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delahais
09-24-2003, 02:46 PM
hello,
i would like to know the formula for attenuations of tapped autotransformer, if someone can help me, thanks. :wave:

4313B
02-10-2005, 02:37 AM
Question: 09-24-2003, 05:46 PM
Answer: 02-10-2005, 05:37 AM

Is that service or what!? :p

Ok. I put this graphic together after lifting the tapped autotransformer pic from here - http://www.allaboutcircuits.com/vol_2/chpt_9/5.html

This is something I've been meaning to put together for a very long time.

I am indebted to David Smith for supplying the fundamental formulas for my spreadsheet.

4313B
02-10-2005, 02:51 AM
Modeling a tapped autotransformer courtesy of David Smith.

4313B
02-10-2005, 02:55 AM
Another model using my software showing the spice data

David's LEAP Crossover Shop software is better in that it automagically calculates the secondary inductance value. ;)

Guido
02-10-2005, 03:22 AM
Hey,

good stuff :) Thanks.

Is there some formula to convert it to this series and parallel R/L substituting circuit?

You somewhere posted this for the 3145 network but it would be useful to be able to convert all the other networks with these tapped AT's

4313B
02-10-2005, 03:36 AM
Is there some formula to convert it to this series and parallel R/L substituting circuit?Not that I know of. Those conversions were all done the hard way. Greg Timbers supplied the original voltage drives along with a few suggestions and I had to plug and chug until the voltage drives looked identical. I never did get around to doing the 4315, L65, S21, or L220. I think Tim G might be able to import voltage drives into SoundEasy and do something with them.

delahais
02-11-2005, 01:54 PM
Question: 09-24-2003, 05:46 PM
Answer: 02-10-2005, 05:37 AM

Is that service or what!? :p

Ok. I put this graphic together after lifting the tapped autotransformer pic from here - http://www.allaboutcircuits.com/vol_2/chpt_9/5.html

This is something I've been meaning to put together for a very long time.

I am indebted to David Smith for supplying the fundamental formulas for my spreadsheet.


hello,
i just see (saw?) your post, you don't forget me !
i'm very happy ...
very good post, thanks. fonzy

Bruno GINARD
02-12-2005, 12:07 AM
Hi Fonzy,

I send you a P.M about this case:applaud:

Regards

Guido
02-12-2005, 12:48 PM
Not that I know of. Those conversions were all done the hard way. Greg Timbers supplied the original voltage drives along with a few suggestions and I had to plug and chug until the voltage drives looked identical. I never did get around to doing the 4315, L65, S21, or L220. I think Tim G might be able to import voltage drives into SoundEasy and do something with them.

OK, so building 4315, L65, S21, or L220 will be a challenge :(
At least we have the 3145 circuit.

Zilch
02-12-2005, 12:58 PM
Somebody should give us a little tutorial here. What's this about? How does it apply?

4313B
02-12-2005, 02:37 PM
55030 Tapped Autotransformer

In this particular instance, used to make the 52978 "1.55mH" tapped autotransformer in the LX80/LX80A/LX300/N333/3131/3133

4313B
02-12-2005, 02:38 PM
Tapped autotransformer shown above measured:

red to black - 1.51 mH 0.69 ohms DCR
1st yellow to black - 0.39 mH 0.48 ohms DCR (-6 dB)
2nd yellow to black - 0.27 mH 0.42 ohms DCR (-7.5 dB, spec'd as - 8 dB)
orange to black - 0.14 mH 0.39 ohms DCR (-10 dB)

red to 1st yellow - 0.36 mH 0.46 ohms DCR (-6 dB)
red to 2nd yellow - 0.52 mH 0.48 ohms DCR (-4.5 dB)
red to orange - 0.75 mH 0.52 ohms DCR (-3 dB)



Using the fomulas posted in #2 above for a 1.51 mH inductor:

4313B
02-12-2005, 03:12 PM
Somebody should give us a little tutorial here. What's this about? How does it apply?It's a way to model tapped autotransformers to simulate voltage drives. Once the voltage drive has been simulated one can replace the tapped autotransformer with resistor pads and regular inductors which will yield the same voltage drive. It's probably easier to do with something like SoundEasy or LEAP Crossover Shop than with something like pSpice.

Bruno GINARD
02-13-2005, 03:09 AM
Hi all,

After a PM exchange with Giskard, i would like to inform you about the availability of autotransformers :

2 months ago , i had a talk with a FRench Hartsfield owner ( a Classic Audio Repro) about autotransformers versus L Pad.(IMO L.Pad are ALL poor quality and very imprecise component).

He gave me the information that this kind of transformer was available at SOWTER UK, as a particular order.

http://www.sowter.co.uk/

Then, we decided to order 10 of them in January.THey are on the way from UK to France for the present.
The conditions of the contract included 9 positions, from -1 to -10 db.Contrary to the JBL original parts, those transformers DO NOT includes the L circuit. THerefore you have to instal the inductor separatly, thus the 10 stepped selector with the different resitors in front of the circuit.( scheme included)
The price of each transformer is about 140 /180 $ without local taxes.

I hope it could help!

Warmest regards,

4313B
02-13-2005, 06:58 AM
Measured impedance curve of 1.55 mH tapped autotransformer without and with preceding 7.5 ohm parallel resistor.
This is the load the 16.5 uF capacitor sees.

Earl K
04-05-2005, 07:01 AM
Fantastic Info !

- I thought I would pop this up to the surface for some air , given Teds inquiry.

( - Tapped inductors vs Lpads ought to be a fascinating debate . )

:D

4313B
04-05-2005, 07:54 AM
Tapped inductors vs Lpads ought to be a fascinating debateOk, let's debate. I'll start:

The tapped inductor is a PITA.

You have the reactive inductance to deal with so a parallel resistor is necessary anyway. Just use a series resistor with that parallel resistor and call it a day. A tapped inductor for a passive loudspeaker filter is an expensive solution to a simple problem. There are plenty of very nice non-inductive resistors available today.

The issue of heat is also faulty because the resistor required in front of the tapped autotransformer can generate a tremendous amount of heat so the lack of heat from the tapped autotransformer is negated. Some of the closed cans like the LX5 were "ok" but remember the mesh grilles on the 4331/4333 networks so those 40 ohm 40 watt monsters could keep cool? How many of you have seen those resistors after continuous high power use? :p

Just use gangs of non-inductive resistors like Mills manufactures.

Counterpoint?

Earl K
04-05-2005, 11:39 AM
Ok, let's debate. I'll start:

Hell, I can't debate you on this,,,, I've paid zero attention to the "sound of resistors"... I'm still over in capacitor land somewhere ,,,,, :p

( Plus, I happen to agree with all your points,,,especially; PITA )


Counterpoint?

Anyone else on a flyby from AA / HE ?

Ian Mackenzie
04-05-2005, 11:56 AM
Any easier way is to piss off these crappy hi sensitivity drivers and use a selection of components that a well matched in terms of sensitivity like everyone else.

Isn't that a bit more sensible?:dont-know

4313B
04-05-2005, 12:01 PM
Yep, could be...

High efficiency system down to ~ 80 Hz and then 2242H subs with boat loads of power to fill in the bottom...

Ian Mackenzie
04-05-2005, 12:14 PM
Hey,

Now that's a big set of headphones!

Ian