Infinite Baffle: Looking for advice re: Manufacturing an OEM 18" for IB Applications

[andrikos]

Hello everybody,
I am working with a subwoofer driver manufacturer to build an OEM 18” driver for Infinite Baffle applications. This is not a full time endeavor for me nor am I in the ‘business’. I do have a day job and this is basically a side project for me. I’m not in it for the money, that’s why I expect to be able to offer the best $/liter displacement ratio in all of wooferdom. I’m doing it to prove to myself that I can do such a thing and in the process help the community use a driver that is specifically and exclusively designed for IB applications.


The main parameters we’re trying to hit by order of importance are:

Xmax > 20mm (more is obviously better but we’re also looking at linear, low distortion performance)
Fs < 20Hz
18” driver – Sd = 1400 – 1500cm^2. We feel that an 18” driver gives us the best chance of hitting our goals.
MAX SPL: >98dB at 10Hz, 110dB at 20Hz, 116dB at 30-80Hz unechoically per driver. Each doubling of driver number will add 6dB to this number. Room gain should add about 20dB more to the above numbers give or take, YMMV.

Pe = 500W single coil
Qts = 0.7- 0.8 (flat response for IB applications, not recommended for small enclosures sealed or ported).
Vas > 500 liters
Neodymium magnet
Foam surround (new and improved stuff not the foam from the 70’s and 80’s)

Our goal air displacement volume is >6 liters.
Our cost goal is <$50 per liter so as to have the most cost effective IB driver out there that is specifically designed for Infinite Baffle operations.

I do not care about aesthetics, bling factor etc. Every single cent will be dedicated towards PERFORMANCE! No fancy graphics/materials just to make a silly statement (i.e. this is NOT an automotive application focused driver )

This driver is aimed to DIY audiences that have the education, knowledge and experience to do a simple IB install with 1 or multiple of these drivers for UNPARALLELED bass performance.

For those who know IBs, the advantages are numerous and overwhelming:
1) Far lower cost than any commercially available subwoofer of an topology
2) Very simple structure (no fancy, expensive boxes required)
3) Out of sight, out of mind – High WAF
4) Did I mention the bass ROCKS? The house shakes, creaks and groans. Little children and puppies whimper in the corner. Neighbors file police complaints. You get the idea…
5) Perfectly blended and natural bass to the rest of your system.

Why am I writing this? Since I’m not a manufacturer, I would like the input of experienced IB owners and enthusiasts that are excited at the possibility of installing an Infinite Baffle in their home theater for a low cost. I’m a huge bargain shopper and the next step for me is to actually MAKE the drivers I want to buy. My potential ‘customers’ are NOT audiofools who spend $17k on a coffin sized sub with an undersized set of ports. My ‘customers’ are regular working stiffs like me with ‘real’ salaries and ‘real’ constraints because they need to include diapers and formula in their budget…

I hope my post wasn’t toooo long.
I’m looking for advice, desirable features, do’s and don’ts, lessons learned etc. etc.
I appreciate and thank you in advance for your feedback.

Andreas

[AJinFLA]

You might want to start here:
http://home.comcast.net/~infinitelybaffled/
http://ibsubwoofers.proboards51.com/

FYI, a driver with Sd 1400-1500cm^2 and a surround capable of over 20mm excursion, will be larger than 18".

anechoically speaking

AJ

[andrikos]

Thanks AJ, you're right about the Sd part.

[johninCR]

A pair of IB 15's will meet your performance requirements for only about $200. Also, Hawthorne Audio is coming out with an 18" cast frame driver built by Eminence specifically for IB. They're sticking with the pro heritage and going with the Definimax cloth surround, so Xmax is only 14mm, but over excursion shouldn't be a banging nightmare.

[Paul W]

One suggestion... Before latching onto a Neo magnet spec, have your OEM supplier quote both Neo and ceramic, and then check freight costs. Ceramic might give more "bang for the buck" in driver cost but, considering shipping costs, maybe not the best overall business decision. Look for the best tradeoff before you leap.

Just personal preference, but I'd go with a little lower Qts.

[paulspencer]

How about 15" versions? It makes sense to build in multiples of 2 so they can be push pull and transfer less vibration to the structure. A single 18" requires a more solid structure to prevent vibration problems than a pair of 15" drivers mounted in this way. Perhaps some price incentives to buy a number of drivers ...

[andrikos]

Thanks for the suggestions so far.
If this thing flies, we'll definitely go the 15" route.

[AJinFLA]

There is plenty of competition in the 15" range.
The number of 18" neo subwoofers with over 20mm xmax - is one (that I am aware of). And it ain't cheap.
My only suggestion (other than a nice open basket) is an aluminum cone.

cheers,

AJ

[theAnonymous1]

A 15" driver is a lot more "application friendly", but if you use an 18" driver you will naturally end up with a lower Fs which is in my opinion the second most important spec of a IB sub, first being Qts.

[andrikos]

The main reason 15" will be offered too is to offer more options to the end user.

If we can make a 21" ultra-woofer for extreme applications, we'll do that too.