I will have to agree, box must be a tad too large.
Two reasons speakers fail:
A. POOR BAFFLING
Speakers in poor baffles in cars can have an amazingly short life--months. This is often due to mechanical failure, not thermal failure. Thermal failure comes from overheating the voice coil at any frequency. Mechanical failure happens when a speaker cone travels too far in the BASS range. This can happen easily at power levels far below the thermal (wattage) rating of the speaker in bad baffles. (Some manufacturers use a surround and a spider with a limited throw to make long excursions impossible, but that causes two more problems. Limited throw means an increase in bass distortion and a decrease in bass volume.)
# What is a GOOD BAFFLE? A solid box the right size and type for the speaker in it.
# What is a BAD BAFFLE? There are lots of possibilities...
1. NO BOX. Yes, people will lay a speaker down with no box or baffle and play it. Sometimes they hang them up by a wire or string and play them. Then they wonder why they don't get any bass and why the speaker tears apart.
2. A good box, but one with a port or passive radiator tuned TOO HIGH in frequency. On low notes the speaker doesn't know it's in a box. It makes a long throw, but not much audible bass.
3. An OPEN baffle board. This means one board, not a solid box with six sides. These open boards are found in many place--behind the seat of a truck, laying over the well in the rear of a hatchback, covering the trunk area of a hatchback, fastened in place of the rear seat in a sedan, or behind the back seat in the trunk of a sedan.
4. The REAR DECK. (usually for six by nines or four by tens) Not a good baffle for powerful bass.
5. The PANELS in cars, trucks and vans.
6. Any baffle that aims heavy speakers (tens, twelves, or fifteens) UP or DOWN. DOWN is not as bad as UP, but a heavy cone will sag from the pull of gravity and come to rest out of the magnetic gap. This will cause distortion, loss of power, and a possible mechanical failure of the speaker.
As you can see, many people have no choice but to use BAD baffles in their vehicles. Nevertheless, they need to be aware that when they do, they are placing their speakers in mechanical jeopardy. Many people think that a trunk or a door panel is equivalent to a solid box. It's not, and the price to be paid is in poor transient response, failure to generate good low frequencies, and increased risk of premature mechanical speaker failure. Extended usage in bad baffles at high power levels in the bass range can lead to these mechanical failures:
1. The spider can be torn.
2. The surround can be torn or worn out.
3. The voice coil can be thrown out of the magnetic gap, permanently, or temporarily, the latter deforming it and making it useless. (Sometimes this is caused by a VERY large transient.)
4. The voice coil can also be deformed by hitting the bottom of the magnetic structure. This could be a speaker design problem, but good compliant speakers should be able to travel almost one tenth of their cone diameter safely.
It should be mentioned that excessive speaker excursion is not a problem in small sealed boxes. It can be a problem in very large sealed boxes.
B. OVERPOWERING THE SPEAKER LEADING TO A CHARRED VOICE COIL
This type failure can happen at any frequency, not just the bass range. When people talk about blowing a speaker up they usually mean that excessive wattage caused a thermal failure of the voice coil. That type failure means that part of the voice coil became short circuited, or open, or deformed so that continued movement is impossible or very noisy. EVERY speaker voice coil can be burned up.
What does a burned (charred) coil look like? You can't tell until the cone and spider are cut out and the coil pulled out of the gap for inspection. However, sometimes the dust cap can be removed and you can see a melted Kapton voice coil former (It goes at 750 degrees.), or bubbles in a paper or aluminum former, or even charred wire. A new voice coil is a neat little cylinder of bright copper colored wire. When operated at its rated power it turns brown. When operated above its rated power it turns black. The coil could delaminate (come unglued from itself) before it turns black. THIS SHOULD BE COVERED BY THE MANUFACTURER'S WARRANTY. But once it turns black, it s ABUSE. Excessive heat can expand the voice coil wire and the little cylinder will not be neat anymore. Eventually the wire may become unbonded and create a short or open circuit.
Thermal overload cannot be fixed in watts. A speaker takes in heat (watts), and it can dissipate heat into the air. If the air is HOT the speaker can't handle as many watts. Power handling goes way down in the summer with a speaker in the trunk. Don't put a hot amp under a speaker or in the enclosure with it.
The wire I'm test'n isn't doin' what it's supposed to be doin'... I am so glad I printed that tech sheet, with the wrong info.
Do it right the first time... or I might have to fix it for ya
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