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Frequency response graph of a B200 SP1039? or the 104ab?

 
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Mike G
Junior Contributor 10+


Joined: 04 Apr 2009
Posts: 19

PostPosted: Sat May 02, 2009 3:18 pm    Post subject: Frequency response graph of a B200 SP1039? or the 104ab? Reply with quote

As most people on here know I am trying to redesign my 104ab's. I am at the stage where I am trying get my new VIFA XT25 tweeters to fit in with the rest of the design. On the advice of others here I am persevering with some of the free software found online. One of the programs out there allows you to take an image and trace both frequency and impedance and export them to .FRC and .FRD files. With these file types you can generate a lot of data.

Through the stats found here and one other site I have found all the VAS numbers. From this it appears that I have the essential impedance information for taming any major resonance issues. All I need is a accurate picture of the frequency response so I can start mapping out my crossover point. I am not worried about the lower end of the frequency of the driver as I am not going to be changing the passive radiator or the volume of the enclosure. This is going on the idea that the passive radiator is having little influence on the driver at non resonate frequencies.

I have found a way to measure the impudence across the frequency spectrum but even though I have good audio equipment I have no way of doing this accurately with frequency.
Someone out there must have a FRC file. There are so many speakers that have built with this driver over the last thirty years surely not everyone did it in the dark. Or did they?
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proffski
Über Contributor 1000+


Joined: 22 Aug 2003
Posts: 1296
Location: Tewkesbury UK

PostPosted: Sun May 03, 2009 2:19 pm    Post subject: Re: Frequency response graph of a B200 SP1039? or the 104ab? Reply with quote

When I was deeply into building loudspeakers back in the 1960s I used a slide rule and later a calculator.

I thought I had reached the pinnacle of design when I could afford my first scientific calculator!
Theory is obviously important to understand first but I usually find that subjective results in my room come into play and one does sometimes have to meander from the beaten path.

One set of KEF based speakers I made sounded dreadful in my room which has a wooden suspended floor. I once lent that system to a friend for a small party; his room dimensions were similar with a solid concrete floor. The difference was astounding! There they sounded fantastic!
I did not keep them for very long after that.

Being a bit of a computer luddite I find using proprietary software a tad of a challenge...
I currently still use “Eminence Speaker Designer” software which is the same as far as I know as the “Bass Box Pro” from Harris Tech, found here: http://www.ht-audio.com/

Books were a great help, some which included the following.
The Loudspeaker Design Cookbook by Vance Dickason, Bullock on Boxes, Loudspeakers by G.A. Briggs, Advanced Speaker Designs By Ray Alden, and so on...
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speakerguru
VIP Contributor 750+


Joined: 18 Nov 2005
Posts: 954
Location: Green Hut, Tovil

PostPosted: Tue May 05, 2009 7:17 am    Post subject: Re: Frequency response graph of a B200 SP1039? or the 104ab? Reply with quote

Mike G wrote:
Someone out there must have a FRC file.


Shocked FRC file! Before 1975 when KEF bought their first HP Fourier Analyser the only frequency response (amplitude only) available would have been on a slip of B &K paper from one of their chart recorders.
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Mike G
Junior Contributor 10+


Joined: 04 Apr 2009
Posts: 19

PostPosted: Wed May 06, 2009 1:05 pm    Post subject: Reply with quote

Hey guys
Thanks for letting me know That I am not talking to myself Smile I was thinking that there must have done tests on the speakers more recently. I have done my best to simulate it in Unibox using numbers on paper. From what I can tell it is doing a pretty good job. Not exact my any means but it can spit out FRC.

I am also getting VERY frustrated with Speaker Workshop. I built my test crossover and my drivers but when I try to get it to show frequency response of the crossover it tells me that there is "no final impedance value". I have no idea how I get around this. I can't find a forum for the program, and there is no manual that I know of. I have read the online walk through. But it fails to deal with any problems. Confused

I would consider buying software for this is not an option at the moment. So I have to work with what I have.
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