ReL Subs: High Level or Low Level connection

There are advantages to both.  Low level with a high pass filter to your mains allows the sub to do all the work at low frequencies and takes some burden off your mains.  High level allows for easier integration imo.  I used the high level speakon connectors for my two RELs and haven’t looked back.  There are many around here who swear by low level and a filter.  I’ve not tried it but I’m extremely happy with the sound and integration I’m currently getting so I likely never will.

The only way to settle your quandary is to try in your system. Having said that, REL pride themselves on seamless integration through high level (speakon) connection. That’s how I am running my pair of REL’s. 

I just set up a S/510 for my Dad.   Awesome sub.  I used the Speakon connection and it sounds great.   I also have a REL in my second system and it is using Speakon also.   In my main system that sub was driven by the pre out .   I think it integrates better with Speakon and a low crossover setting 

Thanks all

Appreciate the input 

FYI, I have Anaylsis Plus cables with Speakons for the REL subs. The cables don't work with 2 pairs of spades on my Pass INT-25 (probably the same on your INT-60) due to the plastic protection caps on the speaker terminals.  You can run the sub cables off the speaker instead.  That also saves on cable length.

You likely already know this, but I forgot to say that the crossover setting on the sub is critical to getting it integrated.  Obviously it’s speaker dependent but I started with mine too low.  

Initially, I agree with lalitk. I'll say my extremely short lived experience with REL  favored using the low level signal.

Relocating the sub-bass speaker and equalizing the low level signal greatly improved every aspect of the product. Except for its dramatic -6dB roll off beginning in the mid 30Hz region. It remained void of any worthwhile desirable and delicate subsonic output present on many recordings. A degree of which is provided by most all -3dB subwoofers.

Personal taste is everything.

@oddiofyl and @jastralfu, what crossover level setting would you recommend?

I too, have a single Rel S510, and my speakers are 3-way, floorstanders (PMC Fact 12s). My integrated is darTZeel LHC-208 Mk2. Currently I have the crossover at 40Hz. Would appreciate your inpout.

I attach 2 RELs together with AQ screw-on spades to attach to the amp, currently a Pass XA-25. Low level inputs on the RELs have never interested me as you need long RCAs which are generally a bad idea, and the high level makes more sense.

I'm a learned person and it seems logical to me that low level inputs would be better.

But I've known people with REL subs who claim the high level inputs are better and the sound of their systems confirms it sounds great.  I think the REL is designed to use the high level inputs and that's how I would go if I needed subs.

Not a fan of adding a crossover as I prefer my music minimally processed.  

Jerry

Not a fan of adding a crossover as I prefer my music minimally processed.

+1 @carlsbad.  I have two REL in each of my two stereo systems, and have tried low level and high level inputs.  The high level (speakon) was the way to go for me, blending better (seamlessly) and improving everything.  I still run my floor standing speakers full range.  And the REL Baseline Blue was the way to go without breaking the bank on sub wires.

For me hi level is best. I’m sure there are advantages for low level with some systems. I have two EVO 400 amps plus 2 REL 212SX. My main speakers are connected to the 4 ohm tap and the RELs to the 8. It is an ideal situation in my opinion. The hi-level adjustments are easy to integrate with the main speakers. 

I like to run my mains full range, never with any type of high pass going to my Amp.  With a low crossover the REL will never call attention to itself.   

I start with RELs recommended volume initially and the crossover set to 25 and slowly work my way up with a bunch of different material until the sub disappears and does no harm, only making itself known when the content demands it. 

@thebingster I have both subs set somewhere around 60hz. I had them set too low previously and could hear the transition between my mains and the subs. I have stand mounts so that might make the transition more obvious when it’s not right but I could clearly hear it. I tuned it by ear by raising the crossover until the transition was smooth and seamless. What the correct crossover point for you is really speaker and room dependent so start somewhere just above the lowest frequency your speakers are rated and work your way up until the integration works for your ears.

After 50 years selling (beginning with the original M&K subs in 1974), designing, building, and using subwoofers in both home and professional live music here's what I know about connecting subwoofers.  There are no advantages to using high (speaker) level connections except convenience or accommodating equipment without low (preamp) level connections. The only correct method of connecting a subwoofer is via a high pass filter to the mains and low password filter to the sub(s). The HP/LP configuration minimizes LF overload to your mains reducing intermodulation distortion from the LF content and improves system dynamic range by as much as 6dB - the equivalent of quadrupling your main amp power. Likewise the LP filter removes higher frequency content from the sub(s) and with it the coloration associated with sub trying to do the mains job. Any HF content from a sub muddies the lower midrange and adversely impacts an accurate soundstage and imaging by creating a third ill-placed source for both channels lower midrange content. While other suboptimal connections may function, they are compromised in one or more aspects and never desirable. Placement of the HP/LP filter may be be in the increasingly common LFE preamp outputs, a separate component, or in the sub itself. In the latter case, longer interconnects are typically required to enable proper sub placement both to and from, so this is less desirable due to potential long cable issues. Crossover frequency and slope is largely situational, but in general keeping crossover frequency at 80 Hz or less is desirable as are steeper 12/18/24 dB per octave crossover slopes. Finally, placement is also largely situational although avoiding known room node points (e.g. halfway down a room's length) is a good starting point. 

I have 2 RELs and I've tried both connections with a couple of different amps. High-level is the way to go IMO. 

That way the RELs are fed exactly the same signal as your mains rather than a filtered signal.

If you go with Speakon connections I highly recommend you upgrade the stock cables. Frank at Signal Cable makes a high quality custom cable  for around 1/2 the price of the REL Bassline Blue cables. 

I have two S/510.  For two channel, they are connected via high level with Analysis Plus wires.  I also do home theatre via a pass through on my preamp. I'm connected to the LFE input from my surround processor.  Seems to work well.

I want my mains to run full range for two channel. 

High level is what REL's designed for, and my experience this best. I've experimented and continue to experiment with high level cables, thus far stock, Duelund tin plated copper, always Neutrik connectors not the cheapo copies. Both stock and Duelund litz wire, next will be VH Audio UniCrystal Airlock, solid core wire. Also various configurations of hookup to my 300B monoblocks vs 845 stereo amps. Finally power cords.

So many variables, not to mention crossover and level on subs, almost forgot to include running on same dedicated circuit as amps with added outlet. Some complain about lack of adjustment with REL's, that's not me. I much prefer the REL's integration vs the low level with DSP I've tried with other subs designed for low level outs.

I connect using high level with Neutrik SpeakOn connectors which are recommended by REL, never look back.

sns "I much prefer the REL’s integration vs the low level with DSP I’ve tried with other subs designed for low level outs."

What make and model of third party DSP or the make and model subwoofer with onboard low level input processing did you try?

If those "other subs" low frequency were rated at -3dB how did you determine their position within your room?

Low level only. Passive is best. 

I forgot to say why. An opinion should always be followed by a reason. Subwoofer drivers are powerful linear motors. They are also powerful linear generators and produce back EMF (electromotive force) This feeds into the output of the amplifier and effects everything else the amp is doing. Then there is the matter of an effective steep 2 way crossover. The low pass filter that comes with most subwoofers is like putting a marathon runner on crutches. The best they can do is  is generally 24 dB/oct. To keep the subwoofer out of the midrange these shallow slopes force the user to push the crossover so low that it is ineffective for most music and there is no benefit for the main amp and speakers. A subwoofer running up to 100 Hz has to be crossed at 48 dB/oct to keep it out of the midrange. Main amps and speakers benefit most from being crossed out at 80-100 Hz depending on the speaker. Two way crossovers are all low level. Digital is best.

Passive subwoofers have the potential to be superior to subs with plate amps. Closing an amplifier in a box is the antithesis of usual amp design with huge heat sinks or fans. Any amp run hard, including class D amps, are going to get hot. subwoofer drivers already have enough trouble dissipating heat. They do not need another heat producing device in their home. For a group of people who insist on putting their electronics on isolation platforms I find it interesting that they would except putting an amp in a vibration machine even though vibration does not affect electronics. Outboard amps are superior to plate amps. QSC makes the PL380, a glorious subwoofer amp at a reasonable price.  

I run pairs of RELs in 4 out of my 6 systems. All connected via high level. Some with the upgraded bassline blue cables, others with the stock speakon cables.

I also run RCA’s for LFE to a pair of S510’s in my home theatre. I agree with other commenters above that it is worth a shot to try it both ways and see which you like better.

mijostyn   Your's was an informative ah-ha post for me.

Hacks that we are, despite the systems star grounding we assumed a grounding issue but were very hesitant to lift the amplifier ground.

The three of us could hear a noticeable issue when those high level cables were connected to the JC-1 amplifiers that were powering the system. It wasn't a huge issue but once we identified it became one of those things you couldn't help but hear.  

Mijostyn

Thank you for all that info.

Some a bit over my head.

Does what you say apply to SUBS with an amp in them ?

For instance my Rel S/510's?

Or just to passive subs?

Thank you

@oddiofyle

I like to run my mains full range, never with any type of high pass going to my Amp.  With a low crossover the REL will never call attention to itself. 

Does that mean you are running 'low level"'?

No, running mains full range and driving sub via speakon cn.   I have a Velodyne SMS 1 that I used to use with the REL but I took it out and went speaker level off the same binding posts as speakers.   I ran that RCA and single cable out of that to sub.   I set the crossover low, at around 40 Hz.  Never calls attention to itself 

The 40 step  X - over knob on a REL  that is marked 25 Hz to 100 Hz is about 1.8 dB per step.  

@fastfreight

Please share your thoughts/ experience with the upgrade to the bass line blue cable. I'm running 2x S/510's with class D monoblocks (1 connected to each amp). I upgraded power cables to Shunyata and that made a noticeable difference in sound quality. I also bought some speakon connectors and was thinking about making my own version of the blueline cables but with some better quality wires.

Hi @veerossi

i found the Baseline Blue cables to be fine for sub high level connections.  I have nice cables everywhere, but do find the sub cables the least impactful.  I certainly looked at other options, but I have one long run of 30’ under the floor and across the room, and never felt the need to upgrade more. I am sure you can make better cables with nice copper wire.  Understand your connections first as you may likely only need two wires vs the three in a REL wire.

My Rel 812's work quite well with the Audion Mk3's using the high level connections. The Audions let me evaluate sub settings more accurately than did my tube amps.

Thanks for this info @fastfreight. I concur: sub cables are the least impactful. Yes, I’m using only 2 wires on each sub. Using all 3 was far too much.

If you could go back, would you spend the money on the Baseline Blue again?

Hi again @veerossi.  I would get them again, it makes me feel better!  And due to the long run the larger wire is probably a good idea.  I have some extra ones if you are interested pm me!

I have researched the high level option for driving subwoofers and according to Paul McGowen there is virtually no impact on the performance on the amplifiers when driving the subwoofer's high level inputs.  According to him the impedance of the high level inputs to the sub are so high that there is no impact on the performance of the amp.

I have a pair of T/i subs in my two channel system. I have both connections laid out depending on amp. Yes, the RCA's are a long run (purchased new from SVS..excellent people to deal with) but IMO based on my system and ears I prefer the low level connection. I feel it gives you more "head room" to make adjustments on the rear and allows the subs to do what they're suppose to do.

Appreciate all the input

Sounds like a HiFi debate

Equal numbers on both sides of the issue

I just compared using Hi level vs low level

At a given amp level and the same music the high level is 1-2 db higher than when using low level using my Pass Labs INT-60

High level sounds a bit better to my ears.

I'm a little disappointed as I was hoping to sell these baseline blues