How To- Perfect Subwoofer Integration

If you love two-channel audio and want some extended bottom end but are reluctant to add a subwoofer, fear not because it can be done successfully. Unfortunately using the "by ear" method involves a lot of trial and error and in the end you are not completely sure you have the smoothest, most blended, most extended response your subwoofer / system is capable of.

Using a laptop, some RTA software (e.g. TrueRTA) a quality microphone and preamp and a full spectrum pink noise test CD you can take the guess work out of the process. Total cost for software, CD, mic and mic preamp was about $200.00. Not outrageous considering the investment in your system.

For proper subwoofer integration, the subwoofer you select will need the following features-

• Level control.
• Continuous phase control (0-180 degrees).
• Polarity / phase switch (normal / inverted).
• Crossover frequency control.

Most subwoofers have those features. Many do not have the continuous phase adjustment. This one happens to be critical for smooth integration. I would not recommend a subwoofer without this feature.
In my case I have the KEF LS50 speakers and integrated a JL Audio d110 subwoofer.

Step 1) Measure your speakers without subwoofer. Put the test CD in the player and play the full spectrum pink noise track (put it on repeat). Adjust the volume to where you listen most. Put the microphone at your listening spot as close to center / ear level as possible. The top of your couch / chair is fine.

The first pic below is the response of my system without subwoofer. The natural roll-off frequency (crossover) is 80Hz. This gives a good subwoofer crossover frequency starting point.

Step 2) Turn on the sub with these default settings-

Level control- half volume.
Continuous phase - 0 degrees
Polarity - inverted or 180 degrees out of phase (based on experience this is the default setting)
Crossover- set at the approximate roll-off frequency of your measured system. In this case- 80 Hz.

Step 3) Measure the sub at high output-

With the pink noise CD playing and the RTA software running, adjust the subwoofer volume until it is high enough in level to exceed the response of the main speakers. You want it higher so you can measure the actual subwoofer roll-off / crossover frequency. Adjust the crossover control lower / or higher until the roll-off frequency matches that of your speakers.

Step 4) Fine tune the sub level. Adjust the level control until it now matches or blends with that of your main speakers. I would recommend the subwoofer be no more than 2-db greater than the level of the speakers at the crossover frequency.

Step 5) Fine tune the crossover at normal level.

Once the sub level is matched to the speaker output, adjust the crossover slightly ONLY if there are any large peaks or valleys in the response as measured. You want to adjust the crossover slightly up and down to even out the response as flat as possible. If it isn't perfect, don't worry there is another step.

Step 6) Fine tune the continuous phase control.

If there are peaks/ valleys in the response, adjust the continuous phase dial and measure the response at 1/4 turn. 1/2 turn, 3/4 turn and full turn. Note the position where the response was smoothest. In my case there were still large peaks and valleys until I adjusted the continuous phase to just before the halfway point. Once you find the best position, adjust one more time up and down from your previous best and measure again.

Step 7) Road test.

Listen to a variety of music and see how it sounds. At this point the only recommended adjustment to make is the level control. In my case the sub was just a little too strong.

Adjust the level in fine increments until the level is blended. In my case, plus 2db was perfect as shown in the second picture.

The third picture shows final system response. Nearly flat down to 20Hz and measurements are true to the ear test, the system sounds deep yet proper, totally integrated and seamless. The subwoofer plays musical notes and works in perfect harmony with the main speakers with zero localization queues of the subwoofer as the source of the sound.

I have tried to do this by ear with many mobile and home systems and have never achieved the level of success you can get by using the RTA software process.
I'd be happy to walk anyone through the process in more detail or answer any questions.

 

Sounds overly complicated to me. Have always adjusted by ear successfully. Not saying perfectly, but pleasant to my ears at least. But good tutorial for those who want to go through the motions.

 

I own 2 Velodyne DD-15 subs with the built in EQ. The subs are dialed in at 3 out of 100 on the volume. The on board EQ is really something.

Tim

 

you're better than me then! i am cursed to be so particular / anal about the sound quality. until i learned how to use RTA software whenever i tried to setup a sub by ear i wound up fiddling with it constantly. so much that i ditched them altogether until recently.
the process ain't that bad either- you play a pink noise cd and fiddle with some knobs until the line on the screen is as flat as possible.

 

those are nice subs!
basically the process i described allows you to get the most out of a subwoofer that does not have room correction / EQ.

 

Is there a Mac-version of this software? Am sort of interested in learning about this process for myself but am totally Mac-immersed.

 

By no means I'm better than you man ! I admire you for being such a perfectionist. The procedure is not that complicated, it's only I'd die of an OCD attack if I followed it; I have OCD and try to fight it back. Would it sound better using your procedure ? Sure ! Would I like the result better ? Huhmmm.........I'm not so sure. Thanx for sharing anyway.

 

not sure this is possible...one record the level, position , etc is fine, next one you find yourself changing things again...not a fan of the subwoofer unless its in a HT set up to save your left and right speakers from explosions...

 

No harm will come to your speakers from explosions, it's only they will prolly not be properly reproduced and be less enjoyable than through a good sub. That's all. Once I heard music being played through a rig with a sub for the first time there was no looking backwards for me.

 

Having been through this process on my 2.2 setup, I can attest it makes a world of difference. I used REW to measure, and a Dayton MIC plus a USB mic preamp. I think the total of those two things was $100 roughly. I have cheap subs, like really cheap ($150/each, roughly). I'm fortunate to have mains that produce appreciable output at 35 Hz so the subs really don't have to do much. So, getting a sub that can fill in from 20-40 Hz is a rather easy task. I've never wanted for better bass detail and I prefer a "warm" sound, my system sounds anemic to me without them. Once you've done this process you can tailor it by ear fairly well. But, a remote sub level control is preferred if you are a fan of recordings lacking in bass.

Where the RTA section gets really interesting is in the midbass. If you can dial the 50-250 Hz region relatively flat, you'll find far more detail in your recordings. Adjust to taste, obviously.

If I can mention some recordings for testing bass response:

Pop Evil - Torn to Pieces. Somehow, this metalcore/pop metal track has a fantastic bass kick drum recording. It should be very tight, no bloat, no excess warmth. Just punch you in the chest when it's right.
Jack Johnson - Middle Man. This features an upright bass coupled with a fairly bassy vocal. If you can dial things in to where the vocals don't smear/mesh with the bass, you're good on most recordings IME.
Rob Wasserman/Jennifer Warnes - Ballad of the Runaway Horse. One vocalist, one upright bass. You should sense the bass in the room, behind Jennifer. It shouldn't buzz or sound flabby. Excellent recording IMO.

 

Best subwoofer advice I ever heard came from a Stereophile writer: Turn the subwoofer slowly up until you can just hear it and then turn it down one notch.

 

Nice post. I'm a big believer in room measurements.

I know audiophiles often are big on doing everything by ear. But a carpenter would never hang a cabinet or a door by sight alone, he' just for level with a tool. A tailor wouldn't hem pants by sight and touch, he'd measure the length with a tool.

An audiophile adjusting their subs and room treatments exclusively by ear is just guessing and hoping for the best and is unlikely to achieve that; I don't understand why many audiophiles have become so resistant to the most basic of measurements and the most basic of specs these days.

Personally I've never used real-time analysis software because, as an old timer, I've always just done things the old fashioned way -- with an SPL meter, sweep tones and test tones, and paper and a pencil. I'm sure RTA is better. I'm gonna shoot my room with it this year. It's become so inexpensive and easy, why not?

 

@chervokas the one difference between audiophiles and tailors/carpenters is that our world is a bit more subjective than theirs. If I were mastering or producing the music I imagine I would want as flat and neutral a response as possible. But with audio, and I'm certainly guilty of this, I like a little bump in the bass, especially the 45 Hz-ish area. Nothing obscene, just a dB or two because I prefer that sound. But that's something I have to get by ear and feel, I honestly wouldn't know what that would look like on an RTA. Beyond that? I agree wholeheartedly and would advise to measure first and then adjust to taste in very small increments.

 

If you like it, you like it. Some people might like their pants shorter or longer. Cuffs or no cuffs. Some people like their food saltier or less salty. Obviously you know you like boosted bass, not "neutral" "accurate" bass (to used common audiophile terms that are thrown around but are really meaningless as subjective assessments: if you weren't there went the original was recorded, you have no idea from listening back whether what you're hearing is accurate or not; and if you're not measuring the room response against the input signal you have no way of knowing if the playback is neutral either). That's fine. Whatever floats your boat. But a lot of audiophiles are looking, or say they're looking for, neutral, accurate sound and you really don't have much idea if you're getting that by listening to music -- there's too much variability in the music sources. Measure with sweeps and test tones, adjust the room with treatment, adjust the speaker positioning and equalize if that's your thing, then listen to your reference recordings, get used to what those recordings sound like in a really neutral, accurate environment. Then even if you like boosted bass, or scooped mids, or soft highs, or whatever -- you have an objective, accurate baseline against which to compare everything. Otherwise you could be stuck like one poster above, adjusting the subwoofer with every record, because presumably, the sub's not in the best place, the room has substantial standing-wave-based peaks and nulls and the various albums have different levels of bass content. It becomes a mystery and a frustration.

 

Chervokas; do you mean a proper setup will eliminate the need for adjusting the sub ? On mine, I never touch the crossover, and the volume is at the 12 o clock position for most recordings, and the mains reach down to 38 hz and run full range, so if there's excessive bass I just turn off the sub. On ocassion, there are recordings with little bass that need boosting and I just reach for the sub's volume knob till I'm satisfied.

Of course with old, low-budget punk and metal this shortcomings are expected.

 

Yeah, of course, if the sub is set up such that the system delivers flat frequency response with test and sweep tones from say 30 Hz to 20 kHz at the listening position, then, of course there should be no need to adjust the sub with different recordings because you have flat response and when you play back the different recordings you'll have accurate reproduction of the source. If you want to change it because you don't like the way the source sounds, that's up to you, but that's you changing the sound to suit your taste not to more accurately reproduce what's on the recording.

 

I've been eyeing the DSpeaker 8033S to try out w/ my Epik 15" sealed sub to see if it would help.

I've heard vg things about it - and a lot less work.

 

I'm afraid that is the the case, but thanx for the kind response.

 

Very informative post. Thanks...

 

The problem with adjusting by ear with music is that all the sources are different so you don't know from record to record what's the right baseline to use. Also, response in most rooms from 200 Hz down is so dominated by room modes and standing waves that any one person's room is subject to wide variations from one frequency to the next so if you're listening to music that has a lot of content at a frequency where there's a big peak or a big null, well you'll do one adjustment, then you play a record in a different key with musical activity away from those frequencies, everything might sound very different. The right solution is to treat the room to flatten out the peaks and nulls, and then set the sub so that the response is even, and then you don't need to kind of randomly futz with everything all the time.

 

At least you're doing it with complete understanding of what you're doing, and that's OK.

 

It will probably help but it is not as capable a solution as many of those that require more effort.

 

I've not done any sort of scientific, measured setup routine, and mine has neither a continuous phase adjustment nor a 0/180 switch. (I have wondered if there was something I could add in-line to provide that functionality.)

But one thing I am absolutely convinced of is that for the best integration of subs and mains you need two subs, preferably running in stereo as opposed to both receiving the .1 signal.

My preamp (Arcam AVP700) has both XLR and RCA outputs for each channel, so I use the front L & R RCA outs to feed my two subs (turning off the .1 bass management entirely). The full frequency range goes to my mains (Paradigm Ref Studio 60s, full-range speakers with surprisingly less bass than I'd expected), and then I adjust the crossover on the subs to my liking.

 

Those RTA plots are not telling you the whole story. Looks like 1/3 octave resolution to me. That's simply not enough when looking at and adjusting sub 300hz. You need to turn smoothing off or set it for 1/24 octave resolution, or else your going to simply gloss over peaks and nulls that exist there.

 

REW, Room EQ Wizzard works on MAC. It is free and works well. I am just very familiar with trueRTA.

http://www.roomeqwizard.com/