Wow!! Velodyne SMS-1 subwoofer correction system

[audioguy3107]

This is one of the best purchases I've ever made. Here's a little background:

If you don't know about this product, this was the standalone processor that Velodyne began to market after their success in implementing it in all of their Digital Drive subwoofers. When I first set up the audio room, I had a Velodyne DD-10 instead of the pair of REL B2s that I have now. Before the Velodyne, the bass is my room just didn't work regardless of room placement or treatments. My bass response graphed out looked like something out of a trigonometry textbook with a fairly large peak between 30 and 37 Hz and an ENORMOUS valley at 40 Hz which pretty much sucked the bass right out of the music. We then peaked again a little above 50 Hz which made the lower midbass sound really boomy and downright annoying. The Velodyne did help somewhat, but as I have mentioned before in other threads, I had a visit from Jim Smith (Get Better Sound fame) who "voiced" my room, set everything up and insisted that 2 RELs in stereo would be better than the one Velodyne. The problem with this was losing the DD correction software. I followed his instruction anyway and sure the RELs bass was deeper, smoother, and more musical, but no matter where I put the damn things, I still had the peaks and valleys in my response. The problem now was that to take advantage of the REL "bass pressurization" and other advantages of REL subwoofers, I had to turn the volume up too high. Even with the RELs ABC crossover set to the lowest setting, when I would turn up the volume, I would begin to get an even louder midbass hump (since you really cannot fine tune the RELs with slope etc.) and still no help with the 40 Hz valley.

A couple of weeks ago I said forget it and started looking for one of these SMS-1 processors...I figure it's not too expensive, somewhat rare, and I could resell it if it didn't work well with the RELs.


So I got it a couple of days ago hooked it up and began dialing it in. Using no equalization, I moved the RELs around until I got the best response watching the graph (in real time) on a monitor. Once that was finished, I performed the auto eq which gets you about 80% of the way home. After that was complete, you can use the software to adjust each frequency, the Q value, and the crossover/slope. To make a long story short, after I was done, the microphone showed now an almost ruler flat response from about 15 Hz to 65 Hz. Sweet. Another thing I was able to do was adjust the crossover slope and make it somewhat steep so that I didn't have too much overlap with the Avalon's. the on screen graph makes it easy since I was able to disconnect the Avalon's to get a graph of the RELs by themselves. Next it was music time.

Holy Crap. I have never heard such deep, smooth bass in my life and I've listened to some pretty outstanding systems. Stereo RELs combined with ruler flat response down to 15 Hz is something to hear. You can actually feel the REL pressurization that you read about without anything muddying up the lower mids. The soundstage now goes wall to wall, since I'm actually getting response between 40 and 50 Hz which was absent before.

Listen, I'm not an equalizer guy, I hate tone controls and I'm sure the engineers at REL would cringe knowing that I had to use a Velodyne processor to help, but let me tell you something, if the room you have negates the advantages of high quality subwoofers, then give it a shot. If there is any time smearing or anything detrimental to the sound by using this, I cannot hear it and even if I could, the advantages far would outweigh the negatives. This is by far the most cost effective upgrade I've ever purchased and it cost me less than $400......I believe it retailed for $799.99 when new.

If anyone out there cannot tame bass response in their room, I urge you to comb ebay or audiogon and give it a try. Amazing!

[chessman]

I have a SMS-1, which worked real magic in my home theater until I upgraded to stereo subs with a Bryston 10B-sub. Even then I used the SMS-1 as a diagnostic tool (real time sweeps and visual display). I used the Bryston to set cross-over and slopes, the ARO on the JLs, but measured the results with the SMS. Then I took the SMS out of the signal path. For the typical user, there is no more simple and effective tool than the SMS.

[audioguy3107]

How was/is your response before the SMS-1? Were you using it to get your placement correct? My bass response was pretty much awful......I have to keep it in the chain....I spent at least 2 days moving subs around to try and smooth out without it, but to no avail. The results are just stunning.

[chessman]

Originally Posted by audioguy3107

How was/is your response before the SMS-1? Were you using it to get your placement correct? My bass response was pretty much awful......I have to keep it in the chain....I spent at least 2 days moving subs around to try and smooth out without it, but to no avail. The results are just stunning.

A complete answer would take longer than I can do on this phone. I have attached a thread link that lays out much of it. I found that accurate volume matching and accurate relative phase adjustment in my acoustically treated room made EQ other than ARO unnecessary. I think the ARO was dealing with decay time more than frequency response.

http://www.audioaficionado.org/subwo...s-project.html

[audioguy3107]

Cool explanation, you were really fortunate to get that kind of frequency response without having to use the SMS-1 eq feature. I wish my room came even close to that, but hey it is what it is. I am really surprised that with all the different sub placement I couldn't do any better, but I guess it's the room dimensions and volume that are getting me.

[chessman]

Originally Posted by audioguy3107

Cool explanation, you were really fortunate to get that kind of frequency response without having to use the SMS-1 eq feature. I wish my room came even close to that, but hey it is what it is. I am really surprised that with all the different sub placement I couldn't do any better, but I guess it's the room dimensions and volume that are getting me.

Where are your subs in relation to your mains? The closer to the mains, the less relative phase adjustment (and ability to err) is needed.

Is your seating 2/3 back from the front wall? Middle of the room is often a dead zone. Against a wall gives boundary effect (thud).

What does your frequency response look like at the cross-over point? A "W" pattern indicates an interference pattern that may be a cross-over setting that is too high or a slope setting that is too gradual.

Happy tweaking!

[audioguy3107]

Originally Posted by chessman

Where are your subs in relation to your mains? The closer to the mains, the less relative phase adjustment (and ability to err) is needed.

Is your seating 2/3 back from the front wall? Middle of the room is often a dead zone. Against a wall gives boundary effect (thud).

What does your frequency response look like at the cross-over point? A "W" pattern indicates an interference pattern that may be a cross-over setting that is too high or a slope setting that is too gradual.

Happy tweaking!

I've got both subs right next to each main speaker and maybe about 8 inches back (I have a wool carpet so I try to keep them off the carpet or else they would be half on half off). My seating is approx. 2/3 from the back wall any you're right, the middle of the room is a dead zone, but Jim Smith and I found the best place for the couch that would still work as seating of course. I have the crossover set really low and a pretty steep slope so I don't think I'm getting any interference at the crossover point. Anyway, it sounds so much better than before I can't belive what I was missing!

[chessman]

Umm, if THE Jim Smith was actually in your room setting things up, then I am shutting up right now!

[audioguy3107]

Originally Posted by chessman

Umm, if THE Jim Smith was actually in your room setting things up, then I am shutting up right now!

Yes, it was him indeed......I'm a pharmacist at a local pharmacy here north of Atlanta. I got to talking to a patient of ours about audio/video and he mentioned that one of their friends was a big audio guy who gives speeches, writes books etc. When I asked who it was, it turned out he is friends with him and little did I know that Jim lives about 20 minutes from me. He put me in touch with him and we got together over at Jim's house first to check out his system and talk about mine. He evaluated mine and then did his thing over at the house. Pretty awesome.......he was very precise and professional...it was fun just talking about all his experiences in the audio world as well.

[chessman]

Originally Posted by audioguy3107

Yes, it was him indeed......I'm a pharmacist at a local pharmacy here north of Atlanta. I got to talking to a patient of ours about audio/video and he mentioned that one of their friends was a big audio guy who gives speeches, writes books etc. When I asked who it was, it turned out he is friends with him and little did I know that Jim lives about 20 minutes from me. He put me in touch with him and we got together over at Jim's house first to check out his system and talk about mine. He evaluated mine and then did his thing over at the house. Pretty awesome.......he was very precise and professional...it was fun just talking about all his experiences in the audio world as well.

I am sooo jealous! And that is too cool.