HD1200/1 vs RD1500/1

[AceE012]

Hello, I am installing (3) 12TW3 subs that will be wired to 1.3 ohms in a down firing sealed box.  I currently have a JL Audio 1200/1 which (per JL) is the max output for these subs.  It has been suggested though that I power these (3) 12s using a RD1500/1 amp in place of the HD1200/1 because the subs can easily handle the extra power.  I don't mind the cost of the RD1500/1 because I can easily sell out of the HD1200/1 and get my money back.  Is the 300 watts worth dumping what I believe to be a higher quality amp though?  I know that JL normally slightly underrates their subs and I do believe that the (3) 12TW3s can easily handle the 1500 watts... 

[Joe X]

If you are running 1200W you would need 2400W to gain 3dB which is a very discrete gain i output, it is safe to say that 300W will not be a compelling gain in output if it is discernible at all.

 

Also the RD1500/1  will only source 1500W at 1 ohm, at 1.3 ohm will source less so your expected 300W gain is questionable,maybe 250W, 200W or less?

 

What I would recommend is checking your electrical and your gains to be optimal, improper electrical can ruin both output and sound quality on a system.

 

If those fixes are not enough changing to a sound quality specific ported design could vastly improve your output, 3-4 dB without sacrificing much sound quality.

 

[Kyblack76]

Just here to say to say, those JL slash amps are cool. Especially if it has the RIPS feature.  (the constant power stuff like rockford)

You are over thinking 300 watts, and thinking the number on the box matters.  

Your electrical will be more important than the board in this case. 

[AceE012]

Well, I forgot for one reason or another that the HD1200/1 only supports loads from 1.5 to 4 ohms.  I guess I'll have to run with the RD1500/1 because my load will be at 1.33 ohms.. 

 

Curious though, I am now going to have 2,860 total watts of power between the subs and the other speakers.  All amps are at near 75% efficiency so I have calculated that I can potentially pull about 275 amps (@ 13.8 volts).  I do have a 2024 Chevrolet Diesel and I did order it with the oversized alternator which is 220 amps.  I assume that even though the system at full load can potentially hit 275 amps this is extremely unlikely to ever happen and I would more or less have to be playing a sine wave to even get close.  Lastly, I also have duel batteries so I assume this would give me some time buffer but this is not something I am used to calculating.  

 

I believe I will need to upgrade the 220 amp alternator but does anyone have any input on this?   

Edited September 16, 2024 by AceE012

[Joe X]

10 hours ago, AceE012 said:

Well, I forgot for one reason or another that the HD1200/1 only supports loads from 1.5 to 4 ohms.  I guess I'll have to run with the RD1500/1 because my load will be at 1.33 ohms.. 

 

Curious though, I am now going to have 2,860 total watts of power between the subs and the other speakers.  All amps are at near 75% efficiency so I have calculated that I can potentially pull about 275 amps (@ 13.8 volts).  I do have a 2024 Chevrolet Diesel and I did order it with the oversized alternator which is 220 amps.  I assume that even though the system at full load can potentially hit 275 amps this is extremely unlikely to ever happen and I would more or less have to be playing a sine wave to even get close.  Lastly, I also have duel batteries so I assume this would give me some time buffer but this is not something I am used to calculating.  

 

I believe I will need to upgrade the 220 amp alternator but does anyone have any input on this?   

 

You got it exactly backwards, the HD1200/1  will give 1200W at 1.33 ohm  bu the RD1500/1 will not give 1500W at 1.33, it will give less, I wouldn't recommend getting the  RD1500/1 at all unless if you like how it looks or something like that, you won't get louder at all.

 

As for the alternator the 220A one will suffice for either amp no problem as long as you don't play continuous sinewaves as you say,  just music, that includes the car services and a mids and highs amp 400-500W RMS, just do use well installed quality power wiring for your amp or amps.

[AceE012]

So even though JL states the HD1200/1 will not to operate below 1.5 ohm, you think I will be ok?  Sorry just want to clarify, their specs state the range is 1.5 - 4 ohm.  I know I'm close but I don't want issues later is all.

 

@ 4 Ω	1200 W RMS x 1
@ 3 Ω	1200 W RMS x 1
@ 2 Ω	1200 W RMS x 1
@ 1.5 Ω	1200 W RMS x 1

[Joe X]

Yes sorry I misread the specs BUT its the same you just wire coils in series, subs in parallel down to 2.66 ohm and you will get 1200W to the 3 subs. You won't get any less power than 1200w because it is a constant power amp, in normal amps you wire down to the lowest impedance to get the most power but not with this one, also will deliver 1200W regardless of the input voltage (12V, 14 V) unlike normal amps.

 

 

[eimhear]

The HD1200/1 provides a solid 1200 watts RMS, which, as you mentioned, meets the recommended max power for the 12TW3 subs when wired to 1.3 ohms.

The RD1500/1 delivers 1500 watts RMS, adding 300 more watts of power, which could increase SPL (sound pressure level) but likely not enough to make a significant difference audibly. JL subs can generally handle a little more power, but this difference in output may not yield a dramatic performance increase.