Connecting NAD C388 integrated amp to high level inputs on JL Audio E110 Sub

[SuyashMoorpana]

Hello,

Just bought a new subwoofer from JL Audio, E110.
I have to set it up for 2.1 Stereo setup with my Focal Chora 826's being used with a Nad C388 class D amp.

Can you please let me know how to connect it through a high level inputs for best performance?
Does connecting a subwoofer mean that my speaker's drivers will no longer work as usual?
I want my speakers to work like they usually do and use the sub as an addition to the lows and mids.

Apart from that my subwoofer has a crossover switch? Shall I leave it on or off?

Any expert advice on how to set up a sub easily?

Below are the Owners manuals for the amp, sub and the loudspeakers for your reference
JL Audio E110 sub - https://content.abt.com/documents/75852/E112ASH-man.pdf
NAD C388 amp - https://nadelectronics.com/wp-content/uploads/2016/09/C388_eng_OM_v21FE.pdf
Focal Chora 826 loudspeakers - https://www.focal.com/sites/www.foc...document/chora_826_specification_sheet_gb.pdf

For any of you who wrote back to me on my previous thread and helped me shortlist the sub, I would like to honestly thank you. I was overwhelmed by the response and help from you all.

 

[ssf]

Your NAD C338 has sub out ( SLNO 3 rear panel). Connect that to Line Inputs in the JL Audio E110 sub using 2 RCA cables, one each for L and R.

Your main speakers has a frequency range of 48 Hz to 28 Khz (+- 3Db) .

Keep the subwoofer crossover switch in the 'On' position. Set the crossover to 60 Hz. You can experiment with this and keep it to your liking. The higher the crossover, more frequencies will be produced by the speaker and the subwoofer which might lead to muddled bass.

 

[shyamv]

For high-level connections, just connect the Speaker Terminals B directly to High level inputs of your subwoofer in parallel to your main speaker outputs to the Focals . Adjust the crossover as desired.

Not sure if high level or line level connection is recommended for your sub. But if high-level is available, usually this is the better method.

 

[ssf]

Not sure if high level or line level connection is recommended for your sub.

The Manual recommends a line level connection. However, the OP could try both to see which sounds better.

 

[SuyashMoorpana]

Your NAD C338 has sub out ( SLNO 3 rear panel). Connect that to Line Inputs in the JL Audio E110 sub using 2 RCA cables, one each for L and R.

Your main speakers has a frequency range of 48 Hz to 28 Khz (+- 3Db) .

Keep the subwoofer crossover switch in the 'On' position. Set the crossover to 60 Hz. You can experiment with this and keep it to your liking. The higher the crossover, more frequencies will be produced by the speaker and the subwoofer which might lead to muddled bass.

I think the RCA cables are the usual way to connect.
I want to connect my sub via high level inputs.

something like this.

 

[Nitin K]

Hello,

Just bought a new subwoofer from JL Audio, E110.
I have to set it up for 2.1 Stereo setup with my Focal Chora 826's being used with a Nad C388 class D amp.

Can you please let me know how to connect it through a high level inputs for best performance?
Does connecting a subwoofer mean that my speaker's drivers will no longer work as usual?
I want my speakers to work like they usually do and use the sub as an addition to the lows and mids.

Apart from that my subwoofer has a crossover switch? Shall I leave it on or off?

Any expert advice on how to set up a sub easily?

Below are the Owners manuals for the amp, sub and the loudspeakers for your reference
JL Audio E110 sub - https://content.abt.com/documents/75852/E112ASH-man.pdf
NAD C388 amp - https://nadelectronics.com/wp-content/uploads/2016/09/C388_eng_OM_v21FE.pdf
Focal Chora 826 loudspeakers - https://www.focal.com/sites/www.foc...document/chora_826_specification_sheet_gb.pdf

For any of you who wrote back to me on my previous thread and helped me shortlist the sub, I would like to honestly thank you. I was overwhelmed by the response and help from you all.

Congrats Suyash, enjoy your sub...

 

[SuyashMoorpana]

For high-level connections, just connect the Speaker Terminals B directly to High level inputs of your subwoofer in parallel to your main speaker outputs to the Focals . Adjust the crossover as desired.

Not sure if high level or line level connection is recommended for your sub. But if high-level is available, usually this is the better method.

Congrats Suyash, enjoy your sub...

Thank you buddy!!

 

[ssf]

I think the RCA cables are the usual way to connect.
I want to connect my sub via high level inputs.

something like this.

I have used my Velodyne EQ Max 15 sub with both speaker level and line level connections. When using it in my 2 channel system, I was forced to use the speaker level connection. In my HT, I use the line level. To be honest, I could not really tell the difference between the two. Maybe REL is doing something different.

Let us know if you have noticed a difference between the two.

 

[SuyashMoorpana]

Your NAD C338 has sub out ( SLNO 3 rear panel). Connect that to Line Inputs in the JL Audio E110 sub using 2 RCA cables, one each for L and R.

Your main speakers has a frequency range of 48 Hz to 28 Khz (+- 3Db) .

Keep the subwoofer crossover switch in the 'On' position. Set the crossover to 60 Hz. You can experiment with this and keep it to your liking. The higher the crossover, more frequencies will be produced by the speaker and the subwoofer which might lead to muddled bass.

Hey,
You were right JL audio suggests line inputs instead of the high level.
I'm amazed to be honest.
Anyways..If I can adjust the crossover manually, Any idea why there's a active crossover built in the sub?

 

[SuyashMoorpana]

For high-level connections, just connect the Speaker Terminals B directly to High level inputs of your subwoofer in parallel to your main speaker outputs to the Focals . Adjust the crossover as desired.

Not sure if high level or line level connection is recommended for your sub. But if high-level is available, usually this is the better method.

Hey,
I have seen all the reviews recommending the high level inputs.

But for some reason I'm amazed in the owner's manual it says -
The E-Sub features high-level inputs designed to accept the output of an amplified source, such as a stereo receiver’s speaker outputs. The use of this feature is only recommended when no suitable line- level signal is available.
When connecting a single E-Sub in mono to a two-channel receiver’s speaker outputs, you will use both the Left and Right connections on the “High-Level Inputs” plug of the E-Sub.

 

[ssf]

Hey,
You were right JL audio suggests line inputs instead of the high level.
I'm amazed to be honest.
Anyways..If I can adjust the crossover manually, Any idea why there's a active crossover built in the sub?

I hope I have understood your question correctly.

A sub without an active crossover will not have any means to adjust the crossover to seamlessly integrate it with your stereo system. In an HT system, this crossover is managed by the Receiver and the crossover in the sub is overridden. But stereo systems which sends full range signals to the sub require an active crossover to limit the frequency range output by the sub.

 

[SuyashMoorpana]

Got a reply from JL on the topic.
They do not recommend high level input.

Hello,

Thank you for your support of JL Audio and the e110 powered subwoofer.

The e110 does provide both the RCA line inputs and the high level to low level speaker adapter connections for use where a true preamp signal is not available. The high level connection is not our first choice when the RCA connections are available.

Here is the section of the e110 manual that addresses line input connections:

High Level Inputs This feature is included for convenience when needing to connect the E-Sub to a receiver or integrated amplifier that only offers speaker level outputs. It is not the preferred method when a line-level signal is available.

JL Audio believes that when you add a powered subwoofer to a two-way speaker you are now creating a three-way speaker system. When you add a subwoofer to a three-way speaker you are now creating a four-way speaker system.

By using the high-level inputs you are forcing the main speakers to remain full range. Secondly, you are having to run a powered amplifier signal of significant wattage into a set of resistors to reduce the signal level to millivoltage which is acceptable for the input stage of the amplifier on the powered subwoofer.

By keeping the speakers full range you are continuing the midrange distortion on the woofer cone that is simultaneously playing sub bass frequencies while playing up to the internal crossover frequency of the speaker. This is usually:

350 Hz Test Tone on most 3-way speaker models

On your Focal Chora 826 the internal crossover frequency between the woofer and the midrange driver is:

270Hz Test Tone

AND
2200 Hz Test Tone on most 2-way speaker models

Even on the 3-way playing up to the 270Hz point you can hear from the test tone that this is well within the female vocal range. When speakers are playing full range female vocalists are singing from the woofer while it is shaking back and forth as low as you will allow it to go.

So we believe it is not how low your speakers can play down to it is much more important to know high your woofer is playing up to before being crossed over to the next smallest driver (midrange or tweeter).

Additionally, by letting the main speakers play full range you are prevented from allowing the subwoofer to play up to the frequencies that it is designed to play. The reason a HT system processor defaults to 80Hz for the THX crossover point is that typically subwoofers are purpose-designed to play the lowest two octaves (80 to 20 hertz).

If you must play the speakers full range, we advise a 60 Hz for the low pass frequency setting on the subwoofer. Much higher than this and you are "co-playing" a lot of common frequencies between the speaker's woofer and the subwoofer which can lead to smearing and muddiness; especially if the phase alignment is not correct between the subwoofer and the main speaker. Much lower than this and you are restricting the subwoofer from "earning it's keep".

Thank you for providing your complete equipment list. After reading the owners manual of the NAD C388 I see that it is equipped with a set of RCA outputs that are configurable between full range OR crossed over at 150Hz at 12dB per octave for sending to a powered subwoofer. When configured to the Subwoofer mode it also high passes the the speaker connections going to your Focals at the same frequency and slope (150Hz at 12dB per octave).

This would be our first choice in setup of your system with the e110.

As for placement of a single subwoofer we would recommend the inside edge of one of the two speakers in close proximity and on plane with the front of the speaker cabinet. By placing it there you are able to tune it to the speaker and create what we call a "single entity" between the speaker and the subwoofer. Additionally by being on the inside you are not too far away from the speaker that does not have a subwoofer in its proximity and the subwoofer is "shared" more effectively.

The most important tuning to get correct is the impulse response which the correct positioning of the phase control knob on the e110. When your subwoofer cone and your woofer cone on the Focal are in phase the synchronous motion creates a significant improvement in focus and detail when the two cones stop fighting each other.

That said, there would still be another sound producer in the room that you cannot synchronize to match the motion of the Focal or the e110. This is the out of phase waveform coming out of the port on the Focal 826. If Focal provided port plugs to seal the ports you should use them when adding a powered subwoofer to your system. If not supplied with the Focals, soft foam rubber the type seat cushions are made from can be squeezed and allowed to expand inside the port opening to prevent the smearing that occurs when the port is allowed to contribute to the audio output.

Many of our customers with front firing ports will place the foam into a black sock and tie an knot in it. Then when the squeeze and insert the sock-covered foam it is black and non obtrusive looking.

So here is the recap:

• Seal the ports on the Focals
• Set the NAD RCA outputs to Subwoofer output mode
• Turn the crossover on the e110 to OFF (crossover frequency dial is then bypassed and irrelevant)
• Place the e110 on the inside edge of one of the Focals
• Perform the reverse polarity phase alignment procedure that I am providing as a hyperlink below
• Adjust the gain on the e110 until it is just below the threshold of audibility (not louder than the speaker)

Adjusting Phase Alignment

Enjoy!
Randy


Randy Wagner
Technical Support Specialist

Randy Wagner
Technical Support Specialist

 

[ssf]

Got a reply from JL on the topic.
They do not recommend high level input.

Hello,

Thank you for your support of JL Audio and the e110 powered subwoofer.

The e110 does provide both the RCA line inputs and the high level to low level speaker adapter connections for use where a true preamp signal is not available. The high level connection is not our first choice when the RCA connections are available.

Here is the section of the e110 manual that addresses line input connections:

High Level Inputs This feature is included for convenience when needing to connect the E-Sub to a receiver or integrated amplifier that only offers speaker level outputs. It is not the preferred method when a line-level signal is available.

JL Audio believes that when you add a powered subwoofer to a two-way speaker you are now creating a three-way speaker system. When you add a subwoofer to a three-way speaker you are now creating a four-way speaker system.

By using the high-level inputs you are forcing the main speakers to remain full range. Secondly, you are having to run a powered amplifier signal of significant wattage into a set of resistors to reduce the signal level to millivoltage which is acceptable for the input stage of the amplifier on the powered subwoofer.

By keeping the speakers full range you are continuing the midrange distortion on the woofer cone that is simultaneously playing sub bass frequencies while playing up to the internal crossover frequency of the speaker. This is usually:

350 Hz Test Tone on most 3-way speaker models

On your Focal Chora 826 the internal crossover frequency between the woofer and the midrange driver is:

270Hz Test Tone

AND
2200 Hz Test Tone on most 2-way speaker models

Even on the 3-way playing up to the 270Hz point you can hear from the test tone that this is well within the female vocal range. When speakers are playing full range female vocalists are singing from the woofer while it is shaking back and forth as low as you will allow it to go.

So we believe it is not how low your speakers can play down to it is much more important to know high your woofer is playing up to before being crossed over to the next smallest driver (midrange or tweeter).

Additionally, by letting the main speakers play full range you are prevented from allowing the subwoofer to play up to the frequencies that it is designed to play. The reason a HT system processor defaults to 80Hz for the THX crossover point is that typically subwoofers are purpose-designed to play the lowest two octaves (80 to 20 hertz).

If you must play the speakers full range, we advise a 60 Hz for the low pass frequency setting on the subwoofer. Much higher than this and you are "co-playing" a lot of common frequencies between the speaker's woofer and the subwoofer which can lead to smearing and muddiness; especially if the phase alignment is not correct between the subwoofer and the main speaker. Much lower than this and you are restricting the subwoofer from "earning it's keep".

Thank you for providing your complete equipment list. After reading the owners manual of the NAD C388 I see that it is equipped with a set of RCA outputs that are configurable between full range OR crossed over at 150Hz at 12dB per octave for sending to a powered subwoofer. When configured to the Subwoofer mode it also high passes the the speaker connections going to your Focals at the same frequency and slope (150Hz at 12dB per octave).

This would be our first choice in setup of your system with the e110.

As for placement of a single subwoofer we would recommend the inside edge of one of the two speakers in close proximity and on plane with the front of the speaker cabinet. By placing it there you are able to tune it to the speaker and create what we call a "single entity" between the speaker and the subwoofer. Additionally by being on the inside you are not too far away from the speaker that does not have a subwoofer in its proximity and the subwoofer is "shared" more effectively.

The most important tuning to get correct is the impulse response which the correct positioning of the phase control knob on the e110. When your subwoofer cone and your woofer cone on the Focal are in phase the synchronous motion creates a significant improvement in focus and detail when the two cones stop fighting each other.

That said, there would still be another sound producer in the room that you cannot synchronize to match the motion of the Focal or the e110. This is the out of phase waveform coming out of the port on the Focal 826. If Focal provided port plugs to seal the ports you should use them when adding a powered subwoofer to your system. If not supplied with the Focals, soft foam rubber the type seat cushions are made from can be squeezed and allowed to expand inside the port opening to prevent the smearing that occurs when the port is allowed to contribute to the audio output.

Many of our customers with front firing ports will place the foam into a black sock and tie an knot in it. Then when the squeeze and insert the sock-covered foam it is black and non obtrusive looking.

So here is the recap:

• Seal the ports on the Focals
• Set the NAD RCA outputs to Subwoofer output mode
• Turn the crossover on the e110 to OFF (crossover frequency dial is then bypassed and irrelevant)
• Place the e110 on the inside edge of one of the Focals
• Perform the reverse polarity phase alignment procedure that I am providing as a hyperlink below
• Adjust the gain on the e110 until it is just below the threshold of audibility (not louder than the speaker)

Adjusting Phase Alignment

Enjoy!
Randy


Randy Wagner
Technical Support Specialist

Randy Wagner
Technical Support Specialist

That was very responsive of JL Audio.

I missed the part where the Nad had a sub crossover feature where frequencies below 150 Hz are sent to the sub and above it is sent to the speakers.

So options you could try:

Use the NAD sub crossover feature. But for this to work correctly, you will have to place the sub as suggested by JL Audio. If you are not able to place the sub in this position, then at 150 Hz, the sub will be localised resulting in your high, mid and lower mid frequencies coming from one place and the bass frequencies coming from another.

If you are not able to place the sub in the location specified by JL Audio, I would disable the subwoofer mode and send full range to the speakers and crossover the sub at 60.

Congratulation on your purchase and all the best for configuring your system.

 

[shyamv]

While this is very responsive of JL Audio, this is quite contrary to what REL says about their subwoofer setup and configuration. The very issue that JL Audio points out about high-level connections is claimed by REL as a virtue of their subs. Recommending to plug the Focal speaker ports is also quite interesting. While I am not an expert of subwoofers by any means, I am not sure if hamstringing the main speakers would make the overall sound better.

 

[SuyashMoorpana]

That was very responsive of JL Audio.

I missed the part where the Nad had a sub crossover feature where frequencies below 150 Hz are sent to the sub and above it is sent to the speakers.

Don't you think that's a stupid feature from NAD? or all the amps are similar?

So options you could try:

Use the NAD sub crossover feature. But for this to work correctly, you will have to place the sub as suggested by JL Audio. If you are not able to place the sub in this position, then at 150 Hz, the sub will be localised resulting in your high, mid and lower mid frequencies coming from one place and the bass frequencies coming from another.

I just checked the max crossover available on my sub is 130 apparently.
So if I use the NAD's sub crossover feature..my speakers stop going below 150Hz and the sub picks up from 130Hz.
Don't you think that would be a problem? Or the sub can play frequencies above 130Hz as-well?

If you are not able to place the sub in the location specified by JL Audio, I would disable the subwoofer mode and send full range to the speakers and crossover the sub at 60.

Do you think that's a good idea?
Actually I wanted something like Rel..As far as the reviews go it adds to the mids and lows both.
If I am using my sub only below 60Hz.
I feel I am not getting the most out of it.

Congratulation on your purchase and all the best for configuring your system.

Thank you buddy!!

 

[SuyashMoorpana]

After reading the owners manual of the NAD C388 I see that it is equipped with a set of RCA outputs that are configurable between full range OR crossed over at 150Hz at 12dB per octave for sending to a powered subwoofer. When configured to the Subwoofer mode it also high passes the the speaker connections going to your Focals at the same frequency and slope (150Hz at 12dB per octave).

Can any of you guys read this and guide me.
It is a bit confusing to me..Does this function on my NAD C388 send all the frequency's below 150hz to the sub and above 150 to the Loudspeakers?

If yes? will the speakers and the sub blend seamlessly? I ask this because there wont be a overlap at all..as far as i know we're supposed to keep around 20-40hz in common at the point of crossover?

 

[ssf]

Don't you think that's a stupid feature from NAD? or all the amps are similar?

This feature is implemented in HT Receivers. It is very rarely implemented in stereo amps which is why I missed it. The feature would have been more useful if they had provided a way for the end user to set the crossover point like in Receivers.

I just checked the max crossover available on my sub is 130 apparently.
So if I use the NAD's sub crossover feature..my speakers stop going below 150Hz and the sub picks up from 130Hz.
Don't you think that would be a problem? Or the sub can play frequencies above 130Hz as-well?

Yes, this will be a problem unless there is a crossover defeat function in the sub. It takes a good eye to catch this. Well done. You could ask JL Audio to clarify this.

Do you think that's a good idea?
Actually I wanted something like Rel..As far as the reviews go it adds to the mids and lows both.
If I am using my sub only below 60Hz.
I feel I am not getting the most out of it.

If there is no crossover defeat function, I think that you only have two options now. One is to use the High Level connection and the other is to use the line level connection. Either way, the configuration of the sub will remain the same for both the two methods.

I would not want my sub to add to the mids. I don't think the REL's do it. I don't think any good subwoofer does it. What it might do is that due to a very good integration between the sub and the mains, the mids that the mains produce might sound better. The reasoning behind speaker level connections being better is that it is using the exact same signal that is being sent to the main speakers.

You can experiment with the crossover in the range of 80 to 60 Hz and use whatever sounds good to you.

Does this function on my NAD C388 send all the frequency's below 150hz to the sub and above 150 to the Loudspeakers?

If yes? will the speakers and the sub blend seamlessly? I ask this because there wont be a overlap at all..as far as i know we're supposed to keep around 20-40hz in common at the point of crossover?

Yes, it sends all frequencies below 150Hz to the sub and above 150 Hz to the speakers. This cannot be tried in your scenario as your subs frequency range is only upto 130 Hz.

All Receivers function like this. If you set the crossover at 80 Hz, it sends frequencies above 80 to the speakers and below 80 Hz to the subwoofer.

Blending a sub with the speakers goes beyond just setting the crossovers. You could read about it on the web as it is not specific to any subwoofer. The sub levels, sub phase, sub placement etc also contributes to the integration of the sub with the main speakers.

Also, as there is no way to set the delay when using a sub in a stereo amp, the sub should be placed as close to the main speakers as possible. Else, the sound from the main speakers and sound from the sub will reach the listening position at slightly different times.

 

[SuyashMoorpana]

This feature is implemented in HT Receivers. It is very rarely implemented in stereo amps which is why I missed it. The feature would have been more useful if they had provided a way for the end user to set the crossover point like in Receivers.



Yes, this will be a problem unless there is a crossover defeat function in the sub. It takes a good eye to catch this. Well done. You could ask JL Audio to clarify this.

If there is no crossover defeat function, I think that you only have two options now. One is to use the High Level connection and the other is to use the line level connection. Either way, the configuration of the sub will remain the same for both the two methods.

I would not want my sub to add to the mids. I don't think the REL's do it. I don't think any good subwoofer does it. What it might do is that due to a very good integration between the sub and the mains, the mids that the mains produce might sound better. The reasoning behind speaker level connections being better is that it is using the exact same signal that is being sent to the main speakers.

You can experiment with the crossover in the range of 80 to 60 Hz and use whatever sounds good to you.


Yes, it sends all frequencies below 150Hz to the sub and above 150 Hz to the speakers. This cannot be tried in your scenario as your subs frequency range is only upto 130 Hz.

All Receivers function like this. If you set the crossover at 80 Hz, it sends frequencies above 80 to the speakers and below 80 Hz to the subwoofer.

Blending a sub with the speakers goes beyond just setting the crossovers. You could read about it on the web as it is not specific to any subwoofer. The sub levels, sub phase, sub placement etc also contributes to the integration of the sub with the main speakers.

Also, as there is no way to set the delay when using a sub in a stereo amp, the sub should be placed as close to the main speakers as possible. Else, the sound from the main speakers and sound from the sub will reach the listening position at slightly different times.

Revert from JL Audio.. below
I think it'll be fine. not a lot to be worried about.
What do you think?

Hello,

It is the overlap that creates the opportunity for smearing the transition between the speaker's woofer and the subwoofer driver. The more the overlap the more smearing that can occur. This is why when two channel systems are set up to play the speaker full range the subwoofer low pass should not be above 60 hertz.

Setting it higher causes the smearing and muddiness and setting much lower prevents the subwoofer from doing it's job.

In a home theater system you are usually setting the two-way crossover at 80Hz and most often with a slope of 24dB per octave. The fourth order 24dB per octave slope is rolling off in both direction (high and low pass) at twice the slope of your crossover setup in the NAD (12dB per octave).

Here is a graph of a two-way crossover set to 100Hz displaying both a 12 dB and 24 dB per octave setting. An octave is either doubling of the frequency or halving the frequency. Look a the graph and you will see at 50Hz and 200Hz the 12 and 24 dB positions on the graph.



With your NAD set at 150Hz and 12dB per octave you can see that you will be crossed over higher than this but a the more gently roll off of the grey line graph.

After you get the NAD set correctly and the e110 control panel set to:

• Polarity at 0
• Phase control at 0
• Crossover switch to OFF

You will then need to do the phase adjustment procedure that I linked in the prior email. You will need to be able to play a 150Hz sine wave test tone through the NAD to accomplish the procedure. Here is an example the tone.

150Hz Sine Wave Test Tone

Once you are in phase with the subwoofer tucked closely to the inside edge of one of the speakers you will be amazed at the overall clarity and focus of your system. Add the second e110 and it should be a stunner!

So here is the recap:

• Seal the ports on the Focals
• Set the NAD RCA outputs to Subwoofer output mode
• Turn the crossover on the e110 to OFF (crossover frequency dial is then bypassed and irrelevant)
• Place the e110 on the inside edge of one of the Focals
• Perform the reverse polarity phase alignment procedure that I am providing as a hyperlink below
• Adjust the gain on the e110 until it is just below the threshold of audibility (not louder than the speaker)

Respectfully,
Randy Wagner
Technical Support Specialist

 

[ssf]

Revert from JL Audio.. below
I think it'll be fine. not a lot to be worried about.
What do you think?

While I would have preferred to have a crossover defeat function, the slope does not look steep enough to create problems. You could try it out and see for yourself if it makes a difference.

Edit: He says, set the crossover switch to off. This is exactly what a crossover defeat is. You should be fine with this setting.

In your place, I would still use the front speakers at full range and crossover the sub at 60.

 

[Decadent_Spectre]

While this is very responsive of JL Audio, this is quite contrary to what REL says about their subwoofer setup and configuration. The very issue that JL Audio points out about high-level connections is claimed by REL as a virtue of their subs. Recommending to plug the Focal speaker ports is also quite interesting. While I am not an expert of subwoofers by any means, I am not sure if hamstringing the main speakers would make the overall sound better.

By plugging the ports (assuming you did it correctly) the system transforms into a sealed system. This means that now the low end extension point of the speaker has shifted up significantly in frequency as the port is no longer providing its native extension, this also means the systems previous output near tune is gone as it has become a sealed system, however this also means that the speaker has a much better time domain response to provide better integration and "speed". The subwoofer will now be the major contributor of sound to a higher frequency, this may or may not sound better than the speaker but the subwoofer may become directional if it plays too high. Do keep in mind that as a sealed system the drivers of the speaker covering the lower end of the spectrum will see greater excursion and heating if the speaker attempts to play too loud and too low.