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6.283

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Joined 2008
2pi-online.de
Hi Joachim,

obviously we have some very similar ideas how to treat the on-axis vs. off-axis behavior of "non-standard" speakers to make them sound "right". So shutting up now and looking forward to LA vol. 5.
I wish I could be done with my dipole before then so I could compare notes. But I am not sure this is going to happen due to some stupid road blocks.
 
PRTG

PRTG

Member
Joined 2005
Joachim Gerhard said:
gannaji, i will post a photo of my current baffles and then we can talk.
PRTG, i will publish some more work on the diffuse EQ in Linear Audio 5 so i can not disclose all the details right now. What i found with dipoles is that the diffuse sound they add has usually too little presence, so in my G-Pole principle i BOOST the presence range. I found that it is not super critical to get the exact Zwicker curve. A simple soft dome with enough sensitivity does the trick just fine with a ca. 2uF cap. I will post what tweeter i use. Also is important to destroy the impulse response to the back while keeping the diffuse field FRD. That can be done with mechanical delay, simply mounting the tweeter some 10cm back and playing around with absolute phase on that tweeter.
Click to expand...

Ok, I got it. We're on the same boats or close then :)

I have tried coupling symmetrical waveguided dipole HF units with symmetrical bipole bass pseudo-horn aka Voigt pipe (W54cm H110cm D30cm, sloped front baffle, half-folded horn mouth opening towards the floor). I did very simple in-room directivity measurements of the tweeters to see what happens if tweeter polarity is inverted or not. Turned out it does differ: in dipole configuration on frequencies under 8kHz dispersion goes increasingly lateral while in dipole (inverted) it keeps near perfect figure eight all the way down. (unbaffled dome HF units with 16cm wavequides mounted back to back). Here is more info if you're interested.

I got right amount of "forwardness" or "presence" by just attenuating rear tweeter by a couple of decibels with L-pad. After that I found the whole speaker having nice balance between direct and diffuse sound in an extremely small room. The jazz singers felt like being in the same room just in front of speakers and enveloped with feeling of much larger space than the room at the same time.

After I've read in your thread I'm just thinking if rearrangement of rear tweeter can add even more diffusivity to rear beam, then I'd like to try it just to compare with my current setup.
 
Joachim Gerhard

Joachim Gerhard

Member
Joined 2009
suesskindaudio.de
I have experimented with waveguides too and got very good results. The stronger amount of direct sound they produce makes the diffuse field tuning less critical. i build an open baffle with a 20cm wide range and a 25cm waveguide on top. I can not remember the crossover frequency but it was quite low, around 1.8kHz. Putting the diffuse field tweeter in the back made much less of an effect then in a wide range dipole.
 
Joachim Gerhard

Joachim Gerhard

Member
Joined 2009
suesskindaudio.de
That is this system.
 

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PRTG

PRTG

Member
Joined 2005
Joachim Gerhard said:
That is this system.
Click to expand...

Looks like Dayton 8-incher. I also tried them, but unfortunately found to be too honky to be tasteful. I see you did the the foam treatment probably for the same reason :)

In my symmetrical waveguide setup I used two Monacor WG-300. Somehow HOM coloration isn't very pronounced with them, perhaps due relative shallowness of the waveguide. Measured dispersion pattern turned out to be quite smooth and therefore dipole sounded very pleasant. Got even better results when removed original DT-300 tweeter faceplate and mounted WG-300 directly on it through thin self-made adaptor. This eliminated physical unsmoothness due gap where tweeter's faceplate normally meets mouth of waveguide. After that measurements did show that formerly present unevenness at 8kHz was fully corrected.

While WG-300 is not universal to fit other domes, still adaptors can be made also for this purpose. Vifa/Peerless XT-series were recommended as they have patented phase plug, still I haven't tried this combination yet, and, as I said will be aiming for more sensitivity anyway.

Ok, I'll definitely keep an eye on this thread, thanks for your great commitment so far!
 
Joachim Gerhard

Joachim Gerhard

Member
Joined 2009
suesskindaudio.de
In this system i use the Dayton 8" waveguide with Selenium 220TI compression driver.
All symmetric, round waveguides have HOM and with the damping the sound is super smooth. No honk at all. The mid-woofer is specially made for me by SEAS. It is based on the Prestige wide band with Reed cone but does not have a wizzer and other changes.
This is the lowest cost speaker that i would call High End. It served me so well that i had it in the system for over 6 month. Now i am back to the MPL slim with Enviee and Mundorf AMT.
 
Joachim Gerhard

Joachim Gerhard

Member
Joined 2009
suesskindaudio.de
It is just a refinement of post230. The SEAS mid bass now has a smaller magnet for a little bit higher Qts and i stuffed the waveguide with natural wool. I also added a separator in form of a half moon. That steers some more treble to the inside where i listen like a mirror reflexes light. The treble is now better resolved and not so dull any more. I think i overdid the damping of the tweeter a little with the foam-
 

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