VTF-15 Impressions...and a problem

[RipcordAFF]

So I received the VTF-15 a week ago and I have been putting it through its paces. First, I am extremely impressed with the packaging and the sub itself. It is physically very imposing and the fit and finish appears to be top notch. I personally dig the triangular design of the front grill and ports, but it definitely makes the sub stand out (so WAF might be an issue for some).

I plugged the VTF in and played a sub test track that I got years ago, a series of bass lines that bounce around from 25hz to about 70hz. My first impressions were very positive. It clearly had much more power in reserve than my MFW-15 that it is replacing. Also very apparent was the "clean" and "smooth" nature of the sound (sorry, I am terrible at describing these things). As compared to my MFW, the VTF is much more precise. Initially very pleased, I settled down to dial everything in....

That's when the problems seem to be cropping up.

My current system consists of AV123 Rockets + Emotiva XPA-5 and an Onkyo 805 in pre\pro duty. I set the VTF settings initially at 1 port open, Q7 and Eq 1. I can't REW to work properly, so I did some ghetto measurements (running one of those stepped sine curves which gives tones are regular Hz levels and taking db readings).

Without running Audyssey, I noticed that the 30-45 hz range was 10 db higher than the 50-70hz range. This obviously created a very uneven response curve. I then ran audyssey and the entire range stabilized. From 20hz to 80hz, I was getting readings within 2 dbs of each other. Very very pleased, I turned on some movies.

Immediately, I noticed that the midbass was greatly reduced. In scenes that I knew were bass heavy, there was just something missing. There was no "explosiveness", that "kick in your chest" feeling wasn't there. I could tell that the sub was doing something, there was deep bass rumble, but no mid-bass impact. Now, my first thought was "of course there isn't you dummy, your midbass was 10db hot, Audyssey tamed that down", and this was confirmed by my own db readings post-Audyssey. But I manually set the sub level in the AVR hot by 5-7 dbs, I really feel like that if I have a flat frequency response, and the sub was 5-7 dbs hotter than the mains, I should be getting much more midbass. I certainly think I was getting more from the old MFW.

Turning off the Audyssey curve returned a good deal of this midbass. But this isn't a long term solution b\c of the uneven nature of that frequency curve. Besides, I like what Audyssey does with the main speakers, so I would like to use it.

Another potential solution would be changing the sub's internal settings. I am confused here too. These two frequency response graphs, showing the potential settings of the VTF illustrate my confusion

http://www.avsforum.com/avs-vb/showpost.php?p=19683927&postcount=769

http://www.avsforum.com/avs-vb/showpost.php?p=19723811&postcount=802

The graphs show, and my initial (sans-Audyssey) frequency sweeps generally support, that 1 port, Q7, Eq1 is far and away the strongest in the deep bass. Furthermore, that configuration apparently only looses a few dbs in the midbass. That seems like the ideal configuration. A config that would supposedly give more midbass is 2 ports open, q7, eq2. But that configuration is WAY off below 20hz and only 2-3 dbs stronger in the midbass....to me, that isn't worth it.

So I am confused, I am missing the midbass slam, but my numbers, and the numbers on these graphs, don't seem to explain why. I THINK I am getting a flat response curve...but I don't think it sounds all that great..

Any thoughts?

[monkuboy]

Have you heard of a "house curve?" While your response curve may be relatively flat, your natural sense of hearing is not - at lower listening levels, the ear perceives low frequencies as softer than the higher frequencies. The article below discusses using a house curve, which in effect boosts the lower frequencies to compensate for our own hearing curve:

http://www.hometheatershack.com/forums/rew-forum/96-house-curve-what-why-you-need-how-do.html

[notchyours]

So you are saying the MFW did not have the same peak at 30-45 hz compared to 50-70hz with no eq or audyssey when it was running in the same spot?

[JerryMeeker]

Your response graphs look very different from my graph (attached), which shows an REW 8-position average with Audyssey active. My X-over to the mains is at 60 Hz. Overall bass is strong and smooth.

What is that huge dip in your graph at ~65Hz?

[Sputter]

I asked him the same questions on AH but no response yet.
I feel his issues are related to a much cleaner and flatter response over what he was getting before. A lot of people don't like a flat response in the real world because it sounds flat lol.
I think he needs a "house curve".
A lot of key pieces of info are missing as well, room size, placement etc.

[RipcordAFF]

I asked him the same questions on AH but no response yet.
I feel his issues are related to a much cleaner and flatter response over what he was getting before. A lot of people don't like a flat response in the real world because it sounds flat lol.
I think he needs a "house curve".
A lot of key pieces of info are missing as well, room size, placement etc.

The house curve thing makes sense I suppose. The boost at the low end would be desirable in some circumstances (but that doesn't apply here, the low end is currently great, I am speaking specifically about the midbass). A house curve would create a the uneven frequency response in the midbass, but I don't see how people could see that as desirable. Some frequencies are just artificially boosted while others are reduced...Either way, I think its a moot point, the MFW was Audysseyed just the same as the VTF. While I didn't take measurements of the MFW after Audyssey, I would imagine it would be roughly similar given the good job it did with the VTF.

My room is about 12x18, with a small open doorway. The VTF is the corner, away from the doorway, in the same spot as the MFW.

I guess what confuses me most is the fact that frequency response is pretty flat (I will really work on getting REW to work--I was getting wonky graphs when I tried it last). But when I run the sub really hot in the AVR, the deep bass goes way up, accordingly, but there still isnt that "slam"\"compression"\"kick to your chest" feeling. I really feel that if the midbass was keeping up, that sensation should appear (even if I wasn't used to a "flat" response curve).

I want to make sure my settings are correct. I think I want to use 1 port to avoid the big roll off in the deep stuff created by 2 port open. I am currently also using Eq1, Q7. I understand that these settings will produce the least amount of midbass, perhaps accentuating my problem. However, when I look at these graphs, (not my graphs mind you, but indicative I think of the different configs)

http://www.avsforum.com/avs-vb/showpost.php?p=19683927&postcount=769

That seems like the correct config. 1 port, Q7, Eq1 gives by far the flattest response curve. Isn't that what we are going for in subwoofers? Why would I want to use Eq2 that just rolls off at about 28hz (scroll down to the graph with averaged Eq settings)?

Agan, I apologize for asking such dumb question. I am new to this, especially new to such customizable subs.

Thanks everyone for the help!

[RipcordAFF]

Ok, I think I got REW working. Its just a rat shack meter (w cal. file) so its likely not very accurate, but you get the drift. The "Aud" in my measurement traces indicate if Audyssey is engaged or not. There is no smoothing

You can see that Audyssey does do a good job at helping that null between 45-80, but its still quite a bit off the lower bass. Phase reverse makes it 100x worse so thats not really an option. It actually looks like 2 ports OPEN is actually just as good as 1 port, EQ2..why would that be? Does that mean I should use that to get more midbass? And I suppose 1 port, eq1 (my old settings) is too hot in the low bass (room gain?)?

So I guess this illustrates exactly what my problem was, but I am no closer to really solving it.

Thanks!

[RipcordAFF]

forgot to attached the graph

full size here http://i.imgur.com/ZPfjM.png

[JerryMeeker]

My apology, I thought the link showed graphs from your system.

Bass "punch" is normally attributed to the 50-80 Hz response range. If you have a room that is 16x20x8, then you have a primary mode associated with the 20 ft dimension at 57 Hz, and secondary modes associated with both the 16 ft and 8 ft (height) dimensions at 71 Hz. All these modes fall within the range of the mid-bass punch you say is missing. The fact that mid-bass doesn't improve as you raise the sub trim in the AVR supports this theory--you can't address a mode by raising trims.

The best way to address room modes is to experiment with sub placement, and the only way to determine the correct placement is by trying different locations and measuring the results (and trying different primary seating locations, of course). Since you provide no graphs, there is no way to be sure that your placement is optimized. I recommend you overcome the issues you are having with REW and get some good measurements. BTW, corner placement of a sub is considered one of the worst placements...

Once placement is as good as it gets, and if you are still unhappy with the results, you might consider a sub equalizer. I highly recommend the SVS AS-EQ1, which improves the resolution of the sub calibration over the standard Audyssey MultEQ XT. In addition, the AS-EQ1 provides "before" and "after" graphs of the sub response, as per the example below. Another option is a second sub.

Good bass is difficult to achieve, but it sure is fun trying! Good luck.

[JerryMeeker]

What is that huge drop-off after 80 Hz? What is your crossover setting for the mains? The response below 80 Hz actually looks pretty good.

In your AVR, is Audyssey Dynamic EQ enabled?

[RipcordAFF]

What is that huge drop-off after 80 Hz? What is your crossover setting for the mains? The response below 80 Hz actually looks pretty good.

In your AVR, is Audyssey Dynamic EQ enabled?

I don't have Audyssey dynamic EQ in my AVR I don't believe (onkyo 805). And I am not sure what huge dip is around 100hz. Its there no matter what I do and it doesnt seem to exist when I take manual readings... All speakers are crossed at 80hz

[Bill Mitchell]

I agree with Jerry that the hole between 100Hz and 140Hz is striking.

Is your graph of the sub with the fronts? Or is it from the sub alone?

As your amplifier is separate, you should be able to turn the fronts off by turning the amp off. You could then raise the crossover to its maximum possible value in the Onkyo and measure how high the sub reaches in your room.

You should also be able to turn the sub off, set the front speakers to Large/Full-range in the Onkyo and see what their response is in the room, without the sub.

These experiments should help you isolate what is happening, whether you have a large suck-out in your room for some reason, whether the woofer is blown in one or both of your front speakers, or something else all together.

[RipcordAFF]

Bill,

I have done some investigating, and isolated things as best I can. Unfortunately, I don't really know how to interpret this stuff. Any ideas what could be happening in these graphs.

Sub alone, 3 different crossovers demonstrated

http://i.imgur.com/CS27t.png

Speakers full range, no sub

http://i.imgur.com/T5Eg7.png

Everything on, crossed at 80

http://i.imgur.com/kHmSV.png


Everything on, sub alone, and speakers alone overlayed...

http://i.imgur.com/98MoC.png


Also, I realize that my REW trace graphs lists the cross at 90hz, that should read 80, that trace was done with the sub crossed at 80

Thanks!

[kinggimp]

I had a similar problem with my vtf-2 mk3. The low end was great but I didn't have the midbass. I ended up running my sub in a overdamped mode. It is set to two ports open with one port plugged. This rolls off the bass sooner so the deep bass is not so high compared to the midbass. I wonder if there is a setting on the subwoofer that would allow you to do the same thing. Maybe should give the company a call to see if they can help you out with it.

[Bill Mitchell]

... Sub alone, 3 different crossovers demonstrated ...

So the sub alone has reasonable extension when the crossover is raised, although there is a dip in the room in the 120-140Hz range.

... Speakers full range, no sub ...

The mains seem to have a sharp dip at ~110Hz and ~130Hz. This is probably from something about the placement of the front speakers or the position of the listening position/mic relative to the walls. (There could be some interaction here between the two front speakers. You might be able to determine if this is true by measuring the left and right front speakers separately.)

... Everything on, crossed at 80 ...

When the sub is used with the fronts, the notch around 100Hz appears and is very deep. The combined response is worse than either response separately. This almost screams at me that Audyssey tried to calculate the distance correctly to the sub, but got confused about something when analyzing the impulse response and got the distance off. How does the calculated distance compare to the physical distance?

I wrote a thread in the REW forum describing a methodology I used with REW v5 to tune my sub distance (http://www.hometheatershack.com/forums/rew-forum/28894-case-study-sub-alignment-using-rew-v5.html), when Audyssey set it a little too short. Or you could use the trial-and-error approach of varying the distance until you see a smooth curve with REW.

Have you tried inverting the sub phase switch at the sub? This did not help me much, as the sub distance was off by a value other than 180° at the crossover, but it does help some people.

[notchyours]

Bill,

I have done some investigating, and isolated things as best I can. Unfortunately, I don't really know how to interpret this stuff. Any ideas what could be happening in these graphs.

Sub alone, 3 different crossovers demonstrated

http://i.imgur.com/CS27t.png

Speakers full range, no sub

http://i.imgur.com/T5Eg7.png

Everything on, crossed at 80

http://i.imgur.com/kHmSV.png


Everything on, sub alone, and speakers alone overlayed...

http://i.imgur.com/98MoC.png


Also, I realize that my REW trace graphs lists the cross at 90hz, that should read 80, that trace was done with the sub crossed at 80

Thanks!


With these graphs, what you are seeing is how your room is affecting bass response with different settings. Your first mission is to isolate the subwoofers response in the room. Run sweeps with Audyssey disabled, and your crossover in the Onkyo 805 up to at least 120hz for the time being and see what different locations and tuning configurations on the sub are doing to the Frequency Response.

Please double check the back of the subwoofer and make sure the subs internal crossover is not active. If you end up moving the sub a lot, it is easy to accidentally change setting on the amp.

What you need to see in order to achieve your desired effect is for the response between 50-80hz to be louder or at least just as loud as everything lower than 50hz. I would start with a 2 port open configuration and move the sub around the room measuring each placement.

Your graphs show that you have a pretty good response in your room, but your low end room gain is causing the 1 port plugged config. to overpower your midbass.

The speakers running in full range show that they aren't doing a good job down low, and that is because of their placement relative to the listening position and room acoustics, not their native performance. Crossing these over at 80hz with your sub makes all the difference. Even where you have it now isn't too bad, it is just heavy in the lowest octaves. I think you should do a graph of the response with the system as is but change the sub config. to both ports open and experiment with the Q setting. A lower Q setting will probably be better.

Once you find the best position for the sub, and the best port and Q configuration, then you need to run Audyssey again. Make sure the phase on the sub is at 0 when running Audyssey. After Audyssey, you can experiment with the phase setting and distance setting of the sub in the Onkyo to try getting rid of any nulls around the crossover point.

[RipcordAFF]

Bill, Notch,

Thanks for the ideas. I have not had a chance to play with REW too much the last few days, but I spoke to Pete on the telephone for a while. He agreed that the rising room gain was likely enough for my low end needs and should take some measurements with 2 ports open. I will also play a bit with Audyssey and attempt to investigate that big dip..i'm not convinced that that is real though...perhaps a weird reflection? When I take manual DB reading at 100 hz its not nearly that bad...

[dalumberjack]

Good bass is difficult to achieve, but it sure is fun trying! Good luck.

Thats what they told me. So I bought two and but them on either side of the couch. Maybe he should do the same lol