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I have read the article on Martin King's website which compares open baffle, U-frame and H-frame speakers. He talks about setting the depth of the U or H frame to push the first quarter wavelength resonance above the crossover frequency. Unfortunately for me, I do not speak math. My current bass speakers are MCM 21" woofers in U-frames that are 24"x24"x16" deep. These are mated with Fostex 166en speakers, which in their own 9" deep U-frames roll off at about 200hz at 12db/oct without any additional crossover. To get a decent combined FR, I am rolling the bass speakers off at 60hz, 12db/oct. Based upon what I have read, I suspect that the bass U-frames are too deep. Can anyone explain to me how to calculate the correct depth for the U-frames?
I have read other posts talking about modifying the Qtd(s) of a driver with series resistance and how damping factor of amp affects drivers etc. I'm not sure if I understand the discussion completely, but I got the idea that series resistance does have *some* effect on the driver's behavior.
If I use two bass drivers and connect them either in series or parallel in one U frame above the other how does the bass extension or SPL vary from the pair. In each case. I have the option of passive XO or active plus biamping and 4ohm load is no problem for my SS amp(s). I realise I will have to change passive XO to account for 4ohm or 16 ohm load at the same frequency, but which connection of drivers would be preferable and why?
Martin said"Adding series resistance will increase the effective Qts of the speaker, it won't change the basic driver's T/S parameters (notice speaker refers to a system and driver is the woofer itself). The SPL response will be impacted and if looked at as a system, resistor and driver, it will appear to be a higher Qts speaker. It accomplishes this by reducing the SPL/2.83 V/m value, the resistor forms a voltage divider with the driver so the driver will only see a portion of the input signal. A resistor will increase the effective Qts but bring down the specified SPL/2.83 volt/m so there is no free lunch."I realise that the Qts of each individual driver does not change since it is the combination of electrical and mechanical properties of that individual driver (correct?). I suppose my question should have been phrased " can the Rvc resistance of each of the two drivers in series be considered as adding external resistance to the other driver and *that* raises the effective Qts of the *system* of two drivers in an open baffle". Not many free lunches unless you go to supermarket product launches.Re: introduction to your article about parallel vs series connection of drivers:I was once told by my supervisor before I had to present a seminar, "only tell them half of what you know--that way you will have something to say during question time". Ozziozzi
I realise that the Qts of each individual driver does not change since it is the combination of electrical and mechanical properties of that individual driver (correct?). I suppose my question should have been phrased " can the Rvc resistance of each of the two drivers in series be considered as adding external resistance to the other driver and *that* raises the effective Qts of the *system* of two drivers in an open baffle".
....Just looking at the modified SPL curve it looks like a higher Qts driver but with a reduced output compared to the original driver's SPL curve.
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