Author Topic: "Small" Thor Measurements  (Read 7633 times)

Offline The Godfather

"Small" Thor Measurements
« on: April 18, 2012, 01:56:30 PM »
Some measurements I have taken of the "Small" Thors I built some time back. I finally got around to using the measurement rig I ordered and am starting to get the hang of things.

Spot any problems, speak up.
















Online DRNB

Re: "Small" Thor Measurements
« Reply #1 on: April 18, 2012, 02:12:18 PM »
They seem to perform better than I thought on the Low end. Interestingly I see the whole response Tilt down towards the HF side, is that the way the x-over was designed? From what I remember the standard x-over didn't have much BSC? Are you still using the standard or the modified version? would be interresting to see the vertical off-axis response, because to my mind the x-over frequency on the original design is too high for an MTM. Although I have never heard a set myself. Based on the dip between 2k and 3k I assume that is the x-over point, so still original?

Looks good overall, and no, I can't spot anything wrong.

"There is no shame in not knowing; the shame lies in not finding out." (Russian Proverb)

Offline Shonver

  • Trade Count: (+10)
  • AVForums Grandmaster
  • *****
  • Posts: 10,788
  • Total likes: 153
  • Criss-cross rhythms that explode with happiness
    • Elipse (under construction)
Re: "Small" Thor Measurements
« Reply #2 on: April 18, 2012, 02:16:04 PM »
Measurements look good. FR dip just above 10kHz does look strange, though I don't think it will sound like there's a dip.
________________

DON'T PANIC
Capie

Online DRNB

Re: "Small" Thor Measurements
« Reply #3 on: April 18, 2012, 02:19:37 PM »
Measurements look good. FR dip just above 10kHz does look strange, though I don't think it will sound like there's a dip.

saw that too, but assumed it might be mic.  :-\
"There is no shame in not knowing; the shame lies in not finding out." (Russian Proverb)

Offline The Godfather

Re: "Small" Thor Measurements
« Reply #4 on: April 18, 2012, 02:37:05 PM »
They seem to perform better than I thought on the Low end. Interestingly I see the whole response Tilt down towards the HF side, is that the way the x-over was designed? From what I remember the standard x-over didn't have much BSC? Are you still using the standard or the modified version? would be interresting to see the vertical off-axis response, because to my mind the x-over frequency on the original design is too high for an MTM. Although I have never heard a set myself. Based on the dip between 2k and 3k I assume that is the x-over point, so still original?

Looks good overall, and no, I can't spot anything wrong.


These are one of the reworked Thors, an MLTL. The low end seems to follow quite closely to what the predicted response should be in King's worksheets for it. This is, as you have correctly guessed, the original crossover. There was much of speculation that D'Appolito didn't do his homework on the crossover WRT the blimp in the magnesium woofers, so I was looking for that but as you can see there is nothing evident. ITO off axis response .. mmm will get back to you on that one :)

There are two things I suppose you should consider when looking at the X-over point. The seas graph for the Millenium shows it under a filter at 2.5k. I wonder how ragged it starts becoming if you lower the XO point? Then there is also power to consider as it is rated at 90W under those data sheet conditions (From 2.5K upwards). Who is willing to test what the power rating is from say 1.6k  :EGrin:

Measurements look good. FR dip just above 10kHz does look strange, though I don't think it will sound like there's a dip.
Looking at the seas graph for the driver you can see the dip it just doesn't look as severe. Their graph isn't to the same scale though but they also don't specify their smoothing which makes a difference. Overall though it matches pretty well so I am happy enough for my first attempt. But i was surpised to find the dip there and it took me ages to convince myself it wasnt me making an error.
« Last Edit: April 18, 2012, 02:39:15 PM by Byrd »

Offline Shonver

  • Trade Count: (+10)
  • AVForums Grandmaster
  • *****
  • Posts: 10,788
  • Total likes: 153
  • Criss-cross rhythms that explode with happiness
    • Elipse (under construction)
Re: "Small" Thor Measurements
« Reply #5 on: April 18, 2012, 02:46:27 PM »
Look at the CSD plot on Zpahaudio.com, and you'll see an anomally above 10k. So it looks like there's a real issue there.

http://www.zaphaudio.com/tweetermishmash/compare.html
________________

DON'T PANIC
Capie

Online DRNB

Re: "Small" Thor Measurements
« Reply #6 on: April 18, 2012, 03:29:53 PM »
There was much of speculation that D'Appolito didn't do his homework on the crossover WRT the blimp in the magnesium woofers, so I was looking for that but as you can see there is nothing evident. ITO off axis response .. mmm will get back to you on that one :)

No I don't think there's a real issue wrt the cone breakup, as is evident in your measurements.
The problem I have is that the bottom to top distance of the midranges is too much for the x-over at 2.5k But I am a little anal about that, and if the tweeter is at the correct height, there should be no issues.

There are two things I suppose you should consider when looking at the X-over point. The seas graph for the Millennium shows it under a filter at 2.5k. I wonder how ragged it starts becoming if you lower the XO point? Then there is also power to consider as it is rated at 90W under those data sheet conditions (From 2.5K upwards). Who is willing to test what the power rating is from say 1.6k  :EGrin:

Th Tryms x-over at 2.6k, and I'm currently crossing my bookshelves at 1.7k.... no issues so far. :nutter:  I have to admit though that I am a little cautious, and would like to add a waveguide at some stage to help ease off the load of the tweeter. Their waaay to expensive to take chances with  ;D
"There is no shame in not knowing; the shame lies in not finding out." (Russian Proverb)

Offline JimGore

Re: "Small" Thor Measurements
« Reply #7 on: April 18, 2012, 03:35:44 PM »
Linkwitz uses a 4th order electrical crossover frequency of 1.4k to 1.5k on the Orions (Seas Millenium) with no issues on power handling.

Whether this is a good idea is another story however.

Ian.

Offline The Godfather

Re: "Small" Thor Measurements
« Reply #8 on: April 18, 2012, 04:04:31 PM »
No I don't think there's a real issue wrt the cone breakup, as is evident in your measurements.
The problem I have is that the bottom to top distance of the midranges is too much for the x-over at 2.5k But I am a little anal about that, and if the tweeter is at the correct height, there should be no issues.

Th Tryms x-over at 2.6k, and I'm currently crossing my bookshelves at 1.7k.... no issues so far. :nutter:  I have to admit though that I am a little cautious, and would like to add a waveguide at some stage to help ease off the load of the tweeter. Their waaay to expensive to take chances with  ;D
It would make me sad if I were to damage mine  :'( Budgetry re-allocation is taking place so not much place for audio budgets.

I bought a MiniDSP last year in order to be able to attempt different crossover configurations. I have attached it, but while sweating and biting my nails. Once i have ensured that the MiniDSP isn't going to destroy my speakers with the off surges I will do some more work on the x-o.

Offline Shonver

  • Trade Count: (+10)
  • AVForums Grandmaster
  • *****
  • Posts: 10,788
  • Total likes: 153
  • Criss-cross rhythms that explode with happiness
    • Elipse (under construction)
Re: "Small" Thor Measurements
« Reply #9 on: April 18, 2012, 04:15:38 PM »
OK. Found a study on MTM crossover frequency and off-axis response.

http://www.birotechnology.com/articles/VSTWLA.html

FWIW, I think that 2kHz is a safe XO frequency to start experimenting with for this class of tweeter. If it starts to honk at you, you know you've gone too low.
________________

DON'T PANIC
Capie

Offline Timber_MG

Re: "Small" Thor Measurements
« Reply #10 on: April 18, 2012, 04:26:02 PM »
The Millenium, 27TDFC and derrivative tweeters both don't mind 1.5kHz crosses. WIth waveguides i've done 1.3kHz with loud levels without issues. The other Seas tweeters are usually crossed around 1.8kHz or higher.

Offline The Godfather

Re: "Small" Thor Measurements
« Reply #11 on: April 18, 2012, 04:28:19 PM »
The Millenium, 27TDFC and derrivative tweeters both don't mind 1.5kHz crosses. WIth waveguides i've done 1.3kHz with loud levels without issues. The other Seas tweeters are usually crossed around 1.8kHz or higher.
What Xo slopes & power were you driving?

Offline tangmonster

Re: "Small" Thor Measurements
« Reply #12 on: April 18, 2012, 05:42:41 PM »
isn't going to destroy my speakers with the off surges I will do some more work on the x-o.

I hope you are planning to build those linkwitz riley boards you bought from me? :)

If you use the power supply board that has the delay on and off muting you really can't damage it.


Offline The Godfather

Re: "Small" Thor Measurements
« Reply #13 on: April 18, 2012, 06:17:45 PM »
I hope you are planning to build those linkwitz riley boards you bought from me? :)

If you use the power supply board that has the delay on and off muting you really can't damage it.


:thumbs:

The miniDSP is supposed to have muting outputs, however they dont work 100% so that is the plan. I tried doing a quasi work around forcing the Mute to engage before the PSU unloads, but it worries me. Going to do it the proper way at the outputs. I was dreading the 8 + 16 switches that I would have to implement, but Shaun convinced me to only do the 8 for single ended.

The LR boards will be when I have fiddled an xover with the minidsp, in about 10 years time :)

Online DRNB

Re: "Small" Thor Measurements
« Reply #14 on: April 19, 2012, 07:13:45 AM »
The LR boards will be when I have fiddled an xover with the minidsp, in about 10 years time :)

now you sounds like me..... I can do a lot in a looong time  >:D
"There is no shame in not knowing; the shame lies in not finding out." (Russian Proverb)