Line Level vs. Speaker Level connection to sub(s)

ML subs offer both line level (from preamp) and speaker level (from amp) connections. I've always used the former with my BF 210's. However, on a whim, I just tried the Speaker Level connection direct from my C-J amp to the subs, as that's the approach recommended for REL subs (likewise highly regarded). On first blush, the bass sounds a little tighter, ostensibly due to better phase/time alignment with my ML Expressions (running full range).

The old (Blue Jeans) speaker cables I used for this experiment were too short for permanent placement or XTZ Room Analyzer measurements, so I ordered a pair of longer cables, and will do more extended listening comparisons and measurements over the next few weeks.

In the meantime, I'm curious about your thoughts re Line vs. Speaker Level connections to sub(s).

A long time ago, I used speaker level with great results.

These days, I use line level - primarily because I use bass management; so no choice - no argument to have.

This is the way my old Vandersteen W2 subs were connected. To me it made since to me that with speaker level your subs would get the exact same signal as your mains.

That said I currently run my Depth i's on a line lever as it is easier.

My Rel and Sumiko subs support both types of connection concurrently. Long time ago when it was just one Rel I was able to use both with no issues and preferred the Neutrik input connection for 2 channel listening.

Fast forward to last year, I was using LFE Input only on the subs, no High Level Neutrik, due to getting ground loop hum while using both concurrently. I never got around to rewiring the offending circuit for my projector, and I no longer need subs for my main L&R speakers, so I still only use the LFE Input (not the Line input) on the subs for all other speaker channels. However, I always preferred the more cohesive sound when using the Speaker Level Neutrik connection.

Alan, the first question will be around are you using bass management or not. It sounds like in your CJ preamp config, there is no bass-management, right?
BTW- Bass-management = the preamp has an active crossover between the mains and the sub, which can also do umming (L+R) if there is only a single sub. That way, the sub handles all signals below the crossover point and the mains handle everything above it.

If you do NOT have bass-management in the preamp, and you parallel the output to the power amp for the mains, with an input the subs (using the high-pass input NOT the LFE), then you are performing what is referred to as a double-bass setup, and the low-end is quite boosted. In general, this is not a recommended configuration, as you can get modal interference and phase cancelations between the output of the mains and the subs.

Now, using the speaker-level inputs on the sub guarantees that it will be applying a high-pass filter before amplifying the signal. So if you have been using the full-range LFE input up until now, that would explain the change, as now there is actually a crossover in the path.

Jonathan, you're right... no bass management with my C-J pre. However, the ML BalancedForce Subs have custom downloadable crossover filters. I'm running my ML Expressions full range, with dual (stereo) BF 210 subs mainly to 1) partially overcome a bass null at ~50-60 Hz, and 2) to further pressurize the large (open floor plan) room.

The "double bass" issue will only arise if I simultaneously feed them LFE from my old Denon home theater receiver, while also feeding bass via speaker (or line) level signal via the C-J Pre Home Theater Bypass. In that situation, I should be able to compensate (via Audyssey MultEQ or manually) in my receiver. Thus far, however, I haven't even hooked up LFE, as I primarily use the system for two channel listening. That will likely change now, as I just upgraded to a 77" LG OLED!

Of note, the C-J Pre is phase inverting, so line level output to the subs is off 180 degrees vs. the Expressions. Although I can (and have) manually adjusted the BF 210's phase, I'm thinking the line-level approach might synergize better.

Over the next couple weeks, I'll play around with XTZ Room Analyzer measurements, and listening tests, and see what works best!

JonFo said:

Alan, the first question will be around are you using bass management or not. It sounds like in your CJ preamp config, there is no bass-management, right?
BTW- Bass-management = the preamp has an active crossover between the mains and the sub, which can also do umming (L+R) if there is only a single sub. That way, the sub handles all signals below the crossover point and the mains handle everything above it.

If you do NOT have bass-management in the preamp, and you parallel the output to the power amp for the mains, with an input the subs (using the high-pass input NOT the LFE), then you are performing what is referred to as a double-bass setup, and the low-end is quite boosted. In general, this is not a recommended configuration, as you can get modal interference and phase cancelations between the output of the mains and the subs.

Now, using the speaker-level inputs on the sub guarantees that it will be applying a high-pass filter before amplifying the signal. So if you have been using the full-range LFE input up until now, that would explain the change, as now there is actually a crossover in the path.

Click to expand...

Jon. Question for you. I have a sunfire sig cinema grand. Have you ever tried daisy chaining the rear and front channels in the rear of the amp - then going out from the amp rear channels into a descent? I think a descent only has line level. Do you think this setup would be better than out of the pre or might something blow up. . Just wonder if you had ever tried it in your travels with sunfire and ML.

> In the meantime, I'm curious about your thoughts re Line vs. Speaker Level connections to sub(s)


Although many hybrid systems and subwoofers offer the line level option, manufacturers and distributor seem always to recommend speaker level. The line level option is normally quoted as best with multi-speaker AV systems.

With my AGs, I recently tested using line level with both parts getting full range input. OK but not as good as speaker level to all. My amplifier offers cut-off of sub output (line level) and cut-in of main output (speaker level) - effectively passive crossover. I tried this but wasn't convinced that it was any better than the simple speaker level to all - so that's where I am now.

Regarding time alignment, as the sub drivers gets their signal after 2 amplifiers and the rest after just one, it's worth experimenting with phase. If by switching the sub input cables the volume at crossover frequency range increases, then use that connection as otherwise your speakers are fighting one another.

I run a wireless connection to my subwoofer via RCA outputs.

sleepysurf said:

Jonathan, you're right... no bass management with my C-J pre. However, the ML BalancedForce Subs have custom downloadable crossover filters. I'm running my ML Expressions full range, with dual (stereo) BF 210 subs mainly to 1) partially overcome a bass null at ~50-60 Hz, and 2) to further pressurize the large (open floor plan) room.

Click to expand...

By definition, that arrangement results in extra bass, as there is no crossover involved before the feed to the Expressions, so it is outputting down to 20Hz (or wherever its natural roll-off is). That the BF210's are running a custom filter just means they might blend-in better to the Expressions at the top end of their range (probably around 80 to 90Hz), but from there on down, both the subs and the Expressions are reproducing the same signal, therefore 'double bass'. Now, as you state, you want/need the extra output to deal with room modes and preferences (we all like the low-end a bit 'hot').
The other challenge is that there is no time-alignment between the subs and the Expressions, so they could be either fighting or overly-reinforcing each other at certain frequencies with very large nulls or peaks based on distance from each other and room placement. When setting up my mid-bass modules, differences in timing made measurable differences in the group-dealy plots, down to the faction of a millisecond.

sleepysurf said:

Of note, the C-J Pre is phase inverting, so line level output to the subs is off 180 degrees vs. the Expressions. Although I can (and have) manually adjusted the BF 210's phase, I'm thinking the line-level approach might synergize better.

Click to expand...

Adjusting that control definetly can help, but it is a fairly coarse thing, measurements can help validate this. Also, use the line-level input that uses the crossover (in other words, not the LFE input) in the sub. Set the crossover to whatever works best in-room.
Line level should be the preferred connection, as you are feeding a signal that is NOT being 'modulated' by the ESL speaker. When feeding the speaker level as the sub input, you are getting a signal that reflects the interaction between the power amp and the ESL.

The ideal would be to run an active crossover between the CJ preamp and the power amp and the subs. Preferably, one that allows for time alignment of two independent sub-outs, which implies a 2-in, 4-out DSP-based unit.

sleepysurf said:

The "double bass" issue will only arise if I simultaneously feed them LFE from my old Denon home theater receiver, while also feeding bass via speaker (or line) level signal via the C-J Pre Home Theater Bypass. In that situation, I should be able to compensate (via Audyssey MultEQ or manually) in my receiver. Thus far, however, I haven't even hooked up LFE, as I primarily use the system for two channel listening. That will likely change now, as I just upgraded to a 77" LG OLED!


Over the next couple weeks, I'll play around with XTZ Room Analyzer measurements, and listening tests, and see what works best!

Click to expand...

You should be able to avoid the Double-Bass situation when using the Denon, as during set-up, you'd configure the Left/Right as 'Small', tell it you have a sub, and the Audyssey setup should be able to adjust delays and perform EQ so the blend of subs to mains is optimized for the room. The feed from the Denon subwoofer out should go into the 'LFE' inputs on the subs.

But when listening to content via the Denon (through the CJ HT Bypass), you definitely do NOT want to split the CJ line-level L/R outputs to the subs, so you need a way to toggle that.

But my advice is just to get a Marantz AV8805 and be done with it. That is one nice preamp / HT processor, super clean and even handles time-aligning 2 subs. Handles all modern 4K formats (for that lovely new LG). I have its predecessor, the 8802A, and love it. Only a Trinnov would be a step-up.

timm said:

Jon. Question for you. I have a sunfire sig cinema grand. Have you ever tried daisy chaining the rear and front channels in the rear of the amp - then going out from the amp rear channels into a descent? I think a descent only has line level. Do you think this setup would be better than out of the pre or might something blow up. . Just wonder if you had ever tried it in your travels with sunfire and ML.

Click to expand...

That would unconventional wiring, best to take the output from the 2-ch preamp, split it (ideally through a crossover), and feed the sub a line-level source.

Hear Here said:

> In the meantime, I'm curious about your thoughts re Line vs. Speaker Level connections to sub(s)


Although many hybrid systems and subwoofers offer the line level option, manufacturers and distributor seem always to recommend speaker level. The line level option is normally quoted as best with multi-speaker AV systems.

With my AGs, I recently tested using line level with both parts getting full range input. OK but not as good as speaker level to all. My amplifier offers cut-off of sub output (line level) and cut-in of main output (speaker level) - effectively passive crossover. I tried this but wasn't convinced that it was any better than the simple speaker level to all - so that's where I am now.

Regarding time alignment, as the sub drivers gets their signal after 2 amplifiers and the rest after just one, it's worth experimenting with phase. If by switching the sub input cables the volume at crossover frequency range increases, then use that connection as otherwise your speakers are fighting one another. ...

Click to expand...

Multi-speaker vs 2-ch means nothing when it comes to what is best for integrating a subwoofer into a system. Best results are achieved when the signal is approriately crossed over and time-aligned. Typically that means a crossover point between 60 and 80Hz between mains and sub. Even if the mains are 'large' and have good low-end extension. Placement, especially with ESLs, usually means they are NOT in a great location for the low-end frequencies, so best to let the sub handle that. Likewise, a sub needs the high-freqencies filtered out, and ideally, the signal is time-aligned so the blend with the mains is coherent.

Can't really do that effectively with speaker level signals, and as noted in my response above, the mains are modulating the signal from the amps, which means it is less acurate than line level.

After further comparisons, I'm sticking with speaker level connection to my subs. The bass is much tighter and coherent (presumably better time aligned), and more musical overall. Even when I adjusted the phase when using line-level inputs, the low end was always a bit muddy. FYI, I'm running the Expressions full range, using the "Bass Augmentation" filter in the two BF210's. The Expression woofers are so well integrated with the panel, I didn't want to "cut" their low end, in order to run the subs with the -10 dB (true crossover) filter option.

We're still in the process of redecorating our Family/Listening Room (new heavy drapes on order), so I'm waiting until after that for XTZ measurements. However, the improvement is quite apparent from listening alone.

If your setup has the option, I strongly suggest comparing line vs. speaker level connections. You might be pleasantly surprised! Of course, it also depends on your upstream gear, and room acoustics, so YMMV.

As I posted in another thread, I'm now using the downloaded BF 210 (MLF) filter that creates a true crossover with my Expression 13A's (with woofer controls initially set to -10 dB), then manually tweaking the 13A's woofer controls further, along with subs volume, for best overall bass response in my room (especially at main listening position).

Of note, I peeked at the actual contents of the two custom BF210 MLF files for the Expressions (using Windows Notepad), and discovered these differences in their high-pass frequencies...

FilterName: Expression ESL 13A (Bass reduced 10dB)
Phase Control Freqeuncy: 62 (somebody at ML needs a new spell checker <g>)
note: the frequency the phase controls operation is centred at - in Hz

FilterName: Expression ESL 13A (Bass Augment)
Phase Control Freqeuncy: 30 (sic)
note: the frequency the phase controls operation is centred at - in Hz

As I've mentioned before, the Expressions, in and of themselves, have superb bass that is well integrated with the panels. However, due to room geometry, I have a major bass null at my primary listening position (down ~10 dB between 50 - 60 Hz), and am unable to reposition the speakers or listening position, so added a pair of BF210's (right behind my couch) to try and smooth out the null.

In retrospect, it's obvious why running the subs with the Bass Augment MLF didn't fully solve the problem. Conversely, dialing down the Expressions woofers, and running the BF210's with the corresponding MLF fills in the null nicely. The only remaining issue was how to optimize the phase/timing between the main speakers and subs. Adjusting the sub phase control beyond 0° merely adds delay to the signal, and (in my case) just muddied the bass, so I left the phase control at 0°, and am now "twiddling" with the Expressions bass control... varying it between the recommended -10 dB to -5 dB, and listening/measuring (with XTZ Room Analyzer) to find the optimal synergy between mains and subs.

I'm making good progress, and will post some XTZ measurements shortly.

Glad to find this , I was going to post the same question, Any more info would be great , Still looking for Pre.

As mentioned, I've made great progress, illustrated by this XTZ Room Analyzer plot (single bass measurements only at primary listening position). This was just a quick measurement to show where I'm at, and I hope to do more extensive measurements later this week.



The key to overcoming the bass null (at least for my room), was to use the BF 210 MLF filter for a "true crossover" (ostensibly paired with the 13A's woofer set to - 10 dB). However, due to the actual acoustic interactions between the mains, subs, and room, the smoothest overall bass response ended up being with the woofers only dialed back to -4 dB, and the sub phase control at "180". Leaving the sub phase at "0" bumped up the combined response a bit, though only slightly audible. Again, however, this was measured only at my primary listening position, so I need to make sure the bass elsewhere in the room is not severely compromised.

sleepysurf said:

... As I've mentioned before, the Expressions, in and of themselves, have superb bass that is well integrated with the panels. However, due to room geometry, I have a major bass null at my primary listening position (down ~10 dB between 50 - 60 Hz), and am unable to reposition the speakers or listening position, so added a pair of BF210's (right behind my couch) to try and smooth out the null.
...

Click to expand...

Sounds like your situation is similar to mine, in that we have a large null near the MLP, and you might benefit from the same fix: a Nearfield Mid-Bass Module.

Given you want to stick with the CJ pre, you can still add MBMs, as all you need is to boost the 50 to 60Hz range, and you need to add delay (since they will be closer to the MLP).

You could then relocate the BF subs to locations where they help the overall low-end.

So adding a miniDSP paralleled on the CJs output (L/R inputs, summed inside the MiniDSP), set to a bandpass filter (high-pass 45Hz 48dB/Octave, low-pass 80hz 12dB octave), set a baseline delay (1ms per Ft from mains) and connected to some amp driving the ported woofer box, and you'd be set.

If you want to test this out, it's not much coin to figure it out, here are the parts:

First, this clever little ported sub, perfectly symmetrical opposed drivers, so it won't shake, and slim, so it can go just behind or even under the couch.
https://www.parts-express.com/dayto...driver-low-profile-passive-subwoofer--300-495 Heck, use two.

Then use a Pro-audio amp that has built-in DSP capable of a bandpass filter and with variable delay (less than $500) and you are set. Or a minDSP + some left-over amp you might have.

Based on those measurements, I'd think the 0 degree phase setting would be the prefered one.

And yes, big hole due to room modes at MLP.

Does XTZ have a waterfall plot? I'd be curious to see that as well. Gated to at least 300ms, 400ms prefered.

JonFo... I agree with your suggestions. However, my setup is in our Family Room, and space constraints limit options for alternate sub placement (other than behind the couch).

Of note, I hosted our local audiophile club yesterday. At the end of the session I ran my Expressions full-range without the subs, and most (if not all) felt that the overall bass response was better (despite the null)! I'm back to "square one" and will see what I can do running the Expressions "full range" with the "Bass Augment" filter for the subs. I'm also thinking of trying the Anthem STR Preamp, which could run ARC for the entire setup combined.

Re the waterfall plot, here's an enlarged view (from the prior measurement I posted above). It's actually surprisingly smooth, other than a slight bump around 63 Hz, where the Expressions and Subs overlapped. The yellow vertical line is 50 ms. The RT60 is also pretty good (uniformly <0.5, except for some ringing above 8K), but I didn't save that trace.

Brad225 said:

This is the way my old Vandersteen W2 subs were connected. To me it made since to me that with speaker level your subs would get the exact same signal as your mains.

That said I currently run my Depth i's on a line lever as it is easier.

Click to expand...

Ok, I don't think I have ever quoted my own post but ------.

Yesterday I decided to pull out the pair of speaker cables that I had previously run to the Vandersteen W2 subs when I had them.

I connected them to my amps and the Depth i on the front wall behind the power amps. Then connected the other 3 subs with the same cable that had come from the preamp to all of them. All i needed to do switch them to the proper "in or out" depending on where in the series they were.

The sound was much better and the controls seemed to have more effect than the line lever connection. I guess this proves in my system it's better.