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Restoring bass performance on your RS4.5's

Back to the original topic....I am going to set out working on my pair soon and I have a few thoughts....comments appreciated :)

Why would a company like Infinity leave a gaping hole below the crossover covered with foam? Acoustic Research (AR) showed way back in the late 50's/early 60's the way infinite baffle (sealed) systems work, including how stuffing the cabinets with acoustically inert material lowered resonance and resonance peaks. Not new technology when the RS4.5's were made.

Putting together that 1. Infinity was trying very hard to address the impedance peak at resonance with the Watkins principle, 2. Aperiodic venting is one way to smooth such a peak and 3. The function of a first octave high pass filter in the main woofer circuit (not the Watkin's coil/circuit)...the 300uF + 150uF is likely there to attenuate subsonic frequencies where the box will now longer act like a sealed system due to the vent in the back and to prevent the woofer from getting damaged.

Would it be wiser to start off by testing the system's impedance after replacing the piece of foam below the crossover instead of sealing the cabinet?

If the cabinet is sealed, would removing the 300uF + 150uF that is in series with the main woofer coil be better? (idk...)

Here is a link about aperiodic venting:

http://www.diyaudio.com/forums/multi-way/93686-aperiodic-enclosures.html#post1100719

(The whole thread is an interesting read)

Edit: Please leave out the part where I bring up the capacitors in series....together with the inductor they serve to smooth out the impedance. Didn't think of that till now, sorry for any confusion! The Aperiodic theory otoh still remains...
 
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I think they are pretty much sealed when the foam was in good shape. Not much air moving through that close cell foam. Rabbits setup is far nicer though. Not sure why they didn't just drill a hole and caulk it like in the rs2.5. Is there something large that has to fish through there?
 
slimpikkins said:
I think they are pretty much sealed when the foam was in good shape. Not much air moving through that close cell foam. Rabbits setup is far nicer though. Not sure why they didn't just drill a hole and caulk it like in the rs2.5. Is there something large that has to fish through there?
Click to expand...

Is there documentation available specifying closed cell foam? Even if it is closed cell foam, why would Infinity use 1" baffles in the front and seal a hole for cables to run through with only foam in the back?

The gaping hole is at least 50% larger than the cables passing through....

I will be replacing the foam with high density open cell foam first and measure T/S parameters in the box and run an impedance plot using the Partsexpress DATS V2 system...if that does not measure up right, I plan on moving forward with sealing the cabinets. Will update you all, may take a while :)
 
Perhaps the hole helped in the assembly process. Maybe the wires were soldered to what ever they go to ahead of time and then fished up from the bottom of the woofer cabinet. I guess it seemed a good idea at the time.

Interested in your findings to add to this already great thread.
 
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