Switching from Alpine Type R Subwoofer box to a custom fiberglass box

[VesperZ]

Just an overview of my current setup, I have 2 x SWR-1242D subwoofers which came with their factory designed ported box shown below:


I am looking to change them into a custom fiberglass sealed box such as this one:



I realize I may get questions like why would you bother and so forth, well reason is because I want my boot space back and this is the most viable option. My current boxes are currently taking up about 3/4 of my boot space which leaves basically no usable room whatsoever. My inquiry is whether this will be sufficient for my subs or will I simply lose the potential of my subs by putting them into these boxes. All I know about these fiberglass boxes is that the volume is 31 litres.

From the specs for the sub, the optimum sealed volume range is between 0.7-1.0ft cubed. I don't understand how to measure volume, especially when it's converting from litres so any help is appreciated. Feel free to post your suggestions also. My main concern is boot space so any solution for this would also be appreciated.

[holdenboy]

31 litres is 1.09 cu.ft. So they will be fine in those enclosures.

You will loose some output as you are going from ported to sealed, just keep that into consideration. Otherwise i cant really see a problem.

[VesperZ]

31 litres is 1.09 cu.ft. So they will be fine in those enclosures.

You will loose some output as you are going from ported to sealed, just keep that into consideration. Otherwise i cant really see a problem.

Thanks for that. When you say I will lose output, are you referring to how deep the bass I'm going to get or overall power? I'm not actually using the full potential of these subs at the moment as I'm only powering them with a 600wrms amp. These subs are rated to 500wrms each. At some stage in the future I will upgrade my amp, but at this stage space is the concern.

[HCVP]

Alpine must have been having a shit break when they listed the enclosure spec's for the Type R 12.I've tried them in 1.2, 2.0, and 2.5 cu ft. 2.0 cu ft offered the best allround performance, the larger 2.5 was able to play lower, but it's point to point excursion was no where near as quick. The 1.2 cu ft enclosure was dismal, to say the least.

Also, ported enclosure's are more efficient, so there's the efficiency loss associated with using a sealed enclosure aswell. Only having a 600rms amp, i'd be just running one sub, until you can afford to upgrade the amp, to minimise the chances of clipping the subs.

[VesperZ]

Alpine must have been having a shit break when they listed the enclosure spec's for the Type R 12.I've tried them in 1.2, 2.0, and 2.5 cu ft. 2.0 cu ft offered the best allround performance, the larger 2.5 was able to play lower, but it's point to point excursion was no where near as quick. The 1.2 cu ft enclosure was dismal, to say the least.

Also, ported enclosure's are more efficient, so there's the efficiency loss associated with using a sealed enclosure aswell. Only having a 600rms amp, i'd be just running one sub, until you can afford to upgrade the amp, to minimise the chances of clipping the subs.

Totally understand where your coming from, but when you have a never ending battle against quality of sound and boot space then sacrifices must be made. I did at one stage have only 1 sub going, but for some reason it seems to sound better with the 2, so I left it in.

[holdenboy]

Yeah HCVP most manufacturers state the smallest sealed enclosure that the sub sounds acceptable in.

HOLD3N, It'll be almost be a totally different "type" of bass. Much more punchier and tight. The lows (<30hz) wont be as prominent, but if you dont listen to alot of drum n bass, rap, RnB etc and more rock, metal, pop etc then you'll be fine.

[VesperZ]

Excellent, that's great news since I typically listen to Rock, Metal and so forth. Thanks for your help holdenboy

[HCVP]

QUOTE- I did at one stage have only 1 sub going, but for some reason it seems to sound better with the 2, so I left it in.

Running 2 would have lowered the impedance level to your amp, meaning it was putting out more power.

[VesperZ]

Well that would explain it then :P

[BLK VT]

This is of late reply but i was wondering if you had much luck with these? i figure by now you have done the mods, and are possibly happy with it?
i was also wondering where you get those enclosures from and a rough price for them? thanks.

[VesperZ]

Funny you mention I just finished it this weekend. I built the enclosures myself using the calculations Alpine suggested. To put it simply... it is satisfactory, I much prefer Alpine's ported boxes over these ones but when space in the boot is a concern then there's no other choice. I am running mine with the absolute minimum amount of volume suggested from Alpine's website then calculated the minimum dimensions required. I also used poly-fill to give the sub the effect of treating it as bigger box than it really is. Hope this helps.

[HCVP]

It's that minuimum amount of internal volume that is effecting their performance.

Going form ported to sealed can reduce the overall output, but a well designed sealed enclosure should not dissapoint in terms of output, if it was the case then you would need at the subs and amps themselves.

Based on 31 litres, if you still went by that, that is 1.09 cu ft, which is just about the same as the smallest out of the 3 i built and tested for the Type R at 1.2 cu ft. This was the enclosure that i mentioned above about having the worst performance out of the 3.


Poly fill is good for reducing rear standing waves in sealed enclosures, but i don't beleive that it can trick the driver into thinking it's playing in a larger enclosure.