Best way to add and cross-over dual subs in a 2-channel system?

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2FlyingYorkies

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This post could go in any one of several sub-forums, but I'm going to put it here as being multi-subject, and therefore "general". (mods, feel free to move)

I'm looking to add a pair of subs to my dedicated 2-channel system listed in my signature. I can see a couple of ways of doing this, and am curious how the rest of you have done it. A few options that came to mind:

1) Add the subs using the 2nd output on my preamp, use the sub's internal low-pass and let the Sopras continue to run full range;
2) Add some sort of active crossover between the pre- and power-amps (suggestions for which crossover?);
3) Migrate to a completely new front end (combined dac/pre?) with built in bass management and potentially room correction (suggestions?)

The goal is to fill in the last octave below where the Sopras start to run out of oomph (16-35hz, though I'd consider stretching it up to 60hz with the right subs and equipment). Big open-concept irregularly shaped multi-use living space that sounds surprisingly good as-is despite being an on-paper disaster for good audio. Budget depends on the complexity of the solution, but let's call it up to $10k plus the subs themselves.

I see pros and cons to all three paths, hence seeking the collective wisdom of the group...

Oh, and if anyone has a favorite sub (or stereo pair) that would visually and acoustically match my gloss carrara white Sopras, even better.
 
I've found the sub out from my preamp to be the easiest when I had my two SVS 2000 Pros hooked up to my system. SVS have a app that uses bluetooth to connect and control phase, crossover and volume if you choose not to use the controls on the back of the subs. If you only have one sub out from your preamp a splitter can be used to feed each sub. Dual sub outs often allow for a stereo low frequency sent to each sub. That is what I used from my Gryphon Diablo 300.

PS, the two SVS 2000 pros are boxed up and sitting in my garage waiting for me to decide what to do with. If your interested in the SVS line drop me a message. Good luck
 
Most people let the mains roll off naturally and cross the sub at the point where it best blends with the mains.

REL allows connection to the speaker terminals. That was their preferred method. As mentioned already many use the second preamp out which is fine.

If you did want to look at a preamp Anthem makes a stereo preamp with bass management and DSP.
 
I would go with option 1. Let your mains roll off naturally then use the flexibility of your two subs placement to smooth out the lowest end from there.

If your mains have a ‘suck out’ because of their room placement, your sub placement may be able to ameliorate that. Experimentation is key.

I have tried an external crossover before. The MEN220 from McIntosh and the JL Audio crossover. Both had their pluses but also added artifacts. I found your option 1 to be the best.

Good luck.
 
When you add subs you become a speaker designer, even if you didn’t want to be one. :)

Sub placement with respect to room boundaries and the mains will have more of an impact on the final result than how you choose to integrate the subs.

For my HT, I use dedicated bass management and time alignment to account for the 1 mSec delay in the subs due to their internal DSP processing.

For 2 channel all that goes away and I just run my mains full range.

I would try the pre-out route as that is usually the easiest.
 
Most preamps have two speaker outputs (one balance output and one RCA output).
Option 1 (no external equipment)
Run one of those outputs to your main speakers. Run the other to the first sub.
Many subs allow you to run one of them as a master and the other as a slave. So you would connect the output from your preamp to the master sub. Then run a cable from the master sub to the slave sub.
You can then use the internal filters in the master sub to control the crossover.
Important: the location of the subs is actually more important than the crossover frequency. You can google and learn about different ways to find the best location for the subs. It will depend on your room.

Option 2 (with external crossover)
You could use a MiniDSP device. More information here: https://www.minidsp.com/applications/digital-crossovers/194-subwoofer-integration-with-minidsp

Option 3.
Adding Room correction (DSP) is a completely different subject. DSP can be added to the two options above. There many threads on this subject in ASR.

Note: If you stream your music, there are several streamers (like WiiM Pro and others) that allow you to add DSP to any system without the need for special equipment or software.
 
Sounds like Option 1 is the way to go, at least for starters. "Cheap and easy" is always welcome, especially if it turns out to work! :)
 
For what it is worth. On my system running the subs from the speaker connection of the amps sounds much better.
It allows the controls to have much more of an effect on the sound than a connection from the preamp.
I have no clue why, it just does.
 
I have two systems with dual subs. My main setup has two SVS SB-4000 subs that are connected as you describe in option one. I have the crossover point on the subs set at 80 Hz like the THX guys recommend, using the volume control on the SVS app to integrate them so the Odeons run full range.

The other system is much more modest. I’ve found it to be to my advantage to use the ACI Force sub’s crossovers, and run the hi-pass out to the Fosi V3 monos, and from them to the Triangle Borea BR03 speakers. This little system performs well above its price point (in my opinion, of course) by wiring it in this fashion. Relieving the Fosi monos and the BR03s of responsibility for reproducing frequencies below 80 Hz seems to have had noticeable benefit.

So I guess the answer is, as with many things in this hobby, it depends. My own experience was that bypassing the internal crossovers was a preferable arrangement, because running through them caused noticeable (to me) degradation of the sound with my Odeons. I’m unfamiliar with your equipment, but it appears to be a very nice setup. How relieving the mains of lower frequencies might benefit you at a cost of running the mains signal through additional crossovers is a question only you can answer. Good luck. I’ll be interested to hear what you decide on.
 
brad225 said:
For what it is worth. On my system running the subs from the speaker connection of the amps sounds much better.
It allows the controls to have much more of an effect on the sound than a connection from the preamp.
I have no clue why, it just does.
Click to expand...
Yup, I have heard many subs that sound better from the speaker connection than from the "line out" connection on the preamp. Makes no sense to me but it is what it is....
 
2FlyingYorkies said:
This post could go in any one of several sub-forums, but I'm going to put it here as being multi-subject, and therefore "general". (mods, feel free to move)

I'm looking to add a pair of subs to my dedicated 2-channel system listed in my signature. I can see a couple of ways of doing this, and am curious how the rest of you have done it. A few options that came to mind:

1) Add the subs using the 2nd output on my preamp, use the sub's internal low-pass and let the Sopras continue to run full range;
2) Add some sort of active crossover between the pre- and power-amps (suggestions for which crossover?);
3) Migrate to a completely new front end (combined dac/pre?) with built in bass management and potentially room correction (suggestions?)

The goal is to fill in the last octave below where the Sopras start to run out of oomph (16-35hz, though I'd consider stretching it up to 60hz with the right subs and equipment). Big open-concept irregularly shaped multi-use living space that sounds surprisingly good as-is despite being an on-paper disaster for good audio. Budget depends on the complexity of the solution, but let's call it up to $10k plus the subs themselves.

I see pros and cons to all three paths, hence seeking the collective wisdom of the group...

Oh, and if anyone has a favorite sub (or stereo pair) that would visually and acoustically match my gloss carrara white Sopras, even better.
Click to expand...
There are many ways… here is the Obsessive way 👇
 
Some subs work from the speaker connections and some do not. I think It’s a matter of design not which is better. Case in point : RELs work off the speaker connections, JL Audio subs do not.

Could argue forever which is ‘better’ after we argue over what ‘better’ is.
 
I ended up purchasing a pair of Arendal 1723 Subwoofer 2S (sealed, dual-opposing 13.8" drivers, 1200w RMS amp in each, finished in satin black, which matches my racks surprisingly well). I connected them using the second set of balanced outputs from my existing preamp using stock power cords into dedicated 20A outlets and Belden 1800F / BlueJeans Cable XLRs as a starting point. Here's what I've done so far to try and integrate them:

1. Position in the room was determined by available space and spousal acceptance. They're both essentially tucked into what corners the room offers, sitting next to the Sopras on the outboard side of each.​
2. Crossover frequency initially selected by playing some test tones on the Sopras and using a dB meter to see where they started to roll off. Picked 50hz as a "probably too high" starting point.​
3. Set a nominal comfortable volume at listening position using the crossover frequency test tone on one Sopra (other speaker disconnected, both subs off)​
4. Used sub gain control to set the same volume using only the matching sub​
5. Inverted phase on the Sopra by swapping speaker wire inputs at the speaker​
6. Adjusted sub phase by playing test tone on both the sub and inverted-phase speaker and adjusting the sub's phase control until min volume was noted at the listening position (i.e. find the null). Restored correct speaker connections so the null turns into a reinforcement​
7. Repeat with the other speaker/sub​
8. Check levels again with everything playing. Dialed the sub gain back just a bit to account for both subs in unison​
9. Repeat test tone sweep to see where levels fall off, or if I created any new peaks.​
10. Adjust as needed. For now I'm crossing somewhere between 40 and 45hz and am reasonably happy. I think 50hz hit a room mode - that frequency ended up hotter than surrounding ones and gave a false impression of being the start of the Sopra's rolloff. If I did it again, I'd probably start my frequency sweep as high as 80hz to try and better differentiate between speaker rolloff and mid-bass room gain.​

Overall I'm happy with this as a starting point. I'm sure I'll tweak some more. I should probably do some more formal measurements using Room EQ Wizard (or similar) to better identify room modes. These subs don't have room correction built in, but they do have a multiband Parametric EQ that I could use for some basic adjustments. I was a bit surprised to find that my phase (and time delay) adjustments on the subs were both essentially zero. Probably a result of the subs sitting so close to the mains and using equal length cables throughout. I was still somewhat expecting to have to delay the subs somewhat (a full cycle?) to account for the internal sub DSP, but that proved unnecessary.

Happy to hear feedback and advice on what I've done so far. Assuming the group doesn't think I've done anything so terrible it needs immediate change, I plan to tweak crossover and level using familiar tracks by ear. I don't think I'll need a whole lot more -it sounds pretty good already. Effortless 16hz organ pipes and much improved mid-bass slam, but nothing "chesty" or congested.
 
FWIW, I run a pair of SVS SB-4000 subs on a set of preamp out jacks with the mains running full range. I had initially set them up in similar fashion to what you’ve done, but a friend who also happens to be an EE laughed at me, telling me that I wasn’t getting the impact to the system I had paid for. He claims the THX guys told him to cross the subs over at 80 Hz and integrate them with the volume control. I do use the eq on the subs to put a bit of a dip at the point of overlap.

With the measuring setup you have, you could undoubtedly integrate them better than I have mine, but if it’s easy, might be worth a try.
 
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