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"Shh, No Talking" Home Theater... - Page 9

post #241 of 300
Thread Starter 
UPDATE...

To hopefully better my LF issues, I found a member on here who was selling a couple of MFW-15's and another member who sold me his Element Designs eq.2 which will allow me to adjust phase for the rear subs and also allow me to run those two MFW's off of the 2nd channel on the EP4000. I'm also in the middle of building a couple of 2.5cuft boxes for the drivers and then stuff them with polyfill I guess.. I will post pictures hopefully tomorrow or friday!

smile.gif
post #242 of 300
I hope the two subs fix your issue of uneven bass over your seating areas. Will cross my fingers for you. wink.gif
post #243 of 300
That's great, ... two more tools in the quest.

Good lookin' out. Best of luck and keep us informed.
post #244 of 300
Thread Starter 
Thanks you guys, I hope to get the cabs buttoned up tomorrow and then temporarily fired up later tonight or worst case sunday for testing... possibly smile.gif

Man, that means I gotta make a new router circle jig! DOH!! rolleyes.gif

Or, I just jig saw the crap outta the driver holes! biggrin.gif
post #245 of 300
Thread Starter 
Alright , here they are, almost complete. They are all pre-screwed and braced. They are just about 2.5 cuft before bracing. I made them on the small side so I could make both boxes out of one 4x8 sheet of wood. I want your opinion on the bracing and what not before I put some glue and DAP in there smile.gif

bothcabsmfw.jpg

frontcabmfw.jpg
post #246 of 300
Thread Starter 
Progress, kind of cool.gif

I finally got my front wall insulated with that 3" rigid stuff I picked up. The boxes are also all sealed on the inside to prevent leaks and hopefully over the next couple of days I can test them out and see what kind of results they yield smile.gif

frontviewfrontwall.jpg

sideviewfrontwall.jpg

Oh, I also got my Element Designs eq.2 in the mail the other day so I can now control phase of the new subs cool.gif
post #247 of 300
Looks great...and you say you're doing nothing??
post #248 of 300
The front wall looks good. That should really offer a significant improvement damping energy off the front wall. This, combined with the mains toe in, ... good stuff.

Good luck w/the subs, they look good,.. nice and beefy.
post #249 of 300
Thread Starter 
Thank you fellas. The subs are all sealed up and ready for testing. I'm looking forward to seeing some better graphs tonight biggrin.gif

Stay tuned!!
post #250 of 300
Thread Starter 
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Can you tell I'm a little upset?

If you MUST know why, I will tell you...

I'm basically just fed up with this project. After all of the planning and research I did, I still managed to build my room wrong. I doubt I'm ever going to get both rows to sound similar in the LFE department. I was hoping to make it better by adding these two 15's, but after I did, the graphs just weren't very impressive at all. in fact, I feel that my table tuba helped more than the MFW's. I will post them later today and show you first hand but I needed to rant for now. I almost ran late for work because I was trying so many different things to get better graphs, but no such luck rolleyes.gif

And with this whole REW thing, what a great tool I tell ya but for some dumb reason I can't stay consistent with my readings, I don't understand why and it frustrates me like whoah! My graphs aren't even the same from before I tried the table tuba and now before I tried the MFW's. I know my scaling is correct now, but still.

Why oh why did I even start down this road? frown.gif
Edited by Digital_Chris - 8/10/12 at 3:11pm
post #251 of 300
Thread Starter 
Here are the graphs...

Front no MFW's...

frontnomfw.jpg

Front with MFW's...

frontwithmfw.jpg

Front overlaid...

frontoverlayed.jpg

Rear no MFW's...

rearnomfw.jpg

Rear with MFW's...

rearwithmfw.jpg

Rear overlaid...

rearoverlayed.jpg


So, you see, not much improvement. I originally had the Element Designs eq.2 in line so I could control phase but that had no good effect. It helped in one row while making it worse in the other, what the heck?!

These are the best readings I got with all of the placement options I played with, all of which were spread out behind the seats. front and rear subs are level matched and that's about it.

One question still remains, well many still remain but one that's on my mind right now is room modes. Do they affect the whole room or just parts of the room? I'm trying to figure out if my big peaks can even be tamed. I have the 60hz peak in the front row and the 30hz peak in the rear row. Hmm..

EDIT: I juist noticed my graphs aren't to spec, I must have redone the last one or two and posted THOSE results but they are similar enough for comparison purposes tongue.gif
Edited by Digital_Chris - 8/10/12 at 5:10am
post #252 of 300
I'm sure there is a solution - you'll get there.

In regards to the consistency of your results - are you using a mic stand and a marked position? Is the mic placement exactly consistent - is what I'm trying to get at. A plumb bob hanging from the mic stand over a mark on the floor with the mic at a standard orientation and a measured height.

In regards to the room modes - I feel confident personally that they are at the heart of your problem. A suggestion I have read that you may not have tried: put one sub in a tricorner - as close as you can get - place the mic in the opposite tricorner - diagonally across the room (ceiling, not floor). Run a sweep. This will put you in a position to excite and measure all the room modes simultaneously. Then we can compare that to the free-space response of the sub (MFW?) and by subtraction, find the relative influence of each mode. Sound good?

Fred
post #253 of 300
I guess this is why IBs can be tough since you can't change placement....well, you could, but it is a bit more work. Do you have any graphs with just the MFWs and no IBs? You'll get this issue taken care of, but realize that every theater/room has different FR plots for each location. You can move your mic 1" and it can make a big difference.
post #254 of 300
Thread Starter 
Here are a couple more graphs...

Front and back overlayed with one sub in each rear corner facing the corner, no superchunk bass traps...


frontbackoverlayedwithmfws.jpg

This is with both MFW's stacked in one corner with the mic in the opposite corner, IB subs disabled...

subsonecornermicoppositecorner.jpg
post #255 of 300
Correct me if I'm wrong, please: the IB array is in the front (duh), and you've been working with the MFWs in the rear corners.

Is it possible to place the MFWs at the midpoint of the length of the room - along the side walls - just for testing? I have a hunch you'll see major improvement in the 60Hz problems with that arrangement. If not, can you post the graph of the normal arrangement with 90 degrees phase adjustment for the MFWs - all subs driven? (I may be barking up the wrong tree here, but I don't think so)

Fred

P.S. - look at this - put in your dimensions (as nearly as you can) in the add room tab - notice the strong modes near 60 Hz - then select the "floor" tab and position your ears in the first and second rows, watching the changes - it's kinda awesome. http://amroc.andymel.eu/
post #256 of 300
You'll sort this out to audibly be fantastic.

I know it's frustrating, I can see that. But surely there exists, in your current array of gear, a combination that gets you the response you want. Now, that said, I'd suggest bring more sources to the fight. If your mains are up to it, lower their lowest operating frequency perhaps down to 60hz. Measure the sum of the entire sub system, and manipulate the time alignment of the fronts to the mains, then bring in the rears at a varying amount of delay until the response appears the smoothest. Knock down the peaks, then manipulate the time alignment again and render the subsequent response to taste.

Sure, easier said then done, but the crossovers used between the subs and to the mains, isn't a brick wall either direction. So the mains extend downward to allow interaction,...smoothing etc out of band. So the response of several drivers over-laps, thus adding to the response smoothing of multiple sources.

So whether the subs a in the rear, or a bit forward toward the front, you'll get this.


Best of luck
post #257 of 300
Thread Starter 
Quote:
Originally Posted by HopefulFred View Post

Correct me if I'm wrong, please: the IB array is in the front (duh), and you've been working with the MFWs in the rear corners.
Is it possible to place the MFWs at the midpoint of the length of the room - along the side walls - just for testing? I have a hunch you'll see major improvement in the 60Hz problems with that arrangement. If not, can you post the graph of the normal arrangement with 90 degrees phase adjustment for the MFWs - all subs driven? (I may be barking up the wrong tree here, but I don't think so)
Fred
P.S. - look at this - put in your dimensions (as nearly as you can) in the add room tab - notice the strong modes near 60 Hz - then select the "floor" tab and position your ears in the first and second rows, watching the changes - it's kinda awesome. http://amroc.andymel.eu/

You are correct about the arrangement. Here are a few graphs for you...

Front and rear rows before and after 90 degree phase change... The large 50hz dip is after phase change...

phase90deg.jpg

Subs at normal phase, MFW's located at side walls middle of room, before and after. A little change has been made to 60hz in red but very little, if anything a little worse at 50hz in blue...

mfwsmidpoint.jpg

Quote:
Originally Posted by FOH View Post

Measure the sum of the entire sub system, and manipulate the time alignment of the fronts to the mains, then bring in the rears at a varying amount of delay until the response appears the smoothest. Knock down the peaks, then manipulate the time alignment again and render the subsequent response to taste.

I'm having a hard time understanding what you are trying to ask me to do, it's a bit confusing to me redface.gif

On a side note, here are two graphs of my mains with no subs and then my subs with no mains, 60hz crossover. First graph rear row, 2nd graph is front row. Do they look odd at all? I'm still trying to figure out why there is such a steady decay from 30hz on up in the rear row.

mainsonlysubsonly60hzxover.jpg
mainsonlysubsonly60hzxoverfrontrow.jpg
Edited by Digital_Chris - 8/22/12 at 1:13am
post #258 of 300
Thread Starter 
Unfortunately, I haven't gotten too much farther with the issue. Tonight I was thinking that maybe I should toss the IB's out the window and go with 4 box subs eek.gif I say this because apparently, sub placement is critical and my current arrangement does more harm than good right now mad.gif

I really REALLY don't want to do that but I'm hating the current situation that I'm in, I can't even get a good taste for what the bad boys should sound like. It's eating me alive... well not really but it makes me not want to be down there. I STILL have to get my side wall treatments done too, I'm ready to do this but I just feel that I'm going to do it all wrong and waste my time. I guess I need to spend some time with the ETC graphs, not looking forward to it. Ughh..

In the mean time, if you guys have some thoughts on my recent graphs, I would love to hear them. FOH, when you get a chance, can you explain a little better to me what you were talking about earlier?

Thanks guys smile.gif
post #259 of 300
Thread Starter 
Just another note, I did a sweep for each seat and all seats in each row were fairly similar, graphs were all within a couple db of each other and had the same trend so I'm not too worried about exact mic position for the LFE sweeps smile.gif
post #260 of 300
Did you endeavor to level-match the MFWs with the IB? I'm not surprised that the IB has lots more output potential, but I think maybe you could be more effective with the filler subs with their gain cranked up a bit more. I make this assertion (guess) based on the relative levels of the graphs in post 254.
post #261 of 300
I'm not as well versed in this as a lot of people that have chimed in already, but I can only imagine your frustration.

With that said, have you taken any peak readings during any movies? I believe the PEAK, SUB, level is supposed to be 115 db. That's +10 db higher than the other channels peak value. I think it's been mentioned before that the sub channel is usually 10 db hot.

if I were in your shoes, I would start troubleshooting this systematically. You've got a couple extra subs that you can move around, so maybe disconnect all of your subs except one, and try moving it around. You'll need to "plug" your other subs somehow. Maybe put some foam over them to keep them from moving. You don't want them sucking energy out of your room. Try a sub crawl with that sub in the front row. Figure out where the "Best" place is for your sub, and then compare to where your IB is located. Maybe setup your room with the two subs in the "BEST" place with the IB disconnected and plugged, and compare to your results with all the subs running. This would at least ensure it's a location problem. Have you taken any measurements of the MFW's outside, perhaps? That would give you an idea of how they perform where modal issues are not a problem.

Also, have you double, triple, quadruple checked all of your wiring to make sure you don't have something out of phase? You don't have any low pass/highpass/bandpass filters inadvertently enabled? Are they all actually powered (again, if one is not it will will absorb energy from your room). You know your TT works well in the room, could you feed the wire from one of your IB's through the IB wall and drive your TT just to make sure everything is working well. Maybe try that with each IB sub?

I'm just throwing ideas out there that I would try if I was troubleshooting your problems.

Hang in there! You'll get it figured out!
post #262 of 300
It is easier to do a sub crawl by putting the sub at the LP and then just moving your ears to the best placement. You are more mobile than your subs. Check the DIY forum for more info on that.
post #263 of 300
+1

I suppose I was rambling a bit in my previous post, but absolutely. Put the sub in the front row in the spot you intend to use the most, and start crawling. However, another point is you can do this with multiple subs. So you might even try a sub crawl with the IB's running. Fire up the IB's, put 1 MFW in the front row, and start crawling around looking for a good response. Put your MFW there, then bring in the next one. Put it in the front row, crawl around again, and put it wherever you find the best response. Then you've optimized the placement with your IB's in place and working.

I'm rambling again, but my point is to start eliminating variables.

1) The first step I would take would be to make sure all the wiring is correct and to VERIFY that the IB's are all working and being driven in the proper phase.
2) Next I'd check to make sure the MFW's are working properly (polarity is correct, etc.).
3) Verify there are no inadvertent filters being added in the processing stream.
4) Then I might try a sub crawl with the IB's operating and one MFW in the "sweet spot."
4a) Put the sub in the best spot and recalibrate accordingly.
4b) Make sure nothing got worse after calibration
5) Repeat 4 for the next MFW.

Andreas had another good point with posting in the DIY speaker forum. There are some very knowledgeable people there.

Sorry for the rambling post. Feel free to ignore it smile.gif

EDIT: I'm not trying to be condescending here, or point out the obvious, but you don't want to change more than one thing at a time. If you change the wiring and add two subs, then you don't know which caused the problem. At this point, you sort of need to be methodical about your approach to find what's been overlooked. I'm guilty of getting carried away with something like this!
post #264 of 300
JPA: I agree. Initially it seemed like something was very off with his subs because he was saying he wasn't getting much bass....which seems a little crazy with four 18s in an IB. I just don't get that at all. With these wacky FR, I have no idea what is going on especially with the MWFs not doing much....but I do agree that the MWFs need to be leveled to the IBs as far as output. You can't expect the MWFs to fill the IB's hole at 80db if they are only putting out 70db.

Please post in the DIY forum. They do FR plots all day long there and the guys know what they are doing. Dedicated theater builders is likely not the right forum.

(Still rooting for you Chris!) smile.gif
post #265 of 300
Something may be amiss, I don't know. Maybe not.

I'd start from scratch eek.gif

You will find a combination that will be fine, with the front IB, and with the filler subs.

Yes, you need to assure proper polarity/proper acoustic summing of the IB drivers. I took for granted that was done.

The above mentioned the DIY forum, yeah, they're good. The real problem solvers are at GearSlutz,...worldclass.


There are a handful of different ways to approach the system EQing, but stick with one and that way you'll find find the best combo of settings. Now, there are some combos of loudspeakers and rooms that are particularly problematic. That may or may not be your case.


I would turn all the speakers except the subs off. Always start with all subs same phase. Ideally, you need the ability to individually set levels, and EQ, of each sub (the IB's as a unit, then either the rears as a unit, or rears individually. Test each sub set individually, set levels and EQ, then reset with all subs running.

When EQing, only knock the peaks off, never boost nulls. Again, ideally each sub should have separate equalizers. But, what ever your capability is (in groups, more the better), EQ one sub, or sub group. Then, move on to the second sub with the first sub playing with its settings. Then, proceeding to the next group, while all previous are playing, etc, etc.

When complete, readjust relative level accordingly to mate with center channel (mains). Also, manipulate the entire group EQ as a whole to fine tune more. Also, without getting lost in your progress, try phase (or delay) adjustments to see if any further smoothing is achieved. Also, a final touch of experimenting with this adjustment can help localization issues. Experiment, carefully, with notes and don't lose your progress.

---

Now, another approach is merely placing all subs in then locations, and prior to EQing each group, only try phase adjustment of each, seeing results immediately. Moving to next sub, etc. Then globally EQ the entire sub system as a unit.

---


I'd think that carefully moving through one of these approaches, will get you a nice, listenable response curve. I wish you were closer, I'd drive over to help you out. I can appreciate your frustration. You'll get this.


Now, question; how many sub groups do you have the capability of controlling in time and frequency? What tools do you currently have?




Best of luck
post #266 of 300
Quote:
Originally Posted by FOH View Post

Yes, you need to assure proper polarity/proper acoustic summing of the IB drivers. I took for granted that was done.

Can you elaborate on how to do this?
post #267 of 300
Quote:
Originally Posted by J_P_A View Post

Can you elaborate on how to do this?

Nothing fancy, polarity check w/battery one way, but that doesn't account for everything, so;

A nearfield mic, between each outside pair, and make sure they sum, then other outer pair, then last, assure both groups sum properly. like powered drivers when doubled, add approx 6dB


----

So, prior to beginning the EQ'ing, everything ideally should sum positively (ie front IB, and back sealed individually, then both compared to front IB. Even though phase and time delay may be added later, beginning at the same acoustic polarity is typically the best starting point.
post #268 of 300
Quote:
Originally Posted by FOH View Post

Nothing fancy, polarity check w/battery one way, but that doesn't account for everything, so;
A nearfield mic, between each outside pair, and make sure they sum, then other outer pair, then last, assure both groups sum properly. like powered drivers when doubled, add approx 6dB
----
So, prior to beginning the EQ'ing, everything ideally should sum positively (ie front IB, and back sealed individually, then both compared to front IB. Even though phase and time delay may be added later, beginning at the same acoustic polarity is typically the best starting point.

That makes sense. I'll add that to my bag of troubleshooting and setup goodies. Thanks for the tip!
post #269 of 300
Hey Chris, did you get to do any tweaking today?

If you haven't, or if it was fruitless, have a look at Dr. Geddes' approach to placing three subs. http://mehlau.net/audio/multisub_geddes/

Fred
post #270 of 300
Chris,
Any further attempts or questions?

I'd certainly be glad to help in any manner possible.
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