Got the executioner 21s at home waiting on a couple of 3" x 4" baffles under a couple Fostex 168 sigmas. With PE's cheap plate amp (6dB boost @ 30Hz) They're flat to 30Hz with no other correction.
I'm going to hear another guy's system with them this weekend--in baffles under Supravox field coils.
I'm going to hear another guy's system with them this weekend--in baffles under Supravox field coils.
Perfect centering isn't crutial, it just gives better balance. For a 2 driver sub setup, I prefer a W baffle because you get a more compact box and reduced vibration due to mechanical cancellation.
Madison drivers
Check the specs on the Madison drivers (http://www.madisonspeakers.netfirms.com/rawdrivers.htm) for suitability for dipoles.
For example, Fs is over 30 hz for all these drivers.
Check the specs on the Madison drivers (http://www.madisonspeakers.netfirms.com/rawdrivers.htm) for suitability for dipoles.
For example, Fs is over 30 hz for all these drivers.
Clyde, are you saying that Fs > 30 is (as Martha would say) "a good thing"?
I read on some site recently that a low Fs and lots of Xmax weren't really necessary for good bass, but whoever it was didn't give any basis for this other than his opinion. Anyone out there heard this line before?
I read on some site recently that a low Fs and lots of Xmax weren't really necessary for good bass, but whoever it was didn't give any basis for this other than his opinion. Anyone out there heard this line before?
The Linkwitz dipole model (http://www.woodartistry.com/linkwitzlab/models.htm) is required reading for anyone that wants to build a dipole sub. Low Fs, large driver size, large Xmax and large baffle size will determine the SPL performance.
See my post of an IB15 dipole prototype (http://209.124.89.84/forums/showthread.php?s=&threadid=34556) for some nice results using these guidelines.
See my post of an IB15 dipole prototype (http://209.124.89.84/forums/showthread.php?s=&threadid=34556) for some nice results using these guidelines.
Well... there are a few more factors....
I agree SL's site is required reading (although now it looks like you gotta buy the CD to get all of it...) but he only holds forth on one way of getting dipole bass done--specifically, with lots of electronic EQ. In that brute-force scenario, Fs isn't all that important as long as it's below the target passband, so lower is better from the standpoint of flexibility. I have no problems with this way of doing OB--props to SL, et. al. 😎
However, there is another way to hit a target dipole response--use a woofer with at least part of the EQ built in. A woofer with a Qts above 0.707 will have bump in the infinite baffle response around Fs. As you take Qts north of 1, the bump gets significant and can go a ways toward equalizing the dipole acoustic shunt. Now, obviously you need to pay closer attention to Fs--it steers where the bump goes and marks your lower cutoff.
In this case, an Fs below 25Hz is in fact detrimental, as it drags your EQ peak down too low to be useful. (Unless you've got some extremely ambitious hardware/plans, you shouldn't expect to get any real <25Hz SPL out of an OB. Linkwitz didn't, that's why he uses the Thor monopole to pick up from the Phoenix dipole below 40Hz.)
So if you're a reasonable chap and want to take your modestly sized OB down to 40Hz with minimal EQ, you want to find a driver with an Fs of 40Hz, a Qts around 1 or greater, and as much Sd and Xmax as possible.
I'm not an entirely reasonable chap, so I decided I wanted an OB with a lower cutoff of 30Hz. Soon thereafter, I stumbled onto the hideously named Madison Executioner 21--Fs: 28, Qts: 1.17, Sd: 298 sq. in. (
) (These specs are from the sheet that came with the drivers and differ some from the specs published online).When I used Brian Steele's OB spreadsheet to simulate these on 3'x4' baffles each driven by the cheap ($75ea.) PE plate amp with 6dB @ 30Hz boost built in, I found a match made in heaven--flat down to near 30Hz with no additional EQ. (the sim below has a 2nd-order Butterworth lowpass at 110Hz.) The combo was easy to do, sounds fantastic, and didn't break the bank.
Attachments
apples and oranges
Of course, I should have stated "max SPL". I think this context was reasonably clear in my post.
If one is to be quoting Mr. Linkwitz, they should also be using his dipole models. The only variables determining excursion limited SPL are Dipole size, Xmax and Sd. Qts and active equalization help to determine frequency response but not max SPL.
The 21" Madison Executioner dipole in a 3' by 4' open baffle is an interesting design. According to the Linkwitz dipole model, expect excursion limited max SPL of about 101dB at 30hz, 3dB more than my current IB15 in a 24" H baffle. The ultimate variation of this design would be to use the 21" ExecutionerX, with twice the Xmax of the Executioner, resulting in 6dB higher max SPL at low frequencies. My planned dual IB15 dipole will have 107dB max SPL at 30hz, exceeding the THX specification.
I look forward to seeing pictures and measurements posted for the completed Executioner dipole.
Of course, I should have stated "max SPL". I think this context was reasonably clear in my post.
If one is to be quoting Mr. Linkwitz, they should also be using his dipole models. The only variables determining excursion limited SPL are Dipole size, Xmax and Sd. Qts and active equalization help to determine frequency response but not max SPL.
The 21" Madison Executioner dipole in a 3' by 4' open baffle is an interesting design. According to the Linkwitz dipole model, expect excursion limited max SPL of about 101dB at 30hz, 3dB more than my current IB15 in a 24" H baffle. The ultimate variation of this design would be to use the 21" ExecutionerX, with twice the Xmax of the Executioner, resulting in 6dB higher max SPL at low frequencies. My planned dual IB15 dipole will have 107dB max SPL at 30hz, exceeding the THX specification.
I look forward to seeing pictures and measurements posted for the completed Executioner dipole.
Actually, if one is to use SL's methods properly, published Xmax is irrelevant. What is important is how much "real" Xmax you can use before distortion and/or chuffing noise become audible. That's why a single 15" IB driver (similar to the rest of the DVC, Tempest, Shiva family OEM'd from Eminence) doesn't "outperform" a pair of Orions even though, at first glance, it might appear that way on paper. Even the 15" Titanic Mk3 doesn't do it. 😉
Woofer distortion tests
Don't just look at the 20-30 Hz charts. By the time you get up to 100 Hz, the XLS and TC2+ are in a class of their own.
Hey Catapult,
Instead of pointless bickering about who's the better disciple of Linkwitz, let's try to encourage others to take full advantage of the available authoritative dipole information. There is also a dipole mail list, but activity there has been sparse of late.
The whole point of the DIY forum is for people to innovate and experiment with new designs and drivers. I give credit to chops for starting this thread and carrying through with construction a new low cost dipole sub design that many people found quite enlightening.
Regarding the Orion, I was one of the first to hear it at SL's house and post a public review, a rave by the way. But, as the saying goes, "it ain't got no bass". The interesting opportunity for DIY's is that big dipoles with big drivers are capable of producting really clean and loud deep bass.
In fact, I'm off to build a bigger one right now.
Instead of pointless bickering about who's the better disciple of Linkwitz, let's try to encourage others to take full advantage of the available authoritative dipole information. There is also a dipole mail list, but activity there has been sparse of late.
The whole point of the DIY forum is for people to innovate and experiment with new designs and drivers. I give credit to chops for starting this thread and carrying through with construction a new low cost dipole sub design that many people found quite enlightening.
Regarding the Orion, I was one of the first to hear it at SL's house and post a public review, a rave by the way. But, as the saying goes, "it ain't got no bass". The interesting opportunity for DIY's is that big dipoles with big drivers are capable of producting really clean and loud deep bass.
In fact, I'm off to build a bigger one right now.
Assuming this is just for bass, I wouldn't do either for a baffle like that. Take advantage of the free ride of the floor. Turn it with the long edge on the floor and mount them as close together as possible and as close to the floor as possible. Don't forget to mount them facing opposite directions and wire out of phase to get the distortion reduction benefit of push/pull.
Is this just a test baffle? If it is, take driver cutout placement into consideration, so you can reuse them in your final design.
Is this just a test baffle? If it is, take driver cutout placement into consideration, so you can reuse them in your final design.
I should have mentioned that the 48" baffle is the middle plane of the H frame just like CHOPS dipole subwoofers. It will be powered by 4 channel GC, one channel per driver from active crossover....initial thought from 80-100hz down push pull.
It is not going to be a test baffle if sounds good...
So should I still mount them as close together as possible?
Chris
It is not going to be a test baffle if sounds good...
So should I still mount them as close together as possible?
Chris
Yep, you want to mximize the dimensions of the baffle, which generally means mounting in the middle.
Steve
Steve
Why so big then? I'd have some concern about cavity resonance with that size unless the wrap around pieces aren't very deep. If it only needs to go up to 100, I'd do a W baffle. If it's good enough for SL, it's good enough for me. The one I made is only 15"x15"x19"deep using 12's and it does well into the 30's with no EQ and that's with cheap drivers of unknown specs.
If it's for something like a false stage for an HT setup, I understand the design, but I'd still lay it on its side and put them close together at the bottom. Did you have some special use in mind in addition to being a sub?
If it's for something like a false stage for an HT setup, I understand the design, but I'd still lay it on its side and put them close together at the bottom. Did you have some special use in mind in addition to being a sub?
It is just a 24"x24"x48" H frame. It is not for HT. It will be two subwoofers for stereo use only. I am only using 2 way out of a 3 way active crossover at the moment. With the extra 4 channel GC I am going to try dipole subs and relief the Jordon JX150 seal boxes from either 80hz or 100hz down or even 60hz down since the crossover can adjust the low pass with a dial. I am more or less copying CHOPS with same size H frame but different and smaller drivers.
Chris
Chris
Chris,
If you've got the room and don't care about the size, then go for it. One question though, what drivers are you using? If they are very high Qts then you could get a big bump in response at Fs and want to be more scientific about your baffle dimensions to make it work to your advantage. If they are low Qts drivers then you'll need to EQ to force them to make bass in the open.
If you've got the room and don't care about the size, then go for it. One question though, what drivers are you using? If they are very high Qts then you could get a big bump in response at Fs and want to be more scientific about your baffle dimensions to make it work to your advantage. If they are low Qts drivers then you'll need to EQ to force them to make bass in the open.
Qts is low
MAX Performance, discontinued line, bought them cheap for $85cdn each..
Power==175W RMS
PEAK==350WATT
Imp==4 ohm
RDC==2.8 ohm
Fs==25Hz
Qes==0.62
Qms==2.9
Qts==0.51
Vas==248L(8.75cu.ft.)
Xmas==+/-6mm(0.24”)
Travel==1.1”
No%==0.627
BI=6.8TM
Mms==64G
Sd sq.M.==0.0531
MAGNET==56oz
SIZE==12”
Features
2" 2 layer voice-coil on aluminum bobbin
chrome ion deposited polypropylene cone with stress relief rings
Rubber surround
++++++++++++++++++++++++++++
I will most likely place it with your suggested way the long side on the floor and use it as a stand for the JX150 100litre seal box, so that I should still have around 5 foot space between them for access to the dvd player and preamp..
Chris
MAX Performance, discontinued line, bought them cheap for $85cdn each..
Power==175W RMS
PEAK==350WATT
Imp==4 ohm
RDC==2.8 ohm
Fs==25Hz
Qes==0.62
Qms==2.9
Qts==0.51
Vas==248L(8.75cu.ft.)
Xmas==+/-6mm(0.24”)
Travel==1.1”
No%==0.627
BI=6.8TM
Mms==64G
Sd sq.M.==0.0531
MAGNET==56oz
SIZE==12”
Features
2" 2 layer voice-coil on aluminum bobbin
chrome ion deposited polypropylene cone with stress relief rings
Rubber surround
++++++++++++++++++++++++++++
I will most likely place it with your suggested way the long side on the floor and use it as a stand for the JX150 100litre seal box, so that I should still have around 5 foot space between them for access to the dvd player and preamp..
Chris
Speaker stands is the ideal location, but it makes a W baffle even more desireable because of the limited cabinet vibration. In a W config the mechanical energy of the drivers offset each other. Then you'll have a nice small stand for putting the Jordans on a smaller baffle with some small wings for support and a little extra baffle width. Dipole bass is great, but dipole midrange is to die for.
Before you build anything, take a 4ftx4ft or 3ftx4ft piece. Mount the 2 woofers in the bottom and one of the Jordans a little off center. Is likely to turn into your whole speaker at least until you decide to fancy up your baffle.
Before you build anything, take a 4ftx4ft or 3ftx4ft piece. Mount the 2 woofers in the bottom and one of the Jordans a little off center. Is likely to turn into your whole speaker at least until you decide to fancy up your baffle.
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