Testing of Dipoles

Robh3606

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Aug 24, 2010
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Hello Sean

A question came up after a review of one of the articles in your blog. Specifically the study about Generation Y and the result of speaker ratings in the study. The questions arrise from using the same placement position in the room testing for a Dipole vs the other speakers in the test. A dipole has a different radiation characteristics than the other speakers in the group. Would this in anyway bias the test results as a dipoles location for best response may differ from a monopole speaker? Was the fact that one speaker was a dipole compensated for by say room treatments during the testing?

Thanks Rob:)
 

Robh3606

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I am sorry I didn't read the intro all the way through. My enthusiasm got the best of me, this is great I can ask him a question!

Mods please delete

Rob:)
 

Jose Almagro

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Dec 10, 2010
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Hi Rob. I'm not Sean but maybe I can help you.

Of course dipoles are different! All of the energy is sent frontside and backwards. Floor, side walls and ceiling first order reflections are almost nothing and the reflections coming from the front wall can be very strong. I don't like rules but my opinion is that all that energy has to be "broken into pieces", I mean it shouldn't be absorbed or it would sound dark. The option of using diffusers could be better it's not bright enough. Create a few diffractions or just using surfaces to guide specular reflections out of the listening point should work better.

Anyway, I have dipolar speakers and use a column and the furniture to achieve very what I wanted: Direct sound is about 23 dB over every reflection and the reverberation (slope) is very high and diffuse.
Hope this can help.
 

tonmeister2008

WBF Technical Expert
Jun 20, 2010
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Westlake Village,CA
Hello Sean

A question came up after a review of one of the articles in your blog. Specifically the study about Generation Y and the result of speaker ratings in the study. The questions arrise from using the same placement position in the room testing for a Dipole vs the other speakers in the test. A dipole has a different radiation characteristics than the other speakers in the group. Would this in anyway bias the test results as a dipoles location for best response may differ from a monopole speaker? Was the fact that one speaker was a dipole compensated for by say room treatments during the testing?

Thanks Rob:)

Hi Rob,
Thanks for your question. Nearly all the dipoles we tested have a direct radiator subwoofer to reproduce frequencies below ~ 100 Hz. So below 100 Hz, the loudspeaker is being treated the same as the others, and will excite the same room modes as the others since we use positional substitution of the loudspeakers via our automated speaker mover.

Above 100 Hz, the speaker does have a dipole characteristic. According to the manufacturer's instructions they recommend the speaker be placed far away from the side walls, which is what we are doing in our tests.
 

Jose Almagro

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Well, when I spoke about dipoles I was thnking about full dipoles. I don't like the hybrid solution because of it's great difference in dispersion between the drivers. That causes the bass balance to be very dependent on the distance.

Since last week I'm owner of a pair of Apogee Stages and I like very much it's sound. My next DIY project is a pair of Class A amplifiers and then I'll probably try to make a pair of cardioid subwoofers (that could be multipatern).
 

muralman1

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Jul 7, 2010
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I have even a more difficult speaker to test. I wonder how it would be done. The vertical tweeter ribbons are bipoles. The mid ribbon and bass panel are dipoles.

Not only do dipoles have to be placed away from the side walls, but also the rear wall. Apogees are suppose to be 3-4' away from the back wall. The reverberation confuses the heck out of electronic room correction devices, like the TacT preamp.
 

Jose Almagro

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My English isn't very good and that "heck out" is confusing me as much as the TacT :)

My point of view is that high reverberation is a bless for my Apogees. Please remember reverb is only a slope so I need a big step in ETC to make it sound good.


Microphone/ears are placed 2,9 m (9.5 ft) away from each loudspeaker.
 

Jose Almagro

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Dec 10, 2010
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Jose, I'm surprised that you so much toe-in on the Stages. Also, being so close to the side walls is usually a no-no with Apogees.
The best way to place Ap's is to use the Cardas site calculator, it works like a champ for me.
Use the dipole calc, it's been able to get the best sound out my Duettas.
Hi wineslob, I'm living here for one month, I used to have a small room with a pair of small monitors (the ones on the shelf) and a fitted sub. When I arrived here I thought it was the time to have something bigger and I started a serious DIY design using JBL 2226H with a diffuser to improve dispersion and a Beyma TPL-150 working as dipole (improves 2nd order HD dramaticly).
http://www.jblpro.com/pages/pub/components/2226.pdf
http://profesional.beyma.com/ingles/pdf/TPL150.pdf
Those are very nive drivers but Apogees have something and I saw them cheap 400 Km from here so I took them here...

After such a long travel and carrying them home I placed them with less toe-in and I had the visit of a very good sound engineer who owned Apogees twice, while I was at the phone I saw him changing their position as you saw and when I sat down I agreed the placement sounded well. A few days later I put the microphone on the listening place and I checked that M*F*has an oscilloscope inside his ears.

The Cardas calculator is very simple and may be a first step but my opinion is that's not very good for most of the rooms.

Jose, for "confuses the heck out of" substitute "greatly confuses". For TacT, see here: http://www.whatsbestforum.com/forumdisplay.php?47-TacT
Thanks, the TacT seems to be a nice toy but expensive for me and as an acoustician I have fun dealing with acoustic problems.
 

Robh3606

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Aug 24, 2010
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Hello Sean

Thanks for answering my question

Rob:)
 

Theresa

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Mar 7, 2011
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Well, when I spoke about dipoles I was thnking about full dipoles. I don't like the hybrid solution because of it's great difference in dispersion between the drivers. That causes the bass balance to be very dependent on the distance.

Since last week I'm owner of a pair of Apogee Stages and I like very much it's sound. My next DIY project is a pair of Class A amplifiers and then I'll probably try to make a pair of cardioid subwoofers (that could be multipatern).

I think it is some other charecteristic of "hybrid" solutions that you don't like as signals as they go below 100Hz become increasingly non-directional. A bass signal has too long a wavelength to be directional. I've never lived with dipoles but a friend in the early '90s had Maggies with a sub and it was wonderful. I do think occasionally but like my "box" speakers too much to bother. Someday perhaps.
 

microstrip

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May 30, 2010
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Above 100 Hz, the speaker does have a dipole characteristic. According to the manufacturer's instructions they recommend the speaker be placed far away from the side walls, which is what we are doing in our tests.

Although most speakers sound better away from walls, some full frequency dipoles can be used with success near the side walls, specially if their angular dispersion is narrow and well controlled. I have heard Quad ESL63's playing near the side walls sounding much better than expected.

If you look at pictures of systems using dipoles in the audio forums, you will find that many Soundlab and Magneplanar users place them rather close to the walls.

As usual, every speaker is a different case.
 

DonH50

Member Sponsor & WBF Technical Expert
Jun 22, 2010
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Note that, while my Maggies are fairly close to walls, those walls are well-damped.

microstrip -- I would have tweaked your last statement just a hair: "As usual, every speaker, room, and listener is a different case."
 

A.wayne

New Member
Jan 14, 2011
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Front Row Center
Hello,

I dont have apps, but i toe my ribbons in the same in my room, the biggest issue i see is the roof height vs listening distance, the apps would be much more "powerful" sounding in a room with a much lower or avg ceiling height ..

Regards,
 

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