# New REW user. Does this look "right"?



## shinksma (Aug 12, 2010)

Hi, 

Attached is an REW graph of my subwoofer's response at the listening position.

SW is an Epik Empire. It is positioned just left of my center channel, up front, since that seems to have provided the most even response (as seen in the graph) at the primary (front and center) and secondary (left seat of front row) positions. The REW PC is connected to analog audio input of my receiver, so response is Fronts + SW. Crossover set to 80 Hz in receiver. The behavior below 80Hz is what I'm most concerned with roght now.

Feel free to critique obvious-to-you errors that are causing a non-ideal response, such as "well obviously you didn't load the Radio Shack SPL meter calibration file correctly", or "your SW level is too high", etc. Actually, I'm sure the SW level is a little too hot (compare response above 80 Hz), but the overall trend below 80 Hz, especially 15Hz to 50 Hz is what is I'm trying to assess/fix.

I enabled display of mic/meter calibration curve - the black line (downloaded from here) - does that look about right?

If the graph looks typical for an uncorrected response, is it mostly correctable using a BFD?

Thanks, 

shinksma


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## Wayne A. Pflughaupt (Apr 13, 2006)

Welcome to the Forum, shinksma!

Everything looks good, REW-wise. Response – looks problematic. It’s going to require some pretty severe equalizing to tame that big hump, which typically isn’t a good thing. It might be good to post a sub-only graph, just in case your main speakers are a contributing factor. Also, try some other locations for the subs, if that’s an option. A center-wall location often gets bad response.

Regards,
Wayne


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## shinksma (Aug 12, 2010)

OK, here are a few more graphs, with the SW connected directly to PC out, so no mains involved.

They are titled as positioned. The first one is the same position as my original post. The next couple are away from the walls - one 4 ft from the left and front (I called it "back" in the graphic), the other much further out (maybe 7 ft and 6 ft). The final graph is with the SW positioned as an end-table to my front row of seats.

Comments? Recommendations? Other suggestions for SW positioning to try? (Other than "all possible positions in the room"?)

The most-middle-of-the-room position seems the best fit, but that isn't really an option to just have it sit there...

shinksma


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## Wayne A. Pflughaupt (Apr 13, 2006)

None of those look much better. Is there a corner available that you could try?

Regards,
Wayne


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## glaufman (Nov 25, 2007)

Corner would porbbaly help the low end, but would just as easily exacerbate that broad peak, no?
Perhaps a diagram of the room is in order.
How are the chances of moving the listening position?


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## Wayne A. Pflughaupt (Apr 13, 2006)

Perhaps, perhaps not. Every room is different, but I’ve seen more instances than not where corner or near-corner placement got a response curve that could be equalized. Can’t hurt to check. :T

Regards,
Wayne


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## shinksma (Aug 12, 2010)

glaufman said:


> Corner would porbbaly help the low end, but would just as easily exacerbate that broad peak, no?
> Perhaps a diagram of the room is in order.
> How are the chances of moving the listening position?


Here's a quick layout of the room. there is a lot more clutter (guitars, amps, a PC, some media racks), but the main gist of the room is there. Main problem is prime seat is pretty well dead-center of room. And that's where I like it. However, I will take some measurements from a position further forward to emulate a different seating position - one that isn't in the prime null/peak spot. Rear seats are on a 9" riser.

EDIT: Oh yeah, the bookshelves along the back wall go pretty well to the ceiling, and are crammed full of books, mostly.

Based on yesterday's measurements, the Sub is currently situated about halfway between the front seat row and the front wall, in front of the right armrest of the rightmost chair. I need to take some measurements from there, but I've run out of time tonight, so perhaps tomorrow...

Thanks for the suggestions so far, hopefully we can tame that response curve a bit.

shinksma


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## Wayne A. Pflughaupt (Apr 13, 2006)

> Based on yesterday's measurements, the Sub is currently situated about halfway between the front seat row and the front wall, in front of the right armrest of the rightmost chair.


As in, right out in the middle of the floor, away from any boundaries? Probably couldn’t get a worse location than that...

Regards,
Wayne


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## kflory (Feb 6, 2010)

What tool did you use for your drawing?

I have been using Visio, but I cannot rotate things to show them at a angle like you did (maybe I need to upgrade )


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## shinksma (Aug 12, 2010)

I use Visio - not a very new version either. Not trying to turn this into a Visio help thread, but don't you have the rotate tool on the tool bar (usually to the right of the Mouse Pointer Select tool)? Looks like an undo button at first (counterclockwise swirl). Select that tool, grab a corner and rotate the object.

Edit: I have a slightly newer version of Visio at work, and to rotate an object you just grab the "tail" that sticks out to one side or another.

And I forgot to mention room dimensions: front wall is about 21 ft across, and right side wall (beside double doors) is about 20 ft long.

shinksma


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## shinksma (Aug 12, 2010)

Wayne A. Pflughaupt said:


> As in, right out in the middle of the floor, away from any boundaries? Probably couldn’t get a worse location than that...
> 
> Regards,
> Wayne


I tried a couple more locations after my measurements that I posted above, and that is where it ended up last. I hope to take some measurements tonight at the current location, and tight in a front corner. And as mentioned, with a simulated listening position different from current. Any other spots to randomly try?

Thanks, 

shinksma


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## shinksma (Aug 12, 2010)

Alrighty then...I think I've found a manageable combination of SW and listening positions.

See attached. By placing the SW in the corner, as suggested by Wayne, the response in the current/old LP was not much better (actually it looks a bit worse, IMHO). See the first graph.

However, by placing the mike/meter forward about three (3) feet, I get the response in the second graph. Not perfect, but much more manageable I think.

The "secondary" LPs to the left and right in the front row have an even better response. (I didn't upload that - don't want to over-upload).

The rear row center seat is a little problematic: almost all SW positions resulted in a null around or just below 40Hz. Some were horrendous drops to sharp nulls, while others were just really deep but actually had a bottom. I'm not going to try to improve that position's room response specifically, but I will make a measurement after I've "fixed" the front row center (after moving the front row forward a bit...).

So thanks for the SW placement suggestions. Now, is the new LP response reasonably correctable? Or am I pushing water uphill?

shinksma


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## kflory (Feb 6, 2010)

shinksma said:


> I have a slightly newer version of Visio at work, and to rotate an object you just grab the "tail" that sticks out to one side or another.
> shinksma


Yes, found it. Just helped knowing it was there some where. 

Thanks!

PS: Nice drawing by the way


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## shinksma (Aug 12, 2010)

OK, tweaking some more. Left the SW position where it was. Measured from slightly left of centerline - basically the armrest position. What a difference yet again.

So, any further thoughts based on this new graph? Wish I could get better response from 25Hz down...

shinksma


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## electrostat (Feb 16, 2010)

The Epik Empire boasts on its website that, "not only does this subwoofer have deep bass extension, but it can also belt-out insane midbass. Even a separate midbass module can’t match the overall output of the Empire subwoofer." You have a sub that seems to be X-overd well above the 80HZ general movie(THX) standard. I suggest the the sub is just being what it is and the room is helping a bit. Lower the X-over point with the adjustment knob, and see if that makes a difference. Also do separate readings for the mains only and then the sub only this will help you to determine the X-0ver point. Also you have a square room which can be somewhat predictable, measure the room and try to place the sub in a null of that frequency. Floyd Toole has some great diagrams in his latest book.

Cheers


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## Wayne A. Pflughaupt (Apr 13, 2006)

I must be off my game not to have noticed the apparent lack of a low pass filter in most of your graphs that Mark mentioned. What’s going on there? Do you have one of those receivers where the crossover is only active with Dolby Digital? Or maybe (like Mark said) this sub’s midbass output is so tremendous that it effectively blows out the crossover?

Regards,
Wayne


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## shinksma (Aug 12, 2010)

For the purpose of my initial measurements I took the AVR out of the loop, in case it was causing issues. I meant to work it back in last night, but didn't get the chance - too busy focused on the below-60hz behavior. (My AVR crossover is normally set to 80Hz.)

I'll do more measurements tonight looking at the whole system (SW output only - disabling the mains).

So the graphs are what I expect, since there is no cross-over (I'm plugged directly into the LFE input of the Empire, so the SW cross-over isn't active either).

Sorry, should have mentioned that. When I said "SW only", I really meant it...

shinksma


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## shinksma (Aug 12, 2010)

OK, round I-don't-know-what:

Attached are a couple of measurements with the AVR in the loop, but mains disconnected, so just SW response through AVR. (I stop the measurement at 150Hz, in case anyone was worried about lack of signal above that.)

The first is essentially the left armrest of my new listening position (center front row). The second is the left armrest of the left seat in the front row.

The overall drop off matches expectations of an 80 Hz crossover (based on my lousy overall room response).

the peak at 55Hz is a room mode (20.3 ft along front wall: 1120ft/sec / 20.3ft = 55 Hz or so). The drop off just above 80 Hz matches a room mode null across the room diagonal, which means there should be a peak just above 40Hz - and there may be a mild one in most of my plots but it is swamped by the peak around 47Hz - not sure what that is caused by (one of the diagonals along a wall?). 

So, can I start with either as a basis for room corrections? Can I recover any of that below 25Hz drop off? Is that drop off a result of me not measuring correctly? A bad SPL meter? Or just a lousy room?

Is this too much for even a BFD to attempt to tame?

shinksma


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## electrostat (Feb 16, 2010)

your latest in corner graph is looking much better, How does it sound? Below 25 hz your SPL meter is probably not spot on and will need to be used as a guide rather than a rule. The peak in the roll off as 90hz might become a problem as well, but now that the other big peaks are removed put in a movie and try it out. The latest "Clash of the Titans" flick has some great subsonic material, most notedly during the mount olympus scenes. If the peaky tones are distracting then you might have to do more EQ or treatments. I have a JBL LS120, not a huge sub but respectable enough, and I have found that no matter how hard I try it wont go flat to 25hz. The specs say it should behave within +-3db but that is in a dead room, in my room that is not the case. (vaulted cealing with a grid detail) Yet I enjoy it allot. I have started to design some treatments out of dense foam and will do my best to tame the front and back walls first, but I expect that there will be many failures before I find some solution, and then with my luck I will have to move to a different house. However I enjoy my not perfect room it has a nice over all tonal balance, If the room sounds nice when you play notes in it what the.... Any way I would just try small changes in the position of the sub at this point, move it into the corner 10 more inches, or out 10 more inches, might be a sweet spot there somewhere. And then treatments and EQ.


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## Wayne A. Pflughaupt (Apr 13, 2006)

> Can I recover any of that below 25Hz drop off? Is that drop off a result of me not measuring correctly? A bad SPL meter? Or just a lousy room?
> 
> Is this too much for even a BFD to attempt to tame?


Looks like corner placement and re-locating the front row did the trick; this response is “equalizable.”

However, I’m at a loss as to what’s causing the poor extension. Everything I can find on your Epik tells me it should have strong output all the way down to and below 20 Hz. A poor room will affect the overall response – e.g. sharp nulls that can’t be fixed – but a poor room should have no affect on extension. That’s typically a function of the sub’s capabilities, or the size of the room (i.e., the larger the room, the harder it is to get low extension, especially at high output). So I can’t help but think that something is wrong somewhere. Something is limiting extension – perhaps electronically – or else something is wrong with the measurement device.

Regards,
Wayne


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## shinksma (Aug 12, 2010)

Wayne A. Pflughaupt said:


> Looks like corner placement and re-locating the front row did the trick; this response is “equalizable.”
> 
> However, I’m at a loss as to what’s causing the poor extension. Everything I can find on your Epik tells me it should have strong output all the way down to and below 20 Hz. A poor room will affect the overall response – e.g. sharp nulls that can’t be fixed – but a poor room should have no affect on extension. That’s typically a function of the sub’s capabilities, or the size of the room (i.e., the larger the room, the harder it is to get low extension, especially at high output). So I can’t help but think that something is wrong somewhere. Something is limiting extension – perhaps electronically – or else something is wrong with the measurement device.
> 
> ...


Yeah, the response below 25hz seems like something I can feel when I watch a movie with known low bass, but I'm not a calibrated mic/meter. On the other hand, maybe my RadioShack SPL is out to lunch. I suppose I could return it and try another, or I could just not bother with trying to "fix" the low end measurements (since there is nothing I can do about it anyway), and just focus on the 30-100 Hz region.

I do have a fairly big room (20ft x 20ft or so, 9ft ceiling I think, although could be 8ft...). But I don't think it is so large as to be sucking that much energy out of the low-end. Curiouser and curiouser, said Alice...

I'll play with my overall system on the weekend low-end-reponse-wise (it may be that my sound card - a Delta1010 - is goofing with something, and I have a couple of vocal mikes [Beta58, SM58] I could try as a rough comparison to the RS SPL).

So, now I get to place an order for a BFD. I know the 1124 is sufficient for my needs, but the 2496 may be worth expending, since if I remove it from the HT system I can throw it in my guitar/vocal effects rack. Any opinions? (Yeah, I'll now go check the BFD subforum...)

shinksma


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## Wayne A. Pflughaupt (Apr 13, 2006)

> I do have a fairly big room (20ft x 20ft or so, 9ft ceiling I think, although could be 8ft...). But I don't think it is so large as to be sucking that much energy out of the low-end.


Not likely. My room’s three times the cu. ft. yours is, and my subs probably aren’t as good as yours, and I get down to 20 Hz.

What you might try doing is going to the BFD Guide. There’s a link for downloading sine waves. Download maybe every other frequency from about 15 Hz up to 35-40 Hz, burn them to a disc, and play it back on your system, starting with the lowest frequency. At first you’ll probably see a lot of cone movement but not hear of feel much. But when the sub “kicks in” you’ll know it. That should give you a seat-of-the-pants idea how low your sub is going.

Regards,
Wayne


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## electrostat (Feb 16, 2010)

Epik will not publish response curves for their subs. But they do say "Frequency response : 20-300 Hz +/-3.5 dB anechoic, 15 Hz or lower in-room extension." Without the baseline curve you are flying blind as to what the sub is doing before it meets your room. Also the term"15 Hz or lower in-room extension" is interesting. I would guess that in-room extension means that for complicated reasons if a room can hold the spl of the transducer without unequal dissipation or absorption, a virtual boundary effect may occur. Well that stuff is way beyond me. (If someone out there can explain the "virtual boundary effect" please do) They say 20-150 +- 3.5db- so worst case the lowest note it will play is 23.5hz -and best would be 16.5. If the sub will not play down to 23.5hz then it is a lemon and send it back because it is out of speck. I would do the suggested tone files and see if that hold any clues. When playing one tone at a time you can walk around the room and find the HQ resonance fields for that tone, as well as the dead spots for a particular tone. Some of the freq. might even cancel themselves mostly away. The Sub should play to 25hz no problem according to their specks. I would imagine that 20hz is about the most you should expect from it. Big and Powerful does not guarantee the lowest tones it just makes them more probable. Here is a test for you: play a 15hz tone and walk around the room and find the spot where you get that shiver in your liver, if that spot is not there it does not play that low..

cheers


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## electrostat (Feb 16, 2010)

Oh on another tangent, how would you describ its timber, dry-wet-punchy-open? How is its Attack, analytical, punchy, smooth, fast? Any way I am curios about your thoughts on the quality of note it plays as well. I bet it does sing. lots of Subs get muddy when they play above 100hz or loose below 40hz. How well does yours do?


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## shinksma (Aug 12, 2010)

Well well well, what an interesting revelation. I downloaded and played the sine waves (as mp3 directly from my laptop) straight into the SW. The SW driver cone responds well visually and via touch from 35 Hz down to 20 Hz and below. So the SW is doing what it should/can.

But in the room, once I got below 28 Hz or so, the "sound" and feel just started to fade. By 25 Hz it was clearly fading, and by 20Hz it was so anemic as to almost be non-existent. The SPL meter confirmed this. Typically flat from 35 Hz to 30 Hz, down 8 dB from 30Hz to 25Hz, and down another 10 or more at 20Hz. I could sense the walls pulsing and absorbing the energy from the SW.

As an experiment, I moved the SW to sit exactly behind the main listening position. Response was less overall, but not otherwise different in nature: at 30-35Hz was fine, but faded at 25Hz and below. Just like the corner position.

So clearly it is the room. Somehow the way the room's construction absorbs the energy at and below 25Hz very effectively. The room is a bonus room over a two car garage. I have area rugs over the windows to act as very simple sound absorption (initially for taming feedback/reverb of my guitars/vocals) and to block the light so I can use the PJ all day. The floor is carpeted in a "short-shag" carpet (dunno the official term). The interior walls are drywall. I am unsure of the interior wall structure: I believe it is 2x4 wood frame. Exterior is a wood paneling surface with sealant and paint. I doubt there is very much if any insulation in the walls. A typical second story in Florida. (First floor is stucco over concrete block, in comparison.)

So...what do I do about a room that simply wants to absorb all that low-bass energy? Are there anti-bass-traps I can install?

Hmm, I can't believe this is the problem I now face. I was expecting to have to tame room response, not try to encourage it...

shinksma


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## electrostat (Feb 16, 2010)

Sounds like its time for some shakers. Cone drivers do have limitations at low hz say 22hz. Air is a medium to cary a wave on and lower waves mean more friction means more power needed to produce that wave. slight phase problems mean big losses. try to find some full scale tone files before you get to crazy. But even the big JBL 1500 array Sub only goes flat to 25hz. it is a 1000w 15in style transducer way beyond my pocket book, the big dog klipsch p-312W goes to 18hz but maximum output is reached a 30hz. So if you are getting 25hz from a mp3 trough a pc as a trasport standing ovation!!!!! In some movie theaters they used to use these strange bladed fan transducer they called a rotary woofer, maybe they still use them, but these can produce waves as big as 8hz, if you want to go below 20hz with any reliability you will have to use shakers to get the effect, or a rotary woofer to get the actual wave. it is very unlikely that you house is able to dissipate that kind of energy, and it may be that there is a massive muti-tonal notch effect going on, but what do you do to solve that? It might mean that the room holds/resonates tones well down to 25hz and after that the wave just blasts through the walls. Interesting thought. the only way to stop some of that loss would be more layers of sheet rock. jibcrete the floor, but then you have increased the reflective nature of the room and will need serious treatments to del with a more lively room. To absorb subsonic waves it takes thick dense open porous material that break sound energy down into heat/thermodynamics/. My bet is that no mater what you do the sub will play down to about 25hz and then start dropping off. That makes it allot like other great Subs. I want to know how it sounds with a movie playing? I have seen some pretty smooth room responses from rooms that to me sounded totally unnatural so my advise is to get the mains tamed a bit and start listening.


Cheers


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## shinksma (Aug 12, 2010)

The Empire sounds pretty good (especially compared with what I had before). I do sense the peaks in the response, especially the one at 55Hz, and I also notice the lack of real oomph below 25-30 Hz or so.

Since many other folks have successfully implemented a flat response to 20Hz or below using cone-driven subwoofers, I have to believe that my situation is purely room-related. (As I mentioned, the cones have very consistent X-dev, observed visually and via touch, down to 20Hz.)

The feeling I get in the room with the frequencies <25Hz are analogous to noise-reduction/cancelling headphones: you can sort of sense the outside sound, but the meat of it has been sucked away. Except that I don't actually want that effect, obviously, whereas it is desireable in the NR headphones.

My room is not the typical basement, so I suspect my situation is not as common as other room problems described here at HT Shack and elsewhere. So if anyone has any suggestions (other than re-construct the walls/floors  ) then I'm all ears.

shinksma


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## electrostat (Feb 16, 2010)

Parametric EQ


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## Wayne A. Pflughaupt (Apr 13, 2006)

> I downloaded and played the sine waves (as mp3 directly from my laptop) straight into the SW. The SW driver cone responds well visually and via touch from 35 Hz down to 20 Hz and below. So the SW is doing what it should/can.


 Probably not the best way to accomplish the experiment, unless you’re certain your soundcard has flat response to 20 Hz.

Most rooms with symmetrical boundaries have a bass “dead zone” in the center of the room, that decreases as you move from the center towards a boundary. Try taking readings near a wall to see of extension is any better.

Regards,
Wayne


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## Wayne A. Pflughaupt (Apr 13, 2006)

> Since many other folks have successfully implemented a flat response to 20Hz or below using cone-driven subwoofers, I have to believe that my situation is purely room-related. (As I mentioned, the cones have very consistent X-dev, observed visually and via touch, down to 20Hz.)


That really doesn’t mean anything. The cone will move regardless of whether or not there is any legitimate “output.” Try something like a 5 Hz tone and you’ll get the same thing.

Regards,
Wayne


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## Wayne A. Pflughaupt (Apr 13, 2006)

> So if anyone has any suggestions (other than re-construct the walls/floors ) then I'm all ears.


 You might try testing the sub in some other room, at a friend’s house, etc. to see what you get.

Regards,
Wayne


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## shinksma (Aug 12, 2010)

Wayne A. Pflughaupt said:


> Probably not the best way to accomplish the experiment, unless you’re certain your soundcard has flat response to 20 Hz.
> 
> Most rooms with symmetrical boundaries have a bass “dead zone” in the center of the room, that decreases as you move from the center towards a boundary. Try taking readings near a wall to see of extension is any better.
> 
> ...


I agree that the visual/touch test is not the most scientific, but it was sufficient for me to be assured the SW cones weren't just "dying" at those low frequencies. I could feel the wall moving but not actually feel the impact personally which matched the SPL meter's response. Some recent reading has led me to believe that the walls are having a diaphrammatic effect on the very low bass response - i.e. acting like a paper bag instead of a concrete wall. 

I'll re-check my laptop soundcard's response, but I'm pretty sure it is flat enough (within a dB) to 20Hz. Certainly not bad enough to cause the results I'm measuring.

My experiment with sinewaves was done in the corner, near the SW, placing the SPL meter in various positions, including near the wall. All positions showed anemic results once the frequencies dropped through 25 Hz.

If my walls really are a major factor in this issue, I won't be able to fix it very easily - I'm not about to add another layer of drywall. I'll experiment with a few things and see if I can improve the results.

The only other thing I can think of is there is something wrong with the SW itself. But since the response above 25 hz seem so expected for the room, I can't imagine a failure or issue that might cause the symptoms I'm experiencing.

I will try the SW in another room, though. The thing is a beast - not exactly easy to just lift and carry downstairs. And I tend to do all this stuff on my own - no help. Maybe I can ask a friend or neighbor to assist...

shinksma


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## shinksma (Aug 12, 2010)

OK, here is the news:

Moved the SW downstairs to the "dining room" (empty), which has wood floor over concrete, and drywall on wood frame with concrete block outside wall. Room is about 1/2 the size of my music room: 12ft x 18ft x 9.5ft, with one regular doorway-sized opening on one end wall and one large 7' wide opening on one side wall. Doorway was open during measurements. Other big opening always open.

Quick measurements using laptop sinewaves straight into SW and using an SPL meter gave 92dB at 35Hz, 83dB at 30Hz, 85dB at 25Hz, and 82dB at 20Hz. Dropped to 73dB at 18Hz, 63dB at 15Hz.

So clearly the roughly flat to the 20Hz drop-off is how this SW will work in the right room. Seems to be a slight room peak at 25Hz and/or a slight null at 30Hz, but much better response than upstairs. 

So it's just that my bonus room is not the right room.

Sigh...now what?

shinksma


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## electrostat (Feb 16, 2010)

trying the sub in another room still does not give absolute scientific results.your dining room may have a 25hz peaky-ness leading you to believe that it is the sub is not the problem. You have to measure the sub in a truly non-res environment to know what it is. If you had access to a sub that was true to say 15hz in anechoic then played it in you theater well you would be much closer to the solution. I discussed this with a college of mine who has multiple calibration certs from Integra, JBL, B&W, Alpine..... and has been in the business for a long time. He has found that very few subs play as low they say they do in a home/car. And many issues come into play, in a engineering environment they use amps and source gear with S/N way down to say 128db, well out of the range of most consumer gear. Also if you look at the actual DAC chip most only play notes 20hz-22khz. Also it is difficult to find a class D that plays below 20hz for any price. So that is a real limitation on moving lower. But back to your room, would you consider heavier sheet rock on two walls? If you double rocked a corner then the sub would have a better chance at coupling with the air at that point and thus radiating it into the room? I feel that you need to apply some eq (50hz), tame the mains and just live with it for a while. You might have a good thing going just as it is, any big change seems like it will cost some real $$. You have a great sub, and your room has limits, parametric eq could help a bunch but the$$$$, Play some movies just listening might reveal some solutions as well. I hope you keep us posted.

cheers

I wish I had a silver bullet for you,


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## shinksma (Aug 12, 2010)

OK, here's a new measurement from a different LP (left front chair instead of center or "just left of center").

I placed the SW back in the bonus room, just left of the Ctr Ch (I think in the exact same spot I have tried before), placed "sideways": one driver facing me, the other facing the wall.

The raw results are a little awful, but by doing a series of cuts beyond the ones automatically found, adjusting width and value of all, and adding one small boost, I think it is much more tame "in theory".

Lacking a BFD I can't actually try the filter settings.

I was going to order one, but hadn't decided on whether 1124 or 2496. I think I'll go for the 1124 - that was the model I selected for deriving filters, and it seemed to have the amount of control I needed.

Your comments are welcome of course.

Now to go place an order and wait for delivery...

shinksma


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## electrostat (Feb 16, 2010)

Is the orange line the curve you expect after the BFD?


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## electrostat (Feb 16, 2010)

sorry i meant orange dotted line


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## Wayne A. Pflughaupt (Apr 13, 2006)

What is the current gain setting on the sub? That’s some severe equalizing you’re looking at, you’re going to have to have plenty of headroom to pull it off.

Regards,
Wayne


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## shinksma (Aug 12, 2010)

electrostat: yes, the orange dotted line is the predicted response after filtering.

Wayne: my SW is currently set at a gain of 0.5 out of one: i.e. at 12 o'clock on the dial. I think I have enough headroom - depends on whether the BFD affects overall gain: I believe I can adjust the output of the BFD too. If not, I'll consider re-doing the curves, but man, eventually I just have to dial something in and relax and enjoy.

Yes, the cuts are severe, but this seems to be the only way to preserve any low-end response. The SW locations where the low end doesn't get the life sucked out of it is also the locations where overall response is very peak-valley.

Now, once I implement the filters and take a real-world measurement it will be interesting to see how well the predicted response is matched.

It appears DSP1124s are on backorder everywhere that I would shop online. Very annoying...

shinksma


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## Wayne A. Pflughaupt (Apr 13, 2006)

> Wayne: my SW is currently set at a gain of 0.5 out of one: i.e. at 12 o'clock on the dial. I think I have enough headroom - depends on whether the BFD affects overall gain: I believe I can adjust the output of the BFD too.


The BFD affects overall gain relevant to the filtering (boosts or cuts, overall) you employ. So eliminating that 55 Hz peak means you’ll loose about 15 dB of output. That will have to be “made up” by increasing the sub’s gain. Otherwise it’s probably going to sound like your sub sounds weak relative to the main channels. You may end up with the sub maxed out and not able to “keep up” during demanding scenes – i.e., clipping, bottoming out, etc. 

But we’ll know for sure after you get the BFD.

Regards,
Wayne


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## shinksma (Aug 12, 2010)

I found a DSP1124 today at a local guitar store. So I should be able to hook it up tonight. Also got a midi cable (my soundcard has midi too).

I mis-typed earlier about adjusting the gain/output of the BFD. I meant that by using the 1124 inline, perhaps by adjusting my AVR output as described in the guide (occasional red LEDs OK, keep it mostly yellow and green) it might result in sufficient increase in the input to balance what I lose in the filtering.

And I'm willing to try other filtering techniques. One thing I have been avoiding, obviously, is boosting frequencies in REW as suggested in the REW guide. But maybe I can be a bit more aggressive and then I wouldn't need such drastic cuts. Meh, I guess we'll see...

shinksma
_Posted via Mobile Device_


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## Wayne A. Pflughaupt (Apr 13, 2006)

You have to make up for gain loss due to equalization _after_ the equalizer. I can’t be re-claimed at the inputs.

In any event - the gain changes have to do with the input signal, and have nothing to do with headroom. Headroom is the real issue with equalization – i.e. what the subwoofer amplifier and driver can reasonably handle – not the strength of the input signal.

BTW, the directions in the Guide for setting levels for the BFD are incorrect. In truth, setting input levels for 24-bit processors is virtually a non issue, information that’s easily found on any pro audio forum or perusing the manuals of said processors. 

Manufacturers that do make a recommendation for input levels recommend leaving about 10-12 dB headroom. Headroom is important with DVDs because you never know what a movie is going to dish out. To arbitrarily pick something off your shelf as “the standard” and expect that nothing more demanding will ever come down the pikes is foolish. 

There is only 1/10 of a volt between the point where the BFD’s red LED’s light up and clipping actually begins, so you want to stay out of the red. It makes more sense to set the input in the -10 dB range.



> And I'm willing to try other filtering techniques. One thing I have been avoiding, obviously, is boosting frequencies in REW as suggested in the REW guide.


That recommendation is made on the premise that boosted filters increase ringing (aka the signal decay times of low frequencies). That’s true, but I have my doubts that increased ringing from a filter will actually overwhelm the natural ringing you’re already getting from the room. So IMO it’s not an issue to worry about, by and large.

Regards,
Wayne


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## shinksma (Aug 12, 2010)

First attempt at taming the room is attached. I'm fairly happy with the overall sound so far - I'm going to watch a couple movies of course to feel it in action.

I'll play around a bit, try doing the filters without as much overall cut by boosting a little more in other spots, but that will be tomorrow. Tonight, I actually use the system for which it is intended: watch a movie!

Thanks for all the tips, 

shinksma


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## electrostat (Feb 16, 2010)

as you increase gain you also raise the noise floor.


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## shinksma (Aug 12, 2010)

OK, one last graph for tonight. Adjusted the filters so there was less cut overall, and had to boost in some areas to compensate. Not ideal, but a lot better than what the room was like prior to REW and a BFD.

Part of the increased dBs is from the new filters, and a little bit of additional gain on the SW itself (I didn't adjust it back fully after the movie).

That peak-valley at 46-50Hz is a little annoying, but I can live with it. Not saying I won't try to massage it out, though... 

But I'm really happy with my low-end response now. So this trial-and-error thing was well worth it.

shinksma


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## shinksma (Aug 12, 2010)

shinksma said:


> And I'm willing to try other filtering techniques. One thing I have been avoiding, obviously, is boosting frequencies in REW as suggested in the REW guide. But maybe I can be a bit more aggressive and then I wouldn't need such drastic cuts.





Wayne A. Pflughaupt said:


> That recommendation is made on the premise that boosted filters increase ringing (aka the signal decay times of low frequencies). That’s true, but I have my doubts that increased ringing from a filter will actually overwhelm the natural ringing you’re already getting from the room. So IMO it’s not an issue to worry about, by and large.


I thought I also read that if too many boosts are made, the BFD can clip digitally (run out of mathematical headroom), which is just as bad as clipping the input signal. Nonetheless, the boosts I made seem to have not had any noticeably detrimental effects, and have meant that my cuts did not have to be so drastic, as hoped.

As a result, the Epik Empire sounds very nice now. "Clean, not muddy, fast" might be some typical terms I would use. (Peppery, hint of lime, and slightly bitter would not be terms I would use, for example. ) I just finished listening to some loud angry music by a band called Buried Inside (Wikipedia classifies the music as "Metalcore, post-hardcore, atmospheric sludge metal"). Lots of low bass (the sludge metal part), which did not muddify as can happen: the ultra-low notes were strong but not buzzing so much it drowned out the rest of the music. So my current EQ certainly works well on that type of music. Now to try out some other music...

Thanks folks for your help and suggestions. I still get jealous when I see other people's non-EQed room measurements and they are so much better than my raw measurements, with natural room extension and only a few peaks/valleys. This room has been a real challenge. I thought it would be a case of do a few measurements, have a nice roll-off below 20Hz with some room extension, adjust three or four filters for some peaks between 40 and 80 Hz, and be done. Instead I feel like I'm torturing the audio as it goes to the SW with the 12 filters pushing and pulling. Yes, I used all 12 filters. Youch.

shinksma


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## electrostat (Feb 16, 2010)

How much has your THD sufferd? THe graph looks nice but does it hold at varied db?


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## shinksma (Aug 12, 2010)

electrostat said:


> How much has your THD sufferd? THe graph looks nice but does it hold at varied db?


Well, I can't say I can accurately measure THD with my ears, but listening at high SPLs today with music I am very familiar with leads me to believe that I haven't degraded the quality significantly.

Is there anything I can do with REW that would indicate impact to THD?

I'll be having a go with a loud-explosions movie of some type or another later today :gulp: , but since explosions are full of brash sound I'm not sure that will indicate anything.

shinksma


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## Wayne A. Pflughaupt (Apr 13, 2006)

> I thought I also read that if too many boosts are made, the BFD can clip digitally (run out of mathematical headroom), which is just as bad as clipping the input signal.


This is true. However, the BFD’s meter in its normal mode reflects the results of equalization, although perhaps not 100% accurately.

Regards,
Wayne


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## JohnM (Apr 11, 2006)

You could use REW's RTA and the sine wave generator to see the distortion levels of pure tones.


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## paulspencer (May 11, 2007)

Regarding the issues with low end gain, you can't easily judge that kind of thing subjectively. If you want to be sure what is going on then it's quite simple with a calibrated mic (not a generic file but a studio calibrated one like those from Cross Spectrum) and a nearfield measurement where you place the mic as close as possible to the cone. Then you see the sub only response which looks very much like an anechoic or ground plane measurement. If you want you can actually calculate the room transfer function, but it's a bit tedious. 

Your raw charts look pretty good actually. Try dealing with a 40 db range! Especially where you have big dips. 

Also you have to consider room construction. An upper level room with light construction, with a timber floor, lots of windows, no bricks or concrete but light cladding - such a room is like one big bass trap, leaking bass. That makes your room fairly tame without much room gain down low.


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## shinksma (Aug 12, 2010)

paulspencer said:


> Also you have to consider room construction. An upper level room with light construction, with a timber floor, lots of windows, no bricks or concrete but light cladding - such a room is like one big bass trap, leaking bass. That makes your room fairly tame without much room gain down low.


Yeah, I realize that now. I just kept reading about room gain and seeing some raw graphs that obviously had good non-EQed ultra-low-end response, and at first I thought Something Major Was Wrong with my room/equipment. But know I recognize that the room's construction is exactly the opposite of many typical HTs, which are located in the basement of homes with nice solid walls, floors and a ceiling that is a floor to the furniture above.

Watched Troy (Brad Pitt etc) over the last couple of nights - the room did not have that boomy characteristic it had before REW/BFD, and the explosions and other "LFE" stuff seemed more natural sounding. So I think it is dialed in pretty good for now. I expect over the next six months I'll be re-measuring and tweaking just for giggles.

shinksma


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## paulspencer (May 11, 2007)

Think of it this way - you got free huge bass traps! The downside with the lossy room (apart from neighbours at the door) is in the bottom octave you have to work much harder. With a garage below you could build a tapped horn perhaps if you can find a bit of space down there. I'm planning a similar thing where sims show 95 db efficiency at 20 Hz! In my case it goes under floor.


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## shinksma (Aug 12, 2010)

I was reading Wayne's post (http://www.hometheatershack.com/for...target-levels-hard-knee-house-curve-long.html) about using fewer filters to get a more natural-sounding response. I decided to give it a go: I had used all 12 (!) of the 1124 to get the results I previously posted.

Attached is the the latest attempt, using only six filters. I might try to tweak it a bit to pull down the response above 70 Hz, but I know the more I do that, the more filters I'll probably need. I couldn't get a response that I was happy with without using six filters: too many peaks and valleys in my raw response.

I also need to give this a good listen through with material I am very familiar with, and compare to my previous 12-filter version. That will be the real test. 

And Wayne: thanks for the excellent technical posts. Very good reading.

shinksma


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## paulspencer (May 11, 2007)

shrinksma, 

You might like to try this - plot both responses then apply 1/3 octave smoothing. You will then see something that looks like what you hear. Not a bad idea to do this with final results as a reminder that our eyes are fussier than our ears.


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## Wayne A. Pflughaupt (Apr 13, 2006)

Thanks for the kind words, shinksma. :T Keep in mind that filters that are ultra-narrow or only a dB or two are most likely inaudible. As Paul noted, response doesn’t have to look picture-perfect to sound good.

Regards,
Wayne


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## shinksma (Aug 12, 2010)

Yeah, I made sure to use filters that had some width to them - the one-note notch filters would not be very useful, I must concur. And any filter that was 2 dB or less I just discarded.

shinksma


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## shinksma (Aug 12, 2010)

So I've been enjoying my Empire with the EQ getting tweaked a little here and there for about a month now. But on the weekend I picked up a second one in essentially new condition, since I was yearning for a bit more kick and headroom. (Sorry for dredging up an old-ish thread.)

Placed them equidistant to each other and the side walls across the front of the room, with drivers facing each other and the walls. Did a quick listen with current EQ, decided that was not very satisfactory, so in about 5 minutes I had a new unfiltered measurement, a set of filters defined to get a flat response to 20Hz, and the filters loaded and running. The measured results are below (and that's not even 1/3 octave smoothed). It is so well integrated now - slams when it should, and does not seem overly boomy when not needed. I thought it was great with one, but with two...wow.

The only thing that might be better would be adding dual TCA 18.2s or Seaton Submersives in the rear corners. Just to see if I can achieve ultra-low bass extension down to 10 Hz or something.

Hmm, I try to believe I'm just kidding, but check with me in a year or so... :gulp:

shinksma


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