I have had my new amp and sub(see sig.) completely installed for a couple of days now. Sealed enclosure, 200w RMS sub, 200+ watt amp. The bass sounds very good at low to medium volume levels but seems to fade at higher volume. It's hard to explain, but it doesn't seem to distort or sound bad, it just doesn't hit quite as hard after a certain volume level. Anyone know what may be causing this?

 

Your 8" sub is not moving enough air for high-volume bass. Your solutions, unfortunately, will require replacement equipment. You can:
1) Get a larger subwoofer. Smaller subs generally need more power to move a given volume of air than a larger sub.

2) Get a more-powerful amp. A small sub in a small sealed box is fairly inefficient (requires more power). Ported/vented enclosures are often more efficient (louder for less power) at the expense of accuracy.

3) Add a second 8" sub.

4) Replace your sub with a more-efficient one, so it will go louder with the same input wattage. This can be checked in the sub's specs, and is rated in decibels at 1-watt input. A higher number is more efficient. Keep in mind that a 3-decibel increase in efficiency results in a doubling of perceived volume. The converse is also true - a sub with an 89-dB rating will sound half as loud as one with a 92-dB rating.

I've got a 10" MTX sub in a small, sealed enclosure, with a 250-watt amp driving it. I don't have any output issues, but my MTX 10" sub is pretty effiecient.

Good luck!

 

I see what you're saying robbobster, but I think I may have a problem with what I have that I can do something about. I wonder now if my enclosure may be too small. I have approximately .3 cubes loaded which is what Rockford recommends, but a guy at a local shop once told me that he usually builds boxes for trucks a little larger than called for. You think this would be something to try before I scrap the whole thing and start over? To get the best sound now, I have to turn on the bass boost, crank the gain, and for some reason it sounds better with the cross-over nearer to 250 Hz.

BTW, I know a friend of a friend with a Mustang running a single 8" that kicks a$$. His setup is very similar to mine other than the enclosure shape and size.

Sorry for all the questions. Thanks for the reply!

 

Ahhh...the gain control you mention throws a new twist into the equation.

I'm not sure about going against what Rockford recommends. Usually a MFR has tested their products every which way. While you may get more sound with a larger enclosure, it MAY come at the cost of accuracy or something else. However, you really have little to lose at this point if you are able to test demo a larger box in your truck. The trade-off may be wothwhile for you.

Now back to that gain issue... do you know what kind of output voltage your head unit is sending to your amp? Check your documentation. If you have 2-volt pre-outs, the signal may not be strong enough. You really want a minimum of 4 volts to get the most sound out of your amp. Any less, and the gain control may not be enough. Also, the gain control will amplify everything that is coming our of your receiver, including noise. 4-volt pre-outs (or more) will provide a clean signal that will cut through the road noise.

My last car had only 2-volt pre-outs on the head unit, and I had to really crank the gain up on my sub amp to get any bass at alll.

The x-over issue is odd. My guess is that the upper-bass frequencies are being over-amplified, and thus louder, while you don't have enough output voltage for the low-bass frequencies. You want the sub to produce sounds from 100Hz and below, as these are non-directional frequencies. Higher frequencies are directional, and you don't want the sub competing with your other speakers anyways, as it was not designed for this.

It sounds like you may have low-volt pre-outs. Ask your local shop if there is anything that can be done to amplify this signal without scrapping your head unit.

Of course, we'll have to start this discusion over if you DO have 4-volt pre-outs...

 

Don't yell at me for not giving enough info the first time! LOL! I'm not well versed in car audio. I am using a LOC in parallel with my rear speaks. The factory HU is still in. I'm running the 4 Blau 5x7s off the factory HU. I think you may be on to something about the low voltage. I can crank the gain on the amp, crank the remote gain, fade all the way to the rear, and it has enough to make my CD changer skip! So, it looks like I may need a new HU? May be a good Christmas present for my wife to give me!

 

I'm not a fan of upgrading other components while retaining the factory head unit. But I must admit that there are many who do this, and are happy with the results. Perhaps I'm an audio snob...

Try to shop around the web if you decide to replace your HU. Like most things, it seems prices vary wildly from vendor to vendor.

Good luck!