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How do you set your high/ low pass filters, for sub speaker integration?

My adventures in stereo

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I have been setting my low pass & high pass values to 80 hz -12 db on my minidsp systems
Noticed that on measuring through REW, this value causes a significant loss of gain from 50 to 150 hz, compared to unfiltered curve

I played around with values, setting high pass to 80 hz at -6 db and low pass to 50 hz at - 6db
Gave me the least destructive result

So my recommendation based on the above is not to blindly, set your high pass & low pass to the default 80 hz, measure & tweak instead

My gear

minidsp SHD, REW for measurements
Nad C 298 power amp
Revel M 126 Be
SVS PB 2000 Pro x3
 

sigbergaudio

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It's very natural that you get less energy when you apply a highpass filter to your speakers and lowpass filter to your subwoofer, that is the intention. The reason for this is that when both the subwoofer and the speakers play the same frequencies at full energy, you will usually not get a good result.

You'd typically want them to meet at the same point with the same attentuation so that they sum to a flat curve. Choosing the same frequency and the same roll-off curve (12dB or 24dB) for both the speakers and the sub will in theory achieve this, if the level of the speakers and the subs are the same. Often we want a rise in the bass / sculpt a slope, which can be achived by the gain of the sub being higher than the speakers, and/or overlapping the frequencies a bit.
 
OP
My adventures in stereo

My adventures in stereo

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Thanks for the reply

It was after reading Geddes Recommendations, that I started looking at changing the setting of high & low pass filters
He suggested no low pass filter & a very shallow high pass filter

Since My mains dont go below 50 hz, I crossed it off at this point
The subs , I left at 80 Hz with a shallow high pass filter with a roll off of - 6db

The curves look good and the music sounds enjoyable
 

HarmonicTHD

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Thanks for the reply

It was after reading Geddes Recommendations, that I started looking at changing the setting of high & low pass filters
He suggested no low pass filter & a very shallow high pass filter

Since My mains dont go below 50 hz, I crossed it off at this point
The subs , I left at 80 Hz with a shallow high pass filter with a roll off of - 6db

The curves look good and the music sounds enjoyable
You would need measurements to really tell whether it was “successful “ ie smooth FR.

As @sigbergaudio wrote, eg closed speakers roll off at 12dB/Oct so you applying 6dB potentially does nothing as the speaker (sub) rolls off “quicker”.

Choosing different x over frequencies might or might not work. Usually it is easiest to choose the same x over and apply 12 or 24dB/Oct (closed/ported) so both speaker sum up correctly to a flat response. Again only measurements can tell.

Do you have a UMIK1 and REW measurements you can share?
 

ZolaIII

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@My adventures in stereo I think you are mixing what is what. So you didn't apply anything to speakers and you set a low pass for sub's at 80 Hz 24 dB/octave.
Reason to use high pass is usually to get stress of the speakers (amplifier and harmonics) as they don't do bottom low frequencies then (in which harmonics are strongest and it needs more power). And you do low pass on subs because they don't do lower mids and anything up really good.
Kinda hard to believe that three sub's can't fill the holes.
Would be good to see your measured response plots individually (speakers/sub's) and together.
Edit: including setup picture (placement) and room description (size and such).
 
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OP
My adventures in stereo

My adventures in stereo

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I will post the measurements

Currently have set the mains to 50hz low pass at 6db roll off
my mains are revel 126 be ported speakers

The subs are crossed over at 80 hz, 6db roll off
 

ZolaIII

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Well you're speakers are @ - 6 dB already at 54 Hz which is reference crossing point regarding Linkwitz Riley. So high pass doesn't do much if anything. However problematic regarding crossing is 2 dB hump @ 200 Hz (from 100 to little over 300 Hz) they have so you should peek PEQ it before doing a crossover.
You should do a calibration to 83 dB reference white noise point for speakers, and let a sub's go +4 dB over that croos them and similar hump but lower should appear from the sub which you again level down with peek PEQ for the sub or on them (their embedded PEQ) really as you like. And not to be flat but to have a little bit of bump in low bass.
 

HarmonicTHD

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I will post the measurements

Currently have set the mains to 50hz low pass at 6db roll off
my mains are revel 126 be ported speakers

The subs are crossed over at 80 hz, 6db roll off
1oo % what @ZolaIII said above.....

Plus you are confusing low and high pass. The mains need to be high passed, so the high frequncies "pass" through and the sub need low passing.... both at least -12db/Oct as -6 dB/Oct as in your case wont do anything (in simple words).

Until you have learned more, I would just pick 80Hz as a cross-over and low/high pass both mains and sub with 24dB/Oct (as they both seem to be ported... if not please correct me). Your current approach, is more likely to make things worse.

But looking forward to your measurements..... if possible please provide a) without DSP, b) with DSP and set y axis from 50 to 100dB and smoothing to either VAR or 1/12.
 

sigbergaudio

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Thanks for the reply

It was after reading Geddes Recommendations, that I started looking at changing the setting of high & low pass filters
He suggested no low pass filter & a very shallow high pass filter

Since My mains dont go below 50 hz, I crossed it off at this point
The subs , I left at 80 Hz with a shallow high pass filter with a roll off of - 6db

The curves look good and the music sounds enjoyable

Not everyone agree with everything Gedde recommends. :) Recommendations with regards to subwoofers can also change drastically depending on whether you employ DSP/EQ or not.
 
OP
My adventures in stereo

My adventures in stereo

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I use REW with minidsp SHD, and use a 6 db Harman house curve

With 6db roll off on mains ( crossed over at 50 hz) and subs ( crossed over at 80 hz)

20230226_171051 6db roll off.jpg


With a 24 db BW filter for both mains and subs, mains crossed over at 60 hz & subs at 80 hz
20230226_185004 24 db roll off.jpg


Mains only with no filters
20230226_185054  mains no sub.jpg
 
OP
My adventures in stereo

My adventures in stereo

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20230225_225034 mains crossover.jpg

mains cross over previous setting 50 hz 6 db roll off
20230225_224959 subs crossover.jpg

subs previous cross over setting, had subsequently changed it to 6 db roll off
 

sigbergaudio

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If you change the scale on the Y-curve so it's covers 50dB (for instance 45-105dB) it will be a bit more comparable to what's typically shared and easier to read.
 

ZolaIII

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I don't know how peak and peak @ 55 Hz can produce the 0? Selam you have room response peak at 55 Hz but I don't have explanation on above question. On the other hand result you are having set as it is is very good so I don't know why you complained in the first place.
 
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sigbergaudio

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Looks like freak luck that it got that good with no roll-off. :) Lean between 60-90hz, but otherwise pretty good.

Based on the graphs it looks like you should try crossing over to the sub at 120-130hz (12 or 24dB roll-off) if your subwoofer is located close to the speakers.
 
OP
My adventures in stereo

My adventures in stereo

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I don't know how peak and peak @ 55 Hz can produce the 0? Selam you have room response peak at 55 Hz but I don't have explanation on above question. On the other hand result you are having set as it is is very good so I don't know why you compiled in the first place.
Not really understanding your comment, kindly elaborate
Looks like freak luck that it got that good with no roll-off. :) Lean between 60-90hz, but otherwise pretty good.

Based on the graphs it looks like you should try crossing over to the sub at 120-130hz (12 or 24dB roll-off) if your subwoofer is located close to the speakers.
Should I just run them with no crossover :D
Two of the subs are adjacent to the mains, one is on the rear left hand corner
I can set the cross over at 120 hz for the two close subs and at 80 hz for the rear sub, with a 12 db roll off
will post measurements
 

ZolaIII

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Take a look at photos of mains only and sub's only. I wouldn't bother about crossing them higher if you don't want to use speakers with port's closed and then high pass slope should be 12 dB / octave. Anyway try it.
 
OP
My adventures in stereo

My adventures in stereo

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did a new calibration today

120 hz high pass for front subs with 80 hz for the rear sub 12 db roll off
eq ed flat to 200 hz

20230227_202406 120hz 12 db roll off.jpg

20230227_203200 with svs peq.jpg

SVS PEQ used to clean up dips in the 70 to 100 hz region
 

ebslo

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did a new calibration today

120 hz high pass for front subs with 80 hz for the rear sub 12 db roll off
eq ed flat to 200 hz
Interesting this still leaves a big suckout 70-130Hz just like with the mains alone. It seems the front subs are subject to the same room issues your mains have in this region, which shouldn't be surprising given they are in similar locations. This tells us that in your better-looking configurations above, the rear sub is carrying most of the load in this region.

Anyway, I do have some questions about how you are doing all this:
  1. How are the subs connected and how are the delays being managed? Your SHD has four channels but you are using five.
  2. Have you checked how your mains sum? I do this by comparing the mains RMS average to vector average.
  3. Same as 2 but for the subs? Do you use the REW alignment tool to set sub delays? Do you re-align the subs each time you change EQ filters or crossover settings as changing filters will change the alignment?
  4. Your no-rolloff configuration looks pretty good in overall FR, but since it seems the rear sub is contributing so much up to 130Hz, have you tried a low-frequency sound localization check? Try the sweeps here with mains only then with mains+subs to see if the subs are interfering with localization too much.
PS. The icon in REW just just above a plot's y-axis that looks like a camera is for creating images of plots. There is an option to include the key block, which is nice since it's really useful to see related plots overlayed on the same graph.
 
OP
My adventures in stereo

My adventures in stereo

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Interesting this still leaves a big suckout 70-130Hz just like with the mains alone. It seems the front subs are subject to the same room issues your mains have in this region, which shouldn't be surprising given they are in similar locations. This tells us that in your better-looking configurations above, the rear sub is carrying most of the load in this region.

Anyway, I do have some questions about how you are doing all this:
  1. How are the subs connected and how are the delays being managed? Your SHD has four channels but you are using five.
  2. Have you checked how your mains sum? I do this by comparing the mains RMS average to vector average.
  3. Same as 2 but for the subs? Do you use the REW alignment tool to set sub delays? Do you re-align the subs each time you change EQ filters or crossover settings as changing filters will change the alignment?
  4. Your no-rolloff configuration looks pretty good in overall FR, but since it seems the rear sub is contributing so much up to 130Hz, have you tried a low-frequency sound localization check? Try the sweeps here with mains only then with mains+subs to see if the subs are interfering with localization too much.
PS. The icon in REW just just above a plot's y-axis that looks like a camera is for creating images of plots. There is an option to include the key block, which is nice since it's really useful to see related plots overlayed on the same graph.

Thanks for the detailed, insightful reply, and for introducing certain new concepts to me :)
1. SHD 4 channels - 2 channels to the fronts, one to RT front sub, one to Lt Front sub, out from Lt sub to Rear Sub
2. Mains Sum - Not sure what this is & how to check
3. I use the REW alignment tool, as per Jeff Mery youtube video, have not realigned after changing eq filter & cross over settings ( not sure how to redo this, as the delay is already applied, in SHD)
4. I will try the sweeps you posted
 
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