Best Sub Driver for small enclosures (1 Viewer)

[ChristianT]

First I am going to build a Sonosub (which I hope to rough finish today). I am not using any 1503 Dumax measurements other than xmax. The rest of the measurements I am using come from the BPD site. For example, what do the BPD Cms and Mms measurements correspond to in Unibox? This question applies to other software like WinISD. I am having trouble matching BPD measurements to measuremets in the software. Do you have any recommendatios for the tuning point? I have 16" diameter sonotube, and a 4" flare to couple with 4" pvc.
My second project is going to be a vented box. I don't have very good woodworking skills, so this is going to be trial and error. Depending on difficulty, I might even try the sealed box idea from Jon.
Thanks,
Christian

 

[ThomasW]

Christian
Just chatted with JonMarsh, for a single 1203 he recommends;
80L net internal volume, tuned to 20Hz using a 4" port 25" long.
With this config you can get 112db output down to 20Hz anechoic, with 1000 watts in
[Edited last by ThomasW on November 04, 2001 at 01:59 PM]

 

[ChristianT]

I have a few questions if it isn't too much trouble.
Is there any benefit to going with a larger enclosure than 80 liters? I have plenty of room. My calculations put the tube length at 29". With the port length being 25" and top mounted, is this too close to rear of the driver?
Is the 80 liter number taking into consideration acoustic stuffing? Sould I or shouldn't I add polyfill to the enclosure?
Thanks in advance,
Christian

 

[Jack Gilvey]

For example, what do the BPD Cms and Mms measurements correspond to in Unibox?

Those specs from the BPD site correspond to the same ones in Unibox, but are not input directly, they are derived by the program based on the specs you do input. The numbers Unibox gave me are very close to the BPD listed specs, although Cms is listed in different units.
WinISD is not as sophisticated, and I think it only really uses the Fs, Qts, and Vas specs to give you a box size, port length, and some idea of frequency response. I'd stick with Unibox, since the price is the same.
How much power do you plan on feeding your sub, do you have the amp yet?

 

[ChristianT]

I have a PE 300-793 now, and will have a Crown K2 within the next month. I plan on using the PE amp in my next box sub, so for now I have built a small stand-alone box to house it until my next project and the Crown amp show up.
I feel stupid now about the Unibox question. I was trying to update the database tab directly instead of inputing the values on the speaker design tab. That is why I couldn't figure out what data to put in all of the extra fields.
Thanks,
Christian

 

[ThomasW]

Christian
No there is no benefit to using a bigger enclosure given the relatively high Fs of the 1203. Jon looked at several different sizes and 81L is the best for the 1203
Yes, line the tube with a 1"-2" layer of bonded polyfill or some eggcrate foam. You could add a liter or two to compensate for the damping but it isn't necessary.

 

[Jack Gilvey]

I'll bet the PE 250 watter will be a good mate to that vented box as long as you defeat the bass-boost, and your port airspeed would still be pretty good. When you get the K2, one channel to each sealed/equalized 1203 as Jon suggested might be a fun project, and would rival multi-thousand dollar subs. Those things move more air than almost any 15" driver.

I feel stupid now about the Unibox question. I was trying to update the database tab directly instead of inputing the values on the speaker design tab. That is why I couldn't figure out what data to put in all of the extra fields.

That certainly wasn't a stupid question, Christian. It's freeware, and it's not like there's a big manual with these things, so there's a lot to figure out on your own.
If you want stupid questions, search under my name for posts from a year or two ago. I ask stupid questions now, of course, but they won't seem stupid to me for another year or so. I think that's the way it works.

 

[Jon Hancock]

Hi Guys,
I had been toying with the idea of a Linkwitz transform box for these (sealed, EQ to get low end, taking advantage of their enormous Xmax - about 28 mm). But once I sat down and ran the numbers, a different story emerges.

It's hard to argue with over 10 dB more output at 20Hz, other than the degradation of transient response. The ported version still damps out quicker than a comparable PR (I looked at both).
Bottom line, I'll be doing a true Aerial SW-12 Klone, or rather, I'll be cloning a 12" version of our Aerial Stryke AS-15. With the same maximum input, there's over a ten dB difference in maximum output in the low bass, and that's just too much for me to ignore.
But still, the idea was cute, even 102 dB from a 48L sealed box is pretty impressive. I've got a Woodstyle baby sub cube around, so I may throw that together with the Marchand Bassis just to sese what gives. But 112 dB from 80L is even more impressive, I think.
This will give me some good reasons to finish the digital amp prototype I've been working on- so I don't have to devote an Aragon to a sub amp. We have other plans for those.
Regards,
Jon
[Edited last by Jon Hancock on November 05, 2001 at 04:19 PM]

 

[Jack Gilvey]

The 1203 is nothing if not interesting.

I've got a Woodstyle baby sub cube around, so I may throw that together with the Marchand Bassis just to sese what gives.

I'd certainly be interested in the results, if you decide to give it a whirl.

 

[ThomasW]

Jack
I wouldn't worry too much about degradation of transient response with vented designs. The AS-15 has some of the 'fastest' transient response of any sub I've ever heard. So a proper ported design with the 1203 should perform very well indeed. I'd forgo the PR's and go ported. And yep 4" flares are the only way to go with a 81L box. I'd say from looking at the SW-12 website that Aerial's driver is a TC-12". So relatively speaking the BPD-1203 should be an even better driver.
my $.02 of course
[Edited last by ThomasW on November 06, 2001 at 01:02 PM]

 

[ChristianT]

Does anyone know the approximate volume of the 1203 itself? Am I being too picky figuring the volume of the bracing and driver into the enclosure measurements to get a net 80 liters? I am a firm believer in doing a job right the first time, but if this is being anal, please let me know.
Thanks,
Christian

 

[Brian Bunge]

I emailed Pat @ Blueprint about the 1803's volume displacement and he said it was .21ft^3 so the 1203 can't be more than that. I don't know if this includes the driver's basket or just the motor structure. If it's just the motor structure I'd think it would be just the same.
Brian
------------------

 

[Jack Gilvey]

Thomas,
I'm afraid I read Jon's comment on degraded transient response the wrong way, and so my reference to it was unclear in its meaning. I didn't mean the vented would have degraded transients compared to sealed (although I guess that's technically true, and apparently what Jon meant). What I was trying to get at was how the transient response of that type of curve would be compared to a flatter curve without the hump at Fb. I thought Jon meant that it would be "degraded" in comparison to a "flat" reflex alignment, and not to his proposed sealed box.
I'd agree that modern drivers allow vented alignments to sound nothing like their older counterparts which earned reflex designs the "boom-box" moniker.
Your $.02 goes a long way around here.

 

[Brian Bunge]

Well, taking into account the conversion factor, I think Thomas' $.02 is worth more than my $2.00!
Brian
------------------

 

[ThomasW]

Jack
I'm pretty sure Jon was referring to the difference in the sealed vs ported as portrayed by the model. But output difference at 20Hz seems significant enough to offset any potential benefit offered by the sealed design
just my $2.00 (now adjusted for ego inflation

)

 

[Jon Hancock]

Hi Guys,
Here's my $0.02-
Comparing curves, there is a small correlation regarding transient repsonse, to peaking, but it's not as simple as it seems, because in both cases you're tuning below the the resonsnace. The bigger the box, the higher the port Q, and it does peak and hang over a little more. But, remember that hang over is mostly in the port output. So, with a cabinet tuned to 18 Hz, there's little affect on the transient response at 40 Hz and higher.
Yes, I was comparing ported versus passive radiator in evaluating for comparable bandwidth; the ported transient reponse settles out sooner, by about 30%.
Well, I think with the BP1203 I'm going to build one of each- an AS-12, and a bitty cube with Linkwitz transform.
Measured Vc inductance was high- 10 mH. This depends somewhat on the freuqency you measure at, but the impedance curve I measured shows the minima at about 70 Hz, with a rise commencing; so they'll also have the "hump in the middle" characteristics of the HE-15.
The packaging is kind of a hoot.

These are the heaviest small boxes I've ever seen!
Regards,
Jon

 

[Jack Gilvey]

Thanks, Jon. Imagine the box for the 1803...I didn't think the FedEx guy was going to make it up the steps to my front porch.

 

[Brian Bunge]

I wasn't quite prepared for the weight of the 1803 either! I bent over to pick it up and quickly realized that I needed to bend at the knees and "lift with my legs"!
Brian

 

[Martice]

Would the BluePrint 1203 be similar to the driver used in the Velodyne HGS 12' sub? If not what are the differences and what would it take to get this driver in a cabinet as small as the Velodyne size? I believe the dimensions are around 14x14x17.
Hey Jack. Thanks for the e-mail response. Kyle at acoustic-visons.com is supplying the goods as far as my DVC 12" driver, cabinet and assembly goes. I never put together a sub before so I had them construct the cabinet for me. However, I will put one together in the near future.
------------------
What if it gets no better than this!?!
[Edited last by Martice on November 07, 2001 at 12:53 PM]
[Edited last by Martice on November 07, 2001 at 12:57 PM]

 

[Jack Gilvey]

Hey Jack. Thanks for the e-mail response. Kyle at acoustic-visons.com is supplying the goods as far as my DVC 12" driver, cabinet and assembly goes.

You're welcome. Sounds like a sub you'll enjoy.