High Pass filter physics.. lost.

drevangabriel

Using a 2006/7 model RF Punch 400.4 in combination with four 6x9 3-way speakers.

I am very curious: if these speakers (according to specs) play only the freq's between 65-23000 Hz, then why would using the HP filter on my amplifier (50-500hz) make them sound so different? There is a noticeable decrease in bass. If the speakers wont even play anything below 65hz, in theory should not the attenuation of anything below 50hz not even make a difference? Please help me to understand the physics here.

Thanks!

arun1963

Your speakers recomended frequency range is 65hz to 23,000hz. This means that based on the cone material, surround, suspension, etc of your 6x9 speaker, it can optimally play the 65-23k range. It will reproduce sound in this range with clarity and without hurting itself.

You have not mentioned if your 6x9 have a crossover, if so the crossover would filter out the freq below 65hz. If the 6x9 do not have xovers then they will play all the frequencies that they are fed.

Sound waves are generated by the speaker cone moving air. The cone moves back and forth when fed a signal, thereby moving air. These waves hit your ear drums and get converted into sound. A 60hz signal would cause your cone to make 60 cycles. 1 forward movement + one backward movement of the cone = 1 cycle. Hence the 60hz signal would move the cone forward and backwards, 60 times per second. The physical distance the cone travels (forward and back) is the excursion. The excursion on a 60 hz signal is greater than that for a say 250hz signal. So if you played a 20hz signal thru your 6x9 cone you would be overextending the cone/surrond and eventually you would damage / destroy the cone / surround.

A sub woofer which plays the low frequencies say 15-80hz is geared for higher excursion and a tweeter which plays the highs is geared for minimal excursion but higher cycles (15,000 cycles for a 15khz signal). Hence the sub will have a larger cone and higher mass than the tweeter as the needs are different.

If you set the HPF on your amp to 60 hz, the amp would feed all signals 60 hz and above to your speakers and would filter out the signals below 60 hz. Hence you hear less bass when you use the HP. Does your HU allow you to set the HP if so you can set the HP from your hu and run it AP (all pass) from your amp.

Am not an expert by any means but I hope the above provides aome answers.

cadenceclipse

ahh, here we go..once again arun no. crossovers that come with speakers(not that it has anything to do with thread) only filter tweeters (high pass), and woofer lowpass, not high pass. which means a HPF on woofers is always highly desirable as without it, woofer will play down to freq HU puts out, usually about 10hz. also because specs say 63hz - ????? means nothing. u can buy a $50 pair of kenwoods that say 35-2????hz but i wouldn't recommend anything lower than 120hz w/ 6db slope on anything like that. they might be able to buzz at that freq. but if your expecting any sort of actual bass, ain't happening.
so there a couple reasons using HPF will make them sound so diff. its meant to make them sound a lot better. if much less bass (at least clean sounding) u can lower the filter to allow more freqs through. your amp proly has 12bd slope. 6db seems to me to be ideal for coaxials/components as it provides a more gentle slope allowing smoother blending into subs. i use 6db on HU and 12db on amp(amps usually have fixed slope)so if only using 12 db slope i'd try setting it at, wait what speakers u got? proly around 120hz maybe 100..

arun1963

dear cadence,

This is your second or third retort post, where you are reacting to something I posted. The tenor of all posts have been patronising and looks like u have blurred the line between personality and issues. Please don't personalise issues here. Feel free to pm me for any personal comments. Tks.

If you have an issue with the content of my post, if it is factually incorrect pls feel free to correct me. While on this, the guy asked a question and I provided the facts. He didn't mention anything about a sub, I did. If you read my post the mention of the sub has a context. I also didn't assume that he has $50 6x9 (maybe he has), I just talked about the theory.

Also, two guys bickering in front of the op is not the best publicity for this forum.

cadenceclipse

dear retort,

the only issue is your facts r not real facts. evrybody loves to hear your 2 cents believe me. its nice your interested i really do respect that, also u seem like u like to help, also respectable. honestly man i know u come from the opposite side of the world but things can't be that much diff. maybe this is my 2nd or 3rd time putting u in your place but its also bout the 4th or 5th time u misled some1. i know u have some useful info to share and by all means its great. u just go 2 far sometimes. if u r not sure its ok thats what this forum is for. but blabbing out your completely wrong thoughts doesn't help any1. in this case like i mentioned passive crossovers do not have HPF on woofers...tart whats the op

arun1963

Wanted to reply to your post yesterday, but it was at the absolute bottom of my priority list and by the time I got around to it, it was late and i was tired.

like i mentioned passive crossovers do not have HPF on woofers

Yes that was a mistake, I should have scanned the post.

maybe this is my 2nd or 3rd time putting u in your place

ummm..... ok, if my posts are so screwed up how come none of experts / gurus here have thought it fit to slam me / put me in my place? The answer to this is given in the last para of this post. Sure, Mac has corrected me a few times, but he's done it in his inimmitable way and the msg has gotten across without any affront. I have never denied that I am at the begining of my learning curve and as such will make some mistakes along the way. You are riding the same curve. It's always best to keep the gap between where you think you are and where you actually are as narrow as possible. Not more than 5mm, anything more than that causes sibillance.(since you need absolute numbers and you have sensitive ears. ).

I have thus far refrained from making personal comments on your posts, but the fact is that your posts lack coherence most of the times (Since you may struggle with the concept of "most of the time" lets say 70% of your posts).

It seems that half of what you want to say stays in your mind and the other half is posted. Very few if any, of us are mind readers. Try re-reading some of your posts objectively. IE read the post for what you have written, without connecting it to what your thought stream was at that point. Here is an example taken from another thread:

yeah we know
u match input voltage when maxing out HU volume. i always kept amp gains alll the way down to 8-9v. HU 8v preout. makes sense right? i also always maxed out volume(almost) 79 out of 80. just recently changed to 55 out of 80 and turned up gains bout half way. so yeah, 80% works pretty well

Ok, so keeping your amp gains down all the way down at 8-9v means your amp goes from 8v-15v? IE 8v is the lowest since its at the "all the way down position". But no hang on, according to the cadence website, if you had the gains on min it would be at 200mv and 9v is the max, ......... U drove your hu at max volume and it didnt strike you earlier that your amp gain setting was out.....ok.

Here's another gem.

thanx mac. only issue is "down a tad" which seems like the common answer or phrase only just a bit too vague for me. guess the average joe listener can back up a tad (or not) and be happy or not even notice the difference. i know i have a sensitive ear but i also know the smallest tad seems to make quite a difference. as i was saying(or maybe meant to but my computer keeps freezing when i hit "submit reply". extemely annoying, but i keep trying) can't wait till amps have digital filters(actually mine does) but where u can set filter digitally to any freq. u know like HU but ANY freq. turning the nob seems rather old school ya know? how bout your processor mac. imagine thats not digital eh?

Also, pls stop siddling upto Mac to try and get him in your corner. More than anything, it shows a lack of respect for someone who is way ahead of you and me in content. and it shows your insecurity.

What I find amazing about this forum that 95% of the experts / guru's et al have a few common traits:

1. They are all rich in content and experience. - Content
2. They realise that acquiring knowledge is about using it for their needs and spreading it to those who want to learn . - Responsibility
3. They dont need to prove to anyone that they 'know'. Least of all to noobs like u n me. They dont need to slam anyone, unless ofcourse the noob happens to be a PITA. - Great Attitude.

If you have 1&2 but lack 3 you'll struggle, both here and in real life. Thanks to your short attention span, I think youre lost by now, So before u accuse me of blabbering, let me encapsulate the above:


1. If you live in a glass house dont chuck stones

2. Take a deep breath and calm that mind of yours. Greater Coherence.

3. The right attitude goes a long way.

Between this post and the last one I have said all I wanted to say. I expect your response will be along predictable lines, but I'm not going to take this any further.

cadenceclipse

you will never b able to predict my response dude not in a million yrs. there is no comparing u and i. every1 knows your a noob (and a boob) cause u prove your lack of well lots of things in about every post. 9v is min. 200mv max. don't know bout your side of the world, but i ain't tryin to figure it out. my posts may not be spelled out to a preschooler i'll b the 1st to admit but at least i don't tell my life story in every damn post. how u doin there drevin got it all figured out?

arun1963

I have been on this forum for a year and a half. Whatever little I know, I have learnt here. I don't want to get into scraps. I'm here to learn thats all.

The above is not me by nature. The above post is out of line in itsc content and out of place on a public forum.

Cadence, lets just agree to disagree and lets not needle each other.

cadenceclipse

i don't think so. don't u see thats the issue here. i got no problem with any1 giving recommendations or sharing thoughts. the only things we(I) disagree on r when some1 who gives advice evryday like myself is giving bad advice and wrong info, just makes it more difficult for myself and any1 else who wants to help and spread the wealth. arun like i think i said b4 i really do look up 2 u or any1 who is that interested to spread the knowlege. i think its great that u share lots of stuff here. but come on man.. enough assuming theres plenty of help here including myself. if not sure let us know. no one will bash u (unless u keep filling these thread with BS) i gotta work..

howie777

A high pass filter will knock out any frequencies below its setting. So if your high pass filter is selectable between 50-500 Hz, and you set it to say, 120 Hz you just lost everything below 120 Hz, and now have very little bass.

Check to make sure you actually set to it 50Hz and not above 120 Hz try again.

If it was a band pass filter, it would knock off anything below 50Hz and everything above 500 Hz. I only bring this up to point out 50Hz - 500 Hz on a high pass suggests a selection must be made. While a bandpass of 50-500Hz indicates a fixed filter with no option to pick the roll off frequencies. So based on your post I am assuming it is a high pass where you need to set the roll off frequency.

Howie

cadenceclipse

wrong-o (buk-o) howie. depending on slope, set at 120, u could be getting down to 80hz. this has been a bit of a confusing thread but throwing "bandpas" in the mix sure stirs it up a bit. wouldn't u need 2 filters for that

howie777

ugh.

There is nothing wrong with my post. Ignoring slope as it doesn't need to be included to answer his question is fine. So no I'm not wrong, I just didn't explain every single detail about filters and how they work. So assume, when the roll off is 120Hz, you get nothing below this value. Then it becomes easier to understand how he could have lost the bass by adding a high pass filter into the system in question.

Forget I said band pass - shouldn't have clouded the issue. And it is simply a filter with two roll off points, one made using a low pass and one made using a high pass. You would use it for a mid bass in a 3 way configuration if at all.

Speaker 65 - 23,000 Hz.
High Pass set to 120 Hz
Frequencies sent to speakers 120 Hz and up. Not much bass at all

Speaker 65 - 23,000 Hz.
High Pass set to 50 Hz
Frequencies sent to speakers 50 Hz and up. All th bass your speakers can handle

Speaker 65 - 23,000 Hz.
High Pass set to 500 Hz
Frequencies sent to speakers 500 Hz and up. No bass at all.

Does that help?

Howie

cadenceclipse

ugh haha dont get frustrated :rolleyes:

no

drevangabriel

i pretty well understand what slope and cut-off and filters are/do.

back to the original question- my speakers are said to be in the range of 65-23k. i've been told by one member that this is a "recommended range" and i've come to believe this is false, that this is the actually the range that the speakers will effectively produce an audible sound. so, anyone with technical knowledge of speakers (as in someone who makes them or uses them scientifically): even if my speaker is stated as starting at the 65hz mark, will it produce sound below 65hz? so far i believe this is not the case.

now, back to the filter.. *IF* my speakers do not even play ANYTHING under 65hz (this is why question one is so important), then attenuating/altering/removing ANYTHING UNDER 65hz in theory should not affect playback. so-

**"black hole"** |65<

---

>23k| **"black hole"**

changing the colors/sounds/size of anything in the "black hole" is irrelevent, theres nothing there anyway, dig? i tried setting my filter to 65hz, and it DOES change the sound. so its not really "all the base my speakers can handle"..

now i think i may understand a little bit about whats going on, and so far no one has even hinted at it. just because my speakers wont PLAY anything under 65hz, doesn't mean they arent getting some kind of SIGNAL that they are in some way responding to.. i started wondering this when i read abotu sub-sonic filters. just because the sound isnt being produced (or even audible) doesnt mean its not affecting what you hear. but again...

cadenceclipse

65-23000 means absolutely nothiing in my book man. like i said dunno what speakers your even talking about but $30 jensens or kenwoods or anything can say they play from 30-30000hz. doesn't mean u want 2 hear freqs anywhere near that range. my eclipse components say something like 83-23000hz. i got my hpf on amp(12db) at about 200hz, also HU(6db)(HU only b/c 200 is as low as it goes in 3way mode)
they will def get some SIGNAL whereever its set. HPF is basucally same as subsonic. for subs u set subsonic same way and reason u set HPF on mids(for example). which is for maximum speaker performance. just cause u can't even hear below 25hz (for example) doesn't mean setting subsonic at 20 won't b different than 25. u don't set any filter for any reason other than thats the way it sounds best. if your 6x9s sound best at 65 or 35hz by all means keep it there. i'm willing to bet though if u turned up the HPF they will sound better meaning clearer, louder and tighter (and more)bass. if u want more buzz and distortion i'm sure you could just keep em at 65. on the ohter hand i hear mac and others talking about 35hx on polk components or something..that i just can't imagine. i believe it, must be sik, but i also don't think your talking about $800 polks

arun1963

back to the original question- my speakers are said to be in the range of 65-23k. i've been told by one member that this is a "recommended range" and i've come to believe this is false, that this is the actually the range that the speakers will effectively produce an audible sound. so, anyone with technical knowledge of speakers (as in someone who makes them or uses them scientifically): even if my speaker is stated as starting at the 65hz mark, will it produce sound below 65hz? so far i believe this is not the case.

1. It would help if we knew make and model of the speakers you are running.

2. There is a BIG difference between a speaker being able to "play" a frequency (i.e. that freq will vibrate the speaker and hence produce a sound) and the speaker playing the said frequency 'with clarity'. Just beacuse your speakers are rated to vibrate at 65hz doesnt mean they are clear at 65hz. Cadence is talking about the clarity bit. Good speaker brands define the freq range based on 'clarity of sound and the physical limits of the speaker". The cheaper brands define the range based on freq which will 'vibrate' the cone. Same thing applies to amps. The better brands will sell amps based on rms watts the cheaper ones will sell based on peak power.

3. If u do not use a hpf from your hu/amp and thus run the full signal from your hu to speakers, the speakers will get frequency below 65hz as long as they are there in the music. This will cause the speaker to move, but how accurately is another issue. Your original post mentions exactly this. When u disengage the HPF you hear more bass.

**"black hole"** |65<

---

>23k| **"black hole"**

If you were to set your HPF to 63 (most hu's where you can selct xover point offer 63 not 65) The black hole would be below 40. Based on an avg slope of 12db/oct your speakers would be seeing a low of around 35-40 but at lower db's. With 90% of mids you need a sub to play the freq below 50hz clearly. Now to the other end. The std measure for human hearing is 20-20,000hz. You would'nt hear anything above this in any case.

This is the theory. If you are using stock / cheaper speakers, just set the hp xover at 100-125hz range. If you feel u need more bass, either buy better speakers or add a sub.

On my polk momo's which are good speakers(the sr's are much better), I have the mids on cascading HPF at 63hz (i.e. 63hz hpf from HU @ 12db slope and amp @ 12 db slope hence a combined slope of 24db/oct) and they are crystal clear. My sub cuts of at 50hz on lpf. I can run the momo mids down to 50 hz with equal clarity. The reason I don't is cause I want to keep a slight seperation between my sub and mids. Polk lists the freq range for the momo's at 43hz-25,000hz.

Hope u get the picture now.

dirthog

I didn't read any of the other posts, lost interest in the battle.

As for it being the recommend range, I would say false. Look at the white papers to see where the drop off starts. I wouldn't even say effectively plays that range. At 63Hz it's output is not the same as higher frequencies.

Just like you stated. Without a HPF the speaker is still getting all of the information below 63hz and it tries to reproduce it, but it's not capable of doing so. Due to smaller cone surface area, shorter xmax and what not. When it's not trying to play those frequencies it allows the speaker to more be linear.

I'm not too sure why you notice such a difference in bass. Did you notice an improvement in clarity?

The difference could be the crossover on your amp is not that accurate especially if it's the knob style.

Another thing is what slope and crossover network is it using. When you have your crossover set at 80hz with let's say a 6db slope it doesn't start attenuating at 80hz. It starts at a higher frequency and the steeper the slope the closer the crossover starts attenuating at the selected frequency.


What speakers are you using?