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In Reply to: RE: What do you make of this? (Impedance curves) posted by Mr_Steady on March 13, 2017 at 17:25:00
Well, going my own way is like an challange for me.
To see what I can accomplish myself with my own ideas.
Today, at least I got ARTA/Limp up and working.
Here are the shart from that measure.
Go for it.
At least now you have a mark to aim for, and maybe a fallback position.
Big speakers and little amps blew my mind!
From wthat I have seen on the web, these curves isīnt so bad.
Especially from mid and up ;o)
Actually it is the low freqences that concerns me.
But are those peaks only adjustable electrically, or is there ways to correct them acoustically?
I know that my bass woofer has a slightly wrong Vas for the Karlsson K-15 cab, And I plan to open it upp to add more wool inside.
Could those abnormalies indicate that the BR-port to be increased/decreased while I am at it?
So your graph is an acoustic measurement of your speaker for impedance and phase? I thought is was an electrical measurement of your dividing network.
It may not look bad, but it doesn't look that good either. I suggest you search online for the impedance plot of the Klipsch AA network. I think it will look a lot like yours. The impedance spike down low is what screws up the bass output from a SET amp. That peak is what you want to get rid of. I think you will have to fix it in the electrical realm before you start to try to tweak it in the acoustical realm. Maybe you should take some electrical measurements of your network with a resistor in place of the woofer.
Sorry Pix I am not an expert, and I can't answer any of your questions about bass enclosures, drivers, and ports. There are a lot of people on this forum who know much more about that than me. Hopefully they will chime in. I do know enough to recognize that your woofer is putting out significant sound a decade past your crossover point which can't be good.
I see you accept emails. I may have the schematics for the crossover I showed you on an old computer. I may be able to retrieve them, and may be able to forward them to you if maybe you were interested in them, and maybe if you agreed not to share them with anybody else. That's a lot of maybes, so I'm not making any guarantees. Let me know if your interested.
Big speakers and little amps blew my mind!
The measurements is purelly electrical.
The initial one where made manually with a signal generator, a reference resistor and two DVMs. The second, where made with ARTA/LIMP with my computer/soundcard. The similarity then between, strengthen the fact that the measurement where correctly done.
I am a novice in this measure acivities, and not qualified to state what causing that hugh 20Hz peak. My thought where that the cabinette could generate some sort of woofer resonance generating back EMF?
I will try replacing the woofer with an 8 ohm resistor to see what happend.
Those filter schematics would be very much appreciated :o)
I am not sure how to link to several pictures in one post, so I add three separate posts.
First, I have measured the impediance of the complete speaker ones again. But this time from 10Hz upp to 20k.
This was just to make sure that the rising impedans low end cuve actually was a hugh peak. And it was.
Actually, I donīt see this 21Hz peak as a problem, since the Karlson K-15 doesīnt play that low. But as a second thought, a peak of this size must come from some sort of resonance fenomena (back EMF), and hence needed to be tamed.
This was what I ment with acoustically corecting whatīs been seen in my impedance measures.
Since mu bass woofer has a fairly low Q-value, I donīt recognise the transducer itself to resonate, but in combination with the K-15 cab, it propably does.
Could more wool inside the cab help? or could I decease the vent to lower the fb to even those two peaks ?
Next I wanted to replaced the bass woofer with a power resistor (wirewound).
But just to make sure the resistor itself did not caused any inducive phaseshift I first hoked it up to ARTA/Limp
As you can see the resisor measure a fairly straight line, which is good.
Finally, I measured the speaker impedance with the wirewound resistor instead of the bass woofer (the filter intact) and the lines looks allmost as good as the ones you showed me earlyer ;o9
The slight stepp upp below 350Hz is probably caused of the wirewound resistor, being 10 Ohms and not 8.
Clearly all those valleys and peaks are all gone, so the abnormalies must derive from the bass woofer/cab
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