Flared Ports (1 Viewer)

[ThomasW]

I'll drop in one more time......
Ted if you want to blow down the house with the 'Pod Race' sell the Samson along with the SVS. Get a BP1503 and one of the QSC or Crest amps. Yes the 1503 has a single 4 ohm VC. So you'll need an amp that's good to go for about 1Kw to get the total attention of your neighbors
Now understand I obviously have nothing against Adire products given that there are 4 subs in my house that contain a total of 20 Shiva's
But IMO, until the 15" Brahma is available the 1503 is the driver of choice. And at $266 delivered the it's cheaper than a MASS-12 or 2 Tempests

 

[Rudy H]

You can run a DVC driver with different (stereo L&R for example) signals going to it, your end result will simply be the sum of those signals. And no, your driver won't end up being torn apart, however if you were to run the coils out of phase and dump a ton of power into the driver and have the cone stand still...well...that would not be very good
When running one coil and leaving the other shorted or opened you change the Q of the driver, Adire has a very nice writeup on how you can change the Qtc of the driver at will. Good for your HT guys that like a lot of boom for HT and wanna keep very good musicality at the turn of a knob

 

[Dustin B]

I seem to remember it being said the Ultra was the equivalent of 2 original CS subs. And that a plus was 80% of an Ultra.

I seem to also remember a thread that said the original SVS CS driver was very similar to the BP1201. And that the Ultra was very similar to the Mass 2012. Given that the motto around here is, there is no replacement for displacement, I'll throw out the following rough Vd comparison numbers.

A 2012 has a Vd of 2.25L. So we'll say an Ultra has a Vd of 2.25L, a CS+ has a Vd of 1.8L and a normal CS had a Vd around 1.1L and is now around 1.3-1.5L.

A Tempest has a VD of 2.5L and a pair will have 5L. A BP1503 has a Vd of (site is down so I'm guessing) around 4.1L.

That's where my claim that my Tempest could match or take an Ultra comes from. Whether that is true or not I won't know for certain until I get a chance to compare my sub to an Ultra. Since that isn't likely gonna happen anytime soon I'll just keep believing my math is right :p)

So if you want to beat out a pair of 16-46CS+ subs you could build the BP1503 Thomas suggests. Or if size isn't an issue build a 480L dual Tempest sonosub tuned to 16hz with dual 6" ports powered by a RMX850 or 1450.

 

[Bryan Michael]

this is what i aam thinking and i dont have the dimenshons yet but do you gyys think it will work? i was thinking of using the tempest driverhttp://goinggonzo.tripod.com/gonzosworld/id11.html

 

[ThomasW]

Dustin

The Vd of a 1503 is pretty close to a HE-15 so figure on 6L

 

[Jack Gilvey]

That's where my claim that my Tempest could match or take an Ultra comes from. Whether that is true or not I won't know for certain until I get a chance to compare my sub to an Ultra. Since that isn't likely gonna happen anytime soon I'll just keep believing my math is right

That's what I based my estimate on, the Vd comparisons. Add to that the fact that using a 6" port provides about 25% more port area in addition to having less frictional losses than 3 small ports and I think you come out ahead easily. Use enough Vb and it'll likely be efficient enough to pull away with a $125 plate amp from PE.
The Blueprints are really tough to beat if you can give them a beefy amp.

 

[Dustin B]

Ok, I'm confused now. I thought the BP1803 was 6.2L. Am I calculating Vd wrong?

Tempest:

(3.28cm p-p Xmax)x(779cm^2 Sd)= 2.55L Vd

HE-15:

(4.57cm p-p Xmax)x(720cm^2 Sd)= 3.29L Vd

I can't get the Sd on the BP1503 right now, but I do believe the dumaxed Xmax was 25.86cm. So a 5.17cm p-p Xmax. Using the Sd of a Tempest that is 4.02L and the Sd of a HE-15 that is 3.72L. For some reason I seem to remember doing the calc a while ago and coming up with 4.1L, so maybe the Sd on the BP1503 is a little larger than the Tempest.

Is this not right?

 

[ThomasW]

Dustin
HE15 T/S Parameters*
Fs: 26 Hz
Qms: 6.0
Qes: .345
Qts: .326
Vas: 106.7 L
Re: 6 ohm
BL: 27.3 Tm
no: .529%
1W SPL: 89 dB
Cms: .145 mm/N
Mms: 257 grams
Rms: 7.0 kg/s
Xmax: 22.85 mm
Sd: 720 cm^2
Vd: 6.5L total
PEmax: ~ 2000W
3.5" p-p
Below are the DUMAX specs on the 1503.

You're correct Vd is usually calculated as maximum linear volume of displacement of the driver (product of Sd times Xmax), in cubic meters.
Sometimes people include 1/2 the width of the surround as part of the radiating area. Others play around with the Xsus as well.

 

[Dustin B]

Have I been calculating Vd wrong all along?

Using that Dumax sheet I get 3.81L for the BP1503.

So to recap by my calc (from Sd and Xmax):

Mass 2012 = 2.25L

Tempest = 2.55L

HE-15 = 3.29L

BP1503 = 3.81L

 

[ThomasW]

Have I been calculating Vd wrong all along?

Technically you're correct. I'll let you figure out where the 6.5L for the HE-15 comes from

 

[Jack Gilvey]

I think that sometimes Vd discrepancies arise from the different Sd values arrived at by DUMAX and those listed by the manufacturer. And, as Thomas mentioned, by using the Xmech values instead of Xmax. This is how ~6.5L is arrived at for the HE-15...not sure if that's a DUMAX Xmech spec, or just the point at which it was found to "bottom" (you can see why people find that impossible to do, though). Using Xmech for the 1503 yields 5.3L, but that's to the point of 400% of the rest Kms value (or, I guess, 25% of the rest Cms?), and does not necessarily indicate "bottoming" ( based on the look of the Kms curve, the 1503 is not "bottoming" at that point, as travel appears to continue well past Xsus/Xmech, so total swept volume could well be on par with the HE15...I'm out of my depth now, though).

For the BPD 1803, using the listed 1217cm^2 Sd and the 25.86mm Xmax results in a Vd of 6.3 L. "Total swept volume", using Xmech, is 8.8L.

 

[TedO]

Just one last question.

Does the Bluprint sub sound "boomy" or need heavy EQing?

If not, this sub project sound like the answer.

I will first build it (maybe in a month or so) then test it and if all is good I will sell my SVS and Samson.

TedO

 

[Dustin B]

It does require some EQ. There is an inductance hump (don't understand this, I'm just repeating) at 70hz that needs to be tamed. Unless you are crossing over at 70hz or lower to the sub.

As for being boomy. Boom is more a function of the enclosure than the driver. Put it in the wrong enclosure and it will sound boomy. Put it in the right enclosure, with enough power and a little eqing and you will have an incredible sounding sub.

 

[ThomasW]

Ted

No the BP1503 doesn't sound boomy if the enclosure is properly designed and made. It requires more EQ than a Tempest but less than a HE-15.

The current crop of high excursion 15"s have a relatively high voice coil inductance. This creates a rising amount of output as the frequencies get higher. So a little EQ to drop this down is helpful.

According to Dan W the new Braham series of drivers are designed so the VC inductance is lower. So the output at higher frequencies is flatter.