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Post by digitalchris on Sept 26, 2012 16:24:46 GMT -7
I want to know what kind of SPL you guys are hitting in order to get a feel for what the IB setup can do. I'll go into details in a min but at a confortable "loud" level in my theater and with the IB's level matched to my mains, I feel nothing below 20hz and I'm just not hearing/feeling what the IB is all about. Even if I crank up the subwoofer level in the AVR 4-5 db, I only get a very minor change in the lower LFE, never mind the ULF. Whats up? Here is my most recent set of graphs, it's of the front and rear row overlaid. You'll also notice that the LF department is a good 5db higher overall than the upper freq (100hz and up). Am I confused for a good reason?  Just a few side notes... (4) IB18's, single 2 ohm each, line array lower front wall EP4000 amp, running all 4 drivers on one channel wired to 2ohms. Marantz SR5005 AVR   |
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Post by ThomasW on Sept 27, 2012 6:55:08 GMT -7
I never participated in the car audio world of dB drag racing, so I've never measured my system for max output.
That said ......
The bass output is high enough that waves of bass radiate through the floor when there's really low bass in the recording. My IB has much less swept volume compared to your 4-18"
I'm not sure what you think the IB experience is. The idea is the best quality bass, something subtle that doesn't call attention to itself until the very low notes are played, then the earth rumbles/the IB roars. If your ultimate goal is mind numbing, brain cell melting output levels all the time (think Korn concert) you'd be better off building horn subs.
FWIW as I posted previously, not a good idea to run the Behringer amps with a 2 ohm load. Eventually they just melt down. That's why a long time ago I suggested you run 2-4 ohm loads
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Post by digitalchris on Sept 27, 2012 15:28:27 GMT -7
Good answer. To be fair, I was previously running (2) 4ohm loads by having a pair of 18's on each channel, but since I added the 2 15's to the mix to help flatten out the response curve, I put the 15's on one channel of the EP4000 and wired all 4 IB's to the other channel. I have no problem finding another amp down the road just for the 15's so this is kind of a test-n-tune setup for now. And no, I'm definitely not looking for db drag racing type bass, I don't want my vision blurred, I don't want my chairs to feel like a gigantic vibrator and I don't need my chest punched every time a gun goes off in a action movie but what I do want and why I built the IB is to feel the ULF stuff which I have yet to feel. So, with that said, I'm curious as to how hot you guys are running your subs and how high of a overall volume you listen at to put a smile on your face and be glad you went with IB in the first place  And maybe it's because I havent played around with too many home audio subs before the IB but I still don't hear this squeaky clean bass... I mean, it sounds good I guess, but I'm thinking that maybe my room is the factor or something is wrong in the setup but I've double checked my wiring, no funky setting are in play, I just don't get it People always rave on how awesome is and how their IB moves the couch because it has soo much low output but I have no idea how they are getting to that point!!  BTW, could it be a house curve by chance, to get the ULF higher up the scale? |
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Post by ThomasW on Sept 27, 2012 16:28:21 GMT -7
If you have 2 MFM-15's in the back of the HT, and have the master bass level adjusted so they are balancing everything out, the amount of output from the front 18"s must be ~80% or more choked off.
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Post by digitalchris on Sept 27, 2012 16:56:39 GMT -7
Say what?!  I'm confused... Without the MFW's connected, I have the gain on the sub amp turned up so I get 75db on the SPL meter from the IB's, then I connect the MFW's and disconnect the IB's and turn up that channel to get 75db on the spl meter, that way both the IB's and the MFW's are level matched. Actually, the MFW's had to be turned up 4-5db more to get the response graph as flat as it is right now. But I'm still confused about your last post.... "and have the master bass level adjusted so they are balancing everything out" and then "the amount of output from the front 18"s must be ~80% or more choked off", meaning I need to choke off my IB's down to 20% of their current output? |
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Post by ThomasW on Sept 27, 2012 18:19:55 GMT -7
meaning I need to choke off my IB's down to 20% of their current output? Nope you already have them choked off that much Having front and back set to 75dB is meaningless Why? 2 MFM-15's can move approx 1 liter of air each, each Fi 18" can move 7+ liters of air. This means if the bass output between the front and back drivers is balanced (your 75dB) and you turn the system up to normal movie SPL's, the MFM drivers will run out of gas while the Fi 18"s are barely off idle..... |
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Post by digitalchris on Sept 27, 2012 19:19:24 GMT -7
Ahhh, well written answer and it makes sense seing that when I do play a movie, I notice by actually watching the drivers that the IB's are barely moving.. I kind of thought that's what you meant anwyay but was confused because it still leaves one question...
How do I "unleash the power" of the IB's? When I wasn't running the MFW's, I still had the "lack of ULF" coming from the IB's... What am I doing wrong? I thought that generally, you level match your subs to the mains and then turn them up a bit more from there if desired.
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Post by ThomasW on Sept 28, 2012 7:48:02 GMT -7
When I wasn't running the MFW's, I still had the "lack of ULF" coming from the IB's... This statement is illogical. The frequency response of the IB remains the same regardless of whether the MFW units are running or not. Did you do a nearfield measurement of one of the 18"s? Turn off/disable/remove all EQ and any other devices in the signal path between the AVR sub out and the EP4000. Place the meter 1.5" in front of one woofer's dust cap and do a sweep. Yes it's ok if the other drivers are operating. That measurement will tell you what frequencies the drivers themselves are reproducing without the effects of the room. |
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danny
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Post by danny on Sept 29, 2012 0:59:23 GMT -7
Check your surround modes and channel gains in the marantz. For 2 channel input, only M-Channel music and M- channel movie send anything out the LFE output.
For the surround modes with actual mulichannel input from a dvd, there is more than one spot for channel gains. In the speaker menu and the surround mode menu there are settings that can really attenuate the lfe. - this was the case with my Sr8001. Yours likely is similar.
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Post by digitalchris on Sept 29, 2012 17:41:23 GMT -7
Yes Thomas, I realize that comment made no sense but what it meant was even when I had only the IB's level matched, I still felt no ULF. My reason for asking that related to the main question in the post... how to I get the IB's to move some air? Crank up the volume to retarded levels? Dial up the "sub" level in the AVR? Sure, all of this will excite the ULF stuff more but also add to the mid bass which is what I don't want.
I'll take a peak at those settings danny and let you know what I find.
Another question has come to mind after having a local enthusiast come visit... Could my laptop, while going through a RCA input on the receiver rather than HDMI, be putting out the correct signal while the HDMI's are not? I know that sounds silly, but it could be the reason why my graphs look great but I hear no ULF when playing movies through a HDMI capable player.
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Post by jman on Sept 30, 2012 18:42:22 GMT -7
Your original question is "how much is enough".
So, what spl peaks are you seeing? For me, I hit around 110-120db peaks on movies with quad 18's. That's enough for me and at those levels my ceiling is shaking (floor is concrete).
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Post by digitalchris on Sept 30, 2012 20:12:41 GMT -7
Bass peaks of 105db during transformers, average overall soundtrack during action scenes is around 95db.
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Post by jman on Sept 30, 2012 21:29:32 GMT -7
105db is at least 10db under reference, which isn't very loud. Many people run their LFE "hot" by 3-8db so that they get the impact of what the bass is like at reference but without running the entire system that loudly.
To really get impact you need to listen at or near reference level. Can your system handle reference? Your IB can but your other speakers might not have the guts. Also, if your room is untreated, even if your speakers are up to the task, the reflections will make it so harsh that nobody will want to be in there when it gets loud.
Bass will never have much impact unless it's at a high enough level.
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Post by digitalchris on Oct 1, 2012 6:09:18 GMT -7
Alright, so maybe my system is just fine and it's my room that's keeping me from turning it up in order to experience the IB's  |
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Post by ThomasW on Oct 1, 2012 8:56:11 GMT -7
It's a pretty safe bet the room dimension and the placement of the subs are what's causing the problem, along with running way to high a crossover point, (think 60-80Hz instead of 120Hz)
You'll have a definitive answer when you compare a nearfield measurement to one from the listening position.
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Post by gworrel on Oct 1, 2012 12:03:44 GMT -7
I have been seeing many mentions of "reference level" in my reading recently so I looked it up. According to THX, "THX Certified Receivers reproduce studio Reference Level, 85dB SPL with 20dB of headroom." So, by that standard, 105dB would be a top peak at reference level. Is there some other standard? I checked the other night while watching a movie and the average level was about 80dB which sounded loud to me. I have very little in the way of acoustic treatment so maybe that is why. I don't yet have an infinite baffle, but I recently moved my Velodyne 18" sub to the basement theater room from my living room and some of the earthquake-like effects are gone. Probably due to a combination of a bigger room and cement floor instead of the wood floor that no doubt acted like a giant bass shaker. By the way, I was watching Megamind, which I found very entertaining, and there is an explosion where Megamind blows up the "good" hero which definitely plumbs the bass depths. www.thx.com/consumer/thx-technology/thx-reference-level/ |
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Post by FOH on Oct 1, 2012 14:24:30 GMT -7
The LFE spec, due to the extra demand placed on the channel for huge effects etc., requires an additional cal setting of +10dB, thus the 115dB for subs.
In bass managed use use, the redirected bass can add even more to where a calibrated flat system can hit 120dB plus @ the LP.
Then add the house curve to taste. Different rooms need differing amounts due to decay time in my experience.
My 2 cents, .... further thoughts? Thomas, Chris?
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Post by digitalchris on Oct 1, 2012 17:20:27 GMT -7
The LFE spec, due to the extra demand placed on the channel for huge effects etc., requires an additional cal setting of +10dB, thus the 115dB for subs. I'm a little confused FOH, are you saying that the +10 needs to be added by me and it's not already mixed in? I thought it was already mixed into the soundtrack. In bass managed use use, the redirected bass can add even more to where a calibrated flat system can hit 120dB plus @ the LP. I'm not sure what you mean by this. Then add the house curve to taste. Different rooms need differing amounts due to decay time in my experience. I was thinking that the other day, maybe I can add a house curve way down low to excite the ULF's, bad idea? Also, notice in my full range graph, the sub 100hz stuff is already a good 5-10 db above the rest of the graph, odd that I still feel like not much bass is present? But again, could it be reflections making the room sound louder than it is in the upper frequencies which is holding me back from turning the whole system up to experience the IB's? I feel like that's not the case though seing that everybody that raves about the IB's are most likely not treated, being living rooms and all. IDK |
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Post by digitalchris on Oct 1, 2012 18:50:16 GMT -7
Here is a graph of one IB driver with the mic 1.5" from the dust cap...  |
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Post by jman on Oct 1, 2012 19:28:11 GMT -7
That's not the curve we were expecting for nearfield measurement. Have you checked the driver wiring with a battery to make sure they are all in phase?
As to the +10db on LFE, that is "builtin" to the mix. Our hearing needs more volume in the low end to perceive it as loudly as higher frequencies. Without that extra 10db of headroom, the mixing engineer wouldn't be able to get the impact desired relative to the other speakers. Or they would have to cut all the other channels by 10db, which basically does the same thing. It just allows for louder signals to be sent to the LFE channel.
You will find that as you raise the master volume, the perception of bass will increase exponentially.
At say 105db peaks you get a little rumble. 110db is starting to get interesting. 115db is starting to get scary. Then from there even each step up of 2-3db is significantly stronger. At 120db your walls/floor/ceiling will be pulsating. You will feel air on your pant legs, your shins might feel vibration, your chest cavity will resonate (more in midbass 50-100hz). Basically 105db doesn't do anything, and 120db can be downright scary/fun. Just watchout for any signs of your ears feeling strained or "hot". That could be an indicator that the volume is too loud for too long.
Maybe I should post a video of my IB playing the last scene of Pulse ;D
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