) makes the excursion go higher compared to TH’s in single use. This is not the same as acoustic wavelength coupling you see in normal horns since the 1/4WL of a TH will not drop much. Always make sure the low-cut filters are set at or above the 1/4WL of the total horn path. In case you are going to use big stacks change your 24dB slope into 18dB or even 12dB slopes (all @40Hz) to compensate for the extra excursion (or lower the input power per cab).
I thought we were working with 1/3 wave lengths in a taped horn.
Andy
 
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