Dual subs ohm rating needed?

Intending to add the JBL 8 channel amp upgrade to my 2021 TRD JBL system. Would also like to consider adding the dual 10" sub box behind the rear seats.

My question is, what ohm rating for the two subs is needed? 2-ohm, or 4-ohm? Using the JBL 8 channel amp, are the sub channel(s) summed to one signal? or independent 2 channels for subs? Wired in series? or parallel?

Thanks
Kenreau

 

Need the specs of the amp to determine what ohm load it actually is rated for.
Is it an aftermarket amp of some factory option? If factory, base it on the impedance of a factory sub (2ohm). If aftermarket, then look at the specs to see the rating. Most multi channel amps are a single, summed output at one terminal.

 

Thanks for the quick response.

The amp to be added is the JBL DSP 4086 dsp 8 channel amp. It is an add on to the factory oem JBL system.
RMS Power Output @ 2Ω = 60W x 8 channels
RMS Power Output @ 4Ω = 40W x 8 channels
Variable crossovers with hi-pass, lo-pass, band-pass capability & adjustable 0-to-48dB slopes. Selectable EQ adjustmentParametric or Graphic.

The existing JBL oem system has a single 8" sub in the back. I'm not sure if it provides two channels summed, or a single mono channel for that single sub.

I am wondering if this common 2 subs in a box upgrade is using two amp channels for two independent 4 ohm subs, or 2 ohm subs? or wired into a mono channel? two 4 ohm subs wired for a single 2 ohm load? or? lots of possibilities.

Thx
Kenreau

 

In your situation, that amplifier does not bridge any channels for a mono sub output. Channels 7&8 are preset to be sub channels but the most you'll get is 2x60watts @ 2ohms. For a single woofer you only use one output channel and you get 40 or 60 watts to it. To get the most out of a dual sub box, you will want to get two 2ohm subs (either a dual vc 4ohm or a single vc 2ohm) and then each sub wired separately to each channel (7-left 8-right) you'll essentially have stereo subs but you'll get the most power available to the subs (2x60=120watts) If you wire the two subs to one channel (2-4ohm subs into a single 2ohm load), you'll only ever get 60watts total @2ohms or 30w per sub which is pretty weak.
Imo 120watts max is NOT enough power for 2 subwoofers and I would recommend a mono block amp dedicated to the sub wether or not it's 1or 2 subs.

 

^ This is great advice..

 

^^ What @Toyotoholic said.

That JBL amplifier would be great for powering a set of active three way speakers for the front sound stage, plus a set of rear coaxials; or two sets of active two way speakers; or a front set of two ways, a pair of mid basses, and a set of rear speakers; or some combination like such. Unfortunately, it's not great for powering subs. Though, with the right subs you could do it. You would need to find a DVC 2 ohm per coil subwoofer with a relatively high sensitivity rating (93+ db) but the tradeoff is normally a big box and lackluster deep bass extension. EuroPop, though, would still thump.

Ideally, though, a decent mono subwoofer amp is the way to go. Class D amps are fairly inexpensive these days and are very efficient - meaning less heat and more power. Just don't clip them - they don't behave very well at all when being overdriven.

 

Great information, thank you. This confirms my fears and it will be more complicated to do it right.