Do I need a minidsp? Onkyo TX-RZ830 / Adcom GFA5400 for subs - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 7 Old 09-21-2019, 12:41 PM - Thread Starter
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Do I need a minidsp? Onkyo TX-RZ830 / Adcom GFA5400 for subs

Starting to dig deeper into the home theater goodies and wanting to step up my sub game. Currently running a pair of Klipsch R-120SWs off a Onkyo TX-RX830 and it does ok but the subs start to get overpowered by the mains at higher volumes. I got a smoking deal on a Adcom GFA-5400 two channel amp and I am wanting to use that to power a pair of 15" subs I am building custom enclosures for to put in the back of my room. The subs are nothing super special (~20 year old Rockford Fosgate subs) but hold a significant amount of sentimental value to me and I would love to be able to use them.

My problem is that when I hook the sub out on the Onkyo to the input on the Adcom I get very little volume, almost none at all even cranked all the way on the receiver. I hooked my phone up to the amp using RCA cables on the input and get good volume so I know the amp is fine. From what I am finding it looks like the output voltage on the sub out on the receiver is just too low for the amp to use? With that, it seems like a minidsp hd is exactly what I need to integrate all four subs and make it all work smooth as it can convert the output to higher voltage that can be used by the amp?
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post #2 of 7 Old 09-21-2019, 03:23 PM
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Originally Posted by RToth View Post
Starting to dig deeper into the home theater goodies and wanting to step up my sub game. Currently running a pair of Klipsch R-120SWs off a Onkyo TX-RX830 and it does ok but the subs start to get overpowered by the mains at higher volumes. I got a smoking deal on a Adcom GFA-5400 two channel amp and I am wanting to use that to power a pair of 15" subs I am building custom enclosures for to put in the back of my room. The subs are nothing super special (~20 year old Rockford Fosgate subs) but hold a significant amount of sentimental value to me and I would love to be able to use them.

My problem is that when I hook the sub out on the Onkyo to the input on the Adcom I get very little volume, almost none at all even cranked all the way on the receiver. I hooked my phone up to the amp using RCA cables on the input and get good volume so I know the amp is fine. From what I am finding it looks like the output voltage on the sub out on the receiver is just too low for the amp to use? With that, it seems like a minidsp hd is exactly what I need to integrate all four subs and make it all work smooth as it can convert the output to higher voltage that can be used by the amp?

The Adcom GFA-5400 is not a subwoofer amplifier. Its rated at 125 watts into 8 ohms. You'll likely damage the amp attempting to drive 15" subs. You need an amplifier stable down to whatever impedance your subs are. I'm guessing 4 ohms.

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post #3 of 7 Old 09-21-2019, 03:36 PM - Thread Starter
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GFA-5400 is rated 200 watts RMS per channel @ 4 ohm which is exactly what the subs are rated. I know very well it is not designed to be a dedicated sub amp but in this case it will be just fine to add some extra boom.
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post #4 of 7 Old 09-21-2019, 03:52 PM
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car subs give terrible performance compared to home subs Im sorry to say in most cases. it can be done, but shoot...a home sub can be had for 200 bux with an amp.

Power: Marantz sr7008, NAD C 275Bee x 2, Video: Oppo 103, Samsung 75un6300
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Subs: Rythmik FV25HP, Rythmik FV15HP
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post #5 of 7 Old 09-21-2019, 03:57 PM - Thread Starter
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With a proper box they will do good. I already have two home subs and plan for a pair of Dayton Ultimax 18s in full Marty boxes, but for now I have the amp, I have the subs, and can build a good box easily.

I know they are car subs, I know the amp is designed as a sub amp, but this is what I have and this is what I am going to do with it. Maybe it will be great, maybe not... Either way it will be done, I'm just asking for a little help with this part
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post #6 of 7 Old 09-21-2019, 04:06 PM
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Quote:
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With a proper box they will do good. I already have two home subs and plan for a pair of Dayton Ultimax 18s in full Marty boxes, but for now I have the amp, I have the subs, and can build a good box easily.

I know they are car subs, I know the amp is designed as a sub amp, but this is what I have and this is what I am going to do with it. Maybe it will be great, maybe not... Either way it will be done, I'm just asking for a little help with this part
fair enough...here a thread

https://www.avsforum.com/forum/155-d...ofer-home.html

your most likely gonna need mini dsp or xover/filter setup...some friends have had fair success others was a joke. good luck.

Power: Marantz sr7008, NAD C 275Bee x 2, Video: Oppo 103, Samsung 75un6300
Speakers: Focal aria 948, Focal cc900, Klipsch synergy KSF 10.5, Magnepan LRS
Subs: Rythmik FV25HP, Rythmik FV15HP

Last edited by torii; 09-21-2019 at 04:10 PM.
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post #7 of 7 Old 09-22-2019, 04:06 AM - Thread Starter
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Originally Posted by torii View Post
fair enough...here a thread



your most likely gonna need mini dsp or xover/filter setup...some friends have had fair success others was a joke. good luck.

Thank you torii.

I think the biggest challenge in this will be building the right box. If I can get the box right I have no doubt that these will slam hard.

To add to this though, the reason I am so dead set on using these subs is because of the sentimental value they have to me. They were given to me in 2001 as a graduation gift and were stolen maybe a year later. They broke into my old S10 Blazer and stole everything I had including breaking the window on the door to get in. The guy was caught and had to pay for it all and I never thought I would see any of the stuff again. EIGHT YEARS later I get a letter in the mail from the local police department saying I need to come pick the subs up as they were clearing out the evidence room, I had no idea they were even there! Since then they have had very little play time on them, but I really want to put them to use if nothing else because it is a crazy story. The subs are Rockford Fosgate HE 15s, single 4 ohm coils 400 watt max so like I said before nothing super crazy and it certainly won't take much to drive them. I think the GFA-5400 will do quite well with these, of course I could be wrong but time will tell. If nothing else I will put that amp to good use somewhere else and get an iNUKE to drive them.
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