Blown RS28 Tweeter

[m1ke323]

I made a post about this is the TMWW thread but I wanted to make a thread out here to get a quicker response becuase I am kinda worried and anxious about the answer.

I finished my crossovers for my TMWW towers on friday and installed the first crossover in one of the speakers. I then went and hooked up the one TMWW to my Rotel-1080 amp and listened to it for about a half hour. It sounded great until my RS28 tweeter blew.

Most of that half hour my volume was at -20db to -10db on my Denon-2807 receiver but I did push it up to reference level of 0db. Keep in mind the receiver goes up to +15 or +20db.

The Rotel-1080 shouldn't have broken a sweat pushing these guys so the amp wasn't clipping. I am pretty much stumped as to why it would blow.

Like I said in my other post, the only part of my XO that is iffy is the connection where all 3 positives hook up to the terminal plate. Same goes for the negatives. I am using Apex Jr's 11AG speaker wire and the stuff is thick. Trying to connect 3 of them together makes a big ball or wire and solder. I thought maybe the tweeter positive is making a better connection and gettign more power. But all of the speakers were playing fine until the tweeter blew, so all of them were gettign power. So I am out of ideas.

Also, is there any sort of power regulator I can solder into the tweeter XO so this doesn't happen again. I do like to listen to movies pretty loud and don't want to have to worry about blowing my tweeter all the time.

Thanks
Mike

[ThomasW]

I finished my crossovers for my TMWW towers on friday and installed the first crossover in one of the speakers. I then went and hooked up the one TMWW to my Rotel-1080 amp and listened to it for about a half hour. It sounded great until my RS28 tweeter blew.

But all of the speakers were playing fine until the tweeter blew, so all of them were gettign power. So I am out of ideas.

Which was it, one speaker playing or several?

If only one speaker was playing, the tendency is to raise the output level to equal that of 2 speakers, since that's what people are used to....

The pre-amp dB output setting doesn't tell you anything about the transients that were being played. The amp certainly could have clipped.

Could be a defective tweeter. Could be the crossover. Hard to know without more info.

[m1ke323]

Well here is whole situation. I have 5 klipsch speakers that I am using in 5.1 surround and I plan on replacing them all with DIY ones. The klipsch are all smaller bookshelf speakers.

I usually watch movies with the Klipsch speakers at like -10db and they are pretty loud but not nearly as loud as the single TMWW was when it was -10db. I listened to the single TMWW speaker for about a half hour at -20 to -10db. It was unusally louder at these volume then any other speakers I have. More efficient maybe? This was only 1 TMWW hooked up too.

I very rarely but sometimes listen to movies at 0db for big action movies. So I turned it up to 0db on the receiver and the TMWW tweeter blew. Every speaker I have hooked up like this has no problem going up to 0db.

I heard you ThosmasW that the db output doesn't tell my much but I don't know how to explain this then. I was listening to music at the time the tweeter blew and there were some pretty high vocals. Either way I am suprised the tweeter would blow? Is there some sort of power regulator I can solder in?

Thanks for the quick reply, I appreciate it
Mike

[ThomasW]

The speakers you've used, or the output level setting for those speakers is irrelevant to this situation.

If the only speaker playing was a single TMWW, then it's quite likely you were running it at a output level equal to that of several speakers. That's just how humans work. If that's the case, the tweeter was either overpowered or it was defective. If it smells like burn insulation then it got too much power.

The dB setting on the pre-amp tells you nothing about how much power is actually being used. High power transient peaks will be played, and they'll happen in milliseconds regardless of the volume setting on the preamp.

The only way to know what happened is to duplicate the situation again, and measure the power at the tweeter as it blows. Obviously that's a bit $pendy....

There's nothing that will fail-safe a tweeter unless you put something like a thermistor in the circuit. Those will open when heated by high power levels and cut the signal to the tweeter. When the power level drops they'll cool and the signal will return. They're somewhat better than using a fuse, since most fuses (even fast-blow) don't function fast enough to stop a transient.

In cheap speakers they put a small light bulb on the tweeter circuit. As the power levels rise it's shunted and the blub lights up. That also protects the tweeter.

Edit....New speakers of high quality can be very deceptive since they play louder with lower distortion than your old ones. So it's likely you were listening at a higher SPL that normal because distortion is the cue to turn it down, and the TMWW would be really loud before you started hearing distortion.

[m1ke323]

Hmm, everything you have said makes sense to me ThomasW. It is possible I was trying to compensate for only have 1 speaker and turning it up louder. But it still has me worried for when I have 2 speakers that I will blow a tweeter.

Do you think it is possible my Rotel-1080 rated at 340wpc at 4ohms was clipping? I would have though the Rotel would be able to handle the TMWW's with ease?

Do you recommended I install something to protect the tweeter. Also won't a fast blow fuse blow everytime there are peaks? I was thinking something more along the lines of slo blow fuse or a thermistor like you said. I really don't know anything about these though and what would be best suited for my purpose. What do you recommended?

Thanks for the help again

Mike

[m1ke323]

I just removed my tweeter and compared it to my old one.

The black cone underneath the protective mesh is shattered on the one I blew. I am not sure if this helps with your evaluation of what happened.

[BobEllis]

Shattered dome smells like major overexcursion. Are you ABSOLUTELY sure that you did not reverse the connections for the mid and tweeter? Triple check all of your crossover wiring. I'll bet that's where your problem lies, unless you were wearing earplugs when you blew the tweeter.

[m1ke323]

Well I found out that I never reversed my connection on my RS150 like the plan calls for. I connected all the speaker positive to the positive wires and the same for negatives.

How would this cause the tweeter to over exert itself though?

[ThomasW]

It's impossible to know the cause of death without reproducing the situation again. My educated guess is that you killed it..

It's difficult to explain, but a musical transient can occur so fast (read paragraph below) that even a fast-blow fuse can't melt quickly enough to protect the tweeter. They can help, but they aren't a fail-safe guarantee.

The amp has more than enough power to destroy a dozen speakers that size. But that's not the point...we're dealing with things that are occuring almost at the speed of light. So there's not much that can completely save any speaker if the situation to kill it has been set-up. And that is big amp playing loud and a transient (surge created by a musical instrument) occurs.

When CD's first came out they did some studies, one showed it could take up to 500 times more power to play certain musical transients. That's what kills speakers.

So use a SPL meter, it will give you an educated but not too accurate guess as to loudness.

[ThomasW]

Well I found out that I never reversed my connection on my RS150 like the plan calls for. I connected all the speaker positive to the positive wires and the same for negatives.

How would this cause the tweeter to over exert itself though?

It wouldn't..... but.....

It would be out of phase. So it won't sound as loud as if it were in phase. That might have caused you to turn it up the volume to compensate.

[m1ke323]

Thanks Thomas, my plan right now is to finish both speakers up, double and triple check all the wiring and play around with them. I don't have a SPL meter but I am willing to buy one, any recommendations?

With both speakers hooked up I can calibrate my receiver and hopefully all will go well. The Denon is still calibrated for the klipsch bookshelves so hopefully recalibrating it will help too.

I am still considering a thermistor though, the idea of that in my XO would put me more at ease. I have never used one and have no idea of how to calcuate which one I should get though.

Mike

[ThomasW]

I am still considering a thermistor though, the idea of that in my XO would put me more at ease. I have never used one and have no idea of how to calcuate which one I should get though.

That I'll have to research...

[cobbpa]

Isn't the tweeter's 150 watts max rating relevant? 1 speaker being driven is probably getting even more wattage than the 340 wpc amp rating (assuming that's am all channels driven rating). It's possible, if there were a lot of high vocals / instruments playing, that the tweeter saw a lot of that power. As for other speakers going to '0' sometimes...do you know what impedance those speakers were? They may only see roughly half that power at the same volume. Or are these propositions way off track?

[m1ke323]

I should have explained the wpc in this thread too. My klipsch are 8ohms so they only see 200wpc but the TMWW see 340wpc at 4 ohms. I am pretty sure my amp is going to deliver the same wether one speaker is hooked up or two. The Rotel 1080 uses seperate internal electronics for each speaker, I think the only thing the two channels share is the toroidal transformer.

[Dennis H]

Looking at the driver specs, the speaker clearly can't handle 300 watts. You've discovered the hard way what happens when you turn it up too loud. You've already said the speaker was much louder than your old ones so that should have been your first clue. The volume knob means nothing; how loud it's playing means everything. Turn it up too loud, something breaks.

[m1ke323]

Dennis, if my amp was putting out 300 watts, it is not like the single tweeter sees all 300 watts. Isn't the power distrbuted to all the drivers in the speaker. Making it less then 100watts RMS? That is the way I saw it at least. Thanks

Mike

[Dennis H]

Dennis, if my amp was putting out 300 watts, it is not like the single tweeter sees all 300 watts. Isn't the power distrbuted to all the drivers in the speaker. Making it less then 100watts RMS? That is the way I saw it at least. Thanks

Mike

It depends. On average, what you say is true but averages don't mean diddley. What if the only thing playing at a particular moment is a high note? All the power goes to the tweeter, the tweeter goes boom.

[cjd]

Wattage doesn't average.

Power handling of a speaker is limited by the driver(s) with the lowest rating, affected additionally if any are in parallel on the same crossover leg.

I've never driven an RS28A so loud to destroy it without significant and obvious signs of trouble before hand (ok, so I've never destroyed one) - they pop when the VC bottoms out, and they heat up and pick up an interesting "listening through a fan" sound as well.

C

[cobbpa]

edit: CJD answerd a lot of this as I was typing

Indeed; this is why playing sweeps & sine waves is done with caution..such concentrated frequencies can do things..like blow subs....annnnnnd tweeters. As we are building these speakers too, note to self: keep power below 300 watts!

I've wondered a lot about how much power DIY speakers can take. A lot of speaker manufacturers underrate power handling to prevent their woofers from being blown, crossovers distribute the power somewhat, and many power sources are overrated. These things make me think I can send more juice than the individual drivers are said to take, but how much?

[ThomasW]

I'll just pop back in here to add....

Statements like '300 watt speakers', make about as much sense as saying '300 hp tires'...:wink:

[jonathanb3478]

My klipsch are 8ohms so they only see 200wpc but the TMWW see 340wpc at 4 ohms.

What you should say here is that the TMWW's can be provided up to 340w cleanly, but the Klipsch can only be provided 200w.

Part of the issue is that your preamp does not know this, and will ask the amp for what ever you tell it to. I would even say that your amp does not know this, and will try to do what ever the preamp asks it to. I suppose it is possible it has a limiting circuit at some point in the power range, but I would not be surprised if it actually had nothing but a slow blow fuse or several.

It is quite possible you never exceeded 340w on an average basis, even unconsiously matching the level of the 5 klipsch speakers, but that is not impossible. Anyway, it hardly matters. As Thomas has pointed out, if a sudden transient has the amp trying to do way more than it is rated for, (even for just a split second) a lot of that is going to be ugly HF energy caused by clipping, based on what I have heard regarding clipping.

Also, regarding "0" being a fine for the kilpsch, but perhaps not the TMWW, that is quite possible, too. Especially if you picked that as the setting previous to audiable distress in the Klipsch setup at some time in the past.

The preamp really only controls the voltage sent to the amp, as I understand things. The amp then has a "gain rating" that it increases that voltage by, in turn. The amount of voltage on the output is then directly related to how much is put on the input of the amp by the preamp.

The thing is, the exact amount of current (the other half of wattage, besides voltage) is determined by the ohm-load of the speaker. The relationship is such that your pre's "0" setting could be 200w into an 8ohm speaker, but it would be 400w to something that has exactly half their ohm-load. Even that rather beefy Rotel is not rated for 400w at 4 ohms.

Essentially, the same volume setting is not just as safe once you switch speakers. In some cases it could be very close to the same, however.

[cobbpa]

I'll just pop back in here to add....

Statements like '300 watt speakers', make about as much sense as saying '300 hp tires'...:wink:

Right...isn't that what Z rated tires are??
But point taken thomas...point taken.


And jonathon's gain & impedance explanation...I see. Makes sense / sounds right! This is an obstacle in car audio; from idle to accelerating an amplifier's input voltage varies..makes it hard to set levels & gains.

[cjd]

Right...isn't that what Z rated tires are??

nooooo, not quite...

Tires are speed rated, but even that isn't the real story.

Tires are actually *heat* rated. How much heat before they start to fall apart. I've shredded H-rated (130mph) tires going zero mph. And I've never shredded a tire at speed (including 70mph tires I've gone 85 with for a short period). My car conservatively puts only ~140hp to the (front) wheels.

Which is actually very similar to speaker ratings and wattage after all.

And, I made a mistake before: wiring two drivers in *series* will affect power handling. Two in parallel leaves power handling the same as if only one were used.

C

[chasw98]

edit: CJD answerd a lot of this as I was typing

Indeed; this is why playing sweeps & sine waves is done with caution..such concentrated frequencies can do things..like blow subs....annnnnnd tweeters. As we are building these speakers too, note to self: keep power below 300 watts!

I've wondered a lot about how much power DIY speakers can take. A lot of speaker manufacturers underrate power handling to prevent their woofers from being blown, crossovers distribute the power somewhat, and many power sources are overrated. These things make me think I can send more juice than the individual drivers are said to take, but how much?

I'll just pop in here too.
I am running 2 WWMT's, a WMTW, and 2 Modula M/T's with each being fed from amplifiers rated at 600 watts per channel into a nominal 4 ohm load. I have calibrated the "0" point on the pre/pro to be equal to 85 db SPL with pink noise. In reality when I have measured the SPL at the "0" point on the pre/pro with music or movies, the reading is well above 100 db SPL. I have never blown a tweeter and my ears are the best protection I have. My amplifiers also have clip lights that very rarely ever flash on. But I have plenty of headroom for transient peaks that will deliver clean unclipped (i.e. non square wave signal) power to the drivers when needed. Just my experience.

Chuck

[cobbpa]

Tires are speed rated, but even that isn't the real story.

Tires are actually *heat* rated. How much heat before they start to fall apart.

I did not know it was rated by heat; I always figured it was some stress/elasticity rating or something like that used to determine what speed they could take over a sustained period. Very interesting! And yes, thermal handling & physical limits does somewhat relate to speaker handling. Ha. :T

[cjd]

Oh, if we really want to get into tires...

There are other conditions than heat - sidewalls take more strain at higher speeds, so they're usually stiffer the higher the rating. There may be some adhesion properties that fail at higher speeds, but the biggest problem is usually tread separation, which is almost entirely governed by heat. Or, at least, that is my understanding. I suspect I really only know tidbits since I've not spent nearly as much time looking into this (my racing days are no more, though I may take it up again in the future)

and now, back to destroying tweeters and ears... (btw, don't ever try to shred tires at 0mph unless you want your car to smell of destroyed rubber for months after... I was proving to some dumb dad that a 4cyl FWD car could easily eat tires - on a pair I was about to replace, which is why I was at the shop... they let me toast 'em in the lot. )

C

[Jim85IROC]

I have a bit of a different viewpoint than the other guys here. Multiple speakers or not, for you to shatter that tweeter means that you were feeding RIDICULOUS power to it, and I'd be willing to bet that your woofer would have bit the dust long before the tweeter. I've DJ'd on and off since I was in high school, and I've blown lots of woofers, but have yet to cook a single tweeter. When crossed properly, they just shouldn't blow up. I'm using a $.65 tweeter crossed at 2k LR2 in an MTM with a pair of NSBs, and that speaker gets loud enough to irritate me downstairs, and if there was ever a tweeter begging to blow up, it's that one. They've put up with my fiance's reckless cranking so that she can hear it in the shower for over a year now.

My guess is that you've made a mistake in your crossover somewhere that's allowing a full range signal (or close to it) to reach your tweeter. With a full range signal, you'll kill a tweeter pretty quick. It's real easy to mis-position one component or one wire somewhere that results in a complete bypass of the intended filter.

Another possibility (which would cause a nearly full-range signal to get to the tweeter) would be if you inadvertantly wired the tweeter to the RS150 portion of the crossover like mentioned above. If you were to do that, the tweeter would have no low frequency protection.

[m1ke323]

Thanks for the help everyone, I plan on getting both speakers hooked up and checking everything over multiple times. I also plan on triple checking my crossovers again before I hook them up. Thanks again for the help.

Mike

[Dennis H]

Meanwhile, you should be able to repair the driver for not much money. Call PE and ask them if they can sell you a voice coil assembly. dlr's page shows how to replace it. Dome, voicecoil, wires, terminals, mounting plate are all one unit. Just unscrew the old one and screw the new one in.

http://www.speakerdesign.net/dayton_rs/tweeter/reference_series_tweeter.html

[m1ke323]

Thanks Dennis, I will do that today.

[Hank]

IF the tweet were not defective, I have a $20 bill that says there's a crossover wiring error. Outta phase sounds likely.

Statements like '300 watt speakers', make about as much sense as saying '300 hp tires'...

Hail, Thomas! If I never hear of "X" watt speakers again for the rest of my life, I'll be happy!
Anyway, make this a do-over, check your xover wiring and try again. Crank it up slowly and 'listen'.