The Tech Test.

[thch 10+ year member]

--No need to PM me new answers, you can check for yourself now!--

---Feel free to PM me other Questions, Compliments, or Criticisms--

this was from an idea i had for an "installers litmus test". basically simple Qs that rcould be used to determine an installers views on certain topics and how likely they would be to mislead you (intentionally or otherwise). from a chat on IRC, i'm not sure how applicable it is to that purpose. As far as i can tell, all questions have definate correct answers to a fairly high degree of certainty. assume that if there is one exteme case, eg only would be true in an RV or with the addition of unessary signal processing, that that case won't happen. obviously with DSP you could make a case for almost any answer to be true.

here is the test, now on its 3rd revision:

1*.) line drivers are devices that increase the signal's voltage on its way to the amp. the gain on the amp can be turned down and the amplifier doesn't have to amplify the signal as much, which of the following might be (an) advantage(s)?

A -- the amp runs cooler

B -- the amp will play less noise

C -- Both

D -- None of the above

2*.) Two woofers are installed in a custom fiberglass box in the trunk of a car. the woofers are aimed towards each other.

A -- both woofers should be wired out of phase.

B -- both woofers should be wired in phase.

C -- one woofer should be wired in phase the other out of phase

D -- Either A or B

E -- Different for every install

3*.) A user has a component set with the tweeter in the dash, and the mid in the door. the speakers are angled differently.

A -- both speakers should be wired out of phase.

B -- both speakers should be wired in phase.

C -- one speaker should be wired in phase the other out of phase

D -- Either A or B

E -- Different for every install

4.) Component sets are placed with the tweeter in the dash, and the mid in the door. what crossover is most likely the best?

A -- 12dB/oct Linkwitz-Riley

B -- 24dB/oct Linkwitz-Riley

C -- 12dB/oct Butterworth

D -- 24dB/oct Butterworth

5*.) a subsonic filter is used in a ported box setup. it should be set to what frequency:

A -- 5hz below tuning

B -- 1/3rd octave below tuning

C -- Different for each system

D -- Same for each system, but not A or B

6.) a class AB amplifier is running at 1/3rd of its rated power output. what would be a typical efficiency?

A -- 16%

B -- 33%

C -- 47%

D -- 60%

7.) MOSFETs are almost universally found in what part(s) of the amplifier:

A -- Audio Amplification

B -- Audio Filtering (crossovers)

C -- Power Supply

D -- Two of the above

E -- All of the above

F -- None of the above

8.) Some EQ filters have a high Q setting, standing for "Quality". what defines a high "Quality" filter?

A -- compatibilty with SACD/DVD-A formats

B -- High priced components

C -- affects a large range of frequencies

D -- affects a small range of frequencies

E -- None of the above.

9.) will setting the gains on an amplifier all the way up cause it to clip?

A -- Yes, in all cases.

B -- Not always, but in some cases.

C -- Never.

10*.) DMMs should be used as the definitive method for setting gains?

A -- Yes

B -- No

i will PM the results and explainations back to you. this is because anyone who gets a 10 of 10 would have a confirmed answer key on the post.

also, if you don't do well, don't feel bad. thus far the best i've seen has been a 6 of 10 which included guesses that were correct.

* -- this Q should be correct if you are a salesman/installer. for instance, i would not buy equipment from someone who got the answers wrong (within reason).

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[flakko 5,000+ posts]

lol its funny cuz i can bet 80 percent of the installers won't be able to get the *'d q's correct

 

[skmfkr 5,000+ posts]

isnt 5 one octave?

 

[thch 10+ year member]

i'm fairly optimistic. the unstarred questions (except for #8) are the most missed ones and also the ones least important for installing.

i had to edit #6 already. never realized how efficient an ideal class B output stage could be at 1/3rd power. anyone who knows how to mathmatically derive output stage efficiency would be misled.

 

[thch 10+ year member]

isnt 5 one octave?

if you think so than then you would answer D -- same for each system, but not listed above.

obviously if i give out the answers on the post then anyone attempting to take the quiz would have, well, an unfair advantage.

 

[faulkton 5,000+ posts]

Dam that was hard. i dont have any installer skillz and only scored 3. Oh well //content.invisioncic.com/y282845/emoticons/crap.gif.7f4dd41e3e9b23fbd170a1ee6f65cecc.gif

 

[squeak9798 5,000+ posts]

4.) Component sets are placed with the tweeter in the dash, and the mid in the door. what crossover is most likely the best?

A -- 12dB/oct Linkwitz-Riley

B -- 24dB/oct Linkwitz-Riley

C -- 12dB/oct Butterworth

D -- 24dB/oct Butterworth

Little ambiguous.

Crossover what? Highpass the mid? The tweeter? Lowpass the mid?

"Best" how? Best power handling? Best low frequency output? Best phase shift?

Shouldn't there be a "E - Setup dependent" here? I don't really see how this one has a "definate correct answers to a fairly high degree of certainty."

Likewise, #5 has an "generally accepted" correct answer.....but is it really *wrong* to not do such? For a retail installer, wouldn't it generally be a good practice to set it a little higher due to the general stupidity the general public as to help avoid idiots damaging their products?

 

[squeak9798 5,000+ posts]

1*.) line drivers are devices that increase the signal's voltage on its way to the amp. the gain on the amp can be turned down and the amplifier doesn't have to amplify the signal as much, which of the following might be advantages?

A -- the amp runs cooler

B -- the amp will play less noise

C -- Both

D -- None of the above

B -- the amp will play less noise

Define this answer. The amp will have a lower SNR? Or are you referring to less noise being present in the input signal (and hence "the amp will play (output?) less noise)?

If I'm going to be answering a question, I want to be sure I fully understand your rational as the question/answer originator before selecting an answer //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif Again, this one left me with a little ambiguity.

 

[thch 10+ year member]

Little ambiguous.
Crossover what? Highpass the mid? The tweeter? Lowpass the mid?

"Best" how? Best power handling? Best low frequency output? Best phase shift?

Shouldn't there be a "E - Setup dependent" here? I don't really see how this one has a "definate correct answers to a fairly high degree of certainty."

Likewise, #5 has an "generally accepted" correct answer.....but is it really *wrong* to not do such? For a retail installer, wouldn't it generally be a good practice to set it a little higher due to the general stupidity the general public as to help avoid idiots damaging their products?

this questions asks which is most likely the best and has a correct answer based upon the conditions given. why not take the test and i'll pm you the correct answers and if requested, why.

as for question #1, the key word here is "might be". this means not in all cases. i need to edit it because i say "advantages" instead of "advantage(s)". i don't want to imply that answers listed are wrong due to grammer.

edit -- as for #5, i've seen many "generally accepted" answers ranging from 1 octave, 10hz, 12hz, 5hz, 1/3rd octave, 1/6th octave, 7hz, and so on. i can't list all of these options though.

and crossover -- mid = lowpass, tweeter = highpass. at the same frequency. thats seems the only logical way to do it.

 

[squeak9798 5,000+ posts]

as for question #1, the key word here is "might be". this means not in all cases. i need to edit it because i say "advantages" instead of "advantage(s)". i don't want to imply that answers listed are wrong due to grammer.

Grammatical errors aside....you didn't answer my question //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif I don't want to respond with a given answer and be *wrong* because my definition of the answer listed is different than your definition of the answer listed. "the amp will play less noise" could be construed multiple ways.

 

[squeak9798 5,000+ posts]

PS: PM sent

 

[thylantyr 10+ year member]

1*.) line drivers are devices that increase the signal's voltage on its way to the amp. the gain on the amp can be turned down and the amplifier doesn't have to amplify the signal as much, which of the following might be (an) advantage(s)?

A -- the amp runs cooler

B -- the amp will play less noise

C -- Both

D -- None of the above

B should read the amp may amplify less noise

What the point of having a test where the answer is Different for every install or Different for each system ?

4.) Component sets are placed with the tweeter in the dash, and the mid in the door. what crossover is most likely the best?

A -- 12dB/oct Linkwitz-Riley

B -- 24dB/oct Linkwitz-Riley

C -- 12dB/oct Butterworth

D -- 24dB/oct Butterworth

You need option E. Depends on the drivers used and install .

 

[chadillac3 10+ year member]

 

4.) Component sets are placed with the tweeter in the dash, and the mid in the door. what crossover is most likely the best?

A -- 12dB/oct Linkwitz-Riley

B -- 24dB/oct Linkwitz-Riley

C -- 12dB/oct Butterworth

D -- 24dB/oct Butterworth

 

You need option E. Depends on the drivers used and install .

 

I couldn't agree more.

 

[thch 10+ year member]

1*.) line drivers are devices that increase the signal's voltage on its way to the amp. the gain on the amp can be turned down and the amplifier doesn't have to amplify the signal as much, which of the following might be (an) advantage(s)?A -- the amp runs cooler

B -- the amp will play less noise

C -- Both

D -- None of the above

B should read the amp may amplify less noise

What the point of having a test where the answer is Different for every install or Different for each system ?

4.) Component sets are placed with the tweeter in the dash, and the mid in the door. what crossover is most likely the best?

A -- 12dB/oct Linkwitz-Riley

B -- 24dB/oct Linkwitz-Riley

C -- 12dB/oct Butterworth

D -- 24dB/oct Butterworth

You need option E. Depends on the drivers used and install .

reread both questions. both have answers listed. in both cases there are answers that are acceptable, wrong, and most correct. in 4, the Q is for the "most likely" based on the situation. i'll look into played vs amplified, not sure i want to change the grammer just yet.

 

[Spr0ket 10+ year member]

This is pretty interesting to say the least. I'll prolly throw my score in the sig just for the hell of it. I wonder how bad I did.

PM Sent.