# My subs aren't IMAX subs



## eclipse911t (Jan 8, 2013)

Good Afternoon Gents,

I have a 17x23x9 room with a pair of Velodyne SC-15's running on an SC-1250 amplifier. I've been relatively happy with my system for some time now as they are not anemic in the least. However, I watched Interstellar in an IMAX theater last night and was blown away by the output. The room was literally pressurized.

I am wanting to get closer to this IMAX experience at home. What do you guys think are my best options?

1. Smaller room with same subs (planning on this in the new house anyway)
2. More of the same sub woofers/amplifiers (used)
3. DIY Sub woofer Options

I'm not sure if it was output or ULF that was really making the IMAX come to life, anyone familiar with their sub woofers and the frequency response? I believe they use cabinets with 4 smallish drivers (10"-12"?) in a ported (labyrinth?) arrangement, and generally use 4-6 cabinets for up to 24 drivers.


----------



## selden (Nov 15, 2009)

http://www.in70mm.com/newsletter/1997/50/imax_sound/index.htm


----------



## tonyvdb (Sep 5, 2007)

Keep in mind that Imax as well as the theaters are not targeting ultra low frequencies. They usually bottom out at 20Hz I bet if you were to take actual readings in that IMAX theater you were in your getting that in your chest pressure at around 30Hz They simply have some big subs behind that screen with alot of power behind them. Not to unreasonable to have 2000watts or more driving each sub.


----------



## eclipse911t (Jan 8, 2013)

selden said:


> http://www.in70mm.com/newsletter/1997/50/imax_sound/index.htm


Nope. This was a 16:9 digital cinema. Not a 70mm old school "real" IMAX setup. Sorry should have specified. It was in a 18 plex owned by Carmike.


----------



## eclipse911t (Jan 8, 2013)

tonyvdb said:


> Keep in mind that Imax as well as the theaters are not targeting ultra low frequencies. They usually bottom out at 20Hz I bet if you were to take actual readings in that IMAX theater you were in your getting that in your chest pressure at around 30Hz They simply have some big subs behind that screen with alot of power behind them. Not to unreasonable to have 2000watts or more driving each sub.


This was my assumption. I'm thinking the easiest solution is a smaller room.


----------



## willis7469 (Jan 31, 2014)

I think DIY. We have 3 surround systems in our house, and the smaller rooms are certainly easier to pressurize, but the larger room adds much more to a realistic presentation. It has better gear also, but the room goes away as do the speakers. Smaller rooms can also be more "modal", and harder to deal with. Fwiw, my big space is 17x26, in a sunken LR that is mirrored by the kitchen. Ceiling is vaulted 12' in the center. Kitchen is connected to a foyer/room maybe 15x 25. It doesn't pressurize in the same way, but the bass is much better overall, and still shakes the couch. I say you DIY a pair of 18" sonosubs and bust some Sheetrock!


----------



## eclipse911t (Jan 8, 2013)

Would you think the SC-1250 I currently have could drive a couple 18" sonosubs? 

Real world output is ~900w at 4 ohms. 
Any brand suggestions for drivers? In this case are you thinking ULF or just more output?

PS I have a DCX2496 on my subs.


----------



## willis7469 (Jan 31, 2014)

I guess I was thinking both. I think your velo's response is 22hz-120. Im sure they're not slouches, but I know there's more on the table. If budget is priority, I'd start looking here. 
http://www.parts-express.com/dayton-audio-um18-22-18-ultimax-dvc-subwoofer-2-ohms-per-coil--295-518
15's are worth looking at too. 
I'm curious to read about your current amp once we get passed supper etc.


----------



## Audiofan1 (Aug 16, 2013)

lddude:If this comes up again or you feel Imax envy and you have access to this in your theater? watch this and feel better about your subs and gear right away :hsd:


----------



## Dr. H (Nov 8, 2014)

tonyvdb said:


> Keep in mind that Imax as well as the theaters are not targeting ultra low frequencies. They usually bottom out at 20Hz I bet if you were to take actual readings in that IMAX theater you were in your getting that in your chest pressure at around 30Hz They simply have some big subs behind that screen with alot of power behind them. Not to unreasonable to have 2000watts or more driving each sub.


I was thinking the same thing.


----------



## eclipse911t (Jan 8, 2013)

I played the IMAX intro you linked to and some THX ones and DTS stuff. I could run the volume and subwoofer level up and pressurize the room just fine. I'm not out of subwoofer output in my room, but I don't have the chest impact I noticed in IMAX. 

Is this just a function of level? Of course I can run my sub hotter. I'm not sure if I want to though...
Could I put in a bump (or contour) at a certain frequency range and perhaps get there?

If it is an output problem (I'm not convinced) then I can perhaps DIY subs if I can make it relatively cost neutral by selling the Velodynes. 

OR

It is likely this will resolve itself in my future room at approximately one third the cu. ft. 

BTW: I'll also be moving to 5 ( or 7) identical studio monitors and getting away from an AT Screen, so sound should improve all around. I'll also be dropping from seating for 10 to only 4. The screen will likely stay at or near 120" but be nearly wall to wall. 

Summary:
If it's not an issue with ultimate output is there a particular target curve or process to increase visceral impact?
If it is level, then I have a couple options depending on when I build the next house.


----------



## tonyvdb (Sep 5, 2007)

Can we have a little more info about your room? 
Is the room completely sealed off from the rest of the house? Pressurization can only be possible if your room is closed off. 
How many cubic feet is your room?


----------



## eclipse911t (Jan 8, 2013)

17x23x9 so 3519 cu ft. 

Door is metal insulated with a threshold. Room has two layers of drywall with green glue. Outlets are not puttied, and there is a single small ceiling air vent. It's 6x8 and leads to a very long piece of flex duct with a number of bends in it. All walls/ceiling/riser/etc have insulation. 

More info here:
http://www.hometheatershack.com/for...ly/64735-eclipses-dedicated-theater-room.html


----------



## tonyvdb (Sep 5, 2007)

Those SC-15s should pressurize that space nicely. What level is the integra setting the output at? have you tried running REW? I would be interested in what your actually getting for a response in the room?


----------



## eclipse911t (Jan 8, 2013)

tonyvdb said:


> Those SC-15s should pressurize that space nicely. What level is the integra setting the output at? have you tried running REW? I would be interested in what your actually getting for a response in the room?


Yes, I have a UMIK-1 and REW. Please note that the below are with no EQ, and no smoothing, with the exception of the full range picture, it has no EQ and 1/12 smoothing. I'm not sure if I hung onto my post EQ measurements, but hopefully this will at least give an idea of what the room is doing until I can measure again.

Do you guys use a particular curve?


----------



## tonyvdb (Sep 5, 2007)

Hmmm, you have a large boost at about 25Hz and it falls off quite dramatically as you go up to 80Hz, that is not an ideal curve.
Is that what Audyssey is setting them at? How many positions are you reading when you run Audyssey and are you using a tripod for the Audyssey mic?


----------



## NBPk402 (Feb 21, 2012)

One or 2 Triax subs would def pressurize your room. We had a single Triax in our family room with 2 4' wide entrances to the room and it not only pressurized the room... It separated the hardwood flooring from the wall for about a 2/ long area!


----------



## willis7469 (Jan 31, 2014)

tonyvdb said:


> Hmmm, you have a large boost at about 25Hz and it falls off quite dramatically as you go up to 80Hz, that is not an ideal curve. Is that what Audyssey is setting them at? How many positions are you reading when you run Audyssey and are you using a tripod for the Audyssey mic?


 Also, I think by his room dims, room gain will start at about 25 hz. I wonder if that's what the bump is all about. Also, being sealed, they seem to drop very quickly after that. The listed freq response starts at 22hz. I'm assuming this is why.


----------



## eclipse911t (Jan 8, 2013)

ellisr63 said:


> One or 2 Triax subs would def pressurize your room. We had a single Triax in our family room with 2 4' wide entrances to the room and it not only pressurized the room... It separated the hardwood flooring from the wall for about a 2/ long area!


No doubt. Mine will as well when I push them as there is plenty of output available, but it just doesn't happen during a movie. I'll have to run REW again to see what levels are like now. I'm guessing I'm either missing a key frequency or there is a peak somewhere making them seem loud but not loud overall where you feel the impact.


----------



## eclipse911t (Jan 8, 2013)

tonyvdb said:


> Hmmm, you have a large boost at about 25Hz and it falls off quite dramatically as you go up to 80Hz, that is not an ideal curve. Is that what Audyssey is setting them at? How many positions are you reading when you run Audyssey and are you using a tripod for the Audyssey mic?


The measurements were with EQ off. That includes the DCX2496 and Audyssey. I run it at four to six positions. Typically six if I'm not just trying something new.

I'm going to go take measurements now and report back. I may try to mimic Wayne's hard knee house curve. Any thoughts?


----------



## eclipse911t (Jan 8, 2013)

Ok here's current state. I pushed the level up from 50 to 75 on the Velodyne and lowered my crossover from 70 to 65 and made it steeper at 48Hz versus 24. 

I'll give it a shot.


----------



## eclipse911t (Jan 8, 2013)

Here is full range before my changes today with 1/12 smoothing.


----------



## NBPk402 (Feb 21, 2012)

I think the feel it in the chest is closer to 100Hz.


----------



## eclipse911t (Jan 8, 2013)

Thanks! Will work on bringing that up and see.


----------



## eclipse911t (Jan 8, 2013)

Pushed the crossover up to 80 and dropped the level to 70 which is still +20 from the previous setting. Watched Live Die Repeat and it was more impressive. Will keep tweaking...

Open to suggestions.


----------



## NBPk402 (Feb 21, 2012)

eclipse911t said:


> Pushed the crossover up to 80 and dropped the level to 70 which is still +20 from the previous setting. Watched Live Die Repeat and it was more impressive. Will keep tweaking...
> 
> Open to suggestions.


Try your LFE at 100Hz (if your subs can go that high). :T


----------



## eclipse911t (Jan 8, 2013)

That should work. They're sealed so should be relatively smooth up there.


----------



## tonyvdb (Sep 5, 2007)

Ummm, Im not sure that a 100Hz crossover is ideal, you start getting localization issues that high. That feel it in your chest frequency range is between 60 and 80Hz the move your pant legs feeling is down around 20Hz


----------



## eclipse911t (Jan 8, 2013)

Yeah, 100 doesn't work. Tons of high frequency bass as expected.

I was thinking, in a commercial environment the LCR's are ran full range, so the level of LFE channel can be pushed without needing to worry as much about hearing the higher bass intended for the mains through a higher output level on the subwoofer. Boosting the subwoofer level only effects the LFE content.

For example a typical 80Hz setup all around will throw away the bass on the LFE track from 80-160 and the bass for the mains under 80 will be too loud if your subwoofer has its output 10db hot as done in a commercial cinemas.

Perhaps I should run my fronts full range and my subwoofer dedicated to the LFE channel crossed at 80-120Hz? Comments? This way I can increase the output to suggested +10 level and not effect the content intended for the LCR's.


----------



## willis7469 (Jan 31, 2014)

Something to think about. The LFE channel itself contains content up to 120hz, no matter what your crossed at, it will play that back accordingly. Unless you set set "ceiling" for the LFE channel. Also, imo, chest thumping bass runs between 20 and 60hz. Maybe up to 80. Think about most car subs, and bass cd's. Lots of them are tuned around 30. Blurred vision...


----------



## eclipse911t (Jan 8, 2013)

First off I think it's clear there is a large discrepancy regarding where everyone thinks the visceral impact is for bass content.

Secondly here is my order of crossovers, etc.

Integra Pre/Pro
LCR Crossover setting (bass redirection)
LFE Crossover setting (chops the top off the LFE track)
Also has some basic graphic EQ settings along with Audyssey

DCX2496
The crossover I actually use.
Also use this for PEQ

Velodyne SC-1250
The crossover is bypassed.
This also has an auto room correction.

I've tried many things, but I would like to get higher bass frequencies out of my subwoofers unless they are really supposed to be there.
The following settings made for a massive amount of higher bass content when it was clearly not needed.

Integra
LCR 100Hz
LFE 120Hz (highest setting)

DCX2496
90Hz 48db/octave

Velodyne
Bypass

I'm now trying this today to see if we can reduce this higher bass frequencies from the LCR bass management. This should reduce the content from the LCR's and let the LFE come through loud and clear. I'll let you guys know what I think.

Integra
LCR 50Hz (merely for some protection)
LFE 120Hz (highest setting)

DCX2496
100Hz 48db/octave

Velodyne
Bypass

What settings are you guys using?


----------



## tonyvdb (Sep 5, 2007)

My mains are running full range (see signature) with a HPF of 30Hz on my YDP2006
My centre is set at 70Hz as are my surrounds
I have my sub crossed over at 70Hz 

This seems to give me my best results as seen in this graph.


----------



## willis7469 (Jan 31, 2014)

I've used 50 on my mains for a long long time. 120 for LFE. 70 on surrounds and 80 for center. I think you will like your setup this way. 
Where are your subs in regarding placement? Sorry I don't recall any mention.


----------



## eclipse911t (Jan 8, 2013)

Ok, I think I've found a point where I am happy.

Integra
All Speakers are set to Full Range.
LFE Output is set to 120Hz which is as wide open as I can set it.

DCX2496
Crossover is set at BUT48 @ 100Hz
EQ Settings are as follows:
-5db @ 25Hz
+8.9db @ 50Hz
-15db @ 92Hz
-12db @ 109Hz (This creates a nice roll off from 40-100) Output was pretty flat before this last filter. Still A/Bing this one.

I'm only getting LFE in my subwoofers, which means I can keep the crossover nice and high while still having the output bumped by 10db. I'm not getting any footsteps or the like through the sub this way, only what the engineer intended to put in the LFE track.

I ran some test material, Man of Steel, MI:Ghost Protocol, Transformers, etc. and was please thus far. I'm sure I've killed my low bass for music since stereo mode will have zero subwoofer. I will test later on. Subwoofer level will likely need some more tweaking to taste. 

My only concern is speaker damage since there is no HP on the mains. The fronts are dual 6.5's so that is really the concern. The rears have 8's so they should be alright. I wish I could run a 50Hz filter on the fronts without bass redirection, but that would mean more equipment.

PS: While playing around I was able to hit 105db @ 20Hz and over 110db at 30-100Hz with the EQ in place at the listening position, so not an output problem.
Still open to suggestions.


----------



## primetimeguy (Jun 3, 2006)

eclipse911t said:


> Ok, I think I've found a point where I am happy.
> 
> Integra
> All Speakers are set to Full Range.
> ...


Glad you like what you are hearing but don't forgot there is a lot of bass in the main channels. Running them full range they may not be able to keep up, depending on your volume level. I'd think to get the pounding IMAX like bass you should focus more on the main channels than the LFE.


----------



## tonyvdb (Sep 5, 2007)

I would have to agree, running your mains at full range is going to be hard on them and probably unnecessary.


primetimeguy said:


> I'd think to get the pounding IMAX like bass you should focus more on the main channels than the LFE.


 Not a chance, you wont find many speakers that can produce those kind of pressurization levels. That job is meant for a sub.


----------



## JBrax (Oct 13, 2011)

tonyvdb said:


> I would have to agree, running your mains at full range is going to be hard on them and probably unnecessary.


 I agree with Tony here. No need for the additional load on the amp and if you have a quality sub/subs let them do what they were designed to do.


----------



## eclipse911t (Jan 8, 2013)

It's a GFA-5503. The amp isn't the issue. The speakers are 4ohm so they're seeing 350wpc. The real potential problem is letting the magic smoke out of one of the woofers. However it's been my experience thus far that the tweeters give out first in these Snells. Been down that road before. 

I may try them with a low crossover to compare the sound. I'll also run them at reference minus five later with the sub muted to see how the distortion levels sound.


----------



## primetimeguy (Jun 3, 2006)

tonyvdb said:


> I would have to agree, running your mains at full range is going to be hard on them and probably unnecessary.
> Not a chance, you wont find many speakers that can produce those kind of pressurization levels. That job is meant for a sub.


Right, what I meant by focusing on the main channels was crossing them over to the subs to actually be able to produce the loud bass that is mixed in those channels.


----------



## tonyvdb (Sep 5, 2007)

primetimeguy said:


> Right, what I meant by focusing on the main channels was crossing them over to the subs to actually be able to produce the loud bass that is mixed in those channels.


understood :T


----------



## eclipse911t (Jan 8, 2013)

Agreed guys. Makes perfect sense. 

However when I cross the mains at 50Hz as they are for this evening's movie I get quite a bit more <50 content that I'd like. Obviously I being the sub level down a tad and then my 50-100 is gone. 

Alternatively if I bring my crossover up to 80 from 50 then I get a fair amount of 50-100 content but it's not the right content. It's foot steps, booming, etc. 

Alternatives?


----------



## willis7469 (Jan 31, 2014)

Have you run a sweep since the last change? Maybe they're just too hot?


----------



## eclipse911t (Jan 8, 2013)

I really could run a comparative sweep since the mains were full range. I don't have HDMI to select audio channels. I guess I could use a 7.1 input from REW but ran them separate to test.

The issue is I'm trying to get the impact level up without them being over powering when they're not supposed to be heard. I feel like the IMAX was just more dynamic. I don't have any sort of equipment or compressors that would explain that.


----------



## willis7469 (Jan 31, 2014)

This might be hard to do,(it would be for me), but what if you set everything to where you liked it best up to this point. , and left the system off for 2 days, and came back to re-evaluate. Just an idea. 
I wonder also if some of the perception of dynamics was due to just plain more SPL?


----------



## eclipse911t (Jan 8, 2013)

I can agree with both points. I'll be in MX on business until Friday so the first point is easy. 

To the second point I do also agree. As an example reference level of 85db for dialog in a cinema or even the pulpit mic at church isn't unreasonable at all. But in a small room the same measured level seems very loud. At the moment the wife and I just finished a movie and are listening to what seems like somewhat loud music and it's peaking at a mere 72db.


----------

