DR-Max

iTrader: (3)

Ok guys, I need your opinions....especially the DIY box designer/maker in the org.

I am going to get a box made for a single RF Punch HX2 10" sub. I wanted to make a vented box for lower frequency response. I have two links showing 2 graphs, SPL and transfer function magnitude (showing driver dB gain), based on 2 box designs. The aqua line signifies a vented box 2.0 cu.ft., tuning freq. 25hz, vent (1) 3"x13"long. The orange line signifies another vented box 1.0 cu.ft., tuning freq. 35hz, vent (1) 3"x13.30"long. In addition,this is the recommended vented enclosure based on Rockford Fosgates' installation manual. The port on each box will be firing towards the opposite direction of the subwoofer. To elaborate on this, the sub will be firing towards the rear of the trunk, while the port will be firing towards the armrest opening of the rear seat. The box will be located right behind the rear seat, under the rear deck.

Which box will sound best in the Maxima trunk? Any suggestions are welcome.


SPL graph:


Transfer function magnitude graph:

2 Da Max

iTrader: (2)

well if you have it in a sealed box you will get better sq. but if you port it right, it should pound a little harder. since its a 10 i would get a vented box to get all the power out of it

DR-Max

iTrader: (3)

I was using this software to give me a visual of how a sealed enclosure would sound and sadly, a sealed box won't just get me low enough at a flat response. As a matter of fact, 80hz is at around -4dB, up slightly at 60hz, then rolls off progressively on lower frequencies. It's been said that you get a free 12dB/octave cabin gain (inside the car) to any subwoofer design, starting from a corner frequency that is dependent on the size of the cabin (the larger the cabin, the lower the corner frequency). Typically this corner frequency lies between 60 Hz and 80 Hz. So in theory (based on this free box designing program that I am using), a sealed box that is 2.5 cu.ft. would give the following: 80hz -4dB, 60hz -4dB, 25hz -10dB. SPL showed to be around 105 dB. In-cabin gain would give a boost of around 12dB more around 60 and 80hz. With the exception of better SQ (which I don't know how much better), a vented box which is half its size goes deeper and louder. Still this is all theoretical based on the box designing program. I'd like to here more input from those who are currently using vented systems.

03SE2HEAR

I know the HX2's love ported enclosures. Keep the port on the same plane as the woofer though. Here's what I suggest....call RF's Tech Support on their toll-free line (they don't mind) at 800-669-9899 and press Option#3 for Tech. They have come up with some crazy stuff for me that's worked wonders. They are using Term-Pro, but have all of the TS perimeters built in to give you what you want for what music you want to listen to. Be sure you tell them what your intention is...SPL, SQ, etc. Personally I've heard that Bass Box Pro enclosure program is better, but why not get the enclosure design directly from the horse's mouth? The suggested enclosures on their spec sheets haven't worked for me in the past. I think the HE, HE2's & HX2's all have the same recommended enclosure perimeters in their literature. Give'em a call.

DR-Max

iTrader: (3)

Thanks...that is the indication I got from WinISD when I entered the T/S Parameters of the HX2 manually. There's this thing called Efficiency Bandwidth Product (EBP) bar indicator which determines which box type is best suited for this particular driver. If the bar is high, then the driver is best suited for installation in a vented box (or a 6th order bandpass). Conversely, if the bar is low, a closed type box (or a 4th order bandpass) is better. If the bar is near the center, then the driver will likely perform equally well in either a closed or vented type box. The HX2 showed 68.2 EBP (higher side of the bar), so this particular sub does like vented boxes better. As for the recommended enclosure in the spec sheet, I ran their numbers thru the software (see orange line in graphs below). It looked pretty good, the 40hz region is boosted at +2dB. While there's about -12dB roll off in the 25hz region, natural in-cabin gains will just about flatten that frequency. I don't know whats my thing with 25hz lately but I've been listening to some music that has bass tones around that region and its been irritating me knowing that the former 15" driver I had before made that frequency very audible. A 10" driver just can't go that low w/o any porting. So as long as I can hear and feel down to 25hz, I'm happy.

Thanks for the suggestions, I will contact RF's tech support.

03SE2HEAR

There's a lot of factors that come into play with some of these programs for doing enclosures. Some may sound awesome, others may sound horrible in the trunk. Trying to get it to sound right is a lot of trial and error in some cases. You're on the right track, call'em. They should be able to hook you up...that's why they get paid the big bucks.

Terran

iTrader: (6)

2_Da_Max...2DaMax. It's twins. You even both have beige maxes...this is going to start getting confusing.

DR-Max

iTrader: (3)

True........but I got seniority!

AscendantMax

iTrader: (7)

do you have a subsonic filter on the amp? if the sub plays frequencies below the tuning frequency of the box, there is very little cone control by the air inside the box...it'll be like free-air at that point. you might risk sub damage.

DR-Max

iTrader: (3)

The only filter this amp has is a 12dB/oct LPF ranging from 32 - 320hz. Interesting point you brought up which I totally overlooked, the sub's frequency range! The HX2 10" sub ranges from 30 - 200hz. So, the lowest freq this sub will probably hit is at 30hz which means I'd have to redesign the box. Currently, my sealed enclosure has a system resonance of 47hz (75 cu.ft. - RF recommended). Forgive me if this is a dumb question but how would anyone filter subsonic response if their amp didn't come with that type of filter? Many high-end amps do but what about those who have something a little less? Would a use of some type of capacitor/inductor do?

DR-Max

iTrader: (3)

OK......just called RF's tech line. Basically, anything below 30hz is inaudible to the human ear, which is something I heard before from somewhere but never really took it as fact. Now I know it is! I think the music that I have been listening to seems to have fooled me into thinking that the bass notes that were pronounced when being played back on my previous 15" sub system was in the 25hz region, I'm probably wrong. I'll find a spectrum analyzer program and see what frequency it is. Anyhow, the tech recommended that I tune the vented box at 45hz. The 10" RF HX2 performs optimally at this frequency. Also, placing the vent facing the opposite direction from the subwoofer is a bad idea, bass cancellation! So the port will be on the same side as the subwoofer. As I mentioned earlier, my current sealed box has a system resonance of 47hz. I ran 0.75 cu.ft. (current box internal volume) and tuning frequency of 45hz thru the box program and the graph looks pretty good...45hz shows a +2 dB gain, and it goes down to 40hz almost flat!!! I can use my current box now and vent it. With the correct vent diameter and length, I'm all set. I'll try this on the weekend.

If anyone is bored and have a box designing program, will you run the same numbers to see if you get the same result I got?

AscendantMax

iTrader: (7)

I'm sure there are some sort of an inline subsonic filter that you can buy that you can connect to the RCA's, but i'm not sure if it'll work as well as ones that are built into the amp. maybe someone with more knowledge in this matter will chime in...

i need to get one as well, i'm getting a ported box built for my brahma.

DR-Max

iTrader: (3)

I called RF again and talked to another tech which gave me another set of numbers. I inquired about the subsonic filter and according to him, you can minimize subsonic response thru box design. Furthermore, the damaging effects of subsonic frequencies is when they are being played at higher SPL which is also probably why many installers do not recommend using bass boost in amps. It boosts a specific frequency which also raises the roll-off of subsonic frequencies unless a steeper crossover slope is being used perhaps 24dB/octave. The tech gave me the following specs for the new box design: 1.1 cu.ft., tuned for 35hz. Subsonic-wise, the roll-off starts from 33 - 30hz, anything below 30hz the sub cannot reproduce. The box will give off a +2dB boost around 40 - 43hz so this box will play nicely at 45hz as well! I'll run it thru my program and tweek it a little to see what I get.

AscendantMax

iTrader: (7)

My concern was when the sub plays stuff below the tuning freq of the box, it can easily reach it's mechanical limits since the air inside the box will no longer act as a spring on the cone. A subsonic filter won't allow any freq (below the mark you set it to) to be sent to the sub.

DR-Max

iTrader: (3)

I made two new graphs showing the recent numbers I got from an RF tech for box design. What he said about the specs he gave me was somewhat dead-on when I ran it thru the program (depicted by the aqua colored line). However, I tweeked it a little to get better subsonic roll-off (depicted by the orange line). Guess what I ended up with, the very same spec that RF indicated as recommended enclosure in their spec sheet. Now I know why, they wouldn't want to be publishing something that could become a warranty issue. Furthermore, the tweek should pretty much perform the same at 45 hz. BTW, I simulated an active LP filtering at 125hz which shows the roll-off curves above 60hz (shown in graph). Respectively, simulating an 80 or even 50hz LP filtering would increase the roll-offs even more. SPL-wise, both designs are pretty much the same.

New SPL graph:


New Transfer function magnitude graph:


Guys thanks for bringing up very good points, it helped greatly! More comments or suggestions are welcome.

DR-Max

iTrader: (3)

I see and I asked the tech the same question about filtering. He said that with filtering or not, frequency roll-offs are by-products of speaker enclosures which is dependent on size and/or porting. There just isn't such a thing as a sudden drop at a given cut-off. Look at the graph below, it simulated a 125hz LP filtering. Despite, there is a roll-off up the frequency band, not a sudden drop. What's good about this 10" sub is that it won't play below 30hz so tuning the box at 35hz won't hurt it much at all.

DR-Max

iTrader: (3)

I just made a graph of cone excursion based on my subwoofer and its box design. I gave it a subsonic signal (just below tuning range) of 34 hz. This bad boy's XMAX is .55". Look at the graph below:



Over-excursion is reached at 25hz, mechanical damage is eminent. Look at 34 - 30hz, way below range. Anything below 30hz, this sub won't simply play it. It can take a lot of punishment! That simulation is w/o using a subsonic filter, purely just box design.

AscendantMax

iTrader: (7)

ah that's cool, maybe i should mess with that program. i downloaded it loooooong time ago, just never messed with it before. i'm worried about my sub over excurting. it has a max of .28mm (~1.1 inch) and that seems plenty!

DR-Max

iTrader: (3)

Also, I wanted to add that power has a direct influence on cone excursion (obviously). I been running several simulations using this software and the only time you really should worry about subsonic filters is when u r pushing anywhere above 600 watts, or even in some cases 800 watts. If you are like me, 300 watts RMS is enough! OK...maybe 500 watts.

Fosgate Fan, seeing that you have a Brahma sub...I know you are pushing some serious power! That's probably why subsonic filtering would concern you more. Regardless, you brought up a very valid point which influenced me greatly on designing my next box.

BTW, if you want me to run your sub thru, give me the sub's model # and your box's internal volume, and your amps output power. We'll see if you are pushing it.

AscendantMax

iTrader: (7)

i don't know about "serious power". i'm only sending about 480 watts to it, and that's plenty for me.

good luck with the box

http://www.adireaudio.com/TextPages/...eFrameText.htm

i have the older mark 1 version, but it's pretty similar to the mark II. mark II versions have like, 1 or 2 mm more of xmax.

DR-Max

iTrader: (3)

Coool.....you have the 12" right? Is it dual 2 ohm voice coils? If so, how are they wired, parallel or series?

AscendantMax

iTrader: (7)

yes, i have the 12" version. dvc 2 ohms wired in series to 4 ohm load.

slickrick

iTrader: (12)

your brahma is laughing at that power. dont worry about it at all unless you clip your amp beyond belief. also i thought the only changes between mark 1 and mark II were coemetic, dutcap, tinsel design, basket.

DR-Max

iTrader: (3)

Hold on, I have to enter the T/S parameters manually, this sub isn't in the database. It won't take too long. BTW, how big is your box? Sealed right?

matt90max

i wouldnt use the port design with your port going threw the armrest, its best to have both port and sub on the same plane firing the same way. the waves will be seperated to much and will probably cause a lot of canceling considing your trying to fill 2 areas the trunk and the cabin. best is totally sealed from the trunk firing into the cabin. or just port and fire back at the trunk lid about 6-8 inches from the back. take out all the plastic and the cardboard on the armrest hole.

you can also use that program to see how your amp will respond to your sub in that box. like when your sub plays threw frequencies it will raise and lower the resistance as the sub moves faster and slower. your sub may have a resitance of 4 at 30hz, and 8 at 35hz. or 2 at 50. depending on how the sub and box is designed you can see how much power your amp will put out at each frequency.

DR-Max

iTrader: (3)

Fosgate Fan,

I just ran it thru with a box volume that the software thought is most suitable. Pushing this monster with your amp. It shows that the cone excursion is 0.6" at the most (at 10hz) progressively declining up the frequency band. I can email you the graphs if you want. If you give it 1600 watts, cone excursion is at 1.1" at the most (at 10hz) progressively declining up the frequency band. At 4800 watts (peak power), serious over-excursion is present starting at 50hz and below. This is based on 0.85 cu.ft. sealed box. Your sub's XMAX is 1.14".

matt90max,
I'm still learning from this software so I'll play around with the features you have mentioned. Just started using this yesterday. As for the port facing the armrest, your right! Major bass cancellation.

AscendantMax

iTrader: (7)

oops, those were the other differences as well

yes, for now it's 1.6 cu ft sealed. new box will be 2.4 cu ft (before sub displacement) tuned to 28 Hz

DR-Max

iTrader: (3)

Fosgate Fan,

Your present box (1.6cu.ft):
480w - .78" at the most from 10hz and below
1600w - over-excursion at 27hz and below (need subsonic filter)
4800w - over-excursion at 50hz and below (need subsonic filter)

Your new box (2.4cu.ft. tuned at 28hz):

480w - over-excursion at 16hz and below (need subsonic filter)
1600w - over-excursion at 23hz and below (need subsonic filter)

4800w - over-excursion at 50hz, 26hz and below.
There's a drop in cone excursion down to .71" between (50 - 26hz). Hope that makes sense.

matt90max

to bad the thermal rating of those coils is not even near 750 watts rms.

AscendantMax

iTrader: (7)

cool, thanks for the data.

DR-Max

iTrader: (3)

Isn't it funny how people market their products throwing out a theoretical number to help it sell. However, I'm sure it wasn't all that hard to sell that subwoofer. Listening to it is proof enough.

matt90max

the only problem with programs like that is they are limited to the drive. the t/s specs you entered where obtained by tests on that sub. they dont tell how the sub will act with large amounts of power and are probably tested in the box they recommeneded. winisd gives you a box related to your t/s specs and gives you information on how the driver will act if it can keep those t/s specs threw the whole response curve and with any amount of power. if you had a perfect sub with coils that can handle any power then that program would be more acurate.

DR-Max

iTrader: (3)

No problem, I'm having too much fun with this thing. Too bad its a freeware version, some features are disabled such as what matt90max had mentioned.

matt90max

try winisd alpha pro

DR-Max

iTrader: (3)

Like everything else, nothing is for sure in this world. Even, science is based on best guesses.

DR-Max

iTrader: (3)

I have Alpha pro ver. 0.50alpha7 [11.09.2004], the graph has no plots when I select "AMPLIFIER APPARENT LOAD POWER (VA)".

matt90max

press tranfunction mag... and go to driver sub catagory and impedence

DR-Max

iTrader: (3)

Fosgate Fan, you are probably wondering how loud you new box should sound? I was wondering too. Based on your current amp power of 480w, you should be at 113.6dB @ 31hz, then rolls off down to 111.2dB @ 85hz. Still, it'll be a pretty loud set up. Right now your sealed box's system resonance is @ 39hz showing it at 106.6dB, at 31 hz it shows 104.3dB. Your new box will be almost 10dB louder!!! Maybe you should think about bracing your rear window.

My box will be at 111dB @ 41hz and about 7dB less than you @ 31hz with 300 watts of amp power. But my sub is sub-par from yours. I wonder if I can calculate system distortion? Just gotta keep playing with this program.

AscendantMax

iTrader: (7)

wonder if i can get it to the 130's

looks like i need an amp upgrade

matt90max

those db are without thinking about if your putting it in a trunk or in a small cab pickup truck. your car/truck will work as an enclosure outside the sub enclosure and add db, it also depends on where your are reading the db from. near the windshield will be much louder then where your head is in the drivers seat. and your db reading will only increase 3 db if you double your amp power..