Crossover Point Help

[jsampsell 10+ year member]

I've done a lot of research on this topic and have learned a lot but I'm still a little unsure of how to set the front and rear crossover points. Sub is fairly straight forward.

I've got an Infinity Reference 5350a 5-channel amp that I am running a Pioneer AVH-P4200DVD. I've got the front, rear and sub signal wires hooked up to the amp and of course four speakers and the subs. The door speakers I have are JL Audio TR570-CXi 3-way full range speakers. Their frequency range is stated at 53Hz-22KHz according to JL's website. The front and rear amp inputs have a crossover range of 32Hz-320Hz. The amp also has crossover mode switches for both the front and rear inputs: LPF, Full Range and HPF.

I'm currently running my sub input at 80Hz.

I'd like to use the front speakers as a high stage and the rear speakers as a mid stage even though all four speakers are full range speakers. I may be viewed as stupid for wanting to do this but the thought had crossed my mind that if the amp gives you the ability to crossover the front and rear separately as this amp does, why can't you cross the fronts at a higher point and the rears at a lower point to accomplish this? Is this possible? Is this crazy? Should I not even bother with doing this?

What recommendations do you folks have for me? I realize that the end result will be based on my personal listening tastes but there's got to be some norms. Maybe not. Either way I'm just looking for some advice.

Thanks in advance,

Jeremy

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[T3mpest 10+ year member]

If you want to use the rears as midbass that's fine. It may help make your subbass to midbass transition at little better. I'd run a lpf at 200hz or so. Depends how steep the slope is. Play just the rears and you want to filter out the rears so you don't get much of the vocal region coming through. You'll get some no matter what. Try listening to just a voice on the radio and listen and a make sure it still sounds like it's just coming mostly from up front. You'll still get reinforment near 80hz where the sub comes in, so it'll help.

 

[jsampsell 10+ year member]

T3mpest - Cool, thanks for the suggestion. I wouldn't have thought about running a lpf on the rears at a higher crossover point but that makes sense. I'll try that tomorrow.

I originally said that the sub was straight forward but I have a question about it after all. On this HU the sub settings have lpf crossover points that you can't turn off. The hpf is a different setting outside of the sub settings obviously and you can choose to turn it off. If the lpf is set on the HU to filter the output signal at a certain crossover point then what do I set the amp sub crossover at?

 

[jsampsell 10+ year member]

By the way, what's a baller? Maybe that's a dumb question, but I'm curious about the quote in your signature. I seriously have never heard that term before.

 

[T3mpest 10+ year member]

lol it's a term rappers use. From urban dictionary:A thug that has "made it" to the big time. Originally refered ball players that made it out of the streets to make millions as a pro ball player, but now is used to describe any thug that is living large.

Anyway yeah, if you don't want the rears to detract from your fronts, but do want them for the extra cone area, then cross them over near 200hz. It'll give you more midbass that way. Anyway, you really only need one HPF, I'd use the HU's since you can adjust it on the fly. If you find that you are getting too much upper bass from the back though, you can active both filters to get an even steeper slope than one could give you alone. If your only need one just use the hu though.

 

[jsampsell 10+ year member]

So let me ask it from a signal flow perspective relative to where the HPFs and LPFs are.

From the source, the HU, the signal for the front and rear channels can be run through an HPF at different frequency points OR it can be turned off allowing the signal to run straight through. Also at the HU, there is a setting to change the rear channel speaker type from full range to subwoofer. In addition, at the source, the subwoofer option has to be turned on to begin outputting the sub signal and the sub settings have a crossover that can not be turned off.

Then at the amp, for both front and rear, there is a crossover mode (LPF, Full Range, HPF) and a crossover frequency range adjustment. And for the sub there is just the crossover frequency adjustment.

I can understand why it would be nice to use the HPF of the HU since adjustments to it are much easier than stopping the car and popping the trunk to adjust the amp's HPF settings. BUT, if you set the HPF at the source, what do you do with the settings at the amp? You can't bypass them. So do you set them at the highest frequency point so that the range that is actually being allowed through the HPF of the HU is allowed to come through? I hope this makes sense. In a single HPF situation you would just adjust it for what you need but in the case where the signal can be modified from the source but it is forced through another filter at the amp before it gets to the speakers, how do you set the amp's HPF in order to let what you choosing to send from the HU actually get through to the speakers? In this case, since the HU HPF can be turned off, thus sending out a full signal to the amp, it would make more sense to use the amp's HPF since I can't turn it off if I wanted to.

The same thing applies to the sub channel. In this case, the source signal is sent through an LPF by default. So, if I set the HU LPF to send out at 80Hz, what do I set the amp's crossover point at?

Do you see my dilema? I'm not quite sure how to get the signal I want through both the HU filters and the amp's filters. The fact that you can turn off the HU's HPF is a way to eliminate the problem with the front and rear channels but since the LPF on the HU can't be turned off, what do I do?

Another way to put it: If the source signal is, let's use the frequency range that my door speakers are suppose to be able to handle, 53Hz to 22KHz and I want to send the entire signal to the amp where I can then set an HPF on the fronts crossed at 320Hz and the rears an LPF crossed at ~200Hz that would mean that the signal getting through to the front speakers would be anything above 320Hz and the rear speakers would get everything below 200Hz.

The sub channel is slightly different. I'm not exactly sure the frequency response is for my subs but let's use the frequency range that the amp's crossover adjustment allows which is 20Hz to 200Hz. If I understand this correctly, since the HU has to use an LPF on the source signal just to be able to send out only low frequencies over the sub channel so I understand why it can't be turned off. In essence, by turning the sub channel on you are actually turning the LPF on. If I set the HU LPF crossover point at it's highest which is 125Hz, that's going to send everything below 125Hz through to the amp. So if I can send the widest frequency range through to the amp's sub crossover and I want to limit what gets through to the speakers themselves, I would then use the amp's crossover at say 80Hz which would then only allow frequencies below 80Hz through to the speakers. Is that correct?

Anyhow, this reply isn't directed specificly toward you T3mpest but if you understand what I'm saying it sounds like you know your stuff so I'd appreciate any enlightenment on this. I'm not quite a newbie but I'm not quite a pro either. Understanding how to install audio equipment is only half of the equation and I've got that down pretty well. It's just getting the final output to sound the best it can where I'm trying to figure all this stuff out. It doesn't help that I'm a trained musician either. I'm a little more picky than others usually are. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[jsampsell 10+ year member]

Another way of looking at this setup:

Frequency range from source signal: 20Hz to 22KHz

So, in the above scenario, that would mean that these are the ranges for each stage:

Front: 320Hz - 22KHz

Rear: 80Hz - 200Hz

Sub: 20Hz - 80Hz

Is this correct?