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View Full Version : advantages to building box exactly to specs?



Falcons
09-07-2011, 10:20 PM
as stated in title, what are the advantages/disadvantages? im not asking which is better cause that is irrelivant. i would just like to know what the good and bad would be of building the box to specs. for example, if a subs fs is 38, and the company reccomends a 32 x 22 x 16 box, and someone perfectly built the box with no flaws (perfect world, i know not possible), would there be any problems with the sound? or would it be amazing lol

Falcons
09-07-2011, 10:43 PM
bump. come on im bored here and wanna learn!!!!

Buck
09-07-2011, 10:47 PM
There are many variable still, even with a perfect box and environment. Going recommended is good sometimes and bad others. It can void warranty in some cases but IMO a lot of big name car audio retailers make their box specs based on what will ensure that they have the least amount responsibility if the woofer breaks.

Anyways, it really depends. The recommended box is just that, a recommended box. They are by no means perfect.

Falcons
09-07-2011, 10:48 PM
ah makes sense. i just looked up my box and it is exactly built to specs lol. pro-rabbit designed it for me

Buck
09-07-2011, 10:54 PM
Pro-rabbit is a good designer to my knowledge.

I usually don't do recommended (for myself) because I like to push the limits a little and test theories. Like my BL's are tuned to 27 hz, and the lowest recommended tuning for them is 31 hz I believe, but I love the way they sound.

DD recommends tuning of 38 hz. I don't like 38 hz tuning personally, in any setup so far, so I don't do 38 hz tuning for DD's unless asked to.

The best thing is to let science work with you, and figure out how you want your woofer to sound. Then design a box based of the woofer, sound you want, and vehicle.

Falcons
09-07-2011, 10:57 PM
right now i got a 4.0 cubic box tuned to 33 hertz on 2k. memphis mojo 15-cm15d4 is my sub

Kangaroux
09-07-2011, 10:57 PM
You could design the "perfect enclosure" but that's only part of the story. The enclosure does the heavy lifting but it still boils down to whether or not your sub is decent.

Falcons
09-07-2011, 10:58 PM
i know my sub isnt the best but it is definately a decent sub

Linkz
09-07-2011, 11:12 PM
Building to spec meas you are building to what the manufacture deemed the purpose of the sub is. For example. DD likes to recommend high tuning because it give a better score(relative to lower tuned boxes of the same size). They are a company know for their strength in the lanes. Which means that they recommend enclosures that will do well in the lanes. The same goes for other companies. I am sure it varies on the perception of what a product line is meant for (eg ddz vs 1500). In all honesty, The recommend enclosure really means nothing. It all boils down to what you want from a subwoofer system. I like the lowes. As a result I built a very large box with a low tuning. Terra is the owner of CD. Which designed the driver I use the omega. He recommended no more than 7cuft and a tuning of 35hz (or there a bouts). I ignored his advice and made it 9.5cuft@~34hz. The result is exactly what I wanted. An enclosure that gives massive bottom end from 30-40hz. Sure I lost some of the power in the higher frequencies. But, I have massive gain in the mid and lower 30's where most of the chopped and screwed music that I listen to plays at.

Falcons
09-07-2011, 11:16 PM
well im bout to experiment cause now i got a box that kills the lows im gonna tuned to around 40 hertz and see how it does. hell mdf is cheap! lol

Linkz
09-07-2011, 11:21 PM
A ported enclosure begins to unload after the frequency play dips below tuning frequency. Tuning to 40hz means that it will begin to unload below 40hz. I do not see how such an enclosure would kill the lows. It would be better to tune around 33-35hz.

Though my definition of lows is defined as upper 20's to mid 30's. So, you may not have the same view as myself in that regard.

Canaan
09-08-2011, 03:10 AM
***I only read the title of this post....none of the replies***

IMHO...building an enclosure based on the manufacturer's "spec-box" is boarder-line CRAP.
Yes, building a 'manu-spec-box' can be a good place to start, but from my time in the 12v world...many mainstream lines recommend a box that will be LOUD in a demo room. Thus, increasing sales due to the loudness around 50-60hz. (If you have ever spent any real time in a reasonably sized demo-room in a shop w/ the average joe, you will see that LOUD SALES!!!!) Hell, if you look at most "good" prebuilt boxes....most are tuned in the 40-45hz range. Thus, with most common subs tend to peak in the 50-60hz range, reinforcing peaks of most sound rooms and making even crap sub systems 'sound' louder.

Forget the 'manu-spec-boxes' in vehicle, unless you have a large SUV and like peaky bass w/ spotty low-end response. (AKA...PROBOX brand crap)

Your enclosure is 80% of your sound when it comes to subwoofer design.
Design your enclosure around your vehicle's acoustics and your sub's parameters.

Otherwise, everything is just hit and miss.




Edit:
Also...ported/vented box tuning (aka HELMHOLTZ RESONANCE) can mean next to nothing in a vehicle environment.
"Tuning" is just a number derived from math based on driver's T/S parameters in a ported/vented enclosure in an perfectly open environment. (AKA...anechoic chamber)
Helmholtz Resonance is (simplified as) the point at which a given driver's impedance is at it greatest in a given environment and enclosure.

Even if your enclosure is 'tuned' to a given freq, if you simply change the environment of the forward chamber (vehicle cabin) you totally change the resonance of the subwoofer, aswell as the response.

For example, if you have ever listened to a simple sealed subwoofer enclosure in a single cab truck you have likely noticed that the bass is FAR louder when windows are rolled down.
Just rolling the windows down in this case turns the cabin of the truck into the forward chamber of a 4th-order bandpass (in horribly simplified terms). Thus the Helmholtz resonance of the drivers shifts. And given that...in principle the forward chamber of the 4th order has become larger. And thus the 'tuning' has become lower.
That is basically why low freq. response is FAR more prominent when your simply roll down the windows of your single cab truck.

This is a VERY basic representation of what can happen due to driver and enclosure design in any given vehicle.



Their is no PERFECT enclosure.

Only an enclosure that fits your personal preference with a given driver.

pro-rabbit
09-08-2011, 11:44 AM
ah makes sense. i just looked up my box and it is exactly built to specs lol. pro-rabbit designed it for me

yep, it is with in the ft3 specs they use and the port area is a bit different then what they would recommend but looked great when I plotted it and should have yielded some great results(per what you asked for at least).

Upping the tuning will get you a peaky response and better numbers if that is what your going for.

You never did get any pics of the setup lol. I wanted to see how that design worked out for you.



As for the perfect enclosure. I'm not sure there is one that can exist. There is always give and take when designing. Different applications will have different end results and various levels of audible play. In most cases, this is very subjective as we all have a different idea on what the overall output should be of an application. Some like deep bass, some like it a bit higher and others just want to burp at the highest number they can muster up. Each scenario is different and will require a different build/design to achieve those goals.

24v
09-11-2011, 12:40 PM
For example, if you have ever listened to a simple sealed subwoofer enclosure in a single cab truck you have likely noticed that the bass is FAR louder when windows are rolled down.
Just rolling the windows down in this case turns the cabin of the truck into the forward chamber of a 4th-order bandpass (in horribly simplified terms). Thus the Helmholtz resonance of the drivers shifts. And given that...in principle the forward chamber of the 4th order has become larger. And thus the 'tuning' has become lower.
That is basically why low freq. response is FAR more prominent when your simply roll down the windows of your single cab truck.

This happens in my truck with a vented enclosure. The difference with the windows up vs. down is pretty great. Is there an enclosure type that would be more resistive to this? It makes tuning pretty difficult. Almost need a windows up, and a windows down setting.

boxy
09-14-2011, 09:10 PM
Although I'm fairly new to serious car audio (about 18 months) I have experienced good and bad versions of both prefab and custom boxes. I've heard twin 10's and 12's in custom builds that my (prefab) DDLE312 simply destroys in terms of depth and loudness (going by the ear not by any measurements). I'm looking to build my own enclosures, simply because my car is tiny and I want a bit more boot space, so currently I'm purposely looking for a sealed set up. But right now I'm willing to sacrifice boot space for a little bit more liveability with my car.

Manufacturers will always play it safe. I was reading tonight someoneís complaint over a PWK design box (Iíll see if i can find the thread) basically the guy felt that the reason for his sub blowing was bad box design. Of course manufacturers don't want a heap of burned out subs and angry customers, so i should imagine they would play it safe .. wouldn't you if you were in the same position?

It would seem that some equate 'Good' for 'Loud'. OK I probably lean more towards SQ with a hint of street-bass, than out and out SPL, but i think people do get distracted by simple statements like 'it'll be louder'.

As for a perfect solution, the next sub will always sound better, the next box builder will always claim to come up with a better solution. Us audiophiles are never satisfied. We're always looking for the next best thing.

I love the 'windows down' example! Thank goodness there's someone who really understands such differences, that many so-called experts seem to set aside. I posted such an example and got a mouth full of abuse, and was basically shouted off the forum.