Planar Speaker Asylum

Welcome! Need support, you got it. Or share your ideas and experiences.

Return to Planar Speaker Asylum

Message Sort: Post Order or Asylum Reverse Threaded

Midrange Attenuator on 3.7is

108.245.106.138
Posted on January 25, 2016 at 19:46:21
TitaniumTroy
Audiophile

Posts: 626
Location: Mishawaka, Indiana
Joined: October 14, 2006
 Tonight I saw a some pics on Audiogon of 3.7is in MI, and noticed the they have a midrange attenuator, any opinions from the forum gurus on this?

Also I seem to remember some forum members saying the ribbon tweeter crossover is now set higher than my 3.6's. What are the pros/cons of doing this, thanks.

Troy

 

Hide full thread outline!
    ...
RE: Midrange Attenuator on 3.7is, posted on January 26, 2016 at 12:30:08
DrChaos
Audiophile

Posts: 2063
Location: San Diego
Joined: July 13, 2009
 I think the reasons are the same.

The midrange on the 3.7 takes up more of the sound range than the 3.6, and therefore may need to be attenuated for psychoacoustic reasons. (Perceived ideal spectral balance is NOT flat, it is sloping down)

Pros are better integration with tweeter I guess.

Cons are less tweeter magic. Perhaps the QR foil on the 3.7 midrange makes up for it vs the wire on the 3.6 midrange.

 

RE: Pros & Cons ..., posted on January 26, 2016 at 17:07:32
andyr
Manufacturer

Posts: 12550
Location: Melbourne
Joined: September 2, 2000
 AIUI, ideally there should not be a XO inside the vital 300 - 3,000Hz frequency range (because of the resulting phasing issue - even a 1st order XO has a 90 deg phase difference between the upper-frequency output and the lower-frequency output).

So they moved the mid-ribbon XO frequency up, for the 3.7, to get away from this issue.


Andy

 

RE: Pros & Cons ..., posted on January 27, 2016 at 04:11:28
Roger Gustavsson
Audiophile

Posts: 2058
Location: Huskvarna
Joined: February 12, 2010
 There is more than just the crossover changes. There are fewer magnets in the bass and the midrange. The edge of the bass/mid driver is not driven. It is not a simple first order series crossover.

The bass is rolled off by about 12 dB/octave above 500 Hz. The midrange operates at about 350-5000 Hz, the tweeter above 3600 Hz.

Figures for the 3.6: bass rolled off by 24 dB/octave above circa 280 Hz. Mid is rolled off by 6 dB/octave below 220 Hz and by 18 dB/octave above 1200 Hz. Tweeter is rolled off by 12 dB/octave below 2500 Hz.

All these are the "electric" roll offs. Acoustic roll off may be different.

The 3.6 stresses the ribbon tweeter a bit. The 3.7/3.7i let the mid operate at higher frequences. This is similar to what it is in the Tympani IV/IVa.

Maybe this is the reason to the better integration of the mid/tweeter? Sure, the mids of the 3.7/3.7i is not very low mass and it sits on the same piece of Mylar as the bass.

Electrical or acoustic phase does not worry me. If the frequency response is right, that is good enough.

 

RE: Pros & Cons ..., posted on January 27, 2016 at 11:41:26
Swamis Cat
Audiophile

Posts: 272
Location: Illinois
Joined: September 7, 2013
 Does anyone use a midrange resistor on their 3.7?

I tried it once when I first got the speakers but don't remember it making much difference with 1 ohm. Has anyone found it does improve things?

What value resistor did you use?

What were the benefits or trade offs?

Now where did I put that bag of resistors....?

 

RE: Pros & Cons ..., posted on January 28, 2016 at 08:10:07
Swamis Cat
Audiophile

Posts: 272
Location: Illinois
Joined: September 7, 2013
 Here is what I found,,,,

With the speakers aimed exactly directly at me (bass side is exactly same distance from my nose as the tweeter side), adding the 1 ohm resistor to the treble reduced loudness by 1.5 db at the listening position when set at 70db starting at 4 kHz. No effect below that.

Inserting the mid 1 ohm resistor lowered the the upper Mids from 800 to 2.5 kHz by about 1 to 1.5 db. Again, it had zero impact above that number or below.

Thus inserting both resistors reduced the volume by about one to 1.5 db at fixed listening position above 800 hz. The only frequency not affected by either was exactly at 3.2 kHz.

Obviously the exact details will differ based upon measuring position, speaker position and toe in (small changes in toe in can dwarf these effects) but for what it is worth...

In terms of sound, adding both resistors to the 3.7i reduces glare and makes the speaker sound much more smooth, liquid and relaxed. The question is whether it makes it TOO smooth. With the Emotiva XPA-1 it seems a good addition, though not uniformly so. Time will tell. I also hope to try it next week with a PS Audio BHK 250.

I have used the treble resistor for a long time, but will now go for a while using both and see how it grows on me.

 

Page processed in 0.033 seconds.

[ Top Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2024, Audio Asylum, all rights reserved ]
[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]