My VTF3-MK3 installation

[Liaury]

Hi folks,

I'm having a real adventure installing my 3.3. I have Rocket RS850 mains, center, and surround. HK AVR335 serving as my pre/pro. I also have a Onix RDES that I'll include later. Speakers are set to small and crossed over at 80 Hz. Sub is placed directly behind me set at 4ft away on the processor. Also have GIK 244 in the two front corners of my room. If you like to see pictures and dimensions of my room (although a bit outdated), my gallery in on the AV123 site. http://www.av123forum.com/photopost/showgallery.php?thumb=1&cat=500&si=liaury&perpage=12&sort=1&stype=&ppuser=

Below are two graphs with the two phase settings. I feel I'm getting really bad response. Anyone have any recommendations or explanation of what I am seeing. I'll have more information later as I try to apply the RDES to the system.

[SeattleDucks]

Hi folks,

I'm have a real adventure installing my 3.3. I have Rocket RS850 mains, center, and surround. HK AVR335 serving as my pre/pro. I also have a Onix RDES that I'll include later. Speakers are set to small and crossed over at 80 Hz. Sub is placed directly behind me set at 4ft away on the processor. Also have GIK 244 in the two front corners of my room. If you like to see pictures and dimensions of my room (although a bit outdated), my gallery in on the AV123 site. http://www.av123forum.com/photopost/showgallery.php?thumb=1&cat=500&si=liaury&perpage=12&sort=1&stype=&ppuser=

Below are two graphs with the two phase settings. I feel I'm getting really bad response. Anyone have any recommendations or explanation of what I am seeing. I'll have more information later as I try to apply the RDES to the system.

Liaury, based on my own in-room measurements using first an Athena AS-P400, then an SVS PB12-NSD, and now a VTF-3 MK3 and from looking at many graphs of other sub owners (of a variety of different brands), what you are getting is not uncommon because most rooms play havoc with bass frequencies. Through lots of careful trial & error with various placement options of the sub (and even moving the listening position at times) you should be able to find a sweet spot that may get you to a variation of about +/-6db, and to improve on that further it is highly recommended to add bass traps/room treatments next, and then if still needed add a good bass equalizer such as the Behringer Feedback Destroyer or Velodyne SMS-1.

[Liaury]

I'll add that I've tried three different positions behind my couch, also rear left corner of the room and front left corner of the room. The two right corners have a door so I didn't go there.

I'm wondering if my shallow room and/or large side openings is causing havoc to the sub response?

[SeattleDucks]

I'll add that I've tried three different positions behind my couch, also rear left corner of the room and front left corner of the room. The two right corners have a door so I didn't go there.

I'm wondering if my shallow room and/or large side openings is causing havoc to the sub response?

Getting the smoothest in-room response sure can be a lot of work. With my 3mk3 I have tried close to 15 positions (and often variations of those by moving the sub just a few inches) and measured them all with both phase settings, and after many hours of this it gets weary. The exact location of the prime listening seat also is critical, as I found moving just a foot or two in either direction changed the readings by as much as 10db in some cases. I finally put the SPL meter away and quit measuring because I was driving myself crazy and have now found a left front corner position that is sounding really great to my ears. I won't start doing critical measurements again until I get some room treatments, as they make a huge difference in smoothing out most of the peaks and dips such as on your graphs.

Maybe cyberbri can chime in here - he has good experience using bass traps for improved room response.

[Liaury]

Getting the smoothest in-room response sure can be a lot of work. With my 3mk3 I have tried close to 15 positions (and often variations of those by moving the sub just a few inches) and measured them all with both phase settings, and after many hours of this it gets weary. The exact location of the prime listening seat also is critical, as I found moving just a foot or two in either direction changed the readings by as much as 10db in some cases. I finally put the SPL meter away and quit measuring because I was driving myself crazy and have now found a left front corner position that is sounding really great to my ears. I won't start doing critical measurements again until I get some room treatments, as they make a huge difference in smoothing out most of the peaks and dips such as on your graphs.

Maybe cyberbri can chime in here - he has good experience using bass traps for improved room response.If I can get +/-5dB, I will be very happy. I'm at +/- 12dB right now.

I did measure both phase settings and physically turn the sub 180 degrees at every position. Turning the sub actually didn't make much difference in my room positions. This is nerve wrecking for sure. I used to have a Rocket UFW-10 which is about 25% the size (and about 1/2 the weight) of the 3.3 (soooo much easier to move around).

[cyberbri]

See my thread here:
http://forum.hsuresearch.com/showthread.php?t=2533

I started experimenting with REW a few weeks ago (did some more tinkering last night, and re-did all my BFD filters too). The graphs are from REW, and are at a very fine resolution, probably 1Hz or better. Sweeps take about 10seconds.

Graphs can look MUCH different if you change the dimensions of the graph. I stretched out the graph and attached it.

But your 180-deg graph doesn't look too bad, and the results aren't surprising considering the sub's behind you. With an eq you could bring the peak at 47~48Hz down and smooth the rest out a bit. If the dips at 60Hz and 67Hz are just variations and not true nulls, those could be smoothed out as well. The dips at 80Hz and 95Hz are normal, not too bad. Additional bass traps could help.

The 0-deg phase one isn't too bad either, at least up to 100Hz (need to see how it looks up to 200Hz or a bit higher to tell what it's doing to the bass in the 100s). That could easily be tamed with an eq.

With no eq, I'd choose the 180-deg phase because it doesn't have the HUGE dip between 55-65Hz or the huge peak from 65-80Hz. If the big peak at 47Hz was tamed with the 180-deg response, even just that would make a huge improvement and give you a nice curve, with a heavy <30Hz area.

You're definitely a good candidate for an eq. With either of those graphs, you could cut frequencies going to the sub and aim for a 70dB baseline, with flat response (or varying degree of house curve), then adjust the level of the sub to calibrate it correctly with the speakers.

If you get an eq, you can try experimenting with sub placement to work on the big dip/s, and then just eq the rest of the peaks down.

What helps is to run graphs for the speakers only, sub only, then combined with phase at 0/180 - so you can see how they are interacting. And run the graphs up to 200~400hz or so, to get the whole sub/speaker interaction picture.



Also, have you tried the sub in the front left corner? The response MAY be better there, if you can move the equipment around. That would be my first place to start.

Plus, bass traps in the front left, front right, rear left, and possibly but not necessarily rear right corner. The more the better.

[SeattleDucks]

See my thread here:
http://forum.hsuresearch.com/showthread.php?t=2533

I started experimenting with REW a few weeks ago (did some more tinkering last night, and re-did all my BFD filters too). The graphs are from REW, and are at a very fine resolution, probably 1Hz or better. Sweeps take about 10seconds.

Graphs can look MUCH different if you change the dimensions of the graph. I stretched out the graph and attached it.

But your 180-deg graph doesn't look too bad, and the results aren't surprising considering the sub's behind you. With an eq you could bring the peak at 47~48Hz down and smooth the rest out a bit. If the dips at 60Hz and 67Hz are just variations and not true nulls, those could be smoothed out as well. The dips at 80Hz and 95Hz are normal, not too bad. Additional bass traps could help.

The 0-deg phase one isn't too bad either, at least up to 100Hz (need to see how it looks up to 200Hz or a bit higher to tell what it's doing to the bass in the 100s). That could easily be tamed with an eq.

With no eq, I'd choose the 180-deg phase because it doesn't have the HUGE dip between 55-65Hz or the huge peak from 65-80Hz. If the big peak at 47Hz was tamed with the 180-deg response, even just that would make a huge improvement and give you a nice curve, with a heavy <30Hz area.

You're definitely a good candidate for an eq. With either of those graphs, you could cut frequencies going to the sub and aim for a 70dB baseline, with flat response (or varying degree of house curve), then adjust the level of the sub to calibrate it correctly with the speakers.

If you get an eq, you can try experimenting with sub placement to work on the big dip/s, and then just eq the rest of the peaks down.

What helps is to run graphs for the speakers only, sub only, then combined with phase at 0/180 - so you can see how they are interacting. And run the graphs up to 200~400hz or so, to get the whole sub/speaker interaction picture.



Also, have you tried the sub in the front left corner? The response MAY be better there, if you can move the equipment around. That would be my first place to start.

Plus, bass traps in the front left, front right, rear left, and possibly but not necessarily rear right corner. The more the better.

cyberbri, you rock, excellent analysis and advice!

If I get brave enough to buy an external soundcard and necessary connections for my RS meter and then learn to use REW, maybe I will run some graphs (instead of the ridiculously time-consuming method of measuring individual 1/6th octave test tones :( ) and post them for your feedback.

[cyberbri]

You may be able to do it with your current soundcard.

With an SPL meter and a tripod, I bought a few connectors and had everything I needed. The hard part is making sure you don't get too much noise coming out of the output from the computer.

Headphone jack to 2x RCA, RCA to SPL meter

Headphone jack to 2x RCA, RCA to receiver/sub input.

I thought it would be complicated, but once I got into it, it's a breeze. I have a MCE PC, so configuring the inputs/outputs on the back (which can be used for 5.1 computer speakers instead of mic, aux, out) took a while to realize and figure out. That took about an hour. But after that it went very smooth, and I can run any test I want in a matter of seconds (once I'm set up and configured).

And once you get 1Hz/better resolution, you see how much 1/6 octave misses.

[Pete_Hsu]

Liaury, I have some questions for you: How exactly is the subwoofer placed (sideways, driver firing into the couch, etc)? Also, where are you placing the microphone when taking measurements? Finally, would it be possible to provide some measurements of the subs in the front left/right corners?

Unfortunately, the way your system is set up right now, the room is not very deep. So one thing that is most likely happening is that you are getting cancellation when one pressure wave moves forward and reflects back just as a second pressure wave moves forward. I would bet that if you were able to try a nearfield mid-bass/farfield low bass setup, your response would be significantly improved!

Another thing that would actually improve the sound would be to reorient the speakers so that they are along the short wall instead of along the long wall. This way, the room wouldn't be very wide, but it would be very deep, and there would be less need to worry about front and back reflections that lead to cancellation.

Thank you very much!

[Liaury]

Liaury, I have some questions for you: How exactly is the subwoofer placed (sideways, driver firing into the couch, etc)? Also, where are you placing the microphone when taking measurements? Finally, would it be possible to provide some measurements of the subs in the front left/right corners?

Unfortunately, the way your system is set up right now, the room is not very deep. So one thing that is most likely happening is that you are getting cancellation when one pressure wave moves forward and reflects back just as a second pressure wave moves forward. I would bet that if you were able to try a nearfield mid-bass/farfield low bass setup, your response would be significantly improved!

Another thing that would actually improve the sound would be to reorient the speakers so that they are along the short wall instead of along the long wall. This way, the room wouldn't be very wide, but it would be very deep, and there would be less need to worry about front and back reflections that lead to cancellation.

Thank you very much!

Thanks for chiming in.

Driver is firing away from the couch. Sub is literally up against the couch.

Rat Shack meter is located where my head would be (dead center), pointing up.

I can get some measurements of the sub in the front left corner. I will never place the sub in the front right coner. There is a door there that I did not show in my layout.

I especially appreciate the comment about the effects of the shallow room.

[Pete_Hsu]

Thanks for the feedback, Liuary! Have you noticed much of a difference when having the driver fire into the couch (1-2" spacing in between)? Also, what type of measurements do you get when the subwoofer is in the rear left corner?

Take care

[Liaury]

Thanks for the feedback, Liuary! Have you noticed much of a difference when having the driver fire into the couch (1-2" spacing in between)? Also, what type of measurements do you get when the subwoofer is in the rear left corner?

Take care
I apologize for not following up on this thread.

Special thank to cyberbri for his opinion on my curves.

And of course thanks to Peter, he is always there for us.

I've been living with my 3.3 along with RDES from AV123 for a while now. The sub is still behind by couch with the driver facing away from the couch. After I was able to apply EQ to tame much of the peak(s), I've became too busy enjoying movies with the 3.3 and PS3 (BluRay). I guess this is a good thing since many of us in this hobby are spending more of their time improving the experience rather than enjoying the experience.

Regardless, I hope to have some measurements from different sub locations and setting for ya this week.

[Pete_Hsu]

Hey Liaury,

Have you tried running the subwoofer so that it is sideways directly behind the couch, with the woofer firing into the couch? That is the config I would recommend, as opposed to having the woofer fire away from the couch.

Are you running maximum output mode or extended bass mode with port plug? What are your impressions when switching between these two modes?

Your room is not very deep, so you are most likely suffering from some reflections that are causing a lot of frequency response anomolies in the mid-bass range, and this is robbing impact. If you placed the VTF-3 Mk3 in the front left corner, and the MBM-12 sideways directly behind your couch, your system performance would improve in a huge way with respect to both sound quality and output capability.

I hope you have a chance to try it out with MBM-12.

Sincerely,

[Liaury]

Hey Liaury,

Have you tried running the subwoofer so that it is sideways directly behind the couch, with the woofer firing into the couch? That is the config I would recommend, as opposed to having the woofer fire away from the couch.

Are you running maximum output mode or extended bass mode with port plug? What are your impressions when switching between these two modes?

Your room is not very deep, so you are most likely suffering from some reflections that are causing a lot of frequency response anomolies in the mid-bass range, and this is robbing impact. If you placed the VTF-3 Mk3 in the front left corner, and the MBM-12 sideways directly behind your couch, your system performance would improve in a huge way with respect to both sound quality and output capability.

I hope you have a chance to try it out with MBM-12.

Sincerely,:eek: Peter, how did you pull this thread from the past?!

I've been enjoying my system too much to do more experimenting with the 3.3 since my last response in January. One thing I did to improve my system is to lower the x-over point of the front speakers from 80 Hz down to 60 Hz. That improved the bass impact of my system a lot. I tried 40 Hz, and although there was still some additional improvement with this iteration, I didn't feel it was as significant so I returned it to 60Hz.

With the sub driver facing the couch, it did "move" the couch a lot more. I actually didn't like this because I was so distracting IMO so I have it facing away.

I'm pretty sure you are right on the benefit off adding a MBM-12. Especially considering my needs in my system, but that's more $$$. I may try it in the future.

Thanks again,

Mr. Happy Hsu Sub Owner

[Pete_Hsu]

Hi Liaury, just checking up on a kind and gracious customer :)

Do you have space in your front left corner to place the true subwoofer? I would try that and see how it goes.

[Liaury]

Here are a couple of graphs for you to feast on. I believe when I took these measurements, the receiver crossed over to the sub at 80 Hz. I turned off my external amp so it is only measuring the sub output.

The first graph is the current position behind the couch. The second is the front left corner.

Keep in mind that with the speaks thrown into the mix, the response is a little different than what is graphed below. I plotted these graphs with the sub alone just to locate good position to start with.

[Pete_Hsu]

Thanks Liaury. As you can see, in your room (and in many other rooms), you get better mid/upper bass performance (50-100Hz) when the subwoofer in placed in the nearfield, and better deep bass performance (< 50Hz) when the subwoofer is placed in the farfield.

In the nearfield, you have a huge dip at 30Hz which is taking away some impact in that region.

In the farfield, you no longer have that dip at 30Hz, but you have even larger dips at 55Hz and 90Hz, which is taking away impact in that region.

By placing an MBM-12 in the nearfield (sideways behind the couch), and a VTF-3 Mk3 in the farfield, you will get much improved frequency response and much wider dynamic range. Since the MBM-12 is downfiring, it should not be distracting in the nearfield. I really think it would work great in your setup. Shipping cost is only $30, and there is a discount on MSRP for current Hsu customers, so opportunity cost to try out the unit is fairly small.

There is one alternative that is worth trying out if you don't want to test out the MBM-12. Try running the VTF-3 Mk3 in the front left corner, crossover frequency set at 50Hz. This way, the mid-bass and higher frequencies would come primarily from the main channel speakers, and only the deep bass would come from the true subwoofer. This could yield smoother mid-bass response vs using only a true subwoofer. Dynamic range probably wouldn't be as good as with MBM-12 in the nearfield, but this could be a good no-cost tweak in your system.

Do you have any frequency response graphs of your current setup crossed over at 60Hz, one with sub in nearfield and one with sub in farfield, including the main channel speakers in the response?

Thanks again.

[Liaury]

Woooh! OK, he's got some skills.

I've moved my sub to the front left "corner" of my room. Below is the before (behind couch) and after (front left corner) plots.

[Liaury]

It's late so I'll won't be able to post on this much. The change has been great! I'll post more tomorrow.

[Pete_Hsu]

Sweet, at least you got rid of that huge peak!

Let me know how it goes if you ever test drive an MBM-12 :)