15" woofer at 1KHz?

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Rudolf

“Even when listening on axis, more than 50 % of what you hear is indirect sound”
Hi Rudolf
50%  :o
I know off-axis response is important, but didn’t feel it could be that much ~ without ever seeing a figure.
Where did you see or calculate that figure?
Would it be a little room dependent, ie with closer side walls, that figure would it be higher?

With a speaker in OB half the sound energy will go to the rear side - it has to. From the energy radiated to the front hemisphere your ears will only catch a fraction directly. Most will reach your ears only after some reflection from the room boundaries. The direct sound will dominate your hearing impression, but the first reflections - reaching your ear within 30 ms - get integrated into your listening experience too because of the precedence effect. Floyd Toole describes it in depth in his book 'Sound Reproduction'.
 
If the frequency response of the indirect/reflected energy in the room doesn't have enough resemblance with the direct sound, your brain can't integrate it with the direct sound - probably you might hear additional phantom sources.

Your primary aim is still to get the direct sound right. But you want to make sure, that the indirect sound energy in the room does not look (and sound) too different.

rick57

Re: 15" woofer at 1KHz?
« Reply #21 on: 23 Jun 2010, 04:02 am »
(I knew that half an OB's sound energy goes to the rear).
But not that - of the energy radiated to the front, our ears only catch a *fraction directly.
 
Yet  *direct sound dominates our hearing impression . .

So is it the reflections reaching our ears within 30 ms,  integrated (into our listening) added to the direct fraction, that dominates our hearing impression?

Cheers

Rudolf

Re: 15" woofer at 1KHz?
« Reply #22 on: 23 Jun 2010, 08:44 am »
So is it the reflections reaching our ears within 30 ms,  integrated (into our listening) added to the direct fraction, that dominates our hearing impression?

Sort of, yes. It can't be explained in two sentences :(  Google for 'Precedence' and 'Haas' effect and for 'Apparent Source Width' ASW. In my opinion the room is a much more important factor in loudspeaker design than commonly believed. And I am not the first one who recommends Toole's 'Sound reproduction' as essential reading. :wink:

rick57

reflections and hearing impressions
« Reply #23 on: 23 Jun 2010, 10:49 am »
I recently got Toole's book, and will try to find time to read it (500 pp)

I appreciate that room interaction is very important, and overlooked by many. that's why I'm going OB

I didnt know the extent to which off axis was *so critical -

In fact I thought that "beaming" of a 15” say 500 – 1500 Hz, means less room interaction, so would be a *Plus . . ?

Rudolf

Re: reflections and hearing impressions
« Reply #24 on: 23 Jun 2010, 02:18 pm »
I recently got Toole's book, and will try to find time to read it (500 pp)

Reflections are chapter 6-10 mainly - out of 22  :roll:

Quote
I didnt know the extent to which off axis was *so critical -

I wouldn't call it 'so critical', but it should not be ignored either.

Quote
In fact I thought that "beaming" of a 15” say 500 – 1500 Hz, means less room interaction, so would be a *Plus . . ?

For most people "beaming" would be a changing directivity - increasing from 500 Hz upward for a bare 15” driver. What you really want is constant directivity. That's what a 15” dipole would deliver up to ~ 500 Hz.

rick57

constant directivity
« Reply #25 on: 23 Jun 2010, 03:09 pm »
Yes! I agree (I'd forgotten constant directivity)  :oops:

"That's what a 15” dipole would deliver up to ~ 500 Hz"

Is there a reference and/ or formula for this?

Up to what Hz, would we get constant directivity from
 - a 8" dipole
 - a 6.5" dipole

Thanks again

Rudolf

Re: constant directivity
« Reply #26 on: 23 Jun 2010, 04:44 pm »
"That's what a 15” dipole would deliver up to ~ 500 Hz"
Is there a reference and/ or formula for this?

Do a simulation in Edge under 0°, 30° and 45°. That will show you what happens off axis.

Quote
Up to what Hz, would we get constant directivity from
 - a 8" dipole
 - a 6.5" dipole

Dipole CD is a function of baffle size and driver diameter. Again - do some simulations in Edge. They are really helpful to get a better understanding of what is happening.

rick57

Re: 15" woofer at 1KHz?
« Reply #27 on: 23 Jun 2010, 11:01 pm »
When looking at results in the Edge, what constitutes CD – what dB gap between 0, and 30 and 45 degrees?

Thanks again 

Rudolf

Re: 15" woofer at 1KHz?
« Reply #28 on: 24 Jun 2010, 11:10 am »
When looking at results in the Edge, what constitutes CD – what dB gap between 0, and 30 and 45 degrees?

"Constant" is about dB gap width staying constant - not about absolute gap width values. In the diagram you see constant directivity up to 500 Hz. If you are more exacting, you would choose 300 Hz as the upper limit:



Above 500 Hz the driver starts beaming - the dB gap between angles becomes larger with frequency.

There are different sorts of constant directivity which are defined by the directivity index. Omni speakers would have a directivity index of 0 dB and dipoles have a directivity index of 4.77 dB.

rick57

Constant directivity
« Reply #29 on: 24 Jun 2010, 11:18 am »
Thanks again, Rudolf

What are the prospects currently, of your site being translated into English?

Rudolf

Re: Constant directivity
« Reply #30 on: 25 Jun 2010, 04:52 pm »
What are the prospects currently, of your site being translated into English?

I have changed my "business model", moving from HTML to a series of PDFs. First PDF is a 14 page treatise on OB response patterns. Today I finished the translation of page 7. Hopefully it will be online by the mid of next week.

Soccer world championship tends to get in the way. If we win against Britain, there are more games to watch. If we loose, I refuse to speak/write English for the next few days :wink:  :green:

ttan98

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Re: Constant directivity
« Reply #31 on: 25 Jun 2010, 10:04 pm »
I have changed my "business model", moving from HTML to a series of PDFs. First PDF is a 14 page treatise on OB response patterns. Today I finished the translation of page 7. Hopefully it will be online by the mid of next week.

Soccer world championship tends to get in the way. If we win against Britain, there are more games to watch. If we loose, I refuse to speak/write English for the next few days :wink:  :green:

Based on performance over the last week I believe Germany should win.

rick57

Re: 15" woofer at 1KHz?
« Reply #32 on: 27 Jun 2010, 03:06 am »
I have the odd country I like to see lose, and the UK is one of them (old colonial spirit?).

(Even though you beat us 4-0) Germany, may the force be with you!  :thumb:

And if the Brits were to pull it off, remember that that most of your English speaking readers are Americans  :wink:

Rick (an Aussie) 

ttan98

  • Full Member
  • Posts: 509
Re: 15" woofer at 1KHz?
« Reply #33 on: 27 Jun 2010, 06:52 am »
Rudolf

Is it possible that you put your paper that is written in German text through an automatic translator into English(I understand the auto translator is not perfect in fact far from perfect)? After that you correct the content of the translated text to make it intelligible and/or as close to the German text. Since you are the author as well wouldn't  it be faster this way. BTW I have no experience in translating(but I have done some translating using specialized s/w from Japanese to English) this is just my guess.

scorpion

Re: 15" woofer at 1KHz?
« Reply #34 on: 30 Jun 2010, 09:05 pm »
Rudolf,

Take your time and transalte to your satisfaction. It is good that people like you invest time to write clarifying papers dealing with fundamental OB issues. Our understanding is much improved by this kind of efforts. And the knowledge is nowhere else to be found. So we all benefit.

However your AJHorn paper inspired me to see what Dave McBeans 'Hornresp' program could be used for. In fact I think you could do the same simulations with that program. If I understand right it would be possible to do H-, U-, Ripole and (with reservations) flat baffle simulations in Hornresp with good results. See here Hornresp input parameters, schematic diagram and SPL-simu results and a comparison with Martin's model result for his H-baffle with Eminence Alpha15:







at last MJK's model:



There are mainly differences in level which can depend on different setups for the simulations but I have tried to make them as alike as possible. The thing with Hornresp, you have to go for the combined response in the Tool menu when you are in the SPL-window and input the path difference to get the right answer.

Now for even more OT. We will see Germany and Brazil in the final for this World Cup. It would of course have been different if England had kept their womenazing Swedish coach, remember Munich. But my barber is ever so proud of coming from the same small Kurdistan town as Oezil's parents. Him playing for Turkey !!! HUUUH !!!  :evil: In the end he might be chosen the best player this time. And Klose makes all the difference.

/Erling

rick57

Re: 15" woofer at 1KHz?
« Reply #35 on: 30 Jun 2010, 11:08 pm »
Hi Erling

Have you contacted Dave McBean with your idea? I wonder how it compares with JohnK’s ABC Dipole?

Germany v Brazil. The emotion! If it happens, Best of luck  :thumb:

scorpion

Re: 15" woofer at 1KHz?
« Reply #36 on: 1 Jul 2010, 12:14 am »
Hi  Rick,

No I just put up the simulations so Dave Mc Bean don't know anything, if he didn't read the post. It is a byproduct of that clever program just as Rudolf has used AJ Horn for the same purpose. But it is nice that the simulationprograms do produce very similar results. I suppose that will strengthen confidence in them. I have not used ABC Dipole so I cannot tell.

OT, Regarding the World Cup I am Swedish so I can be a bit neutral. But Sweden like Germany have had a lot of immigration from Kurdistan. Best teams so far are Germany and Brazil and this time Germany can hit from an underdog position.  :)

/Erling

Rudolf

Re: 15" woofer at 1KHz?
« Reply #37 on: 1 Jul 2010, 12:13 pm »
Hi Rick,
did you look into your audiocircle messages box lately? I need an email adress of yours to send you an attachment.

Hi Erling,
I never looked into hornresp, but now I certainly have to. Your comparison looks really good. Now I need to get aquainted to the program to understand what you did.

WRT to the translation, I have almost finished the pre-translation and some native speaker probably will bring it into a readable shape. In addition he might look whether everything can be understood by someone with a basic knowledge of dipoles.

Automatic translation does not work well in my case since my story is not told "narrative", but simply as an explanation around pictures and diagrams.

Rudolf

Telstar

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Re: Constant directivity
« Reply #38 on: 2 Jul 2010, 02:44 pm »
I have changed my "business model", moving from HTML to a series of PDFs. First PDF is a 14 page treatise on OB response patterns. Today I finished the translation of page 7. Hopefully it will be online by the mid of next week.

Nice, looking forward to it.
PDF are best for printing, which i always do for worthwile stuff.
And i wish Germany all the best in this championship - it was my bet from the beginning.

Ah, can you explain how to make the angled response in Edge? Maybe there's a new version out?

Cheers,
Guido

Rudolf

Re: Constant directivity
« Reply #39 on: 2 Jul 2010, 10:44 pm »
Ah, can you explain how to make the angled response in Edge? Maybe there's a new version out?

Hi Guido,
no new version of Edge. It is just triangulation. If you have a certain "mic distance" and move the mic sideways from the speaker center, you can emulate any angle from -90° to +90°. 

I have done a chart with the angles most often used:



Thanks for the good luck wishes. Statistics dictate that a team from South America has to win 2010. Since Brasil is out, it has to be Argentina. You don't see Paraguay or Uruguay as the champion, don't you? So Germany can't win the next game ...  :wink: