Speaker/amp question from speaker Dummy

[RWT]

I recently purchased the following Full Range Driver...
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=289-124

To be driven by the following 2.5 watt amplifier....
http://store.guitarfetish.com/on25waguamdr.html

The project is a home built guitar with onboard amp/speaker.

I am short on the tech specs on the amp. Only that it claims it is 2.5 watts.
Per wiring diagram accompanying the amp, I have wired the speaker directly to the output of the amp (no cross-overs etc...).

Problem - when guitar strings are played with any attack at all, the speaker is obviously overdriven. It Pops, distorts badly, or perhaps even goes silent until the input quiets down. You can see the cone deflect as far seems possible. If the strings are played very gently, sound is quiet but fairly clear (not counting bass, but hey FR driver right).

The amp is designed for this specific application so I doubt it is ill-suited or mis-matched with the application. Have I just grabbed the wrong speaker here? Do I need additional circuitry support for this particular driver? Do I just need a higher power speaker?

I'm not looking for high fidelity here... Just fairly reasonable function.

[CokewithLime]

Ir sounds like it could be a combination of things. A number of questions first.

1. there is no indication of what speaker impedance the mini amp is expected to drive ?? - necessary info

2. is the speaker installed in your guitar body yet ??

3. have you tried turning down your pickup level control and then slowly adjusting the mini amp input level control up and down to see if this helps ???

[RWT]

Thanks Cokew/Lime.
1. Agreed I need the expected Impedence - I am awaiting that answer from the supplier. Can I work that out alternating between a false 4 ohm load and 8 ohm load and measure the amp output power?
2. At this moment, speaker is still outside guitar body just sitting on the table. Not close enough to the pickup for any issue with magnet proximity. No issues with the "airspace".
3. Yes I have played around with those controls. Mostly I end up getting very low volume, or the distortion under "attack". I can reduce input to the amp, and use more "attack", but the volume is still very low.

[CokewithLime]

At this moment, speaker is still outside guitar body just sitting on the table. Not close enough to the pickup for any issue with magnet proximity. No issues with the "airspace".

This could be one contributing factor - that particular driver is not really suitable for OB operation - ie, it needs to be in a sealed enclosure to sound even reasonable - also the fact that is all aluminum cone it is going to have fairly harsh breakup compared to a paper cone driver. It's possible that the voice coil excursion limit of that driver is being exceeded which may be one factor in the poor performance



Yes I have played around with those controls. Mostly I end up getting very low volume, or the distortion under "attack". I can reduce input to the amp, and use more "attack", but the volume is still very low.

If you have a small standalone speaker ( ie computer multi media or better) try temporally substituting it for the small 2" unit and see of the SQ improves - you are now trying to figure out where the majority of the problem is ( amplifier side or speaker side )

BTW - have you used a small screwdriver to adjust the trim potentiometer (blue square thing with a white X on the back of the circuit board) up or down ?? - the manufacture indicates that is used as preamp sensitivity control.

I'm very wary of the manufactures claim that they can get a solid 2.5 Watts with moderate to low distortion levels out of any amplifier circuit that uses a single 9V battery......