Blown Speaker?

[Bryce_H]

Evening everyone. I am trying to determine what may be happening in my home theater. A couple months ago a got "screeching" through my speakers. It happened again tonight on Rogue One. It usually happens during a loud scene. I'm not sure if this is clipping or something else. My setup is:

Denon 4310CI
Def Tech BP2002 L/R Mains
Def Tech CRL 2002 Center
Def Tech BPX Surrounds
LG BD370 BluRay Player

All speakers connected through 12ga speaker wire with banana plugs
HDMI from BluRay to Receiver

I have checked all connections, all tight
I ensured there were not stray speaker strands

Any thoughts or ideas are appreciated.

Thank you.

 

[TLS Guy]

Obviously the power amp section of the receiver is unstable under the conditions of that loudspeaker load and power delivery. There is every possibility that the receiver would not do it with different speakers.

It is impossible to say whether the receiver is faulty or just does not tolerate the load presented by the DefTechs.

Deftech speakers are a mess and do not sound good. They have speakers pointing back and front. DefTech never publish any useful or meaningful specks on their products. Usually this unstable high frequency oscillation you describe is normally caused by a capacitative load by the speakers that is too high for the amplifier to tolerate. In this case measuring the impedance curve of the speakers would give a lot of insight. Reproducing this problem with the receiver on the test bench could prove very difficult.

In any event these events are highly likely to result in receiver and or speaker destruction.

My best advice is to treat yourself to a significant upgrade in speakers. Deep sixing Deftechs, would always be a good day.

 

[Hetfield]

Another one. Def Tech speakers are just fine. There are a lot of haters. If they are so bad why do they get reviews like this?

And this is from Audioholics too.

 

[TLS Guy]

Another one. Def Tech speakers are just fine. There are a lot of haters. If they are so bad why do they get reviews like this?

And this is from Audioholics too.

The biggest problem with Det Tech is they tell you nothing useful about their speakers and what they do tell you is pretty much fiction. I have heard them and they are ot a speaker I would ever listen to.

Anyhow what you are experiencing sounds very much like amplifier instability from a capcitative load it can't tolerate at high power. This is a bad thing and highly damaging to equipment.

So there are two possibilities. Either the design of the amp does not tolerate the condition of use, or that amp is faulty and is unusually upset by the conditions of use.

The problem is that inducing the fault on the test bench would likely be very difficult and time consuming. So I fear you will end up changing receiver or speakers. A few more episodes of this and may be just one more and you will have a blown speaker and or receiver, of that I'm pretty certain.

I would start with the speaker and measure its impedance curve and phase angles to see if they present the type of load known to induce high frequency oscillation and instability. If nothing turned up there, then the receiver would go on the bench to try and attempts to reproduce the problem.

One last thought I should have asked you before. Do you know for certain, if the screech is coming from the main part of the speaker driven by the receiver, or the powered sub section? I ask this because the powered section of those DefTechs, are well known for failure.

 

[Hetfield]

I don't disagree at all with the BS specs they give. I don't know why they do it because they don't need to.
I have Studio monitor 65 for all 3 channels up front and SM 55 surrounds and a 499 dollar Yamaha receiver from 2008 powering them and not a hint of distress or distortion. I wonder what is going on here myself?
The BS might at some point cause me to move on from this brand. Been thinking about RSL speakers to try or SVS ultra/prime combo in the future.

Sent from my Pixel using Tapatalk

 

[Pogre]

Another one. Def Tech speakers are just fine. There are a lot of haters. If they are so bad why do they get reviews like this?

And this is from Audioholics too.

I wouldn't get too worked up over comments you see about DT. There are just some that can't get past the published specs. While it is bothersome, I still like some of Deftech's speakers. The studiomonitors are pretty good, imo.

TLS isn't your typical audio enthusiast and I think he was talking about a different line of Deftech speakers, as I'm pretty sure he thought you were the OP when he replied to you because he brought up the issue relating to the thread topic.

I have had their speakers (still using Promonitor 1000's for surrounds and do not plan to replace them) and endured those comments for a long time. Like ADTG said to you in another thread, the more you hear it, the louder it gets. Just shrug it off and don't worry about using disclamers. I like the video you posted. I've watched it a few times when I had my 55's, wishing I could have afforded the 65's (which I couldn't at the time).

My Ultras are a nice step up from the 55's, and they'd better be for another $400 in retail. I've heard the 65's in a demo room and thought they were very capable speakers. I'd love to hear them on my system.

Bottom line, if they sound amazing and you're happy with them then just be happy and don't worry about others' opinions. If you run into some money and you're ready to upgrade, make some posts here and you'll get all kinds of suggestions. For now enjoy those SM65's. They're good speakers, imo.

 

[Hetfield]

I wouldn't get too worked up over comments you see about DT. There are just some that can't get past the published specs. While it is bothersome, I still like some of Deftech's speakers. The studiomonitors are pretty good, imo.

TLS isn't your typical audio enthusiast and he was talking about a different line of Deftech speakers, as I'm pretty sure he thought you were the OP when he replied to you because he brought up the issue relating to the thread topic.

I have had their speakers (still using Promonitor 1000's for surrounds and do not plan to replace them) and endured those comments for a long time. Like ADTG said to you in another thread, the more you hear it, the louder it gets. Just shrug it off and don't worry about using disclamers. I like the video you posted. I've watched it a few times when I had my 55's, wishing I could have afforded the 65's (which I couldn't at the time).

My Ultras are a nice step up from the 55's, and they'd better be for another $400 in retail. I've heard the 65's in a demo room and thought they were very capable speakers. I'd love to hear them on my system.

Bottom line, if they sound amazing and you're happy with them then just be happy and don't worry about others' opinions. If you run into some money and you're ready to upgrade, make some posts here and you'll get all kinds of suggestions. For now enjoy those SM65's. They're good speakers, imo.

No you're right. I don't want to come off as defending Def Tech at every turn, because the spec thing is stupid on their part. They design and build great sounding speakers, most people don't buy speakers based on specs so there is no reason to do what they do. The fact that they play games with those numbers takes away from the overall good that they did in designing the speakers and the sound quality. I would like to know from them why they do what they do with the specs myself? Do they know about the complaining and the reputation they have for distorting spec numbers? They must hear it or read it? I bet Gene has let them know more than once?

 

[Pogre]

No you're right. I don't want to come off as defending Def Tech at every turn, because the spec thing is stupid on their part. They design and build great sounding speakers, most people don't buy speakers based on specs so there is no reason to do what they do. The fact that they play games with those numbers takes away from the overall good that they did in designing the speakers and the sound quality. I would like to know from them why they do what they do with the specs myself? Do they know about the complaining and the reputation they have for distorting spec numbers? They must hear it or read it? I bet Gene has let them know more than once?

Marketing. A lot of folks (surprisingly, less educated about speaker specs than a lot of folks here) do purchase audio equipment based on published numbers. Deftech aren't the only ones guilty of this practice either. Even some very respected names are fudging numbers lately as that seems to be the trend. Just look at power ratings for almost any avr on the market today. 130w @6ohm, 1 channel driven... who uses an avr like that?

 

[Bryce_H]

All - thank you for the inputs. A few more data points to help.

I have run this set-up for some time with no issues. It was in our old house for ~5 years in our old house and over a year in our new house before this issue manifested itself.

The speakers are almost 20 years old (I bought them new WAY back in the day)

The subs in the Def Techs are not hooked up as they stopped working

I have a an Energy S12.3 Sub hooked up for the low end

 

[Hetfield]

Marketing. A lot of folks (surprisingly, less educated about speaker specs than a lot of folks here) do purchase audio equipment based on published numbers. Deftech aren't the only ones guilty of this practice either. Even some very respected names are fudging numbers lately as that seems to be the trend. Just look at power ratings for almost any avr on the market today. 130w @6ohm, 1 channel driven... who uses an avr like that?

The AVR specs are WAY out of control. 6 ohms 1 channel driven is just insane. And its from respected companies like Yamaha. That is a very bad trend and a reason to go back to separates even if its less expensive separates like Outlaw and Emotiva. Better off in the end.

 

[Bryce_H]

How do I go about doing this:

"I would start with the speaker and measure its impedance curve and phase angles to see if they present the type of load known to induce high frequency oscillation and instability."

Thank you.

 

[TLS Guy]

How do I go about doing this:

"I would start with the speaker and measure its impedance curve and phase angles to see if they present the type of load known to induce high frequency oscillation and instability."

Thank you.

You do it with one of these.

 

[Bryce_H]

I got thinking...on the amp side (the Denon 4310ci) it should be plenty of powerful enough...right.

 

[lovinthehd]

Maybe not if your spl is high enough to exceed the avr's capabilities....it's a fairly powerful amp section in the avr, but....you might be a candidate for an external amp.

 

[TLS Guy]

I got thinking...on the amp side (the Denon 4310ci) it should be plenty of powerful enough...right.

This is not so much a power issue as a stability issue. Either the receiver does not like the phase angles of the speakers at the power you drive them, or the receiver is stating to fail, and the fault is showing up when the power demands are higher.

An external amp would be one way of solving the problem. If you let it continue, you will likely be replacing the speakers and receiver. That type of high frequency oscillation is a serious problem with a high chance of damaging speakers and the receiver power amps. It is not something you can let continue.

 

[yepimonfire]

This is not so much a power issue as a stability issue. Either the receiver does not like the phase angles of the speakers at the power you drive them, or the receiver is stating to fail, and the fault is showing up when the power demands are higher.

An external amp would be one way of solving the problem. If you let it continue, you will likely be replacing the speakers and receiver. That type of high frequency oscillation is a serious problem with a high chance of damaging speakers and the receiver power amps. It is not something you can let continue.

Wouldn't oscillation be in the mhz region though (i.e. inaudible)?

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[TLS Guy]

Wouldn't oscillation be in the mhz region though (i.e. inaudible)?

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Not always. It can be above the limit of human hearing, but not always, and it can screech like that.

 

[Bryce_H]

So I stopped by my local home theater store (not big box) who are also a Denon and Def Tech authorized dealer. After talking with them for a bit (both the manager and their sr. tech guy) - they were almost certain that the problem was one of the boards on the Denon - either the processor board or the HDMI board. Unfortunately given the age, they indicated it would be very hard (if not impossible) to get replacement parts.


So I used this as a prime excuse to get a new Denon AVR-X4300h!

Will keep everyone posted. Thank you for all the help.

 

[TLS Guy]

So I stopped by my local home theater store (not big box) who are also a Denon and Def Tech authorized dealer. After talking with them for a bit (both the manager and their sr. tech guy) - they were almost certain that the problem was one of the boards on the Denon - either the processor board or the HDMI board. Unfortunately given the age, they indicated it would be very hard (if not impossible) to get replacement parts.


So I used this as a prime excuse to get a new Denon AVR-X4300h!

Will keep everyone posted. Thank you for all the help.

That was probably the most sensible first step.