Extremis as a car "woofer"

CJ Paul · « **on:** 12 May 2005, 09:18 pm »

I normally post over at home theater talk, but I thought I'd mention this here as well since I ordered from DIY Cable. I'm building a small "woofer" for the stereo in my truck. I'm basically just trying to get another octave out of my components in my truck. I'm using the Extremis midwoofer in a small sealed enclosure and I'm hopefully installing it tonight and will do a write-up on the results. If I can even get down to 30hz (which I'm sure I can) I will be more than pleased. I'll probably try to take some SPL readings if I get a chance.

I used a small piece of sonotube and cut some plywood endcaps. I've made a 2" port tuned to about 35hz but I'm going to run it sealed for a while just to see if I even need to port it. I have about $11 in the enclosure so it was a pretty cheap project.

mcgsxr · « **Reply #1 on:** 12 May 2005, 11:40 pm »

I would bet that the cabin gain inherent in car audio, will have you keeping that in the sealed box - I always ran sealed subs in cars, since the balance of the enclosure roll off, against the cabin gain, always seemed to work well for good sound.

Note, I am not saying for booming, but for good sound.

Let us know how it works out!

CJ Paul · « **Reply #2 on:** 13 May 2005, 02:25 pm »

I ran it sealed for about an hour and was having problems matching the output to my mains, but I hadnt stuffed what is actually an undersized enclosure yet. When I took the driver out to add the stuffing I decided to install the port at the same time. I can always plug the port if need be. I'm not sure the driver is even broken in yet. It hits very hard on rap/hip hop/hard hitting bass, but rolling bass lines are not quite as articulate as I'm used to with an ULTRA low Q sealed sub in my home stereo. I'm thinking its because I'm truly pusing the limits of small enclosure size and I may just have to live with it. It was a little sloppy when it was still sealed too, so its not the port. And when I say sloppy, that's not an indictment, but rather it might accurately be put as tighter than 80% of the subs you hear in cars, but not as tight as I'm used to.

Overall it sounds great and I am very happy. It provides a ton of overall output, with one caveat. It is not as sensitive as my components, so I've got the gain on MIN for my components and on MAX for the sub plus I have the sub output on the head unit all the way to +15, so I have no where else to go from that standpoint. Its a good thing at that setting the sub just happens to pretty much line up with the mains or I'd be SOL.

This is really only my third experience with car subs and my first one didnt count because I knew nothing. I had two 15" MTX Road Thunder II drivers in a dual chamber box with about 3 cu/ft per sub

that took up the entire trunk of my car in HS. Then I helped my brother integrate an infinity kappa perfect 10 in his civic which is basically a really great setup, but having a trunk, he has room for the proper enclosure size, etc. And then this sub. I have built my own home theater sub though in between, so my experience is growing. My SPL meter is packed away so I cant really graph the output, which would be helpful if I could discover a hump in the FR since my head unit does have a limited parametric EQ in it. However, I am slightly afraid that if I lowered a hump, I might lose enough output that I wouldnt be able to bring the levels back up to match the mains. At this point its a matter of getting used to having a sub in the car again, waiting for the driver to break in, and then tweaking it to taste.

I'd like to thank Kevin again for his help with the project.

Kevin P · « **Reply #3 on:** 13 May 2005, 06:13 pm »

CJ,

Sounds great.... thanks for sharing your experience. I'm surprised that you need that much gain. I'd double check your wiring etc... because most amps give you at least 30db of gain adjustment. It's hard to believe you are using all of that and still not matching up to the rest of the system.

CJ Paul · « **Reply #4 on:** 13 May 2005, 06:28 pm »

I'll double check, but my head-unit has a 180 degree phase reverse setting on it, and in-phase provides more output than reverse phase, so its not a phase issue. Is it possible that the output will increase a great deal as the driver breaks in? Here is my setup. I'm running an Alpine (a few steps up from entry level a year or so ago) into a Pioneer 4 ch amp. Its putting out 50x4 into 4 ohms so my components are each getting 50 watts. However, the extremis is 8ohms so even bridging the other channels, I'm not positive if its getting 120 or 50 watts (the amp actually bridges into 120x2 so that's not a typo). The sub is JUST integrated with the mains, so for the time being, I'm not going to sweat not having more headroom. Can you think of any other wiring issues other than phase that might be causing this?

kfr01 · « **Reply #5 on:** 13 May 2005, 06:58 pm »

Quote from: CJ Paul

I'll double check, but my head-unit has a 180 degree phase reverse setting on it, and in-phase provides more output than reverse phase, so its not a phase issue. Is it possible that the output will increase a great deal as the driver breaks in? Here is my setup. I'm running an Alpine (a few steps up from entry level a year or so ago) into a Pioneer 4 ch amp. Its putting out 50x4 into 4 ohms so my components are each getting 50 watts. However, the extremis is 8ohms so even bridging the other channels, I ...

Just remember, the power the amplifier is capable of producing has little to do with matching the levels...

Your components must be relatively efficient to be producing this sort of a sensitivity matching issue with the Extremis.

Does your head unit have <2v pre-outs? If so, you may want to consider a different head unit with some higher voltage outs. These will allow you to correctly set the gain for the Extremis channels (which is surely not -max-) and reduce the gain further on your mains. I highly recommend the 8-volt Eclipse line for the maximum in level matching flexibility. If you go that route, you may also want to consider an amplifier with more swing on the gain knob than it sounds like your pioneer has. I am actually in the process of installing an Extremis pair in my car as midbass drivers in the front doors. I am using these full-range class D amplifiers that have very nice signal input voltage (100mv to 17 volts) swing: http://www.xtant.com/html/products/xtant1.1i.cfm

If a pioneer from a few years ago it is likely you have 200mv to ~2v on that amplifier.

Head over to http://www.the12volt.com/ for more help with this issue. The car audio forum over there is well moderated and is relatively serious and focused on helping people resolve installation issues.

CJ Paul · « **Reply #6 on:** 13 May 2005, 07:04 pm »

The Alpine has 4v outs. I spent $99 on the driver and $11 on the enclosure. I have no desire to put ANY more money into this. There is a potential that I may try a set of Kit 61s. If, in the next six months that I'm settling into my new house and potentially getting some new woodworking tools, I decide that this isnt working, I'll see if Kevin can swing me a deal on a partial kit 61 and just yank the extremis out of the truck. This is not a full car audio upgrade. I've had all the other equipment in there for over a year and with a new minivan payment, a new house in June and a 1 year old daughter with the potential for another coming along in the next year, I'm not going to be throwing any more substantial money into this. Like I said, its technically matched right now and while I would rather not have either gain cranked to the extreme like it is, I'm not hearing any detrimental sounds from the situation right now. Thank you for the suggestions though.

kfr01 · « **Reply #7 on:** 13 May 2005, 07:12 pm »

Paul,

I certainly understand wanting to cut off spending on a project. Just as an aside... I ---highly--- recommend building the Kit61. It is almost a shame to limit the Extremis driver to only bass duties. It really shines and is quite amazing playing the bass, midbass, and midrange. The sound from the Kit61 is shockingly complete, cohesive, and balanced. The money used finishing the Kit61 is the best performance for the dollar money I've ever spent on audio.

Kevin P · « **Reply #8 on:** 13 May 2005, 07:17 pm »

It's probably not a power issue. More likely it's a gain issue. You only need 120W into 8 Ohms to reach full excursion @ 40HZ with the box design you are using. You get significant SPL at MUCH lower power so even with 40-50W you have enough power for mucho output. I'd guess you need more gain adjustment... not power.

CJ Paul · « **Reply #9 on:** 13 May 2005, 07:20 pm »

Thanks again. Paul is my last name though. Call me CJ. I have heard so many good things about the kit 61s and I'm really hoping to get some new tools this summer. If I can get a table saw out of the way for Fathers day (hint hint, like my wife reads these forums

) then I will probably just go to the hardware store and pick up a new sander, router, and mitre saw to complete the setup. At that point I think I'll be able to put some DIY projects together where I'm more concerned with looks. If I do a set of speakers, I might try the kit 41s first or even just the WR125 full range as a PC speaker. It would give me a chance to try my finish technique. I'm shooting for no visible wood grain, just like a piano black laquer finish, except not black. I think I'm going to shoot for a bright primary color like blue, but I'll need to practice.

kfr01 · « **Reply #10 on:** 13 May 2005, 07:43 pm »

CJ, sorry about the name mistake.

I was originally hoping to do piano black as well, but learned pretty fast that I'd need to do way more priming and sanding than I had time for. The stone spray was very easy and hid some of my imperfections very well. For my next pair I will probably re-attempt the piano black spray, but after my experience with spraying the stands I've learned I'll probably have to invest in a real sprayer (cans were just so hard to get even when spraying).

Also, to your list I recommend adding this Jasper Circle Jig:
http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=365-250

It makes the front baffle cutting a breeze. If / when you finish your Kits give a post, especially if you do the Kit41... or any other design with the CSS4.5". I've been thinking about adding a pair of those in the bedroom and have yet to hear some subjective listening reviews.

CJ Paul · « **Reply #11 on:** 13 May 2005, 07:54 pm »

The jig is already on my list. I've read many build processes over the years and have formulated plans. I think the key is getting a pretty darn good but not perfect finish before you start the laquer. For example, I plan to paint the whole enclosure with shelac before I start the finish. I used some shellac on a flexy rack I built but ran out and switched to primer. The finish on the shelves with shellac is noticibly better and more consistant. I know there is a lot of work involved in high gloss finishes, and I'll probably play it by ear in the end, but I would like to get a non-textured finish if I could. I know why people use textured finishes on DIY projects and so does everyone else, that's part of the problem. I'd like to achieve a finish that stands on its own so to speak.

kfr01 · « **Reply #12 on:** 13 May 2005, 08:05 pm »

Very true on the textured finish. They always look suspiciously or even conspicuously DIY.

I'll have to try your idea of using shelac -before- the finish. It sounds good. I'd like to see a picture of your stands if you have a chance... I've been thinking about a similar project.

bubba966 · « **Reply #13 on:** 13 May 2005, 08:16 pm »

You get a better finish with laquer if you use a laquer sanding sealer to prime with. It also helps if you've got a good airless sprayer (like a Titan 440 or 640) or an HVLP spayer to use to apply the sanding sealer & laquer.

CJ Paul · « **Reply #14 on:** 13 May 2005, 08:19 pm »

Here is a picture of my flexy rack, I made a TV stand too which got donated to my brother when I got the projector.

kfr01 · « **Reply #15 on:** 13 May 2005, 08:23 pm »

Looks nice... I like the idea of getting those components up and out of the way. We're finishing our basement now and I'm looking for easy (read: cheap) diy ways to complete the a/v.