Which coils?

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Which coils?

Postby Vansloneker on Tue Sep 04, 2018 8:01 am

I decided I want to take the crossover for the Calipers external and leave the old x/o for what it is.
I found an inspiration here of how to make a neat crossover assembly.

There are two local suppliers,
http://audio.nl/Aprodview.asp?type=subl ... 0&b=80&c=0
and
https://www.rumoh.eu/en/spoelen?id_category=244&n=45
and I really have no idea which coil to choose from the huge supply. What does AWG stand for, the diameter of the wire?
I just want good coils, not the end of Hi-End.


This imageImage has all the values indicated. I hope they are correct.

I see one small coil: 0.1mH
one medium coil: 2.7mH
and one big coil: 2.0mH

And what resistors would be a good choice for R 8.06R and R 10R?
poor guy
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Re: Which coils?

Postby Scinemaniac on Wed Sep 05, 2018 12:16 am

Hi

AWG denotes thickness of wire used in each coil which, together with the number of turns, determines the resistance of the coil (measured in ohms).

When upgrading, try to match the resistance as well as inductance (measured in millihenrys). Or adjust the circuit to preserve frequency of crossover.

To know a coil's resistance (probably low in value) you could measure using a reliable LCR meter (expensive), or ask your supplier if he would measure for you. If you send him coils from one speaker and keep the coils from the other one, then you are covered in case they get lost in transit.

Coils wound from flat strip are thought to be slightly better, maybe because the construction is more rigid. But a good wire-wound coil and a good strip-wound coil will sound similar.

Apogee used air coils because they are more linear, lower in distortion. Of course it would be cheaper to use a coil with a ferrite core - but don't be tempted as it would have fewer turns and so different resistance, and give poorer sound.

Photos on Tony Gee's webpage show crossover components mounted close together on PCBs. If you must mount coils close to one another, arrange them orthogonal to avoid interaction between their magnetic fields. And mount them a minimum of one diameter apart.
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Re: Which coils?

Postby Scinemaniac on Wed Sep 05, 2018 12:46 am

I have used both Tritec (wire) and Jantzen wax foil coil (strip). Jantzen wax foil is better and more expensive. Both are excellent quality.

If you tell your supplier which value you want, you pay for a higher value and he can remove turns from the coil until the value drops to the value you want. He should measure and mark that it has the new value.

Careful,
don't order with ferrite core eg. "ferrobar".

pure copper "4N" is good.
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Re: Which coils?

Postby Vansloneker on Thu Sep 06, 2018 8:18 am

Thanks for your extensive reply Scinemaniac. Some interesting and important facts you brought up.
So when arranging the parts, the coils could be, schematic e.g.
Code: Select all
O  --
  |

where the lines represent a top view of a coil.
Will be a nice puzzle to sort when including the other parts.
But the high and low parts could be on different pcb's.

I don't think those web stores will provide customized coils. But the Apogee parts weren't that exact either I think to heave learned earlier.
I know Henk is able to rewind the coils as part of a full speaker restoration, but at the moment I am looking at a smaller step improvement.
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Re: Which coils?

Postby Scinemaniac on Thu Sep 06, 2018 9:26 pm

"I don't think those web stores will provide customized coils."

The purpose of this forum is to provide useful practical advice based on what has worked for us.
I have explained how I boughtmatched replacement coils, and how my supplier helped me.

Have you enquired of either supplier?
Don't just give up!
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Re: Which coils?

Postby Scinemaniac on Thu Sep 06, 2018 9:57 pm

About orthogonal,
yes that is it.

Magnetic field reduces sharply beyond an extra one diameter distance.
Some magnetic coupling may still exist, which might introduce other frequencies.
So if space, place coils apart.
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Re: Which coils?

Postby Vansloneker on Fri Sep 07, 2018 6:09 am

I hope someone comes up with a confirmation of the values including AWGs, or I have to open them and see if there's anything written on the coils.
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Re: Which coils?

Postby Scinemaniac on Fri Sep 07, 2018 11:44 am

huh (sigh)

the coils in Apogees were handmade in the factory from standard enamelled copper wire (not 4N copper), then tied down onto hardboard or perspex.
I've not seen them marked with a value, but maybe someone wrote on yours.

If you like reverse-engineering, unwind the coil entirely to measure the length, measure the diameter of the wire to determine the AWG. From these you could look up the total resistance.
From counting the number of turns, you can look up (calculate) the inductance.

When do you plan to examine the coils inside your speakers?
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Re: Which coils?

Postby apogee_admin on Fri Sep 07, 2018 1:19 pm

I have the info of the coils, will post later when I am home.

It will be possible to implement a signature type crossover, would need to check the mid/tweeter type, can you take a pic of the bottom connections of the mid/tweeter from the rear of the speaker.
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Re: Which coils?

Postby Vansloneker on Fri Sep 07, 2018 7:05 pm

Thank you Scinemaniac and Jon.
The duty called and I just went out for a couple of days and will produce the desired images when I returned home.
The ribbon has the return lead that much I can tell you.

By the way I am contemplating ribbon replacement as the next step.
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Re: Which coils?

Postby apogee_admin on Mon Sep 10, 2018 9:50 am

Realised I never drew a full circuit diagram for the Caliper Signature, the one somebody sent me is really confusing to look at as it included all the switch wiring without any legends for what was what!

Anyway, the bass coil is 1.85mH 12 AWG wire, the mid/tweeter 1.5mH 16 AWG and a small one 0.12-0.18mH 16-18 AWG for the top end circuit.

The Jantzen air coils are good at prices that don't break the bank.
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Re: Which coils?

Postby Vansloneker on Mon Sep 10, 2018 11:44 am

Thank you Jon!

What do these different values accomplish? A lower or a higher frequency switch point from the bass to the mid/high?
There are no changes to the caps, resistors and lay out?
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Re: Which coils?

Postby apogee_admin on Mon Sep 10, 2018 7:53 pm

Sorry didn't specify, the whole circuit is different for Signature, I will draw it up.
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Re: Which coils?

Postby Vansloneker on Wed Sep 12, 2018 5:28 pm

apogee_admin wrote:I have the info of the coils, will post later when I am home.

It will be possible to implement a signature type crossover, would need to check the mid/tweeter type, can you take a pic of the bottom connections of the mid/tweeter from the rear of the speaker.


Image

Is this picture of any help Jon?
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Re: Which coils?

Postby Graz on Fri Sep 14, 2018 5:02 am

Sorry, late in with this one, good advice above BUT - a couple of points;-

1) Values marked on original coils often is not accurate, sometimes way off

2) A good and cheap upgrade is to pot the ones you have in resin.

Bass coils are 12g, MRTW 18g.

All new coils here are actually produced in house on custom cnc machinery...


Take care - Graz
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