rear speakers in new box = bad bass

the past week or so in my off time i've been building some rear speaker box's for my 6.5's to set into, and this morning before work i got the chance to hook em up and test them. i was shocked basically, if anything i figured they'd sound somewhat better, but they were horrid. i had my amp set to LP on my rears for 'some' bass, and in my old box's they were sufficient, however in the new setup, i thought my left speaker was dead, there was very little bass if any coming from it, and the right was a very weird bass, on the upside i found the highs fine and sounded clean as usual.


i used 3/4 MDF for the entire box, and stuck weather stripping used on house doors around the top for a nice tight fit under the rear deck where the speaker box's mount under.
1 box really didnt have the best routing job where the speaker fits into so some gaps were left open, around the outter edge of the speaker itself,that speaker actually sounded better than the other, so i clued into the fact that they 'need' a free-air application.

now in no way do i want to return to the flimsy plastic stock box's, because i know the sub(s) i stick in the trunk will affect them in a negative way in the future, but im wandering if the following possibilities will give me any improvement.

First, i'd like to try some 1" poly fill on the inside of the box, i hear it actually creates more space in the box than is actually there, and i know it is used in subs, im wandering will this affect my speakers in a positive way at all?

Second, my last option i suppose, and the one i want to 'not' attempt unless a last resort, and that would be to create some holes in the box' maybe some fancy design that adds up to alot of open space created, but in general, just adding holes to the box.

will either option help?
any advice would be greatly appreciated,
sorry for rambling, had to be descriptive.

maybe a lil port through the deck to give them some air?  like a half inch pipe?

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2003 Chevy Avalanche,Eclipse CD7000,Morel Elate 5,Adire Extremis,Alpine PDX-4.150, 15" TC-3000, 2 Alpine PDX-1.1000, 470Amp HO Alt.

?poly fill will help but not how your thinking.. just play one at a time and see whats happening..

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dont be a pet monkey ..use your dmm

I woudn't suggest you make holes in the box unless it is "one" hole for the port like ALpine Guy mentions. Making many holes forming a design would make your speaker somewhat equivalent to putting it in the open or in a net.

I would presume from what you are saying that these boxes you made are a bit on the small side, possibly about the size of the original baffle that surrounded the OEM speakers.  Now, I would make these suggestions:

Find some data from the manufacturer of those speakers that supports using them in either a sealed or ported enclosure.  Find out if the maker means for them to be infinite baffle (or free air).  You could post up here what speakers they are, if there is no info to be found.

If the speakers are in the direct air space of your subs, and you want to place a baffle between them, look into making a larger baffle that would separate the rears from the rest of the trunk space.  Cars with trunks have a baffle that does the job.  Make something that imitates that type of baffle instead of enclosing each speaker.

I wouldn't try porting unless you use the T/S parameters and find out exactly what air space and port size you would need.  Guessing won't get you decent sound.  Also, cutting holes in the enclosure will have the effect of having no enclosure at all, and the subs will still interfere with the speakers.  No use having the boxes there at all.

And if the subs are not interfering with them, and you felt that they sounded good before you made these boxes, then consider going back to that setup.

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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

Generally, 6.5" car speakers are meant to be infinite baffle.  You probably built the box too small.  Try the polyfill, I bet it will help some.

If not, then try a larger baffle like stevdart recommended.

Stevdart is right:  don't port unless you know the parameters.

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New Project: 2003 Pathfinder

I don't understand why you are running these 6.5 inch speakers on LP

are they mid bass drivers?????????

did you mean high pass and set the high pass at a lower frequency???

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ELECTRONICS RUN OFF OF SMOKE, WHEN YOU LET THE SMOKE OUT THEY STOP WORKING

i have them set at lp because my setup is quite off at the moment

1) fronts are hooked to my deck, i dont want to over power them and have them blow before i have any replacable fronts. (they are stock)
2)no sub, my only real bass comes from my 6.5's and since i wanted some highs and not all coming from the rear, i set them to LP and try and give the front sound some added bass fill, the 2 speakers running 50/50 sound very off so i've had to fade it a lot to balance out the sound to my liking.
if i had my way and things were perfect i wouldnt have any need for any real bass from my 6.5's but thats not the case so im trying to accomadate the situation as best as possible

when i was saying holes, i wasnt really intending on a ported type hole, i was thinking something like a large enough hole on the side of the box which faces the rear seats, rather than the back of the trunk (where my subs would be) i will try the poly fill though first, hopefully it helps. but if anything, i cant used the box's if they arent working and will go back to what i had, so i may as well cut them because they will be too small. i will try a port as a last case scenario and play with hole sizes from around 1/2 to something that actually resembles or betters the baffles(or plastic box's as i was calling them) that came w/ the car.

thanks for the input guys, most appreciated.

btw, my speakers are Kicker K65's
https://kicker.com/images/manuals/02KSeriesCoaxmanual.pdf
thats the manual (as if it didnt spell it out -_-), very little information given, unless they hide the rest of the information on the backside of a pdf in an alternate language ;/

anyways, i cant have 'no' box in my car anyways, i just remembered, they bolt up into the bottom of the rear deck, so i could prolly create 2 templates to bolt up to it, but maybe we'll see.

i work with kicker speakers a lot and I don't think they give you enclosure sizes for the 6-1/2s : (

try the poly fil, ya never know

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ELECTRONICS RUN OFF OF SMOKE, WHEN YOU LET THE SMOKE OUT THEY STOP WORKING

in an ironic turning of events, a friend of my brothers was using out shope to re-appolster his arm rest for his truck, and he happened to have some polyfill, so i used it, and although it didnt make a huge different, the different was noticable, you could almost hear the speaker gasping for more air, so i removed the foam and stuck a couple holes into the box and its given it better bass already, but i wanna get a bigger bit, or etch out the design i was thinking of, 1 letter at a time to see if it needs more air each time i finish a letter. i checked the speaker holding it in the palm of my hand and it even sounded worse than within the stock box, god i dont know what i've gone through the trouble of making the box's they were fun to build, but the fact that i may end up with a skeleton of a box to even resemble working stock baffle, baffles me ;p

owell it'll chalk one up for experiance tips 40yrs from now -_- ;p