Markbass Tweeter Attenuator Question

Russell L · #1 10-26-2011, 09:58 AM

Well, on my Traveler 151P cab the tweet doesn't seem to be working. I tried it on two of my buds, and they couldn't tell either. But, first of all, the knob doesn't make sense. "0" is all the way clockwise, then it goes 1-16 counterclockwise and stops at a symbol that looks either like two "o's" or infinity. In the middle is a symbol that says "-dB." I'm assuming that fully clockwise is fully ON and fully counterclockwise is fully OFF. But, I don't hear any difference, neither did my friends. One guy "thought" maybe it sounded brighter fully clockwise.

The tweet is piezo. Nasty little thing, but it might as well work like intended. I emailed Markbass a month ago and haven't heard a word from them. (What's that feller's name on here who represents them?).

So, I'm wondering if it's working at all. My BIG question is, if it ain't working will it hurt anything? Does that mess up the ohms count or change what frequencies are going to the 15" speaker (the built-in crossover is at 3.5kHz)? I don't really need it, but I don't wanna ruin anything. It's been this way since I bought the cab back in May. Seems to play and sound fine, but I really need to know for sure what's going on. If it doesn't hurt anything I'm gonna leave it alone. I plan on getting another one of these cabs as soon as I can save up another $600. Maybe I can tell by the new one if there's any difference.

Anyone wanna explain the attenuator knob to me, and give any other advice. I appreciate it. Thanks.

KJung · #2 10-26-2011, 10:08 AM

An attenuator is just that... it attenuates, i.e., cuts.

At the '0db setting' it is full on, meaning that the tweeter is at maximum volume. As you turn it to the -db side, it cuts, and many circuits are set up so that around noon is 'relatively flat' (i.e., that the much more efficient tweeter is cut enough to be relatively balanced with the woofer).

The piezo tweeter impact very high frequencies versus other tweeter designs, so your bass 'might' not be even putting out much sound way up at the 5K+ range of that particular tweeter.

Also, if you are using a Markbass head, make sure you realize that 'neutral/flat' is all tone controls set at noon, BUT THE FILTERS OFF. If you have the VLE set at noon, all frequencies that would come out of the tweeter are eliminated.

The best way to see if a tweeter is working is to unplug your bass (so there is no way to accidentally hurt your ears), crank the treble control on the amp all the way up and turn up the master a bit. You should then be able to hear the hiss coming out of the tweeter, and can hear how the different attenuator levels impact that highest of high end frequency response.

If you don't hear any hiss, the little piezo is most likely blown, which tends to happen with those cheapo tweeter. Probably easy to get a replacement through Guitar Center.

Russell L · #3 10-26-2011, 10:20 AM

Thanks for that, pal.

Ok, I have tried it set "flat" with no filters on. I'm playing an American series Jazz Bass that is passive. I'm also playing Chromes, so there goes a bit of highs right there.

I will try the test you recommended. So, if the tweet is blown, will that hurt anythig, or will I just simply be tweetless?

KJung · #4 10-26-2011, 10:24 AM

Quote:

Originally Posted by Russell L

Thanks for that, pal.

Ok, I have tried it set "flat" with no filters on. I'm playing an American series Jazz Bass that is passive. I'm also playing Chromes, so there goes a bit of highs right there.

I will try the test you recommended. So, if the tweet is blown, will that hurt anythig, or will I just simply be tweetless?

If you chromes are well broken in, you might not be generating the level of upper frequencies that would be impacted by that particular tweeter (even though Chromes can be quite bright, they don't generate that upper treble sizzle much).

I don't have the technical knowledge to answer than definitively. However, I don't think most piezo tweeters even use or need a crossover, so there should be no issue at all.

Peter Murray is the TBer and North American Markbass rep, and would be able to answer that.

will33 · #5 10-26-2011, 06:09 PM

The 15 should still be getting a full range signal anyway. Most bassamps don't have a true crossover but just a highpass filter on the tweeter. Best thing is to disconnect or remove the little circuit board inside the cab and wire the 15 straight up to the jack. Leave the broken tweeter mounted in the cab just to plug the hole so it doesn't throw off the box tuning.

Those little piezo's are only like $3, easier to just replace it than it is to go about disconnecting parts and rewiring the 15.

DownLowJoe · #6 10-26-2011, 06:23 PM

Russell L

I have several Markbass cabs including ones that have a piezo- and ones with the horn tweeter. My experience is like yours-when I alter the tweeter attenuator it is very difficult for me to tell very much difference. My guess is that your tweeter is working. To make sure my tweeters were working I physically blocked the sound from the tweeter with a cloth and then played. In that situation there was a drastic change so I knew the tweeters were working.

dog1 · #7 10-26-2011, 06:48 PM

Forgive. Tweeters for bass? I have never been able to understand HIGH frequency drivers for LOW frequency instruments. Overtones? Slaps?

If your tweet is blown, the rest of your amp is fine.

Sorry, but even voice is Mid range. Bass guitar should growl.

Russell L · #8 10-27-2011, 06:11 AM

Thanks again, folks. I haven't had a chance to mess with it again yet, but I will this weekend. I'd like to try some of ya'll's experiments.

will33, I'll probably just leave it in there if it's not working. Thanks for mentioning the filter. Hadn't thought of that.

DownLowJoe, so I'm not alone, eh? I'll try your experiment.

dog1, well, see, I like a little sizzle on the high end sometimes. I'm weird, I like old school, but with a tad of modern. My Chromes give me what I want, especially since I also play with my fingernails as well as with the meat of my fingertip. I can go dark or bright. I just wanna make sure whether my equipment is ok or not.

I bet it's working, but just hard to hear it, considering what I'm playing. Maybe try my Strat through it, huh?

will33 · #9 10-27-2011, 08:09 AM

Yeah, running a guitar through it, bridge pickup and turning up the treble, it should be quite obvious between attenuator full on and turned down.

Russell L · #10 10-27-2011, 09:37 AM

Ha, ha, stupid me---I found a definitive answer about how the knob works right on the Markbass site. Full clockwise = FULL ON (i.e-nothing attenuated). Full counterclockwise = OFF. That's pretty intuitive, just as I suspected, but the symbols made it a tad confusing, especially since it's hard to hear any difference.

No wonder they never replied to my email, LOL.

will33 · #11 10-27-2011, 10:07 AM

Quote:

Originally Posted by Russell L

Ha, ha, stupid me---I found a definitive answer about how the knob works right on the Markbass site. Full clockwise = FULL ON (i.e-nothing attenuated). Full counterclockwise = OFF. That's pretty intuitive, just as I suspected, but the symbols made it a tad confusing, especially since it's hard to hear any difference.

No wonder they never replied to my email, LOL.

Ya, it's an attenuator.

Full on lets all the juice through to the tweeter. The more you turn it to the left, the more juice it absorbs and burns off as heat, letting less through to the tweeter, thus making it quieter. The L-pad does this while maintaining a consistent 8ohm resistance though so crossovers and amps work properly.

Those markings are probably guesstimates of how many decibels you're losing as you turn it. Perhaps could've come up with a simpler labeling scheme.