Zobel for Tang Band W8-1808?

majerjack

Member
2010-02-20 11:57 am
For my first full-range speaker project, I have purchased a pair of Tang Band W8-1808 drivers, and have settled upon a simple bass reflex box as the cabinet.

I would appreciate hearing from others who have used this driver as to whether the use of a Zobel network is necessary. I would prefer not to use one, but am open to suggestions from those who have achieved better results with a Zobel than without. Please relate the network component values that worked for you, and if you prefer the driver without a Zobel, I would appreciate hearing that, too.

I am building a custom preamp with switchable baffle step equalization built in, so I will not apply BSC to the driver itself. Thanks to all who respond.
 

Bob Brines

Member
2003-01-31 10:11 pm
The primary purpose of a zobel is to flatten the high frequency end of the impedance curve so that the driver will work correctly with a cross over network. If the 1808 is anything like the 1772, you will have no need for a tweeter, and most folks let the full-ranger run wide open anyway.

On a single-driver speaker, a zobel is used to control the rising response of the driver, if any. In essence, the zobel is simply a contour filter and the component values won't necessarily be textbook values. I find a zobel mandatory on Fostex 166/206 but not on the 167/207 (now a mute point). You will simply have to listen to your speakers to decide if you need to tame the top end or not.

I will put a contour filter on a speaker in a heartbeat. I find that a balanced response far outweighs any deleterious effects of the passive components. However, I believe that the best approach is to do the contour shaping digitally or at least at line level as you have done with our BSC filter. None of my personal speakers have any passive components in the boxes.

Bob
 
I will put a contour filter on a speaker in a heartbeat. I find that a balanced response far outweighs any deleterious effects of the passive components. However, I believe that the best approach is to do the contour shaping digitally or at least at line level as you have done with our BSC filter. None of my personal speakers have any passive components in the boxes.

Bob

Hmm,
when I see sometimes 3 notch filters in series with the FR speaker, :confused:
Same feeling I have when "nothing is done", which seems to be preferred in the US.

Bobs approach makes sense:)

Joe
 
A nearby enthusiast has a pair of these drivers in a 40L ported cabinet, with BSC. It was definitely needed. Without it, the sound was too forward, and sounded very lean. Adding the BSC brought the bass back in line, with a more balanced listen overall.

These are extremely good drivers.
 

Bob Brines

Member
2003-01-31 10:11 pm
1808s or 1772s? If it's Colin's speakers we're discussing, it's the latter, which is a different driver. Q on the 1772 is about 40% lower, while Vas & B*L are both rather higher than the 1808.

Indeed! The 1772 will work in 40L, although I prefer 50L. The 1808 will need at least 60L, and any reasonable implementation of a box this size will have serious quarter wave issues.

Bob
 
Indeed! The 1772 will work in 40L, although I prefer 50L. The 1808 will need at least 60L, and any reasonable implementation of a box this size will have serious quarter wave issues.

Bob
Which is why I'm probably just putting mine in a 1.25 cf sealed box as soon as I can get around to it. I'm hoping someone will do the testing for me and post some good values for a Zobel so I can try it both with and without.

I am still toying with the idea of an open baffle with a couple of Emi Alpha 15"ers, but they're just so BIG, and I'm not sure they're going to sound that much better than sealed boxes on top of my Klipschs.
 
I wanted to avoid creating a new thread with the same question, but I have the need for experimentation. Regarding the value of capacitor / resistor, this is an inquiry that I posted to the Parts-Express W8-1808 page:


"I am a novice builder that has a set of these W8-1808 drivers. I am interested in calculating a Zobel network for them, and I think that I may be missing something… The two calculations that I have tried using states: R = 1.25 x Re, where Re is driver’s DC resistance in ohms [R = 1.25 x 6.8 = 8.5ohm], and: C = Lvc / (1.25 x Re²), where Lvc is the driver’s voice coil impedance in henries. The spec sheet of the driver (located above on this page) shows Le is 0.048mH, or 0.000048H: [C = 0.000048 / (1.25 x 6.8)² = .000000664 Farads, or .664uF]. For everything that I’m reading, the ending capacitance value of ~.664uF is much too low. Am I overlooking something crucial or missing my decimal placement? Thank you!"
 
Please reference attached spec sheet:
 

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