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Understanding Subwoofer Specifications.

395 views 2 replies 3 participants last post by  aidoroboo 
#1 ·

Hi,


This is my first post here.


Recently, I purchased "Wharfedale MovieStar 65+ Super" Speaker system. Specifications of its Subwoofer given in the Product Brochure were as under:


01. Boundary Position:28-170 Hz;

02. Crossover Range: 35-85 (10 Hz step);


However, when I got the product, I noticed that:

a. No Boundary Position was given in its User Manual;

b. Crossover Range was 70-170 Hz in User Manual as well as on the Subwoofer itself;

c. LF Response (fb) was given as 45 Hz in the User Manual.


I request you to kindly let me know that:

i. What is the meaning of "Boundary Position: 28-170 Hz"?

ii. What is the meaning of "LF Response (fb): 45 Hz"?

iii. What is the Frequency Response Range of the Subwoofer (if known to you)?


Thanks.
 
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#2 ·

Quote:
Originally Posted by vivekayush  /t/1528317/understanding-subwoofer-specifications#post_24629441


Hi,



This is my first post here.



Recently, I purchased "Wharfedale MovieStar 65+ Super" Speaker system. Specifications of its Subwoofer given in the Product Brochure were as under:



01. Boundary Position:28-170 Hz;


02. Crossover Range: 35-85 (10 Hz step);



However, when I got the product, I noticed that:


a. No Boundary Position was given in its User Manual;


b. Crossover Range was 70-170 Hz in User Manual as well as on the Subwoofer itself;


c. LF Response (fb) was given as 45 Hz in the User Manual.



I request you to kindly let me know that:


i. What is the meaning of "Boundary Position: 28-170 Hz"?


ii. What is the meaning of "LF Response (fb): 45 Hz"?


iii. What is the Frequency Response Range of the Subwoofer (if known to you)?



Thanks.

1 boundary position sounds like marketingspeak to me. Presumably they are attempting to use boundary reinforcement to exaggerate the subs low frequency extension. This is BS because, a) nobody knows how they came up with the spec and b) pure boundary reinforcement does not strengthen lower frequencies more than it does higher frequencies (within the sub's range). I'd GUESS that the 28 Hz number is intended to be a -10 dB point but there's no way to know for sure unless the mfr says what it means. In a small enough room, cabin gain will compensate somewhat for the rolloff of the sub's output, but cabin gain increases at (theoretically at most) 6 dB per octave while output is falling at 24 dB per octave, so it can never catch up . . .


2 the fb SHOULD be port tuning (ie the place where the enclosure's port output is strongest. IIRC, you can expect a ported sub to roll off at 24 dB per octave below port tuning, so by about 22.5 Hz, its output (in the best case) is 14 dB lower than at 45 Hz, or a little more than 'one notch" less than half as loud (sort of - - our hearing is less sensitive at low frequencies and while -10 dB is generally considered half as loud in the midrange it might really be, subjectively, more like a fourth as loud at 45 dB . . . . IOW no significant output very far below the tuning frequency.


I'd guess the -3dB point to be in the range of 40 Hz. But "-3 dB compared to what?" is a legitimate question that you simply cannot answer with the information given.
 
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