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Old 12th May 2011, 11:19 AM   #11
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Quote:
Originally Posted by bjorno View Post
Hi,

I think, you are...Are you designing a passive or active compensation?

b
Touche, yes, this would be doable at line level and I do intend to play with active. I have a bunch of drivers, tweeters and boxes, none properly optomised for each other, I am trying to identify which things will complement each other best if optimised properly... but that is beside the scope of my inquest, I'm simply trying to understand the very basic fundementals (lacking any calculus schooling, we only had algebra and trigonomentry and that was decades ago), to help me make informed choices and starting points for experiments.
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Old 12th May 2011, 11:45 AM   #12
bjorno is offline bjorno  Sweden
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Originally Posted by digits View Post
I'm gonna make this a seperate post as I'm not sure to what extent these are linked yet. If the driver is 226mm wide (outer edge of frame) and you had a microscopicaly small tweeter (for the sake of the experiment), placed right on this border. The shortest wavelenght that could span from center to center would be just over 1500Hz. Does this mean that to approximate a point source,...
No, The system would not approximate a point source but Lambda/4 would, ie at ~380 Hz.

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..the highest frequency the woofer should cross at( Or possibly the correct frequency) would have to be under 1500, (under becasue as the tweeter size grows the frequency would drop a little). Which would correspond with the corner frequency of a baffle width of 22.9cm. (lol, thats less than the width of the driver....)
I really don't not what you are after...To use the 'Edge correctly you need to specify the baffle size, driver sizes involved and the supposed listening height above the floor. Prior to this I suggest you use the Xdir program to make a decision on where you want to put your summed FR loobes, i.e. by choosing the acoustic XO, whether a odd or even order is to be picked...

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we only had algebra and trigonomentry and that was decades ago), to help me make informed choices and starting points for experiments.
You don't need more...as this subject is very basic..

b

Last edited by bjorno; 12th May 2011 at 11:50 AM. Reason: missed a later posting
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Old 12th May 2011, 12:27 PM   #13
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Originally Posted by rabbitz View Post
It's about baffle width and the space where the speaker is working. To calculate the F3 at the baffle step use 115/baffle width in metres.

I'll give you a visual example of baffle step using ants.

With a speaker against the wall (2PI space), picture the baffle covered in ants. As some ants escape to the back of the speaker they can't hide so you see them all (no baffle step reduction).

With a speaker in free space (4PI space), the escaped ants now can hide behind the box so you can't see them, only the remainder. That's the SPL reduction from baffle step.
Good article. BSC equals bass boost equalization to speakers with small baffles placed away from a wall that would otherwise reinforce bass acoustically. The article points out the advantages of providing this boost by active equalization before the power amplifier, the disadvantages of providing it passively with an inductor after the power amplifier, and why that is the way it is commonly done anyway because of the nuttiness of the way audiophiles view the world. It's certainly one way to increase cost.
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Old 12th May 2011, 01:42 PM   #14
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Soundminded ,I don't follow you . Are you suggesting to put a 'black box' before the amplifier to give the correction to a precise loudspeaker ?
I remember I saw those things (Myst ) in the digital world many years ago ,and you did have to put on a EEPROM the correction curve for that kind of loudspeaker system . I don't see any around ,now .
A simple meter of copper ( or more )is simple ,elegant ,unique !!
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Old 12th May 2011, 02:07 PM   #15
AllenB is offline AllenB  Australia
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Originally Posted by digits View Post
In a multi-way system, is there any benefit in designing a a box with dimensions that creates the step at frequencies that are the same as the crossover network's switching points.
No, there is no benefit...regardless, even, of how many drivers and where their crossover points are. There will still be a transition from full space radiation to half space radiation at the baffle imposed step frequency.
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Old 12th May 2011, 03:50 PM   #16
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Originally Posted by picowallspeaker View Post
Soundminded ,I don't follow you . Are you suggesting to put a 'black box' before the amplifier to give the correction to a precise loudspeaker ?
I remember I saw those things (Myst ) in the digital world many years ago ,and you did have to put on a EEPROM the correction curve for that kind of loudspeaker system . I don't see any around ,now .
A simple meter of copper ( or more )is simple ,elegant ,unique !!
The referenced article makes it clear. The FR is designed depending on where the speaker is anticipated to be placed compared to adjacent walls and other reflecting surfaces including the driver's own baffleboard. With no acoustic reinforcement from a narrow front baffleboard or nearby walls the bass output relative to the rest of the spectrum is reduced especially when the speaker is pulled away from the back wall. This will make the speaker sound bass shy unless bass output is increased in one of two ways. Either boost the bass input signal to the power amplifier stage or cut down on the output above the bass after the power amplifier in the crossover network with power wasting passive devices for the rest of the spectrum. But since audiophiles reject the use of active equalizers to boost bass, the second far less efficient and less controllable method is invariably preferred by them. This also opened up a market for a whole new class of devices that was never seen before the last decade or two, the outboard subwoofer as a supplement for what are touted to be full range high quality speaker systems.
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Old 12th May 2011, 03:57 PM   #17
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I am not quite in that category, the planned system is bi or triamped with active crossover or 2 miniDSP's if I can convince my wife to let me sell a kindney or something. Maybe I can start with just one... I know I can stop, if I wanted to.
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Old 12th May 2011, 04:32 PM   #18
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Sorry Digits -I hope you dig it - but I have another question to Soundminded , that I thought it was implicit with my previous sentence.
So you think that a non..audiophile would need the 'black box' ,then rotate some knobs to fit them to their like ....
I've got the answer !!! Google Traduttore
which doesn't relate to BSC ,of course
The problems are the audiophiles and their wives !!!
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Old 12th May 2011, 04:49 PM   #19
AllenB is offline AllenB  Australia
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Originally Posted by Soundminded View Post
adjacent walls and other reflecting surfaces <snip> bass shy unless bass output is increased
Above the schroeder frequency, adjacent surfaces some distance away will contribute a series of peaks and cancellations rather than a certain level of overall reinforcement.

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Either boost the bass input signal to the power amplifier stage....
Trying to specifically boost a cancelled part of the spectrum would be futile and is ill-advised.
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Old 12th May 2011, 06:27 PM   #20
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Originally Posted by AllenB View Post
Above the schroeder frequency, adjacent surfaces some distance away will contribute a series of peaks and cancellations rather than a certain level of overall reinforcement.


Trying to specifically boost a cancelled part of the spectrum would be futile and is ill-advised.
Floyd Toole has written extensively on bass response and how to achieve uniformity. That IMO is his one major contribution to audio knowledge. Where does he recommend locating LF speakers and how many?
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