i'll be playing with the software, but really i need to understand the electronics involved firts...
i've been on your site, nice one, but would be nicer if you didn't fortce the browser window to resize (this happening to firefox 3 on osx)... 🙂
the Quasar Mk II is a nice one! but the diy page still under construction, and then not what you would call narrow... in such a case is the bass and mid frequencies splitted between the two woofers or are they working just the same? isn't such a width, and the little tunnels behind the drivers an issue? someway all U-frames?
i've been on your site, nice one, but would be nicer if you didn't fortce the browser window to resize (this happening to firefox 3 on osx)... 🙂
the Quasar Mk II is a nice one! but the diy page still under construction, and then not what you would call narrow... in such a case is the bass and mid frequencies splitted between the two woofers or are they working just the same? isn't such a width, and the little tunnels behind the drivers an issue? someway all U-frames?
I think 400Hz is abit too high, just gut feeling and never actually done it.
I crossed mine at 300Hz. I've tried lower like 100Hz but the P13 and baffle is too small at that frequency even when equalised. I think the lower the better because there will be less localization at lower freq.
I use gainclones (LM3875) and never feel the need for better ones. The biggest hurdle in electronics design is the PCB. It's difficult, messy,and hard to correct. I simply use point-to-point connection for gainclones and breadboard for the XO. Just like a jigsaw puzzle 🙂 like this
Click "email" to email 🙂
I crossed mine at 300Hz. I've tried lower like 100Hz but the P13 and baffle is too small at that frequency even when equalised. I think the lower the better because there will be less localization at lower freq.
I use gainclones (LM3875) and never feel the need for better ones. The biggest hurdle in electronics design is the PCB. It's difficult, messy,and hard to correct. I simply use point-to-point connection for gainclones and breadboard for the XO. Just like a jigsaw puzzle 🙂 like this
Click "email" to email 🙂
gainphile really'd like to mail you, but all you made public is your blog, that perhaps is where i saw openbaffles first time 🙂 i think it was the S2 or something...
my username @gmail.com
but honestly its better to ask stuff in the open like creating a new thread because 1) I am no expert and others may help. 2) useful for others.
Don't ever feel a question is "not worthy" people are really great in this forum.
😎
but honestly its better to ask stuff in the open like creating a new thread because 1) I am no expert and others may help. 2) useful for others.
Don't ever feel a question is "not worthy" people are really great in this forum.
😎
Rudolf said:
A point worth noting is that XDir is designed to approximate an infinite baffle; the results are certainly wrong if you apply this to an open baffle. For example look at the position 90 degrees off axis, where open baffle response theoretically drops to zero. To what degree this affects the more on-axis positions is not obvious.
so by now, it seems that a narrower baffle has smoother mid response. one thing that puzzles me is that someone claim the it's all about having bass and mid with dipolar directiviti 2pi and highs only frontfiring and direct... so why is the orion using two tweeters?
the clain coming from Thorsten Loesch here,
http://www.diyaudio.com/forums/showthread.php?s=&threadid=48247&perpage=25&highlight=&pagenumber=1
http://www.diyaudio.com/forums/showthread.php?s=&threadid=48247&perpage=25&highlight=&pagenumber=1
pedroskova said:
In the plane of an open baffle the theoretical response should be a null, the front and back waves cancel. It does not matter if you are looking horizontally or vertically. In reality, it might not be completely zero if the sound radiated from the front of the cone is not equal to the sound radiated from the back of the cone for some reason, but it should be a minimum. The plot above shows a maximum at the baffle plane which is correct for an infinite baffle but not for an OB as stated by martinv. I almost always agree with another "martin".
MJK said:
I don't know about theory, but measuring different OB mtm configurations has shown me results that are consistent with what one would expect with differing CTC spacings...relative to the crossover point. Does OB confuse this? Sure, why not, but it doesn't nullify the basic concept.
Because the cross-over frequency of the tweeters is very low with 1,5 kHz. The back-firing tweeter fills in the region above 1,5 kHz. http://www.linkwitzlab.com/orion++.htm It would probably not be necessary to run it above 3 kHz or so, but once it is there, it does not hurt either.human.bin said:
human.bin said:
Thorstens prejudice for fullrange plus supertweeter configurations in OB is well known. Arguments like "Dipole Speakers using dynamic cone drivers tend to remain dipole only to around 300-500Hz" are set at least one octave too low. And his demand "The Transducer(s) should have a even energy balance in the 100Hz - 10kHz range" can only be achieved with backward radiation at the tweeter level.
pacificblue said:
Have you got any insights why back-firing above 3 kHz would (not) be necessary? I´m still looking for any research regarding the frequeny range where direct and power response must be correlated.
indeed in the same thread: IT IS necessary... but room reflections would destroy or at least make uncontrolable such high frequency spacial cues. that is this response would be useful when you plan to live outside, or listen painfully nearfiled. he also suggest that you can by the way 'make up' your room such a way (a hard costly, low WAF one) so that you come up with the same farfield response you are having without back firing above modal range.
if i got it right.
if i got it right.
I do not remember, where I read it, could be here, on the Linkwitz site or some place else.Rudolf said:
I remember two reasons that were given.
One was that the directivity of most tweeters becomes narrow above 3-5 kHz. Any sound radiated from the speaker would be reflected at near right angles between speaker baffle and wall to and fro until all energy was used up, thus never leaving the region between speaker and wall.
The second was that the energy a tweeter radiates is so low, after a few reflection from walls, furniture, etc. virtually nothing would be left to reach the listener.
In both cases the tweeter would not contribute anything to the perceived sound.
I have experimented with/without rear tweeters for quite sometimes. The easiest confirmation is to try it, put on a switch 🙂 The brain cannot judge absolute value, but very good at detecting sudden differences.
Without rear tweeters definitely something is missing ("hollow", "empty space" etc.) in overall sound spectrum -- although FR measures flat. This leads to conclusion that FR is only one small part of the equation of obtaining good illusions. The brain expects sound reflections to be "complete" or "uniform" to be trustworthy.
Without rear tweeters definitely something is missing ("hollow", "empty space" etc.) in overall sound spectrum -- although FR measures flat. This leads to conclusion that FR is only one small part of the equation of obtaining good illusions. The brain expects sound reflections to be "complete" or "uniform" to be trustworthy.
Siegfried Linkwitz also finds this, and so do I (using the Neo3 PDR). The reason for this seems to be the Precendence Effect. The human hearing has the ability to isolate the first wavefront out of all the reflections. The reflections are not heard as a wavefront from a separate source but are perceptually masked (although they do help for source localization). You may already know this theory.
It seems to me (and I believe Linkwitz agrees) that reflections with a very different spectrum (completely missing high frequencies) are not masked but more or less perceived as a different wavefront.
It seems to me (and I believe Linkwitz agrees) that reflections with a very different spectrum (completely missing high frequencies) are not masked but more or less perceived as a different wavefront.
Any decent 1" dome tweeter is less than 5 dB off at 90° and 5 kHz. A 19 mm dome would be off about 5 dB at 10 kHz.pacificblue said:
The following measurement from Music and Design for a dipole with a 1" dome tweeter front and rear shows that
1. at least for the Seas 27TDFC increasing directivity doesn´t start below 5 kHz
2. figure 8 radiation works well above 10 kHz
So we can discuss if a dipolar radiation patterns up to 10 Khz is of any use. But we can NOT discuss, if a dipolar radiation pattern above 3-5 kHz exists. The last posters seem to vote for some benefit.
Rudolf
this one definitely is an answer.
one the same kind of what you are suggesting, on deccaware, valve sound is said to be unfaithful, but then the harmonics the valve invent is something the brain is expecting in the sound texture to fell it true.
one the same kind of what you are suggesting, on deccaware, valve sound is said to be unfaithful, but then the harmonics the valve invent is something the brain is expecting in the sound texture to fell it true.
5 dB less means it radiates ~32 % of the power it radiates on-axis. And the question was about a rear-firing tweeter, i. e. at 180 °. Figure 8 from your link looks as if the rear tweeter was already 10 dB down between 7 and 8 kHz. And that is inspite of a frequency response rise on-axis.Rudolf said:
In the link from post #71 Dr. Linkwitz describes, how he came to adding the rear-firing tweeter to the Orion. It was because he found the difference from the Pluto to the Orion surprisingly small and noticed that the Orion without rear-firing tweeter was a dipole up to 1,5 kHz, while the Pluto covers up to 3 kHz with uniform polar response.
We cannot discuss it, because I don't know, if it is of any use. I assume that it may not be necessary to run a rear-firing tweeter to its upper frequency limit. Maybe it is good to run it until 3 kHz, maybe until 10 kHz, or maybe it should run as high as it can. You will have to make your own tests, if you are interested in knowing the truth.Rudolf said:
Don't be surprised, if it turns out to be a question of the listening room layout and of personal taste. Anyhow I would not go to the lengths of using a low-pass on a rear-firing tweeter. I would wonder whether it makes sense to add a rear-firing tweeter, if the speaker was already dipole up to 3-4 kHz. But then there is always gainphile's proposal from post #75 to check it out.
Rudolf said:
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