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Discussion Starter #1
Hi there,

I currently have an IB using the original Mach 5 18" drivers (I think MJ-18 is the official name; something like that, anyway).

All in all, the IB works pretty well. However, I'm wondering if I could get better performance out of different drivers. I'm pretty sure that I can get away with only using two drivers, especially if they are of better quality. Using four drivers, I don't think I've even approached max output, and when I test it at high volumes, there's more output than I'd ever need.

I don't know much about all the various parameters of a driver, and I really don't have the time to research it (for better or worse). I also don't have any experience with speaker modeling software, and don't have time to learn it either.

Does anyone have any experience in going from the MJ-18 to a different driver, and what was the result in sound quality? I'm interested in any other opinions in this type of perceived change in different drivers.

Budget for two drivers isn't much of a concern. The lower the better, but let's try to keep it under $1k for the two.

Thanks!!!
 

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What do you like and not like about your current setup?

That would help...

Personally, I went with Fi Audio drivers as I have a Q-series sub in my mobile system, and it's a fantastic driver.

4 of the 18's would run you $800 - you could use 2, but 4 wouldn't have to work as hard.. making for cleaner sound, but the IB18's have a 30mm(!) xmax, so they will move some air even if you use 2, like I am (for now)
 

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Discussion Starter #3
I'm not sure that there's anything that I don't like about my sub -- it's just that I wonder if I could get "better" performance from different drivers. I have never heard another IB sub, so I have no ability to compare that way. As we know, it's difficult to describe these types of nuances. Thanks!
 

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I don't mind helping you model a few. I would like to model the Fi drivers, but some of the parameters are off and Scott has not responded as to what might be the problem.

I am assuming you only want to go with 18's and at present you only have room for two?
 

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Discussion Starter #8
Thanks, Sonnie!

Well, I currently have four 18's in my IB. If the new drivers are deeper than the MJ18s, then I might not be able to get one in the IB (the back end of the magnet would hit against a wall in the crawlspace). Plus, I think I really only need two drivers. I just have so much with four drivers, and if I go to better drivers, I think two will do it.

I was thinking of sticking with 18's, just because that's the cutout on the manifold. However, if there's a compelling reason to go with smaller drivers, then I'm all ears. I could make something to make the cutout smaller, but I can't feasably go any bigger (though ya don't really hear much about drivers larger than 18").

Thanks again!
 

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If the new drivers are deeper than the MJ18s, then I might not be able to get one in the IB
Looks like you'll have a problem with the above mentioned subs. Here are the mounting depths:

MJ-18 - 8 inches
IXL-18 - 9.75 inches
RL-p18 - 9.65 inches
Maelstrom-X -11 inches
 

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Can you mount the one driver that will be close, in the reverse direction?

I don't know what your manifold setup looks like, so don't know if that's feasible.
 

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Discussion Starter #12
I might have an extra 2" behind the current setup, so the RL-p18 might fit. If I go to two drivers only, though, there won't be any problem -- three sides of my manifold have plenty of room around them.

Good idea on mounting the driver on the inside -- I think that would work if push came to shove.

Sonnie, from your latest graph, it looks like I'll be able to get more absolute SPL out of the four I have when compared to the two Maelstroms. What about the flatter frequency response you should for the RL-p18 in post 5 above? Is that worth anything?

I'm heavily considering the RL-p18s that are for sale here at the shack.
 

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Sonnie, from your latest graph, it looks like I'll be able to get more absolute SPL out of the four I have when compared to the two Maelstroms. What about the flatter frequency response you should for the RL-p18 in post 5 above? Is that worth anything?

I'm heavily considering the RL-p18s that are for sale here at the shack.
The Maelstrom X drivers actually have a flatter response... the RL-p18's roll off a little faster. I am not sure I would call it significant, but it is possible that it may be slightly noticeable, especially with more power that the MJ-18M's cannot handle.

Here is the response with 4 drivers each...

ibforotto7.jpg

Where you will notice a difference is you will be able to drive the RL-p18's or the Maelstrom X to much higher levels before reaching full excursion. Right now you are not using much of your EP2500 on those MJ-18M's before they run out of steam.

Here is the max power on each at full excursion (at 10Hz, which may not be as realistic as say 15Hz or 20Hz, but you would then need a HPF to get full excursion)...

ibforotto6.jpg

Here is the SPL difference with 4 drivers each at their full excursion...

ibforotto5.jpg

Now that will be very noticeable provided you can get to a 4 ohm load so you can bridge the EP2500.

Whether or not you can stay in the house with it or not is another story... :hsd:

What parameters do you mean?
TS Parameters
 

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I refigured these with max power to reach excursion using a HPF.

You can run max power of 2400 on all of them other than the MJ's... which max out at 1500 watts.



 

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We got Fi Audio's parameters worked out and interestingly Scott has produced a killer IB sub...

This is max power and max excursion, however, you will not reach max excursion on 4 IB Fi's with 2400 watts and no HPF is needed.

ibforotto10.jpg

ibforotto11.jpg

Here's your 4 vs. 2 IB Fi's...

ibforotto12.jpg
 

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Discussion Starter #17
Wow, Sonnie, I really like that! What model is it? I see you have it listed as "Fi IB18" on your model, but I don't see the IB18 on their site. It looks like they have BTL, BL, Q and SSD models. I know you're not their rep, but maybe you know...

Thanks again!
 

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Discussion Starter #20
OK, so I've looked through all of Sonnie's plots (thanks a lot for doing those, Sonnie!). I like the SS RL-p18 and I like the Fi IB18. Anyone want to interpret the graphs or split hairs between those two? There is a pair of RL-p18s up for sale for about $300 each shipped, or I can get the Fi for something like $209 + shipping.

Help me decide! Which is really the better driver?

Thanks!
 
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