I went with the HD Boom Audio. It's all I'll ever need. Plenty loud and clean.
I hear it clearly at highway speed.

 

there is an audio forum here which may better answer your questions.

I work with concert audio --- the car audio world is full of BS and snake oil.
shops will sell you one component and when there is no improvement sell you yet another.

Here's what to watch for:

when comparing speakers look for the specification for sensitivity

it should be written as X dB at 1 watt measured at 1 meter.
X should be higher than 92 dB--- the higher the number the better, that means that you amp doesn't have to work hard to the point of distortion to turn electricity into sound ( the decibel scale is tough to explain, but 96 dB would sound twice as loud as 90 dB, 102 dB would be twice 96 dB every 6 dB is a "doubling" of apparent volume)

frequency response should be close to "flat" if you look at a graph on the package there may be humps but no peaks- a peak at 2 kilohertz is going to just sound bright, harsh and annoying.

some speakers have "tweeters" and a "frequency dividing network" or "crossover"--- these passive devices act as filters and can consume 30% of your available amplifier power. I'd stay away from these, as the marginal advantage of a tweeter is balanced by the amount of clean amp power lost- more likely to drive the amp to distortion at normal listening volumes.


-- from what I have seen most of the amps available are crap with horrible distortion ratios. in the 70's Total Harmonic Distortion ( THD) from good hiFi systems was . 2%....I now see specs written with 5% or 10% THD ( 50 times more distortion).... which would just sound bad.


reality? expecting to hear clear audio over wind and road noise ain't gonna happen at highway speeds
and if you wear a helmet it really ain't gonna.

on long trips I wear pro quality ( $500 and up) multiple driver ear buds. they keep the wind and road noise out and the stuff I wanna hear in and at a reasonable level. with an engineering background I wired into my stereo system so a have a jack for the buds.

short stuff around town I find the stock radio speakers work pretty darn good- and they are paid for.

mike

 

there are tons of options out there, but as many have said doing the job once is key. I cant say that is the case for me. I went with HOGTUNES and they do work, but I want good bass, and I want it loud. I am looking into the HAWG WIRED systems, but there is guy that just opened up a bike shop near and does custom radio work, one of his selling points, the only issue is I hope he is still in Biz when I get back home in June 2012. If he is I am going to have some cash to spend. I did all the motor mods this past summer when I was home, So now I want bad *** tunes. HOGTUNES work but if you want it very Loud, it is not the way to go. THey do have great customer service and if you have an issue they will take the time to walk you through it, but if you are a tune, stereo guy like myself then you might want to go with something else. JMO

 

Memphis does sell great sounding speakers but unfortunately they only come in 4 ohm configurations. Your HK radio is set up for 2 ohm speakers and if you don't go back with some brand of 2 ohm speakers, your radio output is going to be cut about in half.

In other words, you will have to turn your volume control almost wide open to get the same amount of loudness, almost sure to sound distorted.

Infinity makes 2 ohm speakers along with J&M. I think Polk and Hog Wired does too and maybe Biketronics.

 

Can someone please explain to me how the loudness of sound will be diminished from from running 4ohm speakers off of a 2ohm stable amp/stereo? Isn't it true that the 2ohm stable amp is able to easily push those 4 ohm speakers with less stress on the amp? To me it seems that if I put 2ohm to 2ohm that the amp will be working at it's highest output levels at high volume thereby coming close too or exceeding the threshold of when distortion sets in. I am learning about all of this because I want to upgrade my streetglide, but, like most, only want to do this once. Thank you for all of your responses to this lengthy question.

 

We run J&M Rokkers in our bikes. The extra price is not for the name, it is for the quality and sound of the speakers. For anyone who is local, please stop by the shop and take a lsiten. The combo of the J&M amp and speakers will blow you away. I am aware there are a lot of naysayers here, but the sound speaks for itself. One of these days I'll take a video in order to demonstrate.

Drew

 

Look forward to that if you get the time! ...

 

I went with Hertz speakers and am pretty happy with the results. I'm running them with an amp. Without an amp the improvement from stock would not have been worth the money to me. My system sounds real good with the bike sitting still but not what I'd hoped for when traveling at highway speeds. Sure, I can hear it but definitely not good sound quality. Listening to the system before buying is great, just be aware that the audition isn't happening in the actual listening environment.

 

VERY happy with the Harley Boom's on the StreetGlide. One of the best mods I've done to the bike.

T

 

It will take twice the amount of power to drive 4 ohm speakers to the same volume level. The HK radio is not powerful enough to do that without distortion. (Not a very loud level anyway.) I put a pair of Memphis Marine 6 1/2" speakers on my '03 EG Classic (4 ohm radio). They sounded great. I put the same speakers on my '08 Street Glide. By the time I got to a good listening level, they were starting to break up. That's real world experience, not numbers and theories.