Looking for advice re: Manufacturing an OEM 18" f

[andrikos]

Yep, this is the perfect place to ask for advice on this...
Thanks, Thomas for the referral.

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

[ThomasW]

Thoughts....

Lower Qts. Why? By the time room gain does it's thing the world can get a little boomy with higher Qts drivers. Since IB's give us Qts=Qtc, it's nice from a SQ standpoint to target Q of 0.5 = critically damped vs maximally flat = 0.707. One can always use EQ to make a low Q driver sound like a higher Q one, the opposite can't be done.

Don't get all hung up shooting for high efficiency. IB's are inherently the most efficent subs around as frequencies go lower. These days amplifier power is cheap, and since Mr Hoffman's laws always win, there are other places to put your emphasis...

Quite a few years of experience have shown us that multiple drivers are far and away the best choice. The only time a pair of 18"'s have been sufficient, are ones when the Xmax is in the 27mm range.

Shorting rings are always nice....

Neo magnets are $pendy, and primarily beneficial when one needs a small magnet 'shadow', and a high BL That's probably not an issue with a 18" driver given the size of the rest of the assembly.

The +6dB per doubling of drivers is directly contingent on there also being a corresponding doubling of the output power from the amp

[carpenter]

I thought it was 3db per doubling of drivers...

btw, are we trying to make the enclosure Q match the Qt of the driver? Sorry in advance for asking if this info is available in the FAQ... ;D

Well, I googled Qtc and see that I asked a rather foolish question. Sorry. I would enjoy reading anyones comments on the relationship of driver Q and the enclosure environment.

John

[andrikos]

Great feedback Thomas, thanks a bunch!
I'll convey that to my manufacturer.
Any inputs about the cone material? Is it critical at such low frequencies as long as it is sufficiently rigid and non-distorting while in pistonic motion?
The moving mass would have to be in the 300-400g range to achieve a n Fs<20Hz.

Keep them coming, great stuff!

[ThomasW]

I thought it was 3db per doubling of drivers...

There's +3dB from acoustic coupling, and another +3dB if the amplifier doubles it's power with the added driver

Well, I googled Qtc and see that I asked a rather foolish question. Sorry. I would enjoy reading anyones comments on the relationship of driver Q and the enclosure environment

home.comcast.net/~infinitelybaffled/page13-10timesVas.html

Any inputs about the cone material? Is it critical at such low frequencies as long as it is sufficiently rigid and non-distorting while in pistonic motion?

The standard for non-bling drivers is Kevlar epoxied to a pulp cone. Reasonable cost and very stiff.

[carpenter]

There's +3dB from acoustic coupling, and another +3dB if the amplifier doubles it's power with the added driver

Very interesting... and you taught me something new to boot. let's say you are running stereo woofers--does the addition of the second channel contribute 6db even though it's on a separate amplifier? I would think yes, because the available wattage doubled.

All the speaker software I use shows +3db when the area doubles. I never considered that the boost in amplifier wattage added another 3. Thanks for the knowledge and for so kindly referring me to the FAQ regarding Qtc.

I don't mean to circumvent the primary point of this thread, but...

There is another concept I'm curious about: when modeling speaker performance, is it safe to stop enlarging the box volume once the software depicts the 0.5 Qtc point? This is important to those who have limited space; also, some woofers may be quite content in a smaller enclosure.

John

[ThomasW]

There is another concept I'm curious about: when modeling speaker performance, is it safe to stop enlarging the box volume once the software depicts the 0.5 Qtc point?

It is if your primary goal is a Qtc of 0.5 for a small sealed box.

This is important to those who have limited space

If you're modeling an IB, run the largest box possible and forget about having a target "Q".

Actually there's little point in modeling an IB. If one has less than 10 times Vas, lets say 4 times Vas, then buy the lowest Vas woofers that fit the other T/S criteria for an IB. Even an IB that's technically 'too small' will sound better than a small sealed box tuned to a Qtc of 0.5, or one forced to a Qtc of 0.5 with an LT circuit.

This is a long way of saying that an IB with a "Q" of 0.5, doesn't 'sound' like a small sealed box with the same "Q".

[gottavtr]

It would be great to still make it easy on the eyes. Some of us like to show it off in a line array.

[fvoelling]

Andreas,

First of all thank you for your efforts!

I became interested in IBs about 6 months ago, and at the time there was talk about an upcoming 18" IB driver around $200. Well, I'm still waiting, and even yours sounds like it might be closer to $300. Now if the performance is such that two drivers would suffice, up to $300 would be ok, but having to buy four would exceed my targeted price range ($1000 for the complete system including amp, materials, and drivers).

Aside from cost, actual product availability in the very near future would be nice! Why does a new driver always just seem to be a "couple of months" away, with none to actually materialize in my 6 months IB experience?!

My buddy is coming to visit us for a few weeks starting the end of July, now there's your deadline !

Frank

[andrikos]

Hi Frank,
Thanks for your positive comments.

I think the main problem with supply issues is the lack of a profitable market for these things from a manufacturer's perspective.
Since I don't care about cost, it shouldn't be a problem!
We'll see...

[formica]

fvoelling said:

Why does a new driver always just seem to be a "couple of months" away, with none to actually materialize in my 6 months IB experience?!

I think alot of people underestimate the time involved in tweaking a new product and raising enough capital (pre-sales or whatever) to produce them...
ROb

[andrikos]

I have FANTASTIC news from my OEM!!!

Here are the parameters of the prototype driver (plug them in to your favorite subwoofer simulation software and compare them with ANY driver on the market! )

Fs = 14.5Hz
Qts = 0.42
Qes = 0.52
Qms = 2.14
Vas = 926.7 liters
Mms = 232.7g
Re= 4.5ohms
Le = 1.56mH
SPL = 89.2dB
Res = 40.9ohms
Rp = 18.3ohms
Rms = 9.9Kg/s
Cms = 0.51mm/N
Cp = 1487.2uF

Saved the best for last…

Xmax = 35mm!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Sd = 1123.3 cm^2
Displaced volume = 7.864 LITERS OF AIR!!!!!!!!!!!!!

Keep in mind all these are preliminary and maybe I’m jumping the gun a bit as the parameters may change a bit. But this is the driver we’re working on. Amazing stuff!!

As soon as I get the prototypes, I’ll put them in a MONTH-long burn-in in a lab and a real world environment (club, disco, etc.).
Only after reliability of at least 10 samples has been proven, this will be offered for sale.

You have no idea how excited I am! This is absolutely amazing. My OEM have been working solid on this and have delivered BIG TIME!

This is it, ladies and gentlemen, I’m awaiting for your inputs, comments, criticisms, suggestions, etc. etc.

Thanks,

Andreas

[jeffp]

If those specs hold true that would be amazing. Are they going to be DVC to support the additional wiring options?

Send me 4 to replace my 15's and I'll give you my review ;D

[hdjunkie]

Ohhh I want 4 too !!!!

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.


Does this mean $350 - $400 ea?

[andrikos]

jeffp said:

If those specs hold true that would be amazing. Are they going to be DVC to support the additional wiring options?

Send me 4 to replace my 15's and I'll give you my review ;D

So far we're going with a single coil but I'll ask my OEM to see how much it would change the parameters/cost of the driver.

Hey, if there are adventurous people out there willing to test a Beta (or even alpha!) version of the driver, that'd be great.
I'll see what I can do.
Obviously you'd have to write extensive and objective reviews if you were to do this.
Also, I'd basically sell these at cost to get the benefit both ways.
I'll let you know shortly.

[andrikos]

hdjunkie said:

Ohhh I want 4 too !!!!

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.


Does this mean $350 - $400 ea?

Hopefully much less than that especially with multidriver orders.
I don't have any cost data so I cannot commit to any price but, rest assured, that if this driver doesn't DESTROY every other on the market in $/L ratio and performance, then it's a no-go.

At 7.864 liters of displaced volume we have:

$393.2 at $50/L
$353.9 at $45/L
$314.6 at $40/L

At ~$1,200-$1500 worth of drivers you get ~32 LITERS of woofage!
Try and beat that!

[Darrel]

I don't have any cost data so I cannot commit to any price but, rest assured, that if this driver doesn't DESTROY every other on the market in $/L ratio and performance, then it's a no-go.

At 7.864 liters of displaced volume we have:

$393.2 at $50/L
$353.9 at $45/L
$314.6 at $40/L

At ~$1,200-$1500 worth of drivers you get ~32 LITERS of woofage!
Try and beat that!

Hey Andreas,

I'll take that challenge and stand behind it with proven customer service from an established company and an industry leading warranty.

Best regards,
Darrel

[chrisbee]

What do you consider the potential advantages of developing twin coils over a 4 Ohms single coil?

Does delaying production appeal more than getting your hands on a set of affordable 18" in an almost perfect IB driver vacuum?

[toecheese]

Get these drivers out- I've been wanting to get two more Tempest 15s, but can't seem to find them anywhere, so I'll settle for pulling mine out and getting two 18"s.

[andrikos]

I'm working as fast as I can, but this is a brand new endeavor for me.
Please be patient.
I'll be updating you real time.