Well as many of you know I'm still on my never ending quest to find a single subwoofer I like the sound of and I may have come the closest yet yesterday.



We took delivery of the new Image Dynamics IDMAX12 (12") during the week and installed it over the weekend ready to begin it's run in session. I have heard many comments about the IDMAX12 not being overly good for sound quality tasks but I have long suspected this is due to the sheer size of the motor structure and the fact it needs some serious power to control it. So far I have been right.

For some interesting reading, the stats of the sub are:



The installation and environment specs are:

* 1.3 cubic foot sealed enlcosure.
* 36mm MDF walls with internal bracing.
* Zapco Reference 1100.1 amplifier.
* Crossed at 65hz with a 24db slope.
* No boost.

Once run in it was time. We finally gave it a real workout this morning for a little while and I must say the bottom end frequencies are absoultely fantastic! Control at subsonic and lower subbass frequencies is second to none and while obviously the amplifier primarily governs this, no other main stream (ie not specially manufactured for us) subs to date has sounded so clear and controlled. Everything from basson, cello, pipe organ and percussion drums, not to mention techno, dance, pop and metal (didn't have any RnB on hand sorry) sounds suprisingly tight and accuarately defined.

To answer what the SPL heads are already starting to answer, don't stress; when you crank it up, your head turns to jelly and you cannot see - all this from a single 12".

Now next week I should have the brand new RE Audio XXX 12" instaled which I'm lead to believe is even better than the IDMAX but for now, this is one oft best 12"s I've heard in a ling time.

Anyone want a listen, give me a ring. :D:D

there a damn nice speaker. you should try having 2 in a SPL box burping away while driving damn fun stuff

Yeah, I have a ported enclosure lined up in a few weeks for more testing. You reckon I'll blow my head clean off?

not clean off bit of tearing will be involved haha

i won my first SPL trophy with one of these

Just added some images.

Morning Marty
Do you ever sleep :hehe:
What amp are you using to push this baby :?:

they're most definately an awesome sub, personally i think the 10" is the pick of the bunch for SQ, same with the XXX's....
the XXX12 is dearer, so it's not really a fair comparison though

Hey John, it is currently running of a Zapco Reference 1100.1. See here for more details on the test car.

hey marty

how does it compare to a DD3512, which is also in a similar price bracket?

- Stooge007 out

welcome to the family SON !

It need more time to break-in...it should sound sweet after the break in period.

Hey FHRX great read maybe you should post your thoughts on other stuff as it would be a great comparision tool.

Hey FHRX

Mabe you can add some info into the post, as marlin suggested. Some info on what subwoofers you have listned to, etc. What was lacking from each, info like that.

Have you listened to an adireaudio tumult ? I wouldnt mind knowing how they compare

I dont mean to be a pain but i would love to see a Soundstream Van Gogh 12" SQ sub tested. See how it compares.

I still think a Brahma or XXX sound a bit better than the IDMax'x, they ID's dont have the flat BL response of the XBL2 motored subs... but then i guess the Brahma/XXX's are a whole lot more $$$, and the advantage to not using the XBL2 motor is you get better sensitivity, hence why IDMAX's are always regarded as an exceptional 'Loud SQ' sub

At what volume? I mean if still kept in its linear range, then the distortion would be low, so the overall BL curve would not be an issue. So a XBL2 motored subwoofer would not automatically sound any better. The IDMAX is still a pretty decent sub IMO.

Secondly, since when does having a XBL2 motor have anything to do with sensitivity? I mean the BL of the Brahma (for example) was likely specifically chosen, rather than forced to be at that level due having a XBL2 motor.
The bandwidth (F3 in a given Qtc enclosure for example) and required enclosure volume has a bit more to do with the sensitivity though.

The whole point of the XBL2 motor is the motor strength is the same at near full excursion as it is at rest point. The IDMax's are like most subs, the motor strength deteriorates the further the cone moves from resting towards its XMax... i'm not saying they sound bad, they sound bloody wicked, but i still like that silky smooth Brahma sound BTW, apparently BL non-linearity accounts for 70-80% of subwoofer distortion (or so i read somewhere, may have even been Dan Wiggins saying that


For a given magnet size and strength, the XBL2 tech will have less sensitivity, simply because they have to remove some of the magnet internally... its hard to increase the strength of certain areas of the magnet by changing the magnet composition, so both the Brahma and XXX start with a huge magnet and remove some areas of the magnet at strategically located areas to reduce the motor force slightly at those areas... thats how they get the flat BL Which means better SQ but less SPL I'm not saying you cant have a high sensitivity XBL2 sub, just that for a given magnet size the XBL2 motor has less sensitivity, hence why the XXX and Brahma's have utterly massive magnets

The whole point of XBL2 is a to optimise the motor for a longer linear range for a given coil height and top plate height.

I agree that BL non-linearity is a significant contributor to subwoofer distortion. Obviously, within a particular range, the BL spec will not deviate that much, regardless of the motor topology. Hence why I said "At what volume? I mean if still kept in its linear range, then the distortion would be low".



They don't remove any of the magnet. It is the gap that is altered. This will of course have an effect on the BL, but the resulting BL value (at whatever point on the curve) depends on the optimisation of the motor. In fact, in one of the technical articles on the Adire Audio website there is a comparison of the split gap design vs a long gap long coil design, with the same basic parts, only a different voice coil (XBL2 motor had a shorter coil) and obviously a different gap design. The gap width, magnet and top plate height etc all remained the same. In this example, the XBL2 motor had a larger BL value at all points on the BL curve.

But the fact remains, the resulting sensitivity spec of the Brahma, is likely a side effect of optimising the driver for a particular frequency response in a particular size enclosure. Dan could have made the BL (for a given coil resistance) a lot higher, if that was his goal.

Feel free to ask Dan to clarify. If I am wrong, then post/get him to post his reply here and perhaps I will learn something. :wink:

OK, yeh my bad, i knew they made a hole somewhere from reading the tech paper but i thought it was in the magnet, tis in the top plate like you said

[web:61ffaf6599]http://www.adireaudio.com/Files/XBL2DetailsPaper.pdf[/web:61ffaf6599]

IMO the sensitivity is reduced in XBL2 drivers as the the large excursion involved (64mm p-p) requires a large roll surround which decreases the effective piston area and thus reduces efficiency.

i also guess that due to the low frequencies that they're also designed for, the spider need to be fairly stiff to retain control at high xmax.
but i may be wrong on that one

This is also a good point. For example, the difference in efficiency between the large surround of the 12" brahma is probably somewhere around 0.8dB less than the smaller surround on the shiva.

Yes, decent suspension is definitely required to prevent coil rocking at high xmax - no point having a large linear BL range, if the coil ends up scraping at high xmax.....