Dash Speaker Enclosure Design
So you've got yourself one of those fancy horseless carriages with the unique distinction of an audiophile’s wet dream; it’s got dash speakers. The problem is, they’re tiny. They could be 3.5, 4, or if you’re lucky….4x6 inches! Whoo hoo! Hold up Custer. Those Little Bighorns in your dash are going to cause you as much trouble as Crazy Horse if you’re not careful.
You see, the larger the cone area on your speakers, the lower the resonant frequency is. Since you’re relying on these preemie babies to cover the transition in the audible range from your lows (which are typically crossed over somewhere between 80 and 100 Hz) to your midrange (if you’re lucky you’ll get a clean response all the way down to 80) then those pitiful electroacoustical transducers in your Model T are going to have their work cut out for them. Since the back waves of the speakers are firing into the cavernous void of airbags, evaporators, and speedo cables they’re essentially running infinite baffle. Baffling I know, but at that rate when the first beat of Marky Mark and the Funky Bunch rips through your quasi-air dielectric bi-wired individually paralleled insulated Litz constructed speaker cables, your wee drivers are going to hop like Dogfish Head 120 Minute IPA.
What’s the solution you say? Two words: sealed enclosures. I know, I know, the door speakers in your wife’s Fiat X-19 sound great, and that’s not exactly Grant’s catacomb. What gives Buzz? Ok, ok, I’ve got two more words: antiphase radiation. No, it’s not some 1950’s propaganda concept designed to convince you that nuclear fallout is good for your teeth. It’s what’s happening in that mysterious place abaft your dinky diaphragms. Every time you jam your Esteban instructional discs, your speakers are creating sound through the front and back of the cones. If the back waves meet your ears at the same time as the front waves, then most of the sound is cancelled out. (This is why your Funky Pups sound like EVs when you play them out of the box.)
Those door speakers may be playing into a vibrational, diffractional, reflectional, partition, but at least they’re not playing down through the top of your dash and into the listening area like those cramped co-axials under your windscreen. Those back waves are wreaking havoc on your speakers’ ability to reproduce accurate sound, much less down to the critical frequencies that you need to transition out of your subs’ range.
You’re thinking, “You’re asking me to remove my dash and build a complex fiberglass enclosure behind my speakers? You’re a lunatic!” Well, you may be right. I may be crazy. But it just may be a lunatic you’re looking…..sorry. I got distracted. NO! I’m going to show you what to do:
So you’ve got your high-fidelity factory dash speaker……
Go ahead. Check out your hair in that dust cap…..
Once you remove the speaker, you could find anything in there……
If you find any rodents, food, children, or trash, throw it away. If you find money or beer, send it to FloridaSPL.com here: https://www.floridaspl.com/forums/payments.php
You’re going to need some supplies to get working…..
Most important; beer. After that, you will need some sound deadening sheets like Damplifier, Dynamat, etc., a closed cell foam product like Overkill pro, a knife to cut them with, a surface to cut them on, and some spray adhesive.
You start by placing strips of the sound deadening sheets inside with the goal being to create a bowl or cup shape in the hole.
Keep in mind that your speakers have to fit in the dash when you’re done. So use common sense when building your enclosure. Make sure your speaker’s magnet and terminal connections will fit when you’re done.
Building this enclosure as air-tight as possible is the objective.
I built the bowl shape with lots of strips and then I sealed the top edge with these little rectangles you see here.
If you only have the self adhesive mats, you’re done. Install your speakers and enjoy the sonic benefits. But if you’re going all-out with the closed cell foam, keep reading.
Since the bowl shape is symmetrical, I cut 4 equal pieces and sprayed them with adhesive.
And then I sprayed the adhesive in the bowl.
Spray glues work best when they’re allowed to tack up (dry slightly) so go pour another beer while you wait.
Next, carefully position the pieces in the enclosure for maximum coverage.
You’re looking to create a non-reflecting environment to absorb the back waves and reduce the,……wait for it……..antiphase radiation.
Building an enclosure behind the speakers will increase the power handling, improve the sonic accuracy, and reduce diffraction created by those pesky little back waves.
Now you can install your Kracos and jam Zamfir through the hood with pride.
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