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HELP blown speakers

Here is my situation. I am using a set of Silverline Sonata Mk 1 speakers with Pass Aleph 2 amps and a Pass Aleph P preamp for the monitoring in my home recording studio. The Aleph P is fed from a MOTU 2408 Mk 3 Audio interface/sound card that is in turn fed by a Power Mac G4. I run all my signals through a single set of stereo outs on the 2408. All the mixing is done via software in the computer (no mixing board)The effects (reverb etc...) that the computer can generate can go from smooth and lush to downright hashy digital grungefest.

I was working on a piece of music yesterday and using an effect that can tend to produce some peaky loud transients at certain moments. Never would I say the volume exceeded 95 db. I do know that more than once I'm sure the output of the 2408 was overdriven. I was noticing that the sound had a definite distorted quality about it, but I thought that it might have something to do with the effect I was using. I started to try and figure out what was causing this and I ended my search at the speakers. It seems that both speakers have suffered damage. I confirmed this by hooking up another set of speakers, which sound fine. The sonata speakers have 2 tweeters each, and it seems that on both speakers they are damaged. The produce sound, but it is definately distorted, I don't think that the midrange and woofer is damaged, though I'm not entirely certain.

What would cause this? I didn't have the preamp volume to high, and I never played the speakers that loud. I'm pretty sure that I have caused major damage to the speakers. I'm sure I can replace the drivers, but I want to make sure this doesn't happen again. Is it possible to overdrive an input on a preamp to the point where it can damage the drivers even though the preamp is not feeding the amps that high of a signal?
128x128ejlif
marakanetz's avatar
marakanetz
5,473 posts
 
Viridian,
I believe into my poor knowlege of the speaker's internal structure but in reality, the rectangular and saw-shaped splashes due to improper re-locking and/or jitter in digital-to-analogue domain have the huge spectrum from DC components way upto 10x harmonics. X-over caps might not even have enough time to smooth-out such splashes and pass this all junk onto the coil and it probably doesn't neccesarily have to be DC.

Right now I believe that not only tweeters suffer but woofers as well

There also could be solution to use cheap tube buffer such as Musical Fidelity X10 since tubes do not operate on such high freequencies as transistors.
ejlif's avatar
ejlif OP
1,366 posts
 
Thanks guys for all the valuable information. I have been using the Silverlines and Pass amps for some time with no problems. Recently I did add the Pass preamp and got rid of my mixing board. The sound is so much better than the Mackie mixer I was using, I would hate to give up the what the Aleph P adds to the sound of my system.
jcbtubes
400 posts
 
I side with Mech and others on this. A relatively inexpensive audio card can produce unhealthy ultrasonic garbage, whether during clipping or simply as a byproduct of a poor digital filter. It can further cause oscillation or instability in wide-bandwidth amplification stages, like many ss electronics. Whether additional equipment instability occurs or not, this ultrasonic junk will slowly cook your tweeter and/or high-pass x-over components.

Also, don't assume that because a circuit uses tubes that it is limited enough in bandwidth to help in your situation. A good tube pre-amp or buffer stage can easily be flat to 30kHz, and some much higher. If the problem is with sample rate spiking or distortion products within its passband, they will easily be passed downstream to the next component. Mech's suggested solution is sounding better and better. Good luck.



ejlif's avatar
ejlif OP
1,366 posts
 
I talked to Silverline and it appears that the midrange driver is what failed. Apparently these are rather fragile compared to the other drivers in the speaker. I'm gonna replace it and keep my fingers crossed. Thanks for everybody's help.

-Ryan
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rnbowers
6 posts
 
I'm going to correct a few of you on your statements on sound cards. While you are all correct that the average sound card will produce some harsh and undesireable digital artifacts, the cards that are used in recording applications, such as the higher end Turtle Beach and Delta cards are designed to filter this out. It would not do to record without filtering that sort of hash out.

Ejlif, I'd encourage you to look at the information that came with your card and see what it's input and output stages are spec'd out for. Find out if they are using op-amps or if they have more sophistocated preamps and processors in them.

Best regards,
Roland
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