Help with integrating a sealed subwoofer and a ported subwoofer

PatMax

Novice Member
I am trying to integrate a BK XXLS400 DF and a BK Monolith DF in a 5.2.2 system.
The BK XXLS400 was purchased with the intention of using it only for music as 2.1, however I was impressed how much better the bass sounds when I use it together with the Monolith for movies in 5.2.2 format. The BK XXLS is connected to an Arcam SA30 via the high level connection and to a Yamaha RX-V 685 via the low level connection. The Monolith is only connected to the Yamaha RX-V 685 via low level connection. Both subs in LFE mode when whatching movies. I set the subs to have the same gain with an SPL meter - slow C weighted.
I have done the YPAO calibration for the distances and levels. During calibration the subs phases were set to 0 on both. All the speakers are nkw set to small with 80hz crossover in the AVR. The YPAO EQ is set to flat. I then further tweaked the speakers and subs gain level using the SPL meter. The Yamaha has two subwoofer preouts, however it manages them together as one. The YPAO did a good job averaging the distance from the subs to the listening spot.
I testest for hours variants with the AVR in stereo mode (2.2) for the different phases on the subs because I was getting different results at different frequencies until I found the sweet spot (I think).
So here is where I am now:
The best combination is when I keep the BK XXLS400 phased at 180 degrees (10th position) and the Monolith at either the 36 degrees phase (second position on the knob) or at 54 degrees (third position on the knob)
Comparing the two situations at different Hz with the SPL meter there are benefits and downsides (C slow weighted average):
With the Monolith at 36 degrees (second position): at 30 Hz I gain +2 Db, at 40Hz I gain +3.2 Db, at 50Hz it stays the same in both situations, at 60 Hz I lose -0.5 Db, at 70Hz it is -1.5 Db (lower), -3Db (lower) at 80Hz and -1.8Db (lower) at 90Hz.
The opposite is true of course when I set the monolith at 54 degreee (third position on the knob).
For now I left the Monolith at the second position.
The Monolith is positioned in a corner on the right side of the couch right next to the main listening position. The BK XXLS400 is positioned almost diagonally oposite to the Monolith (to be more specific it is placed under the centre speaker and next to the main left speaker).

Is there anything more I can do to better integrate them? I do not have a miniDSP at the momoment.

Two months I did not have a clue about any of this and I was able to find so much information on old posts on this forum so a big thank you to all the people that have offered their information here overe the years.

Kind Regards,
Pat
 

PatMax

Novice Member
I was not able to edit or delete the above thread. The factors have changed a bit after some more work and tests:
I made the message shorter and more to the point:

I am trying to integrate a BK XXLS400 DF and a BK Monolith DF in a 5.2.2 system.

The best sweet spot I found is when I keep the BK XXLS400 phased at 180 degrees (10th position) and the Monolith at the 54 degrees phase (third position on the knob). (Tested with an spl meter with sine tones for 30, 40, 50, 60, 70,80 ,90 hz).

The big problems is at 60hz where I lose -7.5 Db because these frequency is best with the Monolith at 18 degrees (first position).

It's probably because of the tuning point on the ported Monolith compared to the sealed xxls400. Is there any way to mediate this? Should I maybe increase the volume of the Monolith a bit? (As both subs are set to have the same db output).

The Monolith is positioned in a corner on the right side of the couch right next to the main listening position. The BK XXLS400 is positioned almost diagonally oposite to the Monolith (to be more specific it is placed under the centre speaker and next to the main left speaker.

Kind Regards,
Pat
 

PatMax

Novice Member
For anyone who ever encounters this problem. It was actually the YPAO Flat eq that was messing up my subs. Once I set it to "through" everything became easier and was able to find a much much better sweet spot with the BK400 set at phase 0 degress and the Monolith's phase at 36 degrees (second position on the knob). The bass output is much better and you can clearly hear it even without the spl meter.
 

Conrad.

Moderator
It sounds like you've done a good job, even with limited tools.
Depending on the SPL meter you might be able to hook it up to REW which will make your life much easier.

The usual approach is to get the two subs combined so that they have the fewest nulls, then let EQ take care of the peaks. If you're giving YPAO the two subs individually (on two independent sub outs) then it could well undo your phase work by adjusting the distances.

In that case let YPAO run first and then adjust the phase to improve on it.

If this is something that you're interested in doing in the long term I would recommend the investment in a £110 UMIK-1, it'll make things significantly quicker and easier for you.
 

PatMax

Novice Member
It sounds like you've done a good job, even with limited tools.
Depending on the SPL meter you might be able to hook it up to REW which will make your life much easier.

The usual approach is to get the two subs combined so that they have the fewest nulls, then let EQ take care of the peaks. If you're giving YPAO the two subs individually (on two independent sub outs) then it could well undo your phase work by adjusting the distances.

In that case let YPAO run first and then adjust the phase to improve on it.

If this is something that you're interested in doing in the long term I would recommend the investment in a £110 UMIK-1, it'll make things significantly quicker and easier for you.
Thank you kindly for your reply Conrad.
Unfortunatelly the SPL meter that I used, is an app I bought on my phone. I tested several apps and it was the only one that offered pretty reliable C weighted measurements (reliable in a sense that the measurements stay the same). I intended to buy an no name SPL meter (50£), however most bad reviews pointed out not to be reliable and to go with a REED meter. So the spl app purchase was a compromise until I get something better.
Yes, the subs are connected to the two preouts of the Yamaha RX-V685. I did ran the YPAO calibration with the subs both set on phase zero and did those tests yesterday with the sine tones after the calibration has been done. However, it seems that the FLAT EQ was hindering my subs integration. That being said, I do think that the FLAT EQ option was indeed quite important for my other speakers to integrate better with the room geometry.
I will hopefully soon buy the minidsp 2x4 HD. Instead of UMIK, I was hoping I could use the mic that came with the ARCAM SA30 (meant for stereo DIRAC calibration) as I have the calibration file for the mic. Would it work with REW? Hmm maybe I should have tried it already, however from some youtube video I was under the impresion that I need the miniDSP to be able to make use of REW.

Thank you again Conrad!

Kind Regards,
Pat
 

Conrad.

Moderator
I would get the mic first as you seem to be capable without the need of a minidsp (yet).
The mic will let you measure without and without YPAO so you can see exactly what flat is doing and make adjustments, and see the outcome. You'll only need a minidsp if you can't get the results you want without it.

You need a way of implementing the filters from REW into the signal chain. Usually that's a minidsp as it's the cheapest and most widely supported EQ device with that feature set, but it's not the only option. The Behringer Feedback Destroyer, Velodyne SMS1, SVS EQ device, Jriver, they all do the same thing, and some subs have EQ built in, which helps.

In your case you're just adjusting phase which is a control both of your subs have, it might be enough. The minidsp will make things much easier, but it's not an absolute necessity.
 

PatMax

Novice Member
I would get the mic first as you seem to be capable without the need of a minidsp (yet).
The mic will let you measure without and without YPAO so you can see exactly what flat is doing and make adjustments, and see the outcome. You'll only need a minidsp if you can't get the results you want without it.

You need a way of implementing the filters from REW into the signal chain. Usually that's a minidsp as it's the cheapest and most widely supported EQ device with that feature set, but it's not the only option. The Behringer Feedback Destroyer, Velodyne SMS1, SVS EQ device, Jriver, they all do the same thing, and some subs have EQ built in, which helps.

In your case you're just adjusting phase which is a control both of your subs have, it might be enough. The minidsp will make things much easier, but it's not an absolute necessity.
Thank you again Conrad for your helpful replies. I will give REW a try on my next days off with the Arcam V2 mic (that I alreadu have) to see what measurements I get, as I read today some threads here of people using it with REW. If not, I will buy the UMIK.
With regards to the Mini DSP HD. Do you think the NON HD cheaper version that is limited to max 7ms delay would be of any use in my case?


Kind Regards,
Pat
 

Conrad.

Moderator
I think the non-HD version might be a false economy. The precision is better in the HD and I think it has fewer filters. That may or may not be an issue for you. For reference, my greatest sub delay is about 15ms. I might be able to reduce that by decreasing the distance in the AVR, but I haven't tried. So the non-HD definitely wouldn't work for me.
 

james morrison

Active Member
Got a behringer feedback destroyer and cables that I never got around to using sitting about that you can have to see if it helps. Only cost you price of postage and it will make wife happy that another bit of gear that I bought and never used has gone.
 

PatMax

Novice Member
I think the non-HD version might be a false economy. The precision is better in the HD and I think it has fewer filters. That may or may not be an issue for you. For reference, my greatest sub delay is about 15ms. I might be able to reduce that by decreasing the distance in the AVR, but I haven't tried. So the non-HD definitely wouldn't work for me.
Thank you Conrad for you reply. Apologies, it's been a busy week. I managed to spend some hours last night to install REW and understand it a bit. The Arcam mic did give repeatable results and after many tweaks on the subs, this is the best I can get by tunning the phases. The images provided is with the Left Front Speaker used as reference. The AVR is at -22dB and the REW measurements were taken at -26dB sweeps due tk the late hour.
The image with a single purple line is the best outcome ( before the YPAO calibration). The second image is the final result after the YPAO calibration and how different YPAO subwoofer levels change it a bit more at -0.5; -2.5 and -6.5). In the meantime I also got to see what YPAO is changing and in this case it tries to help the sub by attenuating the 39Hz peak (third image attached)
The peak at around 37-39Hz is my main problem I think. Any changes to the phases barely influence this frequency. I can take that 39hz peak further down about 3-5dB by tweaking the phases, however it greatly impacts the other values, so this was the best I could get. The only thing that would further help is moving the couch forward about a meter and even then the 39hz goes down only by 5dB. Am I correct to assume that this is due to an axial room mode? My room is not treated. This frequency resonates at the back and the front of the room and it disipates at the sides and in the middle of the room.
Considering the above, do you think that by adding delays to the subs with a dsp would further help attenuate that peak?

Kind Regards,
Patrick
 

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PatMax

Novice Member
Got a behringer feedback destroyer and cables that I never got around to using sitting about that you can have to see if it helps. Only cost you price of postage and it will make wife happy that another bit of gear that I bought and never used has gone.
Thank you so much James. My apologies for reading your reply a week after. It has been a busy time at work. That is really kind of you to offer. However, I am not sure if I could use it with my setup. From what I previously read about Behringers, they have balanced inputs and my YAMAHA AVR does not have any balanced preouts.
I greatly appreciate it.
Kind Regards,
Patrick
 

Conrad.

Moderator
Thank you Conrad for you reply. Apologies, it's been a busy week. I managed to spend some hours last night to install REW and understand it a bit. The Arcam mic did give repeatable results and after many tweaks on the subs, this is the best I can get by tunning the phases. The images provided is with the Left Front Speaker used as reference. The AVR is at -22dB and the REW measurements were taken at -26dB sweeps due tk the late hour.
The image with a single purple line is the best outcome ( before the YPAO calibration). The second image is the final result after the YPAO calibration and how different YPAO subwoofer levels change it a bit more at -0.5; -2.5 and -6.5). In the meantime I also got to see what YPAO is changing and in this case it tries to help the sub by attenuating the 39Hz peak (third image attached)
The peak at around 37-39Hz is my main problem I think. Any changes to the phases barely influence this frequency. I can take that 39hz peak further down about 3-5dB by tweaking the phases, however it greatly impacts the other values, so this was the best I could get. The only thing that would further help is moving the couch forward about a meter and even then the 39hz goes down only by 5dB. Am I correct to assume that this is due to an axial room mode? My room is not treated. This frequency resonates at the back and the front of the room and it disipates at the sides and in the middle of the room.
Considering the above, do you think that by adding delays to the subs with a dsp would further help attenuate that peak?

Kind Regards,
Patrick

Are you changing the phase of the subs independently, or together?
It's worth using the time alignment tool to evaluate what delays will do to the combined response. As long as you have a timing reference you can use it.

The problem is implementing that ms delay as a phase change. I was just discussing this over PM and I wasn't able to answer. Phase angle changes with frequency and so I don't know how to say that a 3ms delay converts to an x degree phase change, because the questions is "where?". Where are you measuring that phase change.

@Ultrasonic, can you help here?
Is there a way to convert a ms delay in REW to a phase angle change on a sub phase control?

Other than that, I'm sure the mic is consistent, unfortunately you don't know that it's accurate. A mode like in the 30s suggests a large room, is that right? In which case that low end roll off might be right, but it might be the mic losing sensitivity below 30Hz. There could be a calibration file loaded into the Yamaha to correct for that.

I wouldn't worry too much about fixing the big mode, that's easy for EQ to take care of, although the alignment tool will tell you if you can do better. I would focus next on the 100Hz dip which can likely be lessened by adjusting the phase relationship/distance between subs and mains.
 

Ultrasonic

Well-known Member
The problem is implementing that ms delay as a phase change. I was just discussing this over PM and I wasn't able to answer. Phase angle changes with frequency and so I don't know how to say that a 3ms delay converts to an x degree phase change, because the questions is "where?". Where are you measuring that phase change.

@Ultrasonic, can you help here?
Is there a way to convert a ms delay in REW to a phase angle change on a sub phase control?

You're right about the phase change of a delay being frequency dependent. It makes sense to consider the phase change at the crossover frequency between sub and main speakers. I actually use this the other way round for setup myself: I measure the phase difference at the crossover frequency and use it to calculate the time delay to apply in a miniDSP to get the phases to match (in combination with arrival time info. from looking at the impulse response.)

I'll give the maths below but I would personally have zero confidence in applying this to the position of the phase control on a BK sub. Certainly the behaviour of the phase adjustment on my Monolith gave nothing like the sort of direct relationship that might be expected and I think time delays applied via DSP (either on the sub itself like my PSA or separately by an AVR or miniDSP) is a much better way to do this.

___________________________________________________________________________________________

Some maths for anyone that cares....

A sound wave of frequency f has a time period T = 1/f, meaning that it repeats ever time interval T. For example at 80 Hz, T = 12.5 ms.

Phase changes relate to time delays based on what proportion of a cycle they represent. A full cycle is 360°, so a phase shift of θ° corresponds to a time delay of θ°/360° multiplied by the period T. So for the 80 Hz example, a phase change of 180° would be half the period of 12.5 ms, so 6.25 ms.

Given the signals repeat, the phase difference between the main speakers and sub is unchanged by adding time delays that are an integer multiple of the period. So for the 80 Hz example, adding a 12.5 ms delay makes no difference to the relative phase, but may be helpful to get first arrival times to match.
 

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