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Old 6th October 2007, 11:55 AM   #51
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Default T/S parameters for the D5nf & D9nf

Well, I'll tell you that I don't really know what I'm doing when I use it, but I do have a simple Woofer Tester Two that I have used to take basic measurements of some of the drivers.

Click the image to open in full size.

Here is what I have for the D9nf:
Revc = 15.0239 ohms
Fs = 63.7892 Hz
Zmax = 242.4445 ohms
Qes = 0.4280
Qms = 6.4784
Qts = 0.4015
Le = 0.8499 mH (at 1 kHz)
Diam = 180.0000 mm ( 7.0866 in )
ConeArea =25446.9030 mm2( 39.4428 in2)
Vas = 22.8764 L ( 0.8079 ft3)
BL = 18.6603 N/A
Mms = 24.7485 g
Cms = 251.5342 uM/N
Kms = 3975.6030 N/M
Rms = 1.5311 R mechanical

(For what it's worth, the D9x series seems to be extremely easy to work with in bass reflex boxes. They have sounded good in a number of boxes that they have been tested in, ranging from 70 liters to 110 liters in volume. Joe Cohen, who is preparing to demo them in 110 liter enclosurres at RMAF, just called me on the phone a few hours ago and told me that the bass he's getting out of those cabinets is "astoundingly deep -- 'right through the floor' -- and incredibly beautiful." Mr. Teramoto and his enclosure maker arrived at the port dimensions by a very scientific method -- they just guessed: "That ought to be about right." It's just a square hole cut in the baffle. When Mr. Teramoto told me, I said to him, "You're going to RMAF and you just guessed at the parameters for the box? You like to live dangerously, don't you." To which he replied that these drivers will produce great bass in just about any box and there's no need to worry about it . . . which appears to be the case.)

Click the image to open in full size.

Here's the same Woofer Tester Two data, this time for the smaller D5nf driver:
Revc = 14.5706 ohms
Fs = 107.8037 Hz
Zmax = 159.5979 ohms
Qes = 0.6515
Qms = 6.4850
Qts = 0.5920
Le = 0.4430 mH (at 1 kHz)
Diam = 105.0000 mm ( 4.1339 in )
ConeArea = 8659.0145 mm2( 13.4215 in2)
Vas = 5.4951 L ( 0.1941 ft3)
BL = 7.9544 N/A
Mms = 4.1769 g
Cms = 521.8188 uM/N
Kms = 1916.3741 N/M
Rms = 0.4363 R mechanical

The D5nf seems to be a bit harder to design an optimum box for, but it has been around longer and there are a few decent designs. Here is a diy rendition of Feastrex's original enclosure, about 33 liters, which is very good when properly set up but not always the easiest to use on account of its dimensions:

Click the image to open in full size.

Here is a protoype 50-liter enclosure from Feastrex that looks like it would be easier to use:

Click the image to open in full size.

The passive radiator could easily be replaced by a port, either on the front or the rear of the enclosure. You can note in the photo that the protruding base on the enclosure is removable. I believe it bolts onto the bottom of the enclosure. Of course, it is just a prototype, but probably any box of about 50 liters capacity would work. If I was to do it, I would cut a hole in the baffle that would accept a PVC pipe with a tight force fit, and cut and try different lengths of pipe to find the length that worked best.

I'm certainly no expert, but when I look at the Feastrex enclosures for the smaller drivers, I think they are best described as "4th Order Large Vented Enclosure with Low Tuning" ("Extended Bass Shelf" or EBS). Scroll down this link for an explanation

In any case, assuming Mr. Teramoto is in fact able to learn how to use is speaker measurement system at RMAF, more substantial measurements should not be long in coming.

-- Chris
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Old 6th October 2007, 12:05 PM   #52
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Aha. Cheers Chris. I'll see what I can come up with for them.

I can't say I'm sold on the idea of 'pick a box, cut a random hole & say that'll do' though the specs suggest the larger unit at least should be versatile. We should be able to do better than that.
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Old 6th October 2007, 12:33 PM   #53
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Default D9nf dimensions

I have attached a PDF file showing the physical dimensions of the D9nf driver. The dimensions for the D5nf will follow later. I've never done this before; I hope it works . . .
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Old 6th October 2007, 12:46 PM   #54
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OK here's one idea for the D9nf based on the specs. you gave above. I'm increasingly a believer in the KISS approach, given that I've need numerous complicated cabinets give no better (frequently worse) results than something stupidly simple.

Like this Shadow style box.

Cabinet is 260mm wide x 300mm deep. Upper chamber is 450mm tall (for 35 litres) driver mounted 150mm down from the internal top. Downward firing slot 18mm deep at the rear of the bottom panel, full width of the cabinet, 18mm long (thickness of the build material), feeding a rapidly flared vent 381mm tall at the front. Strike-plate starts 25mm down from the slot. Similar layout to the attached, though the slot doesn't need the extra panel, as it's only the length of the material-thickness, & the flare won't look as skinny.
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Old 6th October 2007, 12:47 PM   #55
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Frequency response should be ~flat to 50Hz.
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Old 6th October 2007, 12:50 PM   #56
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The T/S parameters you provided suggest impedance is a bit fierce with this driver, but no worse than a lot of other units.
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Old 6th October 2007, 12:51 PM   #57
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Xmax wasn't mentioned, but excursion is pretty low for 1w in this box.
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Old 6th October 2007, 12:58 PM   #58
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That's awesome! 0.2mm of excursion and 2mm of excursion are the same to these drivers. They can do 2mm all day long while singing and not even break out in a sweat.
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Old 6th October 2007, 01:06 PM   #59
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Then they're going to go loud. Very loud. And with the large area of air these boxes will couple to in the LF, they're going to sound big.

They'll also go straight into Chang, no mods needed. http://homepage.mac.com/tlinespeaker...map-140807.pdf
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Old 6th October 2007, 01:25 PM   #60
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The doubled box is tuned ~10Hz lower as shown above. As you can see, excursion is no higher than for the single version.

I normally try not to overload threads up with multiple posts of graphs but I wanted to make an exception in this case for several reasons. a) because they're unusual drivers clearly showing a lot of personal effort / artistry involved in their design, and b) as my quiet response to some remarks elsewhere.

I'll look into the smaller unit next. I'd love to do something for the Alnico & field-coil units too at some point.
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