What Affects a Woofer's Bass Response? - diyAudio
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Old 19th November 2009, 12:39 AM   #1
form109 is offline form109  United States
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Default What Affects a Woofer's Bass Response?

i have several speaker drivers laying around,and ones ive Experimented with in the Past...


it seems to me that a Weak Motor with a Very Compliant Suspension produces lower bass than a Weak Motor with a Very Stiff Suspension.

it also seems that a Stronger Motor Paired with a Stiff Suspension still goes Fairly low...the Apex Jr Super 8" is a good Example of this to me...(FS around 50 because of stiff suspension,but still able to respond strongly to low Frequencies.)..some Examples Below.

JVC 8" Woofer

Paper Cone,2" Voice Coil,Aluminimum Former,Non Vented Motor.

Foam Surround,Stiff Suspension,Simple Motor

the Woofer's FR drops noticebly below 50 Hz.

No Name 6.5" Woofer

Paper Cone,.75" Voice Coil,Thick Paper Former,Non Vented Motor.

Foam Surround,Very Flexible Suspension,Simple Motor

the woofer's excursion and FR increase Below 50 Hz...and
a fairly low amount of power causes large cone excursion.

Walmart 12" Generic Brand Car Audio Subwoofer Driver

Poly Cone,2" Dual Voice Coil,Aluminimum Former,Grilled Pole Vent.

Rubber Surround,Very Flexible Suspension,Simple Motor.

The Woofer responds strongly to low bass below 30's...sometimes the
excursion seems sloppy and i get the impresion the woofer i doing little
more than Flopping around,(Not Tightly Controlled)

Doe Anybody Have an idea what im getting at?
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Old 19th November 2009, 04:45 PM   #2
MaVo is offline MaVo  Germany
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TBH, no. But to answer your question in the topic: a) the woofers enclosure and b) the room it is in.
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Old 19th November 2009, 07:14 PM   #3
form109 is offline form109  United States
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Quote:
Originally Posted by MaVo View Post
TBH, no. But to answer your question in the topic: a) the woofers enclosure and b) the room it is in.
what im asking is really,does the Strenght of the motor affect the woofers ability to respond to bass signals?
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Old 19th November 2009, 07:22 PM   #4
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Quote:
Originally Posted by form109 View Post
what im asking is really,does the Strenght of the motor affect the woofers ability to respond to bass signals?
Yes, a strong magnetic field means the amplifier can control the cone better as the total driver Q (QTS) should be lower. You'll get more accurate bass in an optimised enclosure, rather than flabby booming bass as you'd get with a driver with a high total Q.

It's a little difficult to explain, let me attempt to think about it
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Old 19th November 2009, 07:24 PM   #5
defect9 is offline defect9  Ireland
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strength of the motor is one factor, yes. how tight the voice coils are to the magnet assembly/pole, size of voice coil, honest length of linear excursion (basically how well the suspension is made and if the motor has room for the excursion), size of magnet assembly, suspension strength/stiffness, weight of the driver, and everything MaVo mentioned. There's probably more too.
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Old 19th November 2009, 07:25 PM   #6
badman is offline badman  United States
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Of course it does. It lowers Q but raises efficiency. Response at Fs usually stays about the same, but everything above rises.
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Old 19th November 2009, 07:59 PM   #7
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I've been increasingly confronted with the affect of the room on performance lately. Just something to consider if you're getting noticeable peaks/dips in your frequency range.
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Old 19th November 2009, 09:35 PM   #8
MaVo is offline MaVo  Germany
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A big magnet, strong motor means that the speaker will need less watts to achieve the same excursion than a with a weaker motor, its more efficient. This often goes hand in hand with a lower qts value since membranes are not necessarily made heavier when motor strength increases. This in turn means that you can have a flat response in a smaller cab. But if you design all cabs for flat response, a weak motor and a strong motor will sound the same, just the cab size wil be different. Terms like "control over the cone" are misleading, as they make you think a strong motor is needed for sound quality, while this is absolutely false, as it all boils down to correct implementation of the driver.
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Old 19th November 2009, 09:41 PM   #9
MaVo is offline MaVo  Germany
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A driver at its lower frequency edge will behave like a highpass filter for the signal. Like the filter, it has a q value, which determines the shape of its response. You can wikipedia this for some pictures for better understanding. The qts is this value. It is composed of the magnet strength, suspension and so on, basically all of the drivers physical qualities. You can influence this value with an enclosure. For example, put a driver in a smaller enclosure and qts goes up.
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Old 19th November 2009, 10:25 PM   #10
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Quote:
Originally Posted by djfoundation View Post
I've been increasingly confronted with the affect of the room on performance lately. Just something to consider if you're getting noticeable peaks/dips in your frequency range.
The room be damned, IMO. Consider the placement loading, pi*x, and be aware of your room gain, but please don't modify your response to adjust for a room modal issue. FIX YOUR ROOM INSTEAD.

Good speakers in a bad room make for lousy sound. Modified speakers to suit the room modal issue makes for worse speakers.
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