Many thanks for the info, I will try to do the impedance curve.
I will also try applying the specific signals.
That's not an error analysis. The other subs have probably less spl or provoke the feedback at another frequency, so don't be surprised if that happens again with different music. But since you are too lazy and don't want to learn what's really going on, I'm out, again a huge waste of time for some ignorant bloke.
I am sorry , I am a little confused, I really appreciate your help, I do not understand your animosity. I will do exactly as you have suggested, I have a small analogue simple mixer that I can use instead of the X32 ..do you think this will be OK?
Plus I am going to attempt to do the impedance curve....I will also do a frequency response curve.
Yes, OK I will try it, I could use REW and try to get a response curve as I have a reference microphone.
I will try to do the impedance but I am not very confident about it and I am worried about damaging something, I will have a go though
The reason I ask is because I seem to gather from your posts, that the problem arises as power is increased to a certain point?
Typical for this design is an excursion maximum between 60 - 100 Hz. Around the lower excursion minimum you've placed a high pass, so if you place EQ around 74 Hz, you're effectively controlling the maximum excursion the driver will make. The average excursion with EQ is lower, so you can now increase the power quite the bit, until the average excursion becomes as high as the maximum excursion without EQ.
If air is starting to escape around a certain excursion mark, it can make a sound as if you're wrecking your driver. Other minor excursion related problems can give that same impression.
So if this does make sense to you, we could look into that.
Johan
Typical for this design is an excursion maximum between 60 - 100 Hz. Around the lower excursion minimum you've placed a high pass, so if you place EQ around 74 Hz, you're effectively controlling the maximum excursion the driver will make. The average excursion with EQ is lower, so you can now increase the power quite the bit, until the average excursion becomes as high as the maximum excursion without EQ.
If air is starting to escape around a certain excursion mark, it can make a sound as if you're wrecking your driver. Other minor excursion related problems can give that same impression.
So if this does make sense to you, we could look into that.
Johan
I doubt you will need REW for what I'm suggesting....which is listening for obvious defects on a sine by sine basis.
No problem, I wont be able to do his until next week now but I will get back to everyone then
Hi mikeydude, I'm posting to my post because I gave some bogus advice...
I just noticed the x-32's signal generator is too coarse in its resolution to be of value, going sine by sine. But REW's generator would work great.
I do this for testing speakers... and room or stage resonances too. Sine waves pinpoint what's squawking real quick...
Thanks I will do this next week, we have had really bad weather here which stops me getting to the unit where the speakers are stored
Well, if it's excursion related, there are 3 main culprits, the design, the construction or the driver. As it's a commercial design, that doesn't look like it has really major flaws, I would assume for now that it's either the construction or the driver.
If you have 2 other 15" drivers that you could mount in the enclosure, you can test if it's driver related or not. If you use different drivers and the problem remains, it's likely construction related.
Also, how much excursion peak to peak, would you say the driver is making, when the driver moves uncontrollably? Some low budget drivers can loose control of the cone very fast beyond the Xmax, so if it's 10 - 15 mm peak to peak, you could already be in that zone with these drivers.
Construction wise, there is multiple possibilities. Though often it's either something inside the enclosure, that starts to move/ vibrate or air that starts to escape, when the excursion gets beyond a certain point. I would inspect the cabinet (and drivers), inside and out for any defects. You can press the cone of the driver, with your fingers evenly spread around the dust cap, to check the voice coil and suspension. You can slightly wet your finger, to feel if there's any unwanted draft (when testing), don't forget to check the connections on the back.
Sometimes the baffle is slightly warped, so air can escape between the driver and the baffle, when the pressure inside the (rear)chamber gets high enough. Sometimes people just don't use enough force when tightening the bolts (and many even don't seem to realise it).
Personally I always advise people to use a (~3 mm) compressible draft strip (full circle) between the driver and the baffle and to tighten the bolts really tightly (going in 2 or 3 circles around all bolts). My favourites for this job are steel Allen hex Bolts (not stainless steel), with an Allen key or better, a ratchet wrench.
Well, these are the problems I most often encounter, could be something else though. Let's hope it's not
Johan
If you have 2 other 15" drivers that you could mount in the enclosure, you can test if it's driver related or not. If you use different drivers and the problem remains, it's likely construction related.
Also, how much excursion peak to peak, would you say the driver is making, when the driver moves uncontrollably? Some low budget drivers can loose control of the cone very fast beyond the Xmax, so if it's 10 - 15 mm peak to peak, you could already be in that zone with these drivers.
Construction wise, there is multiple possibilities. Though often it's either something inside the enclosure, that starts to move/ vibrate or air that starts to escape, when the excursion gets beyond a certain point. I would inspect the cabinet (and drivers), inside and out for any defects. You can press the cone of the driver, with your fingers evenly spread around the dust cap, to check the voice coil and suspension. You can slightly wet your finger, to feel if there's any unwanted draft (when testing), don't forget to check the connections on the back.
Sometimes the baffle is slightly warped, so air can escape between the driver and the baffle, when the pressure inside the (rear)chamber gets high enough. Sometimes people just don't use enough force when tightening the bolts (and many even don't seem to realise it).
Personally I always advise people to use a (~3 mm) compressible draft strip (full circle) between the driver and the baffle and to tighten the bolts really tightly (going in 2 or 3 circles around all bolts). My favourites for this job are steel Allen hex Bolts (not stainless steel), with an Allen key or better, a ratchet wrench.
Well, these are the problems I most often encounter, could be something else though. Let's hope it's not
Johan
Both the hexagonal shape in the bolt head and the thread of stainless steel bolts tend to wear out quicker than galvanised steel (a process known as galling). This is especially true, if the entrance angle isn't ideal (diy-situations), or when using a lot of force when tightening the bolts, or just over time.
Apparently stainless steel bolts can not be hardened to the same degree as regular steel. As galling is friction related, anything that reduces friction reduces galling. As there isn't a real advantage of stainless steel bolts over regular galvanised steel bolts when securing drivers in the enclosure, personally I would avoid them.
Johan
Apparently stainless steel bolts can not be hardened to the same degree as regular steel. As galling is friction related, anything that reduces friction reduces galling. As there isn't a real advantage of stainless steel bolts over regular galvanised steel bolts when securing drivers in the enclosure, personally I would avoid them.
Johan
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.