AB HD15 Enclosure

[bgowdy 5,000+ posts]

Ok so previously I did ask about this and was told go 4.25+ net on the box. I took the advice and I did 4.25 net with a 7.5" aero, tuned to 36hz. I have the 1500 rms version HD15 and on 3k. this box I have built is to big for the power(testing showed me this). So I came up with this.

3.5 cubes ne, slot port with 16.10 square inches of port per cube, tuned to 36-37hz. I was actually given the advice on the box size from a buddy who is a AB Rep and runs it daily.

Your thoughts. I will say I'm not going back up to 4 cubes net

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[Jeffdachef 5,000+ posts]

Ok so previously I did ask about this and was told go 4.25+ net on the box. I took the advice and I did 4.25 net with a 7.5" aero, tuned to 36hz. I have the 1500 rms version HD15 and on 3k. this box I have built is to big for the power(testing showed me this). So I came up with this.
3.5 cubes ne, slot port with 16.10 square inches of port per cube, tuned to 36-37hz. I was actually given the advice on the box size from a buddy who is a AB Rep and runs it daily.

Your thoughts. I will say I'm not going back up to 4 cubes net

was it bottoming out before? Does it bottom out on lower notes or upper notes? Or did it get smelly? Need to know what actually happened to make you not like the results.

 

[bgowdy 5,000+ posts]

was it bottoming out before? Does it bottom out on lower notes or upper notes? Or did it get smelly? Need to know what actually happened to make you not like the results.

It's getting smelly pretty quick. Of course if I smell it I turn it off completely lol I'm a p*ssy. Not clipping, I'm rarely even turn the volume up high enough. My volume goes to 72 I go to vol 30-32 max and gain I usually won't go past half on the remote with volume at 30-32.

It's been bottoming out since I built the box. No I don't just constantly do, once I discovered it I stopped turning more then 1/2. It bottoms out at like just about everywhere if I get on it. Sub looks all over the place when given a good amount of power, but turned down its pretty good just not loud

 

[wew lad 5,000+ posts]

get a new baffle and use that box for 2 12s lol

 

[bgowdy 5,000+ posts]

get a new baffle and use that box for 2 12s lol

Meh I'll probably just use it as fired wood or sale it to someone local or something. It sounds good just to big for what I want

 

[bgowdy 5,000+ posts]

@hispls; curious how does port noise occur? I'm use to using aeros so have never had a port noise issue. I ask you because your really knowledgeable here it seems. Not saying others are not though

 

[hispls 5,000+ posts]

[quote name='bgowdy']@hispls; curious how does port noise occur? I'm use to using aeros so have never had a port noise issue. I ask you because your really knowledgeable here it seems. Not saying others are not though[/QUOTE]

Too much velocity of air in the port, from too little area.

Google "canon toroid smoke" click images and see some illustrations of what happens to the airflow. Those donut shaped smoke rings are pretty much what you're hearing. The term "chuffing" is a pretty good onomatopoeia for what it is.

As you can imagine, flaring the port opening reduces what you see in the image search as will a larger port which will reduce velocity. Too small of a port to the extreme would be if the cone is displacing more volume of air than the port holds at which point you have a "leaky sealed box". Mainly it comes down to displacement so if you have a lot of cone area or push the cone area you have to high excursion (playing really low notes) you'll really need to be more wary about keeping adequate port area.

Really the conventional wisdom for port area in the last decade has been towards overkill. For practical purposes you can typically get away with a lot less than what most folks use, though it's hard to get in trouble going "too big"

 

[bgowdy 5,000+ posts]

Too much velocity of air in the port, from too little area.
Google "canon toroid smoke" click images and see some illustrations of what happens to the airflow. Those donut shaped smoke rings are pretty much what you're hearing. The term "chuffing" is a pretty good onomatopoeia for what it is.

As you can imagine, flaring the port opening reduces what you see in the image search as will a larger port which will reduce velocity. Too small of a port to the extreme would be if the cone is displacing more volume of air than the port holds at which point you have a "leaky sealed box". Mainly it comes down to displacement so if you have a lot of cone area or push the cone area you have to high excursion (playing really low notes) you'll really need to be more wary about keeping adequate port area.

Really the conventional wisdom for port area in the last decade has been towards overkill. For practical purposes you can typically get away with a lot less than what most folks use, though it's hard to get in trouble going "too big"

I see... So what I came up with is 3.5 cubes net with 53.44 inches of port =15.28 sqin per cube. Port is 3.75 wide x14.25 height. Is that enough to possibly avoid port noise. My laptop is down so I don't have access to Torres or anything like that.

 

[hispls 5,000+ posts]

I see... So what I came up with is 3.5 cubes net with 53.44 inches of port =15.28 sqin per cube. Port is 3.75 wide x14.25 height. Is that enough to possibly avoid port noise. My laptop is down so I don't have access to Torres or anything like that.

Should be plenty. The whole ratio of square inches to port is nothing scientific and implies you're using adequate box volume for whatever cone area you have, and it's mainly used by manufacturers trying to simplify calculating tuning.. If you put that 15" in an 8 cube box 8" round port would still be plenty (about 60 square inch), but if you put it in 1 cube a 3 inch round port might look like a good ratio but would sound like you're blowing across the top of a coke bottle.

 

[bgowdy 5,000+ posts]

Should be plenty. The whole ratio of square inches to port is nothing scientific and implies you're using adequate box volume for whatever cone area you have, and it's mainly used by manufacturers trying to simplify calculating tuning.. If you put that 15" in an 8 cube box 8" round port would still be plenty (about 60 square inch), but if you put it in 1 cube a 3 inch round port might look like a good ratio but would sound like you're blowing across the top of a coke bottle.

i see... thanks for the insight. I just figured that it would perform better with a generous amount of port. i was told they like their port.

 

[hispls 5,000+ posts]

i see... thanks for the insight. I just figured that it would perform better with a generous amount of port. i was told they like their port.

No doubt more port area is better, but you're far from having trouble from being too small I'd say. In fact I've found that after a point skimping a big on port area for more box volume if you're tight for space is actually the better tradeoff.

 

[bgowdy 5,000+ posts]

No doubt more port area is better, but you're far from having trouble from being too small I'd say. In fact I've found that after a point skimping a big on port area for more box volume if you're tight for space is actually the better tradeoff.

i mean i have some space if need be right now in my car. But its obvious the sub is not happy in the current box, and im trying to giving it a bit over rated power. The 4.25 that it its in seems like its not peforming at its best and seems to heat up rather quick, though im over powering it but i think with the power, smaller box will yield better cone control(i know it doesnt increase rms of the sub it self). I just think that it will perform better, also a bunch of other AB guys again told me before i built this to go 3.5 net smh. i guess i should have possibly listened to them lol. but i wanted to do it all myself

 

[hispls 5,000+ posts]

i mean i have some space if need be right now in my car. But its obvious the sub is not happy in the current box, and im trying to giving it a bit over rated power. The 4.25 that it its in seems like its not peforming at its best and seems to heat up rather quick, though im over powering it but i think with the power, smaller box will yield better cone control(i know it doesnt increase rms of the sub it self). I just think that it will perform better, also a bunch of other AB guys again told me before i built this to go 3.5 net smh. i guess i should have possibly listened to them lol. but i wanted to do it all myself

So are you running into mechanical or thermal limits? Where are you tuned? Are you using subsonic filter correctly? How much power are you trying to throw into it? Either way, 3.5 to 4.25 cube difference shouldn't be a dramatic difference. IMO 3.5 cube is very small for a 15".

Shrinking the box isn't going to magically make that sub handle more power. If you restrict cone movement you're actually limiting cooling. If you are shrinking the box just for the sake of limiting cone movement you might as well have just turned to volume down until you're not reaching mechanical limits or start correctly using HPF. Larger or smaller box effects efficiency and low extension. (one at the expense of the other) and will also change the Q of the system. If it's really peaky shrinking the box may tame that a bit (at the expense of efficiency and low extension), if it seems over damped and doesn't extend low well a bigger box may help, but that cone can only displace so much air before it reaches mechanical limits no matter what you do and it can only shed so much heat before meltdown.

Lastly pics of the box as it sits in the car would help. Often more dramatic changes can be had from different orientation of box/subs/ports than small size adjustments.

 

[bgowdy 5,000+ posts]

So are you running into mechanical or thermal limits? Where are you tuned? Are you using subsonic filter correctly? How much power are you trying to throw into it? Either way, 3.5 to 4.25 cube difference shouldn't be a dramatic difference. IMO 3.5 cube is very small for a 15".
Shrinking the box isn't going to magically make that sub handle more power. If you restrict cone movement you're actually limiting cooling. If you are shrinking the box just for the sake of limiting cone movement you might as well have just turned to volume down until you're not reaching mechanical limits or start correctly using HPF. Larger or smaller box effects efficiency and low extension. (one at the expense of the other) and will also change the Q of the system. If it's really peaky shrinking the box may tame that a bit (at the expense of efficiency and low extension), if it seems over damped and doesn't extend low well a bigger box may help, but that cone can only displace so much air before it reaches mechanical limits no matter what you do and it can only shed so much heat before meltdown.

Lastly pics of the box as it sits in the car would help. Often more dramatic changes can be had from different orientation of box/subs/ports than small size adjustments.

I see currently i dont have and pics of the box, also orientation is limited due to the dimensions of the box. I the trunk it has decent space but getting it in through the trunk was fun to say the least. I dont have issues with playing the low end. Itsd tuned at 36hz and ive played down to 28 with it and it sounded good. Now playing higher i run into a issue were it sounds like it bottoms out. I can only play up to say 40 and then it begins to sound as if its bottoms out if i play more then like half power. Idk if thats the peakyness in effect but it dont like the sound and it scares me lol.

I completely understand the concept that when you shrink a box it doesnt increase the power handling, also i know the bigger enclosures are more efficient as well and smaller boxers are less efficient. Also with lower power i notice people run larger enclosures vs smaller enclosures guys tend to have more power then sub-x is rated.

I know about of guys that are Team AB/AB Dealers and all run their HD15s in smaller enclosures due to the amount of power then run. Im not saying that it will fix the issues i just figure it would be worth a try. I tried going bigger and it seems to not like it very much, and i know the amount of port should be fine at 11 sqin per cube(7.5 in round port). The subs seems to heat up kind of quick seeing that im not just giving it hell.

As far as the amount of power im throwing at it, my amp is rated 3k @ .5ohm which im running currently, im not sure were my sub sonic is et at honestly. I dont play to low under tune. Usually 32 hz is my lowest i will go and im tuned at 36hz. Idk if its mechanical limit or not, it just heating up rather quick for me to be babying the sub

 

[hispls 5,000+ posts]

I see currently i dont have and pics of the box, also orientation is limited due to the dimensions of the box. I the trunk it has decent space but getting it in through the trunk was fun to say the least. I dont have issues with playing the low end. Itsd tuned at 36hz and ive played down to 28 with it and it sounded good. Now playing higher i run into a issue were it sounds like it bottoms out. I can only play up to say 40 and then it begins to sound as if its bottoms out if i play more then like half power. Idk if thats the peakyness in effect but it dont like the sound and it scares me lol.
I completely understand the concept that when you shrink a box it doesnt increase the power handling, also i know the bigger enclosures are more efficient as well and smaller boxers are less efficient. Also with lower power i notice people run larger enclosures vs smaller enclosures guys tend to have more power then sub-x is rated.

I know about of guys that are Team AB/AB Dealers and all run their HD15s in smaller enclosures due to the amount of power then run. Im not saying that it will fix the issues i just figure it would be worth a try. I tried going bigger and it seems to not like it very much, and i know the amount of port should be fine at 11 sqin per cube(7.5 in round port). The subs seems to heat up kind of quick seeing that im not just giving it hell.

As far as the amount of power im throwing at it, my amp is rated 3k @ .5ohm which im running currently, im not sure were my sub sonic is et at honestly. I dont play to low under tune. Usually 32 hz is my lowest i will go and im tuned at 36hz. Idk if its mechanical limit or not, it just heating up rather quick for me to be babying the sub

Realistically the coil in that can hold 1200W continuous power tops. Even at, say, 20% more power, (1500W) you start building up heat very quickly compared to how fast it can cool. You very well may have some frequency ranges where the sub is seeing over 1000W.

As far as reaching x-max with a single 15 at 40hz that's tough. The port provides plenty of spring/control right @ tuning but unloads outside of that. Obviously as you approach 50 the cone just doesn't need to move as far so it's a non issue.

Try this. Cut up 2 and a half 8 foot 2X4's into blocks the length of one side of your box and screw them in there to take up appx .75 cube (a 2x4 is .29 cubic feet). This will get you closer to the 3.5 cube you think you'll like and also raise tuning for you a bit (best to plug it into some software.... I'm not on a Windows OS now so I can't double check). Ideally if you never play below 32, 40 or 42hz tuning and setting subsonic filter @ 32-34 should let you really wang without running into trouble... tweak subsonic accordingly testing lower frequencies. Between the smaller box and higher tuning it should solve your mechanical issues. You're still stuck with thermal limits of that coil, but with that power you can simply turn it down or play less bass heavy songs if it starts getting stinky until it cools down. You should have a minute or two between smelling it and failure to ease back a bit.

Also bear in mind that you will be going from just fine to hard clip really fast as you're pushing things to the limit which speeds up the heat issues. Consider your amp is making 33V..... (2200W into .5 ohm) and you're chugging along just fine. They give it one more click on the volume knob, you're now asking the amp to make 3100W (likely putting it into a pretty hard clip). That's how fast you can get into trouble!

Anyway, buy a few 2X4's and give that a whirl. Under 10$ and a half an hour to see what 3.5 cube tuned a little higher sounds like.