Phase to control bass "position"?

Hey guys,
just setting up a small work space with a little system.
  • I'm using an HK 3490, Polk RT25I speakers on a desktop, and a Sunfire SDS-8 sub.
  • The HK has stereo sub capability, but I'm only using one.
  • My listening position is about 3ft off the wall from that the bookshelf speakers back up to, pretty much centered on the wall.
  • The sub is off to the left about 3-4ft away, in the corner.
  • Some tracks the bass is ready and apparent.
  • Others, I have to check to see whether the sub is working, as the doesn't seem to be much output. This is inconsistent.
Should I be looking to phase adjustment to "position" the bass? This is an unusual listening position for me - I'd usually be further back. Loosely speaking, I'm kind of sitting in the middle of the room more toward the same wall that the speakers an sub are against.

Is there a difference in what the sub crossover will do with an LFE input vs regular old input channel?

The HK 3490 does not offer bass management - it passes full range. I've never used subs with this unit before, usually just larger speakers, like Monitor 10's, and it does fine, so I'm not sure whether it's a limitation of the unit, or a tuning issue with the sub.
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  • heiney9heiney9 Posts: 24,148
    Are you sure the songs with lesser bass output aren't just bass shy songs? I've been tricked a few times with my rig, thinking where'd the bass go only to realize the songs I was listening to were bass shy.

    Just a thought

    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass

    Pass Aleph 30 | EE Avant Pre | EE Mini Max Plus DAC | MIT Shotgun S3 | MIT Z P/C's | updated SDA 1C| SQ Box Touch/Welbourne Labs P/S- Tubes add soul!
  • mikeyb128mikeyb128 Posts: 2,887
    I had a heck of a time dialing in my sb1000 which sits about 2-3 feet behind my towers and in a corner. It uses full range RCA's from my pre amp and I have it crossed over at about 60hz.

    I was very surprised that even just a few clicks on the phase knob would have no bass output for certain frequencies. I would say you have some set up issues. Since you use small bookies I would cross it over at 80hz and play with the phase settings more.

    I also have been doing a lot of reading on the use of stereo subs. Running the left and right (stereo) RCA's to a mono subwoofer can result in some frequencies being lost, hence why you might not be hearing some bass frequencies. It's like trying to run a stereo signal to one speaker, it can only play so much.
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  • msgmsg Posts: 6,147
    Hey guys, thanks for the thoughts and ideas.
    I think it's most likely a combination of the things you mention.
    I really just threw this system together in less than a day. I have to remind myself that I can't expect it to be perfect right away. And then cables - with the exception of Doug's on the Speaker cable front, the sub and IC from the piCorePlayer are super cheap.

    So, yes, definitely seems to be track related, and for some reason more profound a difference in this space. Some of it hits nicely, and is tight and punchy, and then on some other tracks, it's like it's skittish - comes in slightly and out again, no sustain. While I'm saying track related, I have to also say service quality related. Spotify was better than Pandora.

    Then other reference tracks sound like the bass timing is off. Does this sound like phase?

    And then the other really weird thing - I feel like I'm imagining this - I swear it sounds better after running for 3hrs. I turned the system on when I got home, hung out for a while obsessing and experimenting, and then had to get on to other stuff. And now I'm sitting in here and it's sounding pretty nice. wth? Could also be the Weihenstephaner Kristall Weiss...

    Mike thanks for sharing that info on your experience there. I've really never really seen much on phase before. It doesn't seem to be something that people talk about very often, and haven't read on it myself, either. I always just thought it was just 0° or 180° for the most part, and mostly just for correcting reversed polarity between speakers and sub, but this sub I got from Rick has notched sweep from 0° to 180°.

    I think I need to get an SPL meter and mess around. Recommendations? Everyone always said the Radio Shack one.

    I'm thinking that the sub may do better in the corner to my rear left, further away, which would put my listening position more at the "back" wall from the sub. Still kind of a wreck in here, so the sub crawl isn't really possible right now.

    I was feeling pretty deflated at the lack of filling performance for at least half the stuff I've been listening to, and was considering just scrapping the system altogether and just going back to the Bose Companion 2.1 that I was running straight off the computer, before. That setup sounds okay, and the bass is much more pronounced, but it's also a bit sloppy, AND... I don't think I can give up what the RT25I's are bringing to the table for the rest of the sound range. This is the system I was pulling together when I was looking for some small bookshelf speakers that you guys helped out with, and bass issue aside, I'm really loving these little speakers, so, fantastic recommendation there.

    I'm going to swing another piece of gear in to see whether it pulls in the bottom end. The HK 3490 sounds very pleasing to me in 2ch with RTA-11T's, no sub, but I was reading on AVS earlier that some owners found the 3490 bright and lacking in the bass department, so, could be something about the sub performance. Apparently there's nothing special, just mono preouts. I don't know, maybe it's got low signal. Can I test this with a multimeter?

    @nbrowser - you're running full range speakers with your HK, right? Do you have any experience using a sub with the 3490? I think you're the only other dude I know with one of these.
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  • rpf65rpf65 Posts: 2,131
    I think you may want to try repositioning your sub. Take one of your bass lite tracks, play it, and reposition your sub. Move it about a foot or so, and if the song gains or even looses bass, it's more likely a null/void issue than phase related.

    With phase, you're trying to get the sound waves to blend together more cogerently, that's why it is sometimes referred to as delay. Doesn't sound like a delay issue to me. Sounds more like a freq range is being degraded.

    As far as spl meters, there are a couple of pretty decent free apps that will give you a fairly good base line.
  • msgmsg Posts: 6,147
    edited July 2016
    Hey guys,
    I swapped out the HK3490 for a B&K AVR 507. It seems to be lacking a touch in the 2ch realm, but with bass management, it's addressed the bottom end nicely. I'm not sure what the deal is with the 3490, but it didn't seem to work very well with the sub I'm using, but did seem to pair slightly more nicely with the RT25I speakers wrt 2ch use.

    I set up the 507 pretty quickly
    • Set Stereo/2 configuration with the piCorePlayer/HiFiBerry DAC+
    • Set the RT25I's to small, sub on, and crossover at 80Hz.
    • Speaker distance 3ft., Subwoofer distance 5ft
    • 0° phase, crossover to bypass, and subwoofer physical volume at 0, which is 12 o'clock on this SDS-8 unit.
    Got bass now.
    With the B&K remote, I can set the levels on the fly.
    Speakers zero'd, and sub bumped to +3 on scale of 12.

    Still needs tuning, but this is working much better now. I still plan to experiment with an analyzer and sub phase as recommended, but this at least won't irk me like it was. Don't know nuthin' from nuthin' about that stuff right now.

    I swear the 3490 did very nicely with the RTA-11T's I was experimenting with - pleasing 2ch stereo performance with those speakers. Not really anything in the way of adjustments to troubleshoot the subwoofer integration, though, so I was at a loss there; not really an option to run full size speakers in here. Almost seems like subs were just an afterthought on that unit.

    Thanks for the info and recommendations. I'll keep them in mind as I make adjustments.
    Post edited by msg on
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  • Me, i just displayed 1 furniture on each corner .... The sub sounded horrible (50-70hz peak) after i just twisted my furniture at exactly 45degre on the corner and i had wonderful sub-frequency under 30Hz (all the 50-70hz was tamed).. Happy!
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