Grizzlee

Ok just as the subject states, I have 2 RFD1212 sub (12" punch HX2)

I built a box out of 3/4 mdf 40"x12.5"x8.5" it isn't glued together yet but I am starting to think that this box is TOO SMALL??? On the box the sub's came in it recommends 1.25 ft3 per sub I think I have around 2.45 not including (minus) the notch for the power hatch motor?

I also didn't realize that if I wire the sub in parrellel the ohms drop down to 1 ohm and I am not sure the Alpine 1505 V12 Expert can handle it??

I just roughly screwed the box together and placed the 2 sub on the top plate to see what it sounded like (wire in series = 4 ohms) and it doesn't sound that great? (leaking air right now) but it doesn't seem like it is going to pound??

Gummie

Don't worry a ton about box volume as the .25 cubes or so you're missing really isn't going to matter a lot.

Here are specs on the amp I found on google:

RMS Power (at 12V, 20Hz—20kHz)
Per channel into 4 ohms .................. 150W x 2 (0.08% THD)
Per channel into 2 ohms ....................... 300W x 2 (0.3% THD)
Bridged 4 ohms ........... 600W x 1 (0.3% THD)


RMS Power (at 14.4V, 20Hz—20kHz)
Per channel into 4 ohms .................... 225W x 2 (0.08% THD)
Per channel into 2 ohms ................... 450W x 2 (0.3% THD)
Bridged 4 ohms .................... 900W x 1 (0.3% THD)

How do you have your subs wired? It looks like the ideal situation would be bridging the amp to a 4 ohm load.

sub info

For what it is, it should get pretty loud, but you're under powering the subs. A bigger amp and/or an additional amp would defiantly make things louder. The problem with subs that are capable of handling high amounts of power is that they usually require large amounts of power to get loud.

Finish up the box, you will probably be surprised by the results. At that point if you don't like it your choices are a bigger amp or more efficent subs.

Also, be sure to use wood glue and/or silicon (preferably both) to seal up the box. If you don’t the thing will leak air like a sieve.

Grizzlee

Hey Gummie thanks for the reply I didn't realize that I wasn't that far off with the volume of the box.

I will take your word for it, I have to put the box/car on hold I worked up such a sweat making the box in my freezing garage that I got a cold

I was looking at the instructions that came with the amp and there is a switch on the amp that is (Low Impedance??)

Set to the "ON" position when a speaker with 1 ohm impedance (TOTAL) is used.
If the indicator becomes amber, decrease the volume on the head unit

Wouldn't this setting allow the amp to put out more power?

So I would bridge the amp in mono and then I would wire the speaker in parallel? Currently I have them wired to produce a 4 ohm load but I was thinking of going to a 1 ohm load?? Thoughts on this?

Gummie

I might have grabbed the wrong specs on the amp. Check to make sure that it really is stable at 1 ohm bridged before you go and try it. If it is stable at 1 ohm bridged then there's no harm in running it that way and you will certainty get more power out of it.

To get a 1 ohm load with your two 4 ohm dvc subs wire each sub's coils in parallel then wire the two subs in parallel with the amp.

As for box volume - sealed it really doesn't matter a whole lot. It's one of those things that gets fairly exaggerated in the car audio world. Bigger boxes really don't yield that large a gain in terms of output over smaller boxes and vice versa. Larger boxes will roll off sooner than a sealed box but the slope they roll off at is much more gradual, meaning that you can achieve more low frequency output than a sealed box after the two frequency graphs cross. Smaller sealed boxes will stay flat longer, so they will generally have a lower f3 (the point at which sound output is down 3 dB) – this is good. Once they start to roll off they will roll off a lot faster than a larger box. Also, if your box is too small then you will have a peak in output and then a really high/sharp roll off.

Note that that’s all about output. Boxes do two things: help control output and help control the motion of the cone. By this logic, smaller boxes will sound ‘punchier’ and larger boxes will sound ‘boomier’. This is because smaller boxes have a lot more control over the cone’s motion vs a larger box.

So how big a difference is there between a ‘large’ box and a small box? In terms of output, a pretty big gap – somewhere around 2 or 3 cubes at the minimal to get any kind of noticeable difference. In terms of sound I’ve got no idea honestly. You can’t really graph that but after a certain point it really doesn’t matter how big you go with a box, it will sound the same because the box is large enough to simulate infinite baffle.

So, yeah. Your .25 cubes or so really isn’t going to impact your sound much at all. Also, most manufacturers’ recommended boxes tend to be too small in my personal opinion. A few guys on the board agree. Still, you should get some pretty good sound out of your box granted I have no idea how those subs sound.

Ported is a whole other animal that I don’t feel like going into right now.

Grizzlee

Hey Gummie

what size wiring should I be using to wire the subs (inside the box?) the old box that I had made professionally had monster cable (not sure what gauge)

I haven't felt well enough to finish the box yet.

Don