Roboklipsch's DIYSG 4cft ported build using Legacy EF 15" Driver

[RoboKlipsch]

Part Three:  Integrating the subwoofers together (Phase, Distance and Level)

1. Using REW and a UMIK-1, take a measurement of one of the subwoofers by itself.
2. Add a second subwoofer, and take a measurement of the response.
3. Adjust the phase of the second subwoofer.   Using an INUKE, this is flipping the phase 180.  Take another measurement.
4. Based upon the graphed response, use the phase setting that provides the better response.  It is usually VERY obvious which.
5. Add another sub, take a measurement.  Flip the phase, take another measurement.  Select the better response curve.
6. Once complete, the initial phase, distance and levels have been set.  
7. Take measurements at each listening position at this time, as reference for future measurements.
8. There are often sharp dips in the frequency measurements.  Before moving on to the next step, take some time here to carefully adjust the distance attribute for each subwoofer to achieve the best (usually meaning flattest) response possible at all the seating positions.  This process involves trade-offs.  If a change improves the response without causing harm, it is an improvement.  If it does not change the response, or changes the response negatively at one or more positions, do not make the change.  In some cases, it will dramatically improve the response at one listening position but harm it elsewhere.  Make a note of this change but don't implement it yet.  Test it again at the end of this process once the major improvements have been made.  
9. Adjust the distance by a foot at a time.  If it gets worse, go back.  It it gets better, change it by another foot.  Fine tune that improvement for that sub (say, getting down to the 0.1 foot), and once done, move on to the next sub.  Repeat the process until all of them have been adjusted.  
10. The subs are now adjusted for phase, level and distance.  

 

Part Four:  Running Audyssey

1. Run Audyssey as you normally would, using as many listening positions as you prefer.  I use as many as are offered, and if I don't need all the positions, take additional measurements at the ones used.  In my case, 2 at the center, 2 at left, 2 at right, and 1 each at LC and RC.  Microphone is close to ear level at the ear position, a few inches in front of and above the top/back of the couch.    
2. Adjust speaker sizes and at this time.
3. Add HPFs to each sub as needed.   
4. Crossover setting should be selected based upon a combination of measurements, room layout and speaker capability. Mine is actually set to 120hz, mostly due to room issues.   Speaker placement, listening position and room treatment can all help address this but it's beyond the scope of this process. 

 

Part Five:  Use PEQ to further optimize or smooth the response

1. Using PEQ to improve the response can be done quite easily.  Change one frequency at a time and measure across all the positions to see it's effect.  If it causes little or no harm and improves the response at one or more positions, it is acceptable.  If it causes harm at another position that matches or outweighs the benefit, it's best not to do it.  The more subwoofers you have, and the better their placement and calibration, the less PEQ that should be needed.  
2. PEQ is fine to use in your subwoofer setup.  Most guides suggest that PEQ be applied globally across all the subs the same -- same adjustments to same frequencies for each sub.   It is fine to make a small adjustment to one or more of the subs, but not all of them, if it makes a marked improvement in the response.  In the end, how it sounds is more important than how a response curve appears.

End of Steps!  

 

 

I will provide a detailed review of the new subs, and the 4 subs working together in future posts!  For now I'll get the new response curves up showing what 4 subs were able to do with what amounts to almost no PEQ. 

 

 

[RoboKlipsch]

39 minutes ago, CECAA850 said:

The theory is that nulls are sound waves canceling each other out at a certain spot at a certain frequency (the null).  All rooms have them as well as peaks.  Boosting nulls just uses amplifier power and all it accomplishes is that the waves cancel themselves out with more power.  Use the EQ to drop peaks.  I may not have explained it perfectly but you get the idea.  It's like speakers out of phase with each other, increasing the amplifier gain doesn't increase the volume.

With 2 subs, I found this to be the case and sometimes changed the PEQ on just one of them.  It was not a great solution but one that I thought was better than not using the PEQ. 

[RoboKlipsch]

Before and After Graphs 

 

Before (1st, 3rd and 5th graphs) showing best positions possible in room for 2 subwoofers, lots of PEQ to optimize all 3 seats to be as even as possible

After (2nd, 4th, 6th graphs) showing 4 corner position using 4 subwoofers and no significant PEQ to optimize all 3 seats to be as even as possible

 

 

 

 

 

 

 

 

 

[derrickdj1]

A room null is like a black hole.   The more power put into it, the more cancellation.  They can be addressed with an inverse filter which is not assesible to most of us.  I only set distance once.  Changing it in later calibration will effect a phase response somewhere else in the FR.  What you are shooting for is the best middle ground to land on.

[RoboKlipsch]

6 minutes ago, derrickdj1 said:

A room null is like a black hole.   The more power put into it, the more cancellation.  They can be addressed with an inverse filter which is not assesible to most of us.  I only set distance once.  Changing it in later calibration will effect a phase response somewhere else in the FR.  What you are shooting for is the best middle ground to land on.

i may try using the final distances that I tweaked and seeing how Audyssey deals with them.  My first theory was to give Audyssey what appeared to be one subwoofer (distance and level matched) so it could clearly work out its numbers.  When I tweaked the distances, it was done with trial and error and graphing to insure that the response elsewhere wasn't affected negatively.  Since the distances only affect the frequencies in the subwoofer range, it shouldn't affect anything above 150hz or so. 

[derrickdj1]

If it responds, it is not a null.  Finsh up with you setup and I will wait till you are completely finish.

[derrickdj1]

Rob, I didn't comment on the graphs because I thought you had more to post and did not want break you post up.  The graphs look great.  Limited PEQ is important since thing change on both sides of a filter.  You may get a smoother graph but, it may not equate to a better sound.  PEQ is only part of the equation.  Well done my friend!

[RoboKlipsch]

On 10/28/2016 at 1:40 PM, RoboKlipsch said:

i may try using the final distances that I tweaked and seeing how Audyssey deals with them.  My first theory was to give Audyssey what appeared to be one subwoofer (distance and level matched) so it could clearly work out its numbers.  When I tweaked the distances, it was done with trial and error and graphing to insure that the response elsewhere wasn't affected negatively.  Since the distances only affect the frequencies in the subwoofer range, it shouldn't affect anything above 150hz or so. 

 

I did this and found that the overall response was even better.  Trying to tweak them again after Audyssey made no improvements at all.  

So the correct process is to get the correct distances set before Audyssey.  I have updated the outline to reflect this, and also updated my graphs to show the latest results.

 

[CECAA850]

I noticed low output at the 50 to 60Hz range.  Is that a null there or can you bump it?  That's where you get most of your chest slam, 50-70 Hz or so.

[RoboKlipsch]

High Pass Filter Settings, Lower End Response and SPL Sweeps 

 

I'm fortunate to have a nice sized room for the HT.  It's L-shaped but small enough and mostly sealed that I've never had a problem running out of headroom.

Looking at the first set of graphs I had after adding the new subs, I realized the old subs, which are 18" Ultimaxes simply were able to go a bit lower.

Combining the two caused the lowest end response to drop by about 5db.

 

After some careful thought and modelling in WinISD, I decided to use 1st order HPF and lower the amount of power available to the subs.  

It brought the low end response right back up to match what I had before with just the Ultimaxes.    

I have never had the red light limiter come on with 2 subs, and only hit 3 lights once with 2.  Since adding 2 more subs and moving to the corners I haven't even hit 2 lights. 

 

I decided to run some SPL sweeps for the fun of it, and to make sure the lights didn't come blaring on at high SPL.

 

 

The top sweep was at -5 on the AVR.  I think it would likely go a lot higher than that even.

Distortion at the highest level here was under 1%.  At 30hz it touched 3%, then under 12hz it went up to 5%.

 

The INUKES had a consistent single light on during the sweeps

 

[derrickdj1]

I don't think the low spots are significant if he switches to 1/12 smoothing which I recommend.  Raw data will have to many peaks and valleys.  I know a lot of people use the REW raw graphs but, I've not found them to be any benefit over 1/12 smoothing.  Using the raw readings will make you want to use more filters for correction.  Filters alter the FR and phase on both sides of the filter.  You may get a prettier graph in the FR domain but, there will be negative things in the time domain and phase.  This may lessen your tactile response IMHO.

[RoboKlipsch]

12 minutes ago, CECAA850 said:

I noticed low output at the 50 to 60Hz range.  Is that a null there or can you bump it?  That's where you get most of your chest slam, 50-70 Hz or so.

Take a look at the details of the 5 positions, let me know what your thoughts are on what/how much we want.  I do use Audyssey Dynamic EQ, which is of course not shown here.  

 

 

 

 

 

 

 

 

[derrickdj1]

2 minutes ago, RoboKlipsch said:

High Pass Filter Settings, Lower End Response and SPL Sweeps 

 

I'm fortunate to have a nice sized room for the HT.  It's L-shaped but small enough and mostly sealed that I've never had a problem running out of headroom.

Looking at the first set of graphs I had after adding the new subs, I realized the old subs, which are 18" Ultimaxes simply were able to go a bit lower.

Combining the two caused the lowest end response to drop by about 5db.

 

After some careful thought and modelling in WinISD, I decided to use 1st order HPF and lower the amount of power available to the subs.  

It brought the low end response right back up to match what I had before with just the Ultimaxes.    

I have never had the red light limiter come on with 2 subs, and only hit 3 lights once with 2.  Since adding 2 more subs and moving to the corners I haven't even hit 2 lights. 

 

I decided to run some SPL sweeps for the fun of it, and to make sure the lights didn't come blaring on at high SPL.

 

 

The top sweep was at -5 on the AVR.  I think it would likely go a lot higher than that even.

Distortion at the highest level here was under 1%.  At 30hz it touched 3%, then under 12hz it went up to 5%.

 

The INUKES had a consistent single light on during the sweeps

 

Rob, you are fine with this.  You want the 105 db spl at 0 MV.  So, if you are hitting it before, you are a bit hot.  I'm not say you can't go higher for fun.  Once the LFE is added, you will be at 115 db or THX reference with the current settings.  Watching movies much above the 115 db  mark can lead to clipping in the digital domain.  Redirected bass is fine to go on top of the 115 db and may reach 121 db in a 5.x system or up to 127 db in a 9.x or 11.x system.

[CECAA850]

There's definitely a null at 70Hz but I'b be tempted to bump the 50 to 70Hz range by 5dB or so.  Don't get too obsessed over getting a ruler flat response.  Get it close then listen to some music.  Your ears should be your final calibrating tool.  Listen, tweek.  Re-listen, re-tweek till you like what it sounds like..

[RoboKlipsch]

19 hours ago, derrickdj1 said:

Rob, you are fine with this.  You want the 105 db spl at 0 MV.  So, if you are hitting it before, you are a bit hot.  I'm not say you can't go higher for fun.  Once the LFE is added, you will be at 115 db or THX reference with the current settings.  Watching movies much above the 115 db  mark can lead to clipping in the digital domain.  Redirected bass is fine to go on top of the 115 db and may reach 121 db in a 5.x system or up to 127 db in a 9.x or 11.x system.

This may sound odd but every Audyssey curve ive seen has about a 5db drop from about 100 to 200.  I think it may be how they design the curve to have a slightly stronger lower end.  I know their target curve is flat but in practice ive never seen it.  That may explain why at -5 i was hitting 105 or i also could be hot!

[RoboKlipsch]

19 hours ago, CECAA850 said:

There's definitely a null at 70Hz but I'b be tempted to bump the 50 to 70Hz range by 5dB or so.  Don't get too obsessed over getting a ruler flat response.  Get it close then listen to some music.  Your ears should be your final calibrating tool.  Listen, tweek.  Re-listen, re-tweek till you like what it sounds like..

I think theres a peak above that 80hz range that makes it seem low.  REW doesnt really have flat target curves they always have a slope.  This time i tried for flat but can redo it and try for more slam

[CECAA850]

Your chest resonates in the 50 to 70Hz area.  If you feel a kick drum when you're listening to music then you're putting out good SPL in that range.

[derrickdj1]

I like use  The Sheffield drum stuff for drum demo's.  Here is a sample video:

Turn this one up a bit and let it rip.

[CECAA850]

Blue man group audio would work as well.  Ever been to one of their shows?  Talk about impact in that range, wow.

[derrickdj1]

21 minutes ago, CECAA850 said:

Blue man group audio would work as well.  Ever been to one of their shows?  Talk about impact in that range, wow.

I missed them when they were in Chicago.  I have only heard great comments about their show.