# specs, 1503 vs. 1803

Discussion in 'Archived Threads 2001-2004' started by Greg P, Jan 13, 2002.

1. ### Greg P Stunt Coordinator

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For my first sub project I think I have finally narrowed down the drivers and the application. Im going to use the 1503 or 1803 blueprint drivers with a QSC amp and a BFD in a sealed enclosure. After listening to some subs with several different Qs low and high I believe a Q of .647 should suite my tastes.

Question #1 - I want to see what the response curve of these drivers aftter the fs. I tried to download unibox in excel but all I got was numeric computer codes. I only want the sub flat to about 22hz so I should need to much power fo eq. Can someone help me with downloading this?

Question #2 - I used the formulas from diysubwoofers.org to calculate box size, and with a Q of .647 I got 36.17 liters for the 1503, and I got 115.72 liters for the 1803. (This is why I believe I'll go with the 1503 because it can go in a tiny box.) Is there that big a difference in volume needed for these 2 drivers? Is this correct?

2. ### Greg Monfort Supporting Actor

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Question #1 -

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Can't help here, I use BoxPlot and Lspcad.

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Question #2 - I used the formulas from diysubwoofers.org to calculate box size, and with a Q of .647 I got 36.17 liters for the 1503, and I got 115.72 liters for the 1803. (This is why I believe I'll go with the 1503 because it can go in a tiny box.) Is there that big a difference in volume needed for these 2 drivers? Is this correct?

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Yes, look at Vas and Qts. An increase in either causes an increase in Vb for a given alignment, and the 1803 is much more in both, so it needs a much larger Vb (less resistance) to work against.

As for correctness, you'll need to factor in VC heating/stuffing effects if you're going to be so specific WRT Qtc. This would entail measuring prototypes while playing music at the desired SPL to get it exact.

Regardless, unless some was factored in when you calculated these, Qtc will rise a bit in actual use.

GM