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Old 01-13-2003, 11:18 AM   #1
fragment
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Default Why don't the door speakers use/need enclosures?

This has bugged me for a long time, and I'd like informed opinions on why most installs of higher end car audio don't utilize sealed enclosures for door speakers? I'm thinking here of 5 1/4" and 6 1/2" drivers. In my mind, the mid bass would become much more accurate, punchier and less prone to driver slap. I'm toying with the idea of creating small sealed fiberglass enclosures, and I'd like to hear pros/cons.

Right now, I'm using a/d/s/ 5 1/4" separates with dynamat around the speaker mounting location, but not totally dynamatted. I find the mid-bass to be pretty bad, and I know its not just the speaker. When I had these same speakers in my Legacy GT, they sounded much better.
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Old 01-13-2003, 12:42 PM   #2
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Actually most high-end stereos do use enclosures in the front. You see them in the kickpanels usually made with fiberglass.

I have never had mine installed in the kickpanels. Basically because i was worried about the passenger kicking them accidentally and legs covering up the sound.

The reason they put them in the kickpanels is that you can get better imaging. You will also get better mid-bass because they are in a enclosure also.

Some companies make pods for particular cars for a custom fit. I would say go for the kickpanels if you want more midbass.

Also, its not surprising to move to another car and it sounds different. Cars have different characteristics (volume and damping). Don't know if you have control over crossover points but you may want to play with that. Gain settings on all equipment being used may also need adjusting.
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Old 01-13-2003, 01:17 PM   #3
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I do have controll over the cross over points; if I want it. However, the a/d/s/ set has a dedicated crossover that I'm using because I don't think playing with the crossover point between mid-bass and tweeter will gain me anything. I should let you know that I have the seperate components bi-amped, but using the factory crossover. I have played a fair bit with the sub to mid bass crossover, and I've settled on 80Hz with 24db/octave roll off.

I don't like the limitations posed by kick panels; namely loss of foot room and having my tweeters firing at my shins. I've got size 13 feet, and find the footwell cramped already.

My thinking is to build a fibreglass "bubble" behind the mid driver that bonds to the mounting adaptor I built out of MDF. I've never worked with fiberglass before though, and want to know that I'm going to get an improvement before I go through the time and expense of building these things.
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Old 01-15-2003, 01:44 AM   #4
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The door is used as an enclosure, which is hardly an ideal proposition. Hardly ideal is putting it lightly what with all the holes and open spaces for the window winders, electric locks, heating/defrost/mirrors, vents, and what not. Its not the greatest, but since there is usually a bit of air space in there it generally works for most applications.

If you did want to turn your door into an enclosure, you could glass the inside and fill the door skins, then dynamat the interior skins, and polyfill it. I'd think that that would be quite an enclosure then. How much do you value your doors versus your midbass?

Also, I'd think that if your speakers are bottoming out then they are hitting and exceeding the maximum travel of the system and that you'd either better cross them over or not put so much low bass through them. I'd say its pretty damn hard to get 50hz out of a 5 1/4 no matter who they're made by.

An automobile is not an ideal environment for an audio system. That said, what is your idea of great midbass? And are you being realistic? Memory always has a way of making things we remember to be better than they actually are or were.

I run a set of Soundstream SPL60G components at 2ohm with about 150watts per. I find that the midbass kick down to 65hz to be excellent with no dynamat/etc but then again I'm not expecting anything more. Yeah, I think it sounds great until I step inside to hear the same music through my bi-amped Sony SS-M7's and I realize just how crappy everything sounds in my car. Reality bites.

I'd reccomend getting the largest size drivers you could into the doors if you want more midbass(bass?). Dynamat doesn't actually help the bass, well maybe a lil, but it mainly keeps your doors from rattling. As long as there are still holes in your doors like swiss cheese, dynamat ain't gonna cut it. So get bigger drivers.
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Old 01-15-2003, 01:53 AM   #5
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Quote:
Originally posted by fragment
I have played a fair bit with the sub to mid bass crossover, and I've settled on 80Hz with 24db/octave roll off.
I missed this part.

Damn, 80hz with a 24db roll off is a pretty good reason why there ain't much down low. Your drivers aren't getting to use the awesome bass extension from the built-in resonance frequency of most car cabins which is generally around 60hz. What I mean is that most vehicle cabins boost frequencies near 60hz which is like getting free bass, but if your speakers are getting cutoff with a seriously steep slope like 24db/oct at 20hz higher than said resonance freq point, you're losing out.

Get bigger speakers and cross them over at like 75hz with a 12db/oct slope so they can use the cabin resonance to make more bass.
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Old 01-15-2003, 11:02 AM   #6
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I agree somewhat with what thesmokingman said. I don't know about a specific frequency at 60hz that cars resonate at, however, I do know that most of your problem lies in your crossover frequency. I personally have my midbass drivers set at 80hz as well, but with an 18db/octave roll off. I get a LITTLE bass extension but nothing to rave about. When I move my crossover point to 50-62hz, I get considerably more bass. In fact, so much that I almost wouldn't need subs, but we all want to FEEL the bass every now and again. I am using Focal's 165k2's in custom door panels and love them.

Honestly if you want better bass extension get yourself an 8-inch driver or a sub, for those lower end frequencies, because tuning your mids below 80hz could definitely cause them to fail which is why I assume you already haven't done so.

Oh and before I finish the post, the enclosure might help you gain a couple db's of extension in the lower end, but I can almost guarantee you it wouldn't be worth your time to do it.

Chad
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Old 01-15-2003, 11:26 AM   #7
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I know for a fact that the rear speakers that are in the rear deck must be shielded from the trunk if you run a subwoofer in there. Otherwise the woofer will push the speakers and cause Dopler effect.
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Old 01-15-2003, 01:12 PM   #8
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Maybe I wasn't explicit enough. I also have a 10" a/d/s/ DVC sub in the trunk inside a sealed enclosure. Right now, its running 80Hz down. I've got a pretty good bass system, just the mid-bass problem.

Given the Q of the 5 1/4" driver, I think an enclosure of .2 ft3 or smaller would be ballpark. Right now, the driver is operating in free air suspension mode (given the poor sealing / size of the door enclosure) and I'd like to see if enclosing it would increase the SQ, and maybe also extend the sound level limit before it distorts.
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Old 01-15-2003, 01:55 PM   #9
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You're right you didn't give enough details. Proper equalization should solve your problem as well. What type of eq, if any, do you have?

If you already have a nice EQ, and you've tried tuning to correct the problem, why not try another midbass driver? Not all drivers match up well with others, and a/d/s/ are not particularly known for output, but moreso for clarity.

Chad
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Old 01-15-2003, 05:42 PM   #10
fragment
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My head unit has some limited EQ capability (seven bands with selectable Q), but I'm a fan of getting the base system as right as possible before "processing" the signal.

My original post wasn't really a request for trouble shooting help with my system (or I would have given a complete list of the parts and setup). I was really looking for a theoretical discussion of door enclosures.

Thanks for all your comments.
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Old 01-15-2003, 05:42 PM   #11
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There isn't room inside the door for an enclosure since the window rolls down half way past the driver magnet. And in most installs the window itself is with in millimeters of touching the magnet.

You could try sealing the door better, making it less of a free air system. At least you will have better sound when the window is up. A downside is the amount of moisture that will accumulate inside your door.

Using the 5 1/4 driver from the 235im set which has a free air resonance of 82.2Hz, vas of 4.34 liters, and a qts of .64;

The box volume would be about .37 cu. ft. using an ideal box Q of .707, which would give you the smoothest response and achieve 97Hz +/- 3db. After about 90Hz it starts to drop off. At +/- 6db its at 70Hz.

As ruiner suggested, your best bet is to try a different driver. I'd reccomend one with a much lower F3 (resonance freq) as that is a true indicator of exactly how low the driver can hit. ADS claims a freq response of 48Hz-22KHz, but thats hardly attainable outside of an anechoic chamber, not to mention the infinite baffle thingy.
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