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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
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.
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.
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.
strateahed OP
299 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.
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.
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