How reduce distortion 500hz to 1000hz

[Pegaso]

Hi friends, I have two Faital 12 inch woofer for high efficiency two way speaker, well today I try same experiments to look the best performances.


I have seem that at 2700hz crossover point is good for tweeter Audax TW034. but when listen the piano the woofer distortion is a litle bit audible. The 12 inch Faital have 98db and I want to know your comment about how to reduce this distortion.

ideas:
1. coat the cone with epoxy resin to increase the weight in 50gr or more, I loose same db but now I use a resistor to match with the tweeter, at increase the structural resistance of the paper cone maybe reduce the distortion, but after do this step can not change to the original stage 🙂

2. put a plug similar to phase plug in the front of the centre cone, today I put high density foam plug around 14cm OD and the sound is better, I am sure that the distortion have been reduce, tomorrow I need to measure to see how change the response curves.

Ideas???

 

[sreten]

Hi,

Your problem is much more likely to be very poor x/o
design than any inherent driver fault that "needs" fixing.

rgds, sreten.

 

[Pano]

I agree. Your crossover is probably letting the rough areas of the woofer - and maybe the tweeter - get thru. Don't fix the drivers, fix the crossover!

 

[system7]

Usually about 2mH coil and 10uF shunt for this sort of bass filter. Tweeter 3.3uF and 0.3mH plus resistors for level. Where are you now?

 

[lousymusician]

Usually about 2mH coil and 10uF shunt for this sort of bass filter. Tweeter 3.3uF and 0.3mH plus resistors for level. Where are you now?

I think he's saying he has to attenuate the WOOFER down to tweeter level..

First step might be to assure that the crossover is addressing the baffle step (if it is not already). That should get the levels matched better.

The woofer can't be much good up to 2700 Hz. At the very least the dispersion would be nothing like that of a dome tweeter.

 

[anatech]

Hi Pegaso,
Consider making this a three way system. A 12" woofer isn't happy at 1 KHz, so a midrange unit that comes in about 600 Hz and out maybe 4,500 Hz - give or take as this is less critical. I'm not surprised a piano sounds off with this setup.

If you can find a dome midrange, something like what Peerless used to sell (do they still?). Failing that, use a good cone upper bass driver and roll that off closer to 3 KHz. As system7 suggested, a 12 dB per octave x-over would be the minimum.

-Chris

 

[system7]

I'm just fishing to find out what Pegaso is up to here. 🙂

This sort of thing might work with an Audax TWO34 waveguide and a 12" bass. Along with a mid:
DTQWT-mkIII

 

[Bare]

Do Not paint your driver.. easier to save time/effort by simply putting it into the trash bin IF that's your only alternate.
That driver "should' be Usable to 1200/1400 hz.
Adjust your crossover to suit it.

 

[Pegaso]

Sorry I don't explain correctly The graphic is only the woofer without crossover at 97db 1w 0.5m, I though that to have less that 1% at 97db 1w I is not bad for a two ways 12 inch and match correctly with the Audax TW034 but of course the sound is always improvable 🙂, I aprecite your opinion about how to reduce if is possible the 3rd harmonic distortion 500-1000hz

 

[scholl]

I use that woofer to 1600hz. I never measured distortion but it sounds great. If your in the US and want to sell it let me know. That is if it wasn't ruined with paint.

 

[5th element]

I'm guessing that's third order? Looks fairly normal for a driver with a more basic motor system.

 

[Pegaso]

Well after check many times with different reversible solutions without coated, that will be the last, I listen very clear the distortion at 900hz with the piano, compare with my other speakers 18w8531 at the same SPL the 18w8531 are very clear winner, without distortion audible to 2000hz.
When I use a beaming plug similar to
http://nexo-sa.com/images/category_geod_technology_3.jpg
this plug reduce a little but distortion is audible, I am very maniac with the right hand in the piano, I need to listen it very clear.
Now I have three ways:
1. reduce the crossover point from 2700 at 1400hz in first order to begin the drop at 500hz as Anatech said before, in the limit of the tweeter without distortion but need to change to 3rd order with more and bigger caps. ( price up)
2. Begin with the irreversible coated with epoxy ( only cone no surround) I think that the cause of the distortion is the structural deformed of the cone, normal in big and light cones. I begin the simulation in the structural simulation software to see where are the critical point. ( not important for price)

3. Change to other woofer as JANTZEN JA-8008 HMQ ( price in the same range that point one with the caps )

I appreciate your comments

 

[TBTL]

The crossover point must be way lower to avoid a mismatch in directivity. 1 kHz will be better. However, the tweeter won't handle that.

 

[Dissi]

The 3rd harmonic distortion plot of the Faital 12PR310 correlates nicely with irregularities in the impedance curve at 600 Hz and 1000 Hz. Many drivers suffer from a surround resonance in this frequency range. The resonance is often accompanied by elevated distortions. I don't think you can do much against it. Perhaps coating the driver helps, but the risk of ruin the driver is high as well.

3rd harmonic distortions close to 1% around 1 kHz are audible and are a problem. Once your brain begins to focus on them the fun is over.

AFAIK changing the crossover frequency doesn't reduce the distortions in the passband.