Flared, horn-ish ports are for exactly this purpose. The port isn't that small and with an Xmax of 6mm such a high velocity isn't even possible. There's yet another explanation though. High spl and just at certain music causes it? That sounds like you forgot your lowcut (or it's too low) and the driver does too much excursion. No back vented box may be used below the tuning frequency! Try a lowcut of 39-42Hz. And especally no EQ boost down there!
Even if you'd shorten the port to just 2cm length in the simulation, the tuning frequency does not rise above 40 Hz.
It does however fit the K2, 74/2= 37Hz. Do you use an exciter or a similar effect? An exciter would create the lower harmonics, which would be below the tuning frequency, causing the driver to exceed the maximum excursion. If you take out the frequency with a notch filter, the lower harmonics isn't created anymore, the effect is gone. The drivers are a heavy mismatch with the enclosure anyway, the best driver can't work properly in the wrong enclosure with the wrong tuning. I would bet the Celestion (even if it's an excellent driver) was not the originally in that enclosure or for that plan. Even a cheap Emminence Kappa 15LFA performs better in that box, up to 3 dB more in the complete usable range of the subwoofer!
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It's not a 'clean' tuning, that's not possible with these drivers. The Celestions are good drivers but they can't perform well in that enclosure.
Where do you set the lowcut?
That should be fine.
Bad speaker design.
Generally the wrong combination of enclosure, tuning and drivers. You can recognize a non-clean tuning by simulating or measuring it, if the curve is malformed, got a dive and then a bump at the lower end or a bump at the upper bass.Generally, for pa-speakers, a little decline at the lower end is preferred because the power compression will hit at the fs and it will sound cleaner even under power compression.
Could you please describe your complete signal chain from source to the speakers?
That should be fine.
Bad speaker design.
Generally, for pa-speakers, a little decline at the lower end is preferred because the power compression will hit at the fs and it will sound cleaner even under power compression.
Could you please describe your complete signal chain from source to the speakers?
Source is a range of microphoness and DI boxes on stage, with microphones used for drums instruments and vocals, these are connected to an Behringer X32 mixer, then to a DBX speaker controller, then to a Behringer inuke then to the subs
I don't think it's the design itself, though the rear chamber looks quite a bit larger then you would want it/ need it. The chain does look normal to me also (though it isn't my field of expertise), so I would suspect the driver or the construction.
Have you reversed the polarity on one of the drivers? I've had some factory units that were wired wrong to the connectors and your problem sounds like it could be an out phase issue. So even though they look like they're of the same polarity now, it might actually be the opposite.
Second issue I would address: Are you using bolts and t-nuts or screws to mount the drivers?
Best regards
Have you reversed the polarity on one of the drivers? I've had some factory units that were wired wrong to the connectors and your problem sounds like it could be an out phase issue. So even though they look like they're of the same polarity now, it might actually be the opposite.
Second issue I would address: Are you using bolts and t-nuts or screws to mount the drivers?
Best regards
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nope no feedback, I have the same issue wile playing recorded music.
It's a strange sound, certain kick drums set it off as they are tunes to the same frequency....If I use a parametric with a narrow Q at about 70Hz can notch it out then the sub works much better..in fact it transforms it as it can then handle much more power an becomes much louder.
I think I will just experiment by firstly lengthening the ports across the back wall of the speaker and if that does not help I can make the port area wider plus add more port length.
Yes, but he didn't state 'how' he checked. Maybe he just checked if the connectors were the same colour/ sign, which doesn't address polarity persé. That's why I'm interested how he checked.
Apart from the semantics I could say I'm kinda of an expert on this specific design. Having had feedback of 100-ths of people, walking into similar problems, as described by the TS.
In most of those cases it reverted back to driver or construction related issues.
Just trying to help
Best regards Johan
well he has the drivers as a result of buying the box and he's not happy with what it's doing and is looking for direction on understanding why it's wrong,and potentially sort out a workaround or fix.
i wish i was more proficient at using Hornresp to help out.
i think it would be easy enough to cut panels oversized just enough to be snug fitting and see if the port tuning can be lowered (i still favor extending the panels to form more of a tapped horn)
if the current shape fails at being either a bass reflex or a bass horn i would attempt to modify it to become one or the other.
i wish i was more proficient at using Hornresp to help out.
i think it would be easy enough to cut panels oversized just enough to be snug fitting and see if the port tuning can be lowered (i still favor extending the panels to form more of a tapped horn)
if the current shape fails at being either a bass reflex or a bass horn i would attempt to modify it to become one or the other.
That is the exact description of how a feedback starts. A feedback can also be created by a mechanical resonance of a part. That could be a DI box or ground lift (audio transformer), old reverb also some other mechanical parts.
Are any parts of the chain in close to medium proximity to the subs? The amp rack, stage box of the x32.. ? If it starts fairly normal and gets louder in any way without a feedback it is absolutely impossible it's the subwoofer by itself. The speaker can not create more power, that is impossible by the laws of physics. You can likely see the power gain on the VU-meters of the amp or maybe other parts of the chain.
No, that will not help you in any way. You have to systematically inspect and exclude each part of the chain. That can be done in different ways, by exchanging or removing parts of the chain, by shortening the chain, moving things apart from the subwoofer (or the other way around, moving the sub somewhere else). It could also be a problem of the settings of the x32, it allows free routing, filters, external effect units (send/return or could also be the effect units itself) ect.
A rocker you say... You simply must try one of these: Single sheet TH challenge
Load it with one of those drivers and see if you like it. If you do (and I predict you do) build more or reinstall the driver and sell the cabs to fund some higher xmax drivers. I can help you sim them to ensure they work.
BTW who built that cab/what model?
You simply must try one of these: Single sheet TH challengeLoad it with one of those drivers and see if you like it. If you do (and I predict you do) build more or reinstall the driver and sell the cabs to fund some higher xmax drivers. I can help you sim them to ensure they work.
BTW who built that cab/what model?
They are indeed indeed....unfortunately I am the not so proud owner of eight of them.
I new there had to be a reason for them costing less than the price of the two divers in each!!! They retail at over £1200 each...but monocor were selling them for just £350 each.....Hmmm...perhaps I now see why.
Hey....How did you find out the designers name...perhaps I could contact him?
The Celestion are sold for 200 - 300$. And I have to repeat myself, it's not the fault of the subwoofers. Do the troubleshooting I proposed. Use i.e. a DJ-mixer instead of the console as a source and play the same music to exclude all the inputs, routings, settings, effects, monitors, inserts, talkback etc of the console at once. If that still happens, move and replace the other parts of the chain.
How did I find the name? My Google-Fu is better than yours!
You can reach him by calling Monacor Germany Bremen and ask for him, he still works there. But he will tell you exactly the same, Feedback. And he will ask you to do the same troubleshooting steps, so there's no need to call across half of Europe just because you are too lazy to test the subject yourself. Don't be mad because you don't get the result by not doing the work it needs.
Is the box braced internally? Perhaps one of the braces is loose. Or maybe the terminal cup is leaking. Or maybe one of the panels has become slightly unglued - that happened to me with my POC3.
I suggest running an impedance curve test against the sub to see if there is an unexplained blip in the curve at 70 Hz, which would be another sign of an issue with bracing or leakage. Also, if you feed it a pure tone around that frequency, it could help you locate the source of the noise more effectively.
Are you kidding? He doesn't even want to touch the signal chain, what gives you the idea he'd do actual work by measuring them!
Besides I strongly doubt that happened on all of the subs.The Celestion are sold for 200 - 300$. And I have to repeat myself, it's not the fault of the subwoofers. Do the troubleshooting I proposed. Use i.e. a DJ-mixer instead of the console as a source and play the same music to exclude all the inputs, routings, settings, effects, monitors, inserts, talkback etc of the console at once. If that still happens, move and replace the other parts of the chain.
How did I find the name? My Google-Fu is better than yours!
No problem...just made it easier.....I went to my unit and set up the same system but used some different subs that I have....they do not have the same problem....!!! chain analysed!!!
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