Sub Crossover. How is the wiim setting the slope and crossover points?

[mattzildjian]

Hi all,

I have been tweaking my sub settings and I noticed that there is a vast difference in sound between using the built in crossover, vs sending a full range signal to my sub and using my subs low pass filter at the same crossover frequency.

Does anyone know exactly how the wiim crossover setting is operating? And at what slope?
Perhaps setting a crossover in the wiim at 80hz, is actually doing something more complex, like sending 75hz to sub and 85hz to mains in order to reduce overlap?

I have an SVS SB1000Pro with precise control for low pass filter frequency and 4 slope options, 6db, 12db, 18db, 24db.

Thanks!

Note: I encourage anyone using a sub to try this for yourself, set your subwoofer to use it's low pass filter at the same frequency as the wiim is set to, and then send full range to the sub (using subwoofer bypass mode) and see how different it sounds. For me the difference is huge and I am not sure why.

 

[adias]

Using a WiiM Sub Pro with a WiiM Amp Ultra I set it as:

Sub

Crossover 75Hz
Level 6dB - main speakers dependent
No Sub RoomFut



Amp Ultra

Eq - High Pass filter set at 35Hz
No RoomFit



RoomFit is also an option.

 

[slartibartfast]

Hi all,

I have been tweaking my sub settings and I noticed that there is a vast difference in sound between using the built in crossover, vs sending a full range signal to my sub and using my subs low pass filter at the same crossover frequency.

Does anyone know exactly how the wiim crossover setting is operating? And at what slope?
Perhaps setting a crossover in the wiim at 80hz, is actually doing something more complex, like sending 75hz to sub and 85hz to mains in order to reduce overlap?

I have an SVS SB1000Pro with precise control for low pass filter frequency and 4 slope options, 6db, 12db, 18db, 24db.

Thanks!

Note: I encourage anyone using a sub to try this for yourself, set your subwoofer to use it's low pass filter at the same frequency as the wiim is set to, and then send full range to the sub (using subwoofer bypass mode) and see how different it sounds. For me the difference is huge and I am not sure why.

The slope of the WiiM LPF is 24dB/octave. Do you still have the main speakers high passed by the WiiM crossover?

 

[harkpabst]

The slope of the WiiM LPF is 24dB/octave. Do you still have the main speakers high passed by the WiiM crossover?

And a 4th order Linkwitz-Riley filter means that the level of each source (mains and sub) is down by 6 dB right at the crossover frequency to get a flat summation.

Other filter slopes and filter types have different requirements. With a 3rd order Butterworth high pass and low pass the individual levels must be at -3 dB for a clean and flat summation of output signals.

Using both, the sun's built-in crossover and the WiiM crossover at the same time is exclusively for those owning the appropriate measuring equipment and knowing how.to use it. In most cases it will simply degrade the performance. A few more complex edge cases could benefit not using the WiiM low pass filter but adjusting that of the sub, based on hamds-on in-room measurements.

 

[mattzildjian]

The slope of the WiiM LPF is 24dB/octave. Do you still have the main speakers high passed by the WiiM crossover?

Yes I am still high passing the mains.

And a 4th order Linkwitz-Riley filter means that the level of each source (mains and sub) is down by 6 dB right at the crossover frequency to get a flat summation.

Other filter slopes and filter types have different requirements. With a 3rd order Butterworth high pass and low pass the individual levels must be at -3 dB for a clean and flat summation of output signals.

Using both, the sun's built-in crossover and the WiiM crossover at the same time is exclusively for those owning the appropriate measuring equipment and knowing how.to use it. In most cases it will simply degrade the performance. A few more complex edge cases could benefit not using the WiiM low pass filter but adjusting that of the sub, based on hamds-on in-room measurements.

This seems to make a lot of sense, when I bypass the wiim crossover and use the subwoofer LFP at the same frequency, I get a sizable boost of gain at the crossover region.

According to Wikipedia
Fourth-order Linkwitz–Riley crossovers (LR4, LR24) are currently the most commonly used type of audio crossover. They are constructed by cascading two 2nd-order Butterworth filters. Their slope is 24 dB/octave (80 dB/decade). The phase difference is 360°, meaning the two drivers appear in phase, although the low-pass section has a full period time delay.

2 questions based on this new information:

1. What type of crossover does the SVS SB1000Pro subwoofer use? I may contact them to find out.
2. If I am to be bypassing the wiim subwoofer crossover and using my own subs LPF, should I be setting the subwoofer phase to 360° as mentioned by the wiki information on 4th Order LR?

Thanks!

 

[harkpabst]

What type of crossover does the SVS SB1000Pro subwoofer use? I may contact them to find out.

They are the ones to ask, indeed.

If I am to be bypassing the wiim subwoofer crossover and using my own subs LPF, should I be setting the subwoofer phase to 360° as mentioned by the wiki information on 4th Order LR?

Any phase adjustment on the subwoofer (usually I lay ranging fro 0⁰ to 180⁰) can only add further delay. The 360⁰ phase shift is a characteristic, not really a problem that needs solving.

Why would you want to use the crossover in your sub at all? I would just set the sub to LFE and use the WiiM subwoofer management.

 

[mattzildjian]

Why would you want to use the crossover in your sub at all? I would just set the sub to LFE and use the WiiM subwoofer management.

Because the wiim subwoofer output is low in level, and SVS subs have an always active noise gate / input threshold. If I listen to audio at a low level, the sub stops playing because the input signal is too low to overcome the noise gate.

I have already added a Y splitter to add 6db of gain, and I'm boosting the sub output level on the wiim (though I don't want to do this too much as it reduces preamp headroom), and yet still, in some scenarios, the sub will not have enough input to activate.

Sending a full range signal to the sub is sending more voltage and therefore more likely to overcome the noise gate in more situations, so this is where I am at.

 

[harkpabst]

I see. What WiiM device are you using? What other components make up your system?

... and I'm boosting the sub output level on the wiim (though I don't want to do this too much as it reduces preamp headroom), and yet still, in some scenarios, the sub will not have enough input to activate.

I wouldn't be too much concerned about this. Have you actually tried it? The subwoofer output has its very own DAC.

 

[mattzildjian]

I see. What WiiM device are you using? What other components make up your system?

Wiim Amp
Elac DBR62
SVS SB1000Pro

I wouldn't be too much concerned about this. Have you actually tried it? The subwoofer output has its very own DAC.

I did contact wiim directly via a support ticket and they said that boosting the sub output is ok as long as I don't go over a certain volume level to avoid distortion, which clearly suggests that boosting sub output is reducing headroom. I tried to get a clarification on this as I felt there could have been a misunderstanding, but they came back with the same response.

I currently have the sub output boosted a few db, but since it could be removing headroom, I really want to avoid doing that.

 

[EddNog]

Even if the sub is set to exactly the same slope and filter type on the low-pass filter as the WiiM's (24dB/Oct Linkwitz-Riley), using one and then the other will likely result in different results because of speaker to subwoofer sync. When you use the WiiM's low-pass filter, the filter is applied before the sound is sent to the sub. When you send full-range from the WiiM and then use the sub's low-pass filter, that filter is applied after the sound is received and then processed. There is a short delay due to DSP on SVS subs (on average about 7.2ms, but it varies from model to model) and also the speaker to sub sync function of the WiiM applies its own alignment adjustment. However, the alignment is never perfect because the mic that WiiM uses for the speaker to sub alignment is inside the WiiM and not the mic in your phone which is at the main listening position and would be the correct one to use for synching speakers to sub if WiiM would do the damn thing right.

Try one, then try the other, use the one that gets the best result. Or if you have the option and cables that are extremely long, place the WiiM at the main listening position, perform the speaker to sub sync, and that should get you as close as possible to the right sync at least, then compare the two methods again.

-Ed