[Kevin Haskins]

This one is done and I'm placing my PO for it this week.   Expect availability May 14th.

The design idea was a simple one.   We wanted a high output Dipole/IB driver that not only broke the value barrier in terms of $$/L of displacement, it had to utilized Dan's XBL^2 motor design and the AlCu inductance tricks to minimize inductance non-linearities and flux modulation under dynamic peaks in the program material.   Its a tall order to both hit the value mark and still produce a world-class motor design but we managed only slightly over budget coming in @ $125 each.  Slightly less in 4 & 8 packs.   Expect to see shipped pricing in the $30/L of displacement range.

This is a single 8 Ohm VC design, in most cases being used in pairs to achieve a nominal 4 Ohm load.   The VC is a 2.4" all copper design with black anodized aluminum former for maximum power handling.   This is huge overkill for this design as it doesn't take much power to get it to full stroke in its intended application, but what the hell, it didn't cost much more and power compression will be a non-issue.

The motor is good for about 22mm X-max, that being the 30% down point.    The 10% down is out to 18mm so we have plenty of linear BL.   Why not more?   For three reasons.   First, in dipole designs low noise is important.   As you design a driver with more and more stroke the noise generated by the suspension & air movement around the basket and through the pole vent start to become an issue.   There are practical limits to what can be done to minimize these effects and we find that designing a driver with more stroke gains you very little when the mechanical noise starts to become a limit for dipole use.     The second reason has to do with Sd.   For high stroke designs you need a larger roll surround, which eats away at some of your cone area.    By keeping the stroke reasonable we could use a relatively small roll surround keeping Sd high while keeping self-noise under control.  The third factor was the driver weight.   We wanted a driver that was light weight, under 20lbs to keep shipping cost low.   These drivers are going to come in around 18lbs so shipping for 4 & 8 Packs is HALF the cost of shipping the same number of Tempest-X in many cases and with the higher Sd, the total swept volume is 3.65L which is still a healthy number for a 15" driver.

Pre-Production Parameters:

Re: 6.1 Ohm
Le: 1.7 mH
Fs: 19.5 Hz
Qms: 3.27
Qes: 0.84
Qts: 0.67
Mms: 271g
Cms: 0.23 mm/N
Vas: 232L
Sd: 830 cm^2
Vd: 3.65L
BL: 15.67
SPL: 85.2 1W/1M
X-max: 22mm
X-mech 29mm
 

Motor Design:



And here is a rather crude picture that needed a lot of Photoshop work to even post.      The red cast is because the background was red in the original picture.   It was hurting my eyes so I changed it to blue with some PS work.

[mcgsxr]

Oh mama, I am going to have to get a second job, a quartet of these babies may just end my search for perfect OB bass... aa

[macnewma]

What kind of upper usable limit will these drivers have?  Have you tried them in any open baffle setups?  My application would be upper bass/midbass.  I would probably low pass them around 300-400hz.

[Kevin Haskins]

Once I have production units I'll build a couple baffles and get measurements.    Should be good on-axis out to about 1K but you really have to measure them on the baffle your going to use.

[ttan98]

Kevin,

At about 86spl per unit, with 2 units per side, running in parallel in OB config.,what is the min power required to drive then to reasonable sound level? 100W, I suspect much higher.

[Kevin Haskins]

Define reasonable, the baffle width and the bandwidth.   

The driver sensitivity is driven by the Mms (moving mass) and BL (motor strength).    We could increase sensitivity by decreasing the moving mass.    While doing so, the Fs would raise and the Qms drops along with Qts and the unassisted bandwidth of the driver goes way up.    If we leave the mass the same, and increase the BL we get the same result, except now the Qes & Qts of the driver drop, killing the bandwidth.

So.... the short and dirty on the sensitivity story is that its determined by your choice of bandwidth.    A lot of people argue that you should start with an efficient driver and then equalize it to gain the low frequency bandwidth.   The result is that you still need the SAME amount of power as you did with the less efficient driver to achieve the same bandwidth.   The efficiency is up at the higher frequencies, not where we designed the driver to operate (the first 2-3 octaves).   

So, would you rather have a 91db/1W/1M driver, that cost 50% more (needs twice the motor),  that needs active equalization,  and lots of power, or would you rather have a driver that DOESN'T require equalization, can use any power amp sufficient for the job, and achieves the same thing?   Both require the same power in the first & second octave.   One solution cost much more and is much more complex.

Its a fairly simple choice from where I'm looking.   

I'd say the F500-TS is a perfect amp to drive four of these.   That gives you 250W per driver (four drivers, two per side) and by my calculations you should be able to hit the full excursion of the driver in free-air @ 23-24Hz.     That is PLENTY of output, much more than your going to see from most dipoles.    By that time your getting a lot of driver noise from the excessive excursion anyway.    If you need that kind of SPL your better off going up to 4 DPL-15s per side.   

     

[EProvenzano]

Oh mama, I am going to have to get a second job, a quartet of these babies may just end my search for perfect OB bass... aa

Hi Mark & Kevin!

Mark, I know you have some experience with the B200 drivers.
Do either of you know if these OB woofers would be a good candidate to fill in the falling response of the (unequalized) B200?

I'm curious if I could easily whip up a large WMW open baffle using two of these new woofers flanking the B200 in the middle of a 20"w x 60"h baffle?

I imagine I will need to apply a low pass filter, and possibly still a high pass filter on the B200's.  I have not experimented with equalizing my B200's because I knew one day I would want to augment the bass, so unfortunately, I have no experience with adding these seemingly simple cross-overs.

Thanks 

[mcgsxr]

Eprovenzano - I won't speak for Kevin, he likely has forgotten more about drivers that I will ever know, but I have stated my belief that this will be a beauty to implement for OB bass, if you keep "sensible" goals in mind.  Kevin astutely points out that the implementation is critical, but I will go on record saying that all the relevant specs (the combo of QTS, FS and XMAX, and swept area) all look really strong for this to be a great performer.

I do indeed use a set of b200's (no EQ on anything but the bass in my system) and leverage one of these from Reckhorn to split the upper and lower frequencies - http://www.reckhorn.com/index.php?ln=en&prod=f1 - they are cheap and cheerful from Bob at CSS in Canada (less than $80).

From there, the bass frequencies are run through an old analog EQ I have, then onto my sub amp, then out to the 12's I use (1 in each baffle).  Very simple stuff, just a little tough to express in the written word.

I would recommend a MWW arrangement, to better leverage floor boost (the upper woofer in a WMW would be quite far from the floor) and I would think a simple U baffle would work wonders with this driver.  There is a thread in the Open Baffle circle right now, where someone has posted a link to Martin King's musings on a passive OB bass solution (it points out how baffle width and depth in a U or H will affect efficiency and extension) but it is very simple to apply to active installations too - the efficiency part becomes far less critical as you just dial up more power from the sub amp.

My woofers (not from Kevin) are likely mid 80's efficient, and 100wpc each has them keeping up with the b200 no problem, so I would think that a quartet of these 15's would be fine sharing anything over 100wpc (ie 100 each).

I hope I get the chance to sample these, but I am not sure I can swing the deal right now - they are priced wonderfully, but only the tax man will know if I can afford them before May!

[navin]

Define reasonable, the baffle width and the bandwidth.   
I'd say the F500-TS is a perfect amp to drive four of these.

Have you compared this driver with it's obvious competitors from Eminence and Hawthorne? I have an older Carver amp (M1.0t 400W/4 ohms) that I intend to press into service for this purpose (2 x 15" OB per channel) is it adequate?

My room is about 250 sq. ft. (17x 15) with a 9 ft ceiling.

[Kevin Haskins]

Define reasonable, the baffle width and the bandwidth.   
I'd say the F500-TS is a perfect amp to drive four of these.

Have you compared this driver with it's obvious competitors from Eminence and Hawthorne? I have an older Carver amp (M1.0t 400W/4 ohms) that I intend to press into service for this purpose (2 x 15" OB per channel) is it adequate?

My room is about 250 sq. ft. (17x 15) with a 9 ft ceiling.

That should be plenty of power.    I've not compared it to anything.   We don't buy other drivers to design around, we dream-up what we need, explore the parameters to get there, and design the driver to achieve our design goals. 

I know Eminence's product line pretty well.   I like their drivers in general and their head engineer Jerry McNutt is a hell of a nice guy.    They have a Klippel in-house which I'm sure is helpful.    Their market is quite a bit different than what we tend to attract.   I don't think they make a single driver with 22mm of X-max.   Not because they couldn't, but because its not something their market requires. 

I'm sure they have a couple big high efficiency drivers with a high Qts that would be suitable for OB use but they won't play deep and they wouldn't have the excursion to support it if they did.    Not a knock at their product, its just designed for a different bandwidth. 

[navin]

I'm sure they have a couple big high efficiency drivers with a high Qts that would be suitable for OB use

I was thinking of using 15" OBs on a 18" wide baffle with 6" sides. Sort of like a very shallow "U". On top of this would be a Widerange like a B200 or Supavox 215 (and if needed a B&G Neo3 tweeter) on a seperate baffle (for isolation). Would a 15" woofer work or would I have to use something smaller like the DPL 10, DPL12, Hawthone 10" Augie or GR SW12-16FR?

Does the tweerer need to be dipole? If not would a dome Hiquphon/ScanSpeak/Seas or ribbon Fountek/Aurum Cantus or planar HiVi make more sense?

[Kevin Haskins]

Your asking questions I cannot answer.   Those are system design choices and ones I'd only make after measuring drivers in the intended application.

[Lazz]

Hello Kevin ,what is the eta on the dpl15?

[Kevin Haskins]

Hello Kevin ,what is the eta on the dpl15?

Its looking like May 14th +/- 10 days.

[taloyd]

Kyrill,

The only two way configuration the driver would work with would be more of a full-range with a "helper"... so then the question is where do you want to cross them, or do you have a sufficiently large full range driver (8", etc.) that you can do a 1.5 way.

Good potential drivers for a 1.5 way would be a Silver Iris, Jordan JX92, Fostex FE206, etc.

For a real two way, the above drivers, and smaller ones like a Fostex FE126, Jordan JX53, etc....

Most subwoofers have too much inductance (Le), cone mass (Mms), and too rigid a cone to be able to produce higher frequencies cleanly. This one is no exception... I wouldn't cross it higher than 150 Hz, and even that can likely sound better if crossed lower...

cheers,
-Tal

[poseidonsvoice]

Good potential drivers for a 1.5 way would be a Silver Iris, Jordan JX92, Fostex FE206, etc.

Precisely. I was thinking about using the DPL-15 with the Silver Iris/Sterling Silver Iris actively crossed over low at 50-60 Hz either in a U-frame or H-frame.  aa

Anand.

[Kevin Haskins]

The real inductance will likely be lower than our listed spec.   The Maelstrom-X came out much lower due to the AlCu inductance rings and the DPL-15 will likely follow that pattern.    The main issue I'd have with using it higher would be frequency response related.   It would follow the same design rules you would use for any other 15" driver.    Their cone break-up and dispersion patterns mainly dictating how they should be used higher in frequency and the linear distortion dictating how difficult the crossover.   

[Kevin Haskins]

No update on shipping but here are the prices on the 2-pack, 4-pack and 8-packs.

DPL-15:   $125ea   $34.25/L 

2-Pack:   $240    $32.87/L

4-Pack:   $450    $30.82/L

8-Pack:   $840    $28.76/L

[Kevin Haskins]

i suppose there is no info on DIYcable website yet?
is the ETA still in may?

Yes... nothing has changed at this point. 

[ezeg]

Any news on The DPL-15's yet?