# GB25 sealed or ib



## gregerst22 (Dec 18, 2012)

I am in the process of building sail panel pods for audiofrog gb25 midranges. The pods can be sealed with .17 cubic liters of volume or i can vent them down into the door. Which would be better?


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## Bayboy (Dec 29, 2010)

Personally, I prefer sealed on any small mid to help out in it's piston range.


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## Shane (Oct 8, 2009)

I just finished installing the GB25's in my lower A-pillar and used white PVC endcaps that are available at Home Depot to act as a sealed enclosure. I fiberglassed them into the pillar and they worked perfectly.
I think that it is most important to contain the sound from the back of the speaker.


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## SkizeR (Apr 19, 2011)

.17 cubic liters is to small unless you use a high crossover on the low end. The gb25 wants at least .3 liters. I'm about to add gb25s to my car and am in the same predicament 

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## nstaln (Feb 11, 2009)

the GB25's do very well in tiny sealed...I made pods the same size as pvc endcaps and they sounded fantastic...thinkin about adding them to my current 5.1 surround build with all Froggy speakers...


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## Shane (Oct 8, 2009)

I have mine crossed over at 390hz with a steep 48dB LR crossover so there wont be any damage to the driver.
I saw Andy at his shop last week and he gave my a-pillar install two thumbs up.



SkizeR said:


> .17 cubic liters is to small unless you use a high crossover on the low end. The gb25 wants at least .3 liters. I'm about to add gb25s to my car and am in the same predicament
> 
> Sent from my VS988 using Tapatalk


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## SkizeR (Apr 19, 2011)

Shane said:


> I have mine crossed over at 390hz with a steep 48dB LR crossover so there wont be any damage to the driver.
> I saw Andy at his shop last week and he gave my a-pillar install two thumbs up.


Yes but the question at hand is should the op do sealed or vented into the door. I would say sealed if he can squeeze put the proper amount of airspace

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## Shane (Oct 8, 2009)

As an aside, the GB25's replaced my Dyn's, and there isn't even a comparison. The Audiofrog GB25's sound superior in every way. The difference is dramatic.


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## Shane (Oct 8, 2009)

SkizeR said:


> Yes but the question at hand is should the op do sealed or vented into the door. I would say sealed if he can squeeze put the proper amount of airspace
> 
> Sent from my VS988 using Tapatalk


Yup - I agree with Nick - sealed if you can do it..


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## SkizeR (Apr 19, 2011)

Shane said:


> As an aside, the GB25's replaced my Dyn's, and there isn't even a comparison. The Audiofrog GB25's sound superior in every way. The difference is dramatic.


Interesting. Where were you during the dyn vs frog thread a week ago lol

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## Shane (Oct 8, 2009)

SkizeR said:


> Interesting. Where were you during the dyn vs frog thread a week ago lol
> 
> Sent from my VS988 using Tapatalk


I must have missed that one... 
But I am an believer in Audiofrog for sure..!


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## Elgrosso (Jun 15, 2013)

Would they share the space with the woofer if vented in door?
Anyway I had mine in a tiny sealed volume and of course it helped a lot on power handling, I think I had them around [email protected] 
But after some time I kept raising and raising the XO so finally the enclosure was not that important.


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## gregerst22 (Dec 18, 2012)

I might be able to squeeze .2 liter or a tiny bit more, but at .3 i think the pods will be too big for my liking. 
Last weekend I was playing around with them in pvc pods that had about .2 liter and I thought they were sounding pretty good crossed at 300hz lr4. I don't really think i need to cross them any lower than that, even 325hz - 350hz would probably be fine.

On the ib route I have the option of venting them down through the door cavity, sharing space with the woofer, or i can vent them between the door card and door skin. Or i can do both. Which would be preferred if doing ib?


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## Elgrosso (Jun 15, 2013)

Best would to seal it, even in too small since you won't cross too low.
But if not, at least it should not share the woofer space, door card then.


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## dsquared (Aug 10, 2016)

In a 3 way front end and barring any space issues, when would one use a gb40 over a gb25? I don't see the 40's used much.


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## kmbkk (Jun 11, 2011)

dsquared said:


> In a 3 way front end and barring any space issues, when would one use a gb40 over a gb25? I don't see the 40's used much.


I'm actually going to run the 40s in a 3-way front end and was also curious why they don't seem to be used as much.


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## I800C0LLECT (Jan 26, 2009)

Mine are IB in the kicks at 330hz with 24dB slopes. I think sealed is great for power handling when crossed lower but they definitely get loud and sound good doing it. I'm not worried about getting an enclosure for them

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## gregerst22 (Dec 18, 2012)

I was able to eek out a little more space in the pods and got them to .21 liters. I'm going to try that. I think i'll be happy but if not I may have a trick to give them more air space without making the pods visibly larger, though it'll take some extra work. 
Also, would poly-fil or similar provide any benefit?


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## Patrick Bateman (Sep 11, 2006)

IB is great for subs. It's not always practical to build a 4-6 cubic foot box for a sub or two.

IB is not so great for midranges. You can improve power handling by using a small sealed box. One exception to this rule is if you're able to apply a carefully tuned highpass.


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## I800C0LLECT (Jan 26, 2009)

Is there any benefit in isolating back wave? I was really concerned about not sealing it up until I realized Scott B. and many others don't. I just figured it was mostly for power handling and to keep from sharing space with a mid-bass or sub?

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## dgage (Oct 1, 2013)

Everything is a trade off. A sealed enclosure is also called acoustic suspension as the air inside will only compress so much when the driver pushes into the enclosure, which helps control the driver's suspension giving added strength/control. With IB (or ported below port tune) the only control is provided by the stiffness of the driver's suspension.

IB done right is to get full extension without a ton of power. Sealed needs more power because the driver is "fighting" against the enclosure and has a natural roll off of the deep bass due to the enclosure. 

I'd say going IB in the kicks is mostly about getting as much airspace as you can. IB in the trunk is about getting deep bass without a ton of power and without building an enclosure although you do need to seal off the trunk from the car.

Which brings up a final point and I think the answer to your question. If the front wave and back wave meet, the waves will interact and you can get some cancelations and additive coupling(boominess), which is why IB has two separate spaces that never meet.

And I just realized who I was answering and your experience but I'll leave most of it as it may be helpful to others reading this in the future.


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## estione (Jul 24, 2009)

how does this go from a 2.5" midrange to a subwoofer????????


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## I800C0LLECT (Jan 26, 2009)

Dgage... Your points are all right. Air space requirement isn't a big deal if mid-range only though. The rear wave issue is valid too. But I think measurements are needed to identify if that's going to rear it's head. I have a big Spike at 800Hz (thanks Babs). Otherwise, I don't see downsides with this approach. Everybody is bringing up great points for the most part.

In the end, IB will interact with the environment much more than sealed. There will be tradeoffs and I think we all pointed them out. Good thread. I'm good at regurgitation but I may try sealed just to experience the difference. Application is always key. I've learned a lot just by throwing things together

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## I800C0LLECT (Jan 26, 2009)

Op... Why not just go sealed and see if you can get a measurement? I think sealed is the easiest way to get what you want from the driver

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## dgage (Oct 1, 2013)

estione said:


> how does this go from a 2.5" midrange to a subwoofer????????


The laws of physics don't change. A speaker, also known as a transducer follows the rules of physics no matter the size or frequencies. So a midrange in a sealed enclosure will have a roll off just as a sub will have a roll off in a sealed enclosure. The thing is, if you can put enough airspace in the midrange such that is doesn't roll off above the point you want it to, then you're golden. As an example, say the enclosure naturally starts rolling off at 300 Hz but you plan to crossover to the midbass at 350 Hz, then you're golden. Or you don't put a crossover on the midrange at all and just use the natural sealed roll off to integrate with the midbass. That's possible but if you push the midrange hard, I'd put a high-pass crossover just to protect it from damage.

With IB on the midrange, you will need a crossover to integrate with a midbass to protect the midrange from over excursion. And you'll want to isolate the front and back waves as we mentioned. And you don't want a midrange and midbass sharing the same airspace (door) as the midbass would overpowerhe midrange and negatively affect how it performs.

Simple fact is sealed is simple. Simple to calculate and simple to build and less prone to damage caused by errors. IB doesn't have some of the protections of (acoustic suspension) so just for peace of mind, I'd use that over IB. IB works great but it is more susceptible to damage to being over driven or not setup correctly.


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## gregerst22 (Dec 18, 2012)

Thanks for the replies everyone. I got the pods installed today. Internal volume is about .21 liters. I took a few quick impulse response measurements. no eq, red is a few inches away from the speaker. the others are left and right measured at headrest at my normal seating position.



















edit: fixed broken image link


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## I800C0LLECT (Jan 26, 2009)

Really glad you posted that for everybody! Looks like a good start

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## brumledb (Feb 2, 2015)

Looks like you have the same dip at 2k I have even though yours are on axis while mine are in the stock dash location. Weird.











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## gregerst22 (Dec 18, 2012)

yea one side has a dip at 1k and the other at 2k. not sure what to make of it. easy enough to eq though as I am only cutting freq to get my curve.
i originally had them sealed in the a-pillar and fairly off axis, which was aimed at the backside of the review mirror, because I didn't want them sticking out too much and obstructing my view. But i just could not get them to sound as good as I wanted or expected. This is the same issue i had with scanspeak 12m that were in the dash. After many many hours of tuning I gave up. Now that these are on axis they sound so much better and super easy to tune. All of the tonality issues i was dealing with are gone.


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## brumledb (Feb 2, 2015)

Sounds like it was worth the effort. Where are you putting your tweets?


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## gregerst22 (Dec 18, 2012)

Definitely was worth doing. I am not exactly sure where I'll put the tweeters. One thought I had was mounting them on axis behind the pillars.


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## 156546 (Feb 10, 2017)

You can put these things in a box that's just big enough to fit over the back of the driver and they'll be just fine.


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## 1sty (Jun 24, 2009)

anyone running these without a tweeter?
Thoughts/results?

From their literature, it looks like these do well to 16K and above that could be eq'd.


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## 156546 (Feb 10, 2017)

OK, guys. 

Since this is a small midrange driver and will undoubtedly be used in a 3-way with some other midbass driver, then we can assume that the system will also use some kind of an active crossover. 

That active crossover, just like the suspension of the speaker coupled with the enclosure (or lack of an enclosure) is a high pass filter. 

The GB25 was designed so you'd be able to put it in a really small A-pillar box and still get the low frequency extension you need without having to build watermelon sized boxes. They were also designed so that you could simply build a little pod without considering the airspace--part of my job as a product designer is to make products that work well even when people don't understand how to use them or bother to read the manual.

So, here are three box models that include a 4th order Linkwitz-Riley high pass filter at 200Hz. 

The first one is a huge box, essentially Infinite Baffle:

https://www.dropbox.com/s/zj83hbey1324j28/GB25.JPG?dl=0

The second one is the smallest rectangular box you could build around the speaker and still the basket and motor fit, also modeled with the high pass filter. This one is about .162 liters.

https://www.dropbox.com/s/4i3gu3xfx60x4ql/Smallest.JPG?dl=0

And the last one is 0.25 liters. 

https://www.dropbox.com/s/9xb4iqycel3d59r/250%20ccm.JPG?dl=0

So, the moral of the story here is that in these three applications, the response of the speaker is only SLIGHTLY different. There's no point in venting the driver into the a-pillar, but you can if you want. You can also use this in IB because a 200Hz crossover mostly eliminates the effect of every enclosure that can be built to house this speaker.

A GB40 is designed for infinite baffle--primarily for dashboards and the doors of BMWs. There's no point in using the GB40 in an a-pillar. That's what a GB25 is for. 

Here's a GB40 in the same .25 liter box with the 200Hz high pass filter:

https://www.dropbox.com/s/qv6i6jfhst1o6n6/GB40%20250.JPG?dl=0

See, not as good as the GB25 in this application. In a 1 liter box, it performs just as well as a GB25.

https://www.dropbox.com/s/4i00bus3rwx0cb2/GB40%20one%20liter.JPG?dl=0

But, in the door of a BMW, where the speaker has to play a little lower to meet the 8" under the seat, the GB40 will handle a little more than 100W RMS before reaching xMax with a 120Hz 4th order high pass filter. 

https://www.dropbox.com/s/d7s33gzwp99gl8s/GB40%20IB.JPG?dl=0

So, if you really think that there's going to be a difference in the performance of your front stage with a-pillar pods with them crossed over at 120 vs 200, then you can use a GB40, but it will have to be in an IB.

My objective was to make a little midrange that would handle plenty of power with low distortion that you could put in a tiny a-pillar box without any hassles. There's no speaker that does this better.


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## 156546 (Feb 10, 2017)

Stupid. I wrote all of that and posted the pictures as images, but when I save, it strips out all of the images. So, all the images are in there as links. 

What a hassle.


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## glockcoma (Dec 22, 2015)




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## danno14 (Sep 1, 2009)

Right out of the frogs mouth!

Thanks Andy


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## Babs (Jul 6, 2007)

Open pillar because that's how the chips rolled for my first uneducated pillar job.. Keeping them conservatively crossed at 349hz LR4 as a lowest limit, they've done quite well. Had considered trying to seal them but I'd only accomplish really in making leaky tiny enclosures at best, so not sure on that. But man they do bring the goods. Their acoustic HP roll off of course is a bit lower, as are my GB10's. going to work on their transition a bit though as recent look at their coherence with Niick indicates (my theory) their angling might not like a 5khz crossover.. Polar response limits with the 2.5" driver. Since I've room to spare that may come down a bit if the tweeters play lower better than the GB25's play higher in that region. Maybe 3500, or 4000ish possibly. 


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## I800C0LLECT (Jan 26, 2009)

When I was running my 3 way setup I think I had settled in 3200MHz between the GB10 and GB25. The tweeter might surprise you. Mine were split though... Tweeter in pillar and mid-range in kick panel. 

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## 619Tundra (Sep 24, 2020)

I heard from Jeff Smith that by using Black Hole Stuff for fill will make the driver sound better.


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## 619Tundra (Sep 24, 2020)

I heard from Jeff Smith that by using Black Hole Stuff for fill will make the driver sound better.


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## dumdum (Feb 27, 2007)

619Tundra said:


> I heard from Jeff Smith that by using Black Hole Stuff for fill will make the driver sound better.


I have honestly never seen any actual data or proof that this offers any benefits over Dacron or any other form of enclosure stuffing, especially in an enclosure as small as the one a gb25 fits in... and how little you can actually fit in...


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