The Specifications for a JBL Professional M115-8A

By Alexander Rudinski

When you want to fill a room with sound, you need heavy-duty speakers. In most cases, you'll want a set of DJ speakers, or at the very least a public address system, depending on the intended usage and what sort of talent you're dealing with. JBL's M115-8A woofer packs the sort of punch you'll need for a wide range of applications.


The M115-8A is a subwoofer speaker, or woofer, designed especially for the reproduction of low frequencies. The speaker is found in several JBL cabinets designed for a wide range of uses, from DJing to conference presentations. While versatile, this jack-of-all-trades woofer isn't the finest on the market, but it has the power to fill a room.


At 15 inches in diameter, the JBL M115-8A is an average-sized woofer. Even so, it can get loud, capable of reaching 128 decibels, or dB, at its peak power. That's about as loud as a cranked-up rock concert -- or a jet engine -- so you'll be able to fill large rooms with sound.


JBL rates this speaker at 225 watts RMS, or root mean square, and 450 watts of continuous power, while maxing out at a peak load of about 1,000 watts. In practice, this means that the speaker will most often work at about 250 watts, though it is built to withstand four times that power without "blowing out," or damaging the speaker driver.

Frequency Range

On sweep tests, an objective method of measuring a speaker's frequency response, the M115-8A was able to reproduce frequencies as low as 20 Hz, which is the threshold for human hearing, and 1.2 kHz, which is approximately the frequency of human speech or singing. However, in application, the speaker will not reproduce tones this low due to the power of the amplifier. Lower tones need more power, so the more wattage the amp can produce, the lower the speaker can go.

Other Specifications

The JBL M115-8A is an 8 ohm speaker with a recommended amp load of 250 to 500 watts going into the same amount of ohms. Its sensitivity, which is a measurement of the speakers efficiency, is 92 decibels SPL, or sound pressure level. The speaker is a transducer, which is common in low-frequency speakers. The speakers weighs 16 pounds and measures 15 inches across.