Woofer upgrade in Aspire 4330, 3680, and similar

I would like to share my experience significantly improving the sound quality from the so-so 3680 or the tiny pathetic 4330. Usually adding speakers inside a laptop is either not possible or completely counterproductive. Many laptop amplifiers won't handle impedances under 16 ohms. There's usually nowhere to actually put any speakers, and even if there were, you usually can't enclose that section of the laptop in order to make an isobaric chamber. If you do, you're likely to block vital air flow. Worse, any usable openings are usually so small that you can only add smaller, even more tinny speakers to the already tinny laptop sound.

The memory cover on the 3680 has a small vent section which is usually covered over with some black plastic. It seems that this was designed to be a vent for an option that isn't available on the 3680, such as a video card upgrade. Since air doesn't need to flow through, and since the connector for the front speakers becomes accessible from here, this is an easy place to add sound.

As for the choice of laptop speaker, I run a computer shop and so have a large basket of small laptop speakers scavenged from junk laptops of all ages. By a wide margin, the best speakers I've found are the steel-frame-caged speakers found in many Pentium II Toshiba Satellite Pro's. They're 16 ohm long-throw poly-woofers, and despite their tiny size, they produce full-range sound. (A great way to demonstrate the potential one of these holds is to hook it up to a headphone jack, place the front of the speaker against a CD, and place that CD against an empty jar, so as to make an isobaric chamber.) One advantage of these speakers is that they're open-air, meaning that they're not integrated into tiny plastic boxes. They're ready to be engineered into any new container you make for them.

For my first Aspire 3680, I used some electric tape to mask off the vent holes that would not be directly in front of the speakers, and then I used super-glue to attach the speakers to the remaining openings, being careful not to let any super glue touch the speaker membrane. Splicing into the existing connector was a snap, and there was no problem making the wires fit inside the spacious laptop. I closed it up, started some music, and was initially disappointed.

It seems that my mistake was to rely on the rest of the laptop to act as my isobaric chamber. I had two options to correct this, though.

1) I could make a container inside the laptop, such as from sliced pieces of CD cases put together with super glue. This would have an advantage of consistent sound quality and the simplicity of being a complete speaker enclosure entirely placed on the back-side of the memory cover.

2) I could use pieces of weather-strip on the bottom of the laptop to create a perimeter around the area where the speaker's were, so that when the laptop is placed on any flat surface, such as a counter or desk, the combination of that surface, the weatherstrip, and the bottom of the laptop would become an isobaric chamber for the speakers, and the sound would emanate upwards through the laptop.

For my first 3680, I chose the second option, since I like to have a laptop play movies while I work, and I have little need to loud, rich sound while I have it sitting on my lap. I have another 3680 coming in, which I think I will design with a very small audio amplifier, dedicated chamber, and single woofer, somewhat like some of the large Dell laptops have.

The result is that the sound is not any louder when the laptop is placed on a table, but it's much richer. However, when it's lifted off of the table, the bottom of the laptop is just a baffle, and so it's simply much louder without being any deeper.

The Aspire 4330 has all the solder and bolt points for an MXM slot, but there's no slot there. Instead of soldering on an MXM slot just to see what would happen, I decided that the Intel 4500MHD video is good enough for me, and I'd rather have better sound. On one hand, it's easier to make a really good isobaric chamber on this laptop. I used four layers of common household weatherstrip to create a box so that the speakers would use the open area where a video card would go as a chamber. In fact, there's even a convenient screw hole to run the speaker wires up through, so that you can splice them into the connector on the other side of the motherboard. The only problem I ran across with this was that there's so very little tolerance for even a millimeter of extra stuff between the keyboard and the upper plastic piece over the motherboard. I simply split the wires up and spread them slightly. (Note: Don't use electric tape. Masking tape works so much better for these low-voltage wires.) As it turns out, this actually improves the keyboard a little bit, because it supports the back side. Just make sure it's not pressing up so much as to warp the keyboard.

The sound quality improvement on the 4330 is simply astounding! This is now ranked up with among the very best-sounding laptops I've ever used, even besting the old Presario 700 series. I kind of suspect that the amplifier used in the Aspire 4330 is 8 ohm nominal, because the maximum volume is much higher. In fact, even if I completely block the speakers I added, the original speakers alone are much louder than before.

I will try to add pictures as I get a chance, and as I get more of these budget Acer's with awful sound, I'll be sure to add details.

By the way, I'm normally not so helpful when it comes to making how-to's, but having taken so much from the Acer Aspire 3680 Core 2 Duo upgrade instructions, I am encouraged to share my Acer modding experiences. I'd also like to add that I have been working on computers for quite a long time, and I love modifying hardware, but budget Acer laptops have been among the most rewarding by far.

Update 1: The Aspire 4330 has some awful standing waves, I think somewhere around 6k. Unfortunately, I think they're coming from the original speakers. This is bad news, because the solutions aren't as nice as I would like. I can attempt to stuff the original speakers with fiberglass, place weights on the domes, or use a notch filter. These are all fidgety things that I don't mind doing, but they're all tricky to describe. Stuffing the original speakers with fiberglass will probably solve the standing waves the best, but how the heck do I do that? :-D Placing weights on the domes will work, too, but finding the right weight is a very frustrating process, and the resonant frequency of the speaker will change slightly, so it's not a permanent fix. A notch filter is simple circuitry, but I think what I'll use is a very simple filter config. I think I'll just use one capacitor per speaker to start a 3db/octave drop at 6KHz, since the speakers that I added on the bottom do fine at 6KHz and stay nice and flat until the upper 100's.

Update 2: I have a new favorite driver: Headphones. The drivers in headphones are very low profile, and they have a lot flatter response. They're cheap to obtain, push a lot of air, and are often 1.25", which fits perfectly over the vent grills. The two main downsides are that I can't tie both left and right channels to one single driver, and the efficiency is low. The solution to both problems is to sneak an LM386 in, probably powered by a USB port. This is a whole lot more work. But there are two big benefits: 1) I can actively low-pass filter the sound. 2) I can pull the signal from the headphone jack. That way, I can use the Headphone volume control as subwoofer control. I can either use the mechanism in the headphone jack to cut signal to the LM386, or I can rig a mute function that's simply enabled when a headphone jack is plugged in. Those are both much easier than they sound. (-: (Another amplifier I might consider is a TDA1517. They tolerate a wide range of supply voltages, they're easy to design around, and I have plenty of old ISA sound cards that I can scavenge them from.) Before doing that, though, I think I'll try gluing two headphone drivers together facing eachother. If I can make a simple solution, I shall...

Update 2a: I tried the headphone drivers together, and maybe four of them (two pairs of two) would match the sensitivity, but it would definitely be a better solution to use just one with its own dedicated amplifier. This is much simpler than it sounds, as the LM386-based amplifier is such a simple circuit that I would probably just solder the external components onto the pins and wad the whole thing up in glue and/or tape. The LM386 is just a 1/4 watt amp, but I think that's plenty for what we want to do. If it's not, then two of them in a BTL would do the trick. LM386's are usually less than $2 at your local Radio Shack.

Update 2b: I don't know why, but the 3680 seems to drive the headphone drivers much harder than the 4330. I think I prefer the old long-throw laptop speakers, but the headphone drivers still work very well and are easy to come across. One down side is that they require a little bit of cutting into the RAM cover if you want to use two of them, but if you plan to make an amplifier and run just one, then this is the perfect driver.

 

Looks like the LM386 is just not strong enough off of a 5v rail, and I don't want to run it at 10v+, 'cause I don't know how much power the MB needs. I would like to try an LM4670 instead, but in the meantime I will try two LM386's in BTL configuration like I mentioned. I hate to use extra parts, especially where space is so tight.

The LM4670 is a bridged 1w amp that operates most efficiently at 5v. It's surface mount, which makes it a bit of a pain, and it's not available at very many small electronics shops. Of course, the easiest thing would be to find a pair of USB speakers, rip them apart, and find some place to hide the circuitry. Unfortunately, a lot of them are too big, and you won't know it until you've already torn it apart.

I've been toying around with some Aspire 5315's, because they have a large volume of air not being used for anything. The stock speakers aren't nearly as bad as the 4330's, so an additional speaker should be aimed more towards mid-bass. One well-done Aspire 5315 should have really nice sound.

Question: Anyone know how easy it would be to pull 12v from the SATA power connector? I don't think the hard drive actually uses it. Edit: Nevermind. I -know- the hard drive doesn't use it, because it's turned off. *sigh* Oh well.