Blog Audiofil -Audio-sisteme-scheme-boxe: woofer

duminică, 24 ianuarie 2010

vineri, 16 ianuarie 2009

Constructie SubWoofer

This design is a single fold transmission line using a 330mm (12") Audax driver (HD 33 S 66). The port loads out the back. Very little stuffing is used.

It as a SubWoofer in a Home Theater System with an active 4th order low pass at 70 Hz. Since the cross-over is low, upper resonnances ( > 150 Hz ) are not a big problem. This line is not optimized for higher crossover frequencies.

Results:

From 50 Hz to 100 Hz driver and terminus are in phase (+/-10°)
The - 3dB point is near 45 Hz
At the Fr of the line (40 Hz) driver and terminus are 90° out of phase
Below 40 Hz they are out of phase

The stuffing could have be better optimised, reducing the effect of the null at 140 Hz.

If I were to do it again I'd make the terminus a bit larger. (or use the line for a 10"/ed)

Since originally putting this project together more stuffing has been added making this a true TL. The preliminary results are that the stuffing improves the performance of the speaker. (details as they become available/ed)

Line Configuration

	Physical length	1.6 m
	Physical fs at 1/4 wl	54 Hz
	Acoustic 1/4 wl (measured)	2.13 m/40 Hz
	Measured c'	0.75c
	(speed of sound in the line)
	Begining cross section	838 cm^2
	Terminus section	262 cm^2
	Taper	1.6 : 0.5 Sd
	First odd harmonic	140 Hz
	(null of driver, max of terminus)
	Max of terminus	90 Hz
	(level of the terminus is 3 dB below the driver )
	Stuffing	50 mm Rockwool

udax PR 330 M0*

	Sd	538 cm^2
	Vas	264 liters
	Cms	6.5 e-4 N/m
	Cas	1.9 e-6m^5/N
	Mms	52 g
	Fs	27 Hz
	Bl	13.6 N/A
	Re	5.8 Ohms
	Qms	6.7
	Qes	0.28
	Qts	0.27
	Pmax	150 Watts
	Xmax	+/-4 mm

* Audax HD 33 S 66 replaced by PR 330 M0