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Multi-Way Conventional loudspeakers with crossovers

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Old 11th December 2010, 08:56 PM   #21
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Excuse me, i meant spheres of cause.
Is there still old material of that interesting company ?
I worked with the Dynaudio drivers back then too.
The D21 is exceptional, even today.
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Old 11th December 2010, 09:06 PM   #22
SY is offline SY  United States
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At that time, Dynaudio was still SEN-Labs. I still have a pair of their old paper 21cm woofers (ancestor of the 21W54), 12 ohm nominal impedance, just looking for the right project. I'll see if I can find one of Precedent's old brochures for the MZ Mod II/III speakers, scan it, and send it along.
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Old 11th December 2010, 09:31 PM   #23
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great ! Skaning, one of the founding members founded Audio Technology later.
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Old 12th December 2010, 06:48 AM   #24
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I made more experiments with the ZDL tweeter and Elias is right. Simply hanging the tweeter in "free air" is not the solution. Some damping of reflexions is necessarry for best results and i arived at a good result by damping the back of the tweeter with foam and damping the bucket with poly stuff. That ainīt look pretty but this is just a first attempt.
See the response i get now compared with the measurement without damping.
Attached Images
File Type: jpg ZDL Tweeter with damping.jpg (57.6 KB, 1002 views)
Attached Files
File Type: pdf ZDL Tweeter on Bucket damping plus foam behind.pdf (6.8 KB, 158 views)
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Old 12th December 2010, 09:54 AM   #25
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I also measured distortion. First Harmonic Distortion, second and third. As comparison i used a SEAS 19TFF1. Here the SEAS scores with less third but that does not tell the whole story as you will see in my next post.
Attached Files
File Type: pdf SEAS 19TFF 1 Harmoni Distortion.pdf (5.3 KB, 110 views)
File Type: pdf ZDL Tweeter Harmonic distortion.pdf (5.4 KB, 90 views)
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Old 12th December 2010, 10:49 AM   #26
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First you see that under 2kHz the ZDL tweeter does better the SEAS in third. This is what i found with a lot of tweeters that use Ferrofluid. In the SEAS some compression is going on but it is still well controlled. Now i made some Multitone measurements. Here the diffences come out more clear i think. The ZDL tweeer has more low level hash and should not be used much under 2kHz but the SEAS ( red ) has more high level intermodulation.
What sounds better can only be found out with listening tests. I can not use the SEAS anyway because it has a wide baffle and it does not fit into this particular design.
Attached Files
File Type: pdf ZDL Tweeter green, 19TFF1 red, Multitone.pdf (7.7 KB, 92 views)
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Old 12th December 2010, 10:59 AM   #27
soongsc is offline soongsc  Taiwan
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Quote:
Originally Posted by 6.283 View Post
post 10
Yep. Agree.
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Old 12th December 2010, 09:50 PM   #28
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Ah, I was not aware of that version of the Vifa 3/4" tweeter with the rear chamber! We had tested the previous (no-chamber) version for similar use, but went with another tweeter for that particular application. The one with the chamber looks much more promising. I will certainly be ordering some of the chambered version for my own use.

It's funny, I had just bought some MDM-55 midranges a few months back to test something like the Stoll speaker (the omni woofer being something we have been doing consistantly for more than 30 years already at Ohm, of course). I had not known of Stoll until reading your thread here. In some ways it is quite similar to some Ohm speakers, but, thankfully missing some key design features [which I'd not want to disclose publicly].
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Old 13th December 2010, 05:57 PM   #29
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I had a long discussion with Dominik and this is what he would like to clarify:
There are two way to show sensitivity : at 1W/ 1m and at 2.83V/ 1m. An 8 Ohm speaker whith a sensitivity of 90dB @ 1W/ 1m whould also have a sensitivity of 90dB @ 2.83V/ 1m. The tweeter i am using is a 4 Ohm ( DIN ) design with a DC value of 3.3 Ohm and has a sensitivity of ca. 90dB @ 2.83V/ 1m. Measured as 1W/ 1m the sensitivity whould be 3dB lower so 87dB @ 1W / 1m.
I am using the 2.83V / 1m method.
Second he found it absolutely correct that the sound travels around the driver. He was encuraging me to remeasure the ZDL tweeter against the SEAS on a string hanging from the ceilling . The ZDL tweeter under this conditions should have a very flat response acording to his experience.
Third a ZDL speaker should have no early reflexion the first 17msec that are stronger then -35dB.
Forth, the Q2-b is designed to be listened too very close ( not more then 1m, or as long as your arm stretched out ) in a well damped room so his setup is even more stringent then mine.
Fifth he agrees with Linkwitz that the sound a speaker produces to the sides and even to the back is extremely important for "timbre" especially in the fundamental tone area under 1kHz and that this is not researched well or got too little attention.
I start to feel the burden.
Critofur, i had an Ohm F back then and besides grilling amps ( the big Dynaco worked ) the sound we got was quite psychedelic. I had forgotten that i already had a lot of experience with Omnis 35 years back. Well, the ZDL will not excactly be an omni but i will try to extend the off axis treble as much as i can.
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Old 14th December 2010, 10:15 AM   #30
Elias is offline Elias  Finland
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Hello,

Quote:
Originally Posted by Joachim Gerhard View Post
I went breefly through the link you send me Elias. Interesting interpretation that the sound moves around the tweeter and comes back from behind to interfer. I have not put much thought into that but it inspires me. Many thanks. Was that a conventional tweeter with a rather big frontplate ?
I still do not have a picture of the bigger Midfield Stoll Monitor but there Domink uses a tweeter that as an extended bullet shaped back. I have no idea if that helps to supress the "roundabout effect".
Yes the around diffraction is reality. Wavelets have teached me quite a lot about audio. It's very good visualisation tool.

The tweeter I used with that wavelet graph was Peerless dome with 100mm round front plate.


But I think sphere is a compromise, it tries to minimise front diffraction but it maximises around diffraction. Better to put the element in the end of a long tube so bacwards diffracted sound cannot turn back again.
Click the image to open in full size.

This comes to mind:
Click the image to open in full size.



Quote:
Originally Posted by Joachim Gerhard View Post
Third a ZDL speaker should have no early reflexion the first 17msec that are stronger then -35dB.
That is not going to happen unless the room size is at least 6*6*6m and you're listening at 3m distance from boundaries, also the floor Not very domestic situation.

I think it is better to use very high directivity speakers (e.g. dipole line arrays) in the midrange to avoid the room.


- Elias
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Last edited by Elias; 14th December 2010 at 10:18 AM.
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