Hi, I didnt know if I should ask here or at Multi Way but you dudes that are into subs might know. So I have done some repositioning of speakers and listening position etc and listening and measuring, trying to understand what happens. I have come up with a placement that suits me fairly for my LP and the speakers. It sounds ok, still doing tweaking with speaker stuffing (its TQWT) that changes things quite alot. Lately I have also added two subs that are placed ca 1,5 m in front of the speakers. I assumed that I will have to run those thru a dsp because of likely phase disalignment with the speakers woofers. But It doesnt sound or measure as I will have to.
The system is analog but actively crossed at 1000 hz, and I feed the subs with an extra buffer that I have tapped from the LF outputs on the active x-over, so they have a 20-1000 hz signal. The main speakers has a fairly good respons down to abt 40, than they fall pretty steep. So I turned the local low pass button on the subs all anticlockwise to lowest lowpass fq, hoping that they will cut over 40 or so. And maybe they do but not very steep, as seen in measures.
But, now to my main poll. Do you agree that it doesnt look like I have a big problem with phase woofer/subs, so maybe I can skip the dsp and work with some sub eq instead?
Lower is speakers only, both channels, upper is with subs added.
The system is analog but actively crossed at 1000 hz, and I feed the subs with an extra buffer that I have tapped from the LF outputs on the active x-over, so they have a 20-1000 hz signal. The main speakers has a fairly good respons down to abt 40, than they fall pretty steep. So I turned the local low pass button on the subs all anticlockwise to lowest lowpass fq, hoping that they will cut over 40 or so. And maybe they do but not very steep, as seen in measures.
But, now to my main poll. Do you agree that it doesnt look like I have a big problem with phase woofer/subs, so maybe I can skip the dsp and work with some sub eq instead?
Lower is speakers only, both channels, upper is with subs added.
Yes, when i get home, went for s beer 😉
It largely follows the curves except it reverses one dip partially cancels it.
I was also thinking of adding a pole to the active filter and Low Pass it from 40 with 24db/oct for the subs but looking at this I think the speaker woofer and the sub does good together also above that.
It largely follows the curves except it reverses one dip partially cancels it.
I was also thinking of adding a pole to the active filter and Low Pass it from 40 with 24db/oct for the subs but looking at this I think the speaker woofer and the sub does good together also above that.
So here is a graph with only the subs also. Sorry for the dB scale, I tuned for 75 dB and it gets higher when I run 20-300 Hz only. 40 and 70 are lengtht-with room nodes that I will have to eq, above that I can probably do room treatment for.
The back wall one quarter wavelength reflection (speaker-boundary interference) at 1.5 m may be causing some of the peaks and dips. Can't EQ back the phase cancellation frequencies like the one at 85Hz.
http://arqen.com/acoustics-101/speaker-placement-boundary-interference/
There is a link to a 2d wall bounce calculator there.
Thanks for the link. Do you find my measurments problematic or should I just move on to building some decent amps?
It all sounds quite complicated. Generally speaking adding a sub shouldn't just add more bass but it should make the whole set up sound glorious, unrestricted. Based on personal experience and talking to those who have experimented with me this seems to happen best with high pass limited mains and well integrated subs. It doesn't do so well with full-range passed to the mains, or an attempt to use very low high pass filter settings.
In several cases, adding a HP filter to the mains so they cross around 80 Hz always seems to improve the sound quality coming out of the mains. Also, if your mains are ported it is worth considering sealing them for better integration.
In several cases, adding a HP filter to the mains so they cross around 80 Hz always seems to improve the sound quality coming out of the mains. Also, if your mains are ported it is worth considering sealing them for better integration.
Your measurements don't look unusual. If you are happy with their response, no problem, move on..
The thing is that back wall sbi was the reason I’m doing this. The livingroom where I am listening to music is in file with the dining room giving it a total lenght of 7,4 m. With those big speakers at the end of the livingroom wall I hardly got any base at all. One day when I was fixing with furniture I temporarily placed the speakers like 3 m from the back wall. And mama, what a base I had 🙂
But I couldnt have it like that, I had to sit at the dining table listening to music 🙂
One day my ex was over and sweepingly said, why dont you put your big ugly speakes in the middle of the room so you can have some nice chairs and stuff in the livingroom?
At first I thought she was silly as usual but when she had left I tried, sneaky me 🙂 And It worked! I had good balance in the music.
Problem was, or is, I dont want the turntable and stuff in the dining room. So I had to make a decision. Like 13 m long speaker cables nailed to the walls, or 13 m signal cables and amps by the speakers? I went for the later. That ment I had to go from single ended to balanced and I since I’m a nerd and build everything myself I had to rebuild my entire audio chain.
So the speakers now is like 3 m from the dining room back wall and my LP is in a cosy chair at the end of the living room wall. And as you can see on the graphs, I have base and decent balance. Things to work on? Yes. But it is workable. It wasnt before.
The 40ish peak is the half wave of the total length probably combined with full width (3,6 m) and and 70 third of length and first floor-ceiling (2,35 m). Nothing to do about that but try easing it out with some eq and room treatment where I can.
About adding x-over filters: Those who knows knows that adding x-overs means adding components to the audio chain. Components that will affect the music. They might add some noice and they might alter the phase. I never add components when it is not necessary.
So now I came to the conclusion, with your help 🙂 I wont add components that I dont need.
Thanks!
I used the formulae for back wall sbi for the main speaker. The distance from cone to wall is 3,16 m. This may explain the fairly drastic fall off under 40 for them. Been wondering about that since they are tuned for Fs 38 Hz
Fs is a driver's free air resonance. The driver's resonance rises from Fs to Fc in a sealed box.
Response generally falls at -12dB per octave below Fc.
The frequency of a ported box tuning is called Fb. Below Fb response generally falls at -24dB per octave, very little output below Fb as the port output transitions from 90 degrees to 180 degrees out of phase from the driver.
Just from the graphs posted I would try a 2nd order highpass on the main speakers at approx 40Hz, and a 4th order on the mains at approx 40Hz. (aiming for a 40Hz LR type crossover)
Rob
Rob
Rob did you mean 4th order lowpass on the subs by any chance? Care to evolve why you are suggesting this?