Did I screw something up?

Hi Easy E, bustamove, CVStroker, CT!, et al. After reading a couple of rave reviews on how the 12W6v2-D4 performs in large ported enclosures, I recently decided to undertake a design of a ported enclosure myself. I drive an Audi A6 so the trunk area certainly accommodates a large vented cabinet.

Ultimately, I decided to use an enclosure with a net internal volume, Vb, of about 2.1 cu. feet, just slightly more, some long decimal. This is after woofer displacement and port displacement. As a matter of fact, the external dimensions are 15"H x 27.25"W x 16.75"D. The front baffle is 1.5" thick, the walls are 0.75", and the side walls come in at 0.5". I used 0.25" deep dados in the front, back, top and bottom walls.

Anyway, the vent's cross sectional area is 20.25 sq. in, and the vent length is 36", and the net internal volume of the enclosure is about 3664.1 cu. in. Inputing this data into the tuning frequency formula yields about 25Hz. The minus 3 decibel half power cut-off is about 28Hz. I can give you a link to where I found the formula, if needed. I read some where that the ratio of port height to port width can't be > 9/1. Fortunately, when I finished the drafting and the number crunching I found that my height 13.5" and width 1.5" produces 9 to 1 exactly. Thank Gosh!

Because my father is a fantastic carpenter, I let him undertake the construction. We used MDF that I bought from the local Home Depot, and carpet and speaker terminal I bought from Crutchfield. No Rat Shack this time, LOL!

Anyway, the set up is in the car, it weighs a TON. But, I find that the output isn't as defined as my former 1.25 cu. ft sealed enclosure. My father and I agreed that the output sounds soft when the back seats are closed. This leads me to my inquiry. Did I screw up something in the design? Easy E, CVStroker, bustamove, CT!, anybody?:confused:

I mostly listen to 80s music now, and enjoy that added kick. I'm powering the set up with 500 W RMS. I prefer to have the back seats closed because I don't want the set up to be conspicuous. I have a lot of scrap pieces of Dynamat Extreme stuck onto the metal panels underneath the rear deck that I had left over from several years back. BTW, the rear deck has some vents in it already that links the trunk area to the vehicles cabin. Rear defroster aparatus I guess. Anyway, any input or guidance you guys may give me will be greatly appreciated. I am beginning to think this stuff is WAY over my head! Thank you guys.:)

Guys, I think I may have discovered what the problem is. I seems I over-estimated the structural integrity of the speaker terminal cup I bought from Crutchfield. It being possibly a millimeter thick or so, and being subjected to the intense internal sound pressure most likely reduced the efficiency of the system. The result being the pressure finding the weakest link and oscillating the H, E, double hockey sticks out of it. Anyway, I'm keeping my fingers crossed that the terminal cup was the issue. My dad and I put a couple layers of silicone on it. Hope that resolves the issue.

Oh, BTW, Easy E, I'm sorry if I over reacted in that one thread a while back. I've just been VERY busy. I dropped out of the UC Quarted system, it was just WAY to fast. I am used to semesters since I'm originally from NJ. Anyway, I successfully read my entire Calculus text book in my year long hiatus, and am now reading my Differential Equations text. I'd like to see anybody do that as a past time, LOL! No, but some day I want to be a compotent Civil Engineer. My aunt and father found a school that specializes in the treatment of my life-long disorder, Asperger's. So I'm feeling optimistic about going back to school, with a SEMESTER system this time, LOL!

I know all you guys must be busy. We engineers generally are. Once I'm back in school I'll probably will be MIA from the forums. I'll probably be absent from the forums too when I am studying for the PE, Professional Degree Examination for CE. At any rate, just don't take my absence the wrong way. Have a good one guys!:)

1 mm is pretty darn thin. Let's hope your fix works.

Good luck with school. I can't even fathom reading a Calculus book nowadays cause I think my head would explode from the intensity.

Derek

Well, problem solved. It was indeed the terminal cup. Now it sounds the way it's supposed to. Put it to the acid test. Turned on Hold On My Heart by Genesis on my Eclipse CD-5030, set the HPF X-over for the front and rear all the way up to 10kHz, left LPF X-over at 80Hz. This effectively, isolates the high treble and bass frequencies so I can hear the subwoofer better. Otherwise, I have to listen to it over the midrange. Anyway, it purrs like a kitten now. After the listen, I set the HPF X-over for the front and rear back to 63Hz for optimum SQ. Readjusted the amp gain to a lower voltage; the larger the enclosure the less voltage it takes for the woofer to over-excur. Now I can set my ISF all the way down to 20Hz. Nice!

Oh, bustamove, believe me when I tell you Calc is just the tip of the iceberg. When I applied to UCR, I specified Mechanical Engineering as my major. I guess it filled up rather quick so I was placed in Pure Math since I specified that as a secondary conditional major. I breezed through Multiple Variable Calc and got an A+ in Diff Equations. THEN, I took Set Theory and Topology, which is a completely different story. I practically got whiplash from the pace of the quarter system in these advanced math courses. Transfinite sets, Proof, infimums, supremums, Peano Axioms, Completeness Axiom, Compactness Axiom, Monotonicity, not to mention double negative sentences as a means of being rigorous. I'll never forget what my one TA said, "But there is "no" empty set that does "not" contain the set of zero, {0}. Tell me about it! Don't get me wrong, I love all this stuff but not at the super fast quarter system speed. And in terms of text book reading, when I read my Topology and Set Theory texts, my Frontal Lobe was actually pulsating. Anyway, I'm going off on a tangent.

If anybody would like me to upload photos' of my new set up don't hesistate to ask. I'll put them in the profile gallery. I think its against CR's TOS to post photos' in a thread. Anyway, have a nice day guys!:)

Now my head is spinning after all that math stuff. Whew! I can see how you can get overwhelmed by going to a school on the quarter system.

You are certainly welcome to post photos of the install in the thread. Real porn will get deleted immediately, but car audio porn is welcome. We generally recommend a maximum width of 800 pixels and a file size of 300MB or smaller.

[/QUOTE]
Good luck with school. I can't even fathom reading a Calculus book nowadays cause I think my head would explode from the intensity.

Derek[/QUOTE]

BTW, sorry for forgeting bustamove. Thank you for your kind remarks. I am thrilled about going to a school now that specializes in the treatment of Asperger's. I start Aug 22. Its nice that they actually have CE as a selectable major. I can't wait to start digging in!:)

I am glad you got it figured out. Cheap terminal cups are always an issue. Radio Shack and other companies sell spring loaded ones that leak like no other. I always go for the screw down terminal.

Hey Easy E, how's it going man? How's the family doing? I'm about to embark on my journey back east. I'm going to live with my sister in VA, visit my family back in NJ, and am going to school in WV. Boy, without bustamove, CV, and you, these forums are quite quiet. Nice to see you man.

Anyway, about my install. I bought a 5-way binding post terminal cup, put some silicone on it, and that seems to have solved the problem, but in retrospect, I am concerned about a few things...

For starters, my dad insisted that we put a screw every inch where the adjoining piece gets fitted into the dado. So we have this layout on the top and bottom pieces. We used 1 5/8 inch screws, and like I said they're an inch apart.

Anyway, I started getting concerned about my dad's idea with the screw separation as I saw some slight splits in the adjoining pieces. I repeatedly asked him, "Do you think those splits will expand from the sound pressure?" His response was, "No, since the sound waves will be hitting the MDF perpendicular to the split". We haven't had issues thus far, but this stuff is a little over my head. I would happy if you would share some of your wisdom about this MDF split dilemma. Should I worry about expansion due to SPL? Uggh... I hope I don't have to make another, and scrap the one we built. But... hey, if I have to then so be it.

One other thing... In a future install, presumably after I have a BS in CE, I think I will undertake a project, where I incorporate an internal slanted wall in a vented enclosure. I realize now that that will yield better SQ. My current install is just a rectangular prism with a 36.75" port. This leads me to my next inquiry. Easy E, what adjectives would you use to describe the sound from a rectangular prism enclosure? From what I have read from CV, there's a loaded wave that propagates between the back of the woofer and the port partition that parallels the back wall. Anyway, I digress, what does this translate to as far as the sound is concerned? Again, I would like your wisdom Easy E.:)

Well its about bed time for me ha. I get up at 5 AM and have to catch the train at 5:30. The family is good. The children are monsters sometimes. Did you pre drill the holes for the screws? Also did you use a crap what is it called to flush mount the screws? No need to put a screw every inch. You know need a few per side like every 3-6 inches. The screws are just to keep the wood clamped so the glue can dry. A good wood glue is super strong. A rectangular port isn't going to sound much different then a round port etc. You might get port noise though because the surface area to port area is limited. That is why round ports with a flare is popular. It helps with port noise. All round square and rectangular ports sound similar minus the port noise. Maybe I will check this website once a week instead of once a month or 3.

First off, sorry for the long winded post Easy E. I tend to do that more often than not. Anyway, does having a screw every inch compromise the structural integrity of the MDF?

I asked my dad if we could remove the screws once the All-Purpose Gorilla Glue is dry, but he insisted that we keep the screws in. So now we have the enclosure carpeted and it's all hooked up in the car.

We pre-drilled the holes and the screws are 1 5/8 inch. My question is, will the splits expand from the sound pressure? Thanks in advance Easy E.:confused:

Depends on how deep and big the splits are. Leave the screws in. If it is only a minor split you should be fine. If you are happy with the finish product then don't worry about the cracks. No sense getting worked up over the little things in life :).

Hey Easy E. The splits are about a 1 1/8 inches. They are, as far as I can tell, relatively minor. Thank you for your advice Easy E; it really comes to me as a relief. You're the man Easy E.:thumbsup:

Have you began designing any audio equipment of your own yet? Maybe after I graduate, and acrue some income as a CE, I would be interested in purchasing anything you have devised. You truly are a professional at what you do, keep up the good work.:)

I tried to upgrade my alternator recently. Iraggi was the first one I attempted contacting. On his site, he only had alts available for domestics. So, I tried contacting him by phone, and, unfortunately, that was when disaster struck in Japan. Running out of options, I bought a 150A Bosch so that way I could upgrade to CDT Classics and a 4 channel amp. Trying to install a new alternator in an Audi is a NIGHTMARE! Everything is over the alt, obstructing our accessibility to it. So, we took it to a place that works on imports. Unfortunately, the 150A Bosch didn't fit. They said the only thing that does is a 120A Valeo. A "Whimpy" 120A Valeo if you ask me. So now I'm stuck with the factory BOSE with their lack-luster colorful output. YUCK!!!

I know more about "mathematical induction" than I do "induction". Here's your sign! -- KirK

Yea I designed a subwoofer. I haven't been in the car audio game anymore. I am super busy with work so it keeps me busy.

For the alternator a 120A has to be better then factory. Why don't you run the new amp?

Hey Easy E. I think I might run a new amp once I pick up a PT job preferabley on campus. I read some where that alternators generally run at 60% of their complete amperage. That was from one source. I also have a mechanic in the family that says it depends on the RPM. So you think having a 4 channel amp won't put too much strain on the 120 A Valeo? I'm certainly considering expanding the system, but buying the Audi kind of made me broke. Oh well...

BTW, you asked me before how big the split is. I used my micrometer, it measures to about 1/32 of an inch. And I tested what we applied on scrap pieces of MDF. The split thins out and becomes absent around 2 1/8 inches. The width of 1/32 inches is the maximum width of the split measured on the factory edge.

what amps are you running now and how big are they? Also what size 4 channel are you looking at running?

I'm thinking about running 50 W RMS x 4 channel amplifier. I would like some nice components to replace the BOSE.

I'm running the JL 500/1 presently with the gain set pretty low. So that 50 Amps there. The Eclipse CD 5030 supposedly does 25 W RMS x 4, so I'm guessing that might be another 10 Amps. So altogether about 60 Amps for the audio equipment.

You will be fine with a 50x4 amp. Good luck getting 25 watts a channel out of the eclipse.

Hmm... I take it Eclipse over rates the RMS on the HUs'. Well that doesn't come to me as a suprise that's for sure. First off, the HU wasn't CEA Compliant. I am starting to have a working knowledge of using the Param EQ. Mostly I work with the lower band of midrange frequencies, boosting them, set center frequency, adjust bandwidth. Also another thing too is it doesn't have a DAC, which is no big deal for me, I have a 8 gigabyte USB drive. That would create a problem if my older sister wanted to use her iPod Nano through the HU, but oh well, it's my car anyway..

Hi Easy E. Sorry for bringing up the alt situation. I guess I introduced a red herring there more or less.

Anyway, back to those splits. The split thins out and disappears at almost 2 1/8 inches, the max split width is 1/32 of an inch, and the screws themselves stop at 1 1/8 inches in the adjoining piece of MDF. We did pre drill the holes.

So, would this fit your criteria of a minor split, or should I be concerned about them? I highly value your input Easy E. Thank you in advance.:)

Everyone overrates their HUs. Think about how big a 50x4 amp is and think about how big the amp is to fit inside the HU. The problem with HUs is they don't usually raise the voltage from 12 volts like a typical car audio amplifier does. Because they don't have the room for it. So you are stuck with the 12 volt DC base.

Quote:

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Originally Posted by KirK

Hmm... I take it Eclipse over rates the RMS on the HUs'. Well that doesn't come to me as a suprise that's for sure. First off, the HU wasn't CEA Compliant. I am starting to have a working knowledge of using the Param EQ. Mostly I work with the lower band of midrange frequencies, boosting them, set center frequency, adjust bandwidth. Also another thing too is it doesn't have a DAC, which is no big deal for me, I have a 8 gigabyte USB drive. That would create a problem if my older sister wanted to use her iPod Nano through the HU, but oh well, it's my car anyway..

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Like I said before if you are happy with the sound of it don't worry about the split. Is the split hurting your SPL? Most likely. Are you going to notice it, most likely not. Unless you are in a SPL compeition and need every .1 DB don't worry about it.

Quote:

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Originally Posted by KirK

Hi Easy E. Sorry for bringing up the alt situation. I guess I introduced a red herring there more or less.

Anyway, back to those splits. The split thins out and disappears at almost 2 1/8 inches, the max split width is 1/32 of an inch, and the screws themselves stop at 1 1/8 inches in the adjoining piece of MDF. We did pre drill the holes.

So, would this fit your criteria of a minor split, or should I be concerned about them? I highly value your input Easy E. Thank you in advance.:)

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Thank you Easy E. That all makes sense. I'm definitely not taking it to sound offs, so that certainly isn't a problem. Well, okay then.:)

I wish I could hear it...