System not like I expected?!

[thehardknoxlife 10+ year member]

To answer one of your questions. Upgrading the alt is more important than the battery imo, but you need to have proper alt power and reserve to be honest. I strongly dislike the box design. 2 ports for one chamber is just asking for problems.

No it's not, well, not if it's properly designed.

Ok so I went through the math AGAIN lol. and it all adds up Ill got through it with you guys.
Ok the TOTAL INTERNAL volume of the box is 5525 cubic inches (13"Hx17"Dx25"W) or 3.2 CuFT. These dimensions are internal correct?

My port has a volume of 1140.75CuIN (13"Hx29.25Lx1.5"W Times 2 for two ports) The 1.5 includes the wood thickness correct (assuming you used one of the outer walls as a port wall)

Take the total volume and subtract the port volume and you get 4385CuIN or 2.53CuFT.

Now minus the displacement of the sub .15CuFt

In the end the NET INTERNAL volume is right about 2.5 and with the 2 vents at 30" puts me right around 35Hz.

So what could it be. Could it be my electrical system?

I get 2.0 at 40hz with a 1.5" port opening and 2.3 @ 27hz with a .75" port opening(assuming you used .75" wood for the walls). I have a feeling your box design is the culprit. Show us a diagram.

 

[Chriszle 10+ year member]

No it's not, well, not if it's properly designed.

I get 2.0 at 40hz with a 1.5" port opening and 2.3 @ 27hz with a .75" port opening(assuming you used .75" wood for the walls). I have a feeling your box design is the culprit. Show us a diagram.

I have never seen or heard a setup with 2 slot ports on opposite sides of the box with only a single chamber meter well or sound good. If I can be proven wrong, then I stand corrected.

 

[thehardknoxlife 10+ year member]

I have never seen or heard a setup with 2 slot ports on opposite sides of the box with only a single chamber meter well, or sound good. If I can be proven wrong, then I stand corrected.

I've done it numerous times. It's not any different than having one big port as long as the sub is centered between them. Theoretically that shouldn't even matter as the sub will create positive and negative pressure that will distribute evenly in all directions.

 

[Chriszle 10+ year member]

I've done it numerous times. It's not any different than having one big port as long as the sub is centered between them.

Have you metered the dual port setups, and metered them compared to the exact same box with 1 larger port? And since metering isn't that important to me, have you compared the sound quality and loudness to the ear with both? My guess is if the change is negligible, than it may not be the best orientation to begin with.

 

[thehardknoxlife 10+ year member]

Have you metered the dual port setups, and metered them compared to the exact same box with 1 larger port? And since metering isn't that important to me, have you compared the sound quality and loudness to the ear with both? My guess is if the change is negligible, than it may not be the best orientation to begin with.

I haven't thought about that much to compare side by side, especially on a meter, but I have made 100's of boxes and quite a few have had dual ports. No one has complained and I haven't either. There probably is a small difference between the two on a meter but it wouldn't be more than a few tenths give or take, it'd be very inaudible. It wouldn't be any different that flipping a single port box the other way or placing a 1/2 cut PVC pipe on the box near the port. SQ will not be affected at all as long as the ports are facing the same direction and aren't way too far apart.

 

[dbeez 5,000+ posts]

Now when you were figuring poty displacement did hou figure the inner por port wall as .75x heightxlength as it has a displacement as well on both sides my guess is you are actually closer to 2 cubes and tune mid to high 40hz will check measurements later as I am on my phone right now.

 

[Villainstone 10+ year member]

When I was figuring port displacement I don't think I figured wall thickness in. I believe I just figured in port volume. So that would lower my net volume thus increasing my frequency?

 

[mazdakid 5,000+ posts]

If your box is smaller than you thought and your port stayed the same size and length then yes youre tuned higher than you thought.

 

[Villainstone 10+ year member]

But will that really take away from the sound. Even if the tuning is off how will that cause me to need so much gain? How much sub sonic filter should I use, same with the phase knob, where should that be set.

 

[hispls 5,000+ posts]

That right there may be your problem. Is your enclosure ported or no? If it is not ported, then 1.5in is way too thick for an enclosure. You want some flexibility on your walls so your sub has more room to move that air. I try and make my boxes so the two side walls expand about 0.15mm, which gives me about an extra 1.25mm flexibility in my sub foam. This gives me better sounding thumps and after-tones, but slightly less return-response (not noticeable)
If it is ported, your sub may not be moving the "box air" properly. I suggest you try a different type of port. Instead of just a hole or a tube that protrudes inside the box, try a bi-force port. It is basically 2 @ .5" ported holes with J-shaped tubes stemming out from them. The two port ends are connected to a T joint with one port hole as a result. The two air ports force eachother to expel only a certain amount of air out of the resulting port, and you can adjust this. This allows for a tighter bass and more response. This method may sound ridiculous, but it is the same method used to make motorcycle racing exhaust pipes. Mechanics use backpressure and stroke pressure to make the highest-performing pipes (sound included)

This is some of the worst information I've seen posted on this site this year.

Sorry, its hard for me to explain. But, I was just giving an idea that I had tested successfully with my professor, no need to bash on me. And I had .15mm wall flex, not .5mm, mistype.
The flex method involves "the control of expanding and contracting of the walls in order to control the expanding and contracting capabilities of the sub". You are able to use the (expanded wall's) contraction force to your advantage.

For the U-port, it just has to be done to be shown. To sum it up, it tries to keep a constant air volume in the box, and moves air in and out ONLY when it needs to (like a vent). It's trial-and-error for the calculations and hands-on attempt.

Providing you could "tune" the walls to resonate out of phase with the woofer it would probably gain, but this would never sound good and it would be impossible to pull off. Port isn't trying to circulate air out of the box, it is supposed to vibrate the column of air within the port. If port is puffing gusts of air out it is unloading and not adding anything to output but possibly noise.

IDK why but now that you mention it I think that I did 2.5 gross not net. I hope not. Yeah sure my math is right but for the wrong **** dimensions. Ill have to check but the more I think about it the more I think the gross volume is 2.5 and I wanted that as my net. Post back after I check

The volume of wood and port counts against you.

I've done it numerous times. It's not any different than having one big port as long as the sub is centered between them. Theoretically that shouldn't even matter as the sub will create positive and negative pressure that will distribute evenly in all directions.

The problem I see with 2 ports (besides multiple point sources) is that they both are so narrow they likely are not functioning properly. Width vs height ratio is far too high with a design like this. Also I see that the box has the hole from trunk to cabin so constricted that likely not much sound is able to escape from the trunk.

After all is set and done my gain is at about 60%, that seems high to me when my amps RMS is nearly double the RMS of the sub. The bass boost which I would rather not have to use is about 50%. Subsonic filter in in the at about 25%, LPF is about halfway. I dont have a DD, DMM, or an O-scope. I had to set my gains by ear.

First of all learn what gain and crossovers do. The crossover isn't set to "25%" it's set to a particular frequency!!!

It is also likely that you are sacrificing output for wider bandwidth. It's quite easy to "upgrade" and get quieter but have more output overall when you consider the larger bandwidth.

Good on you for double walling the box. IMO that's about the only thing you did right on this build, but you really should have asked someone who knows what they're doing to make some plans for a proper box.

 

[dbeez 5,000+ posts]

Gain is strictly dependant on input voltage of the rca and not a volume knob and from amp to amp they will need to be set differently.

 

[Villainstone 10+ year member]

I choose this design because I wanted the box to look symmetrical. I submitted a thread asking for input n suggestions but I didn't get any replies. So I decided to just go ahead n build the box because the math worked out. Either way I guess I will just build another box. Maybe I can get feedback this time lol

 

[Villainstone 10+ year member]

Alright I set the Input Lvl with a mm to 35v. The way I came up with this buy taking the the RMS power of the amp (1300) and multiplying it by the resistance (1ohm). Taking that number and finding the square root and getting 36.05. I set the gain at 35 and its right about 75 perfect, maybe 70. I still think that seems high doesnts it? 1300w amp and 750w RMS sub should need very much gain at all.

Could this from poor factory wiring? I will do the big three next month. But could it cause this issue with high gain?

 

[Villainstone 10+ year member]

With the gain set by using a multimeter, the systems pounds. Nice loud deep bass, seems quite accurate. Im not so sure I should build another box. What do you guys think. If I build a single port box would I get a noticeable difference?