HDX4 amp match


WakeNBake520

CarAudio.com Enthusiast
Mar 5, 2020
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So I’m not exactly sure how large of an amp I should get for this sub... SQ says it’s 2k rms, 6k peak. Read somewhere that you can run two of their 4.8k amps strapped on it which leads me to think maybe 8-10k?

It’s ran parallel at .5 ohm currently on a Taramps Smart 3k but it’s not enough power. That and the low signal input required by this amp is a terrible match for my Kenwood DDX-9906 head unit.

Thoughts on wattage and brand(s) would be greatly appreciated, as well as any other info that might be deemed helpful.
 

Jeffdachef

Gunz That Turn on Nunz
Feb 5, 2013
18,543
796
South Coast Metro, CA
Get the soundqubed 4500 if you are running half ohm. If you still arent loud enough then its an enclosure design issue. Throwing power at the sub is not the way to solve problems because if you cant get loud on low power, throwing more power is not gonna get you that much louder. Whats the enclosure like and how is it positioned in the vehicle? From my last modeling of the HDX series for their 18s, you dont get any real performance until you have it in an 8.25 cubic foot box tuned to 26 to 32hz. They seem to like a lot more airspace than the old generation HDC series which only needed 5.5 to 6.0 cubes for the 18s.

So the 12s would need 2.75 to 3 cubes and 15s around 5.5 to 6 cubes.
 
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dragon.breath

Senior VIP Member
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Nov 22, 2007
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Since you already have a smart 3, you could buy a second one and run one per coil. If it will not get loud on 6k, it will not get loud.
 
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WakeNBake520

CarAudio.com Enthusiast
Mar 5, 2020
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They are sold out n have been since I got the cash to get it unfortunately which is why I’m looking at getting a substitute.

So it does get kinda loud now but nowhere near where I think it shoukd, but definitely has a signal issue with the smart 3. It’s input is .2 - 4V max n this headunit puts out 5v at “max”. It also jumps the signal meter on top of the amp to max forcing it into protect with certain songs with higher output or even high notes.

I built the enclosure n it’s a bit larger than the one recommended by SQ on their site but definitely a different shape, n is tuned roughly to 32-34. Net volume minus bracing n displacement is about 7.23 cu.ft. It’s in an 05 Nissan Titan king cab. I’ll attach the box design pic but it doesn’t include the ports.

For the ports I used 2x 8” pvc sections coming out of the top with 90deg fittings and extended the rest of the length towards the front to get to the tuning i did. I didn’t realize that I’d need such long ports otherwise I’d have likely went with a slot design if I could have figured out a good way to fit it. The ports currently face forward as does the sub. I am able to pretty easily change the ports direction, at least as far as space allows.

And honestly if the best thing to do is redesign n build the box then that’s cool too. Just trying to get this all working properly.
 

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Jeffdachef

Gunz That Turn on Nunz
Feb 5, 2013
18,543
796
South Coast Metro, CA
They are sold out n have been since I got the cash to get it unfortunately which is why I’m looking at getting a substitute.

So it does get kinda loud now but nowhere near where I think it shoukd, but definitely has a signal issue with the smart 3. It’s input is .2 - 4V max n this headunit puts out 5v at “max”. It also jumps the signal meter on top of the amp to max forcing it into protect with certain songs with higher output or even high notes.

I built the enclosure n it’s a bit larger than the one recommended by SQ on their site but definitely a different shape, n is tuned roughly to 32-34. Net volume minus bracing n displacement is about 7.23 cu.ft. It’s in an 05 Nissan Titan king cab. I’ll attach the box design pic but it doesn’t include the ports.

For the ports I used 2x 8” pvc sections coming out of the top with 90deg fittings and extended the rest of the length towards the front to get to the tuning i did. I didn’t realize that I’d need such long ports otherwise I’d have likely went with a slot design if I could have figured out a good way to fit it. The ports currently face forward as does the sub. I am able to pretty easily change the ports direction, at least as far as space allows.

And honestly if the best thing to do is redesign n build the box then that’s cool too. Just trying to get this all working properly.
dude you have the port forward firing. thats why you arent getting any output. Thats cancellation hell, definitely have the port firing at a solid wall if you can.

Also the protect thing is not because of the input voltage. its because you are running it at half ohm and borderline clipping it.
 
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dragon.breath

Senior VIP Member
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Nov 22, 2007
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I would definitely redo the box before I spending money on more power. I would even try sealed before leaving it like that.
 
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WakeNBake520

CarAudio.com Enthusiast
Mar 5, 2020
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So for now I’ll redirect the ports, at least until I can get another one built. I’m assuming that they both should face the same direction, towards a solid wall, at a distance just larger than the diameter of the ports. Right?

If I were to design a new box, you said 8.25 cu ft n up is where it really started to put out. Is 8.25 ideal or if I can get more, do so?

I would use a slot port for practicality but what volume and cross area would I want the port to be? Also what would be a good width for the port to avoid noise and adverse effects? And which direction would be best for the sub & port to face?
 
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WakeNBake520

CarAudio.com Enthusiast
Mar 5, 2020
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I see about the signal thing. I knew it was borderline clipping but the clip light doesn’t light up and the gauge on the top of the amp says it indicates input signal level and literally as soon at it tops out, every time, the amp pops off into protect. The flashes when it happens indicates a low voltage shut off (according to manual). Kinda misleading.

So eventually I’ll need a different amp anyway given that this one shouldn’t be driven at half ohm. What would be a good one to do the job real well? So I can get a price and hold onto the cash for it.
 

Jeffdachef

Gunz That Turn on Nunz
Feb 5, 2013
18,543
796
South Coast Metro, CA
So for now I’ll redirect the ports, at least until I can get another one built. I’m assuming that they both should face the same direction, towards a solid wall, at a distance just larger than the diameter of the ports. Right?

If I were to design a new box, you said 8.25 cu ft n up is where it really started to put out. Is 8.25 ideal or if I can get more, do so?

I would use a slot port for practicality but what volume and cross area would I want the port to be? Also what would be a good width for the port to avoid noise and adverse effects? And which direction would be best for the sub & port to face?
8.25 is for the 18 in my original comment i mentioned above. read the last few sentences for the 12s and 15s.

If you can make a wall thats the only time a forward facing port next to the sub would work. but usually for a stand alone box, side ported is fine, up ported is mediocre.
 

dragon.breath

Senior VIP Member
10+ year member
Nov 22, 2007
653
65
Al
I see about the signal thing. I knew it was borderline clipping but the clip light doesn’t light up and the gauge on the top of the amp says it indicates input signal level and literally as soon at it tops out, every time, the amp pops off into protect. The flashes when it happens indicates a low voltage shut off (according to manual). Kinda misleading.

So eventually I’ll need a different amp anyway given that this one shouldn’t be driven at half ohm. What would be a good one to do the job real well? So I can get a price and hold onto the cash for it.
Sounds more like you have a low voltage problem.
Also the smart 3 makes the same power at 2 ohms as .5 ohms. You could just rewire the sub for 2 ohms.
 
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WakeNBake520

CarAudio.com Enthusiast
Mar 5, 2020
33
2
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So 8.25 is what I’ll aim for then, as I do have the 18. And side ported as well.

What port area/volume should it be for that size of box? U mentioned 26-32 hz is what worked for your last install on one so I’ll probably aim for 28. Is it advantageous to have the port along any side in particular? I’m thinking the back side bc the front will be wedged to fit to the seats but I’d welcome any additional advice as well.

I knew the amp made same power at 1&2 but didn’t know at .5. I had it originally at 2 ohms but clipping light would flash a lot more and it def sounds way better at .5 IMO.

You could certainly be right about the voltage part, but my gauge doesn’t really go below 12.4 or so n if it does I cut volume back to prevent any damage. I’ve got an ultra cap in there but I’m waiting for my 320 amp alt to return and my battery bank to get here to install.
 

Jeffdachef

Gunz That Turn on Nunz
Feb 5, 2013
18,543
796
South Coast Metro, CA
So 8.25 is what I’ll aim for then, as I do have the 18. And side ported as well.

What port area/volume should it be for that size of box? U mentioned 26-32 hz is what worked for your last install on one so I’ll probably aim for 28. Is it advantageous to have the port along any side in particular? I’m thinking the back side bc the front will be wedged to fit to the seats but I’d welcome any additional advice as well.

I knew the amp made same power at 1&2 but didn’t know at .5. I had it originally at 2 ohms but clipping light would flash a lot more and it def sounds way better at .5 IMO.

You could certainly be right about the voltage part, but my gauge doesn’t really go below 12.4 or so n if it does I cut volume back to prevent any damage. I’ve got an ultra cap in there but I’m waiting for my 320 amp alt to return and my battery bank to get here to install.
For now i'd just work on having the port fire towards a solid wall and wait for the alt before taking more actions. patience is key.
 

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