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Old 11-19-2015, 10:23 PM   #1
SQ+

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amp tuning, crossovers

Could someone please explain crossovers in a way that a noobie can understand? I'm still trying to figure that out.

Here's where I'm at. My amp is a 4 ch. Alpine MRV-F340. Front and rear speakers are Boston Acoustics coaxials. The front tweeters were awful. Then, after learning a bit in this forum and in the OM, I looked at my amp's settings.

The HP and LP switches for chs 1+2 and 3+4 were set to, "Off." I set ch 1+2 to HP. I turned down the crossover point from 100 to 60. The treble then sounded much better. It no longer drowns out the mids. It no longer is serious pain to my ears. And I finally realized that BA speakers are actually pretty good.

So, although I had a guess about what to do, I was not sure why it worked. Did setting the HP lower make more lower frequencies go to the tweeter instead of the mid? If so, how would that make the tweeters sound less harsh, and stop drowning out the mids? I don't see how it works.

Does HP block lower frequencies below the crossover level setting? Does LP block higher frequencies above the crossover level setting? Does that send the correct signals to the tweeters and mids?
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Old 11-20-2015, 02:59 AM   #2
basicxj

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Quote:
Originally Posted by SQ+ View Post
Could someone please explain crossovers in a way that a noobie can understand? I'm still trying to figure that out.

Here's where I'm at. My amp is a 4 ch. Alpine MRV-F340. Front and rear speakers are Boston Acoustics coaxials. The front tweeters were awful. Then, after learning a bit in this forum and in the OM, I looked at my amp's settings.

The HP and LP switches for chs 1+2 and 3+4 were set to, "Off." I set ch 1+2 to HP. I turned down the crossover point from 100 to 60. The treble then sounded much better. It no longer drowns out the mids. It no longer is serious pain to my ears. And I finally realized that BA speakers are actually pretty good.

So, although I had a guess about what to do, I was not sure why it worked. Did setting the HP lower make more lower frequencies go to the tweeter instead of the mid? If so, how would that make the tweeters sound less harsh, and stop drowning out the mids? I don't see how it works.

Does HP block lower frequencies below the crossover level setting? Does LP block higher frequencies above the crossover level setting? Does that send the correct signals to the tweeters and mids?
Turning down the high pass filter point on the amp for a coaxial or component set doesn't affect the tweeters- coaxials usually have rudimentary crossovers by way of caps and inductors on the back of the cone, though some higher-end ones do indeed come with a real crossover network. Components usually have a proper dividing network to send appropriate frequencies to the mid and tweeter, but the high pass filter set to 60hz on either type of speaker only rolls off the frequencies below that point, with the rate those frequencies get rolled off being dependent on the slope of the filter. What has probably happened is that the lower crossover point gives you a better balance of midbass to offset the output of the tweeters. If you want more control, that usually means stepping up to component speakers and bi-amping mids and tweeters on separate amplifier channels using an electronic crossover to run them "active."

http://www.teufelaudio.com/blog/audi...ers-explained/

https://en.wikipedia.org/wiki/Audio_crossover

http://www.bcae1.com/passxovr.htm

http://www.bcae1.com/xoorder.htm

http://www.bcae1.com/elxovsp2.htm

Think of a crossover as something that gradually reduces frequencies below (in the case of a high pass) or above (in the case of a low pass) the chosen crossover point. The gradual reduction attenuates frequencies at the rate allowed by the design, type or order of the crossover being used. The steeper the slope, the more dramatic the roll off as frequencies go up or down in octave. With a few exceptions, passive crossovers are typically not adjustable for slope, and electronic aka active crossovers such as those found in head units, some amplifiers, outboard audio processors or stand-alone electronic crossovers can allow varying the chosen crossover point along with the slope.

If all you want to do is adjust output of tweeters relative to output of mids, a decent component set often has multiple attenuation settings for one or the other on the supplied passive crossovers to allow adjusting overall timbre of the set to the liking of individual users- this is usually accomplished using an "L-pad" built into the crossover network.
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Old 11-20-2015, 03:27 AM   #3
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what basicxj said. the tweeter has its own xover which probably doesnt have any adjustments. for the mids, i set mine as low as sounds good (around 80hz or so)
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Old 11-20-2015, 03:29 AM   #4
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another things thats super important...

http://www.jlaudio.com/header/Suppor...Setting/287546

heres the tones...

http://www.realmofexcursion.com/downloads.htm
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Old 11-20-2015, 12:38 PM   #5
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[quote=basicxj; What has probably happened is that the lower crossover point gives you a better balance of midbass to offset the output of the tweeters.[/QUOTE]

There is SO MUCH to learn in order to understand HP, LP, and crossovers, I know, and I appreciate how there is so much to explain. Thank you for trying. I will read all the replies carefully, and check out the links, to try to understand. Thank you basicxj and nauc for all that.

For now, it sounds like turning down the HP has balanced the mids to offset tweeter output, as you said basicxj. So, if it's possible to explain it accurately in such simple terms, does lowering the HP crossover mean lower signals or frequencies are now being sent to the mids instead of the tweeters? Is that how the mids are better balanced to offset the tweeters, but then maybe that only happens with component speakers running active? I realize, though, that my questions and thinking might be too simple. Sorry if that's what I'm doing.
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Old 11-20-2015, 12:54 PM   #6
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Quote:
Originally Posted by SQ+ View Post
There is SO MUCH to learn in order to understand HP, LP, and crossovers, I know, and I appreciate how there is so much to explain. Thank you for trying. I will read all the replies carefully, and check out the links, to try to understand. Thank you basicxj and nauc for all that.

For now, it sounds like turning down the HP has balanced the mids to offset tweeter output, as you said basicxj. So, if it's possible to explain it accurately in such simple terms, does lowering the HP crossover mean lower signals or frequencies are now being sent to the mids instead of the tweeters? Is that how the mids are better balanced to offset the tweeters, but then maybe that only happens with component speakers running active? I realize, though, that my questions and thinking might be too simple. Sorry if that's what I'm doing.
Running a high pass filter on the coaxials set at 100hz means frequencies below 100hz get rolled off and only a fraction get through with more being rolled off as you go down in octave. Lowering that high pass to 60hz means more midbass energy gets through to the mid (and the tweeters are unaffected, as they already have a high pass filter of sorts acting on them and dividing frequencies between the tweeter and mid).
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Old 11-20-2015, 01:14 PM   #7
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So the tweeters become less harsh (A LOT less harsh), even with loud volume, because lowering HP to 60hz sends more energy to the mids, without actually changing the input the tweeters themselves receive.

I'm looking forward to checking out those links you guys posted. It's great to start to understand something that has been confusing.
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Old 11-20-2015, 04:34 PM   #8
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SQ+ where are the "GAIN" knobs set on your amp and did you change them at all in the process of debugging your harsh tweeter situation?

I have a hard time believing that only lowering the HP xover freq made a *drastic* improvement in tweeter harshness. I agree with others that mid-high blend would be improved, but it seems like you are saying your high frequencies also became less distorted at high volumes.
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Old 11-20-2015, 06:30 PM   #9
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Yes, jepalan, it does seem strange, I know, but that's how it seems to be. I changed the switch from Off to HP, turned down the crossover from 100hz to 50hz (I thought it was 60hz now, but it's actually 50hz), and now the treble is safe for my ears. I'm not sure if it was distorted before, but maybe it was. What I notice now is that the treble is not piercing anymore, no more grimacing from the highest notes, and I can hear the rest of the music much better now that the air is not so full of treble. It sounds really good, actually, especially compared to before.

Here is what the OM says, "Set to the HP position when the amplifier
is used to drive a tweeter/midrange system. The frequencies below the crossover point will be attenuated at 12 dB/octave." What do they mean by "attenuated at 12 db/octave?"

I checked the Gain settings, front and rear, as you asked. They are both between 10 o'clock and 11 o'clock (the only markings show "NOM" at 12 o'clock, and 0.5V at 1 o'clock). I think that is where the shop guy set them when he did the install. I did not touch them before, during, or after I adjusted the crossover.

If necessary, I could go to a car stereo shop, ask the guy to check it out, and then let you guys know what he says.

Last edited by SQ+; 11-20-2015 at 06:41 PM.
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Old 11-20-2015, 07:59 PM   #10
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Quote:
Originally Posted by SQ+ View Post
Yes, jepalan, it does seem strange, I know, but that's how it seems to be. I changed the switch from Off to HP, turned down the crossover from 100hz to 50hz (I thought it was 60hz now, but it's actually 50hz), and now the treble is safe for my ears. I'm not sure if it was distorted before, but maybe it was. What I notice now is that the treble is not piercing anymore, no more grimacing from the highest notes, and I can hear the rest of the music much better now that the air is not so full of treble. It sounds really good, actually, especially compared to before.

Here is what the OM says, "Set to the HP position when the amplifier
is used to drive a tweeter/midrange system. The frequencies below the crossover point will be attenuated at 12 dB/octave." What do they mean by "attenuated at 12 db/octave?"

I checked the Gain settings, front and rear, as you asked. They are both between 10 o'clock and 11 o'clock (the only markings show "NOM" at 12 o'clock, and 0.5V at 1 o'clock). I think that is where the shop guy set them when he did the install. I did not touch them before, during, or after I adjusted the crossover.

If necessary, I could go to a car stereo shop, ask the guy to check it out, and then let you guys know what he says.
What model head-unit do you have?
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Old 11-20-2015, 11:39 PM   #11
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HU is Kenwood KDC-MP345U

http://www.kenwoodusa.com/Car_Entert...ent/KDC-MP345U
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Old 11-21-2015, 11:14 AM   #12
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Quote:
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OK. Your gains seem about right. Your amp gain range covers input levels from 4v (min gain) to 0.2v (max gain). The center detent labelled "nom" is 1v. So having the gains just to left of nom around the 10'oclock position *seems* about right because your head-unit has 2v RCA preouts.

Go with what sounds good for now.
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