Need HELP! with my loudspeakers...

[PR116]

I decided to built two loudspeakers myself. Lots of hard work and patience involved but enjoyed though. This is whats inside each well reinforced cabinet:

1 Eminence Delta 15LFA 8 ohm 15 inch Woofer
Nominal Impedance* 8 ohms
Power Rating
Watts 500W
Music Program 1000W
Resonance 39Hz
Usable Frequency Range 42Hz-3.2kHz
Sensitivity*** 96
Magnet Weight 56 oz.
Gap Height 0.375", 9.53mm
Voice Coil Diameter 2.5", 63.5mm

1 Gem GH3910 Compression Midrange with Horn
Large 10 oz. ceramic magnet
Attached 2.2µF crossover capacitor
Power capacity: 50W/150W RMS/Peak (when properly crossed over)
Frequency response: 1K ~ 8KHz
Efficiency: 105dB (W/M)
Nominal impedance: 8 ohms

4 PIEZO SUPER HORN TWEETERS
Fequency: 4K - 27KHz
Impendance: 4 - 8 Ohm
Sensitivity: 94dB
175 watts Peak power (each)

1 CERWIN VEGA CROSSOVERS SPEAKER 3 WAY 400 WATTS
8 OHMS.
400 WATTS PEAK CAPACITY.
PROGRAM: 200 WATTS.
FREQUENCY RESPONSE: 38Hz - 20kHz.
TWEETER WIRES ARE 19" IN LENGTH.
MIDRANGE WIRES ARE 17" IN LENGTH.
WOOFER WIRES ARE 17" IN LENGTH.

When test time came I connected the speakers to my Pioneer integrated amplifier SA-1050 along with an Apple Ipod. It sounded nice til I gave it some volume. In less than a minute my amp smoked, right away did shut everything off. Started searching looking for a why? According to all the reading that I've done so far is that probably was caused by the Piezo tweeters. I treated and wired the Piezo's just like a conventional compression tweeters, parallel and serial combination so I could get an "8 ohms" as a final result and simply connected to the treble in the passive crossover. No resistors nor caps at all, thinking that was unnecessary due to the existence of the crossover. To be honest, the more I read about this issue the more confusion and frustration I get because of the diversity of opinions about it. During my search I came across this site and decided to post about my problem. If indeed the Piezos caused this, all I need is a suggestion on how to wire the four Piezos along with what resistor or caps or whatever combination anybody can suggest, including the elimination of the Cerwing Vega crossover and installing new pieces to all drivers if necessary, based on all the spec info shown above so I could avoid damaging another amp because of my ignorance. Later will post on the proper section about the value of the two resistors (R707 and R708) burned in the amp. I will deeply appreciate if anybody could throw some light in my case.

[Inductor]

I'm not sure about what you have or what you need (only references for one Eminence knowned woofer, from T/S specs and curves). Anyway xovers are different for (normal) tweeters and piezos. Usually a xover from a (no brand) manufacturer says 3-way/piezo, like it should in your case. Unless your "CERWIN VEGA CROSSOVERS" are for connection with piezo tweeters, that you don't refer (or post schematic).
http://www.adelcom.net/MotorolaTweeters1.htm

"If a conventional crossover network is to be used, the tweeter must be made to look "resistive" in order to work with the crossover. This can be done by wiring an 8 ohm resistor /across/ the piezo tweeter. It should be noted, however, that the power efficiency benefits are now lost since the piezo tweeter will look more like an 8 ohm dynamic unit electrically. It will, however, allow the use of conventional crossover technology. If a variable level attenuation is desired, an L-Pad can be used."
http://www.pulsardevelopments.com/pr...l/piezoan.html

[PR116]

Thanks for your reply. No, the crossover mentioned above is just a conventional one, not for piezos. I'll try wiring an 8 ohm resistor across the leads on each of the 4 tweeters and leave the ser/par wiring combination so I could use the actual crossover installed. Does this sound right? Hoping that this will prevent any damage on whichever amp I try next time. Will also see how they sound. Will update post with results.

[PeteMcK]

planet_10 hifi
It is unlikely that the C-V xover will be suitable for your drivers

[PR116]

Ok... by saying "your drivers" you mean only the piezo drivers or all the drivers (including the woofer and mid) stated on the info I provided before. If the answer is only for the piezos, would it make sense if I leave disconnected the wire to the tweeter from the crossover, connecting only the woofer and mid drivers, then connecting the piezos with whichever combination of resistors straight to the rear of the cabinet bypassing the crossover? What would you suggest. Thanks guys for your interest an help. I still have not received the other amplifier to try it out.

[elac310]

A piezo driver has never killed an amp, with or without the usually recomended cap/resistor components connected before to "civilize" it (to avoid it sounds like "tschhh" where it should sound "tssss" etc. ). If that was the case, half of the sound systems on earth would have experienced the same incidents as yours.

Connecting an unknown standard crossover to any speakers is always a risky business.

What I believe is that either the impedance of the system was dropped to levels the amp couldn't handle or there was a short circuit somewhere...

[jleaman]

are you able to post any pictures of the crossover or the wiring you have done ?

Sorry to hear about the smoke being let out of the amp, !!

[PR116]

Here are some pics of the crossover... the only info I have about them is the one I posted at the beggining. I agree with elac310 when he states that either the impedance of the system was dropped to levels the amp couldn't handle or there was a short circuit somewhere... Now the cuestion is if the first was the case would it be possible by wiring piezos to the crossover as compression drivers would cause the impedance to drop down to a dangerous level towards the amp? I still have not received the other integrated amp so I could retest again. I tested the speakers with a friend of mine with a commercial amp system that can handle low impedance, but piezos weren't sounding right. This time I had the piezos wired ser/par with an 8 ohm resistor
shunt on each one connected to the crossover. Went back home and after considering all the info from the web I decided to redo the whole thing. First I disconnected the piezos off the crossover (left only mid compression horn and 15" woofer). Connected all 4 piezos in parallel with only one 4.7uf to the + lead straight to the rear of cabinet off the crossover and for the first time I heard the piezos sound the way they should. Then decided to shunt only the first piezo with a 33 ohm 5w ceramic resistor so the amp (the one that smoked but at relatively low volume still works) would see some source of impedance. By doing this the piezos lost pretty much of its high pitch sound. So I decided to lower the resistance and wired two 8 ohm 5w ceramic resistors in series. This time they sounded almost perfect for my taste. Guys what do you think about this set up. I still waiting for a vintage (I love them) Technics integrated amp so I could retest again and will post results.