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Old 02-15-2012, 01:10 PM
CDF346 CDF346 is offline
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Default 4 ohm amp to 2 ohm speakers

This is my flh project I am finishing up.http://www.hdforums.com/forum/evo-cl...onversion.html
i have installed an 05 radio, hawgtunes nca amp, which Iam running to the fairing.
i am preampingout to a line output interface, mounting a r fosgate 4 channel amp to run the rear speakers, and the sidecar speakers which are polk audio marine's (4 ohm). I am also putting a kenwood self powered sub to the back of the sidecar seat, along with a big fatass cap. My other speakers are hogtunes, 2 ohm'r's. I can series in 2 ohm resistors to 4 ohm the 2 hogtunes speakers, is there a specific wattage rez I should be looking for?
the r fosgate amp out's say 4ohm only, so i dont want to play with that, though it would wok w 2 ohm'r's
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Old 02-15-2012, 09:27 PM
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UltraNutZ UltraNutZ is offline
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1. you can't logically or technically add a resistor to a 2 ohm speaker to make it a 4 ohm speaker. it just doesn't work that way. The wattage you'll be pushing through that resistor will generate so much heat, you'll do one of two things. either keep popping resistors, or set your ride on fire.
2. fosgate amps have always been known to be WAY underated for power and impedance capabilities. Meaning if it was a 75w x 2 amp into a 4 ohm load, it was capable of producing 250w of power at a bridged 1 ohm load.
3. this pbr300x4 is not of this caliber and in fact I was sorely dissapointed in it's output power ratings. yes it will sound much better than stock and yes i've also installed it in a 4 channel 2 ohm load configuration and it ran fine for over 2 weeks of heavy use in my garage with the amp getting slightly warm to the touch during almost 4 hours of continuous usage driven at about 1/2 radio volume and the gains turned up about 3/4 the way.

On a side note; I am partial to the J&M 4 channel amp but I also understand folks are looking for a more cost effective alternative to them.. this was the primary reason I bought this pbr300x4 amp and gave it to a friend who couldn't afford to buy it. This was an honest shot at being able to install this amp and report good things back to you folks who wanted that more cost effective solution.
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Motor: Vee-Twin Street Port, Andrews 57H, Fullsac DX, CVO 4" Cans w/Fullsac 2.25" Power Cores, TTS, SE Ventilator, Barnett +1, 480 Spring, ClutchWiz
Audio: Kenwood KIV-BT901, RF 3sixty.3 DSP, (2) SoundStream TN4.900D, Biketronics (4) 7.1", (2) 6.5", (2) 6x9"

Last edited by UltraNutZ; 02-15-2012 at 09:35 PM..
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Old 02-15-2012, 11:08 PM
CDF346 CDF346 is offline
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Ok, 10-4. I was just being a cheap bastard. Ill just pick up a set of 5/4 polks for the tour pack and no pain and misery. thanks for the help.
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Old 02-16-2012, 06:25 AM
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my point was i'm dissapointed in the amp. the amp, based on my 2+ weeks of testing will drive a 2 ohm load fine.
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Audio: Kenwood KIV-BT901, RF 3sixty.3 DSP, (2) SoundStream TN4.900D, Biketronics (4) 7.1", (2) 6.5", (2) 6x9"
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Old 02-16-2012, 10:21 AM
CDF346 CDF346 is offline
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Yes, I got what you were saying that the amp wasnt like the salesman said. Perhaps with 2 4o load and 2 2o load it wont stress as much as driving 4 2o. Im just curious as to how much current will pour out of it also. That may be an issue I will meter it when its up and running to see what it draws.
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Old 02-16-2012, 02:21 PM
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Harleypingman Harleypingman is offline
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Quote:
Originally Posted by UltraNutZ View Post
1. you can't logically or technically add a resistor to a 2 ohm speaker to make it a 4 ohm speaker. it just doesn't work that way. The wattage you'll be pushing through that resistor will generate so much heat, you'll do one of two things. either keep popping resistors, or set your ride on fire.
2. fosgate amps have always been known to be WAY underated for power and impedance capabilities. Meaning if it was a 75w x 2 amp into a 4 ohm load, it was capable of producing 250w of power at a bridged 1 ohm load.
3. this pbr300x4 is not of this caliber and in fact I was sorely dissapointed in it's output power ratings. (So what disappointed you regarding its power output? The RF PBR 300X4 is supplied with a test certificate showing its power output measured by an industry standard. The two I have exceeded the advertised 75W per channel comfortably--one was 83W per channel and the other was 85W per channel. How did you measure the power output that caused you to be disappointed?) yes it will sound much better than stock and yes i've also installed it in a 4 channel 2 ohm load configuration and it ran fine for over 2 weeks of heavy use in my garage with the amp getting slightly warm to the touch during almost 4 hours of continuous usage driven at about 1/2 radio volume and the gains turned up about 3/4 the way. (Why run an amp the mfr. says uses a 4 ohm impedance speaker with a 2 ohm impedance speaker? Also, the quality of the speaker plays a major role in the sound quality--the amp plays a much smaller role in sound quality. What were you trying to assess--that you could use an unspecified 2 ohm speaker with the RF amp w/o killing the amp; etc.?

On a side note; I am partial to the J&M 4 channel amp but I also understand folks are looking for a more cost effective alternative to them.. this was the primary reason I bought this pbr300x4 amp and gave it to a friend who couldn't afford to buy it. This was an honest shot at being able to install this amp and report good things back to you folks who wanted that more cost effective solution.
Personally, the RF amp works great and is an outstanding value (4-channel amp) compared to the J&M 500W amp (actually a 280-200W amp when using 4 ohm speakers used by the RF amp; comparing apples to apples).

There are a ton of highly favorable RF amp threads in the Touring forum. Granted, very few folks have compared multiple amps. In my case, I ran the Arc 125.2 amp before using the RF amp. Frankly, I'm not enough of an audiophile to say which was better under the same conditions. I know that I'm very pleased with the RF amp driving a 4-channel system and believe it delivers at least equivalent sound to the Arc 125.2 that I used with a 2-channel set-up.

Also, I've recently installed a second RF amp on top of the HK head-unit (mounting the two amps lengthwise) and adding HD saddlebag lid speakers and tour pak pod speakers for 8 separately powered channels--pretty cool w/o sacrificing tour pak or saddlebag space for the second amp.

Carl
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Old 02-16-2012, 02:39 PM
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hehe.. leave it to Carl... I think what my problem is;
I pulled the amp out of the box, got everything installed, noticed a slight "tainty" sound to it so started investigating. The moment I touch the gain controls incredible amounts of "scratchiness" (if that is even a word) come from all 4 speakers and literally makes them inaudible. Remember the old car stereos that had volume control *****? after a couple of years, they would get dirty and scratchy, pull the top off the radio, spray some contact cleaner through the holes in the (pots) let it dry out and you're good for another couple of years. My past experiences (many years of making cars go boom) has been nothing less of stellar with RF. I guess I just need to contact RF to get a swap on the amp and then report back more favorably... stay tuned....
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"SEPST FOR DUMMIES" by Foxster
"PV Step By Step" by sportytrace
2012 FLHTK
Motor: Vee-Twin Street Port, Andrews 57H, Fullsac DX, CVO 4" Cans w/Fullsac 2.25" Power Cores, TTS, SE Ventilator, Barnett +1, 480 Spring, ClutchWiz
Audio: Kenwood KIV-BT901, RF 3sixty.3 DSP, (2) SoundStream TN4.900D, Biketronics (4) 7.1", (2) 6.5", (2) 6x9"
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Old 02-16-2012, 06:28 PM
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Quote:
Originally Posted by UltraNutZ View Post
my point was i'm dissapointed in the amp. the amp, based on my 2+ weeks of testing will drive a 2 ohm load fine.
I wouldn't recommend using the RF PBR-300/4 in a 2-ohm setup. While it may work fine in some installs, it was not engineered to those specs so "all bets are off".

I'll agree with Carl here ... having tested both the Arc series of amps (my experience is with the 125.2) and the RF PBR series the RF is at least as good, if not better, than the Arc. I wish the RF PBR-300/4 had a tuneable high-pass filter like the Arc (the RF is fixed at 80 Hz centered) but the output of the RF is outstanding.

One thing ... the RF PBR-300/4 does not have a switchable input for RCA/Speaker Level. While you can use either ... my testing shows that the output does suffer on the RF when using RCA outs from the stock H/K head unit. This is to be expected without a switchable low-level/high-level input.

When using the RF PBR-300/4 and speaker-level inputs, it certainly competes with the Arc (et al) output. I prefer the RF to the Arc for my system, the price, and the ease of install.

Hope this helps.
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Old 02-21-2012, 08:49 AM
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UltraNutZ UltraNutZ is offline
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follow up:

I've confirmed 2 things since this last post.
1. 2 ohm setup will not work. The reason for this setup was to test the amp. It failed the 2 ohm test (which i figured it would but wanted to test anyway) and clips if volume goes up above 1/2 for any period of time.
2. there is in fact an issue with the amp itself where-as it driving a pair or two pair of speakers cannot be properly achieved because of the bad pots. RF will swap the amp and I'll be putting the new amp up for sale here when it arrives.
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"TTS FOR DUMMIES" by Mr.Wizard
"SEPST FOR DUMMIES" by Foxster
"PV Step By Step" by sportytrace
2012 FLHTK
Motor: Vee-Twin Street Port, Andrews 57H, Fullsac DX, CVO 4" Cans w/Fullsac 2.25" Power Cores, TTS, SE Ventilator, Barnett +1, 480 Spring, ClutchWiz
Audio: Kenwood KIV-BT901, RF 3sixty.3 DSP, (2) SoundStream TN4.900D, Biketronics (4) 7.1", (2) 6.5", (2) 6x9"
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Old 02-21-2012, 08:49 AM
 
 
 
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