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In the Forum: Horn-Loaded Speakers
In the Thread: Macondo’s Midbass Project – the grown up time.
Post Subject: Resonance frequency and massPosted by Romy the Cat on: 9/1/2010
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 unicon wrote:
Roman, 
first of all I feel good about your bass horn that's what i have always bin dreaming and if i get the space for it wont even waste a minute
I think you already know it or using it ...

You mentioned using a foam in  back chamber so it adds a mass in driver and then the Fs goes down. thats a great idea and it works.and besides coupling your driver to horn you can simply measure how much is the added mass of it.

I suggest that you do add the mass in driver like coins in driver cone(and measure the coin weight too) and do added mass free air impedance test then you can see where it can bring another low resonance .then when it reaches 20% lower the free air you are getting the most out of your driver  .so in loaded horn you can be sure how much foam to add and having the goal impedance you can be almost sure everything is right.
and i suggest not to try more than 20% 

Unicon, since I heard it last two days I feel very good about my midbass horn as well. It will be some labor to integrate it properly but I feel that I will be able to do it.

Adding foam to back chamber does not add any mass in driver. Also when used in this context the word “foam” you need to specify that it is not compressible foam as a regular comprisable foam produces a very much opposite effect – it virtually expends back chamber.

If you do add mass to driver then you get exactly opposite effect as you will be dropping the Fs even lower, so I do not see your logic. I also do not see a need to wary about the actual mass. We worry about mass ONLY in context of resonance frequency. So if we measure the resonance frequency and set it where it hall be then why do we worry about the actual mass?

The Cat

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