[Rclark]

http://www.audiojunkies.com/product/97/adire-audio-brahma-15quot-mkii-reviews


So I'm putting together my first system and have an unused pair of those that I would like to use. They will be paired with these http://speakerdesignworks.com/Statements_Monitor.html

If someone has a design that would work well I've got someone ready to cut wood. Thinking baltic birch stained.

Hoping this design has the subs somewhat elevated. Thanks for any help! Also need some proper amplification too btw.

[Angaria]

What are your target SPL's?  You're going to need active eq for those...

[Rclark]

Oh I don't know about spl, this is a first sub of this type I'll have listened to. I assume I'd want the normal range of spl capability even though I'll likely listen at low to moderate. So normal? I guess? Ability to turn up loud ocassionally just like anything else? Hard to answer that question.
 
 And kind of an odd question, as though there could be any spl issues for a pair of 45 pound 15's.

Can you please elaborate on the need for an active eq? I don't understand the how or why. Does that mean I just need sub amps with extra eq, like those Rythmik plate amps with parametric eq built in?

[Rclark]

 Yeah I'm a bit fuzzy on the EQ part. Would just a really nice subwoofer amp with really nice eq take care of that? Or are you saying I need a seperate unit of some sort?

 Actually, just got an email from my flatpack guy and he wants to know if I want open baffle type monopole or dipole and I don't know what to say.

 is monopole ob two seperate units and dipole is the two subs mounted on the same thing? Also asks if I want .75 inch or 1 in.

 Guys, I really don't want to put these in sealed boxes, I really do want to run them OB, but have absolutely no idea what to do. Please help

 OB white papers are terribly complicated for this non-engineer. Kind of funny how a woofer on a flat panel seems to be the most complicated application of them all.

 Help a brother out.

[JohnR]

Yeah I'm a bit fuzzy on the EQ part. Would just a really nice subwoofer amp with really nice eq take care of that? Or are you saying I need a seperate unit of some sort?

 Actually, just got an email from my flatpack guy and he wants to know if I want open baffle type monopole or dipole and I don't know what to say.

 is monopole ob two seperate units and dipole is the two subs mounted on the same thing? Also asks if I want .75 inch or 1 in.

 Guys, I really don't want to put these in sealed boxes, I really do want to run them OB, but have absolutely no idea what to do. Please help

 OB white papers are terribly complicated for this non-engineer. Kind of funny how a woofer on a flat panel seems to be the most complicated application of them all.

 Help a brother out.

The reasons for the need for EQ with a dipole sub are because of the cancellation that occurs between the acoustic wave from the front and back of the baffle. You may be able to get away without it but it really depends on many factors... I haven't looked into those drivers but if EQ and various kinds of mucking around are an issue then perhaps a more conventional box design would be easier to approach i.e. sealed or ported.

[Rclark]

ok so basically just go for it and hope for the best, buy some kind of eq and any old panel should do it. The open baffle forum rocks.

[Angaria]

+1 on EQ,  if you really want to look into this get an OB simulator - the MJK worksheets, or I think Basta or the Edge will show you what kind of roll-off you can expect....  it's prodigious unless you have a high qts woofer or a lot of xmax to work with via eq.

[JohnR]

ok so basically just go for it and hope for the best, buy some kind of eq and any old panel should do it. The open baffle forum rocks.

Basically, yes. You seem to be wanting a cut and dried answer to an unusual question and there isn't one. I'd suggest just stick them into a 600x600 (mm) baffle and see what happens to start with. If you have enough power to get those drivers to full excursion there's a good chance that you can, as open baffle is a great way to use up excursion at low frequencies - but then again nobody including yourself knows what output levels you need at what frequencies... so you'll need to experiment! If output level does turn out to be a concern then you could try building a pair of U-frames; if it really is a sub and therefore can be run in mono then you could try a W-frame. Also, if you don't mind my saying so, it does seem a bit odd that you would be pairing them with ported monitors, it's somewhat opposite of the usual approach. Hope that helps a bit more...

[chlorofille]

Rclark,

The ported monitors + open baffle sub is a very unusual mix. Unless you absolutely have to build an OB sub, I suggest you go for a large ported enclosure which can be accompanied by a 500W subwoofer plate amplifier. 150L tuned to 20Hz or 250L tuned to 15Hz 

With a large enclosure, no EQ is needed. I'm running a pair of peerless XXLS 12'' subs in a 250L box and they do 18-25Hz with stunning authority. There is no replacement for enclosure volume !

Here's a suitable sub amp.

[Rudolf]

Guys, I really don't want to put these in sealed boxes, I really do want to run them OB, but have absolutely no idea what to do. Please help

First: You should not run them in OB, but in a H frame (which is sort of OB, anyway).
Second: You should run them with only one voice coil connected to raise the Qts. I could do a MJK simulation for you, but would need the TSP for the Brahma with only one voice coil connected. What you have linked is for both voice coils in parallel only.

[Rclark]

Ah Mr.Rudolf. Respect. Please tell me more. What is a TSP?

Do you think the Brahma's in H-frame will work with my monitors? I will go ahead and seal them if need be, and I can do OB on my next build, but I'd prefer OB if I can manage it. I'm going to call Danny at GR, he seems to think it can work and has a solution.

 Thanks for the help everybody! I'll have this system up eventually and then speaker porn for all.

[mcgsxr]

TSP - Thiele Small Parameters - the specs please!

[Rclark]

Fs 26 Hz
Qms 5.5
Qes 0.51
Qts 0.47
Vas 113 liters
Znom 1 Ohm parallel
Re2 0.75 Ohms parallel
Le3 0.45 mH parallel
BL 15.9
Sd 749 cm2
Xmax 28mm one way linear
Pmax4 1600W RMS, 4800W peakNOTE: Power rating is thermal only! It is NOT a power requirement; typically you get full output with significantly less power than the rating.SPL5 87.6 dB @ 1W, 1mDiameter 15.5"Cutout 14"
Depth 8.25"
Volume 0.18 cubic feet
Weight 41 pounds

[Rudolf]

Fs 26 Hz
Qms 5.5
Qes 0.51
Qts 0.47
Vas 113 liters
Znom 1 Ohm parallel
Re2 0.75 Ohms parallel
Le3 0.45 mH parallel
...

Yes, I have seen those values before. But that "parallel" signals, that the parameters above have been measured with both voice coils connected in parallel. They will be different when measured with a single voice coil connected - but better suited to dipole use IMHO.

As long as I don't know the single coil parameters, I can only give a wild guesstimation:
Build a H frame that is just wide and high enough to fit the Brahma. Make the total depth roughly the same as the width of the opening. Add a 10 mH iron core inductor in line with one voice coil of the driver and start from there.

If Danny at GR has any experience with that driver, you certainly should go with his advice.

Rudolf

[JohnR]

You can get the T/S of a single coil from the parallel coil ones.. double the Re and Le... I think you halve the Qes and that's it. Or is that double it... Let me just check that with Unibox...