Enclosures for Hartley 24"

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Hartley TS specs and box sizes

This is a rehash of a post I did on another forum about 18 months ago. A google search should have found it. I tested a Hartley 24" anf found it was suited to BIG boxes or open baffle. it won't work in 20 cu ft - it will have a big bass hump.

I use a pair of these in a long path dipole setup of approx 34" cubed dimensions and get pretty much flat bass down to 32Hz without needing the usual 6dB/octave boost you would normally apply to a bass dipole. I cross over at 110Hz to a stacked Quad/Decca ribbon setup.

HERE'S MY EARLIER POST INCLUDING ALL THE NUMBERS YOU'LL NEED TO MODEL A BOX FOR YOURSELF....

A google search still fails to turn up TS specs on these after all these years. So I finally decided to bite the bullet and do my public service bit and measure one.

Fortunately the heat sink pipe provided a safe and convenient place to stick all the bluetac for the mass measurement phase!

I have read online of an Fs of 13Hz and also 29Hz on various forums...both are wrong. I have also read that the unique magnetic suspension design renders TS measurements impractical or inconsistent. Turns out the speaker has fairly conventional numbers - pretty much what you would expect for a big heavy cone with a smallish motor.

Plugging the numbers into WinISD or similar gives a suggestion of a CLOSED box of 1700L or approx 60 cubic feet. So Hartely's recommendation of 24 cu ft is actually a bit small! I guess that's why lossy cabinets or open baffles are popular...to try to compromise on the size.

Anyway here are the numbers from memory...I can supply the extra decimal places if anyone really wants to know although of course numbers will vary from unit to unit. The unit tested was an original 1970s alnico type, not the modern production.

John Corneille
(Melbourne Australia)

Fs = 20.9Hz
Qts = 0.65
Qes = 0.74
Re = 3.7 ohms
VAS = 1250 litres
Sd calc to 0.22 sq metres

That's all the numbers you will need to checkout just how much artificial bass boost you'll get when using "tiny" 20 cu ft boxes!
 
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