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Old 15th March 2004, 04:56 PM   #1
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Default Goldwood 18" for OB sub

Well I was playing around (for the first time) with the xbaffle open-baffle spreadsheet to see how the Fostex FE206E and the 18" Goldwood GW-1858 driver looks for open baffle use. _Here are my results. _The Goldwood driver looks promising, at least compared to the emminence driver. _The FE206E obviously does not have any low end in an open baffle. I'm not sure how accurate this spreadsheet is to real-world results/sound. _A crossover point of 200hz looks like a good starting point for the Goldwood. _If the FR graph is to be believed, that 104db bump at 45hz of the 1858 compensates nicely for the low end drop off when used in an open baffle.

Room Response: http://www.speechstreet.com/temp/gw1858_ob_room.gif
Frequency response: http://www.speechstreet.com/temp/gw1858_ob_fr.gif

spec's and baffle sizes used for calculations...

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _Fostex _ _ _Goldwood _ _ _Eminence
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _FE206E _ _ _GW-1858 _ _ _Gamma Pro 15CX
Driver Resonant Frequency (Fs - Hz): _ _ _39.00 _ _ _30.00 _ _ _43.00
Driver Electrical Q (Qes): _ _ _ _ _ _0.18 _ _ _1.07 _ _ _1.00
Driver Mechanical Q (Qms): _ _ _ _ _ _3.73 _ _ _6.65 _ _ _6.55
Driver Equiv Volume (Vas - liter): _ _ _54.53 _ _ _524.00 _ _ _225.00
Thermal Power Limit _ (P - VA): _ _ _ _ _ _90.00 _ _ _220.00 _ _ _200.00
DC Resistance _ _ _ _(Re - Ohm): _ _ _6.69 _ _ _6.20 _ _ _5.80
Pk-to-Pk Excursion (Xmax - mm): _ _ _ _ _ _1.50 _ _ _3.36 _ _ _8.00
Effective Cone Dia. _ (D - mm): _ _ _ _ _ _162.00 _ _ _406.00 _ _ _350.00
Baffle Width (mm) _ _ _ _ _ _ _ _ _ _ _380 _ _ _750 _ _ _750
Hight above floor (mm) _ _ _ _ _ _ _ _ _ _762 _ _ _618 _ _ _618
Dist. rear Wall (mm) _ _ _ _ _ _ _ _ _ _1618 _ _ _1618 _ _ _1618
Dist. side Wall (mm) _ _ _ _ _ _ _ __ _ _1000 _ _ _1000 _ _ _1000
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Old 15th March 2004, 05:17 PM   #2
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You may also want to look at Studio Pro 18" PW1808-US, lower Fs, higher x-max, although it does have a bit lower Qts...

Peace
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Old 15th March 2004, 05:26 PM   #3
sreten is offline sreten  United Kingdom
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Hi BB,

I'm a little confused.

How did you arrive at the huge bump at 45Hz, with a
driver supposedly having a Qts of ~1.1 at 30Hz ?

sreten.
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Old 15th March 2004, 11:44 PM   #4
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What about the dayton 15" ib woofer with 14mm xmax? it will have much more Vd than a tiny xmax 18" of cheaper quality.

If i could fit an IB,or dipole and amps,id try this out due to people here loving the sound of dipoles :-D

dayton 15"

Excuse my sillyness-but WHICH graph do i take note of!
there are 3 the same...

because the FR (onewoofer) looks good,yet the graph on the driver input page,and room response looks bad...

Cheers
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Old 16th March 2004, 12:29 AM   #5
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I'd be concerned with the low xmax of the goldwood. You might want to calculate how much SPL you can get with the goldwood before you run out of travel. i suspect it wouldn't take much power at all to run out of xmax at 30Hz or so.

This is very similar to what I've been planning -- Fostex FE206E along with an Eminence Kilomax-18. I've got the eminence running with right now with some temporary mids and a tweeter. The Kilomax is moving a fair amount -- way more than 4 mm.

- Robert
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Old 16th March 2004, 12:43 AM   #6
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I "arrived" at the bump by looking at the response graph that Goldwood sent me. You can see it by clicking on the "104db bump" link I posted above.

I saw that Pyramid Studio Pro driver, and yes it also looks good. I could not find a response graph for it though, or who to send an email to in order to get it (like I did for Goldwood). Anyone know where is the Pyramid home page?

That Dayton driver is too inefficient for my taste.

I'm not so concerned with the xmax as I'm planning on running 2, or maybe 4 drivers total, so things would have to get aweful loud before I start hitting the xmax limit.

The Kilomax driver looks good, but I question if it's worth the extra money, when you can get 4 of the goldwood drivers for less. I'm not convinced that you have to spend allot on drivers for open baffle use. Also, what's it's efficiency, I couldn't find it? And the FR graph doesn't plot the impedance - though the Zmax is quite high.

I may put a couple other drivers through the spreadsheet and see what happens. Or, someone else could do it for the Kilomax, and Pyramid?
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Old 16th March 2004, 01:28 AM   #7
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Here's the comparison of the Pyramid driver to the Goldwood via the spreadsheet. They performance looks almost identicle (as is their price), in this sim/spreadsheet anyway...

Frequency Response: http://www.speechstreet.net/temp/gol...pyramid-fr.gif

In-room (whatever this is really representing?)...
http://www.speechstreet.net/temp/gol...ramid-room.gif

For me the interesting thing is if the Pyramid driver's Le as low as the Goldwood (.6 mH)? And what does the Pyramid impedance plot look like? Zmax?


Data for the sim...


XL-Baffle Version 0.9 - prerelease version
Fostex 8" Goldwood 18" Pyramid 18"
FE206E GW-1858 Studio Pro
Driver Resonant Frequency (Fs - Hz): 39.00 30.00 24.56
Driver Electrical Q (Qes): 0.18 1.27 0.91
Driver Mechanical Q (Qms): 3.73 6.65 8.12
Driver Equiv Volume (Vas - liter): 54.53 524.00 900.00
Thermal Power Limit (P - VA): 90.00 220.00 325.00
DC Resistance (Re - Ohm): 6.69 6.20 7.20
Pk-to-Pk Excursion (Xmax - mm): 1.50 3.36 4.60
Effective Cone Dia. (D - mm): 162.00 438.00 438.00
Baffle Width (mm) 380 750 750
Hight above floor (mm) 762 618 618
Dist. rear Wall (mm) 1618 1618 1618
Dist. side Wall (mm) 1000 1000 1000
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Old 16th March 2004, 02:05 AM   #8
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Here a comparison of Goldwood, Pyramid, and Eminence (Kilomax) 18" drivers...

http://www.speechstreet.com/temp/gol...minence-fr.gif

Although the Kilomax can handle tons more power, it doesn't look to be the best choice for open baffle bass response (if this spreadsheet is to be believed). The proof is in the hearing though - and baffle construction.

Again, given these are all "pro" drivers, they are ALL made to handle much more power than I believe they will see for audio use, at least in MY house. Especially since I will be running more than just one - ie, not just a single subwoofer.

I'm really hoping that this bears out, as it would be nice if you can get away with $70 drivers instead of $300 drivers for open baffle use.
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Old 16th March 2004, 02:56 AM   #9
DeonC is offline DeonC  South Africa
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Hi Brad

Have you considered the Goldwood GW215 15" drivers? When you compare them to the GW1858 in XL Baffle, they model flatter in the bass region than the 1858 (due to a higher Q). ITO peak SPL the 18" drivers give only about a 6dB advantage, but at the expense of a rising response. In the low bass there is little to choose between them. Here's the kicker though: the GW215 drivers cost only US$23 each at PartsExpress if you take more than four (which I assume you will be doing), so you can get THREE GW215s for the price of one GW1858. As long as space is not an issue (which it doesn't seem to be as you're contemplating more than one 18" driver per side) I think that the GW215 will be better suited to your needs. Three GW215 drivers are sure to be superior to a single GW1858. If you have the space you can mount six GW215 drivers per side on a baffle that will be about 8.5 feet tall . The cost will be the same as two GW1858 drivers per side, and should sound better (not too mention look a LOT meaner ).

Enjoy,
Deon
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Old 16th March 2004, 05:56 AM   #10
OMNIFEX is offline OMNIFEX  Jamaica
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bbaker6212

I'm a person that appreciates 18 drivers. With that being
said, I think you would be making a mistake going for the Goldwood 1858.

Eminence will stand by their published specs. Will Goldwood
do the same?

I understand you want an open baffle type bass system.

However, Goldwood 1858 has a no. of 0.873%, with a
xmax of 3.36 mm, where as the Eminence Killomax 18
has an no. of 1.433, and, an xmax of 9.8 mm

So, two Goldwood 1858's will be a tad under one Eminence
Killomax 18. This is of course Goldwood's TS Parameters
are correct.

Companies can get away making a cheap 15, 12, 10, and,
8 inch woofer. But, they can't with a 18, 21, or 24 inch
woofer.
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