Time for a second Sub. Suggestions needed

[mystik610]

Father's day is around the corner and I thought I'd use this as an opportunity to treat myself to a second sub. For the record, I love my VTF-3, and despite the size of my living-room, it performs well enough to leave my ears a little numb after watching the first LOTR on Blu-ray at close to reference levels :). But as with any audio purchase, the honeymoon phase passes, and the limitations to your systems start to 'itch'.

One thing that's always bothered me is the uneven frequency response across different parts of the room....it's something that's noticeable without whipping out the SPL meter. This has less to do with the sub itself, and much more to do with the layout of my room. The subs output drops changes significantly from one seating position to the next. Where my sub is situated now, the LFE track actually sounds best in the kitchen and the study upstairs (two enclosed areas in the house). I'm attaching pics so you can see what I'm working with.....I'm sure most would agree its an acoustic nightmare.

Another area I've always felt my lfe channel was lacking was in the upper-bass region....the VTF-3 does a wonderful job of producing the gut-wrenching super low frequencies that rattle your bones, and an OK job of giving you that smack you in the chest mid-bass impact. The other day I was playing Battlefield Bad Company 2, and noticed that the sub had trouble articulating the gun-shots....granted, the game has a poorly produced LFE track IMO, that vastly exaggerates the mid and upper-bass frequencies (explosions in the game sound like audible rumbles in the 40-50hz range), but it really highlighted the limitations of the VTF-3 in my set-up.

I went back and studied an old excel sheet I made when I first measured my VTF-3 last year, and noticed that there's a sloping 10db drop in output going from 65hz to 85hz that was fairly consistent between the VTF-3 in ME and MO mode. I also measured the STF-2 I was auditioning back then, and comparatively, it had a sloping db drop in output going from 65hz to 85hz.

Given all of that, I'm contemplating two options...either adding a second VTF-3, or adding an MBM. A third option would be to sell the VTF-3 and pick up a ULS-15, which would cost me about the same, but is a lot more trouble lol.

Any suggestions would be greatly appreciated!

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[Pete_Hsu]

Hi mystik,

The most straightforward thing to do would be to add another VTF-3 MK3. Would you be able to place it near the fireplace right next to the couch where that stuffed animal is placed in the first picture?

Note that with your current VTF-3 MK3, changing the orientation of the driver should help a bit with upper bass frequencies. To the extent that there are any items directly in front of the driver, the frequency response may be affected in the mid/upper bass frequencies at seating locations away from the direct radiating path of the driver. So try to do the best you can to clear some obstacles directly in that path.

May I ask what settings you currently have on the sub amp and on the receiver with respect to crossover frequency?

Thanks

Sincerely,

[mystik610]

thanks pete,

unfortunately i'm pretty sure the waf would prevent me from keeping a sub right there. the null i was hoping to eliminate is on the right side of the listening area....on the opposite side of where my sub is currently.

i did try putting the sub near thr fireplace just now, and it sounds a little anemic there. turning the sub so the driver faces my listening are has helped tremendously....it still doesnt give that chest slamminh punch, but it mid bass is more articulate. i originally had the ports firing into the wall to benefiy from a little room gain, but so far thr sub sounds better with the ports facing the front of the room and the driver facing the listening area.

as for the sub settings....the gain is set to 9.5 o clock and the lfe channel is set to +1 on the onkyo
as for thr sub settings

[Pete_Hsu]

Placement of the subwoofer close to the fireplace will be fine for deep bass reproduction but not great for mid-bass reproduction, so that's probably why you felt it was anemic in that location.

Can you place one VTF-3 MK3 in between the two couches (close to where it is shown in the picture), and place another VTF-3 MK3 on the other end of the couch (the end closer to the kitchen area)?

Is there any particular seat or seats that you would like to optimize for?

On the subwoofer amp, presumably you have crossover set to 'Out' correct? Are you using an 80Hz crossover for all channels on the receiver?

[mystik610]

Placement of the subwoofer close to the fireplace will be fine for deep bass reproduction but not great for mid-bass reproduction, so that's probably why you felt it was anemic in that location.

Can you place one VTF-3 MK3 in between the two couches (close to where it is shown in the picture), and place another VTF-3 MK3 on the other end of the couch (the end closer to the kitchen area)?

Is there any particular seat or seats that you would like to optimize for?

On the subwoofer amp, presumably you have crossover set to 'Out' correct? Are you using an 80Hz crossover for all channels on the receiver?

I contemplated putting the sub on the other side of the couch before and tried it out, but unfortunately the size of the sub doesn't leave any room to walk past that area. The other fear is leaving the sub controls exposed where my son could access them. It would really suck if he turned the volume knob all the way up one day lol.

Really the only other position that I think would work for a second sub is to the right of my mains, close to the kitchen. What do you think of placement there? I had it there before, and it sounded similar to the way it sounds close the fireplace. I moved it nearfield because it has more impact there...probably because my room is really deep and the mid-bass doesn't reach the listening position from a farfield position. I can tell the deep bass sounding better far-field though. I've noticed that the deep bass notes sound cleaner when I'm standing further away from the sub. From a nearfield position the low frequencies sound kind of 'compacted' at times...the low frequencies seem to sound better when they travel and have room to 'stretch out'.

All of this kind of has me learning towards an MBM between the two couches, and the VTF-3 to the right of the listening area. Do you think this would be more beneficial?

Oh and I do have the crossovers set to 'out' on the sub, but am running my fronts full-band and my rears crossed at 70hz. I know the general rule of thumb is to use an 80hz crossover for the mains, but my ears liked this better. Is there any detriment to this? The low-pass filter is set at 80hz for the LFE channel.

Thanks Pete!

[Bill Mitchell]

... Oh and I do have the crossovers set to 'out' on the sub, but am running my fronts full-band and my rears crossed at 70hz. I know the general rule of thumb is to use an 80hz crossover for the mains, but my ears liked this better. Is there any detriment to this? ...

I don't know what cutoff frequency the Onkyo uses to determine when to set the speakers to full range after the Audyssey setup process. So you don't really know how much off the low end you might be losing by leaving the fronts as full range, unless you use something like REW (http://www.hometheatershack.com/roomeq/) to measure the actual response in your room. The other advantage of setting a crossover is that, by moving the lowest frequencies to the sub, this leaves more headroom in the receiver's amplifier for the other frequencies. As the receiver (http://www.onkyousa.com/model.cfm?m=TX-SR706&class=Receiver&p=s) is rated at 100W/channel and the Polk site (http://www.polkaudio.com/homeaudio/specs/recent/rti8/) recommends a maximum of 250W without giving a sensitivity figure, this suggests your speakers could benefit from more headroom in the amp. As I recall, the Onkyo offers choices in increments of 10Hz, so you could experiment with a low crossover for the fronts, starting with 40Hz which the manufacturer documents as the -3dB rolloff point.

Bill

[Pete_Hsu]

Mystik, I'd say it is worthwhile for you to try out the MBM-12 MK2. Feel free to experiment with location of the VTF sub and the MBM.

Bill is correct when describing the impact of setting the main speakers to 'Full Band'. It would be better to use some form of crossover for the mains, whether it is 40Hz/60Hz/80Hz/etc.

Sincerely,

[JerryMeeker]

Your room, like mine, looks like a challenge to find a fairly flat bass response. With a single sub, you are always going to have spots where the bass sounds loud, and other spots where it sounds weak. It has been demonstrated by many HT owners that adding a second sub can go a long way towards taming the peaks and dips, if the subs are placed carefully. So, I would recommend a second sub, rather than replacing your current sub with a ULS-15. I have two two subs, and by experimenting with placement (measured by REW), I was able to find a reasonably flat response. In additoin, it is important that the subs be the same (same manufacturer, same model number).

You will find it difficult to find the best placement for your sub(s) if you leave your mains configured for full frequency spectrum, i.e. you can't tell whether the bass response issues you are hearing are being caused by the sub or the mains. I highly recommend setting all speakers to "small" to engage bass management, and to set the crossover to at least 80 Hz. Let the sub do the job it is intended for. Once you have made these changes, finding the optimum placement for your singe sub (or better yet, your two subs) will be much easier.

As far as adding a MBM, while I have no direct experience with this system, I don't see how it will address your issue. Having two single speakers addressing different ranges in the bass region doesn't sound like it would address the peaks and dips as well as two identical speakers addressing the same bass range. Once you have tamed the response with a second sub for the low bass, and if you still feel the mid-bass is lacking, that's the time to consider the MBM. Just my opinion.

[Pete_Hsu]

When one uses two or more identical subwoofers separated in the room handling the same frequencies, there can be cancellation which may lead to a dip in the frequency response at the listening position at some particular frequency or frequencies. A two-way subwoofer system with one or more MBM to handle mid-bass and one or more true sub(s) to handle deep bass can help to improve that.

In mystik's case, his layout poses some difficulties when using multiple identical true subwoofers. One is that the room is not symmetrical in any way. Another is that each true subwoofer will not be equidistant from the main listening position.

But then again, his layout poses some difficulties when using one MBM with one true sub. It is difficult to get good mid-bass across a wide variety of seats with just one MBM.

Having one MBM nearfield and one VTF sub farfield should result in a flatter overall bass response at the listening position vs just one VTF sub nearfield. Having one VTF sub nearfield and one VTF sub farfield should result in flatter overall bass response at the listening position vs just one VTF sub nearfield too. So it's a tough choice because it's hard to predict what the frequency response will look like in these two different scenarios.

Sincerely,

[mystik610]

I don't know what cutoff frequency the Onkyo uses to determine when to set the speakers to full range after the Audyssey setup process. So you don't really know how much off the low end you might be losing by leaving the fronts as full range, unless you use something like REW (http://www.hometheatershack.com/roomeq/) to measure the actual response in your room. The other advantage of setting a crossover is that, by moving the lowest frequencies to the sub, this leaves more headroom in the receiver's amplifier for the other frequencies. As the receiver (http://www.onkyousa.com/model.cfm?m=TX-SR706&class=Receiver&p=s) is rated at 100W/channel and the Polk site (http://www.polkaudio.com/homeaudio/specs/recent/rti8/) recommends a maximum of 250W without giving a sensitivity figure, this suggests your speakers could benefit from more headroom in the amp. As I recall, the Onkyo offers choices in increments of 10Hz, so you could experiment with a low crossover for the fronts, starting with 40Hz which the manufacturer documents as the -3dB rolloff point.

Bill

I believe Audyssey will set your speakers to full-band if it detects any output below 40hz. I used to run my fronts with an 80hz cross-over until I added the HK amp....its suprisingly powerful...far more powerful than the Onkyo, although they have the same quoted WPC (HK tends to underrate their gear). The HK really brought out the mid-range, and now the RTi8's and CSi5 are very punchy in the upper bass regions. I've been running them full-range ever since.

I did try using an 80z crossover last night, and decided this morning while doing my P90x workouts that I didn't like it. The male voices don't has as much depth, and the cheesy musical soundtrack didn't have the same level of fullness and punch to it. I've been playing these videos almost every day for a while now, and although it isn't the best reference material in the world, I'm very familiar with it. I did follow your advice and am using a 40hz crossover point. It makes sense that a lot of the amps 'juice' is being wasted on the lower frequencies.

Setting a lower cross-over point for the mains seems to fill-out the mid-range across the sound-stage, and creates a more seamless integration between the sub and my mains...particularly when listening to music.

[mystik610]

When one uses two or more identical subwoofers separated in the room handling the same frequencies, there can be cancellation which may lead to a dip in the frequency response at the listening position at some particular frequency or frequencies. A two-way subwoofer system with one or more MBM to handle mid-bass and one or more true sub(s) to handle deep bass can help to improve that.

In mystik's case, his layout poses some difficulties when using multiple identical true subwoofers. One is that the room is not symmetrical in any way. Another is that each true subwoofer will not be equidistant from the main listening position.

But then again, his layout poses some difficulties when using one MBM with one true sub. It is difficult to get good mid-bass across a wide variety of seats with just one MBM.

Having one MBM nearfield and one VTF sub farfield should result in a flatter overall bass response at the listening position vs just one VTF sub nearfield. Having one VTF sub nearfield and one VTF sub farfield should result in flatter overall bass response at the listening position vs just one VTF sub nearfield too. So it's a tough choice because it's hard to predict what the frequency response will look like in these two different scenarios.

Sincerely,

When I was auditioning the STF-2 I actually experimented with a dual sub set-up with the STF-2 nearfield, and the VTF-3 far-field...and there actually was some bass cancellation in the lower frequencies. Its kind of odd thing to experience, when you know the subs are engaged, and very little LFE material is being heard from the listening area.

I've measured the output from the nearfield position and farfield to the right of my mains before....and suprisingly, the output of the lower frequencies is very similar at the two locations. In hindsight, I think what I was appreciating with a nearfield placement is the impact of the mid-bass...with the VTF-3 sitting in the farfield position, the driver is actually firing out of the room, and into the kitchen.

My gut is telling me to go with an MBM.....flattening the overall LFE response across different seating positions seems like a much larger endeavor than flattening the frequency response from my primary seating positions (the left and middle seats on my couch) by reinforcing the mid-bass. I'm thinking that adding a second VTF-3 would strengthen the deep bass, but further accentuate the lacking mid-bass in my room.

Any thoughts?

[Ddavidson]

IMO the near-field MBM would be the most beneficial. It is indeed quite an endeavor to balance frequencies across multiple room seating positions. It becomes a matter of compromise in most rooms.

Ddavidson