Brand new, distorts intermittingly. Used same Speakers with other similer amps Mackie 808 Yamaha etc. with no problem . It sounds good when it does''nt distort

There are repair services on ebay etc but not cheap.

sounds like it could be dust or moisture ...Try cleaning the board and knobs and faders. this may help it may make it worse. Also while at it...check all connections...especially from board to amps. or to outboard gear. Could be a bad chord

Sounds like a problem with the horn amp in that cabinet. This is not a user fixable problem and needs to go to the shop. Here is a link to the Mackie support page where you can find a link to the repair shop list.
Mackie Tech Support

Don't even go there. In my experience these are just not reliable speakers, we have had and heard of so many issues with them we sold our working ones. If one has gone sell the other working one with the dead one as spares and repairs and buy something from QSC, EV, JBL or Yamaha or even Wharfedale Pro.

I'd suspect power supply first - filter capacitors may have leaked/dried out. That would be an easy fix for someone familiar.

It sounds like the rubber around the speakers has perished. Open the cabinet to check. If so, measure the size and order replacements easily on internet. It's a simple job for someone with a little knowhow

I ASSUME that you plugged your guitar into a DI box that then used BALANCED XLR cable to the Mackie board??? The guitar generates line level and the Mackie board inputs are mostly mic level... you will get distortion if you overdrive the Mackie board. You could try going into line level jacks, HOWEVER if you go any distance balanced interconnects must be used. Even the line level jacks require using TRS balanced cables. Try is using a DI box, and preferably one with a gain switch. Also fiddle with the ground lift switch on it for least noise or hum. I use the LiveWire brand DI boxes and they seem to work fine. Then it is important to set the gain with the trim on the MAckie so you don't clip. Also be aware that an acoustic guitar can "hear" speakers and you can get feedback or regeneration that will sound like you are in a cave.

I can't give you much information other than to tell you the idea of adjustable crossovers is to allow adjustments to suit the acoustics of the room or space where they are sited, a function that used to be common but has largely been replaced by the graphic equaliser, popularly used to adjust the sound to suit personal preference but originally was intended to be used with a white or pink noise generator and adjusted to compensate for mechanical and electronic "inefficiencies" of hi-fi systems to produce a pure sound.

The best advice I can offer you is to start hanging with a few hi-fi nuts to learn what you need to know and lots more. Positioning the speakers is very important for a good sound and popular and inexpensive mod is to fit spiked feet to them or lift them clear of the ground on purpose built stands...

If you've changed the tweeter and the sound is still muffled the fault is with the HF amp, or the cross-over. You will have to send the amp assembly for repair as it is all surface mount components in there -nothing you will be able to fix yourself. Sorry for the bad news!

If more than one input is bad, then problem has NOTHING to do with the preamps. Check list:
1. Make sure you are using BALANCED lines everywhere... either XLR or TRS cables.

2. Make sure ALL interconnected equipment, mixers, amps, powered speakers, CD players, etc. are ALL powered from the SAME receptacle or power distribution unit.

3. Do proper setup. Select each channel PFL and set the trims so the indicator never goes into clipping, but is in the 70% range during max volume input to mics, etc..

4. During operation the sliders should be at least 50% up on used channels and the mains. Setting of levels throughout the system is important for noise free operation. Using EXCESS gain at some point results in distortion and noise. Using sliders near the bottom position results in poor signal to noise ratio.

Now re-read #2 above... and believe it. I have seen a lot of equipment blown due to ground bounce of building power. That is why the pro's run power back to their mixer from the area where the amps are powered.