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Old 20th February 2018, 02:04 PM   #111
Skylar88 is offline Skylar88  South Africa
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Quote:
Originally Posted by kking85743 View Post
I am aware of the home-made inductor you made, and I believe you ended up with an air-core inductor with a 50mm interior diameter, and something like 123 turns. How wide was the coil (distance between the end-boards on the pipe)? I tried back-calculating info on the link you provided, and had real trouble getting 0.9mH. Can you clarify? I also believe you ended up with a 1 ohm resistor in parallel with the coil. Is that correct? More interested in starting from a known point, so I'd rather match your configuration than start with an experiment. Once I have a baseline, I can try to mess with it, if I my ears are different than yours.

The coil is 20mm high (wide). I used to use a 1.5 Ohm resistor, but am now listening with 2.2 Ohm. It dampens the highs a little more.

But as X said, adjust (the resistor) to taste. I'd start with 2.2 Ohm and try a few other values, between 1 and 4.7 Ohm to hear the difference.
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Old 20th February 2018, 03:36 PM   #112
Skylar88 is offline Skylar88  South Africa
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Default Inductors

I have used the M0UKD Air Cored Inductor Calculator to design my 0.9mH inductors. The values used were:
Coil diameter: 51.2mm (center to center of wire)
Coil length: 20mm
Number of turns: 123
(I kept the default 1.850 frequency)
The result is a 0.9mH choke. I've used 1.2mm wire for very low resistance (0.29 Ohm).

The coil length should have been18.8mm to the center of the wire, but even with that correct, the inductance doesn't vary much (0.94mH). 120 Turns would make it 0.895mH.

Play around with the calculator and see what you get.
Attached Images
File Type: jpg 0.9mH_inductor_thick_wire.jpg (78.6 KB, 316 views)
File Type: jpg jig_inductor.jpg (251.4 KB, 319 views)
File Type: jpg 50mm_inductor_2.jpg (233.9 KB, 310 views)
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Old 22nd February 2018, 12:44 PM   #113
Eric is offline Eric  United States
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I've done the same thing with my Tang Band 1772 speakers and my FHXL with 10.3 metal cone drivers. Taming the highs was simple experimentation and made both speakers much more enjoyable to me! I rather enjoy the tweak-to-taste approach to dialing in the response curve for my speakers.

Both are excellent candidates for the ACA!
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Old 22nd February 2018, 06:59 PM   #114
xrk971 is online now xrk971  United States
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You know what would be an interesting thing is a Karlsonator made for qnty 3 3FE25-16 in parallel (nominal 5.3ohm load). That would even be more sensitive at 2.83v.
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Old 24th February 2018, 09:24 PM   #115
Lingwendil is offline Lingwendil  United States
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What would that make, something like 100db for 1 watt?
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Old 24th February 2018, 10:16 PM   #116
planet10 is offline planet10  Canada
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Hard to say. The spec says 90 dB sensitivity and 1W/1m, but sensitivity would be 2.83 V into 16Ω which is a half-watt. So they could be 90 or 93 dB 1W/1m depending on which part of the spec is a mis-truth. Add a secound driver get 3 dB more level, add 2 more for 3dB more, and adjust for impedance. Sensitivity & 1W/1m will be different.

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Old 17th March 2018, 10:34 PM   #117
kking85743 is offline kking85743
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Hey Skylar88 & xrk971

I've been looking at the frequency response of the 3FE25-16, and noticed that there's a bump at 2kHz, and that there is a rise starting at 3k, passing thru about +6dB at 6k and on to about 10-12dB at 12k before falling off. I presume these are the 'honk' and 'ear fatigue' peaks mentioned in discussions about the baffle step circuit.

However, looking at what Skylar88 is using (0.9mH & 2R2) and putting it in a simulation with 7.5 ohms as the load, about the average between 3k & 12k (based on the graph provided by the manufacturer), I got about a 2dB cut way earlier than expected and being about 1dB down at about 450-500Hz. Using a similar inductor and the 4R7 recommended by xrk971, I got about 4dB of hi freq cut, with the curve passing thru the -2dB point at about 700Hz.

This is not what I expected to see, based on what was discussed. In theory, if I read it correctly, I was expecting the filter not to start cutting until about 1k (which, based on what the speaker graph, seems to be a bit early). I played with the circuit to try to get the silly thing to do what I think it should do (start cutting around 1K, show some decrease by 3k, -6dB at 6k and -12dB at 12k) and ended up with a 0.3mH (at 0.3 ohm) and a 47 ohm resistor. I got about -2dB at 3k, -7.5dB at 6k and -10dB at 12k. However, it was still dropping like a rock, so by 20k, it was down over 14db and still falling.

I obviously don't understand something. I thought the baffle step was there to help level the speaker response. Am I getting a little carried away?

PS -Skylar88 - I tried building the same inductor you did, and came up with (using a $12 kit inductor-meter) 0.903mH and about 0.7 ohms for 17ga wire (a little thinner than yours). The online calculator came out better than expected. I used 2" outer diameter (50.8mm) plumbing adapter, cut to 20mm long and plates bolted on each end as a form.
Attached Images
File Type: jpg 3fe25-16FreqResp.jpg (70.7 KB, 166 views)
File Type: jpg 900uH_2r2.jpg (140.9 KB, 162 views)
File Type: jpg 900uH_4r7.JPG (146.2 KB, 27 views)
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Old 17th March 2018, 11:36 PM   #118
Lingwendil is offline Lingwendil  United States
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You may want to try a line level BSC circuit, the one Rod Elliot outlines is simple, effective, and adjustable via pot. Less interaction with the speaker itself.

Baffle Step Compensation

Or here-

Passive Line Level Baffle Diffraction Step Compensation
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Old 18th March 2018, 12:55 AM   #119
Skylar88 is offline Skylar88  South Africa
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Quote:
Originally Posted by kking85743 View Post
PS -Skylar88 - I tried building the same inductor you did, and came up with (using a $12 kit inductor-meter) 0.903mH and about 0.7 ohms for 17ga wire (a little thinner than yours). The online calculator came out better than expected. I used 2" outer diameter (50.8mm) plumbing adapter, cut to 20mm long and plates bolted on each end as a form.
Good to know, Ken. Thanks for confirming that the calculator can be trusted. Btw, I have been listening to my dual driver K's, without and with BSC. There is quite a reduction in SPL with the BSC. If my ears could handle the natural high frequency boost (of the dual drivers), I would much rather go without the BSC, in combination with the fleawatt ACA and B1 buffer.

In hindsight, the B1 may not have been the best preamp option for the ACA in my system. I'm therefore planning to build a new preamp with gain (AKSA Lender) to hopefully get better SPL out of the ACA and Karlsonator (with BSC) combination. I know the Karlsonators can do it, but whether the ACA can deliver more remains to be seen.
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Old 18th March 2018, 01:09 AM   #120
xrk971 is online now xrk971  United States
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If you make the Alpha 20, you get the Aksa Lender Preamp as the front end to the amp and 20w which should be more than enough for the Karlsonator. I never used a BSC on my Karlsonators - I always felt they were pretty well balanced and not too bright. But then never had a dual 16ohm one.

KKing, the BSC May prove to be different if you model the speaker with appropriate elements equivalent to real driver (RLC equivalent of TS parameters).

I can run a simulation in Akabak with and without BSC and let’s see how it looks.
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