I hate cars

I modeled a few subs tonight. The AE IB15, 12W6, and JBL 15GTI.

Still got to host the pictures but here's the data...

I modeled them to find how much power it took each one to hit it's xmax excursion limit in both IB and sealed. Remember, when dealing with sealed and IB setups, SPL is a matter of simple displacement. If you take two identical subs and move them the same distance, they're going to have the same output whether IB or sealed with the big difference being power required to get there.

I threw in the power level required in IB to hit max excursion in the sealed box to see how much power is lost in sealed. If you noticed, the upper sub bass is mostly unchanged but the low end becomes so much more efficient without that enclosure to restrict it.

12W6 IB
Qtc= .488
Xmax@20hz- 180w
Xmech@20hz-300w

180w= 99.3db@20hz 106.3db@50hz
300w= 101.5db@20hz 108.6@50hz


12W6 in 1.5'
Qtc = .760
Xmax@20hz 500w
Xmech@20hz 1,000w

500w= 99.27@20hz 111@50
1,000w= 102@20hz 114@50
180= 94.8@20hz 107.2@50
300= 96.9@20hz 109.4@50

15GTi IB
Qtc= .550
Xmax@20hz- 400w
No Xmech given

400w= 105db@20hz 112@50

15GTi 2.0'
Qtc= .872
Xmax@20hz- 1,500w

1,500w= 105db@20hz 119@50
400w= 89.2db@20 103.3db

800w= 20hz- 102.3 50hz-116.3

AE IB15
Qtc= .537
Xmax@20hz- 200w
Xmech 300w

200w= 105db@20hz 111.8@50hz
300w= 106.7@20hz 113.6@50hz

The JBL can't come close to hitting xmax in a 2 cubic foot box. Thermal limit is 800w so I threw that in there as it's maximum output but it required 1,500w to hit xmax. It has the same output at 400w infinite baffle as 1,500w in the sealed box. To it's credit, the box is too small but this is a common size people use for it.

The 12W6 requires 500w in a 1.5' box to give the same output as 180w infinite baffle.

This is why I'll never run a box in a car that allows infinite baffle.

You can see a single IB15 on 200w will get as loud as the JBL15 in a sealed box on 1,500w. Having two of them is even better. This is why I don't understand why so many people list some crazy power handling number as part of their sub selection. Efficiency is much better.

Trunk Monkey

iTrader: (1)

Thanks for doing that Matt. How do they compare up around 70-80hz??

..if you still have the graphs open

niebur3

Welcome to the world of marketing and bragging rights over actual sound.

JD TL-S

iTrader: (1)

XMAX is the distance in MM how far the voice coil goes in and out for cone movement.

I hate cars

It's how far the cone moves one way with under 10% distortion. Some manufacturers rate xmax at a higher standard than 10% like JL.

Xmech is how far it can physically move before bottoming and causing damage. My IB15s have 19mm xmax and 25mm one way mechanical excursion. The 12W6 has 17mm xmax and 25mm xmech. Both still sound very good past xmax.

MOS805

Damn now if only I can find a 15" idq or more 12" to try IB.. I don't think my single 12" would cut it but I still want to try so bad.

I hate cars

There's a 15IDQv2 for sale on DIYMA for $150 right now. A single 12 with decent throw will be fine for SQ listening.

jda123

I can tell you that SBP 15 along with IB3 15 on 700 combined watts could not get within 4 dbs of a single 12" FI Q in a sealed box on 1100 watts. Real life in my car on a 20, 30, 40, 50 and 70 hz tone with near linear results. Both were plenty loud, so I concluded that the rest is just academic.

The sealed setup has energy transfered back through the cone that leads to SPL that you are not taking into account - these would vary from sub to sub and probably impossible to model. Our cars do the same thing on a lesser scale since they are pseudo IB.

I hate cars

Energy back through the cone is distortion.

SPL from the sub itself is solely determined by displacement whether it's in a sealed box or IB.

MOS805

Hmm I got to check it out, everytime I go on the for sale there I see too much I want lol, still unsure wheather to do a bigger amp or a IB since I have one 12" but I guess wouldn't hurt to try IB and see before spending more $ on an amp.

I hate cars

Are you lacking SPL right now? IB will be very close watt for watt in the upper sub frequencies but in the lower frequencies that require a lot of power, its very efficient. 2-3x as efficient as a typical sealed box. SQ is generally better as well assuming the sub works in IB. Materials should come in under $50 so its definitely cheaper than an amp.

I hate cars

I have no idea why the thumbsdown appeared in my last post. Stupid droid lol.

jda123

Of course it is distortion in the regard that not much of it is exactly the same frequency as the original. However, some of it will be reasonably useful... and some of it not so useful as it gets further and further away from the original frequency (this is why some sound quite "boxy"). ...and then factor in that the frequencies inside of the box are ever-bouncing and changing as you play music. ...then, you get into materials for the pass through. Think about it, the energy has to leave and if it was pure bad distortion, then nobody would ever even consider listening to a speaker in a box. Whether good, or bad, you need to account for it when you are considering loudness, even if it is anecdotal consideration.

Do me a favor and model out what a Dual 2 12" FI Q in a 1.2 cu ft box at 1100 watts comes in at on the software that you are using. If it matters, I have the high qts model with all of the cooling and stuff that was designed to go sealed. There is some poylfill in there too if you can model that. The box is fiberglass. I did 20, 30, 40, 50 and 70 hz, so pick one of those if you can. I will look up what it measured out at my dash after coming from the trunk. They will not even be close to one and another, but it might provide an interesting factor between the static algorithm that you are using and real measurements.

I hate cars

In car measurements will be drastically different due to cabin gain. I wouldn't be surprised to see a 30db difference on the low end. WinISD has proven to be a very accurate, very useful tool for designing enclosure and comparing subs. It won't tell you how a sub is going to sound but it will give useful info like excursion and SPL in different enclosures before cabin gain is factored in. Everything I've modeled so far has been backed up by my ears. In the beginning it was hard to figure out exactly what I wanted but now that I've done several of these I have a good idea of what frequency responses sound the best in the TL.

People use boxes because they're convenient (there's no pre-made infinite baffle) and that's what they know. There's no worry of over excursion since the box is a highpass filter. The manufacturer is going to want their sub in a box for this very reason. You get the average idiot that will throw a sub in IB and then crank the gain and destroy it. Smaller boxes mean less warranty returns. IB is super easy to set up but not idiot proof as sealed boxes are.

Boxes are what people know. IB is like black magic to most. Even a local stereo shop looked at me like I was crazy for not using a box and said it would never work. I had a JL engineer tell me the 12W6 wouldn't work in IB. It's just what we're used to. I've never seen anyone go IB and then back to sealed assuming they didn't sell the car or something unrelated to car audio. The usual reaction is why didn't I do this sooner.

Some of the threads and tests I've read show sealed to be around 1db louder at the same excursion due to distortion but this is not how I want to get my SPL. If I can't get it cleanly, I don't want it.

Distortion adds to the perception of loudness. With the stock stereo and even when I had the Infinities you could turn the stereo up to where it sounded loud and yet you could still talk over it. Then add a set of Esotars and a ton of clean power and you can turn it up to where it doesn't sound loud at all until you try and talk to a passenger and can't.

I don't think all distortion is bad. From what I've read, even order distortion can add to a warm sound. Some say that's why poly cone subs and comps have a warm sound. While I don't want a cold sound, I don't want warm either, I want a natural sound.

I just don't see the need for a sealed box in a car that's IB friendly. There are too many advantages to IB and few for sealed. For ported and bandpass you can make a good argument but not sealed.

I'll model those subs you mentioned but the only valid comparison would be against the other subs modeled due to cabin gain. The IB15 displaces 15% more air with both subs at xmax. Unless the Q was being pushed beyond xmax there's no way it could be louder. Are you saying you used both the IB15 and the IB315 together and they did not reach the same output?

The one thing I question is does the energy inside the box have to leave through the cone? Most of it is used to resist the cone movement but you have to wonder, why would you want to resist cone movement and kill efficiency?

What did you finally settle on?

jda123

Yeah, that is what I am saying. Both of the IBs together were a few decibels below the single sealed sub. I was kind of surprised, but then I thought about it... this is not some low quality setup and this stuff was manufactured and installed to be best of breed in SQ and SPL when sealed up... and it takes gobs of power, especially in burps. The tests that I had seen before compared the same sub in 2 different setups, and it was probalby not awesome at either - this was a totally different test than what I did by using what I perceived to be best-of-breed of both kinds of setups. I will look up the data in my notebook after I am done working, but generally, the IB appeared to scale with the sealed for several hundred watts, but then they fall off and the Q kept on going up. The 12 to 15" appeared to be somehow mitigated in output and the SPL meter agreed, but I have no idea why... pressure, physical resistance, location? I don't know... I am still baffled. I think that a single IB maxed out around 108db on my meter around 400w with quality that I would listen to (similar to what I am used to with the Q) and would get a little bit higher with some bad sound.

There are lots of reason why somebody would want to use IB, but output would be the LEAST of the reasons in my book. IB is never going to appeal to the bigger-is-better crowd, so don't waste your breath on them.

I get why people do not want to do it. Easy is a good reason - ask McDonalds and Taco Bell. There are some other reasons that I can think of too, though. The best parallel that I can come up with is the age-old example why anybody would still use Windows over Linux or OS X... but those numbers are changing every day due to diehards who continued to convince people of the real value... and they create new diehards every day.

Get a cheapo SPL meter, if you don't have one, and keep it in your car. While you are tricking around, grab a reading during some bad-ass song and post about it. Hard to argue with readings in a car when somebody is considering IB. I will grab some on the way to work tomorrow for some kind of a baseline.

I took the IBs out. I am not selling them, though. I will probably use them later. I am either going to keep the Q (it really does sound good) or I also have some 13" Focals that sound absolutely amazing... but they should for what they cost new (thank you Craigslist).

jda123

Power... and not just wattage. In this scenario, waves are no match for the moving assembly and the effect is hardly noticeable, which is why some can still sound so good. Don't confuse compressed air resistance with the waves. This is why I still contend that IB needs more power in automotive trunk applications even though I totally get all that you have posted before about less resistance, etc. in academic terms. Trunks are still not IB and the setup in your car suffers and/or benefits from this same phenomenon of waves and air behind the cone, even if it is to a lesser degree... maybe even a significantly lesser degree.

I hate cars

Of course power will overcome the air spring but the question is why would you want to add more power to overcome an airspring?

I like the idea of using a loose suspension and no air spring and the motor to provide all of the control. This is just my opinion but using the air spring seems like a band-aid. I'm not talking about ported or bandpass though.

Are you saying IB needs more power in automotive applications when compared to true IB in a home? Or are you saying IB needs more power than sealed?

I wish I had bookmarked all of the research I did before going IB because I had already resolved the reflective waves in the trunk in IB in my mind. They're still there obviously but to a much, much lesser degree. With the huge volume of air and carpet it's a non issue. Pressure is there, WinISD will show a change in Q from 12.5' to 100'. The vents move in time with the bass. I removed my vents and replaced with screen to lower the Q more. When you take 12.5 cubic feel along with a couple large holes, pressure hardly plays a role but I do understand what you're saying. Opening the trunk makes very, very little difference in this setup.

I hate cars

Something has to be wrong with that setup. There's no way a pair of 15s with good xmax can get outdone by a single 12 in a sealed box. Is your trunk sealed from the cabin well?

Running 2 different brands of subs at the same time might be causing some cancellation.

Was the 12 in the sealed box facing the rear of the car? In a corner?

I've seen a pair of IB15s hit 140db at the dash so something is not right. I'm trying to figure out what's going on. 120db should be very easy to hit with little power.

Displacement is all that matters in regards to SPL, that's why there's no way a single 12 with 28mm xmax can come close to a pair of 15s with 19mm xmax.

But again my original point was IB is so much more power efficient than sealed in the low end. In the upper end they're almost identical at the same power.

jda123

The readings that I got:

Q at 50hz hit 138.1.
IB3 at 50hz hit 113.2.
SBP at 50hz hit 112.9.
Both IB subs together hit 130.4 at 754 combined watts.

I have no idea if my meter compares well to others, but it should compare well to it's self.

I have no idea why these are what they are. It is possible that the installs sucked, the numbers are wrong on the specs, the drivers go well beyond specs or that some base assumptions don't prove out. I really do not care. It does not matter to me. They are plenty loud enough. I got what I wanted out of my time.

If anybody wants to test this out, wait to cut out the second hole in your baffle, or else you will have to create a new one to test the single sub setup. The IB subs were really not that great by themselves if the other one acts like a radiator.

I hate cars

How much power were you giving each driver? The IB15 will take the full 500w at 50hz without getting close to xmax.


IMO, doing a test at 50hz is no longer an IB vs sealed test. The box has very little effect at that frequency and excursion limits will not be reached so it's a matter of the sub that can handle more power thermally will have the most output whether sealed or IB.

Looking at the curves, WinISD shows IB and sealed to be nearly equal around 50hz watt for watt. Take them down to 20 or 30hz where excursion limits come into play and at the same excursion the IB will be just as loud as sealed and require far less power and the pair of 15s are going to mop up the 12. 50hz is just a test of which sub will handle the most power.

Double the power along with double the cone area will give a 6db increase. Double the cone area at the same power and you get +3db. The numbers are all wrong.

If you're testing a single sub with two subs mounted in the baffle you will lose a ton of SPL. The passive sub partially cancels out the active sub. That could be the reason for the massive difference.

I'm definitely going to get a meter. What do you suggest?

jda123

Hmmm... I didn't look at how much wattage I gave to the AE and FI. I know that I wrote it down though.

One thing that I found out for sure is that you never know how much wattage you are cranking out of an amp unless you have a large resistor at your ohm rating and an o-scope to actually test it. What I thought was 1300 watts was more like 1100, once I tested it... so I turned it up some more. Wattages can really start to drop once they get hot, too, from what I found - I tested the 450/4 that I drive my 6.5s with and output dropped about 20W once it got really hot (and they do get hot). The D class didn't drop too much.

I had to cut another board with only one hole because I found out the hard way that you cannot have a driver in the other hole not working.

You can get some cheap handheld meters for less than $40, but they stop at 130-135db. Really, you don't need any more than that since you can barely stand to be in the car at that level (or at least I cannot stand it). For regular driving and measuring, then one of these would be fine. I have a grey one that I keep in the car with me - it can do real time analysis, or do a max.

I borrowed a Galaxy (I think) that went up to 150db for my tests since I buried the 130-135db on my first burp. In the 100-130 range, both meters were within 1 or 1.5db of each other.

I think that the only real downside to IB for a true audio lover would be having to buy 2 drivers instead of 1. I don't think that everybody would be happy with the output of a single IB sub. This is a minimal downside, especially when you can offset some of that cost with box materials.

Off topic, but do any of you know how many rattles our car has over 130db? There are a million rattles behind the dash and even the outside mirrors rattle. My sunroof mechanism rattles during normal listening over 115db.

jda123

Oh, I forgot, my sealed sub is in the drivers rear corner and probably does have some corner loading properties... but to what degree, I have no idea, if such a thing is even real.

I hate cars

The inductance and resistance of the VC goes up as the speaker gets hot, lowering the voltage it sees.

If you need 2 drivers for IB, you would need 2 drivers for sealed. SPL is the same except by the small amount of additional SPL you get from the added distortion of a sealed box but that's not how you want to gain SPL. It's about displacement (cone area * excursion), nothing else.
EVERYTHING on my car is deadened. There are some things I can't seem to cure but I can push it very hard without rattles. Even harder than the subwoofers was stopping the door panels from "lighting up" around 800hz even with the doors heavily deadened and the door panels heavily deadened.

eggyhustles

Ported>all.

I hate cars

Sure, as long as "all" means "spl"

eggyhustles

Plus

Higher efficiency
More output
added flexibility
better low end extension

Only drawback is larger gross volume.

I hate cars

Efficiency- in the sense of db per watt, ported can be very close to IB. Just modeled a 12W6 in ported, sealed, bandpass, and IB since I've run these exact speakers in these configurations.

At 20hz and the same power level, IB is within 1db of the ported and 5db ahead of the sealed box. At 30hz it's at a respectable 3db loss. By 50hz they're almost even again as is the sealed box.

Output- With the same sub, ported will always have more output. However, if I needed more output than a pair of 15s could provide in IB, I would skip ported and go straight for the ultra efficient bandpass.

You NEED eq to tame the low end of the ported box or it's going to sound muddy. This is not a bad thing, it actually has the advantage of less excursion in the lower frequencies but it needs to be pointed out that unless you're a bass head, you must have eq to properly integrate it.

Not sure about the flexibility you mention. IB is more likely to play every type of music well and require very little to no eq to sound great. Ported is likely going to need a lot of eq to tame the low end.

Low end extension- No ported setup in a car tuned for music is going to play as low as IB, it's just not going to happen. Play some of the 15hz organ music I play and the sub is going to unload and destroy itself in a ported box.

Weight- IB will be considerably lighter especially when a small motor IB specific sub is used.

Trunk space- You retain 90% or more vs losing 90% ported.

Group delay- You can get some serious delay with a ported setup and the least amount of delay with an IB, something very important for SQ.

Coloration- The box colors the music. If you're in it for the SPL, it's not a concern. For SQ, it matters.

I like ported, I would run it over sealed in most cases and eq out the fr bump. I like bandpass even more and the only reason I got rid of mine was trunk space.

Each setup has it's advantages and disadvantages but for a power efficient SQ setup I can't imagine ever using anything but IB.

05TLbase

So if I was going to do this... I should get two IB 15's?

Im on the edge but I really like my amps on the back seat, looks really clean. Idk if the backside of two subs has the same appeal and wouldnt some kind of vanity plate kind of cut that whole infinite thing in half?

I hate cars

There are many subs that will work in this configuration. The IB15s are no longer available, they've been replaced with the SBP15.

I don't know what to tell you about the looks. I like the way the two subs look when you pop the trunk but I've never been into looks, more into making my stuff look stock.

You have to use the whole trunk. I made a weak wood frame with some thin cloth stretched over it that completely covers the subs like they're not there. It has to be thin, you can't restrict the backwave without changing the sound.

05TLbase

Did you remove ski port plastic and leave armrest open, or would that even matter with two since neither will be centered there?