So I put in a full stereo system for my wifes Scion xB. To keep the storage space to a maximum I built a fiberglass box to fit in the rear side panel. Its a Rockford Fosgate Prime 10" (R2D4-10) Dual voice coil. Its powered by a Rockford Fosgate 250watt RMS (R250-1D) Mono D Class amp. The power is there for the sub, I have tuned it out as best as I could, but its just not putting out the bump I was expecting. I dont know if its my box design, if I need to add some insulation to the box, my box isnt enough/too much cubic feet. Let me know your thoughts. Rockford Fosgate 10" sub http://www.rockfordfosgate.com/products/details/r2d4-10 Rockford Fosgate 250 watt Amp http://www.rockfordfosgate.com/products/details/r250x1 The pictures are not the final, box is due to be wrapped in carpet. Might need some help from that (Alex)
eeeek! duct tape?!?! did that leave any adhesive residue? For others doing this fantastic project themselves in the future- use blue painters tape. Some other tips too for those interested.......
Tried painters tape, masking tape, wouldn't stick. Cleaned with alcohol first, nothing. Cleaned with acetone, nothing. It was cheap duck tape so didn't hold like real stuff. Left barely anything behind, cleaned right off. In fact when I pulled the mold it came out with it even with a coat of Pam on it. However I also recommend trying the painters tape, this is only the 3rd fiberglass box I have made. Every other time I used painters tape. Rare exception.
I am guessing you are running it at a 2 ohm load, correct? My guess is the amp. My experience with amps is they are always over rated when it comes to power. I remember some of the first BOSS amps coming out stating they were 5000 watts. My JL Audio 500/1 was still a little under powered for my JL 10w3 and that amp is rated for 500 watts. You should always put a little poly-fill in the box to help with standing waves.
CES ratings cleared up a lot of that over hype on power. Don't think RF is in the same hood that BOSS is....... Too lazy to look up the equipment, so here's my trouble shoot on it..... Confirm impedance load from the driver- did you error in series vs parallel on the VCs and up the impedance. What is the actual power RMS on the little amp for the confirmed impedance What is the rated line level voltage from the HU- used to determine the proper gain setting on the amp. Is there a high pass crossover on the amp that may be set too high Do you need both inputs on the amp to get full power (like the Alpine PDX5- you needed to split sub signal to both inputs to get full rated output, even on the mono channel) What do the specs call for a sealed enclosure volume and how close are you to that What is the sensitivity rating on that sub?
I know...but I was just stating what was going on 20 years ago. My Old School PPI amps from the 90's put out a lot more power than anything I have purchased in the last decade.
Yeah, RF really isnt going to be in the same rankings as Boss. But I know what your talking about, definately not the case with this amp. Ok, so confirmed I am running at 2ohm on the amp (dual 4ohm on the sub). Amp is rated at 250 RMS, hooked it up to a meter and measured at 266 watts with it cracked all the way up, I am currently running it only at 231 watts. It is a mono block amp, only has low pass, 50-250hz. I didn't measure the boxes area, rough estimate .5-.75 cubic feet (860-1200 cubic inches) which puts me in range of manufacture recommended specs, (Sealed box volume 0.59 cubic feet or Ported box volume 1.4 cubic feet). So at this point I am leaning on putting some filling in the box, that's really only thing I can think of being wrong at this point. Unless someone else has a recommendation.
If memory serves me some filling in the box will make perform like a larger one.It has been a while since I have done this stuff.Is the enclosure airtight and does it flex at all when playing?..Have you heard this setup or something very similar.I remember back in the day that sometimes 2 very similar systems would sound very different in 2 different vehicles..
and by more poly fill, we are talking lbs of poly fill. Pack it tight to get any perceived benefit; which will not be night and day. If your expectations are 10 on a given scale and it's currently performing at a 6, more poly will not get you there. You may get to 7 or 8, but it's not a miracle worker. You would need to address the other aspects of the system to get desired results.
After doing a little more research about fill and the effects, I do believe that is the issue. The bass is too sharp, need to slow the waves down, mellow it out. Im going to try and explain it the best I can. If you were to look at the bass sound wave, the current setup would look very jagged and sharp with short wavelengths. The amplitude seems spot on, however is like I need to stretch the waves out, and make them a little more smooth. Im a super geek, so thats about the best way I could answer it.
This is the best image I could find to help explain it. Now technically I know Im basically describing frequency, but imagine those lines not being smooth, more jagged, like there is reverb essentially.
Check the length of the sound waves for the frequency range you are reproducing with a subwoofer..... 20hz ~ 60 FEET; 80hz ~ 16 FEET. You can't "stretch" a wave out- frequency in Hz is a given wave. Even if you could; what net results would you get from "stretching" the length- the length of your car isn't even in the subwoofer frequency range.. The box in a sealed "system" has remarkably little to do with response as you aren't actually tuning anything like in a vented box. What you are doing is adding suspension via the compression of air inside the box, addressing the Q factor of the "system". This is what additional polyfill will "tweak" and it can affect tonality of the system, but not much for volume. You are over thinking this quite a bit. In a sealed system you have very few factors that affect the amplitude (volume) of the system- power and efficiency. Have you played with WinISD yet? I'm sure you have fully confirmed that it is running at a 2ohm load, but the statement above doesn't indicate so. A dual 4ohm driver can be run in series for an 8ohm load or parallel for a 2ohm load. I hope what you meant to say was: "I have confirmed that I am running my dual 4ohm voice coils in parallel, giving the effective load of 2ohms to the amplifier to get the maximum power of 250watts".... In an amp with a non-regulated power supply (which your RF appears to have based on specs from Crutchfield), that is the difference between 250 watts and 75-90.
Like I said, I know I was explaining freq, I was just trying to make sense of it all. However I do believe your right with " over thinking this". Its really just echo or vibration (reverberation) made by the subwoofer. The subwoofer is performing exactly how it should, the volume is fine, the frequency response is fine. Im just a perfectionist and searching for imperfections in my work. I ended up contacting a old work buddy of mine, who still does this stuff. His ear is still tuned. The sound I was hearing is in fact reverb/echo. There was also some roof and rear quarter panel vibration giving some very strange metal vibration. Needless to say, he told me it needs to have some filling in the box, and I need to purchase some dynamat to help dampen some vibration in the quarter panel. I should do the roof too, but thats a hell of alot of dynamat.
Definitely dont need more power, sub is only rated for 250 watts RMS. Amp is supplying plenty of power to the sub.