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Old 1st December 2012, 02:42 PM   #31
system7 is offline system7  United Kingdom
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Quote:
Originally Posted by tuantran View Post
Steve,
How will the speaker sound if replacing 2.7 Ohm by 3.9 Ohm resistor, 4.7 uF by 3.3 uF capacitor, 0.2 mH by 0.25 mH inductor for the tweeter?
That's going in the wrong direction really. You've got a low crossover on the metal drivers as is normal practice, but a high crossover on the tweeter. It just makes a huge hole in the midrange...

Notice how bad phase is on this speaker.
Attached Images
File Type: jpg Mon_Audio_RS6_3.3uF.JPG (58.9 KB, 105 views)
File Type: jpg Mon_Audio_RS6_3.3uF_Phase.JPG (52.5 KB, 103 views)
File Type: jpg Mon_Audio_RS6_3.3uF_Network.JPG (26.8 KB, 104 views)
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Old 1st December 2012, 03:21 PM   #32
PALUSE is offline PALUSE  Portugal
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Hi everybody.
Actually i found two 8,2 ohms, 5W resistors in my stock. If Steve confirm that this Zobel network dont affect cross over point between tweeter and mid drive, so, let it be as it is (8.2Ohms + 2uF).

Kind regards

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Old 1st December 2012, 04:21 PM   #33
system7 is offline system7  United Kingdom
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I will show you the modelling of the standard MA speaker without and with the Zobel. As you can see, it just rolls off the top end as predicted. Sounds far better to my ears with metal tweeters which have some issues at the top:
E0047-04 T29MF001

Click the image to open in full size.

Click the image to open in full size.

I can always hear a metal tweeter dome. They make classical piano sound metallic. But nice on rock and jazz drums.

Metal woofers have all sorts of breakup modes around 5-10kHz. The SEAS Thor crossover attempts to notch what is a tidy 4.8kHz single peak here. Most metal cones are worse than this.

Click the image to open in full size.

If you look at the W18E001 driver frequency response, you can see why it has this:
E0018-08S W18E001

The whole thing is discussed at Klippel, if you are interested:
Vibration analysis

Klippel modelling gets quite close to the more typical SEAS L18RNX/P driver. Bit of a pig to tame that one!
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Last edited by system7; 1st December 2012 at 04:23 PM.
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Old 1st December 2012, 09:48 PM   #34
PALUSE is offline PALUSE  Portugal
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Sorry Steve, but i'm a bit lost with the meaning of the 1st and 2nd graphic.
The idea was to prevent the depression after 10Khz and the peak at 20Khz with the 8,2 Ohms+2uF, even with the original crossover of the MA Silver S6; to tame the top a bit.
Wasn't it?
By the way, which software do you use for loudspeaker simulation?

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Old 1st December 2012, 10:00 PM   #35
system7 is offline system7  United Kingdom
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I'm using Visaton Boxsim. Very nice, very easy!
Downloads

Also substituting the Visaton AL-130 driver which is a typical metal cone:
AL 130 - 8 Ohm

And the soft dome G25FFL. I gotta admit I thought that was a metal dome, but it shouldn't matter much, but I might remodel it with something else...
G 25 FFL - 8 Ohm

A Zobel just reduces treble by 2dB in conjunction with an attenuating resistor on the input to the filter. That's what the diagram shows. Doesn't sound like much, but these sort of differences make a level mismatch stand out. It won't cure the characteristic aluminium tweeter peak at around 27kHz, but will reduce it.
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Last edited by system7; 1st December 2012 at 10:07 PM.
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Old 1st December 2012, 10:16 PM   #36
PALUSE is offline PALUSE  Portugal
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Ok, Steve. So, the high pass notch (8,2Ohms+2uF) only attenuates the tweeter response by 2db or more, after "what" zone?
It will cut a bit the 20Khz peak, but don't correct the 10khz + depression, only deeps it a bit.
After all we dont have MA Silver S6 tweeter model and specs.

Best regards

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Old 1st December 2012, 10:38 PM   #37
system7 is offline system7  United Kingdom
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Don't worry, it's not hard to modify an existing design if you have certain goals in mind. It's enough to know the general principles of filters.

I remodelled it with a metal dome tweeter, and it's not much different. BUT PHASE is now a DELIGHT. This confirms a new principle for me. Use paper tweeters with paper woofers, and metal tweeters with metal woofers for good phase.

Here's the final design. You can use the existing treble filter for now, but I'd recommend the third order. 10uF is OK, but 15uF is now optimum. Beyond a certain point, you have to live with that top treble rise. It's not easy to notch tweeters without taking impedance too low.
Attached Images
File Type: jpg MA-RS6-Network-DSM.JPG (29.5 KB, 43 views)
File Type: jpg MA-RS6-Network-DSM-Phase.JPG (48.7 KB, 39 views)
File Type: jpg MA-RS6_DSM-FResp.JPG (56.9 KB, 31 views)
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Old 1st December 2012, 11:15 PM   #38
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Thanks Steve.
If the MA Silver S6 tweeter is similar to the RS6, the depression after 10Khz is "cured" with a serial ressonant combination at +/- 15Khz. We have to know the hf drive inductance, to calculate serial capacitance.

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Old 3rd December 2012, 01:32 AM   #39
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But as far i could see with Seas tweeters, theres a big chance of the inductor value be 50uH, which would imply a 2,2uF capacitor to create a low Z at 15Khz; but it will devastate the HF response of the system. Behind that, the Zobel would take care of the 20Khz peak, and behind the Zobel the high pass filter take care of the hf band and spl tuning of the HF drive.

What does the 18uF cap, after the highpass stage. Its a bit expensive a 18uF MKP capacitor?!

Best regards

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Old 3rd December 2012, 02:15 AM   #40
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I notice the majority of Seas tweeters have a near 30Khz peak, instead of the near 20Khz.
You refer the 50uH, 6Ohms Z, as a normalize figure for an inch tweeter...
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