Adventures With Subwoofers

That is strange, especially when you were able to set the crossover on the sub to 25Hz.  My experience is that with subs properly positioned and calibrated imaging improves and the soundstage expands and think that should be no different with your Harbeths.  I’m perplexed. 

@soix 

So was I. But to my ears I lost air and soundstage openness with the sub even at a 25 Hz crossover. I’m just sensitive to that area of the frequency range. Probably 60-120 Hz. Not subtle to me. I did experience a minor soundstage expansion and slight improvement of depth but again at the expense of openness. Also with the sub a perceptible warming of strings. Less ethereal and airy. The image slightly more forward. When I turned off the sub it was like someone turned on the lights over the orchestra. It was more airy. Don’t know what to tell you but I’ve been experimenting with this for a year. I just prefer the overall sonic with the Harbeth without the sub. I really wanted the sub to work. 

As I mentioned recently elsewhere. That has been my experience with subs-woofers as well. In addition to two subs I used to have a low frequency subwoofer equalizer... so it did not operate on the main speakers. Still the same problem, bumps somewhere... and lack of coherence.

I was really happy and stunned with my then new Sonus Faber Amati Traditional without subwoofers. I suddenly understood what coherence sounded like. The Amati are about flat to 28hz, so I really don’t feel I am missing anything and the character of the sound is beautifully homogeneous. So, I got rid of the subs and are really happy. If at some point I want more bass, I’ll upgrade to Sonus Faber Lilium (20hz - 20khz). 

Couple of things.  I've heard these effects and heard them solved.  I suspect one of these issues: 

• Not high passing the main speakers
  • Alternatively plug them if ported
• Not a steep enough low pass on the woofer
• Unexpectedly bad resonances being created by the sub.  
  • These can add 20 dB (i.e. 20x) of output in very narrow bands.  Can be effectively tamed by an EQ

Of course, the easiest solution is to start with measurements. 

You gentlemen have run into something I've known for a while, that subs don't alays just drop into place and can require  significant work to integrate.  The audiophile habit of trying to configure speakers and subs by spec instead of measuring how they are performing IN ROOM makes it very difficult. 

Best of luck,

Erik

@soix +1  

Unlike your dramatically rolled off -6dB sub-bass woofer the first step when switching to a -3dB subwoofer is to simply drop the sub into one of YOUR rooms strongest standing wave bass modes. Unfortunately most manufactures of subwoofers simply don't get this critical first step. JL Audio is no exception. 

Did you happen to try reversing the polarity of the subs at all?

I had the same speaker with an SVS 16 and thought it really helped steady the image and deepen the experience. Mayne my hearing is off and I didn't notice the nuances, or maybe room dependent as it mostly is.

Some of those Rel subs are not rated very low. I suppose it's a niche to make a sub that only goes down to 35hz, but for my purposes I'd say you want something more like the s812 with those speakers.

My issue with the C7's were with volume. They play loud but once you throw a little bass at them and the driver would bottom out.  Other than that I loved them. The clarity and energy with the lack of fatigue or aggression is great.

Proper sub integration takes a lot of time and effort. If you are a seasoned audio aficionado and have lived long without subs, it becomes easier to understand when subs add smearing and cause issues more than help. In my experience, this is not just about the crossover point and slope, but also equally as much to do with phase and time alignment, and maybe even more so.
 

The challenge with REL is that integration of their subs is typically limited to adjusting the crossover and positioning them, as phase is limited to 0 or 180 degrees, and most models do not have other features such as delay or parametric EQ. If you were to play with subs fromPerlisten (I’m an authorized Perlisten dealer, FYI), SVS (previous owner), or Martin Logan, their subs can be dialed in from your listening chair. When you can do this and adjust phase by degree, delay by millisecond, and crossover frequency by Hertz (as well as its slope), you’ll be amazed at how much easier it is to dial the sub into your system and get favorable results. Of course, sub build quality is very important. While SVS does wonders for the money, Perlisten and Martin Logan offer products that are a huge step above.

As others have mentioned, many of RELs offerings are meant to operate in the audible range and augment musical information into the subs (e.g. they don’t go that low). To experience the benefits of a wider, deeper soundstage and a more coherent presentation across the entire frequency spectrum (and not just in the lows), the sub should be dialed in using the features mentioned above, but in reality the sub also needs to go down to at least 20Hz, and preferably below. 

In my reference system, I employ two Perlisten D12s subs. A few of my clients have had me configure swarms of their larger subwoofers. In some cases they are crossed as low as 31-34Hz, and with proper integration in any system I’ve configured subs, you can barely hear them when the amplifier is off. But what they do to eliminate room modes, clean up the entire frequency spectrum, and add immediacy and texture to the sound can be accomplished by little else (BACCH-SP’s DSP innovations come to mind here). 

I used a miniDSP to my sub only (Rythmik F12SE) to blend sub integration. Was able to get a relatively flat frequency response as measured with Audyssey MultiEQ-X & the Audyssey microphone with a known frequency response. 
My next step is to use the UMIK-1 with REW. 

I use an SVS sub which has very comprehensive DSP over most parameters. Changing the rolloff to 24db instead of 12 makes a huge difference in how it interacts with the mains. I also use a 24db HPF on my mains to reduce the bleed. I tried two subs but found one works better in my room. 

Integrating a sub takes time and effort. How many, location, filter settings, EQ, and phase all work together in complex ways. It's not much different than setting up your mains. Listening, measuring, trial and error with settings, and sufficient time are all part of the process. 

I have a pair of rel subs that I have setup where you can’t tell where the subs are located and you think the bass is coming out of the revels.

what model rel to get is room dependent. Some people say the t5x are very musical. I went with the bigger rels.

With all due respect, if you asked an AI bot, "What is the weakest link in my system?" the answer would be the main speakers.  The mains are rolling off at 45hz.  That makes for a big ask to get subs to integrate seamlessly.   

With that in mind there are a couple of things that you can do to optimize what you have working in your room.  Pass off your subs at max 45hz with a 24db slope as your already discovered.  Phase is a moving target so getting the phase organically in-line without electronic correction is paramount.  For a starting point, set your subs outside of the mains, and at least a few inches forward of the mains to compensate for the natural delay of the lower frequency signal.  This should help keep the subs from knitting into the mid-bass range and keep things clean.  Good luck and cheers.  

@ozzy 

Yes that’s been my experience. Even with a 24db slope and a low crossover the midrange  transparency is compromised. Yes you get more low end but the overall presentation is warmer or darker. I also find the soundstage is slightly forward.  After a year of experimenting I’m enjoying the more open transparent soundstage without the sub. 

@ozzy It has more to do with phasing than it does with a crossover point and slope. It’s not necessarily that the subs at that combination makes frequencies that match the tinkle you’re hearing, but that some of those frequencies may intersect with that tinkle sound. For example, if that sound is at 1KHz, all divisible frequencies, like 500Hz, 250, 125, etc, if perfectly time aligned, intersect at intervals of the 1KHz frequency. Add phasing shifts, and that 1KHz frequency is affected, typically by smearing it. With proper phase and time alignment, the crossover point is more forgiving, not that it should be set any more than it needs to.

Not sure what's causing your difficulty, as you describe it all, it doesn't seem like you should have any issues. I have an F113v2 and a JL CR1 in my ARC REF160s/ARC ls28se/ Wilson Sasha 2 set up in a 12x22 room- sounds great and the Boz Skaggs song couples to the room really well. I have GIK bass absorbers in the front and rear corners and they make a difference. I also trim down 150 hz area with Roon EQ. I just added a pair of REL S812 and run them instead of the JL for the time being. The REL going plenty deep and are plenty powerful, more musical than the JL set up I think too. You may need to just keep playing around with placement etc. 

I could get my old Velodyne servo sub to integrate well with my Harbeth C7s (unlike with my Spica TC-50s in which the bass was close to being flat down to 20 hz).

I’ve been able to get my Arendal sub to integrate well with my LRS+ in my 2.1 bedroom home theater system but only by setting the low pass filter to 35hz and using 24db slope.  Otherwise even dialogue does not sound as pure.

Sorry- I meant to say that I could NOT get the Harbeths to integrate.

@saboros 

Just my experience but I believe the open, transparent and natural midrange of the Harbeth C7 is easily compromised by subwoofers. This is especially true of the C7.  I compared it to the Harbeth 30 and 5. It was that airy and expansive midrange that sold me. Just presented a beautifully wide ranging soundstage and life like imaging. So this subwoofer issue may be more apparent with C7. 

I use a soundmeter app and streamed whitenoise to ballpark the sub integration initially, then fine tune by ear from there.  Works nicely!  Very fast and easy.

I look for level, crossover, and phase adjustments on any sub I would consider. Some newer subs from some vendors like SVS for example include DSP functionality with an app to help integrate, which sound like a very nice feature!  Might be trying that soon.

Currently I have a Klipsch sr308 sub integrated to a tee (to my ears and based on measurements) with KEF ls50 metas and the sound is awesome...dare I say pretty much perfect?

Note that in addition for streaming I have Roon DSP applied for room correction and to custom tailor to my ears from there as needed all the time.   Once you have good gear setup and integrated well, this is the ultimate tweak needed to make thing sound just right!!!!  Do it!

I've been using a pair of REL S812's with Sonus Faber Il Cremonese which are flat to 35Hz.  The RELs are -6dB at 19 Hz.  The RELs are located 2' out from the corners of my 19' x 23' room in the same plane as my speakers and located outside of them.  In addition the speakers' Intrawoofers are aimed towards the walls of my room.  After several iterations during months of listening, I arrived at a crossover point for the REL set at ~30-35 Hz, and the volume at ~ 9 o'clock as I'm only seeking to subtly capture the ambience of the recorded space.  Very pleased with the results.

Someone just mentioned subwoofer volume.  There was a recent thread on Agon where this was discussed and turning down both the crossover frequency and the volume on my sub did wonders to clean up the sound in general and reduce the localization of the bass in my room at certain frequencies.  This for a single sub application in a medium sized room.

As for REL subs, it has been suggested already that the S/812 would be a better match for the C7’s than the T5/X, and I agree.  If your room is on the smaller side, the S/512 might be better, or even the Classic 99, less hammer, more dulcimer.  The lack of crossover slope adjustment to match the ported C7 may be an Achilles heal for REL, but I have not heard this complaint before related to paring with Harbeths.

kn

There is also this:  https://rel.net/pages/speaker-pairings

I have had consistent success in adding a sub (first the SVS SB1000, then a JLAudio e110) to my home office’s desktop system. There are 2 keys to success, in my experience:

1 - I use an external crossover with 24 dB/octave high- & low-pass filter slopes.

2 - I can run the speakers full range if I wish, but I find it’s absolutely critical to use a high-pass filter to cut off frequencies below the point where the sub will operate. Failure to do this creates a muddy, indistinct and bloated sound in the upper bass and lower midrange.

3 - Finally, I use sealed/acoustic suspension mains and sub. I find this design gives not only the most predictable, easy-to-manage bass overall, but also give bass that is qualitatively better than ported designs. This is ideal for music-only listenings. I might feel differently if I was using the sub in a home theater, but for music appreciation, sealed/acoustic suspension mains & sub give me the best results.

Just get an SVS sub and enjoy your system. Also try running your mains full range to keep the electronic xover distortion out of them.

Feim my Adventures with Subwoofers, here are some things that seem critical to solving integration.

Firstly, low end highlights smearing most. If your source is allowing smearing, focus on that otherwise the rest will be a battle.  For example, noise in you ethernet system is, in my experience, a damaging source of noise that causes smearing. Also subs power cables, interconnects and fuses all contribute.

Next, you need to be able to place subeoofers according to room acoustics, which means you need to be able to delay the main speaker output.  Adjusting phase might sound similar, but it's a convenient short cut.

Delay needs to account for not only distance but also the latency of the subwoofer - it's filters, amp, acoustic design, etc.  This is not to say subs are slow,just a tad late.  12ms is alot later than 4ms.  It's enough to cause smearing.

It's best to control the slopes of both the subs and the mains, so both HP and LP filters are needed.  The volume level of the sub can ruin the crossover blending 

24dB slope better than 12dB because it's over less frequency range.

Choose a crossover frequency that allows best tone,which may be influences by placement of the sub/s and their interaction with the room.

All this dialing in should be the foundation, the neutral/correct, for then choosing what you prefer.  EQ can help tune to suit preference if you prefer a less neutral ... suits you hearing (eg. change with age).

I hope this is helpful.

Dear jfrmusic, this needs to be approached scientifically if you hope to achieve proper integration of subs into your system. You have some really nice kit and it's worth doing what is necessary to hear what it's capable of.

The only way to do this without endless experimentation is to embrace measurement so please download REW (free) and buy a suitable mic. for $100 which will remove the guesswork. There has been some good advice here in certain repects but most of it is all over the place and confusing. Best is to go about things methodically.

Any sub like REL and its ilk are unsuitable for 1 reason: they do not have variable phase. It's also easier and better to use sealed subs which your D108 is and has a natural 12dB/octave roll-off so plug the ports on your speakers which force them to now behave as a sealed box (a good thing)  which decays at 12dB/octave and so match the D108.  I suggest at least 2 subs  which is neccessary to truly smooth out the performance of speakers, extra bass sources (subs) and the huge influence of your room's acoustics. This brings into the picture the importance of plugging the Harbeth's ports. You have effectively removed 2 additional bass sources that resonate at only 1 specific frequency which by definition can not be tuned and will complicate set up. Point: AI has misled you claiming a 12dB slope. Your REL  has a passive radiator which rolls off slightly steeper than a ported design which is 24dB/octve.

Your D108 partnered with a sealed sub like the great value SVS SB 1000 PRO with numerous controls will allow you to achieve the industry standard of +/- 3dB across the spectrum. Without the ability to see the frequency response continually change as you adjust the controls you are left guessing. REW will also display if you have sufficient absorption or perhaps too much. As I mentioned it's a scientific approach which has been well documented. It works. 

A further bonus is the ability to place the subs where you would like them to be which is a function of continuously variable phase. Ignore the advice in posts above to place them behind or in front or whatever. I do recommend starting with 1 sub in a corner, any corner, and the other in the middle of the opposite wall. 

I state with confidence that you will not have a smeared image nor loss of air just the opposite. By using measurement and subs and some absorption you will have effectively removed the damaging effects of your room's acoustics and will hear the acoustics of the event. The audiophools holy grail is it not? 

For years I have put my Subs on an Aurelex Sub Dude isolation platform.   Cheapest way to eliminate boomy bass.   That and a low X over that does not excite room modes.  

My second system uses a pair of Studio Electric M4 , a sealed acoustic suspension speaker that has great bass.   I'm also using a sealed acoustic suspension REL sub.    I think this combination is the best sounding  Monitor/ Sub combo I've ever had , and I have had many.   I attribute it to both speakers being sealed, no ports.  

I suggest you look at the Vandersteen subs with their high pass filters.  

I saw you mentioned not having an external crossover. They do make high quality ones. I almost went that route myself. Spl makes one that comes highly recommended by various sub manufacturer’s. Pricey though. I bought speakers with more bass instead. 

Integrating subs is always a challenge without DSP. I couldn’t recommend Danville Signal Processing’s dspNexus operating at 192K or 384K which has 2 inputs and 8 outputs to amps. The team there is awesome and will help you build your crossovers as needed. Get the phase, delay, and room modes fixed measuring with Room EQ Wizard and put those results into Multi Sub Optimizer. The subs will blend seamlessly. It’s work, but well worth the effort. 

- Steve

* typo - “I couldn’t recommend more. . . “

@jfrmusic 

I had Harbeth C7ES3 and used JL Audio D110 subs.  After a while I noticed that the subs were nice, deep and punchy but created occasionally "hard" bass notes in conjunction with the speakers.  The deal breaker was that the sound lost dynamics and rhythm with the subs engaged.  

Five sets of subs and as many speakers later I finally realize that I have the best possible sound using speakers that have decent low end bandwidth and nix the subs.     Sure we can work out sub integration "on paper" with theoretical crossover points, level setting and even measuring the response with RTA software.  

At the end of the day listening matters and if you listen critically you will hear issues that the subs cause along with the thrilling deep notes that occasionally show up in music.   

If your speakers do not have enough octaves of bass get some that do.  

@avanti1960  Five sets!

Reading your of dissatisfaction sounds quite familiar. Could you describe where and how you determined these subwoofer's positioning within your room?

Integrating subs into a system and more important, a listening room can be a real challenge.

My listening room in our last house had terrible "room modes" in the low frequencies, the best I could do was to reduce the terrible, boomy bass with a LOT of bass traps; my wife characterized that as my "padded cell".  Yes, the low frequencies were better with the subs, but not ideal, even though these subs (JL Audio F113V2's) had really good power and DSP.

We moved to a new home where my audio room is the bonus room above the garage and these subs are definitely more than this room requires, but with just a few bass traps, they really added a lot to my enjoyment.  My latest improvement was to add a JL Audio CR-1 crossover, where I could better tune the system to the room, and had the portion of the musical spectrum that the subs were reproducing, removed from the main speakers and very much to my surprise, the detail in the bass region was very much improved.

@avanti1960 

I’m more than satisfied with the bass on my Harbeth C7s. I was hoping to improve the soundstage by pressurizing it with sub bass. But that came at the expense of compromising the midrange.