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Discussion Starter · #1 ·
Search function is driving me crazy. I cannot find anything that I know is there.
Few general questions regarding IB.

1. What kind of sound can I expect in comparison to sealed box?
2. DO subs have to fire 100% into the cabin or can they fire in the rear seat back?
3. I have 600wrms on hand, I guess I would want 2 drivers? 10s, 12s? I am really digging the sound of single 10" in a sealed box sitting on my rear seat., but I can't get 12"s to work in my car. Don't know why, just didn't sound right.
4. How far up can IB setup play?
5. IB: yay, nay?

Resonant Frequency (Fs) 30Hz
Equivalent Volume (Vas) 84 l 2.97ft3
Total Q (Qts) 0.45
Electrical Q (Qes) 0.47
Mechanical Q (Qms) 9.8
Compliance (Cms) 230µm/N
Moving Mass (Mms) 121g
Cone Area (Sd) 510cm2
Voice Coil Diameter 51mm
Voice Coil DCR (Re) 1.6Ω
Voice Coil Inductance @ 1kHz (Le) 0.40mH
Linear Excursion—One Way (Xmax) 8.5mm
Peak-to-Peak Max. Excursion 40mm
Reference Efficiency (ηo) 0.46
 

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1. good sound
2. they can fire in the seat, I don't think the seat will totally "kill" the whole deal. there's difference, but I don't think it's critical if there's no other way to do it.
3. i have 600w amp and two 12s and they do fine.
4. i dunno, depends on the driver? inductance may be an issue?
5. yay but it depends on a sub choice.
with the specs you have listed, I'd be scared to turn it up. you need more balls.
as far as other stuff, let me dig something up for you.
 

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Discussion Starter · #3 ·
Thanks, I just read your IB DIYMA article. By guts, you mean I need more power or excursion, or?
 

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no, power is fine. i mean i'm really surprised how much i get out of 300w a piece.
excursion yes, I think it's a fairly important thing for IB.:) i mean 8.5 mm one way is on the shy side. you could prob get away with a larger driver and not so big xmax, say like dayton 15 that bob titts is running, but it depends on your listening preferences.

for ****s sake, whats going on with search function, takes forever. damn we need another server upgrade. :rolleyes:
 

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1. Better in my case. Flatter response than a sealed box. Sounds better to me.
2. Mine fire into my rear seats. I've seen somewhere that a person was saying the rear seats act as a LPF and seemed to be shutting out anything above 60hz for him. I haven't had this problem at all. *Check out the figure at the bottom of this post*
3. 600w would probably suffice but it depends on the drivers. I haven't done any measurements to see what I'm feeding my 2 Idmax's, but I'd say its probably 600w or more. For 10's I'd thnk that'd be plenty.
4. I set my LPF for 140hz in the picture below and set no HPF. Subs played flat all the way through 100hz with no problem at all. Check picture below.
5. Not sure. I'm not familiar enough with high spl woofers to know if that'll do fine IB. For a door install it looks to be pretty good, though. If things are the same, then they'd probably do good. I'd still pull up winISD and do some modeling to see, though.

** referenced in #3 & #4 **

This is the response of my IB wall. (2) 12" Idmax's pointed straight toward the cabin, playing through rear seats.
From this thread:http://www.diymobileaudio.com/forum/showthread.php?t=43122&highlight=rta+results

 

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Discussion Starter · #7 ·
I like a combination of front mids and subwoofer for my midbass. Will I loose it if I go IB? Thinking 2 10" IDQ v.3s with 300wrms each.
 

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beauty of Ib is the added efficiency on the bottom end. Power is rarely an issue in an Ib install, normally surface area is more important.
 

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I used to use high xmax subs, now go for cone area. I just found I prefer it...
 

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with ib the subs won't take as much power as they do in sealed enclosures because there is no back pressure for the motor to work against going either direction. as stated, 600w is plenty.
 

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I'm on the boat with backwoods.
Xmax is nothing but highly overated spec for an IB SQ application. Notice most subs that model up for IB dont use or say waste a high displacement motor? Not to say you cannot use one for trhe application.

Excursion is not nearly as important IB as is cone area, particularly in a level matched, balanced SQ system. You can only use so much motor before the structural rigidity of the baffle and rattling go to shyt. The more cone area, multiple drivers raises the overall system Q finding your self with this 'seamless' , 'musical' sounding and linear/flat overall sound many talk about.

Like yermolov, i too have about ~600 rms to a deuce of twelves and its more than i need to do the job and dont find myself coming near the mechanical limits of the drivers before i'm stupidly satisfied with the bass output i desire on any track or volume level.
 

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I am pretty much anti-xmax in general....IB, sealed, vented, etc. Nice to see others catching on.

Something to consider when opting for a trunk baffled "IB" setup that NOBODY talks about is the baffle size. This is especially true for parcel shelf/rear deck mounting (not so much an issue when you build a wall behind the seats like Manny's Maxima).

I'm not talking about baffle thickness, but overall area around the woofers. The more area you have around the woofers the better you are separating the front and rear waves, allowing a truer approximation of an IB setup, otherwise what you really have is a large sealed enclosure.

Infinite Baffle means just that; infinite *baffle* not so much an infinite enclosure volume (although a lot of volume is required of course). By doing this you get less standing waves, and smoother response.

You can reap all of these benefits when designing enclosures. Better to have a very wide enclosure that's not very deep than a narrow enclosure that's deep. Some of the enclosures for the speakers I sell and custom make tend to be a bit wider than the norm.

I don't have any specific formulas but for most cars I wouldn't go bigger than 8" or 10" on a rear deck....12" is pushing it in numerous instances and 15" is just too big. If you want cone area, fine...just go the multiple driver route in this case.

This is not to say that if you violated the rule, it would sound like s***. Just wouldn't be 100%.
 

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Discussion Starter · #15 · (Edited)
I don't doubt your experience. I'm simply saying there is no reason all 12 inch subs would perform poorly in your car. To satisfy my own curiosity could you list some of the subs you have used?

Sounds like you are looking for midbass reinforcement more than sub bass given your preference for 10s and your questions about how high IB setups can play. Where do you cross your sub currently? Do you care about performance below 30 hz? I don't see any reason not to use IB, but it might not be worth the effort if you aren't looking for low frequency extension.

IDQ12v1, IDQ12v2, IDQ12v.3, ID12v.3, IDMax12v.2, IDMax12v.3, Boston Acoustics LF 12.5.

I do, but I am not sure whether I want to get involved in IB just yet. I'd like to leave rear shelf alone. I already have steel wall behind my rear seat back, so I was hoping I could utilize that by adding a 3/4 baffle and firing subs into the seats if it comes to IB. I do have an armrest in the back seat, not sure if it will help. I am leaning towards single 10" IDQ sealed against ski pass.

I currently have mids crossed at 80hz/18 and sub at 80/24. I am in process of building kicks for my mids, so I was going to get that wrapped up before I move into my sub stage thing. So far, I do like reinforcement provided by the sub. I wish I could audition a quality IB locally.

Thanks.

P.S. So will those Bostons listed in the original post work for IB if I decide to go that route?
 

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I used to use high xmax subs, now go for cone area. I just found I prefer it...
oh I agree, although I don't have first hand experience with bigger drivers in IB, since I had 2 diymas and no extra money on something else, so I decided to try them IB...
I just responded back to his posted specs and me thinks that I would want at least two of those (I was getting worried about over excursion if that xmech of 40mm peak = 20mm one way? I think I can move my diymas that much easily)
 

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Discussion Starter · #18 ·
oh I agree, although I don't have first hand experience with bigger drivers in IB, since I had 2 diymas and no extra money on something else, so I decided to try them IB...
I just responded back to his posted specs and me thinks that I would want at least two of those (I was getting worried about over excursion if that xmech of 40mm peak = 20mm one way? I think I can move my diymas that much easily)
Thanks. If I go with those Boston, I will definitely have (2) 12". How does that sound?
 

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I am glad I came accross this thread - do others feel similarly that two 15s in a rear deck is less preferrable than two 12s for reasons stated (more baffle area around a sub is better? With no experience in this area, I have no basis to question this, but it would just seem that as long as everything was sealed up 100% between front and back things would be all good.

Additionally, I am wondering what those who have experience with rear deck installs think about the necessity of cutting holes for the subs. Can I just fire them into the rear deck (the only air would flow through factory 6" openings and would do so not directly above each sub) - would this work or is cutting necessary?
 

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I am glad I came accross this thread - do others feel similarly that two 15s in a rear deck is less preferrable than two 12s for reasons stated (more baffle area around a sub is better? With no experience in this area, I have no basis to question this, but it would just seem that as long as everything was sealed up 100% between front and back things would be all good.

Additionally, I am wondering what those who have experience with rear deck installs think about the necessity of cutting holes for the subs. Can I just fire them into the rear deck (the only air would flow through factory 6" openings and would do so not directly above each sub) - would this work or is cutting necessary?
If your OK with this compromise , DO IT ! ;)
 
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