A few months ago I scored some old Adire Brahma 12". After looking up old reviews and specs, I thought $125 for two of them in very good condition was an absolute steal. In some old threads and from the person I bought them from, box suggestions were around 2cu.ft. for sealed and 3cu.ft for ported. Wanting to get some really deep bass for HT, I am looking into ported. Threw the driver into WINISD and let the software come up with parameters for C4/SC4 box. It suggests 10.55 cu.ft. and 21hz port tuning. Looks like a nice response but seems WAY too big of a box. I threw in some smaller boxes and different tuning just to play around. The 7 cuft still looks nice, but going to 3cuft it seems to drop off quickly and the F3 isnt all that impressive. Am I missing something here? Any suggestions for a smaller box with substantial low end response? I have included the driver parameters in the screen shots. I got that information from the person I purchased them from. He said he had actually tested the drivers and confirmed Fs etc.
A single driver in a 3cu.ft box tuned to 15Hz gives a nice response for home theatre but the ports would have to be massively long to accommodate the xmax / power handling of the driver. I think you'd have to look at passive radiators or going sealed.
Vas/1.44 tuned to Fs is optimum max power handling Vs box size, so WinISD is properly showing you that as tuning goes lower, box volume [Vb] needed to maintain the ratio must increase, with of course Xmax setting increasingly less usable peak SPL.
GM
Thanks for the feedback. I guess the real question I am trying to ask is can I get some decent low extension out of this driver in a reasonable box size? The 7-10 cu.ft. boxes seem to produce nice relatively flat response all the way down to the 20hz region (in the WINISD model anyway). The smaller box sizes roll off much quicker and have peaks in the response in the 40-60 hz range. Not sure if that will sound OK. I have never really had a good home sub capable of producing anything meaningful below 40-50hz, so I wanted to get in on some of that low rumble in the 20-30hz range from movie soundtracks. These woofers have 26mm Xmax and decently low Fs with plenty of power handling so I thought I might be able to achieve that. But maybe it will just require a really big bos with these drivers
You're welcome!
Again, as WinISD has shown you, this driver's specs demand a big box to go low with authority, though can tune it low in smaller boxes at the expense of either a huge vent to handle its power or accept that it might not be loud enough to the deep bass 'thrill' of a T-Rex without audible vent noise spoiling it a bit, or as Rob noted, use dual passive radiators [PR] as a mechanical vent substitute.
All that said, you can put it in a TL pipe, i.e. the tube IS the box + vent and thanks to B0$3 we can make it as small as 50% of driver [Sd], which normally is plenty big enough in area to handle the power based on a same size vent area.
A quick sim is 7" dia. x 147.22" L pipe tuned to ~22 Hz, the lowest practical tuning based on Fs/peak power, though would be built as a folded in half box with the driver at one end ~31" up off the floor and the vent at the other end at the floor, so ~3.333 ft^3 net.
Of course the trade-off is still a high F3, can't fool Mother Nature, but down low it matches or bests the 7 ft^3/22 Hz Fb cab down to their ~12 Hz/110 Hz peak limit, though it needs all 600 W Vs the ~2.1x larger cab's ~25 W limit and in a corner can potentially give you more true sub [infra] bass performance than all but the most powerful consumer subs.
GM
Again, as WinISD has shown you, this driver's specs demand a big box to go low with authority, though can tune it low in smaller boxes at the expense of either a huge vent to handle its power or accept that it might not be loud enough to the deep bass 'thrill' of a T-Rex without audible vent noise spoiling it a bit, or as Rob noted, use dual passive radiators [PR] as a mechanical vent substitute.
All that said, you can put it in a TL pipe, i.e. the tube IS the box + vent and thanks to B0$3 we can make it as small as 50% of driver [Sd], which normally is plenty big enough in area to handle the power based on a same size vent area.
A quick sim is 7" dia. x 147.22" L pipe tuned to ~22 Hz, the lowest practical tuning based on Fs/peak power, though would be built as a folded in half box with the driver at one end ~31" up off the floor and the vent at the other end at the floor, so ~3.333 ft^3 net.
Of course the trade-off is still a high F3, can't fool Mother Nature, but down low it matches or bests the 7 ft^3/22 Hz Fb cab down to their ~12 Hz/110 Hz peak limit, though it needs all 600 W Vs the ~2.1x larger cab's ~25 W limit and in a corner can potentially give you more true sub [infra] bass performance than all but the most powerful consumer subs.
GM
Is this same driver?
Brahma - Adire Audio
Thats quite some X-Max! I was having a look with WinISD, the built in params give me a similar graph as your third pic, looking on the Adire site, some of the values are quite a bit different to what your editor shows.
Tried putting the Adire listed into a new driversheet.
Both sets of numbers produce a box way smaller than 10cft?
Just playing with numbers, the Box given for the built in params is almost same as my ScanSeak 32W4870T00 @ just over 3.1cft my port being 12cm longer at 62cm
with what I could get from website wants 1.5cft with 72cm port which seems well off...
I actually run Sealed box at rough 3.5cft, I have not tried ported but have the option to try with the built size.
I did have a screenshot of Holmimpulse somewhere which was pretty much identical to the WinISD prediction
Brahma - Adire Audio
Thats quite some X-Max! I was having a look with WinISD, the built in params give me a similar graph as your third pic, looking on the Adire site, some of the values are quite a bit different to what your editor shows.
Tried putting the Adire listed into a new driversheet.
Both sets of numbers produce a box way smaller than 10cft?
Just playing with numbers, the Box given for the built in params is almost same as my ScanSeak 32W4870T00 @ just over 3.1cft my port being 12cm longer at 62cm
with what I could get from website wants 1.5cft with 72cm port which seems well off...
I actually run Sealed box at rough 3.5cft, I have not tried ported but have the option to try with the built size.
I did have a screenshot of Holmimpulse somewhere which was pretty much identical to the WinISD prediction
juz400 - that is a new version of the driver that I have. I don't think the parameters on that driver are the same as the ones I have. I did some searching on Google and found that the original Adire Brahmas were quite the drivers in their day. Huge Xmax, but also known for SQL and not just SPL. And the XBL^2 system was very unique...I forgot exactly how it all works but basically keeps the magnetic field consistent through the range of motion and therefore speaker can reach Xmax with more linearity. Like I said, I am really interested in putting these to use as I think they should be incredibly high quality drivers.
GM - I would love to build a TL or horn with these. I tried to use Hornresp but got frustrated and gave up. WINISD is really easy to use, but doesnt model horns or TLs. Never tried to build a 6th order bandpass...any advantages over a 4th order or ported or TL with a 6th order?
If you think a TL would produce good results I would try it. I am just having a hard time envisioning the enclosure you described. How can I use a 7" pipe with a 12" driver?
If you think a TL would produce good results I would try it. I am just having a hard time envisioning the enclosure you described. How can I use a 7" pipe with a 12" driver?
GM - I am intrigued with the TL idea. I have seen a video that claims, in its simplest form, a 1/4 TL is constructed basically with the tuning frequency in mind. Just make the length of the pipe equal to 1/4 of the wavelength of the tuning frequency. Obviously there are all kinds of design parameters, tweaks etc. But essentially could one build a simple TL just using that concept?
What are you using to model TL? Hornresp? If a TL will produce really nice results with authoritative low end bass and is not too complex, then I would love to build one.
Also, what is BO$3? I am not familiar with that? It sounds like maybe you are suggesting that for this driver (or any driver?) that the area of the line and thus the opening at the end need only be 50% of Sd. Would larger cross section produce higher SPL or other benefits?
All that said, you can put it in a TL pipe, i.e. the tube IS the box + vent and thanks to B0$3 we can make it as small as 50% of driver [Sd], which normally is plenty big enough in area to handle the power based on a same size vent area.
All that said, you can put it in a TL pipe, i.e. the tube IS the box + vent and thanks to B0$3 we can make it as small as 50% of driver [Sd], which normally is plenty big enough in area to handle the power based on a same size vent area.
Greets!
Right, though it's an acoustic 1/4 WL long tube, so will be somewhat shorter to actually tune it to Fs, which of course should be measured rather than assuming the published spec is accurate.
Yes.
Well, it takes a lot of box volume [Vb] to make big/authoritative bass [up to 10x Vas depending on driver specs], so most 'bass' TLs are actually powerful, high SQ mid-bass speakers tuned low and use the room gain to 'pump it up' some.
GM
World's most successful audio company, misspelled to disrespect them for how they did it, but got to give the 'devil his due' thanks to its prime engineer and mass quantities of R&D.
???, just means its a constant [straight] tapered TL's optimal acoustical loading is a 2:1 CR Vs the pioneer's 1:1. Most of mine were 10:1 tapered based on the pioneer's conclusion it was the highest CR a compression horn could stand, long term. Me and at least one other have done up to 20:1, but mine were vere very narrow BW alignments, not sure about his.
The bigger the box, the lower its F3. SPL is a function of box tuning, power handing available.
For instance, you want lots of mid-bass efficiency, so make the box Vb = Vas/1.44 tuned to Fs and choose an Fs, Qts that gives you the desired mid-bass 'bump', i.e. normally an under damped alignment.
For ported, the pioneer's seemed to claim a 1:1 vent ratio because Thuras [BR inventor] used them in his patent, but decades later in an interview said he did the test box alignments such to keep the math as simple as possible and proved it by making virtually all of the production designs with much smaller vents.
Anyway, TLs are like sealed, lots of design flexibility to fit the needs of the app since normally tuned with stuffing, EQ.
GM
OK...got it about the large audio company.
GM - let's assume I have just about no clue what you are saying in about 80% of the above post. Sorry...I am an amateur builder and have zero experience with anything except sealed boxes and a few ported projects. Given that...I believe through your responses in this post that you are saying a TL could be a good design for getting deep response in a possibly smaller enclosure than required for ported?
I'm hoping to get some nice low rumble for HT application
I think I finally found a spot in the family room for two enclosures using the Brahmas. We have some built in cabinets with shelves and I think I might be able to "hide" two of the enclosures in some of that area. Dimensions of each available space are 32.5" wide by 13.5" deep by potentially 20-24" tall. Assuming 3/4" MDF construction, some internal bracing and space taken up by the woofer itself and possibly a port it means I have about 3.5-4.0 cubic feet to play with.
With a goal of getting some reasonable output for HT in the 20-ish Hz range given these dimensions, should I attempt sealed, ported or TL? I know ported are not known for their sound ... not as "tight" as sealed. But I think ported might help get me down to some good output below 30Hz.
Would there be a problem with building one of these ported and the other one sealed?
Thanks
With a goal of getting some reasonable output for HT in the 20-ish Hz range given these dimensions, should I attempt sealed, ported or TL? I know ported are not known for their sound ... not as "tight" as sealed. But I think ported might help get me down to some good output below 30Hz.
Would there be a problem with building one of these ported and the other one sealed?
Thanks
OK...I just went ahead and started building. Box is going to be ported and I have 4.77 cubic feet as a gross internal volume. In WINISD it looks like I need two 4" ports to keep port velocity down, but that seems a bit overkill. Maybe one 4" should be enough? Maybe if driving this with a lot of watts because of such large excursion is why it is calling for such a large port.
Correct, it can be as little as ~3.33 ft^3 net, though with the understanding that with speaker box design, less is always less, so while it can be tuned low for 'rumble' it will have a high roll off beginning around ~1.56x Fs.
GM