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IB concerned?


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12 replies to this topic

#1 of 13 OFFLINE   Demas

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Posted March 31 2003 - 05:54 PM

At present i have no subwoofer, but have heard many from the likes of m&k and velodyne and although the quality is very good, many have praised the IB for delivering the finest bass, hence the reason for this.I would like outrageous output, or crazy output as they say, so an IB it has to be then, if only for using multiple very high excursion drivers.I have been accustomed to very high output, and i mean VERY high output at a friends house where he has 4 tumults installed, and it's simply unbelievable the type of output and quality of bass difference one will expect exchanging a box sub to the IB route.Compared to the velodyne HGS18, my friends IB is like looking thru a misty windows and then clearing it to see the whole view, far cleaner and greater detail retrieval.Kick drums are so impressive, and movie effects....well he has 4 tumults so there is little for the imagination.


Based on what others have attained, my thoughts have headed towards the IB, and using 4 av15's should prove interesting, very interesting.The spl is what i find most intriguing from this combination.ThomasW 12 shivas will achieve greater displacement(guessing around 3-4db) which is impressive and in the crazy output realm, as is Tom Nuisanes 8 15"s IB.When talking about output, 110 db at 20hz is good, 115 is very good, 120 is excellent, 125db is overkill, and 130db+ is crazy, so i would be in the crazy department.Keep in mind that i'm still thinking about doing this, depending on if it's even possible.

My thoughts conclude that max clean output of 4 av15's with 1200 watts,would reach 134 db at 20hz with room gain.Compared to 4 Tempests, i should be ahead by 10db of clean output.Are these guesses in the right direction?My plans are to build a simple line array, and fit the drivers, powered by the RMX 1450.It sickens me, how easy it is to achieve incredible output and best sound quality(I know it's subjective but experts have praised the quality), for literally small change.A few questions based on my IB.I would be using a closet in another room(about 7m away) and will cut the top of closet ceiling and install the baffle, a simple line array is the most simple of any IB design and is just requires the right length baffel board and cut circles and place the drivers, wire them up and bass nirvana in a nonsarcastic kind of way.This design is the same as Mike Knapps and is dead easy, at least i assume it is, but how much space would be required behind the drivers, as there is very little space in the actual closet, but there is about 14X15X6 behind them where the attic is?Would the IB work with being in another room, only a couple meters away?I'm a little worried that there is very little space in the actual closet, as won't the drivers move too much air inside a small space prove disastraus?Lastly if anyone has an IB, I would be grateful to hear your experiences and insight into your expectations with them.

Regards

#2 of 13 OFFLINE   Dustin B

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Posted April 01 2003 - 12:46 PM

I'm a little unclear. You're planning on doing what Mike Knapp did right?

So you have a closet that will allow the drivers to fire into the room. You also have an attic space that is >1250ft^3. 4 AV15 drivers should have 325ft^3 plus behind them to be a proper IB. So if you seal the closet well and make a large hole in the roof of the closet to the attic you'll have no problems at all. Provided where the drivers will be firing into the room doesn't result in bad room modes.

PS- Did BrianKR finish his IB and not tell any of us?
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#3 of 13 OFFLINE   ThomasW

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Posted April 01 2003 - 05:10 PM

Quote:
My thoughts conclude that max clean output of 4 av15's with 1200 watts, would reach 134 db at 20hz with room gain

Well you'll very likely bottom the VC's.

Look this isn't car audio dB drag racing and can't be, unless your house is made from solid concrete. Standard stud frame construction isn't designed for this level of output. If you want to try it realize that you will have drywall cracking and run a fairly high risk of blowing out windows. In addition heating ducts will rattle, things will vibrate off shelves, you'll destroy the filaments in light bulbs, doors will rattle in their frames, etc, etc, etc.......

No the IB drivers themselves can't be in a different room, there would be significant phase issues.

If you can open the closet to the adjoining space then the drivers will see the sum of the space provided by the closet and adjoining space

#4 of 13 OFFLINE   Demas

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Posted April 01 2003 - 06:11 PM

Quote:
I'm a little unclear. You're planning on doing what Mike Knapp did right?

Yes, this is what i'm planning to do.To answer fully, i was confused because the amount of space within the closet seem very small, but there is enough space to mount the baffel, i'm just worried that the drivers will have an adverse effect of being in too small a closet.

Directly above the closet is the attic, obviously i must still cut the top board out for this, and I definitely have enough space directly behind them.

Quote:
Well you'll very likely bottom the VC's.

Are you saying that 4 av15's cannot achieve this output?Obviously i have no intentions of reaching these levels, as you are with yours.4 tempests could reach well over 120db at 20hz, correct?Would not 4 15's increase clean output by 10-12 dbs based on preminary specs?

The closet is exactly 7m from the listening position, so will there, can there be no IB in this case?I'm not entirely sure of what you mean't in your lost two sentences, could you please explain as if i'm kind of lost, sorry if I seem a bit confused.

Regards

#5 of 13 OFFLINE   Hank Frankenberg

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Posted April 02 2003 - 12:00 AM

130db+ is crazy, so i would be in the crazy department


WHY in the world do you want 130dB??

Look this isn't car audio dB drag racing and can't be, unless your house is made from solid concrete


Exactly

#6 of 13 OFFLINE   Bryan Michael

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Posted April 02 2003 - 12:32 AM

dual av15 can push past 125db i was playing brass monkey and turned it up. then turned it down after getting a reading. i need to try lower. also i am in the basement.
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#7 of 13 OFFLINE   ThomasW

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Posted April 02 2003 - 12:47 AM

The stated 7m distance (~21') could create phase issue problems between the mains and the sub. Obviously you should check the potential sub placement, using the methods described on the "Cult" FAQ page, before beginning this project.

#8 of 13 OFFLINE   Demas

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Posted April 02 2003 - 04:08 AM

Would 1200watts be overkill with 4 av15's?What amount of power would be needed to reach maximum excursion?

I just looked at your design, how painful was it to cut the opening to the outlet of your IB to the basement?Do you use a grill to cover?

I understand that 130db+ at 20hz is impractical in my case, as the drywall will crack and cause falling debris, however I

would like 121db with the extra 10db+ for greater dynamic headroom, THD levels should be non-existant, and very linear in

their range.I don't ever won't to worry about bottoming at reference regardless of material, hence the reason of 4

av15's.Just like your 12 shivas(if you still have them) 18L VD should be capable of greater than 134db at 20hz in a modest

size room, even though you won't use it, it does contribute to even cleaner output at the required level of use.14L VD

compared to 18L is about 3-4db, is this more or less correct?Bass cancellations would probably compensate for a couple dbs, how severe are the cancellations?It's just like the B4+, more output than you would care to use,

yet you benefit with cleaner bass at reference lvl, as the drivers stay in their linear range with less effort.

Thomas Nuisanes IB with 8 TC-SOUNDS 15"(not entirely sure which driver) is even more crazy, probably more output wise than

your 12 shivas i'd think, so i'm wondering if his system was more of a design goal of reaching a certain db level, car spl's

no doubt.My design is line array, which as you know is the easiest to implement, however are there any serious disadvantages

compared to manafolds?Would I benefit with manafolds in my situation?

Regards

#9 of 13 OFFLINE   David Lorenzo

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Posted April 02 2003 - 03:57 PM

Would 1200watts be overkill with 4 av15's?What amount of power would be needed to reach maximum excursion?


I modeled your IB plan as a huge sealed enclosure and with 1200 watts you would reach max excursion at ~17 hz.

#10 of 13 OFFLINE   Demas

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Posted April 02 2003 - 08:39 PM

Quote:
WHY in the world do you want 130dB??

Firstly thanks for the replies.Secondly because i would like to listen at reference lvl with no compression or thd, just absolutely clean bass at this lvl, which happens to be very hard to accomplish by ordinary means.Once you reach 121db down to 20hz, thats just the first step.Then you question,is this at its limits or within the linearity of the drivers motion?How hard would it be to achieve this level with 2-3% THD?Based on a IB, it seems to be the most plausable way of reaching lvls you want(obviously depending on drivers employed), while having no distortion characteristics like power compression at peak lvls, but atleast you are given these options.

My friend, invited me to his home a few weeks back, and his system was simple incredible(4 tumults in a manafold)he used 400 watts per driver(not sure if this is overkill power), and the ball explosion at reference lvl was astonishing.We played monster inc. the scene where there is this door knock, at reference lvl, i thought i was going to have heart attack(in a good way) the force was just so great it was beyond belief.The amount of air moved was beyond anything i have ever experienced, and i've heard incredibly expensive albiet lacking subwoofers(in the absolute sense) such as the Wilson XS.Now if this is using 4 tumults, then 4 av15 won't be too far behind, i'd suspect.I heard expensive subwoofers that simply pale in comparison, even the Krell MS was dynamically limited in those scenes with a sense of compression as reaching its limits, however this room was 4000cuf large.20k and still not performing as expected gives you a sense of anger and frustration.

With regards to headroom, its better to have the linearity of drivers motion at 30% than at 90-100%.In this case, with more than 10db+ of additional headroom, that would mean many, many years of use, as i will never exceed 50% in practice.If I had to constantly barrage the system at or near it's limits with very big dynamic swings, or bass material that needs headroom to perform cleanly,then i doubt that it would last that long.This is why, i honor systems that are capable of far more output than you would care to use, just for the sake of knowing that the drivers will never come close to half their limits, such as ThomasW, Tom N and others.

I ask again, are there any significant advantages to using a manafold compared to a line array?Would walls handle the pressure better if a manafold is employed?Would I benefit in my situation?

Regards

#11 of 13 OFFLINE   RichardHOS

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Posted April 03 2003 - 12:39 AM

From what I can gather, a line array should offer the fewest sonic compromises, but a manifold eliminates most of the mechanical forces produced by the cone motion of the drivers. A wall would probably not take to well to four AV15's mounted directly into it.

#12 of 13 OFFLINE   Mike Knapp

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Posted April 03 2003 - 01:43 PM

I havent had any problems...

Posted Image


Just a crack or two in the plaster. Posted Image

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#13 of 13 OFFLINE   Demas

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Posted April 03 2003 - 06:39 PM

If i cannot use a line array, then a manafold might be the only way, and according to other members, this can slightly improve quality compared to line array.

If this is incorrect, please correct me.I was told over at AVS, that manafolds will give less harmonic distortion if drivers are in opposed directings, but you would get slight bass cancellations as a result.Manafolds would also take care of most of the mechanical forces which another wise would rattle the wall loose and cause cracks, hope this is correct.

What i would like to know, does it matter how big the manafold is, as i've seen different size manafolds that hold 4 drivers.Ones a small cube, while another is a larger rectangular shape box, so does it affect sound quality if the enclosure is too small, even if it contains the 4 drivers?If this is incorrect, then it seems that i should build a cube that will hold 4 drivers(don't have the proper tools, must go to a carpenter).The only big concern is cabling.How on earth would i get enough cabling from the ceiling back to the listening position?

Regards


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