Sierra 1 & bass distortion?

[883]

Mr. Fabrikant,

If you get the opportunity will you please share with me (I, having shared another incident and the use of Audyssey) if you still believe that the woofer is undamaged and more about the mechanical distress I would hear if damaged? I have since been very afraid to push any significant bass through them, I have set crossover at 50Hz, and while listening to basic orchestral arrangements at moderate volume the speakers have sounded as impressive as ever. I've got my fingers crossed.

[Mag_Neato]

I will add my .02 on Audyssey.

My Marantz AVR with Audyssey MultEQ set my Sierra-1 NrT's to Large. It recognized my 12" Rythmik sub and set distance/level for it. It set the Bass setting to "Mix". Well, I thought setting the Sierra's to Large was fairly typical as they go pretty low in the bass. I left it as set by Audyssey to give it a chance. I thought it sounded OK, but did not knock me over. After looking up the bass "Mix" setting in the manual I discovered that although the sub was calibrated, it was not being fed any bass. All the bass was being sent to the Sierra's. HUH?? How crazy is that?! Of course I fixed the settings. Sierra's set as Small, 80Hz X-over, "Yes" for sub. Sounds much better now.

Never trust these auto setup systems. Manually tweak things so the system works correctly.

[davef]

Very helpful.

You mentioned that I would hear "mechanical distress" with all sources if the woofer was damaged... If you are able to describe, what would this sound like and would it be significantly dependent on volume level and or frequencies (needing to be particularly low)?

I apologize if this is beleaguering the matter but I truly hope my lack of understanding with the Audyssey and speaker combination has not likely (esp. noticeably) shortened the life of or damaged my speakers. I kinda love them.

Thanks again.

Mr. Fabrikant,

If you get the opportunity will you please share with me (I, having shared another incident and the use of Audyssey) if you still believe that the woofer is undamaged and more about the mechanical distress I would hear if damaged? I have since been very afraid to push any significant bass through them, I have set crossover at 50Hz, and while listening to basic orchestral arrangements at moderate volume the speakers have sounded as impressive as ever. I've got my fingers crossed.

Hi 883,

If the woofer is damaged, you will know it... In nearly all cases of a damaged woofer, the voice coil is damaged and will eventually short -- there will be no output out of the woofer at all and the speaker will sound horrible. The other possibility is that the voice coil develops a "rub" -- in which case the woofer cone and suspension will no longer move back and forth freely. In this case, the sound from the woofer will be heavily distorted at any volume level.

Honestly, since you have set a 50Hz crossover and the speakers sound great --- everything is fine, don't worry and just enjoy the system. The woofers in the Sierra-1 are quite durable.

Tale care!

[883]

Thanks for the thoughts Mag_Neato. Nice to know another person's experience with Audyssey and setting up.

[883]

Hi 883,

If the woofer is damaged, you will know it... In nearly all cases of a damaged woofer, the voice coil is damaged and will eventually short -- there will be no output out of the woofer at all and the speaker will sound horrible. The other possibility is that the voice coil develops a "rub" -- in which case the woofer cone and suspension will no longer move back and forth freely. In this case, the sound from the woofer will be heavily distorted at any volume level.

Honestly, since you have set a 50Hz crossover and the speakers sound great --- everything is fine, don't worry and just enjoy the system. The woofers in the Sierra-1 are quite durable.

Tale care!

Thank you VERY much for the reply and for beautiful speakers. Much appreciated. I will enjoy. I suppose I will add a subwoofer since I do use them for movies as well as the music. Although, a sub that will provide the quality of bass I expect from my Sierra 1 will probably not be an option for the time -- this could be a disappointing problem if I want to crank up Michael Murray playing Bach on the pipe organ -- but at least those lower registers will come through without me worrying about abusing the Sierras :-).

Best regards.

[davef]

Thank you VERY much for the reply and for beautiful speakers. Much appreciated. I will enjoy. I suppose I will add a subwoofer since I do use them for movies as well as the music. Although, a sub that will provide the quality of bass I expect from my Sierra 1 will probably not be an option for the time -- this could be a disappointing problem if I want to crank up Michael Murray playing Bach on the pipe organ -- but at least those lower registers will come through without me worrying about abusing the Sierras :-).

Best regards.

It is my sincere pleasure!

Yes, for your usage (especially Bach ) I strongly encourage you to add a subwoofer to the system.

Thanks again!

[ats_phd]

Dave,

Can't the cross over be designed not to allow frequency content less than the designed minimum frequency?

Aravind

[curtis]

Can't the cross over be designed not to allow frequency content less than the designed minimum frequency?

I'm not Dave...but here are my thoughts...

A couple of things...
Not everyone has this issue...in fact, The Dark Knight is known to have a lot of low frequency output. It isn't something you want to do and then end up hindering other material.

In a crossover, you don't want to have to add components if you don't have to. Less is more.

[Dark Ranger]

I'm not Dave either, but here are my two cents.

Generally speaking, crossovers are not "brick wall" filters. Instead, they are "roll off" filters that can be adjusted depending on the requirements. Here is an example:

A typical crossover slope between a subwoofer and a loudspeaker is 12 dB/octave (aka second order crossover). If the crossover centering frequency is 80 Hz, this means that the crossover starts attenuating (reducing) frequencies below 80 Hz to the loudspeakers. For 12 dB/octave, the output at 40 Hz will be 12 dB less than output at 80 Hz. Likewise, at 20 Hz, output will be another 12 dB less than at 40 Hz.

For crossovers inside of loudspeakers, the slopes are usually steeper for several reasons. If memory serves, the low-cut (high pass) filter on the Sierra-1 woofer is 24 dB/octave (aka fourth order crossover). This is MUCH steeper than a 12 dB/octave slope, so the low frequencies are reduced more quickly. Using the same example above, if the low-cut crossover was set to 80 Hz, the output at 40 Hz would be 24 dB less (instead of 12 dB less in the previous example). Here's a visual example of three common crossover slopes used today:



There is a first order, 6 dB/octave filter that isn't shown, but you can see that a 24 dB/octave is much steeper than the 12 or 18 dB/octave slopes. There is a lot more involved with crossovers, but hopefully this helps shed some light on the issue.

To bring this home, the Sierra-1 loudspeaker has an in-room response of -3 dB around 40 Hz, and has a 24 dB/octave low-cut/high-pass filter on the woofer. So at 20 Hz, the output is 24 dB less than at 40 Hz. 24 dB is a lot of attenuation. This is how Dave can control the low frequency output of the Sierra-1, but also shows why the Sierra-1 can still respond to significant low frequency content like what you experienced with The Dark Knight. I actually rewatched this film recently and noted how intense the low frequency content was, even at lower volumes. The woofer moves outward and inward in response to the electrical signal. At mid-range frequencies, it only moves a little bit. At bass frequencies, it moves much more. With extreme low frequencies, the inward/outward motion (excursion) can be so much that you can actually hear the woofer move along with the significant rush of air being pushed out and sucked in via the port (as Dave mentioned).

If you don't plan to use a subwoofer, my honest recommendation would be to keep the 50 Hz low-cut crossover on your Sierra-1s when watching movies. This will help prevent the issue you ran into and give you piece of mind.

[ats_phd]

Thanks Curtis and Jacob !.

It makes sense now.