[bassboy]

http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=299-810

I just noticed them yesterday and couldn't help it.  I tried to resist but today I ordered 4 of them.

Shipping (to Canada) stings a bit, since the shipping costs more then the drivers, but even with exchange rate, shipping, brokerage, customs, etc, I expect to hit the $40/driver (or slightly less) mark.

Other than about 3 db less sensitivity, these look very similar to the alpha 15 in xbaffle sims.  They have 2x more xmax than the alpha 15 though.

[slbender]

Quite good 15" driver for that price.  Too bad they don't have something similar in a 9 1/4" woofer, I built my own speakers about 24+ years ago using French woofers from Audax, that are discontinued for decades already. To replace them, closest thing would be the Morel HU9.1 9" Cast Frame Woofer, at 9.1" and $315.. per pair plus shipping.

An 8" driver would fall into the hole, while most 10" would not fit, or overlap the midrange by a small bit if it could be made to fit.  While 10" woofer could maybe be put in with some wood adjustment (read: 20 hours work on each box with a file to make the box mounting hole slightly larger) guess I'll still keep gunking up the original Audax drivers with heaps and blobs of epoxy keeping them together.

-Steven

http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=299-810

I just noticed them yesterday and couldn't help it.  I tried to resist but today I ordered 4 of them.

Shipping (to Canada) stings a bit, since the shipping costs more then the drivers, but even with exchange rate, shipping, brokerage, customs, etc, I expect to hit the $40/driver (or slightly less) mark.

Other than about 3 db less sensitivity, these look very similar to the alpha 15 in xbaffle sims.  They have 2x more xmax than the alpha 15 though.

[iON]

A small headsup: foam surrounds!

None the less, good OB parameters and incredibly cheap!

[Michael V]

A small headsup: foam surrounds!

None the less, good OB parameters and incredibly cheap!

I realize foam is probably not suggestive of high quality generally, but what effect is that likely to have on bass response? 

Thanks

[iON]

Michael: It will not have negative impact of the bass respone. Until the test of time has begun that is. Polyester foam rot is a known problem. Having owned drivers where the surround rotted away I'd hesitate before buying "future problem" again, if you know what I mean.

Anyway, since they're supercheap(tm) perhaps one can overlook the foam surrounds. I mean they could still be useful for concept prototypes, happy experimenting (isn't that the essence of DIY!), party speakers or something

PS: There is also polyether foam which supposedly is magnitudes better than polyester in terms of durability. It is however much more expensive and you seldom see it (definitly not on cheapo drivers anyway).

[mcgsxr]

Interesting find, and glad to see a fellow Canuck doing some experimenting!

Higher QTS than what I see typically, though you are right, they are close to the Alpha in that regard.

For the dough, I am sure you cannot better them as an experimentation jumping off point.

Keep us in the loop!

[bassboy]

I got them today and have to say I am very disappointed.   I guess you can't expect much for $17 but they really did look better in the picture than they do in person.  The baskets are made of the thinnest gauge metal I've ever seen used on speakers and they ring like a bell when tapped.  The baskets are not painted and look awful, they looked painted in the picture.  The cone is equally bad looking paper (did I mention it looked better in the picture?) and the area in and around the pole piece is corroded.

No word yet on how they sound, but even so I already don't recommend them.

[gitarretyp]

I'd recommend checking the drivers actual Xmax. There's a good chance the rated Xmax of 7mm is peak-to-peak on these drivers. In which case, they have less linear excursion than the ubiquitous Alpha 15.

[WerTicus]

They look like crap from the picture to me, thanks for trying it out for us and saving (our) time.

[bassboy]

I thought the pic looked pretty cool, they don't have a big lip around the rim and seemed to look similar to peerless drivers in that regard.  (There is a tiny bit of a lip, but since it's not painted, it either needs paint or to have the big foam rim ring that comes with it glued on)

Anyway, they cost me almost $40 each, so I WILL be taking the time to try to make them a bit better.  I've got some ideas on strengthening the basket legs, and then damping as much of the basket as possible (legs included) with ductseal, and of course they are going to have to be painted before any of that.

At this point I've tested only one of them and then buried them in the back of the closet so I don't feel the sting of the credit card payment every time I look at them.  In 6 months or so I'll pull them out and fix em up.

At this point, I'd say IF you plan on doing a bit of diy on the driver and IF you live in the US (due to shipping costs) and IF the drivers are not visible when in use then these might not be a bad for an extreme budget product.  They still fit into my OB philosphy quite well, I just wouldn't pay $40 each if I had it to do again.

The weak basket and unfinished appearance are my main complaints and I think I can fix those, for the most part.

MY OB PHILOSOPHY
The is no replacement for cone area.

Displacement only goes so far.  Beyond a few mil excursion, even the better OB bass drivers are going to make all kinds of noise, so you can have 30 mil xmax all you want, you won't be able to use it, the vent noise is going to scream like a little girl on the first day of kindergarten.
Total q doesn't matter much if you have a decent eq.
FS still matters a lot, but even that can be overcome with eq (18 db/oct worth of eq below fs), and plenty of cone area.

All these specs are important but cone area rules and these have plenty of cone area.  Not much else going for them, but they got lots of cone.

[Graham Maynard]

Hi bassboy,

I like your philosophy/summary.

If you built your drivers into a Ripole then their looks would not be a problem, also outer frames steadying the magnets would further reduce basket resonances.  Just an idea.

Cheers ....... Graham.

 

[scorpion]

I would like to point to my thread below about MJK's Bass Study: http://www.quarter-wave.com/OBs/U_and_H_Frames.pdf .
According to MJK's simulation models two Sonavoxes in an H-baffle double the heigth of MJK's and same width would produce like this with 125 Hz LP L-R /12dB/oct filter:



/Erling

[tubamark]

Hi bassboy,

I like your philosophy/summary.

If you built your drivers into a Ripole then their looks would not be a problem, also outer frames steadying the magnets would further reduce basket resonances.  Just an idea.

Cheers ....... Graham.

 

Overall a good idea, but I expect that this driver's Qts is too high (1.31!) for a Ripole, which would make the Qts even higher yet . . . How much higher is hard to say.
Perhaps a less-compact W-frame would work fine.

I know that one can typically expect a decrease in FS by ~10 Hz, assuming frame exits at 25-30% of total Sd . . .
But does anyone out there know a rule-of-thumb for the increase of Qts in a ripole?  'Could be more involved to predict, as a Ripole changes Qts indirectly by changing Mms (moving mass).

--- Mark

[WerTicus]

I thought the pic looked pretty cool...

Really? I have fridge magnets that are larger than the magnet on this driver.

This is what a good 15inch woofer looks like
And before you say 'well this driver costs 100x the price' I know, but that is why it costs more, because its good

Anyway im not trying to rip into you, i'm just suggesting that skimping on drivers is the wrong way to reach your goals.

A sound system worth 2k where the speakers are worth $1900 and the amp, pre amp, and source are worth $100 will sound a million times better than a sound system worth 2k where the speakers are worth $200 and the amp, pre amp and source are worth $1800 because speakers are where 99% of the distortion come from. Where as you can just hook up an ipod and a class T amp and till have a signal with only 1% distortion.

Basically I am saying the speaker and its components are the most important part of a sound system, because they colour the sound more than anything else.

[Graham Maynard]

Hi Mark,

If high Qts at a low frequency turns out to be a problem then it might be possible to reduce the Ripole Q by fitting expanded aluminium grilles to resistively load chamber air motion.  
As long as higher driver Qts does not develop within the wanted passband then it might not be much of a problem anyway.


Hi Werticus,

But expensive power woofers are not automatically suitable for use on dipole baffles and in ripole housings.  Cheaper drivers can actually sound better because they can still displace air without needing to generate high pressures below 50Hz (where the highly resistive power woofer suspensions limit amplitude).
For dipole pattern reproduction at LF, and where cone suspensions must be very compliant at LF, we specifically do not want the kind of driver you show.


Cheers ........ Graham.

[WerTicus]

how about these GR Research woofer (cheap at $150, they have a circle here)  but only 12inches however they are designed for open baffle use

 
and they actually look the biz, in terms of construction.

Hrmm actually they are more subwoofer rather than woofer.. 20hz - 150hz

[speaker]

I got them today and have to say I am very disappointed.   I guess you can't expect much for $17 but they really did look better in the picture than they do in person.  The baskets are made of the thinnest gauge metal I've ever seen used on speakers and they ring like a bell when tapped.  The baskets are not painted and look awful, they looked painted in the picture.  The cone is equally bad looking paper (did I mention it looked better in the picture?) and the area in and around the pole piece is corroded.

No word yet on how they sound, but even so I already don't recommend them.

Much of the ringing will go away when they are mounted and screwed down and what doesn't can be damped with a Dynamat-like product.

[bassboy]

WerTicus - I'd encourage you to look at it from a different perspective - $ for $.

The 12 inch OB driver you posted and quoted at $150 costs about 9x more than the ones I bought, giving your driver about 15x less overall cone area $ for $.

Additionally, your driver WILL need eq, mine doesn't.

Scorpion, Mark and Graham - thanks for the graph and the suggestions.  I think Mark might be right - ripole might be a bit too much of a load for these drivers, given their already optimal qts.  As the graph shows, there is a slight dip in response around 40 - 50 hz which indicates that an H baffle is about the most load you would want to give them.  Tuning lower is just going to make that dip worse.  BUT...

I'm not completely sold on any alignment but pure dipole yet and need to do some physical testing.  Everything I've read leads me to believe that most people seem to favor the flavor of true dipole over these other variants, and people are only using the U's and H's and ripoles to move the fs down and qts up slightly, which of course is going to lower the sensitivity.

You can accomplish exactly the same thing by adding mass to the driver cone and still use the pure dipole alignment.  So why wouldn't you?  It's a whole lot easier than making U's, H's and ripoles.

[mcgsxr]

As a guy who has played around with OB bass for a couple of years now, I would add this:

1 - the 12 inch woofer quoted appears to be a great unit, and should be considered by people thinking about OB bass - it often helps to start with a driver where the specs all point in the right direction, for a simple implementation.
2 - DIY Cable also has a very nice 15 inch in the same price point, that I would consider.
3 - Dmason has pointed out the very nice 15 by Acoustic Elegance
4 - Dayton builds a nice 15 for IB use that would be very easy to implement in OB
5 - I have found the Mach 5 Audio 12's useful, and wish I had pony'd up for the 15's at the time...
6 - lots of folks happy with their Eminence Alphas too
7 - The Hawthorne Auggie is also clearly a good option
8 - looking for cheap drivers with the relevant QTS, FS and XMAX metrics is always rewarding - you can implement to save $, or maximize swept area by buying more if you have the space!

As for the "true" dipole vs H, W, ripole etc, I think it often comes down to space - my OB are around 36 inches wide, and even with the wings folded in some, they are HUGE in a room.  The ability to retain 90% of the sound, for 40% of the footprint would be VERY useful should they ever have to live outside my dedicated room.

[scorpion]

bassboy,

I do like your reasoning. Going Ripole or Linkwitz' Phoenix W-pole should be considered for drivers around 0.7 Qts or a little less and fs around 40 Hz. These will perform beautifully in this kind of houses. Your units will perform best in plain OBs or like I hinted at H-units. Judging from MJK's simulations the Sonavoxes would do about in simulations as good as Eminence Alpha15s but with lesser output and going a bit lower.

/Erling