hpf and lpf, which setting?

hi guys,

i have a pioneer deh-p80mp.(pretty and pretty good unit)

i have also 2 sets of jbl p6550c comps and 2 jbl gt4-12 woofers.the question i need to ask as i am clueless is this,i need to know what hpf setting/level i need to set my headunit at and i also need to know which lpf setting/level to set my headunit at.i have the option on both hpf and lpf of 50,80 and 120,so which do i choose for each filter?

any help would be great,

cheers,

dave.

The setting will be the same for both.  If 80 Hz and below go to the subs with the LP, then 80 Hz and above will go to the components using the HP.  You want neither an overlap or a hole in the crossover, which means the number must be the same for both. 

If the head unit can send the signals out full range, then the LP and HP settings on the amplifiers would be used.  80 is a good point for starters, 50 will be too low (the components mids wouldn't go there), and 120 may be a little too high for the subs (you'd start to get a sense of sound direction at that freq).  Normally, finer crossover adustments, and usually a better crossover slope for the subs, can be had by sending the signal out of the head unit at full range and using the filters on the respective amplifiers.  And the amps will give you more precision in setting crossovers for the two sets of components, as they will have a crossover for each set (as in if you are using a 4 channel amp to power them).

The crossovers on (that) head unit could be used if you're just doing a simple deck and/or speakers upgrade and no amplifiers are added.

hi stevdart,

well,i do have an amplifier and im running hp mode on the front and rear channels.i also have the headunit set at 80 for the hp,so i must see what i have the sub filter set at.i think its 120.

the 5th and 6th channels on my amp are set to "bandpass" for my 2 subs.

the amp is a rodek r680a 6channel amp,and i got it basically as a space saver or all in one jobbie.do you reccomend i get a small mono for the subs instead? the bass sounds terrible from my amp and not at all loud.or maybe i just have it set up wrong and i dont know which settings to choose.

yes,my headunit can send out full stereo,i just have to switch off the hpf.being honest,the sound of the car does not sound right at all.sounds like the comps are getting too much bass,and the subs are'nt getting it at all.

cheers for the reply mate.

The sub MUST be set on lowpass, not bandpass.  Bandpass setting is for an in-betweener...between the subs and the main components.  You don't have any need for that setting.  You should try to set sub and highs like I posted above.  Send the signal full-range, use the amp crossovers.  Or send the signal through the deck crossover, bypass the amp crossovers.  One or the other, but not both.

With 80 Hz as the crossover setting, the components have a hard time hitting it well.  But that is better than trying to push the subwoofer freq up to 100 or so because you get a misdirected stereo response in that critical range.  That range should be hitting hard from the front main speakers.

As important as the crossover settings is the preparation of the vehicle.  Damping in the front doors will bring out more detailed sound.  Right now it sounds like you are allowing too much low bass material to reach those front speakers and they are complaining.  Another factor is the subwoofer enclosure which must be built specifically for those subs and aimed right.  Damping, again, is a primary concern here, too.

The quality of the amplifier, too, will make or break the system.  It could be you are trying to get too much out of it (I'm not familiar with it).  Whether you upgrade your system depends on your ability to afford it, but powering subs with a mono amp is certainly a better way to go than using 5 & 6 on a 6 channel as long as the subs will wire to either 2 or 4 ohms.  With the 6 channel, you will have to have subs capable of being wired at no lower than 4 ohms.  (I didn't look up the specs on those subs).

hey man,

what i will do later,is take pics of the amp.mainly the side wall where all the switches and settings are.i will write up the spec's of the comps and also the woofer.i would do it now but my sister has my car.i will take pic's also of the headunit and the display it has for hpf and lpf.as for the amp and lp or bandpass switch,i dont think the amp has a setting for lp.i remember seeing hp and bp.i will check though when she gets in.if she ever gets in!! never lend a car to anyone else,they will muck it up further than you have.especially if its a woman.

cheers,

dave.

hey stev,

i managed to upload this pic.sorry it is very small.limit of 30kb on it.i think if you right click and save pic you may get a better view with a picture viewer.

my headunit has 3 pre-outs,front-rear-subwoofer and are 6.5volt jobbies.

jbl speaker spec:

comps- 4 ohms,90 watt rms,270 watt peak,sensitivity 90db,frequency response is 45hz-23khz

sub- 4 ohms,250 watt rms,1000 watt peak,sensitivity 93db,frequency response is 23hz-450hz

i have checked the control panel on the amp.no lp switch at all.there is however a knob which i can select the required lp.these are the same knobs which are used for the gain control.above in the pic you will see where i have added ink to make arrows in each section.where all the arrows point to,this is the way the amp came,and im wondering which direction all these arrows should be pointing to.

if you can make heads or tails from all of this you must be fairly good with your car audio.

any help would be great.thanks for the replies so far,

dave.

davemk7 wrote:

if this is no help,what site do i use to host the pic or if you want me to mail it to you i will.

That looks like a capable amplifier, very versatile.  The bandpass setting would be used for the subwoofer output.  HP allows passage of highs, or anything higher than the setting (of course, it "cuts" it off on a curve);  LP allows passage of lows.  So LP is used for the subs' high point and HP is used for the front and rear speakers' low points...AND the subs' low point.  (LP is not used for the front or rear speakers.)  The settings between the two should be the same:  i.e., if 80 Hz is used for the sub's LP, then 80 Hz should also be used for the main's HP. 

If the GT4s are housed in a sealed box, turn the HP as low as it will go.  If the subs reside in a ported box, you can use the HP setting as a subsonic filter and put it just below the box tuning frequency.  If the HP setting won't go as low as 30 Hz, then this amp is not suitable for driving subs.

The disadvantage with this amp/subs combo is that the subs are SVC 4 ohm, and so they will have to be series-wired to 8 ohms to bridge across channels 5 and 6.  This may be too little power for the impact you are looking for, so perhaps a mono amp (with the subs parallel-wired) would be a better way to go.

The phase/shift slider can be set to whichever way makes the subs sound louder with the rest of the system playing.  Experiment with that.

A test tone generator should be used to make a test CD if you don't already have one.  Set to 0 db using sine waves, you can make numerous tones to use in precise settings of gains and crossover points.  Make several tones 5 to 10 seconds long at and around the crossover settings, including the lowest for the subs.  In setting gains, the tones make hearing the clipping very easy.  And with all amplified car audio, well-damped doors and damped resonate sheet metal panels will improve the sound.