| about us | advertise | careers | links |

[an error occurred while processing this directive]


Woofer Impedance (Factory Rated 4 Ohm @ 25W)

Frequency (Hz)
Voltage (mV)
Current (mA)
Impedance (Z)
50
298
25.0
11.9
75
292
10.8
27.0
100
285
22.2
12.8
125
282
30.9
9.13
150
279
36.5
7.64

Even though significant factors (especially near the free air resonance frequency) of inductive and capacitive reactance are left out for simplicity, rest assured that this driver is not anywhere near 4 Ohms. If I was to assign a meaningful impedance to this port loaded driver, it would be in the 8 Ohm range.

The Satellites

Like the subwoofer, the satellite specs are not specified by the manufacturer. Instead of round units, Logitech chose oval ones so that tall, narrow enclosures would take up less precious desktop space. Labeled as 3 Ohm, 8W units, I was able to make a few measurements across the audio range.

Satellite Impedance (Factory Rated 3 Ohm @ 8W)

Frequency (Hz)
Voltage (mV)
Current (mA)
Impedance (Z)
150
106
18.8
5.64
315
102
19.4
5.26
1000
100
20.8
4.81
3150
97.1
17.8
5.46

Affecting power measurements, and thusly power ratings, the satellite impedance isn't anywhere near 3 Ohms--more like 5 Ohms for the purposes of power calculations.

Rated R.M.S. Power Output

At least Logitech didn't fall for the ludicrous PMPO (peak music power output) specification. However, I was shocked when I opened the woofer case to view it's mysterious guts. Logitech has committed audio suicide by doing the unthinkable--using a switching power supply instead of a linear one. Never intended for audio use and regarded as taboo by all worthy audio engineers, the X2's were compromised before powering them up. The main filter cap, the part that helps the amps remain stable during periods of high output, was a paltry 2700uF. All this mess for a per unit savings of maybe $2-4; what a shame.

The internal amp is the tried and true Philips TDA 1554Q (q for quad). A quick trip to the Philips semiconductor site produced the Adobe .pdf file, which shows a maximum power output of 22W @ 10% THD for a BTL (bridged tied load) application, which the subwoofer uses. The satellite single ended output was rated at 6W (each channel) @ 10% THD. Both power specs are for 4 Ohms loads. Even if these numbers were accurate, a THD of 10% is unlistenable for any length of time; a figure below 1% THD is more appropriate. If Logitech changed it's ratings for the SoundMan to reflect that lower THD, the total output might drop from 40W to 25W--big difference, especially for the marketing folks.

Frequency Response

The intentional bass hump is caused from either the loaded port design and/or an intentional preamp eq curve. These measurements were taken with the sub placed at the corner of two walls, which gives a theoretical 12dB boost centering in the 100Hz range. The 64-90Hz boost is not a reflection of the natural boost as free air measurements confirmed the moderately wide hump.

The satellite driver produces sound only in the low to upper midrange. Rolling off sharply after 8.5kHz, no appreciable sound output was heard or measured in the 10-20kHz range.

Overall Frequency Response

Bass (rel. 100Hz)
Midrange (rel. 1kHz)
Highs
90-64Hz = +3 to +7dB
2.2-3.0kHz = +1 to +3dB
10-20kHz = Severe Rolloff
61Hz = Flat (0dB)
8.5kHz = 0dB
 
58Hz = -3dB
   
55Hz = -6dB
   

 





Web Target PC




 

[an error occurred while processing this directive]

Contact us | About us | Advertise
Copyright 1999-2007 TargetPC.com. All rights reserved. Privacy information.


targetpc