Tweeter Diaphragm Problem - Aguilar DB 212 4ohm

[VirtuallyReal]

Ok this is the 2nd time i have to replace the tweeter diaphragm on my Aguilar DB 212, and at $50 each, is a recurring problem i would like to solve permanently.
So, in your experience, what could be causing this recurring problem?

I only use this cabinet with my Aguilar AG500 head, connected via a Speakon cable.

Keep in mind i use this amp mainly at home, and have never (ever) exceeded 3 on the master volume level, and 5 on the gain, with a flat EQ most of the time, and neither of the deep and bright switches engaged.

Also, i always use the -10db switch, since all of my basses are active. The tweeter attenuator is usually set between 80-100 (depending on how many "hiss" noise im willyng to tolerate, as this amps tend to produce a certain degree of noise)

Also, all of my instrument cables have circuit breakers on them (mogami & planet waves), so not a single time this unit has experiences clicks or pops due to and improper connection or defective cable.

I would like to know all the "possible suspects" on this matter... Could it be somethig wrong with the amp?

Is there a way one of my basses could be causing this? I ask this because my pedulla mvp-5 is producing some weird noise when i use it on the bridge pickup, so right now im only using it on the neck pickup (is a PJ mvp)

I took the diaphragm out and noticed some scattered dark spots in it... Compared it with the diaphragm picture on the Aguilar web store and they definitely look different... When i move the diaphragm so it makes contrast towards the ambient light, theese spots looks like oil marks. Structurally, it looks ok, but im no expert so i have no idea how a blown tweeter diaphragm should look like.

Obviously the problem affects the tweeter, its been the victim twice already... all i want to know is were to look for the true source of this recurring inconvenience.

[BassmanPaul]

The oil sounds like it could be Ferrofluid used to cool some tweeters. If you have blown the diaphragm twice you could have a problem with your crossover.

[billfitzmaurice]

Tweeters are blown by overpowering. That can be the result of using distortion or by insufficient slope in the crossover.

[VirtuallyReal]

Thanks guys!
"insufficient slope in the crossover"... hmm... could you please elaborate?
i'm no expert in electronics, so i'm not sure what it means
i know what the crossover is, and i know it filters which frequencies go to which speaker... but the whole "insufficient slope" concept is above my limited knowledge on the subject... an explanation would be appreciated!
Thanks again!

[billfitzmaurice]

Originally Posted by VirtuallyReal

Thanks guys!
"insufficient slope in the crossover"... hmm... could you please elaborate

Passive Crossover Slopes
Cheap systems use first order high pass, which barely offers the tweeter any protection. Second order is generally sufficient for hi-fi cabs, but not for pro-sound. Third order filtering offers the minimum acceptable tweeter protection for pro-sound, fourth order is even better.

[VirtuallyReal]

Originally Posted by billfitzmaurice

Passive Crossover Slopes
Cheap systems use first order high pass, which barely offers the tweeter any protection. Second order is generally sufficient for hi-fi cabs, but not for pro-sound. Third order filtering offers the minimum acceptable tweeter protection for pro-sound, fourth order is even better.

My cabinet is an Aguilar DB 212, any idea about what type of high pass do they use? Aguilar cabinets are not precisely "cheap"... so...

[Aguilar/Dave B.]

Originally Posted by billfitzmaurice

Passive Crossover Slopes
Cheap systems use first order high pass, which barely offers the tweeter any protection. Second order is generally sufficient for hi-fi cabs, but not for pro-sound. Third order filtering offers the minimum acceptable tweeter protection for pro-sound, fourth order is even better.

Filter is not there to protect the tweeter, it's there to modify the sound and control the spectrum content going to the tweeter.
You can't sacrifice the primary function of the filter to achieve the secondary function.
Fourth order would be a very steep slope and would be a bad choice for our cabinet.
For other systems you might choose a differently.

Hope this is helpful.

Dave

[billfitzmaurice]

Originally Posted by VirtuallyReal

any idea about what type of high pass do they use?

I have no idea. The filter prevents damaging low frequencies from entering the tweeter. The lower the slope the less protection, the higher the slope the more protection. If you're blowing tweeters and you're not using overdrive or pushing the cab into distortion then inadequate protection may be the problem.
You also may find this of interest:
http://www.speakerrepair.com/mm5/mer...ter_Diaphragms

[VirtuallyReal]

Thanks Dave for the reply!
Given the situation (2 blown tweeter diaphragms) and the fact that i haven't (ever) used this cabinet above the levels described in the original post, what you guys (Aguilar) think might be causing this issue? there's third diaphragm on the way, and i definitely don't want to ruin this new one also...

Bill: when you say "inadequate protection", are you talking in terms of some built-in protection on the crossover/amp, according to its design, or something regarding the power source?

[bassmankai]

I had that issue on my GS212, it blew twice in about a year. Try running the tweeter lower than 80-100% and watch the amount of high-end your putting through the amp. Since I replaced the last one, I haven't had one blow in about 4 years, and stopped running the tweeter as hot as I used to. Hopefully this helpful, and if the crossover went you would know. It will create a very unpleasant odor.

Kai

[VirtuallyReal]

Originally Posted by bassmankai

I had that issue on my GS212, it blew twice in about a year. Try running the tweeter lower than 80-100% and watch the amount of high-end your putting through the amp. Since I replaced the last one, I haven't had one blow in about 4 years, and stopped running the tweeter as hot as I used to. Hopefully this helpful, and if the crossover went you would know. It will create a very unpleasant odor.

Kai

Thanks Kai; i remember someone told me (here on TB) that heavy use of the attenuator could damage the corssover... that's the reason why i use it between 80-100%... now i'm confused... Dave?

[EricssonB]

I had/have this problem with my Fender Bassman 200. Trouble is that I was being a moron and doing things like taking it to a football field and cranking it, leaving the tweeter plugged in.

Thank God I'm not a teenager anymore.

I've replaced the 1" diaphragm twice, but I somehow burnt out a component of the crossover - working on fixing that this weekend, actually.

And as bassmankai stated, 80-100% seems pretty high.

Oh and don't run microphones thru it with the tweeter on. That gave me an ear ringer as soon as I switched it on. That was the second time I blew it out.

[EricssonB]

Originally Posted by VirtuallyReal

Thanks Kai; i remember someone told me (here on TB) that heavy use of the attenuator could damage the corssover... that's the reason why i use it between 80-100%... now i'm confused... Dave?

Hmm, never thought of that. Maybe that's what damage my crossover!!!

[VirtuallyReal]

I hope Dave can give me an "official", Aguilar-approved suggestion:

- Should i use the attenuator at 80-100%?
- Should i use it at 50%?

What i know for sure is i don't want to get a 4th diaphragm! LOL

[billfitzmaurice]

Originally Posted by VirtuallyReal

Bill: when you say "inadequate protection", are you talking in terms of some built-in protection on the crossover/amp, according to its design, or something regarding the power source?

Tweeters can't handle the power of lows. A 1st order high pass reduces a 100 watt signal to 25 watts one octave below the tweeter pass band, but that's not enough to keep most tweeters from blowing. A 2nd order filter reduces it to 6 watts, and that's much better. But a 3rd order filter reduces it to 1.5 watts, and a 4th order to only 0.4 watts. That's why 3rd and 4th order filters are the standard for pro-sound.

i remember someone told me (here on TB) that heavy use of the attenuator could damage the corssover...

Attenuators burn off unwanted power as heat; the lower you turn it down the more heat it creates. Enough heat can burn it out, so attenuators shouldn't be turned below 1/4. If there's still too much high end turn the amp EQ down, which reduces both power that can overheat the attenuator and also power than can toast the tweeter.

[VirtuallyReal]

Originally Posted by billfitzmaurice

Tweeters can't handle the power of lows. A 1st order high pass reduces a 100 watt signal to 25 watts one octave below the tweeter pass band, but that's not enough to keep most tweeters from blowing. A 2nd order filter reduces it to 6 watts, and that's much better. But a 3rd order filter reduces it to 1.5 watts, and a 4th order to only 0.4 watts. That's why 3rd and 4th order filters are the standard for pro-sound.
Attenuators burn off unwanted power as heat; the lower you turn it down the more heat it creates. Enough heat can burn it out, so attenuators shouldn't be turned below 1/4. If there's still too much high end turn the amp EQ down, which reduces both power that can overheat the attenuator and also power than can toast the tweeter.

...And there's the bottom-line answer i was looking for! thanks to all of you guys for the help!

[lbwdog]

Most problems such as this are caused by operator error, like boosting the highs way too much at high volume, using a lot of distortion at high volume, etc. But it sounds as if you have probably babied it, although you never said what your EQ settings are. Also, you're running the pre gain hotter than the output (master), which would cause overdrive type distortion in most cases, which, if excessive, can cause tweeter failure.

Personally, I like a clean sound, so I run my master way up close to full, while keeping my pre gain lower. I also run my attenuator between 50% and 75% just 'cause I don't require a lot of sizzle.

Still, it doesn't sound like you are doing anything that should cause repeated failure.

[VirtuallyReal]

Ok this is just frustrating. Today i installed the new diaphragm, and the problem remains! I adjusted the attenuator, is now at about 40% (as advised), the master volume at 7, and the gain at 3. The amp still produces an amount of "hiss"' that is too annoying to tolerate (neither of my other (smaller) amps does this). I also installed the previous diaphragm (the one i assumed was blown) and the sound is the exact same, so i ruled out the whole "blown tweeter diaphragm" thing.

The hiss only disapears when i turn the attenuator all the way down, which is not good for the crossover, as you guys told me, and also wipes all the highs from my sound.

Even with no instrument cable connected, i get the exact same noise level when the attenuator is other than "zero".

I bought this cabinet new (Amazon), and i noticed a unusual amout of "hiss" since day 1. I was told (here on TB) that the AG500 amp does produce some hiss, so i assumed this was "normal". Now im starting to belive the i just had the bad luck of getting a deffective crossover on my cabinet... Or maybe there's something wrong with my amp... don't know what to think anymore.

I live outside the U.S., so the obvious solution of taking the cabinet and amp to an Aguilar authorized repair shop is rather difficult and very expensive to me (it cost me more than U.S. $500 to ship this home when i bought it)

So im running out of options here... Last thing i'll do is to try the cabinet with a different amp head, just to check if it makes the same "hiss" noise... If it does, i'll assume there's something wrong with the crossover on the cabinet; if it doesn't, then it might be something wrong with the amp.

Any ideas?

Again, is frustrating to spend over $3,000 on a rig like this, and get a hiss sound so loud and annoying it makes me go for one of my "lower-quality", smaller amps every time i want to play.

I Hope maybe Dave or any of you guys can give me any advise that help me solve this.

[billfitzmaurice]

Tweeters don't cause hiss. They reproduce hiss that's created by the amp.

[lbwdog]

to VirtuallyReal:

Maybe I'm missing something, but I can't find you describing anything other than hiss in any of your posts.

Are the high frequencies distorting, or is it just the hiss?
If so, there's probably nothing wrong with the tweeter.