Going Active. Help me to understand these terms

[Theride 10+ year member]

Ive been reading up on these things for a long time. Since this is my first time trying to go into the TECHNICALS of car audio, these are kinda hard to comprehend.

Ok, so I understand frequency(or so i think) If a tweeter is made to be crossed at 2.5khz to 5.0khz, i shouldnt go lower like 1.2 or 2.0.

Now.. Octave Slope, I see 12db octave slope, 18 and 24. I read something that its the roll-off something. roll-off what? lets say i set my tweeter to 3.5khz, is it ok to set the slope at 12db octave? would you hear a difference if you set it at 18 or 24? Is changing the slope a personal thing to YOU or is it a general guide made by the manufacturer? for example, if i set the tweeter at 3.5khz, is it a MUST that it is set to 12db octave slope?

Now, while researching an ACTIVE AMP, Some of the guys dropped some new things that i never heard of. One of the guys said the amp has to have.... x1 and x10..... huh? what does this do?

Bandpass-im using a 4ch amp. 1/2 for tweeter and 3/4 for midwoofer. and a separate amp for subwoofer. how does bandpass play any role in this?

Subsonic?- i dont even know how to formulate a question about this.

Time Alignment. I think I have an understanding of this.

bare with me guys. im coming from runing 5x7 boss coaxial speakers. Im used to set it to my liking and forget it. But going active or even messing with high-end equipments, you have to have some understanding as it will be an expensive mistake.

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[audioholic 5,000+ posts]

Ive been reading up on these things for a long time. Since this is my first time trying to go into the TECHNICALS of car audio, these are kinda hard to comprehend.
Ok, so I understand frequency(or so i think) If a tweeter is made to be crossed at 2.5khz to 5.0khz, i shouldnt go lower like 1.2 or 2.0.

Now.. Octave Slope, I see 12db octave slope, 18 and 24. I read something that its the roll-off something. roll-off what? lets say i set my tweeter to 3.5khz, is it ok to set the slope at 12db octave? would you hear a difference if you set it at 18 or 24? Is changing the slope a personal thing to YOU or is it a general guide made by the manufacturer? for example, if i set the tweeter at 3.5khz, is it a MUST that it is set to 12db octave slope?

Now, while researching an ACTIVE AMP, Some of the guys dropped some new things that i never heard of. One of the guys said the amp has to have.... x1 and x10..... huh? what does this do?

Bandpass-im using a 4ch amp. 1/2 for tweeter and 3/4 for midwoofer. and a separate amp for subwoofer. how does bandpass play any role in this?

Subsonic?- i dont even know how to formulate a question about this.

Time Alignment. I think I have an understanding of this.

bare with me guys. im coming from runing 5x7 boss coaxial speakers. Im used to set it to my liking and forget it. But going active or even messing with high-end equipments, you have to have some understanding as it will be an expensive mistake.

Octave slope.

An octave is a doubling or a halving of the frequency. So 100ha is 1 octave above 50hz, and 25hz is 1 octave below 50hz.12.5hz is 2 octaves below 50hz.

Slope is how steep the frequency roll off is at the cut off frequency. In other words, if you set your crossover at 100hz (lowpassed), it is not a brick wall that stops everything above 100hz. A crossover with a slope of 12db/octave means for every octave moved away from the crossover point, there will be a loss of 12db's of output. If your crossover is set at 100hz (lowpassed), at 200hz the crossover will filter out 12db worth of material (it will be 12db quieter). At 400hz it will be 24db quieter. A crossover with a 24db/octave slope will, of course, cut off the sound twice as fast.

There is no best slope for a crossover. In some instances you want a sharp transition (cutoff) between speakers, while other times you want a gentle transition. Generally speaking, subs like steeper slopes (18 and 24db) while mids and tweets like a shallower slope (6-12db), but this is speaker/install/listener preference dependent. The best crossover is one that allows you to adjust your slope to find out exactly what cutoff point, and slope, works best for your setup.

Now that you understand the slope is how steep the crossover filters out the sound, you should understand that slope affects the crossover point. Generally speaking its bass that kills a tweeter. If you run it to too low of a frequency, the diaphragm will bottom out and damage will occur. This is why watching the HP filter on your tweeters is critical. Back to slope affects xover point... say you can safely run your tweeters down to 3.5khz with a highpass (HP) filter with a slope of 12db/octave. If you changed to a 24db/octave slope, you could possibly run down to 3.3 or 3.2khz, because the xover is filtering out the bass quicker once the xover point is met. That is simply an example, as I said many times people run a mere 6db/octave slope to HP filter their tweeters because a sharper slope can sometimes create an audible anomaly in this range due to it being in the middle of the human ear's most sensitive frequency range.

The amp has to have x1 or x10. That's a new one on me. No clue what they are talking about.

Bandpass. In this context, bandpass simply means the speaker in question will have both a highpass filter, and a lowpass filter. In a 3-way setup (tweeter, mid, sub), the midrange is "bandpassed" because it has a highpass filter cutting off bass between it and the subwoofer, and it has a lowpass filter blocking treble that passes to the tweeters. The term bandpass originated from the phrase 'pass band', which simply means the band of frequencies that the filters allow to pass through them. The midrange in my example might have a pass band of 80hz to 3.5khz.

Subsonic. This is referring to the subsonic filter. A subwoofer in a vented enclosure should also ba bandpassed. Most people just think of the lowpass filter on a sub (80hz and below for example) but a vented sub should also have a filter blocking too low of frequencies from passing to it. Vented enclosures are tuned to a spoecifc freq, and when the sub plays notes lower than it, cone excursion increases rapidly. Over excursion to the point of damage can occur quickly. So a subsonic filter will be placed on the system to guarantee nothing below 20hz passes to the sub, again for example. Slope is also a factor on a SSF, but most SSF's have a very steep slope so it can be applied at as low a frequency as possible.

Time alignment, ask if you have any questions.

Hope I helped.

 

[ciaonzo 5,000+ posts]

He's referring to the x10 button present on some amplifiers that changes the frequency adjustment from, let's say 50 - 500Hz, to 500 - 5kHz in order to facilitate a tweeter filter point.

 

[RMF419 10+ year member]

Great answer, I picked up some understanding on slope. I need to go do some tinkering with my setup now.

 

[neomac3444]

audioholic nice write up that was great information!

 

[supermaxx123 10+ year member]

Best to get a good processor, something from audiocontrol or the RF 360(haven't used one but i want to). I have used a coustic and clarion active crossovers but the digital is a lot easiser. I am using the Audiocontrol DQX and like it except it does not have slope changing option to everything is at 24db.

Any 4ch amp with a seperate processor will let you go active. A 6ch will let you go 3-way front active which I want to try but am limited on space. I also understand headunits will do processing jobs so look out for those.

 

[keep_hope_alive Premium Member]

You mention buying an ACTIVE amp. That is tough - since most amps don't have crossover points in the mid/tweeter range. Hence the comment on a x1/x10 crossover frequency multiplier switch. Not many amps have that feature. Also, to get bandpass crossovers in an amp is also expensive. Audison LRx amps have those features - for a grand or more. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

The discontinued Alpine PXA-H701 lets you have 8 channels for an active three way front stage, sub, and mono rear fill. You can get them used with the RUX-C701 controller for around $400. Great flexibility but you want an Alpine HU to control the volume. Audison BitOne is another great 8 channel processor.

You can certainly go active for less, but as you've seen you need flexible crossovers, time alignment is bonus, and EQ of some sort. The Pioneer 800PRS and 880PRS or the new DEX-99RS let you go active inside the HU. Nice pieces by Pioneer IMO.

 

[audioholic 5,000+ posts]

He's referring to the x10 button present on some amplifiers that changes the frequency adjustment from, let's say 50 - 500Hz, to 500 - 5kHz in order to facilitate a tweeter filter point.

Ah, right.

 

[Theride 10+ year member]

Octave slope.
An octave is a doubling or a halving of the frequency. So 100ha is 1 octave above 50hz, and 25hz is 1 octave below 50hz.12.5hz is 2 octaves below 50hz.

Slope is how steep the frequency roll off is at the cut off frequency. In other words, if you set your crossover at 100hz (lowpassed), it is not a brick wall that stops everything above 100hz. A crossover with a slope of 12db/octave means for every octave moved away from the crossover point, there will be a loss of 12db's of output. If your crossover is set at 100hz (lowpassed), at 200hz the crossover will filter out 12db worth of material (it will be 12db quieter). At 400hz it will be 24db quieter. A crossover with a 24db/octave slope will, of course, cut off the sound twice as fast.

There is no best slope for a crossover. In some instances you want a sharp transition (cutoff) between speakers, while other times you want a gentle transition. Generally speaking, subs like steeper slopes (18 and 24db) while mids and tweets like a shallower slope (6-12db), but this is speaker/install/listener preference dependent. The best crossover is one that allows you to adjust your slope to find out exactly what cutoff point, and slope, works best for your setup.

Now that you understand the slope is how steep the crossover filters out the sound, you should understand that slope affects the crossover point. Generally speaking its bass that kills a tweeter. If you run it to too low of a frequency, the diaphragm will bottom out and damage will occur. This is why watching the HP filter on your tweeters is critical. Back to slope affects xover point... say you can safely run your tweeters down to 3.5khz with a highpass (HP) filter with a slope of 12db/octave. If you changed to a 24db/octave slope, you could possibly run down to 3.3 or 3.2khz, because the xover is filtering out the bass quicker once the xover point is met. That is simply an example, as I said many times people run a mere 6db/octave slope to HP filter their tweeters because a sharper slope can sometimes create an audible anomaly in this range due to it being in the middle of the human ear's most sensitive frequency range.

The amp has to have x1 or x10. That's a new one on me. No clue what they are talking about.

Bandpass. In this context, bandpass simply means the speaker in question will have both a highpass filter, and a lowpass filter. In a 3-way setup (tweeter, mid, sub), the midrange is "bandpassed" because it has a highpass filter cutting off bass between it and the subwoofer, and it has a lowpass filter blocking treble that passes to the tweeters. The term bandpass originated from the phrase 'pass band', which simply means the band of frequencies that the filters allow to pass through them. The midrange in my example might have a pass band of 80hz to 3.5khz.

Subsonic. This is referring to the subsonic filter. A subwoofer in a vented enclosure should also ba bandpassed. Most people just think of the lowpass filter on a sub (80hz and below for example) but a vented sub should also have a filter blocking too low of frequencies from passing to it. Vented enclosures are tuned to a spoecifc freq, and when the sub plays notes lower than it, cone excursion increases rapidly. Over excursion to the point of damage can occur quickly. So a subsonic filter will be placed on the system to guarantee nothing below 20hz passes to the sub, again for example. Slope is also a factor on a SSF, but most SSF's have a very steep slope so it can be applied at as low a frequency as possible.

Time alignment, ask if you have any questions.

Hope I helped.

Thank you. that helped greatly. I will read and re-read your reply so it click properly.

 

[Theride 10+ year member]

You mention buying an ACTIVE amp. That is tough - since most amps don't have crossover points in the mid/tweeter range. Hence the comment on a x1/x10 crossover frequency multiplier switch. Not many amps have that feature. Also, to get bandpass crossovers in an amp is also expensive. Audison LRx amps have those features - for a grand or more. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif
The discontinued Alpine PXA-H701 lets you have 8 channels for an active three way front stage, sub, and mono rear fill. You can get them used with the RUX-C701 controller for around $400. Great flexibility but you want an Alpine HU to control the volume. Audison BitOne is another great 8 channel processor.

You can certainly go active for less, but as you've seen you need flexible crossovers, time alignment is bonus, and EQ of some sort. The Pioneer 800PRS and 880PRS or the new DEX-99RS let you go active inside the HU. Nice pieces by Pioneer IMO.

The thing is i just got a pioneer DVD HU that i like and would like to keep.

 

[Theride 10+ year member]

You mention buying an ACTIVE amp. That is tough - since most amps don't have crossover points in the mid/tweeter range. Hence the comment on a x1/x10 crossover frequency multiplier switch. Not many amps have that feature. Also, to get bandpass crossovers in an amp is also expensive. Audison LRx amps have those features - for a grand or more. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif
The discontinued Alpine PXA-H701 lets you have 8 channels for an active three way front stage, sub, and mono rear fill. You can get them used with the RUX-C701 controller for around $400. Great flexibility but you want an Alpine HU to control the volume. Audison BitOne is another great 8 channel processor.

You can certainly go active for less, but as you've seen you need flexible crossovers, time alignment is bonus, and EQ of some sort. The Pioneer 800PRS and 880PRS or the new DEX-99RS let you go active inside the HU. Nice pieces by Pioneer IMO.

I got a Audioque 90x4 amp.

 

[keep_hope_alive Premium Member]

Ah, so you already have the head unit and the amp. Well, have fun! You seem to have the information you need.

 

[bmoney9 10+ year member]

audioholic..darn good write up..helped me out too! haha