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In the Forum: Horn-Loaded Speakers
In the Thread: Back chamber
Post Subject: I would not worry about it. Set it once and forget.Posted by Romy the Cat on: 9/21/2015
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 noviygera wrote:
1. Let's say the my original back chamber from the manufacturer is a good "starting point". Is Romy saying that those last few hertz of the fine tuning of the chamber volume are very important and audible, in other words the manufacturers design may be roughly correct but in my room and with my speaker placement it's worth it to further adjust the volume, in which case the manufacturer's design may not be optimal?I am talking NOT about midbass horn here, I am talking about midrange horn 300 to 2Khz.2. Further, once above chamber volume is fine tuned, how important is the shape of this chamber?3. No mention of sound absorbing material in back chamber. Is it needed?
   
Well, if we had “manufacturers” of the midbass horns then it is very true they will be very seldom “correct”.  There is however no manufacturers and all midbass horns are home made. Still, even the home made horn are very seldom correct, including my own midbass horns. The temperature is change, the furniture is moved, the driver cone suspension become less stiff as the driver work mode, the magnet get demagnetized… All of it and a few other factors make the perfect size of the back chamber made with precision of 1 Hz of Fs to be a bit imperfect. Why? Well, do you change your chamber calibration when season change in case your back chamber expose to temperature fluctuation. Do you re-adjust your back chamber after I would say a year of use when you diaphragm got more broken-in? Do you adjust your back chamber after you change your output tube on your DSET and the plate impedance was 10% different then during the calibration? So, the point that I making is that the precision of back chamber is in a way always approximate and we just set it when it shall be precise but we do understand that it will run away and will not be precise. I do not feel that it is bad to revise the precision once a while but I do not think that many people do it out there. It is like the people who rotate the large woofers – we all know that we need to fight gravity but how many people in reality do it?
   
 
About the need to deal with precision of back chamber at 300Hz? Yes, I would do it but the impact would be much lower. The type of the lower know that you get at 300Hz will be to a great degree overridden by your upper midbass channel. Also, as you set up your back chamber at 300Hz once it will hardly move away from it. So, I would not be too anal about back chamber at 300Hz.

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