My "adventures" with the Velodyne SMS-1 (experts needed -- help)

[Vaughan Odendaa]

Alright. I finally got my SMS-1. Unpacked it. This thing is gorgeous to look at in my equipment rack. I connected the SMS-1 to my SVS PB10 ISD.

Crossover is 80 hz in my AVR (Yamaha RXV-450). The low pass crossover has been disabled on the SMS-1 and my subwoofer does not have a low pass filter so I'm using the one in my AVR. Speakers are all set to small.
Subwoofer distance is about 5.5 m even though the actual distance is more like 2.7 m.

The subsonic limiter is set to 15 hz with a 6 dB slope. I haven't upgraded the software as of yet. This unit is extremely revealing of small system changes. I found that, for example, changing phase on my subwoofer from 0 to 180 changed the response, for the better ! I had, I think, about a 12-15 dB dip inbetween 50-80 hz. Flipping this around to 180 deg increased these levels by almost 10 dB's !

Talk about an improvement in the crossover region. I haven't messed around with this unit for very long. I've spent about two hours maximum with it. There are still quite a few things that I don't understand. I participate on AVSforums and have posted in the Velodyne help thread. I'll just copy what I said over there to give you an idea of how far I've gotten.

"A few graphs are in order.

First graph is my response, unequalized.

http://uploadimages.com/view.php?type=thumb3&p=2007/0227/11897175886054.jpg

Second graph I took a stab at the EQ (manual).

Keep in mind that I probably haven't used the right levels to actually EQ but I was in a rush so I had to be brief.

http://uploadimages.com/view.php?typ...7175891142.jpg

This third graph I found interesting. As soon as I closed the door behind me (which leads to another small room, this is what I got. The same settings as in graph 2 but with my door closed resulted in :

http://uploadimages.com/view.php?typ...7175909005.jpg

Please keep in mind again, that I don't yet understand how to use the controls like Q and bandwidth. I just moved the sliders but I still can't affect the frequencies that I wanted to. I need to read up more on this."

So there you go.

Since then, I have made a few modifications (the above was posted about 2 days ago or so). My graph is now much flatter and I've used a level of 80 dB's for the tones to play.

I found that after switching between the eq'ed response and preset 6 (uneq'ed response), the tone of the bass was almost completely different when using the pink noise in the AVR to calibrate sub levels. Before I mostly heard a deep rumbling but now I actually hear more bass.

The problem I'm facing is that once I've eq'ed my frequency response, I have to recalibrate a few dB's lower than before but then my uneq'ed response is down by a few dB's. So I can't make an apples to apples comparison. Is there a way for me to calibrate preset 6 (unequalized) to 73-74 dB's and then calibrate preset 5 (eq'ed response) to the same level ?

For test tone levels, I muted the subwoofer and increased master volume on amp until the levels on the right side of the graph reached 80 dB's and matched this with the left side (sub then unmuted to match).

Is that correct ? I will post some new graphs in a few hours time. The graph I have currently is actually even flatter that my first few attempts. A few questions though. Even though my response is far flatter, the needle on my SPL meter still moves to and fro as if there are serious peaks or dips in the response.

I would have thought that the needle would hardly be moving as some people have reported. Alright, enough with the measurements, time to listen to some music and films.

Listening to music, I found that bass notes are now much fuller than before. Before bass was thin sounding in the 50-80 hz region. My results confirm this in the graphs. Movies are a mixed bag at the moment. Perhaps I've done something wrong, I'm not sure. The infrasonic bass range just sounds really, really subdued, as if my subwoofer has actively cut off from 40 hz and below. But the entire bass range from 20 hz and up has actually increased in the graphs compared to what it was unequalized. It's flat I think to within 4-5 dB's which is darn flat in my book.

The only film I've tried so far is The Matrix. I tried the crop field chapter. There is a scene where a machine tentacle moves past you and it has infrasonic 20 hz information in it. Before, at about 0 dB's on AVR (calibrated to 73-74 dB's and 75 dB's for the main speakers), the room pressurized at that sequence.

But now, nothing. Like I said before, I have increased the levels to create an even flatter response. Another scene is when Neo and Morpheus are sparring in the virtual dojo. When Morpheus jumps and breaks through the mat, there is information extending to 15 hz.

Before I could feel the bass on this one. Now, I can't feel anything at all. Is it possible that the subsonic limiter is limiting output from 25 hz and below ? Because quite a few people have reported that there is a steep roll off below 25 hz on this unit (later revisions have greatly improved this I've heard).

But if this is a roll off problem with the SMS-1, why does it show a graph which gives more deep bass than the unequalized graph ? Why would it show something that I can't perceive ? I need help in trying to understand this.

Please discuss. The end result is that for music there has been a great improvement. However using the EQ result, the bass was still pretty boomy. I am disappointed that the deep bass seems low even though I've increased the levels.

Any suggestions would be most welcome.

--Regards,

 

[avaserfi]

I would love to help, but the second and third links to pictures don't work. Maybe I will be able to be more help afterwards although I am still learning how to use my SMS-1 to its full effect as well .

 

[mike c]

we'll try to help when the other two pics work already

but try these out when you go back to EQ'ing:
-raise the receiver volume so that the line above the crossover frequency is about 80-85db (most of it)
-lower the subwoofer volume IF it exceeds the 80-85 line when you do the above.
-before setting the EQ's, try flipping both phase and polarity (this will save you some sliders, and save you from re-EQ'ing)
-before setting the EQ's, you have to understand how the Q works, and how it affects your actual graph.
-try to play with the Q's ... set a CUT of whatever db you want, then flip through the Q from the biggest to the lowest so you can get the hang of it.

 

[Vaughan Odendaa]

Try now.

http://uploadimages.com/view.php?type=thumb3&p=2007/0227/11897175891142.jpg

http://uploadimages.com/view.php?type=thumb3&p=2007/0227/11897175909005.jpg

 

[Vaughan Odendaa]

Alright, been reading through the Outlaw PDF manual. A higher Q affects a wider range of frequencies and a lower Q a more narrow area.

So if I want to target specific frequencies as opposed to frequency bands then a higher Q would be beneficial. I've got phase perfect on the sub which is 180 deg but I haven't messed around with the phase settings on the SMS-1 (or the polarity).

I'm still a bit worried at the deep bass response problem. I should be getting deeper and stronger bass but it seems nonexistant compared to my former setting uneq'ed.

I'll post the graphs soon. Sorry, I've been extremely busy today and I just got home. I am learning a lot using this unit, that's for sure.

--Regards,

 

[Vaughan Odendaa]

Mike,

raise the receiver volume so that the line above the crossover frequency is about 80-85db (most of it)[/n]

Alright, I'll try that.

lower the subwoofer volume IF it exceeds the 80-85 line when you do the above.

Must I lower the volume control on the SMS-1, the sublevel on the AVR or the gain control on my subwoofer ?

before setting the EQ's, try flipping both phase and polarity (this will save you some sliders, and save you from re-EQ'ing)

Thanks, I think I'll try that.

before setting the EQ's, you have to understand how the Q works, and how it affects your actual graph.

Although I understand (I think) how Q works, it still doesn't work when I want it to work. If I have a target frequency in particular that I want to raise, let's say by 4-5 dB's, if I increase Q, no matter how much I raise it, it still seems to affect nearby frequencies.

Mind you, this only affects a very narrow range. But if I have neigherhood frequencies which are perfectly flat, and then I increase a specific problem frequency by a couple dB's, I almost always manage to inadvertantly affect the other frequencies.

Time and patience. Time and patience.

try to play with the Q's ... set a CUT of whatever db you want, then flip through the Q from the biggest to the lowest so you can get the hang of it.

Thanks for the advice ! It's strange that when I position my subwoofer in the corner, of all places, the response gets somewhat flatter. I always imagined that the corner would be the worst possible place to put it due to room modes being extraordinarily strong at the room boundries.

I wonder if anyone would be able to find out why my SPL meter needle still moves a bit given the results of my FR plot. Perhaps my graph isn't flat enough ?

The only other real concern is the deep bass roll off which I assume is the reason why my bass isn't anywhere as good as what it was prior to me using the SMS-1.

Thanks.

--Regards,

 

[mike c]

i don't think the 100hz boost is going to help since you have a subwoofer crossover set at 80hz. so the sub should be producing minimal 100hz material. if your yamaha has a treble and bass control up front (like mine) I'd play with boosting the bass there ... most bass boosts are around 100hz.

IIRC, a lower Q affects a wider range.

 

[mike c]

Must I lower the volume control on the SMS-1, the sublevel on the AVR or the gain control on my subwoofer ?

volume control on the sub or sms-1 should have the same effect.

Thanks for the advice ! It's strange that when I position my subwoofer in the corner, of all places, the response gets somewhat flatter. I always imagined that the corner would be the worst possible place to put it due to room modes being extraordinarily strong at the room boundries.

it's probably a combination of a room null corrected by the room mode

I wonder if anyone would be able to find out why my SPL meter needle still moves a bit given the results of my FR plot. Perhaps my graph isn't flat enough ?

when is your spl meter needle moving?

The only other real concern is the deep bass roll off which I assume is the reason why my bass isn't anywhere as good as what it was prior to me using the SMS-1.

it's probably because of the 20hz rolloff of the sms-1. but since the pb10 is tuned to around 18hz, it shouldn't matter to you.

 

[Vaughan Odendaa]

i don't think the 100hz boost is going to help since you have a subwoofer crossover set at 80hz. so the sub should be producing minimal 100hz material.

That's what I thought. But then if I boost output at 100 hz, the graph level increases at 100 hz. So that is a good thing is it not ?

Or should I turn the levels down on the 100 hz setting all the way ?

when is your spl meter needle moving?

When I use the pink noise in my AVR, the needle is still moving quite a bit. Which is odd because I assumed that if my response became flatter, the needle wouldn't be moving as much because of the much smaller variations in FR.

it's probably because of the 20hz rolloff of the sms-1. but since the pb10 is tuned to around 18hz, it shouldn't matter to you.

There must be a reason why my deep bass seems to have gone way down since I used the SMS-1. 18 hz content matters a lot to me. Although my subwoofer won't be able to put out 120 dB's at 18 hz, what it does put out is very good (IMO) and I don't want to sacrifice that output.

If there is deep bass content from 20 hz and down, wouldn't the output be sacrificed because of the subsonic limiter ? But then what I don't seem to understand is that if there was a significant roll off, why does the graph tell me otherwise ? It's not as if my levels have dropped off the scale. They're there. I even increased the levels more than what it was.

If you look at the SVS demo sheet, take a look at the Morpheus dojo fight scene. Apparently it has output down to 15 hz or so. The scene with Neo in the pod fields has good bass extension down to 20 hz. Admittedly, there is only one scene in that sequence that dips down that low (that I can tell).

But after using the SMS-1, that bass disappears. Are my levels not correct perhaps ? Maybe the increase in level at 100 hz is somehow affecting things ?

I dunno.

--Regards,

 

[avaserfi]

A couple things I noticed. Mike is right about the 100hz boost there is no real need for it if your crossover is set at 80hz. With my SMS-1 I basically ignore everything past my crossover level since, as Mike said, there will be minimal output.

You say you are worried about the very low end bass response. I haven't noticed any rolloff between 20hz-25hz as you mention and I have firmware 2.1. Version 2.1.2 is the firmware that lowers the subsonic limiter to 5hz. Perhaps you should try to upgrade to 2.1.2 and see if that works for you it should lower the subsonic filter enough to get the SPLs you are looking for.

 

[Vaughan Odendaa]

Cool, but isn't Velodyne releasing their latest firmware update at the end of this month ? Apparently they have decided to defeat the subsonic filter altogether for those who need it.

A couple things I noticed. Mike is right about the 100hz boost there is no real need for it if your crossover is set at 80hz.

I think I've maxed out the 100 hz levels. Is that adversely affecting the subwoofer ? What am I doing effectively ? I thought that because there was a big dip at 100 hz (or a null, it might be deep enough to be classified as such) and by increasing the levels, the null (or dips) increased.

Guess I was wrong on that one.

--Regards,

 

[mike c]

That's what I thought. But then if I boost output at 100 hz, the graph level increases at 100 hz. So that is a good thing is it not ?

yes, as long as it's flat in relation to the other frequencies.

Or should I turn the levels down on the 100 hz setting all the way ?

if you mean the sms-1 level at 100hz, you should use it for the other frequencies below 80hz.

When I use the pink noise in my AVR, the needle is still moving quite a bit. Which is odd because I assumed that if my response became flatter, the needle wouldn't be moving as much because of the much smaller variations in FR.

i think this is unrelated to the sms-1 and how flat your response is.

There must be a reason why my deep bass seems to have gone way down since I used the SMS-1. 18 hz content matters a lot to me. Although my subwoofer won't be able to put out 120 dB's at 18 hz, what it does put out is very good (IMO) and I don't want to sacrifice that output.

how did your deep bass have gone way down? have you measured this, or did you just feel this?

If there is deep bass content from 20 hz and down, wouldn't the output be sacrificed because of the subsonic limiter ? But then what I don't seem to understand is that if there was a significant roll off, why does the graph tell me otherwise ? It's not as if my levels have dropped off the scale. They're there. I even increased the levels more than what it was.

like I said, the PB10 with it's 18hz tuning will barely be affected with the 20hz rolloff. in short, you won't even know the difference.

increased the levels? don't increase any frequency below 18hz.

If you look at the SVS demo sheet, take a look at the Morpheus dojo fight scene. Apparently it has output down to 15 hz or so. The scene with Neo in the pod fields has good bass extension down to 20 hz. Admittedly, there is only one scene in that sequence that dips down that low (that I can tell).

But after using the SMS-1, that bass disappears. Are my levels not correct perhaps ?

are you comparing the scene with and without the sms-1 at the SAME location for the subwoofer?

Maybe the increase in level at 100 hz is somehow affecting things ?

if there is an increase, there should be more bass. your graphs show that your 100hz freq. is a dip (which is why you tried to raise the level)



I do believe though that the chest thump people think is "deep bass" is actually around 100hz.

 

[Vaughan Odendaa]

Mike,

Just got some bad news from AVSforum. Apparently the SMS-1 has some pretty high distortion levels on the input stage. And according to the graph (for the roll off) doesn't the roll off start above 20 hz ? Looks to be around 25 hz and that is with the latest firmware update !

http://www.hometheatershack.com/forums/bfd-forum/6346-behringer-fbq2496-velodyne-sms-1-distortion.html

I hope this isn't going to affect things too much.

I think this is unrelated to the sms-1 and how flat your response is.

Do you think perhaps my SPL meter (Radioshack) is to blame ? Because I've heard plenty of people report that once their response was flattened to within a couple dB's, the SPL needle hardly moved.

are you comparing the scene with and without the sms-1 at the SAME location for the subwoofer?

Yes. But I can't even get the levels right for both presets. In fact, my uneq'ed preset (preset 6) gives me deeper perceived bass and the levels are calibrated lower than when I use preset 5 (eq'ed response) which already has increased levels across the board and a massive increase from 50 to 80 hz and the deep bass is just not as powerful.

how did your deep bass have gone way down? have you measured this, or did you just feel this?

The percieved level of deep bass has gone down. Because when I swap presets, the uneq'ed preset literally pressurizes the room more than my eq'ed preset and I have improved the levels to get a flatter response so the deeper bass should be more easily percieved.

Alas, that is not to be for some strange unknown reason.

--Regards,

 

[Vaughan Odendaa]

Concerning the boost at 100 hz, my speakers are going to bear the brunt of the increase, correct ? I have Jamo Concert 803 bookshelf speakers which are fairly large and incorporate a 7" midbass/bass driver and, according to test tones, reach down to the high 40's.

I still have them set to small for headroom purpuses. But if the SMS-1 only affects the sub range then what am I doing maxing out the slider at 100 hz ? If the subwoofer isn't reproducing this then the speakers would, surely ?

Or is it the crossover that is employed ? The subwoofer still reproduces information above the crossover but attenuated ? Is that more or less correct ? Although the graph is much flatter than what it was prior to me increasing the levels at 100 hz, I just need to know that I've done the right thing.

Thanks.

--Regards,

 

[avaserfi]

First off nice choice in speakers as you might be able to tell by my sig I am a Jamo fan .

Secondly, crossovers are not brick walls. Just because it is set at a certain level doesn't mean there is no sound coming from the sub above 80hz. It should just be quieter and eventually disappear faster than without one. It seems as if you have done everything right, but I would still suggest moving the boost off of the 100hz tone as you don't need a flat frequency response in a range you don't want your subwoofer reproducing.

 

[Vaughan Odendaa]

Thanks, I have the Jamo Concert 803's with the Concert C80 center and C80 surrounds (dipoles) san Jamo sub (I have SVS PB10). All of this magnificent gear is run off a Yamaha RXV-450 !

I'm pretty happy.

Thanks for your advice on the 100 hz boost. I thought I was doing the right thing but if I need to use that filter in a range that definitely will give me a more noticable improvement then I'm all for it.

What level's have you chosen to use for your graph ? 80 dB's ? 70 dB's ?

Because I've found that increasing the levels give you more of an idea of peaks and dips (or nulls). First I had the levels at about 75-76 dB's and then 79-80 dB's. The latter gives me even more "resolution" so that I can see more variation in my FR.

Perhaps I should try 85 dB's. If it's going to show even more variation then perhaps I should work with a level high enough so that I can use the filters more effectively.

--Regards,

 

[avaserfi]

My dad just picked up the 809s with the same center and surrounds .

Here is a picture of my response:

My sub runs from about 24hz-80hz according to spec, but in my room goes lower, as you can see the response is fairly flat with one dip around 45 or so hz which is due to room nodes that I cannot overcome because of my limited placement options.

I could really care less what the response looks like beyond 80hz because my mains and such will fix that as well .

I know it isn't ideal yet, but I haven't had a chance to tweak everything the way I would like. Hope this helps.

 

[Vaughan Odendaa]

Congratulations on the purchase ! I'm a Jamo dealer so I thought I might as well get the Concert speakers. Hehe.

Btw, did you upgrade the firmware to it's latest version ? I might have missed that in one of your previous replies. Are you running your system with mains as large ? What is your crossover frequency ?

By the looks of your graph, I'm not entirely sure what level you've used but I'm guessing around 82-83 dB's ?

Thanks.

--Regards,

 

[Vaughan Odendaa]

BTW, about the calibration of two seperate presets, how do I go about doing that ?

--Regards,

 

[avaserfi]

Congratulations on the purchase ! I'm a Jamo dealer so I thought I might as well get the Concert speakers. Hehe.

Btw, did you upgrade the firmware to it's latest version ? I might have missed that in one of your previous replies. Are you running your system with mains as large ? What is your crossover frequency ?

By the looks of your graph, I'm not entirely sure what level you've used but I'm guessing around 82-83 dB's ?

Thanks.

--Regards,

I am using firmware 2.1 which has the subsonic filter at 15hz as far as I know. My Jamo E770s are set to small with my crossovers set at 80hz.

The level is about 83dB. I found setting it to high causes it to hit the ceiling where everything just looks flat.