SPL Trunk 'Wall' Build Log
- Thread starter Jonnyswboy
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I put money these subs will take 5k all day on music in a good box with clean electrical.
You gotta have super clean power. I know dudes who use the hell out of the v4's, they're 18's. He had each on 8k and the sub was bottoming out but he literally couldn't blow the coil. LITERALLY. These subs are absolute MONSTERS. Great choice bro.
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Jonnyswboy
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Can you play it at all? I forget, so sorry if you’ve said that, I talk to a lot of people every day.
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Jonnyswboy
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Hooked it up to my buddies two MD8ks briefly (underpowered but wanted to get an idea of the response curve) and it moves a lot of air. Peaking at 30hz which is a little lower than I wanted, but I don't mind it. Starts dropping off sharply beyond ~37hz. I clamped one of the amps/subs and it was about 5.5ohms at 28hz, which as I understand would be 2.75 ohms once they're wired in parallel to 0.5ohm on my amp. 2.75ohm is not bad. Would like to be closer to 1.5ohms but I should be alright.
This is clamping ~1500w per speaker, so about half power. I will post a longer video on full power once my electrical is installed.
It's going to have rise, for sure. It's a nice size single chamber, it's going to rise. I'm interested to see the drop off once you get it on full power.
I would still seal it off, man. You've got all of this great equipment and the box built, take it all of the way, if you can. I think we talked about port lengths and shortening. Lmk if you want to do that. I would try to seal it off. If you keep the subs and port from pressurizing the trunk, I think that'll help a lot. Just lmk. I'd really recommend sealing it off and trying it on full power, when or if you're able to. I expect sealing off your trunk to help with bandwidth. You're just simply going to be pressurizing less air to a higher pressure. If you cut that port length down, you probably want to shrink the box down also.
Without the box sealed off, can you push the box any further towards the back of the trunk?
I'd say the sharp drop off is a combo of this:
1. Forward firing box
2. Box not sealed off
3. Not full power yet
4. You have a good sized port area (for the very high power levels)
5. Lower tuning, of course.
Just some things to think about. It'll be interesting to see it on full power. Let me know if I can help. I may be repetitive some about what we've talked about, it's hard for me to remember what all has been said.
I would still seal it off, man. You've got all of this great equipment and the box built, take it all of the way, if you can. I think we talked about port lengths and shortening. Lmk if you want to do that. I would try to seal it off. If you keep the subs and port from pressurizing the trunk, I think that'll help a lot. Just lmk. I'd really recommend sealing it off and trying it on full power, when or if you're able to. I expect sealing off your trunk to help with bandwidth. You're just simply going to be pressurizing less air to a higher pressure. If you cut that port length down, you probably want to shrink the box down also.
Without the box sealed off, can you push the box any further towards the back of the trunk?
I'd say the sharp drop off is a combo of this:
1. Forward firing box
2. Box not sealed off
3. Not full power yet
4. You have a good sized port area (for the very high power levels)
5. Lower tuning, of course.
Just some things to think about. It'll be interesting to see it on full power. Let me know if I can help. I may be repetitive some about what we've talked about, it's hard for me to remember what all has been said.
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Jonnyswboy
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I'm in a trunk build only group and it's about 50/50 people saying sealing will gain, so I will test both ways and act accordingly.
Unfortunately I can't push the box further back because the battery will be behind it. I do think the bandwidth will get better after sealing and on full power. I didn't really test that far bellow tuning as I only had them powered for a few minutes, but I wouldn't be surprised if it still has compression down to the high teens.
Once I am on full power and sealed I will let you know what kind of bandwidth and clamped power I am getting and post more videos. It's going to be a whole different beast on full power I can't wait. Honestly after hearing the lower tune it has definitely grown on me, I love the wind.
I really appreciate you working with me from start to finish!
I try! I do my best from behind a computer screen haha.
I'm not saying sealed will gain peak SPL, I think it may gain overall SPL across a wider bandwidth.
From my experience, you have to have a certain amount of power to run walls and trunk blowthroughs properly, especially when the cabin is sosososo much bigger than the box, in this case. You have to load that cabin air really well, because you don't have loading walls all around the box. There may be a certain amount of power where the box comes alive, where it starts fully pressurizing over a wider bandwidth. It's sort of got to have enough power to load itself, if that makes sense. If all fails and you still want it different than it is, lmk, that box is big and we did big as possible like that so you could always shrink it down. It wouldn't be too hard, and your box won't change on the outside, it looks good.
The bandwidth may even be narrow because the subs are so beefy that you're not really driving them yet, with only 1500w. This box is more designed to run at full power, so let's see how it does under full power and maybe some more play time. It seems very apparent to me that these woofers are built to be abused, so you better get to it!
It's difficult to predict how a car will act with the box firing forward. Like, I wonder if the wave is going back into the trunk and getting stuck in there, or if it's causing any kind of cancellation. That gap around the box is so small, the pressure is higher at the face of the box, but if that air gets in the trunk, I doubt it's going to have enough energy to escape, when it can only escape back around the box edges, it looks like. You could be creating a weird cancellation where that gap around the box could be acting as a port, and the trunk an enclosure, being accessed by those gaps.
You could just stick some of that deadener to the face of the box to the car metal. Not sure if it would stay that way....you could do high density foam since there's deadener everywhere, and then you could put deadener over that to seal it. The foam would keep the deadener from pushing in, some. You might have to get creative with it. High density foam is fairly strong, at least the kind I filled my entire hatch was. Just some thoughts.
You could just stick some of that deadener to the face of the box to the car metal. Not sure if it would stay that way....you could do high density foam since there's deadener everywhere, and then you could put deadener over that to seal it. The foam would keep the deadener from pushing in, some. You might have to get creative with it. High density foam is fairly strong, at least the kind I filled my entire hatch was. Just some thoughts.
If you put a lot of weight in your doors and on your roof, that will help too. Those subs are gonna try to push everything out, the heavier the doors and roof are, more of the sound will stay in the car. You don't want your roof and doors acting like a passive radiator.
Kickstand
CarAudio.com Veteran
I had 2 layers of hush mat and a bunch of rolled up carpet underlay in the doors, back panels, deck lid, pretty much anywhere i could fit it on my cobalt
The back end began to sag from all the weight so I had to put coilovers on to get that nose down look again
I sprayed the roof with spectrum sludge which was a great product but that was years ago not sure if they still make it or not
The back end began to sag from all the weight so I had to put coilovers on to get that nose down look again
I sprayed the roof with spectrum sludge which was a great product but that was years ago not sure if they still make it or not
The 5 Lishen cells in my truck are at 13.96 when my truck is on. It's 110° outside as well. When I charged them out of the truck the charger would charge the 5 cells up to 14.2v and then stop. I've seen 5 cells at the shop on a charger at 15.2v and then we took it off the charger. That charger didn't have an automatic stop point. 5 cells is perfectly fine for a standard system, IMO! I ended up putting a piece of all thread to raise the negative from the bottom buss bar to make it easier to connect to.
Of course it is, trunks are notorious for this phenomenon and box position in the trunk is going to make some dramatic differences in your response curve. At what frequency it is causing peaks and nulls is going to be the only point to try to measure and correct as needed.
So what picks up the difference between 37hz and where your midranges pick up or do you only use slowed or re-mixed music?
Also subs like that with high motor force are going to play extremely peaky over a tight bandwidth. You can get flat response by using a too-small box and sacrificing efficiency or just pick a narrow bandwidth that works for you and enjoy the huge output where you can get it.
A dude up my way just got a couple in some kind of tiny clown car and they take power reasonably well but get really hot and stinky rather fast on 6K each. I suspect you'll be running into mechanical limits before thermal limits with 12" versions though.
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Jonnyswboy
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Yeah since I can't move the box because it's so big I'm guessing sealing it off is going to be the thing that has the most dramatic effect on my response curve.
I only listen to rebassed music in my car. I go to my computer and put on my Sennheisers when I get the SQ itch.
To be honest I'm pretty content picking and choosing songs within my ~10hz window and enjoying the output. With a box this large I agree I'll probably hit mechanical limitations first. In a few months I might play around with the idea of lowering the internal volume and raising the tuning a little.
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