2. speakers
  3. 1331602830

Sub Integration Question / Recommendation

In the process of changing out some cables and upgrading my system, I now need to get Hsu subwoofer dialed in again. The prospect of going through this exercise was enough of a disincentive to making these types of changes before now.

According to previous forum posts, my chosen approach is termed "Bass Augmentation" as opposed to "Bass Replacement". However, the term "augmentation" may be somewhat of a misnomer; that is, my goal is to have the subwoofer "blended" seamlessly with speakers running at full range in a 2-channel application. There was some discussion of “level matching”, but no step-by-step description on how to do it.

Rather than taking measurements (with RS analog SPL meter) above and below manufacturer’s recommended level of 50Hz, I took another route. My speakers go down to 35Hz, and I got a suggested cross-over of 40Hz. So this is the setting used on the sub, with the cross-over switch set to “In”, and Volume at 9:00 o’clock.

Here are the steps I took: 1) Set the main system volume to near the maximum that I generally listen; 2) using Stereophile test CD at 40Hz tone, took SPL reading of main speakers from listening position, without subwoofer (sub turned off); 3) with main speakers turned “off” and again using test CD at 40Hz, adjusted sub volume to match same level of mains measured in Step #2 … in this case 67 db.

When both the mains and the sub were all turned on, something unexpected happened: the SPL level dropped down to just below 64 db. I had expected it to be the same or higher. What’s going on there? Now “theoretically”, is this the correct method to perform “level matching”, or should the sub volume (with mains “on”) be adjusted upwards to reach the same level reached in Steps #2 and #3 … which was 67 db?

I mentioned “theoretically” because - in the long run - I will play around with the settings to fine tune the sound by ear, in order to get it to my liking. That’s what happened last time out, and it’s also the way I got my second system dialed in.

That said, I would still like to know: what is the accepted and correct way to perform “level matching” between main speakers and sub woofer? One would think this should form the basis of the most objective starting reference point. What’s your take and/or recommendation?
strateahed
9 responses Add your response
xti16
1,525 posts
 
I have tried several locations and for me I have my B3 about 6ft to the right of my right speaker (about 9ft from the sweet spot and about 3ft from the right corner). Funny the location I disliked the most (but thought it would be the best position) was between the 2 speakers.

That being said I have a goofy room and wanted to get equal bass throughout the room. Without a ton of treatments I found that won't happen. The position it is in now is the best compromise for me.
rockyboy
335 posts
 
Xti16

Need to ask - where did your REL finally end up in the room? And did the placement make a significant difference? I've not played with my REL which I set initially in the corner and it's stayed there; so, I'm curious. When I get my amp back from repair I will have to experiment with placement.
xti16
1,525 posts
 
Again take your time and play music with super low notes and pay attention to whether or not the subs leading or lagging the sound from the speaker (move the sub accordingly). After that then work on crossover point and volume/loudness.

After all in the end you want the sub to pick up where the speakers leave off and not add to what you already have. In my opinion I would cross the sub over at 30hz and maybe if needed to go up from there. You should not be able to tell where the sub is located.
strateahed OP
303 posts
 
Thanks everyone for your input and ideas. I really appreciate it. Looks like there are definitely a few more things I can try in order to get this thing right. In the meantime, like Xti16, I've experimented with moving the sub ever so slightly. This results in changes to the quality of the bass.
martykl
3,578 posts
 
If I've read your post correctly, you probably got destructive interference at the measured frequency:

Bass is omnidirectional, and reflections off nearby walls will (depending on phase relationships) either reinforce or cancel subsequent output from the bass driver at the same frequency. You were probably measuring at a frequency where out of phase reflections caused a null in response. Google "Quarter wave cancellation" for a good explanation of this phenomenon.

From my own set-up/measurement experience, I'd note the following:

This effect will be audible below app 200ish hz, and will dominate the in-room response below +/- 125hz in most untreated rooms. If you use Hemholtz devices (bass busters) you might get some relief from this until you get down to +/- 75hz, where these start to fail.

The best way to level match a sub is with a real time analyzer (RTA) and/or EQ. I use Audyssey which combines RTA, crossover, and EQ in the digital domain. It is automatic and (for the recent XT32, at least) tremendously effective.

Velodyne makes a stand-alone version called the SMS-1 that also works pretty well. However, its automatic mode is useless and the much better manual mode requires a fair bit of time and effort to get right. If you use it strictly for set-up, it will help you place your subs for smoothest FR and you can remove the device from the chain after you've optimized placement. Alternatively, you can leave it in the signal path and EQ the subs if you wish.

Re: "replacement" vs "augmentation", well....

If you run your mains full-range and cross at 40hz (augmentation) without any room EQ, you're still going to face the issue of room effects. Even if you use the SMS-1 to move the sub(s) around until you find the best position for minimizing these effects (per the above), you'll probably be left with pretty significant room induced irregularities, particularly above the x-over point. If you cross the subs higher, you can use optimized placement to extend the benefits of smoothed FR up to the new, higher x-over point.

Good Luck.

Marty
onemug
784 posts
 
Possibly the sub is out of phase with the main speakers causing some cancelation. Try reversing the L and R of both mains (or does the sub have a way to reverse phase?) and see what your reading is.
xti16
1,525 posts
 
When both the mains and the sub were all turned on, something unexpected happened: the SPL level dropped down to just below 64 db. I had expected it to be the same or higher. What’s going on there? Now “theoretically”, is this the correct method to perform “level matching”, or should the sub volume (with mains “on”) be adjusted upwards to reach the same level reached in Steps #2 and #3 … which was 67 db?

I mentioned “theoretically” because - in the long run - I will play around with the settings to fine tune the sound by ear, in order to get it to my liking. That’s what happened last time out, and it’s also the way I got my second system dialed in.
Sounds to me as if the timing/phasing is way off (like 180 degrees off) so the speaker and sub are fighting each other. When I got my sub I had a similar problem but I don't have a SPL meter. I tried using a test cd with different tones and it threw me way off. So I just listened to music with very deep low notes and over time I realized that the sub notes were either leading or lagging the speakers. My Rel has a phase switch that is 0 or 180 degrees. What I ended up doing is physically moving the sub either closer or farther ( by a couple of inches at a time) to get it to blend.

That being said my speakers are rated to 45hz and I cross the sub over at 41hz and turn the volume up a hair.
hifitime
715 posts
 
When both the mains and the sub were all turned on, something unexpected happened: the SPL level dropped down to just below 64 db. I had expected it to be the same or higher. What’s going on there?

A lot of people set sub levels different than others. So I don't want to get into a proper, or not proper way of doing it.

The statement about the volume drop when everything is on leaves me thinking your sub is out of phase with your other speakers. Try reversing its phase, and check for an increase in level.
magfan
1,583 posts
 
with touching nothing, swap phase on both main speakers. (+-)
Sounds like they are out of phase with the sub..in the crossover region.

I too, have a HSU sub. A VTFII mk III.

If I cared enough to do a level match, I'd start at 1khz at zero. try to get maybe 75 or 80db net.
Than, go below and above the crossover. try to draw some kind of curve to maybe -12 db or more.
THAN turn the sub on and try again.

As for which disk to use? Well the Rives disk I have is level corrected for the RS meter.
Log in to respond
More to discover
80x80
Infinity Intermezzo 4.1t
80x80
Martin Logan Classic ESL 9A
80x80
Focal Kanta 3