Really love my Ampeg BA108 but felt compelled to try to "improve" it.
My first thought was to replace the stock speaker with an upgraded unit.
The Faital 8FE200
is an 8" ceramic-maget woofer that is rated at 130 watts and has an impressive 4.7mm Xmax. Sensitivity is good as well at a rate 95 dB.
I also considered the Eminence Alpha 8A
. The Alpha 8A's Xmax was 3mm so I took a chance and went with the Faital. The Swap
Removing the stock speaker and installing the Faital was a piece of cake. The Faital is a drop-in replacement. Not much more to say. Sensitivity
I have no way to measure absolute sensitivity but I constructed a relative sensitivity measurement system. I laid the BA108 on it's back, speaker pointing up. I mounted my trusty Radio Shack sound level meter to a tripod and suspended it about 10" above the speaker, midway between the driver and the port. I fed my iPhone's speaker output into the CD input on the amp and used a Signal Gen application to provide sine wave inputs into the amp. Once I set the volume of the iPhone and amp, I left them alone. I measured the output at 80, 150, 300, 600 and 1200 Hz first with the stock speaker, then with the Faital. I also played music and measured the output.
80 Hz.......70 dB.......71 dB
150 Hz......80.5 dB....80 dB
300 Hz......77 dB.......80 dB
600 Hz......76 dB.......82 dB
1200 Hz....76 dB.......80 dB
music.......77 dB.......80 dB
From a sensitivity point of view, the Faital is about 3 dB stronger than the stock speaker at frequencies from 300 Hz and above. At 150 Hz and below, the two generate about the same output. Sound
My first sound test was to listen to CD music through each speaker.
The stock speaker lacked any true highs and was quite strong in the midrange (1000 Hz?) region. Music played through the speaker sounded boxy and muffled. Cymbals were non-existent, acoustic guitars sounded muted, vocals were missing any sense of presence.
The Faital opened up significantly. Cymbals can now be heard (though they are not real strong), acoustic guitars ring with some level of clarity and vocals are fairly well balanced. There is no way that you'd mistake this for a true full-range system supported by a good tweeter, but the improvement over the stock speaker is startling.
Results while playing bass through the amp were not so clear-cut.
With the stock speaker, the BA108 has a very good warm, full sound. B string notes tended to be a bit blurry or non-distinct however.
The smoother response of the Faital erases that 150 Hz peak from the stock speaker and all but eliminates that built-in warm sound. Bass sounds smoother and less like a bass. Note clarity is improved however erasing the blurriness that made the lowest notes (low B string) indistinct. Which is better?
The answer to that is "it depends". If you just want an amp that sound warm and full for bass usage only, then the stock speaker will give you that. This is especially true for 4-string players who will avoid the blurriness of the low-B notes.
If you want to make use of the CD input for bass practice than the Faital is a substantial improvement. It makes the amp a better sounding full-range system. I was able to dial enough warmth back into the bass but boosting the lows and cutting mids and highs on the amp's EQ. This way I still had a full sounding amp but much better accompaniment track sound. Other Approaches
I did no analysis on the box tuning, but subjective listening tests suggest the port freq could be raised to fatten up the low end (at the expense of bass extension).
Another possible modification would be to add a midrange to the stock speaker. A midrange with a crossover of say 800 Hz would allow you enjoy the fuller lows of the stock speaker while overcoming the lack of mids and highs. This mod would require a new hole be cut in the front panel and would require a crossover.
- Keith -