How do you improve bass response in a null?

hi ken,

as each of these subs has different amplification & crossover electronics, i'm not sure what the best solution would be, for you to run a stereo pair. i suggest you try to match up the two subs that have the most similar cross-over point/slope to do this. but, i honestly think it would be dumb luck, if it worked. it might be easier if you ran the monitors full-range...

of course, i am referring to audio - i have no suggestions at all as to home-theatre, altho i know the accuracy & distortion-free output isn't as critical.

if you're really serious about top-notch 2-channel audio & want subs, i strongly recommend a *matching* pair of subs, at the very least. of course, my preference is well-known to those who frequent these forums - i prefer passive subs, an active outboard electronic x-over, & separate amplification. i believe you then maximize the quality of the electronics at the least cost, and it also is really the most flexible, tho it may not seem so at 1st.

i'm a cheapskate, primarily shopping used, cuz my taste exceeds my budget! ;~) but, in the case of my subwoofer set-up, i bought mostly new. why? because it was far & away the best performance for the money, & what i got rarely shows up on the used market. i bought the subs & x-over brand-new, using an old adcom gfa555 amp i already had, & buying a second adcom amp, just for overkill, & cuz i could afford it! :>) i got my fully-optioned vmps larger subs, marchand xm-9 x-over w/upgraded op-amps, the two adcoms, & the cabling for a bit under $2400. this is *serious* bass for audio; i can only imagine what it would do in a h-t set-up... ;~) and, w/the marchand x-over, it is amazingly flexible - i've successfully had speakers as diverse as thiel 3.5's, & proac response 1sc's seamlessly intergrate into my ~25x38 listening room. i wouldn't trade my set-up for a pair of rel's top-line offerings. i might be interested in auditioning a pair of bag end d18's - their models w/the 18" drivers each, along w/their $2600 elf x-over - if i won the lottery! :>)

go to vmps' www & check the distortion & output specs of their subs - truly world-class; nothing else even close at anywhere near the price; only a couple approach 'em, at *any* price.

doug s., yust a satisfied customer...

Doug,

I've just ordered a REL Storm III. In addition to it I'll have a Velodyne HGS-18 & M&K MX125 with dual 12" drivers. What would be your suggestion for using either of these 2 subs as the 2nd stereo sub in addition to the REL?

The Velo can be connected via high or low inputs, while the M&K is limited to low level only. Or should I just connect all 3 and run them in concert?

Thanks,

Ken

run a pair of subs in stereo. easier to get a more natural low-frequency soundstage, & easier to set up to avoid room nodes, imo. added benefit is much cleaner sound, due to much less distortion for the same spl. especially important if you're not using subs w/such low-distortion/hi-output ratings as vmps... ;~)

doug s.

Dave 1,

Very creative solution. Unfortunately my sub's phase is already set for maximum spl. If I reverse phase, it will make the null even worse. If my sub were set out of phase, then your solution would be a good one.

Thanks for your advice though.

Ken

I had a problem not so much with a null, but rather a peak at 40 Hz. Though I had a bit of a null at 80 Hz, the response of the sub in the room was almost +10db higher at 40 Hz. Moving the sub around did help a little, but didn't come close to eliminating it.

After months of heavy lifting the sub to various points in the room and annoying my family and dog to no end with test tones and sweeps, I decided to try and play with the phase of the sub to see if it made any difference. The usual way to set the phase is to adjust it (usually a switch or knob on the sub) so that you get the loudest response at the listening position, which is what I always did. So just for grins, I decided to flip the phase switch on my sub from the 0 degree position to the 180 degree position. I could instantly hear the 40 Hz peak was either gone or significantly reduced. So I re-ran my test tones and calibrated things again with the phase set to 180.

Sure enough, after measuring it with my Radio Shack meter, the 40 Hz peak was reduced to a 1 db peak. No more boom-boom headaches or seemingly one-note bass. Music and HT sound signficantly better.

Not sure if it will work with your null problem but you may want to try it. My system includes Dunlavy Aletha's and a Velodyne FSR-15 sub. Try it and let us know if it works for you.

Both brand and location make a difference for quality and spl. I don't think integration per se has anything to do with SPL (if we're talking about the same definition of integration), but there might be something I'm not thinking of. A Rel sub might not produce a null zone from the same location because they're down-firing (if the M&K is a front-firing sub). Getting a similar sub with more power may not do the trick, if the null zone is caused by by the room structure. The Rels, btw, don't come with the most powerful amps out there. I'd definitely experiment with moving the sub around a little. That's the easiest and cheapest solution.

Dbwl,

I read a past post of yours where you heartily endorse REL subs. You've given me food for thought. I'm thinking that the REL might augment the bass better than my current M&K sub. Do you think it's more a matter of location or brand of sub? The M&K has plenty of raw output, but may not integrate as well. Does integration have any bearing on spl level?

Sean,

As you suggest, I've thought about moving the sofa farther back, but then realize that the TV picture would become smaller. However, this might be an acceptable trade-off. It's easy enough to try. I'll let you know the results.

Sdcampbell,

The sub is currently located on right front wall about 3-4 feet from the side wall. Corner location would interfere with a closet door on side wall. I've heard that while corner placement provides more bass reinforcement, it also can add to boominess and standing waves. But as you suggest, maybe I just need to move it a few inches.

In the past I've moved my seating position a few inches, and it never has made a significant difference. Is this the same as moving the sub's location?

Thanks to all for your input.

You didn't state where the sub is currently located. The optimal position for best bass loading is normally in a corner of the room, where there are three adjoining surfaces. Sometimes moving the subwoofer only a few inches will make a significant improvement.

How about moving the couch a tad further back. You don't have to muck with speaker placement much and this would change your listening point of perception. Sean
>

I imagine experimenting with sub placement would help. Also, you could move the mains either forwards or backwards a foot or two without changing the fact that you and the tv are centered between them. That might work. Less likely to work, but still a possibility, is to move the speakers slightly farther apart. I'm guessing you've found the right spot for the mains though, so I'd try the sub first.