Open Aire Aktiv build thread

0 Members and 1 Guest are viewing this topic. Read 9155 times.

Danny Richie

  • Facilitator
  • Posts: 11761
    • http://www.gr-research.com
Re: Open Aire Aktiv build thread
« Reply #100 on: 12 Oct 2017, 10:36 pm »
OK so the green are Mundorf resistors. No good? Also I was told that shunt resistors are not critical. I have them in Mills and can change.  There are some silver coated copper as well as some good copper (I forget if it was OHNO but something reasonably good like that.

I agree with the connectors as I have said it allows me to quickly remove/install to make changes to the XO. I could just eliminate them and solder directly.

Still the Mills is the higher quality resistor, and the shunt resistors are still in the path just like the shunt inductor.

Silver coated Copper causes an audible phase shift in the upper frequency range that is pretty easy to hear in some cases. I tend to avoid it.

Also if you can minimize any break in the wire as it goes from binding posts to components to drivers, then that will help too.

And I understand the connectors allowing you to easily swap parts. Nothing wrong with that. But when you finalize it all then I'd rewire it all with good wire and no connectors. 

jimbones

Re: Open Aire Aktiv build thread
« Reply #101 on: 29 Oct 2017, 05:11 pm »
I have had some listening sessions with friends and they are hearing the dip in Fr at about 175hz between woofers and mid. So I figure that I make the baffle bigger for the mid and take a measurement. No difference then I decide to try to enclose the mid by creating a top and back and extend the sides. So it is a lossy enclosure but I figure I am impeding he rear wave. No dice measurement changes minimally. What am I missing. It shouldnt be that hard to get a mid to go down to 150hz is it?

Danny Richie

  • Facilitator
  • Posts: 11761
    • http://www.gr-research.com
Re: Open Aire Aktiv build thread
« Reply #102 on: 30 Oct 2017, 02:19 pm »
I have had some listening sessions with friends and they are hearing the dip in Fr at about 175hz between woofers and mid. So I figure that I make the baffle bigger for the mid and take a measurement. No difference then I decide to try to enclose the mid by creating a top and back and extend the sides. So it is a lossy enclosure but I figure I am impeding he rear wave. No dice measurement changes minimally. What am I missing. It shouldnt be that hard to get a mid to go down to 150hz is it?

I think I warned you in the beginning that mid was not a good candidate for open baffle. The Qts was a bit low. It could be made to work though.

I would add surface reflections around the drivers. Just increase the wing length to extend the range a little lower. However, extending the range a little lower might me a reduced output too.

jimbones

Re: Open Aire Aktiv build thread
« Reply #103 on: 30 Oct 2017, 02:34 pm »
Yes you did. However we discussed sound "quality" as opposed to output. As I understand it the lower cutoff frequency of the mid in an open baffle is a function of its Fs and baffle wing dimension. In order to get down to 150hz the baffle needs to be about 30 inch  so i put on temporary wings 14 in each side plus the with is 9 inch. No change. Do I need to go to an 8 inch driver? I don't think that will help based on what I see.

Danny Richie

  • Facilitator
  • Posts: 11761
    • http://www.gr-research.com
Re: Open Aire Aktiv build thread
« Reply #104 on: 30 Oct 2017, 06:43 pm »
Yes you did. However we discussed sound "quality" as opposed to output. As I understand it the lower cutoff frequency of the mid in an open baffle is a function of its Fs and baffle wing dimension. In order to get down to 150hz the baffle needs to be about 30 inch  so i put on temporary wings 14 in each side plus the with is 9 inch. No change. Do I need to go to an 8 inch driver? I don't think that will help based on what I see.

If you enclose it on both sides then the upper frequency ranges that it covers will propagate within that space and set up a cavity resonance. You have to keep it open and asymmetrical to avoid the cavity resonance issue.

You could mount four of our M-165 woofers below that mid in a series parallel arrangement to cover from 200Hz down to around 80Hz. Basically build it like the NX-Otica but with your upper section. Then it will easily blend to the servo subs.

See pics of the cabinet:  http://www.audiocircle.com/index.php?topic=141654.msg1510858#msg1510858

http://www.audiocircle.com/index.php?topic=143221.msg1528962#msg1528962

jimbones

Re: Open Aire Aktiv build thread
« Reply #105 on: 30 Oct 2017, 07:35 pm »
Yea, my question was more fundamental, as I want to learn what governs low cutoff frequency> As I see it Qts, Fs and Baffle dimensions. Technically there is no reason why the Mid I have cant reach 150hz. Now it may not "sound good" but I should get down to 150 hz, no??

Danny Richie

  • Facilitator
  • Posts: 11761
    • http://www.gr-research.com
Re: Open Aire Aktiv build thread
« Reply #106 on: 30 Oct 2017, 09:02 pm »
Yea, my question was more fundamental, as I want to learn what governs low cutoff frequency> As I see it Qts, Fs and Baffle dimensions. Technically there is no reason why the Mid I have cant reach 150hz. Now it may not "sound good" but I should get down to 150 hz, no??

Yes, those are the factors to look at. With that woofer the compliance or Qts is low and it needs the loading of an air space (inside a box) to bring the total Q up to an nominal .7 Qtc level. And in an open baffle configuration it is just not there.