Inductor calculations for Zaph B3S

[sbrtoy]

Greetings all,

I am in way over my head in projects...sooo many fun toys to build and so little time!

I am building one of the projects off the Zaph Audio site using the Hi-Vi B3S 3" driver, and the XO requires a .08mH inductor. I couldn't find this available anywhere so I ordered a .1mH from Madisound.

On Zaph's page he recommends using Lalena's inductor calculator to determine how much to unwind to make it into .08mH, sounded simple except the calculator requires input of spool length. The diameter I have, gauge I have, spool length...uhh no. Nothing is mentioned on this spec anywhere I can find on Madisound or any other coil suppliers...could someone guide me as to how to determine this without unwinding the whole thing?

[Ron E]

First off, Madisound will unwind it for you for a 10% upcharge on a larger inductor.

Inductance scales as the number of turns squared.
Count the number of turns across the coil and then from the inner diameter to outer. Multiply these together and you have the number of turns. Call this N1.

L1/L2 = (N1/N2)^2
N1/N2 = sqrt(L1/L2)
N2=N1/sqrt(L1/L2)

N2=N1/sqrt(0.08/0.10)

The number of turns to remove is just (N1-N2)

pretty simple, eh?

[owdi]

Since you need to make a precision strike on the peak in response at 8200hz, I recommend you build an impedance jig to measure your filter. So long as your soundcard has a headphone output, all you will need to do is hack up a 3.5mm to 3.5mm cable, add a resistor and two alligator clips.

http://www.partsexpress.com/pe/showd...number=240-095
http://www.partsexpress.com/pe/pshow...tnumber=004-30
http://www.partsexpress.com/pe/showd...umber=360-150#

Use Limp to measure the impedance. Download the manual and refer to figure 3.1 on page 8 for how to build the impedance jig.

http://www.fesb.hr/~mateljan/arta/download.htm

Dan

[chubby chaser]

Ive seen this problem pop up on another thread without conclusion.(jaygeorge 1979)
The problem is everyone is running the numbers on the Lalena calculator and putting in the wrong values. When the coil length is asked for dont put in the overall length of the wire in the coil. The site is looking for the width of the coil. A better example of this is located at http://www.pronine.ca/multind.htm. (this site has an example) A picture is worth a thousand words.
I ran my numbers on the pronine site for my coil and it looked like this.

pe 255-020 jantzen .10 mh 20 awg air core inductor

Inductance (L): .10
Coil Inner Diameter (d): .75
Coil Length (l): .375
Wire Gauge: 20 AWG
Number of Turns (N): 63
Turns per Layer: 11.23
Number of Layers: 5.61
Coil Outer Diameter (D): 1.15
Wire Diameter: 33.4 mil
Wire Length: 14.89
DC Resistance (R): .15
Ohms

Now to run the numbers for a .08 coil .
I
nductance (L): .08
Coil Inner Diameter (d): .75
Coil Length (l): .375
Wire Gauge: 20 AWG
Number of Turns (N): 58
Turns per Layer: 11.23
Number of Layers: 5.17
Coil Outer Diameter (D): 1.15
Wire Diameter: 33.4 mil
Wire Length: 13.46
DC Resistance (R): .14
Ohms

So the pronine site tells me that I need to remove 5 coils to come up with .08 mh.
I ran these nunbers through the lalena calculator and it told me to remove 6 coils to come up with .08 mh. Go figure.
I removed 21 1/2" 6 coils.
I tested the crossover out with the b3s in a plywood test box with a old towel shoved inside and it sounded pretty clear. It would ease my mind if someone else with a lc or lcr meter acturally tested this out with the calculators and then the meter and post their findings. I thought the jaygeorge 1079 thread was heading in that direction but he dropped the ball after getting his coils read then cut by a meter at his school and didnt document his findings. To be young again............

[chubby chaser]

Surely someone has slapped a lc or lcr meter on a .10 air coil too bring it down to a .08. Dont be shy speak up.

[holdent]

Why not just buy a 0.08 mH ALPHA-CORE air core inductor from Parts Connexion at http://www.partsconnexion.com/catalog/inductors.html? Part #ACORE- 59032 is a 12 gauge 0.08 mH one ($13.63 each), and the #ACORE- 59053 is a 14 gauge one ($9.96).

[chubby chaser]

Thats sort of like throwing money at the problem. Im getting a kick out of trying to do this cheap. This Zaph set up is a surround sound system for my wifes home gym. I seized the opportunity to build dyi style for her room first then the big build for the living room. She wanted something small and cheap in her room. So I picked up a sony strdg510 from BB for $99.00.
I guess over kill would be to fly John out to the house and pay him by the hour to build my speakers here. LOL <------- a little overboard wouldnt u say? {Sorry John Im not at that stage yet.}
I am aware I could throw the money at the problem and make this thread go away but I am trying to enjoy my builds and share my progress and problems with this site. Hopefully I may make a friend or two in the process. Its a learning process for me more like a hobby than a necessity. I guess I did sort of admitted defeat resently though. Best Buy had their sale on Klipsch Quintet III satelites and Synergy Sub -10 so i picked up a pair for the living room. Allot of things prompted that move. PE having their price increase before the first of the year, I missed the sale on the $99.00 Bash 300W sub amp, the BB sale at the same time, low traffic in the threads I participated in (at times I need moral support). Heck I even have to learn how to post pictures. My camera is producing pictures at 3,000,000 plus bytes and this site only accepts max 102400 bytes. I have to take the time to figure out how to reduce my photos bytes. Busy busy busy I am. Ill give this thread another day or two then just buy the PE 255-602 foil inductor.

[chubby chaser]

I have system finished but not mounted yet. I built a closed box sub for this 5 spkr system with a 10" dayton dvc woofer w/100watt sub amp. I have two extra spkrs built for rears in another room. Total b3s built 7. I really like the way the recessed speaker looks on the baffle.

[chubby chaser]

Here is a close up of baffle

[chubby chaser]

and here is the sub