I am in the planning process for my own audio system upgrade on my Ultra using the valuable wisdom from the members on this forum. I was researching new products introduced last week at the Consumer Electronics Show (CES) when I found (2) new amplifiers from Rockford Fosgate that could be easily integrated into the confines of a fairing installation. These amps were listed in Car Audio magazine's "Top Products of CES 2011 Part 2" (see link below)

http://caraudiomag.com/articles/top-...es-2011-part-2

I pulled up the specs on the website and found the following:

http://www.rockfordfosgate.com/produ...n_US&p_status=

Rockford Fosgate Punch PBR300X4
75W x 4 (impedance of load not given)
MSRP: $239.99
1.53"H x 4.25"W x 6.75"L

Rockford Fosgate Punch PBR300x1 - Monoblock amp for subwoofers
75W x 1 (4 ohms)
150W x 1 (2 ohms)
300W x 1 (1 ohm)
MSRP: $239.99
1.53"H x 4.25"W x 6.75"L

For comparison
Arc Audio KS125.2 Mini
70W x 2 (4 ohms)
125W x 2 (2 ohms)
250W x 1 (4 ohms)
MSRP: $329.99
1.7"H x 4.8"W x 8.25"L

I have been removed from the car audio world for over a decade. In the early to mid 90s I designed and installed car audio systems for my own vehicles and those of my friends as a hobby. In those days my favorite amps were the now "old school" Rockford Fosgate Punch amps including the highly-regarded, but very underrated (in terms of power) Punch 50 that made an impact in the 50W and under classes of the car audio competitions. I have read that over the years Rockford Fosgate was forced to build products to a competitive price point which forced some compromises on many fronts.

I am curious how this 4-channel, attractively priced amplifier with a compact form factor similar to the Arc Audio/Elf Audio/Wet Sounds amplifiers would compare in our motorcycle audio applications.

Fine Print: I am not associated with Rockford Fosgate in any way. I am just passing along a potentially interesting product announcement to my fellow Harley Davidson enthusiasts.

 

I am with you on the car audio history and also am very curious about this. I am going to put something up on the touring page to see if I get any info from anyone there. I, just like you am in the planning stages still and think at $240 MSRP you could save a good chunk of cash!!!

 

Looks like a sweet unit. As long as it has speaker level inputs it should be a great option. I'm sure it will be able to be found at a discounted price easier than the other two brands also.

Good find.

 

I called Rockford Fosgate about ten days ago to get some info on them. The fella said the 75W x 4ch. aren't out yet, and should be available about mid April. I have an amp and then an in line amp hidden on my bike.The sound and volume are very good,,,,,,but always looking to improve things. This amp looks interesting.

 

There's a couple of items to note here. Remember that most "claimed" wattage is maximum (fully distorted) wattage, and that is a marketing number, pretty useless in the real world. You would never listen to music at (or anywhere near) that level - it would be so distorted it just sound like hash, right before your speakers blew up. The only meaningful number to compare amplifier power is RMS wattage, and in the car audio world, even that is allowed to be rated at 1% distortion (which would be uncomfortably gritty to listen to) - but at least it equalizes the playing field. To give you an idea how out-of-skew and misleading total power numbers can be, the stock Harmon/Kardon head unit on my Ultra is claimed to produce 160 watts (and that's the number Harley likes to promote) but in reality, only produces about 15-17 watts RMS per channel.
The second thing to keep in mind is that "Power", or wattage, is a function of voltage times amperage - so I can increase the advertised wattage by increasing either the voltage OR the amperage (current) in the output stage. How power is produced is, in a large part, determined by circuit topology, defined by "Class" - Class A, Class A/B, Class D, are some of the designs I'm familiar with.
Speaker drivers are moved by a change in voltage, but are CONTROLLED by current, or amperage. The tradeoff is that high current outputs create a lot of heat that needs to be dissipated via mass and surface area, just like the cylinders on our bikes. High voltage outputs will fling driver around with very little control - which is okay at low volumes, but the more you turn it up, the more likely it will be to sound "blurry". This is different than distortion, which is an electronic distortion of the sound wave from the amp, and will melt voice coils.
So how does all this relate to the discussion...? A small amp with little to no heat dissipation is not likely to produce much current - unless the laws of physics have changed while I was sleeping, you can't produce current without heat, and you can't build up heat without melting the unit that's producing it! Rockford Fosgate lists these new units as "Class BR" - which is a new circuit topology that is almost certainly voltage dominated. The Biketronics amp is another little amp looks good on paper, too - 75 watts RMS per channel - but sure enough, is a Class D amp - not much current. The reason this is so significant for us is that at 70 miles per hour, we need to turn these suckers UP to hear them, and that's exactly where a low-current amp is likely to be at its worst.

 

wow. maybe i needed that lesson. more research at 2:14am est. At least i didnt go in the garage and fire up the bike for a field trip.

 

how do the kenwood and the crunch do with maintaining heat in tight spaces. I currently have an alpine 9886m stereo with titan 6.5 speakers and hawgwired tweeters. I thought that the alpine powerpack would do the job i need in terms of powering the speakers without much heat dissipation. While all of that sounds good, I would like to go a little louder and i want to make sure im not burning anything up under the hood for a little more beat in my system.

 

Part of my system is an small amp from UniqCycle. It was adequate at highway cruising speed. I installed an Alpine power pack. That did the trick. We can hear things very well at any speed we travel at now. Still interested in the Rockford Fosgate amp. If I can find a spot to mount it and keep it not to noticeable. I have the two amps hidden out of sight on the bike right now.

 

Well, heat is a function of volume and frequency. Remember, these car amps are designed to be bridged into mono mode and power 12" subwoofers, because a lot of kids want to buy the cheapest thing they can get and still thump out the bass. Lower frequencies require longer voice coil travel and a lot more current to control that travel. And it's current flow that produces heat.

So now let's apply these amps to our situation: although we do need the volume to hear our stereos on the highway, 5-1/4 or 6-1/2 in drivers don't reproduce much bass, or move much air! It's unlikely (in reality) that we're really reproducing much below 100 hz, and if we are, it's rolling off at about 6db per octave. That means that the last two octaves of music that we can hear (100 hz - 50hz, 50 hz to 25 hz) are being delivered at a lower volume - music at 50 hz (a tight bass drum)being about 1/4 as loud, music at 25 hz (a very, very low organ note, for example, or some components of the cannon shots in the 1812 overture) at 1/16 the volume.

So - long answer to your question, but it's not likely that we would overheat a 60 or 75 watt per channel amp mounted on our bikes.

Unless you had a pair of 12 inch subwoofers mounted in the saddlebags, of course...

 

Checked the RF website today and the amp is now $269 (a $30 increase!) and shows delivery in May.

Carl