I need help on building a ported subwoofer box

**pomz23** · 05-08-2009, 03:40 PM

your talking about a few things that im clueless about. Im pretty technical but when it comes to technicality of sound and electronics related, thats out of my knowledge. Im just going with what seems logical. = 2 subs hit harder than 1. Now if you are telling me that its not worth it, than that's news to me. I listen mostly to rap with the subs, and for classic rock, I can lower the subs and between my headunit and speakers, the highs sound very good in my car. I work at a cabinet shop and I program a CNC machine, so building a box is no problem for me. I am also looking for that "wow" factor in my sub/box combo. IMO, im taking the car to shows, one sub, just looks like I didnt have the cash for a second one. I like the L7, they look sick, and from what I was told they hit excellent. Maybe someone has a recommendation for another sub that doesn't cost crazy $$. Im not looking to spend more than 150 for a sub, and Im shopping on ebay, and have found great deals so far.

Originally Posted by bes51659

It is about moving air. Two subs will shift the double amount of air. Double volume is 3dB. If you want to know how much 3dB is, let someone increase volume and say "stop" when you can tell that the volume has indeed increesed. That is 3dB.

On the other hand. Some elements will give 91dB and others 94dB per Watt and save you the space of one bass.

Apart from moving air, it is also about transient responce, dampfactor,and what kind of music you are listening too. That will dictate what box type you need. Like a bass-reflex is not very good when you have very low frequencies. There is no control of the cone below its turn over frequency, but you get better bass just over that freq.

2 more cents: why do people parallell connect elements down to 1 ohm and get fladder-bass without punch what so ever?!? And monster cables to avoid to high loss? In case you do not prefer brummm to punch.

Well, if I'm made you think and not automatically do what every body else does, I'm happy :-)

**bes51659** · 05-08-2009, 05:42 PM

Technical or not, it has got something to do with what you will hear in the end.

I agree they look good. And they will do fine in quite small boxes.

Just a link to a very nice looking bandpass box Advantage is that it will still work below turnover frequency and not just move air from cone via port to reverse side of cone. But maybe you think that looks impressive? (sorry, I could not resist) They are hard to build but you seem to have all the tools. But L7's are made for ported systems I think.

Do I dear suggest that you connect them in series to an amp made for 8ohm output? Well, if you do get a low ohm amp you can still try it and connect it back and then tell me its mumbo jumbo. That goes for the rest of you guys too.

btw. What do you think hits hardest? 2x12' or 1x15' ;-) Or 2x10' / 1x12' for that matter. Someone even wanted to go 4x8'. Very interesting acctually. To my experience that will sound great but not send anything down your spine. Disagree?

**thewizard** · 05-08-2009, 05:50 PM

Two subs are not at all a necessity. This is coming from a guy that "used" to run multiple subs in every installation that I ever did, and it wasn't loud enough if it couldn't produce over 148db. I lived and learned the expensive way. Multiple subs are waste of space and money these days. I run a single DD9510 10" sub in a ported box driven by a true 3200 watts and a few runs of 1/0 wire. The sound quality is incredible and it will exceed 150db on the termlab, takes up very little space, and is not even visible in the truck unless I want it to be. It all depends on your box, both sound quality and SPL. I can make a piece of crap sub both sound better and be louder in a well built box then you can make a mega buck top of the line monster sub sound in a crap box.

**bes51659** · 05-09-2009, 03:05 AM

I love you!

**thewizard** · 05-09-2009, 11:51 AM

When you decide on a sub or two post what you have chosen and we will help you design a box to make it perform well. Until you decide no design can even be considered.

**bes51659** · 05-09-2009, 05:29 PM

This was so fun! Your link was great, treeman!

If I had a coupe, I would select a bandpass box and draw the port(s) up the hat-shelf. The box in the boot would then be completely sealed, and not matter what I put in there would not affect the sound. I "might" put plexi there to show off the element (and amp) just for fun. Or let the system be a complete sleeper. Nothing to be seen in the boot. Upholstery to let the sub melt in to the environment. No filters on amp! No need.

I do not have that experience in selecting speakers, but I am weak for Infinity Kappa's and would put a 12' in there. That would get me 28 to 95Hz in a 50l box, but not more than 120dB's if I am not misstaken. How do you reach 150, wizard!? Do you count in the boost you get due to car compartment?

Drawback: 1) The relatively low upper turnover freq would require a very good front set. 2) 2x 20cm 3,5m ports :-) I have probably selected wrong element.

Oh, sorry, forgot. It wasn't me that wanted help with a speaker...

**thewizard** · 05-10-2009, 09:45 AM

Hitting high spl requires finding the resident frequency (the frequency that your vehicle will produce better than any other) and tuning your box to that frequency. In my case I lucked out because my resident frequency was almost the same as what I wanted to tune my box to in the first place. It requires a lot of work and a lot of time. In my case I wasn't really going for an spl build, that was a just a side effect of the equipment that I am using and an efficient box design. My current box is the fifth box that I have built for the same truck and sub, and finally got the right combination and box design that works in the truck. Just for the record I do have to make a few changes to this setup to achieve that high spl. It is setup for sound quality most of the time as it is my daily driver, for spl I have to change the sub wiring around a bit which forces the amplifier to produce much more power, and also have to change my port tube length to raise the box frequency. I run my bass amp at 2ohms for daily driving, but can run it as low as a 1/4ohm for spl burps.

Just wanted to add something here, some vehicles are much better for spl than others and it all depends on what the resident frequency of that vehicle is. If the frequency is too high or too low than it may not be as good for achieving a high spl as others. My spl competition days ended about 10 years ago, but I still do show up the odd time to play. My hobbies over the years have yielded some permanent hearing damage, as safety was not always a priority back then.

**bes51659** · 05-11-2009, 05:15 AM

Great read from someone that knows what he is talking about! (sorry to hear about hearing damage. It is when you get a bit older you pay the price with tinitus and stuff I guess. When young you think you will live for ever)

Q1) My belief is that having the ports entering the coupe below the rear seat or preferably in hat shelf (correct wording?) is better than just relying on bass comming thru rear back seat. Do you agree? If entering at hat shelf I might even get a positive effekt from the "horn" that is formed by hat-shelf and rear window. Maybe that has to be considered when designing the box?

Q2) What should I look for in an element intended for a bandpass box? I though any element for a sealed box would do well. Same selection qriteria.

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