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4 18s wont do it, I have 4 and 2000W and I can not get 125dB, although my room is HUGE (20000+ cubic feet).



what is average size? Room gain might get you there....


I would get 8 to be sure and power them with 6000+ watts




btw, have you been on the IB cult site to ask the same question?
 

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Well he said average sized living room, so I was thinking of something normal - not a house plan penn. =P Mighty big living room.


I'm thinking with "average" (whatever that is) room gain, 4 18's in an IB at full throw could do it. But it might take 8, it all depends.
 

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Discussion Starter · #6 ·

Quote:
Originally Posted by penngray /forum/post/14172144


4 18s wont do it, I have 4 and 2000W and I can not get 125dB, although my room is HUGE (20000+ cubic feet).



what is average size? Room gain might get you there....


I would get 8 to be sure and power them with 6000+ watts




btw, have you been on the IB cult site to ask the same question?


Haven't been to the cult yet.


What kind of numbers are you getting with your 4 18s?
 

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One of those fan subs?
 

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Depending on how much room gain you have. 16 FI IB18"s would be needed, if you only have 14db room gian, 8 if you have 20db room gain, 4 you would need 26db room gian which might be pushing it. The best way to figure it out would be to take a sealed box subwoofer that at a certian displacment should be giving you XXdb's put it where the IB outlet will be and see how many db's you accualy get, then you can determin how many you need. Or better yet get one IB driver biuld put it in and see how much output you get, then double the number of drivers for every 6db more you need.
 

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Quote:
Originally Posted by Funky Waves /forum/post/14172223


Depending on how much room gain you have. 16 FI IB18"s would be needed, if you only have 14db room gian, 8 if you have 20db room gain, 4 you would need 26db room gian which might be pushing it. The best way to figure it out would be to take a sealed box subwoofer that at a certian displacment should be giving you XXdb's put it where the IB outlet will be and see how many db's you accualy get, then you can determin how many you need. Or better yet get one IB driver biuld put it in and see how much output you get, then double the number of drivers for every 6db more you need.

From what I understand, gain that low should be pretty large.
 

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Quote:
Haven't been to the cult yet.


What kind of numbers are you getting with your 4 18s?


You know, I have not run them extremely hard in a long time and I dont have the measurements. I should try to get some this weekend when the family is away.

Quote:
penn. =P Mighty big living room

Thanks, it actually has an open kitchen behind it so it makes it huge. its great for hosting, football games, parties...it has "stadium seating" but its hard to fill it with sound! I have a HT Room now so I dont care so much
 

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Discussion Starter · #11 ·

Quote:
Originally Posted by penngray /forum/post/14172294


You know, I have not run them extremely hard in a long time and I dont have the measurements. I should try to get some this weekend when the family is away.

Great. Your 18s are in an IB?
 

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Quote:
Originally Posted by Willd /forum/post/14172252


From what I understand, gain that low should be pretty large.

Or at least that's what Bosso measures.
 

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Great. Your 18s are in an IB?

Yes, 4 18s in an IB array in my ceiling. They are they original Q18s from ficar, not the new IB18s but Im sure they are very, very similar. Top displacement/$$$ drivers out there!!


Im just hooked up my new Face F1200TS amp to them, I will see what they can do!!
 

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Don't you guys dial in a sloping house curve or something? (assuming electronics can take it in the first place, which gotta be...else why chase this low in the first place
). So including room gain, a flat response won't cut it, will it?
 

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Don't you guys dial in a sloping house curve or something? (assuming electronics can take it in the first place, which gotta be...else why chase this low in the first place ). So including room gain, a flat response won't cut it, will it?

Honestly, I have never worried about or checked 5Hz, I have checked my IB down to 10Hz but I also know that some of my equipment used in the past add SFF at 18Hz or so



Its been awhile now since I have tweaked my IB with the new amp I will test what it can do down to 5Hz. Of course Im nervous about damaging my drivers!!
 

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There is no earthly scenario that would require 125dB at 5Hz. I'm not aware of any source that would require more than 105dB at 5Hz at reference playback.


A 5Hz sound wave is 225 feet long. It takes 200ms to completely emerge from the driver. It would require a room dimension of 113 feet to set up a mode, which means that it can pressurize any room. It becomes an input signal rather than a sound wave because it has no chance to appear as a complete sound wave.


Pressure Vessel Gain (demonstrated by the gain seen in cars) is in effect in every room at 5Hz. This is in addition to Boundary Gain, which can technically be 18dB with a corner placement, less losses due to the construction of the boundaries. This combination of BG + PVG explains the amplification of 5Hz in excess of 18dB in every room I've measured at 5Hz. In my own room of 4K cubes, I see >30dB at 5Hz. (See attached graph where LP response is level matched to quasi-anechoic response).


If you conduct a peak hold measurement of any given source, the SPL meter may read 125dB when the SW output trim is set +10dB hot and the MV level is at '0', but the SPL meter reading is a measurement of total sound pressure at any given instant. If the peak hold measurement showed 125dB at 5Hz, the peak SPL meter reading would be much higher than that.


Ilkka's outdoor test of a single 15" Tumult MKI, driven by 1200 watts show that it will produce 78dB at 5Hz, provided that the signal chain remains unfiltered to that point. Using that as a guide, a 2X15" 2400 watt version will give 84dB, and 4 of them (8X15" 9600 watts) will give 96dB at 5Hz. Add 30dB of BG+PVG and you have 126dB at the tail end of a 30 second reverse sign wave sweep in my room with the subs in a co-located, corner placement.


So, yes...I can measure 125dB at 5Hz in-room with my system, but there will never be a scenario that will require it to occur.


Ilkka claims that the harmonic distortion will be easily audible, even with a 30dB reduction of the higher order harmonics which will realize zero gain. I disagree with that assessment, but being that there is virtually no data on this subject, there is little to be gained from further discussion of this particular aspect. Still, Ilkka is a formidable source of logical processing of known facts, so I wouldn't discount his opinion without your own tests.


Thigpen has tested his TRW in a cathedral environment to 6Hz and concluded that 105dB is the reference level at that frequency to be well heard in relation to higher frequencies. Not inconsequentially, single digit fundamentals of sound track effects are encoded at -10 to -15dBFS, which would mean they are intended to hit your ears at 100-105dB as a reference level relative to higher frequencies.


My conclusion is that 4 of the Haskins/Wiggins Maelstrom-X 18" drivers will accomplish reference level 5Hz output with any known source fed by a proper signal chain in most any room at any LP distance.


125dB at 5Hz would depend on the room and placement, but again, I don't see the point unless it's to play sine waves at that in-room level with the sole purpose of initiating an insurance claim of some sort.


Bosso
 

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"It becomes an input signal rather than a sound wave because it has no chance to appear as a complete sound wave."


Interesting point, though I'd say that from the listener's perspective there's a wave because he experiences a pulsating pressure and ssociated perception of sound and feeling.


"Pressure Vessel Gain (demonstrated by the gain seen in cars) is in effect in every room at 5Hz. This is in addition to Boundary Gain, which can technically be 18dB with a corner placement, less losses due to the construction of the boundaries."


Isn't that double-dipping? I think PV gain *is* boundary gain, where the wavelength is so long that anywhere in the room is effectively near all of the boundaries.


Alternatively, I believe you'd need to invoke wave reflection, and as you said above, wave behavior is absent sufficiently below room mode freq.
 

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Quote:
Originally Posted by bossobass /forum/post/14173807


Ilkka claims that the harmonic distortion will be easily audible, even with a 30dB reduction of the higher order harmonics which will realize zero gain. I disagree with that assessment, but being that there is virtually no data on this subject, there is little to be gained from further discussion of this particular aspect. Still, Ilkka is a formidable source of logical processing of known facts, so I wouldn't discount his opinion without your own tests.


Bosso

You can't just say such things without any additional information. How much distortion? What kind of spectral distribution? Is there a lot of other content which is masking the distortion?


I'll give you an example. Here's a clean sine sweep that I use to measure the subwoofers. It goes from 105 Hz to 9 Hz in 30 seconds (linear). Listen to it with your favourite gear. Depending on gear, you might not hear the very end of the sweep. For reference, 20 Hz is around 26 second mark.

Clean 110db sweep.wav - 5.50MB (make sure it loads completely)


Once you have listened that, here's the same 110 dB sweep produced by the Tumult MK1 100L sealed subwoofer. This is the actual output of the subwoofer during the test session. Any additional sound compared to the previous sweep is DISTORTION. Can you now hear the sweep all the way down? Probably, because there are a lot of high order distortion components being produced by the driver which are easily audible.

Tumult MK1 110db sweep.wav - 5.49MB (make sure it loads completely)


And actually the Tumult is pretty clean at the low end (though upper bass is extremely bad), most drivers sound much worse at those levels below 20 Hz. That amount of distortion might be masked by the upper frequency content from the main speakers. But that wasn't my point, the point was that it's not correct to claim that low frequency distortion isn't audible in general. It is.


I can give you other examples than the Tumult if you like.
 

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Quote:
Originally Posted by noah katz /forum/post/14174094


"It becomes an input signal rather than a sound wave because it has no chance to appear as a complete sound wave."


Interesting point, though I'd say that from the listener's perspective there's a wave because he experiences a pulsating pressure and ssociated perception of sound and feeling.


"Pressure Vessel Gain (demonstrated by the gain seen in cars) is in effect in every room at 5Hz. This is in addition to Boundary Gain, which can technically be 18dB with a corner placement, less losses due to the construction of the boundaries."


Isn't that double-dipping? I think PV gain *is* boundary gain, where the wavelength is so long that anywhere in the room is effectively near all of the boundaries.


Alternatively, I believe you'd need to invoke wave reflection, and as you said above, wave behavior is absent sufficiently below room mode freq.


Noah's got it right here, of course the pressure modulation vs boundary gain is a matter of perspective as boundary gain creates pressure gain, where as the sloping gain of a contained space is really just a special case which doesn't apply up into the modal range. Again, it's semantics. The low frequency gain function will rise from the level of the subwoofer in the modal region, so both are at work, but they are also part of eachother.


In my own experience, I've seen many confined rooms delivering -4dB to +6dB relative to 1m gp output at the listening position as referenced around 10Hz. If 5Hz is really your goal, first make sure the electronics chain will pass it, construct your room solidly, and then design your 1m gp simulation to be in the vecinity of your desired output at 10Hz, with a 9-12dB roll off to 5Hz.


So far as how much is needed or desired below 10Hz, having heard the TRW subs and played with a variety of systems with VLF capability, I would say that and ideal goal is >110dB @ the listening position if you like to listen loud. Most rooms will visibly start to flex and move in the 115-125dB range below 10Hz.


I believe Bosso is pretty close with the typical spectrum maximum in the 5-10Hz range for a flat system. Most typically have the 25Hz and below range at least 5dB over the average level of the main speakers, and with serious main speakers and a good room, you can certainly clip a system capable of 105dB in the 5-10Hz range. Personally I feel that capability of about 100dB to 10Hz before gross compression is where things begin to be subjectively beneficial, of course oppinions will vary. A goal of 110-125dB at these frequencies is certainly a worthwhile goal which will keep you well below the maximum distortion limits for 90-98% of your listening. The point to keep in mind is that just because you can't reach 125dB, doesn't make the effort useless.
 
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