pick the topic

[dave_Edwards 1]

Well guys---I read alot of forums and it looks as though ALOT of people are misinformed about the "basics" of car audio----I need your help----tell me a topic in which we can all give our input and see if we can come to learn more-----I personally am sick of seeing these "which sub or which amp" topics----it is called "learn then deside for yourself".

I will talk in depth about all of the topics you want but I need a start----you guys from FXN.net know me pretty well to know I can talk for days about car audio.

for the guys that don't know me----

http://www.fordexplorer.net/viewforum.php?f=10

Alot of the stickys are mine. Read and enjoy.

Live and LEARN,

Dave

[Aaron Clinton 2,372]

ok let me start off, well something that is not very clear to the general public,

when you crack your amp open, what do you want to look for in a well designed board, and good internal components????

[ss454 0]

Here is another one that a lot of people get duped on by the sales guy.

What do the specs of subs mean in a setup?

Qts

Vas

Fs

Bl

spl

xmax

Rms Power handling

Music power handling

How to you relate these into what you need in a system.

[dave_Edwards 1]

Here is another one that a lot of people get duped on by the sales guy.

What do the specs of subs mean in a setup?

Qts

Vas

Fs

Bl

spl

xmax

Rms Power handling

Music power handling

      From my post on T/S parameters

How to you relate these into what you need in a system.

Prior to 1970, there were no easy or affordable methods accepted as standard in the industry for obtaining comparative data about loudspeaker performance. Recognized laboratory tests were expensive and unrealistic for the thousands of individuals needing performance information. Standard measurement criteria were required to enable manufacturers to publish consistent data for customers to make comparisons between various loudspeakers.

Thiele-Small Parameters

In the early seventies, several technical papers were presented to the AES (Audio Engineering Society) that resulted in the development of what we know today as 'Thiele-Small Parameters'. These papers were authored by A.N.Thiele and Richard H. Small. Thiele was the senior engineer of design and development for the Australian Broadcasting Commission and was responsible at the time for the Federal Engineering Laboratory, as well as for analyzing the design of equipment and systems for sound and vision broadcasting. Small was, at the time, a Commonwealth Post-graduate Research Student in the School of Electrical Engineering at the University of Sydney.

Thiele and Small devoted considerable effort to show how the following parameters define the relationship between a speaker and a particular enclosure. However, they can be invaluable in making choices because they tell you far more about the transducer's real performance than the basic benchmarks of size, maximum power rating or average sensitivity.

Fs------This parameter is the free-air resonant frequency of a speaker. Simply stated, it is the point at which the weight of the moving parts of the speaker becomes balanced with the force of the speaker suspension when in motion. If you've ever seen a piece of string start humming uncontrollably in the wind, you have seen the effect of reaching a resonant frequency. It is important to know this information so that you can prevent your enclosure from 'ringing'. With a loudspeaker, the mass of the moving parts, and the stiffness of the suspension (surround and spider) are the key elements that affect the resonant frequency. As a general rule of thumb, a lower Fs indicates a woofer that would be better for low-frequency reproduction than a woofer with a higher Fs. This is not always the case though, because other parameters affect the ultimate performance as well.

Re--------This is the DC resistance of the driver measured with an ohm meter and it is often referred to as the 'DCR'. This measurement will almost always be less than the driver's nominal impedance. Consumers sometimes get concerned the Re is less than the published impedance and fear that amplifiers will be overloaded. Due to the fact that the inductance of a speaker rises with a rise in frequency, it is unlikely that the amplifier will often see the DC resistance as its load.

Le--------This is the voice coil inductance measured in millihenries (mH). The industry standard is to measure inductance at 1,000 Hz. As frequencies get higher there will be a rise in impedance above Re. This is because the voice coil is acting as an inductor. Consequently, the impedance of a speaker is not a fixed resistance, but can be represented as a curve that changes as the input frequency changes. Maximum impedance (Zmax) occurs at Fs.

Q Parameters---------Qms, Qes, and Qts are measurements related to the control of a transducer's suspension when it reaches the resonant frequency (Fs). The suspension must prevent any lateral motion that might allow the voice coil and pole to touch (this would destroy the loudspeaker). The suspension must also act like a shock absorber. Qms is a measurement of the control coming from the speaker's mechanical suspension system (the surround and spider). View these components like springs. Qes is a measurement of the control coming from the speaker's electrical suspension system (the voice coil and magnet). Opposing forces from the mechanical and electrical suspensions act to absorb shock. Qts is called the 'Total Q' of the driver and is derived from an equation where Qes is multiplied by Qms and the result is divided by the sum of the same.

As a general guideline, Qts of 0.4 or below indicates a transducer well suited to a vented enclosure. Qts between 0.4 and 0.7 indicates suitability for a sealed enclosure. Qts of 0.7 or above indicates suitability for free-air or infinite baffle applications. However, there are exceptions! The Eminence Kilomax 18 has a Qts of 0.56. This suggests a sealed enclosure, but in reality it works extremely well in a ported enclosure. Please consider all the parameters when selecting loudspeakers. If you are in any doubt, contact your Eminence representative for technical assistance

Vas/Cms--------Vas represents the volume of air that when compressed to one cubic meter exerts the same force as the compliance (Cms) of the suspension in a particular speaker. Vas is one of the trickiest parameters to measure because air pressure changes relative to humidity and temperature

[dave_Edwards 1]

Here is another one that a lot of people get duped on by the sales guy.

What do the specs of subs mean in a setup?

Qts

Vas

Fs

Bl

spl

xmax

Rms Power handling

Music power handling

How to you relate these into what you need in a system.

QTS=in simple terms---is it goning to be boomy or smooth sounding

Vas=air displacement of the subwoofer

Fs=free air resonace

BL=flatter the better

SPL=how much power is really needed to get them loud

xmax=linear movement of the cone

RMS=Rarely Means chit---RMS from the manufactor is measured so many ways now a days it doesn't really mean anything.

If I have the same sub----one 1.0 cub and one 10.0 cubes-----which box can take more wattage?Right the 1.0 cube-----it is always back to simple physics---smaller air chamber----less air to "pressurize"

hope this helps alittle

Dave

[dave_Edwards 1]

ok let me start off, well something that is not very clear to the general public,

when you crack your amp open, what do you want to look for in a well designed board, and good internal components????

myself----If you didn't build it and don't know what you are doing leave it alone!

but if you do know what you are doing----105 degree caps---TO3 output resistors----all that stuff really gets my blood going----to most people a good laid out board---not too much silicone----good weight is a good sign and try to stick to some type of name brand company-----do your homework---check on the amp before you buy---don't just buy it because every other guy has one.

Dave