"Shh, No Talking" Home Theater... - Page 10

Sub crawl would also help identify modal issues. E.g. with a sub at the LP, if you get a null at the IB's, then you have a better idea of what your working against.

What's the distance to your LP from your subs again?

I highly recommend reading a couple of the articles on house curves over at Home Theater Shack. You will get a better idea about where your bass should be vs the rest of your system. I aim for comfortable (-10db from reference) dialog or even softer and room shaking bass...but it depends on the movie and source. Dubstep/movies the bass can be ridiculous where on the same volume, rock will be loud, but relatively no bass. I am going to buy an EQ with presets to modify my curve on the fly to compensate for content.

When I run Audyssey, I put my sub amp on about half. Then afterward I put my amp full on. I then adjust my sub channel level on the AVR to my desired taste. I plan on redoing REW again when I have the room completed for a more elegant house curve, but this method works good enough for me. I don't think you will get max output without maxing your sub amp unless your amp is much more powerful than what your subs can handle (at mid/upper bass freqs -- you are excursion limited at low bass freqs). I am sure you are not even close to the limits of your subs...measuring voltage and excursion on test tones at max levels will tell you how much further you can push them, but if your vision isn't getting blurry with 4 x 18s you have a long way to go.

Have you tried turning the subs up until you're happy? I know the THX reference level for a sub is 10 db hotter than for the mains. 10 db may not sound like much, but it's perceived to be twice as loud (you probably know that already, but I like hearing myself sometimes ).


As a side note, I understand that most processors handle this 10 db offset, and level matching is the correct approach. BUT, if you're not happy with the bass, turn it up to where you are happy, and worry about the graphs later. Enjoy the theater, and let it be a hobby again rather than a pain in the arse and something that disappoints you every time you look at it. Set it so that you enjoy it, and then worry with what has to happen to make the graphs agree when you've got a holiday and want to fiddle with it.

A few qick Qs Chris:

1. are all of your measurements with the main speakers running or the subwoofers on their own?
2. What are you powering the MFWs & IB's with?
3. I saw mention of the EQ.2. Is this just on the MFWs?
4. You might have posted it, but in a quick scan I couldn't locate measurements of the MFWs alone (no IB) in the room at the rear locations or mid-wall, preferably from both rows.

The dip in the back row is a reality of the room acoustics for any bass source at the front wall, and one I've observed at the back row in more than a few rooms. You should be able to get very good performance from the front row, or at least one of the 2 rows, but getting both rows great will be a battle. Be sure to not measure too many things together, as you can't see what each is contributing. I'd suggest you would be better off with a DCX-2496 or MiniDSP to optimize things than the EQ.2, but it could be useful to confirm if either of the 2 DSP options would be of help.

Mark;
Here is the balance of the measurements, roughly a quarter of the way down is the small sealed MFW graphs. All the amp and EQ details in opening post I believe.

Thanks FOH. That helps.

Chris:

In the first post I see a simple point to re-visit and see if there is an easier compromise to start from for the setup and get some more encouraging results before diving too much deeper.

I'm going to make a quick observation below, but I'm going to preface this by stating these measurements should be re-taken before adjusting. If the "with LCR" was tested with all 3 LCR speakers playing, you're making things more difficult on yourself or at least more confusing. I recommend starting with just the center channel and the subwoofers, where you can send the same test signal to the L & R input with the mode set to DPL-Cinema (not Music). This will route the test signal to the center and subwoofer. You can later remove or turn off the L or R input to test the others, remembering the level will come out -3dB relative to the center channel.

I would also suggest raising the subwoofer level overall by 3-6dB before running these tests. Looking at just the lowest frequencies makes it easy to overlook the relative level of the 500-2kHz range where the calibrations signals and dialog loudness are roughly centered.

Remembering that 2 acoustic sources combining can run the gamut of maximum +6dB summation over the level of a single sub to a deep cancellation depending on phase/timing, let's look at the crossover region for both rows Chris posted in his first post linked above:
We see the front row has constructive combination occurring between the subs & LCR which is further emphasizing the peak near 60Hz, while the rear row measurement shows cancellation with the level droping below either speaker/sub individual measurement. An adjustment of the subwoofer distance would be the easiest to experiment with quickly. 60-70Hz equates to a 1/2 wavelength of 9.5' to 8'. We don't want full cancellation, so I would start by adding 4-5 ft. to the subwoofer distance. Before making this adjustment, measure the center channel + subwoofers as you currently have them. Now make the +4ms adjustment and repeat the measurement in both locations, making no other changes. I would then focus on the front row to make adjustments that best smooth the peak at 60Hz without major holes in the response. Now check what happened in the rear row. I suspect you will see the combined response above both of the individual responses. Not perfect, but it could be a big improvement and you haven't asked any more output from your speakers or subs.

First make these adjustments to get some improvement around the crossover. You can tinker with the 30Hz peak in the rear row after you get the front row sounding more impressive.

Hopefully that helps some.

I can't remember if it's encoded in the track or if the processor handles it, but in either case I believe level matching is the "correct" approach. However, my point was to turn up the bass until you can enjoy watching a movie. Then spend your spare time tweaking when you feel up to it. You seemed to be getting down about the whole thing and losing sight of the fact that it's supposed to be fun!

This is by no means the optimal solution, but some times you just have to have a carrot to keep you motivated

Hi Chris. I just dropped by to see what you were up to. I did a speed read of the thread to catch up. Looks like you are solving LF issues and are implementing a multi sub approach.

I saw someone mentioned the Geddes method and I wanted to add a link to Parham's version of that:
http://audioroundtable.com/forum/index.php?t=msg&&th=3387&goto=66914#msg_66914
The LF response you were getting with just the front subs in a relatively small room seems expected.
Good to know you are on your way to tackling the LF problem.

Chris, was the FMOD the only way you could add a HPF? Did you have any evidence that a HPF was needed, or was it just peace of mind insurance?

I was just hoping that you had a variable filter you could engage lower. (like 20Hz?)

Chris, I hope you get things sorted out. I went through a similar frustrating issue of being unable to listen to my sound system for over a year due to my ear sensitivity to Power amps or the XLR cables. Don't ask me why, but I still can not be in the same room with power amps and XLR cables. Hang in there , you will get it in the end, and you have some of the knowledgeable people in your thread giving advice.

Chris - it's been a couple weeks since the site has even logged you on the forums - so I know you're not in the middle of trouble shooting this. I hope you haven't really turned it all off in the mean time. Let us know.

All that's good to hear, and I too will still be glad to assist in whatever manner needed (even if that means no assist).

I'd like FOH to answer, but my understanding is that the position is less important (within a 1/4 wavelength) than phase and delay.

Essentially,it's the same.

It's all about the time domain, whether that's performed electronically, or physically. Physically, introduces other variables, but that's ok too.

The tactile feel associated with the deep stuff, is largely a function of the floor construction. Concrete, ... not much movement, crawlspace, or second floor, .. diaphramatic motion ensues.

Fwiw, I'd recommend Crowson, tactile actuators for such an effect. That's an entire diff story.