Answered Dali Opticon 6 frequency response

exponential

Well-known Member
Hi all.

I'm hoping someone out there can help me understand the measured response for my speakers.

Here is the spec:

Product series OPTICON
Frequency Range (+/-3 dB) [Hz] 49 - 32,000
Sensitivity (2,83 V/1 m) [dB] 89.0
Nominal Impedance [ohms] 4
Maximum SPL [dB] 110
Recommended Amplifier Power [W] 25 - 200
Crossover Frequency [Hz] 800 / 2,200 / 14,000

So, using DIRAC and a UMIK1 measurement mic, I measured the following:

IMG_20190203_155047.jpg


I understand that the response between 20hz-500hz is purely room related which DIRAC has cleaned up nicely but, and here is my question, why do my speakers tail off so rapidly after the 14khz crossover when they are rated to output up to 32khz?
Is there something wrong with the ribbon tweeters or is this a perfectly normal measurement?

Any help understanding what I'm seeing and what is being measured will be greatly appreciated. Thanks. :smashin:
 

Paul7777x

Distinguished Member
The higher the frequency the more ‘beamed’ it is.

That will have at least something to do with the graph.

If you want to make sure the speakers are working correctly (and I’m certain they are) at those frequencies then you could do a sweep with the mic directly in line with the tweeter... rather than in the listening position.

My Adams sweep looks much the same after about 12-13 KHz.
 

exponential

Well-known Member
Hi Paul.

Ah... It all makes sense now! It's because I'm measuring the room and not the speaker itself!
I'll do a direct speaker measurement next time I break out the mic and laptop. :smashin:

Thanks Paul. :clap:
 

Ugg10

Distinguished Member
As has already been said, if you want the true speaker output measure the tweeters about 30cm on the tweeter axis and measure the bass driver about 5cm from the front of the cabinet on the speaker axis. If they are bi-wired then do one driver at a time and then merge the results. Alternatively measure at 1m on the tweeter axis, do an impulse measurement and gate the result to remove as much of the room interference, the gate setting will be taken from the impulse result.

However, as you can't do anything about the crossover measuring at the seated position and using dirac or other room equalisation tools to smooth the response out is also valid. I would do one speaker at a time and flatten out and then see what the response is for both.

Also make sure you have set up the mic with the provided calibration curve (think this can be downloaded using the mic serial number) this may help the high end.
 

nomore landings

Standard Member
Hi,
As a very happy Opticon (and Rubicon) 6 owner, there may be a simple explanation for the 14k+ roll off.
Ribbons are generally wide dispersion laterally and very limited vertically and the DALis require your ears to be at tweeter height to give their best. Perhaps your mike was placed below this optimum horizontal plane? Regardless of measurements, excellent speakers IMH and biased opinion!
 

exponential

Well-known Member
Hi,
As a very happy Opticon (and Rubicon) 6 owner, there may be a simple explanation for the 14k+ roll off.
Ribbons are generally wide dispersion laterally and very limited vertically and the DALis require your ears to be at tweeter height to give their best. Perhaps your mike was placed below this optimum horizontal plane? Regardless of measurements, excellent speakers IMH and biased opinion!

Hi.

Yeah, I think you may be onto something there to be honest.
Back in my Marantz ownership days using MultiEQ32 + SubHT, I used to religiously set my mic height at the exact tweeter level and do my measurements based on that.
I distinctly remember the measurements which showed my high end tailing off much much closer to the 20khz mark.
Using DIRAC, I now measure at my ear height which is ever so slightly higher than the tweeters.
This may account for the new readings as you suggest.

I'm also going to try a direct speaker measurement as Ugg10 has suggested just to satisfy my curiosity.

I too love my Opticons. They are fantastic speakers and are incredibly detailed.
My only gripe is the dual rear ports which cause huge peaks in the low end.
DIRAC sorts that out nicely however but still, it was my inexperience when buying them at fault and certainly not the speakers fault.
I just can't have them as far away from the wall as I would like. :thumbsdow
I have tried stuffing the ports but, although it does calm down the boominess (when being measured), it distinctly changes the character of the speakers themselves which I didn't like at all.

Cant have it all eh... :laugh:
 

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