Fibergalss vs mdf sub enclosure, ported vs sealed...

Vital

Looking into getting rid of my Polk BD 12'' in polk's ported enclosure and getting Polk SR 12''.
Current Polk PA600.1 mono amp (400 rms @ 2 ohms) will also be replaced with PA1200.1 (800 rms @ 2ohms) to properly power up SR12''

Will start practicing fiberglass enclosures to build fg sealed box for SR to fit it on the side of the trunk - main reason is to save space in the trunk and finally get a chance to make it look good with all those amps, wires and x-overs. BD sub sounds good but having that huge DB ported box is in a way of everything and there's not much i can do about it short of replacing it.

SO...
2 question for now, u can bet there'll be lots more as we go along haha.

1 - with this sub and sub box swap i'll be going from 360 rms in ported to 700 rms in sealed. We all know that all things equal ported is louder then sealed. Question is What should i expect SPL-wise from this swap? 700rms is basically double of 360rms but we'll have to subtract enclosure effect.

2 - all thing equal - how is fiberglass comparing to mdf when it comes to weight?
Yes, i know, it's very subjective question but let's say we have the same 10x10x10 box out of mdf and 10x10x10 box out of fiberglass - which one is heavier???

catch22atplay

Not sure which box you're talking about. But comparing a DB12 in a vented enclosure at 1.5cu ft with 360w rms vs an SR124 in a 1.5cu ft sealed box with 700w rms. I'll compare them but i don't know what the DB port is tuned to. So listing a few examples.

DB port tuning at 30hz
DB +1db at 45hz
break even point=24hz
SR >+6db per octave below 24hz

DB port tuning at 35hz
DB +2db at 45hz
break even point=31hz
SR >+6db per octave below 31hz

DB port tuning at 40hz
DB +3db at 55hz
break even point=36hz
SR >+6db per octave below 36hz

DB port tuning at 45hz
DB +4db at 58hz
break even point=41hz
SR >+6db per octave below 41hz

Least that's what WinISD shows. Approximate values.

As for which box is heavier i've no idea.

chu

Vital wrote: »

Looking into getting rid of my Polk BD 12'' in polk's ported enclosure and getting Polk SR 12''.
Current Polk PA600.1 mono amp (400 rms @ 2 ohms) will also be replaced with PA1200.1 (800 rms @ 2ohms) to properly power up SR12''

Will start practicing fiberglass enclosures to build fg sealed box for SR to fit it on the side of the trunk - main reason is to save space in the trunk and finally get a chance to make it look good with all those amps, wires and x-overs. BD sub sounds good but having that huge DB ported box is in a way of everything and there's not much i can do about it short of replacing it.

SO...
2 question for now, u can bet there'll be lots more as we go along haha.

1 - with this sub and sub box swap i'll be going from 360 rms in ported to 700 rms in sealed. We all know that all things equal ported is louder then sealed. Question is What should i expect SPL-wise from this swap? 700rms is basically double of 360rms but we'll have to subtract enclosure effect.

2 - all thing equal - how is fiberglass comparing to mdf when it comes to weight?
Yes, i know, it's very subjective question but let's say we have the same 10x10x10 box out of mdf and 10x10x10 box out of fiberglass - which one is heavier???

1. You should expect the same amount of output when you double the power in a sealed enclosure. But if you were to double the amount in a ported enclosure, the ported will be louder obviously. 3db gain isn't much anyways.

2. mdf is heavier.

arun1963

Doubling power increases the sound level by about 3db. You would lose a part of this by going sealed. The real difference though will be in the presentation of the sub bass. Typically, the sub in a ported box would give you a 'kick' due to a peak somewhere around the 30-40hz mark depending on various factors including the box and the port.

The sealed sub would would not give you this peak. The sub bass would be more linear and tighter. But chances are your first reaction would be to feel a loss of this peak. Hang in there and let your ears get used to the new sound. Will take a couple of weeks.

Vital

Thank you for all replies guys.

catch22atplay wrote: »

Not sure which box you're talking about.

Polk Audio DB1212, have no idea what it's tunned to.

catch22atplay wrote: »

DB port tuning at 30hz
DB +1db at 45hz
break even point=24hz
SR >+6db per octave below 24hz

DB port tuning at 35hz
DB +2db at 45hz
break even point=31hz
SR >+6db per octave below 31hz

DB port tuning at 40hz
DB +3db at 55hz
break even point=36hz
SR >+6db per octave below 36hz

DB port tuning at 45hz
DB +4db at 58hz
break even point=41hz
SR >+6db per octave below 41hz

Least that's what WinISD shows. Approximate values.

to be honest i have no idea what it all means lol.

DSkip wrote: »

Why is the weight important? The biggest increase in weight will be going to the SR driver. It's a beast at 25-27 lbs, depending on the 10" or 12"

It's not the most important thing, i'll go for it even if fiberglass was a LOT heavier, it's just for my own "good to know" info.

arun1963 wrote: »

chances are your first reaction would be to feel a loss of this peak. Hang in there and let your ears get used to the new sound. Will take a couple of weeks.

Just what i want.

tk421

the FG is lighter. a 12" SR should be housed in a strong encl. built of and braced with 1" MDF. or HDF if u could find/afford/lift.

the FG encl is good for irregularly shaped location and for saving weight. but this does not mean that the FG encl is gonna be 1/2 the weight. you need to add a lot of layers to get a strong, vibration free encl. there are different weights in FG cloth/mat. i've found that the best to work with is the woven-roven (aka mat + woven FG). there are different weights. i like the lighter one as it is more flexible.

FG tips - build the first 2 layers in the car (following one of the many FG how-to's online). allow to dry completely, remove and then build up the other 6 - 10 layers outside the car (and outdoors!). buy the FG roller. buy an auto-painters full jumpsuit, googles, chemical mask and medium-tough rubber gloves or a lot of medical examination gloves.

avoid bubbles! use the FG roller and a nail for this.

allow to dry. trim, sand, smooth ... filler .. paint or carpet.

brace between the FG backing and the speaker mounting surface very very well. the speaker mounting surface should be at least 1" thick MDF or HDF. seal any and all leaks. test on your workbench; listening for leaks.

oh ;-) .. insider tip ... mdf is porous. paint the inner side of your mdf with FG resin. allow to dry etc. a leak SQ box is a bad thing.