95Honda

I bought a case (like 16 or 24 or something stupid like that) of the first 4.5" full range Adire CSS drivers (Like FR125s or something, I can't remember the model) back in 03' or 04'. I used them mostly for home audio, but I did play with a few pairs in an automtive environment. A few things of note- Even being 4.5" or so in diameter, they still beam, alot, especially where they are touted for having a good top end. They did not sound very good off axis at all. I added tweeters to most of the installs. They don't play very loud, at all. A 4.5" driver (even with the 1/2" or so of stroke) doesn't have a lot of output, especially if you are driving. I blew one actually, fried the voicecoil. They sound really good on-axis at moderate levels, especially if the aren't being overdriven. They don't have much bottom end unless you put them in a very well designed enclosure. They suck in a car door. I did buy a pair of the Dayton Neo 8" fullranges, they are still in the box, but I think I won't even entertain putting these in a car, they simply will not work off-axis in the slightest up on top...

All of those plots have a lot of ripple and when combined with cabin gain will make it sound like you are missing the top end of the sub stage due to the exaggerated bottom end. You should try and find something that models flatter, or you will be forever stuck with what sound you are describing (without heavy eq'ing...)

I am starting a build for a friend of mine. His goals are a decent amount of bass in a removable package. This will be installed in late model 4-runner. After talking with Brian (BKOLFO4) about some different single driver solutions that would have good output he suggested a single Mayhem 15, and well, kind of going to take his word for it. As for power, I bought a single Cresendo 3500, should be plenty of power. The 4-runner has a decent factory stereo (Nav and all that crap) so we wanted to keep what we could. I picked up one of the new Audio Control LC2i: http://www.audiocont...ol----LC2i.html because I am sick of PAC Trunk LOCs. They are POS's that are nothing but a headache. I only say this because I have installed about 10 of them. The LC2i also has a cool ciruit that defeats the factory compression of bass at higher levels... And remote turn on triggered by signal sense... Way cool. He also bought a 250 amp alt and plenty of 1/0 and a stout battery. So good there... Now, as for the box. This presents a few problems. It has to be small enough to fit behind the rear seat and we want to keep it below the window line. Brian suggested around 4ft3, I am going to go with that. A 30Hz tuning should work pretty good. Woofer and vent will fire back. 1.5" MDF construction, heavily braced. Inside will be heavily coated with Cascade Quiet Coat (I have 5 gallons left over) and outside will be proffesionally Line-X'd. Grill be solid PA style, steel with perforated holes and powder coated black. Will cover the entire back of the enclosure, flush with the cabinet. Now, if there is one thing I hate, it is mounted electronics to the enclosure. But with this install, everything needed to be removable. So the amp and LC2i will be mounted to the front of the enclosure (against the back seat) with these isolation devices: http://www.zorotools...e_Shopping_Feed I am going to countersink them into the cabinet about 3/8" of an inch, so they won't be very visible. I did a little research, these should help alot in the range of vibrations the enclosure will try and transfer to the amp. Since the amp is mounted verticle, I made sure the shear rating was adequate, didn't want them sagging over time. I'll use 6 on the amp and 4 on the LC2i. They will be attached to the cabinet with T-nuts from the inside via studs with LocTite. As for making everything removable quick via electrical connection, I am going with a single 5 pin Neutrik XLR: http://www.parts-exp...tnumber=092-328 for signal and 1/0 breakaways for power: http://www.parts-exp...tnumber=263-112 Nice thing is, for signal, I will use some 18/4 architechual cable with a nice braided jacket placed over it. It will look good and be simple and clean. There will only be the single break-away power connector and the single signal connector going to the box. 2 connections and your done... Anyway, just waiting on the Mayhem right now, I'll probably start the box in a week or so. I'll post pics as the build progresses. -Mike

Optimum port area has NO RELATIONSHIP to the box volume. This is kind of a bad rule of thumb... The only way to know if your vent has enough area is to model for Vent Velocity. "Less ports are more efficent" = Basketballs make good salad dressing Honestly though, both vent options should not introduce much compression with any 15" drivers, I would go with whatever option fits your build better...

The video should be deleted. Horribly misleading. The guy doesn't really have a clue on what he is doing, either...

Your not to blame, it is just understanding what you are measuring. This is why there is a lot of confusion on what is going on when test equipment is involved. Even something as simple as a DMM can get you started down the wrong path if you don't know what you are doing. The terminals could also very well be faulty, but the fluctuations you were reading (especially the ones without the terminals) was being caused by the woofer.

Don't worry, the fluctuations you see the amp never does. Also, what you are seeing can very well be lower than the driver DCR due to the current flow from the driver. Again, the amp will never see this though, only your multimeter...

And don't forget, you CANNOT measure impedance with a mutimeter the way you have it hooked up. You are in no way measuring what your amplifier sees...

Re-read what I posted about the current levels causing your meter fluctuations. They are anywhere from 1/1,000 to 1/1,000,000 of an amp. You amplifier has what is called an output impedance. It is very low, like well under 1/100 of an ohm. It completely dampens out ANY current fluctuations caused by your woofers turning spurious acoustic energy into electrical energy... Want to see how output impedance works? Tap on your woofers with the amplifier off and then on. You will see how it dampens out the woofer... It literally acts like a brake on the cone...

That means 1 millionth of an amp... Yes, .000001.... Also, take a 25 pound weight and lay it on the cone (find a way to do this without damaging the driver) and you will see the fluctuations drop because of the increased mechanical dampening...

Believe me, it doesn't take much. It could be as simple as the mass of the probes or the way the leads are angled from the terminal. You are talking micro and milliamps... The bottom line is, you don't have to worry about anything you are measuring being presented to the amplifier.

Oh, and the fresh recone has more mechanical dampening since the spiders are new, so that is why you get less flucuation...

You kind of need to go back to basics to understand what is going on here. The terminals aren't the reason for your erratic readings. A loudspeaker is a transducer. It takes one form of energy (electrical current) and coverts it to another form (acoustic energy). It also can also do the opposite, change acoustic energy into electrical current. Your multi-meter measure DC resistance (in no way does it measure impedance). It does this by applying a very, very minute amount of DC current to whatever circuit is placed in series with it and it measures how much current flows through the circuit and calculates the DC resistance from this. Any, and I mean ANY small (talking micro to low milliamp) current introduced into the circuit under measurement will throw off the meter, substantially. The subwoofer will produce milliamps of current with you talking in the same room at a low level and it being 10' away... That is how easily it effects the meter readings. So why are my direct leads making a difference? Simple, due to tension on the leads you have changed the mechanical dampening on part of the suspension and reduced the woofers ability to act as transducer. You have changed it just enough to dampen out some of the cone movement and therefore some of the current being introduced to the meters DC resistance measuring circuit. It is also easy to see how this works if you have a recone by itself out of the motor. You can hook up the leads any way you like and you won't get any more fluctuation than the meter leads by themselves as the recone cannot act like a transducer without the motor attached. Additionally, if you were to place a tight shim in the gap that locked the cone in place you would not see the fluctuations. And lastly, these measurements do not in any way AT ALL represent anything your amplifier sees. You are talking milliamps of current, once connected to your amplifier the output impedance dampens any of this, completely, and it will never effect the overall load your amplifier sees in the slightest. I hope this clears up what is going on.

Jeeze... Nobody is saying thinking is a crime. What people are saying is think about what you are doing logically and make informed decsions. When we see bandpass ratios, port area rules of thumbs, RMS questions, etc. it makes the people who want to help think you aren't serious because you aren't doing all your homework. The comments are meant to keep you from wasting time. I remember when nodoby would get butt-hurt on audio forums, it has been a long time... Lol... (And no, this comment is NOT directed at anyone in particular)

99.99999% of the people who are going to give you and answer have no idea what the impedance they are presenting thier amplifiers actually is. So honestly, you aren't going to get any objective answers to this unless someone has a swept impedance curve of thier subwoofer system and the amplifer you are talking about. This is kind of the problem and where so many different opinions come from, they are not based on any sort of facts, just gut feeling. You can get in trouble because guy X runs the same subs as you and the same amp and is fine, but your box may have a completely different impednace curve and you might cook your amp where guy X was fine the whole time...

I don't really do it for buisness anymore, this was a personal favor for a friend. I really have no idea who in my area builds decent boxes...

Also, don't forget that anything can be shipped to an APO if it less than 75 pounds. You can have it mailed to a family member and then have them forward it to your APO address or use a place like "Ship It APO". I had everything from gun optics to paints sent to me in Germany that the vendors wouldn't send directly...

I was dissapointed with a few of the instal points. I had pre-assembled everything in Colorado and ensured every fastener was aligned and fit perfectly, lubricated all threads to prevent galling and oxidation and then carefully dissasembled everything. I next printed out detailed instructions on assembly order, torque specs, etc. The installer managed to cross-thread one of the 1/4-20 button head hex screws that held the grill in place (because he managed to install the grill upside down and the holes don't line up perfectly that way). I picked up a tap and chased all the threads. They also did not understand how to instal the quick dissconnect the right way, they actually ruined the first one. I guess the moral of the story is, no matter how thorough you are, if you don't do it right yourself, it doesn't always get done correctly. I do admit I am picky about this, this is easily my 200+ loudspeaker I have built, I have doing this since the late 80s. But I am still dissapointed when a decent shop can't see a project through to the end without issues... My buddy Tony was super patient with them and ended up getting what he wanted in the end, so that is really all that matters...

It took a long time to get it done, too... I am finally finishing my H/T, too. The last parts should be waiting for me when we get back from vacation next week...

Thx. Was good to see it come together...

So I finally got back to Seattle to hear the system last week... It has been almost 2 years since I built the box... Well, it is loud, real loud. Loudest single 15" I have ever heard. The response was also smoother than I had thought it would be. Not real peaky, but I attribute that to the vehicle more than anything... I designed for a flat response, and the cabin gain (at least from the passenger seat) isn't horribly ragged. It would keep up with some decent rock tracks and sounded pretty good with overall. Little John was obnoxiously loud, as expected, and my buddy listens to alot of Dub-Step, which also shined. The HO alt held solid voltage with the Cresendo 3500 well into clipping everywhere but idle and there were no heating/shut-off isses... All in all that Mayhem is one hell of a driver. Thanks Brian Owens for the idea... He is easily knocking at the door of 150db in that 4-runner...

If you go ported, you will probably have a lot of ripple in response and it probably won't sound too good...

Your 12s are already in a 4th order enclosure. Are you wanting to build a bandpass? They are more complicated and only potential gains in output over a small range of frequencies. If you aren't really good at designing and building enclosures now, I would suggest building your knowlege base or hiring out the work.

I would purchase a copy of the Loudspeaker Design Cookbook.

Even if you can't find a LOC a simple voltage divider will work perfect. All you will need is a pair of 20 cent resisters to knock the input voltage to the amp in half which will probably be perfect. You already know the input impedance of the amp so it is pretty easy to design and build, I will walk you through it through email if you would like, no problem.