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post #271 of 300 Old 09-03-2012, 01:07 AM - Thread Starter
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Thank you all for taking the time to respond. I have not done much more since last week, I've been busy renovation my bedroom and closet. I decided to come back down tonight to play around and did find something interesting. After I did the following test, I guess since the MFW's can't compete with the IB's, they actually won't do much good. I decided to unhook my IB's and run my MFW's only to see what results came of that. I found that with both MFW's in the front of the room, I got similar results (as compared to the IB's alone) only with about 7-8db less output. Now, if I have one MFW in front and the other right behind the rear center seat with the driver firing against the seat, I got MUCH better results in the back row except for a small sharp null at 30hz. My front row still had a huge 60hz rise but was smoother going up to it. Bottom line is that because the MFW's can't put out what the IB's can, it seems that they won't be much help in my situation.

To answer one of Fred's questions, yes, the the subs are level matched. If I play the IB's alone vs the MFW's alone, they both show 75db on my meter while using the receivers' test tone. I don't know why MFW's alone test at about 7-8db lower than the IB's alone

Also, all polarity seems fine, nothing out of wack.

Also, about placement. I don't feel the need to do a crawl test since I only have a few potential placement spots, but I wil try other tests to see what helps.

Here is graph comparing the IB's (with and without the rear MFW's) along with the MFW's alone. The red lines show the IB's alone vs the IB's with the MFW's in the rear, you can see that the MFW's helped slightly, by only by a few db. The blue lines show the MFW's (both up front vs one up front and one in the rear), what a difference! All FR's are of the rear row where I have that large 30hz mountain.

mfwvsibrearrow.jpg
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post #272 of 300 Old 09-04-2012, 07:20 AM
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Quote:
Originally Posted by Digital_Chris View Post

...........
Also, about placement. I don't feel the need to do a crawl test since I only have a few potential placement spots, but I wil try other tests to see what helps.
..........


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?

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post #273 of 300 Old 09-04-2012, 02:01 PM - Thread Starter
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Roughly 9ft front row and 13ft back row.
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post #274 of 300 Old 09-09-2012, 10:47 PM - Thread Starter
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So, while I'm awaiting some feedback on my most recent graph, I would like to post a question that I have been thinking about lately.

First, lets take the front row for instance. I'm pretty flat up to about 60hz and I have level matched my sub output to that of my mains, but why oh why is there almost no bass present? I really feel almost no low end in the front row. Same goes for the back row if I EQ out the huge 30hz muontain. Why does it seem like I would have to seriously crank either the AVR volume or the gain on the EP4000 / sub gain in the AVR to get decent results?

It's been bothering me because I read about other folks buying regular box subs (granted they can be pretty massive like the Seaton Submersive, and others in that range) and they seem to rock the house of said purchaser! But why do I feel like I really need to crank it up to ear piercing levels to enjoy the LFE part of my system? I guess I need to take some SPL reading during some scenes that I'm familiar with and see what you guys think of my current levels. If I play The Incredible Hulk at my comfortable but still kind of loud volume, there is almost no bass in the front row. I guess bottom line is that at the volume I listen at, the bass is almost non existent. I feel that I should still have the bass "rumble" even at lower volumes.. What's wrong with this? rolleyes.gif
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post #275 of 300 Old 09-10-2012, 04:18 AM
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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.

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post #276 of 300 Old 09-10-2012, 07:44 AM
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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 smile.gif ).


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.

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post #277 of 300 Old 09-10-2012, 10:58 AM
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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.

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post #278 of 300 Old 09-10-2012, 04:33 PM
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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.

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post #279 of 300 Old 09-10-2012, 07:45 PM
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Quote:
Originally Posted by FOH View Post

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:
Quote:
Originally Posted by Digital_Chris View Post

Front row overlaid...

Subs only = purple
Mains only = red
Subs + Mains = green

frontrowoverayedsubsmainssubsmains.jpg

Rear row overlaid...

Subs only = purple
Mains only = blue
Subs + Mains = green

rearrowoverlayedsubsmainssubsmains.jpg

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.
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post #280 of 300 Old 09-14-2012, 05:51 AM - Thread Starter
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Just a quick note to JPA, I'm pretty sure that the 10db hot LFE is already in the soundtrack and needs no further upping of the LFE channel via processor or subwoofer amp, someone correct me if I'm wrong but I was under your impression a while ago then I did some more reading.

And thanks Mark, I did a little more testing today without the mains in the mix and set the crossover to 250hz and I made a startling discovery!! If I put one MFW in each rear corner firing into the corner bass trap, my rear row is IMPRESSIVELY improved! Take a look! Bue is IB's alone and Red is with the MFW's in the corners.

rearrownew.jpg

I tried the MFW's in all other spots back there before and nothing had a change like this did, but today I WILL try those other spots again just to confirm that firing INTO the corner actually does the trick!

The front row has a change as well, in a good/bad way I suppose. What do you think?

frontrownew.jpg

Now another funny thing, this is all with no EQ inline, just rca from AVR to EP4000. If I add the BFD inline and deactivate all EQ functions, I get a few db rise over the whole graph, is this normal?

frontrowbfdinline.jpg

rearrowbfdinline.jpg
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post #281 of 300 Old 09-14-2012, 10:45 AM
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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 biggrin.gif

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post #282 of 300 Old 09-18-2012, 10:00 PM - Thread Starter
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Ladies and gentlemen, I have some VERY good results from the other night! I think I've mentioned this already but whenever I added my mains to the mix, the freq response goes bonkers! So, I decided to play with crossovers and sub distance. After about a half hour of playing around, I came to a very acceptable setting! X-Over at 60hz and sub distance at, wait for it...... 1ft !!!

I went from this (60hz x-over and true speaker distance)...

allat60hzxoverandtruedistancenofmod.jpg

To this just by dropping the subwoofer distance in the AVR down to 1 ft!!!

alltogether60hzxoversubdistance1ft.jpg

My only concern is with the MFW's... I had to turn them up about 5-6db higher than the IB's to get this flat... I'm worried about over excursion of the MFW's at lower freq. I decided to add in a 30hz FMOD for the MFW's and this is what happened...

alltogether60hzxoversubdistance1ft30hzfmodadded.jpg

WTF?
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post #283 of 300 Old 09-19-2012, 01:24 PM
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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.
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post #284 of 300 Old 09-19-2012, 01:47 PM
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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?
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post #285 of 300 Old 09-19-2012, 03:11 PM - Thread Starter
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The FMOD wasn't the only way, the other being the eq.2 which had a subsonic filter on it. If I set that to 30hz and turned the switch "on", it totally messed up my graphs, worse than the FMOD. I also wanted to add it for peace of mind, not sure if they are in danger but I assumed so because I had to turn up the MFW's more than the IB's, a good 5-6 db higher. But the MFW's also help quite a bit in the 30hz range so I don't want to add a 30hz hpf, any other suggestions?

Thanks Skywave, I'll take a look at the link you posted smile.gif
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post #286 of 300 Old 09-19-2012, 04:30 PM
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I was just hoping that you had a variable filter you could engage lower. (like 20Hz?)
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post #287 of 300 Old 09-19-2012, 04:48 PM - Thread Starter
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I'll give the eq.2 another shot at 20hz and we'll see what that yields.
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post #288 of 300 Old 10-04-2012, 03:30 PM - Thread Starter
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Well, the eq.2 subsonic filter does more damage than good no matter what freq I set it at, so that's a no go. I do have some good results from last night but most likely won't be able to keep them, here's why. I ended up cranking the MFW's up more than last time and then added a 30hz boost to the MFW's of roughly 5db. On top of that, I played with x-over points and subwoofer distances until I came up with this...

newoverlaywitheq2_zps2f68e3cd.jpg

Looks great, right? Here's another thought. I have feasibility of taking two of the IB drivers and mounting them on the wall in the rear right corner of the room. I just need confirmation from the IB forums that this will work.

On a weird note, even after I got this flat via REW, when I play music, the bass notes and bass drums are at least 6-8 db louder in the front row vs the back row. No where on my graph in the bassy region do I see that sweep except around 170hz. Front row is red btw.

These notes I'm hearing/feeling a difference in could be higher than 200hz, I don't know.
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post #289 of 300 Old 11-26-2012, 10:22 PM - Thread Starter
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So it's been a while since my last post so I thought I'd freshen this up a tad.

In a nut shell, I took two of my front IB drivers and placed them in a manifold in the rear left corner of my theater so I could take advantage of the multiple sub placement approach. Unfortunately, so far, not much has changed as far as sound to the room or my graphs. I played around with REW a bit last night before work but was unhappy with it all. I will post pics of the setup later today, hopefully, and maybe I'll hear back from the IB guru's on the other forum with their thoughts.
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post #290 of 300 Old 01-21-2013, 02:06 AM
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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. smile.gif

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post #291 of 300 Old 03-18-2013, 07:42 PM
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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. smile.gif
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post #292 of 300 Old 03-19-2013, 05:55 AM - Thread Starter
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Hey Fred, thanks for keeping tabs on my thread smile.gif

I haven't given up on the whole theater but DID decide to take it out of commission until I got all of my HVAC done. I'm currently and slowly installing central air in the house and plan on plumbing in the theater at the same time. I'm not doing ANYTHING in there until that is done because one, it's winter and cold so it's not fun bundling un in a blanket just to watch a movie on the big screen and I HATE seeing dust in the air every time I turn on the lights, NOT good for the projector, obviously.

That's the scoop, so hopefully in the next month or so, I can start finishing up in there smile.gif
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post #293 of 300 Old 03-21-2013, 08:43 AM
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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). eek.gif

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post #294 of 300 Old 03-21-2013, 10:09 AM - Thread Starter
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Thanks FOH smile.gif

Now, to keep this thread alive, let's talk about a few things.

One, when installing a 2nd sub in the back of the room (in my case, two of my IB's), what plays a bigger part in correctly tuning the two sets to get a more even room response... placement of the rear subs or signal tuning via time delay, etc? I ask because I got different results between the IB's in the rear corner and the MFW's placed in the center of the back wall. I don't mind finding a way to tune the rear subs but if placement plays a bigger role, I'm out of luck if the rear corner is no good.

Two, does position of the IB configuration (wall, floor or ceiling mounted drivers) affect the floor shaking LFE that a lot of people seem to acquire from their IB setups? I'm still trying to figure out why I didn't seem to feel the super low frequencies like others raved about.
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post #295 of 300 Old 03-21-2013, 10:23 AM
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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.
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post #296 of 300 Old 03-23-2013, 08:49 AM
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Quote:
Originally Posted by Digital_Chris View Post

One, when installing a 2nd sub in the back of the room (in my case, two of my IB's), what plays a bigger part in correctly tuning the two sets to get a more even room response... placement of the rear subs or signal tuning via time delay, etc? I ask because I got different results between the IB's in the rear corner and the MFW's placed in the center of the back wall. I don't mind finding a way to tune the rear subs but if placement plays a bigger role, I'm out of luck if the rear corner is no good.

Two, does position of the IB configuration (wall, floor or ceiling mounted drivers) affect the floor shaking LFE that a lot of people seem to acquire from their IB setups? I'm still trying to figure out why I didn't seem to feel the super low frequencies like others raved about.


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.

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post #297 of 300 Old 01-27-2014, 10:47 AM - Thread Starter
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Wow, 8 months or so and no update from me redface.gif

Well, theater is coming back online, kind of. I'm debating on whether to keep the IB's or not, still need to order some rigid insulation for front row first reflection points as well as back wall and still working on a dusty room mad.gif

I noted that I moved two of the IB drivers to the rear corner of the room, in the end I don't really want them there anyway due to them taking up the space that my equipment was going to go into, obstructs room for corner bass traps there, and they don't seem to make much of a difference anyway..

I might sell the IB's and just use the MFW's since the IB's don't provide the LF chair rumbling that I was after rolleyes.gif

Anyway, just a quick update on where I'm heading.
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post #298 of 300 Old 02-22-2014, 04:10 AM
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Chris - welcome back to tweaking your HT....

In this thread you started Early reflection panel thickness..., you asked Q's on the 1" recommendation that is in the Acoustical Treatments Master Thread sticky early posts, and I believe you came to the conclusion 1" was not appropriate and and went with 3", correct?
Your post here shows using 3"
http://www.avsforum.com/t/1290765/shh-no-talking-home-theater/210#post_22045778

Did you take ETC charts and if so what did they show?
Subjectively how does your set-up sound?
Key is minimal usage of treatments just to attenuate your first reflections -20db within first 25-30ms of the direct sound, not put treatments on not needed surfaces.

Looking in this thread did I miss your final side wall pictures?

I like what you did with your front baffle wall.

I see you are also tweaking your LFE, considering ditching the IB sub and going sealed cabs....for me I as able to achieve flat freq resp in my 1st row by addition of 2 subs to my IB line array, 1 I placed along front wall at 1/4 in from LH side and 2nd on LH side wall 1/4 in from front.

I see your thread in the IB cult also...
http://ibsubwoofers.proboards.com/thread/1686/new-poster-theater-build-considering?page=5

hopefully being away has re-charged your batteries, and given you new insight.

Good luck.
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post #299 of 300 Old 02-24-2014, 09:08 AM - Thread Starter
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Thanks for the reply mtbdudex, I did recharge my batteries, so long though, to the point I forgot how they go back in the system! tongue.gif

I went back in the room a few weeks ago to get myself familiar with taking measurements again and for the love of god I could not figure out why I was getting no mic input!! I finally figured out that I think it's because of the new "mavericks" OSX on my mac so I was able to find a work around with some extra software and it now works, weird.

I was and still kind of am contemplating on ditching the IB's so I don't have so much tweaking to do but not sure. If I keep them, I will tune them to sound good for my rear row which is where I usually sit because the difference between the two rows is ridiculous, BUT, once I tweak for the rear row, the front will still sound almost non-existent in the LFE world. I want both rows to feel the bass, I just do not get that right now. If I ditch the IB's, I will put one 15 in the front of the theater and one in the back, if I keep the IB's, I will have bnoth 15's int he back of the room which is where I had best test results with playing around with all subs. I just don't know my best route, really, it's tiring.

I did go with 3": panels and the ones in that link you provided is the old stuff that I got rid of. I just recently ordered some fresh 3" panels so those will get placed soon. I will get back and take some ETC measurements once the insulation arrives. Overall, the rear row sound stage sounds pretty good but the front row is a bit mushy and harsh, I'm hoping the correct treatment will fix that.

Any advice you can give about the IB's, I'm all ears. Btw, do you have a house curve on your system?
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post #300 of 300 Old 02-24-2014, 01:26 PM
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Chris ; I feel your pain on going back to REW and just getting the gear out for measuring, I took pictures just to remind me the cables and set-up.

So dis-appointed you are not getting more from your IB sub.
Back to basics:
-how are they wired, what amp are you using, and what watts/driver are they seeing based on wiring?
-Are you using outboard PEQ or MiniDSP or?
I know you have (had) a horizontal 4 x 18" line array from pictures, then split that up into a 2 x 18" array up front and a 2 x 18" manifold in the rear.

Besides REW/Mic, you have a RS SPL? I've felt using that, while playing test tones of trouble freq, and moving seat-seat and row-row helped me grasp issues gut feel better than looking at a 10-200hz sweep and seeing lots of nulls/peaks. I used that to focus on the trouble spots.

Have paper, and mark results to correlate to the REW sweeps and peaks / nulls.
Mark Seaton chimed in on a thread you had in the Audio area, do you think that thread is more appropriate to tweak your IB sub before you throw the towel in on it?
If so, I'll move my comments there and not respond further here.....

Good luck and welcome back again.
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