Tuesday Tech Talk questions

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Giri

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Tuesday Tech Talk questions
« on: 14 Nov 2019, 06:54 am »
Hello Danny,

Coming here from your Tuesday Tech Talk series of videos. I must acknowledge that your talks are the best when it comes to presenting technical knowledge in a practically understandable manner. Definitely a step up from the popular PS Audio channel, which simplifies it down a bit, apart from endorsing exotic cables :)
I hope you continue the video series into the future too.

I have a few questions on the open baffle video;

1) Why did you prefer U-fame design for NX-Otica over H-frame? Is it a matter of visual/manufacturing preference or sound quality?

2) You used U-frame at an angle of 8 degrees to avoid internal resonances. Did you arrive at the angle based on experimentation only or there is  mathematical justification behind it?

3) What is the principle that guides the length of the unequal wings used for the mid-range?

4) This question is about stacking drivers in a line. Am I correct in understanding that the high crossover frequency should be should have a wavelength greater than the distance between the drivers in order for the cancellation of frequencies to occur?

5) This question is about double driver H-frames. In a H-frame, does it matter of the drivers are stacked one over the other, vertically or if they are stacked horizontally, next to each other? Would the frame behave as a single driver, irrespective of the number of its constituent drivers, as long as the drivers are close together?

Thank you.

Danny Richie

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Re: Tuesday Tech Talk questions
« Reply #1 on: 14 Nov 2019, 01:55 pm »
Hello Danny,

Coming here from your Tuesday Tech Talk series of videos. I must acknowledge that your talks are the best when it comes to presenting technical knowledge in a practically understandable manner. Definitely a step up from the popular PS Audio channel, which simplifies it down a bit, apart from endorsing exotic cables :)
I hope you continue the video series into the future too.

First off all, thinks for watching.

Quote
I have a few questions on the open baffle video;

1) Why did you prefer U-fame design for NX-Otica over H-frame? Is it a matter of visual/manufacturing preference or sound quality?

It is a continuation of the upper section. Keeping the drivers on the same plane helps keep them in phase with the upper drivers. And at the high crossover point of about 160 to 180Hz that is important.

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2) You used U-frame at an angle of 8 degrees to avoid internal resonances. Did you arrive at the angle based on experimentation only or there is  mathematical justification behind it?

It is actually a 10 degree angle. Again it is a continuation of what is going on above. The angles are really not that relevant within the operating range that they are covering. But it does elevate some back side pressure on the diaphragms.

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3) What is the principle that guides the length of the unequal wings used for the mid-range?

That is the culmination of years worth of development that included a ton of measuring and testing. Check out this example:  https://www.audiocircle.com/index.php?topic=154485.msg1651847#msg1651847

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4) This question is about stacking drivers in a line. Am I correct in understanding that the high crossover frequency should be should have a wavelength greater than the distance between the drivers in order for the cancellation of frequencies to occur?

That's just a rule of thumb in minimizing cancellation effects and allowing the drivers to blend as a single unit. As increased vertical off axis angles occur there can still be time delayed cancellation in most cases.

Quote
5) This question is about double driver H-frames. In a H-frame, does it matter of the drivers are stacked one over the other, vertically or if they are stacked horizontally, next to each other? Would the frame behave as a single driver, irrespective of the number of its constituent drivers, as long as the drivers are close together?

Because the wavelengths that they are covering are so long in most cases then it doesn't really matter which way they are turned, and they do act as a single driver.

Giri

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Re: Tuesday Tech Talk questions
« Reply #2 on: 15 Nov 2019, 09:18 am »
Quote
I have a few questions on the open baffle video;

1) Why did you prefer U-fame design for NX-Otica over H-frame? Is it a matter of visual/manufacturing preference or sound quality?

It is a continuation of the upper section. Keeping the drivers on the same plane helps keep them in phase with the upper drivers. And at the high crossover point of about 160 to 180Hz that is important.

Could please you explain further? I thought all the drivers can be brought to the same plane in the time domain, through DSP. What is the significance of the high crossover point?

Quote
2) You used U-frame at an angle of 8 degrees to avoid internal resonances. Did you arrive at the angle based on experimentation only or there is  mathematical justification behind it?

It is actually a 10 degree angle. Again it is a continuation of what is going on above. The angles are really not that relevant within the operating range that they are covering. But it does elevate some back side pressure on the diaphragms.

How is elevating the back side pressure on the diaphragm advantageous?

Quote
3) What is the principle that guides the length of the unequal wings used for the mid-range?

That is the culmination of years worth of development that included a ton of measuring and testing. Check out this example:  https://www.audiocircle.com/index.php?topic=154485.msg1651847#msg1651847

You literally did gave the farm away with that post.
If I understood correct, it's a matter of experimentation, more than anything else. Or is a 2" shorter wing a decent rule of thumb?

Danny Richie

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Re: Tuesday Tech Talk questions
« Reply #3 on: 16 Nov 2019, 05:04 pm »
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Could please you explain further? I thought all the drivers can be brought to the same plane in the time domain, through DSP. What is the significance of the high crossover point?

I try to avoid DSP manipulation, that often causes aa lot of other drawbacks.

Regardless of that it distance of the acoustic centers is still very important for the drivers to blend well.

This one might help a little:  https://www.youtube.com/watch?v=HByEmfg7kis&list=PLUFNGRKZZWXzCt2Syx4yjR4Oy7V-uiePB&index=19&t=10s

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How is elevating the back side pressure on the diaphragm advantageous?

So long as the driver doesn't need back pressure for control or as part of the total Q then taking away that pressure reduces stress on the cone and can allow upper ranges to be a bit more transparent.

Quote
You literally did gave the farm away with that post. If I understood correct, it's a matter of experimentation, more than anything else. Or is a 2" shorter wing a decent rule of thumb?

Experimentation is best because it is really hard to model. Plus it is real easy to swap out side wings. For measuring purposes they can even be cut from Styrofoam. And you can see the effect immediately and then replicate it in MDF.

Giri

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Re: Tuesday Tech Talk questions
« Reply #4 on: 18 Nov 2019, 02:58 am »
Quote
Could please you explain further? I thought all the drivers can be brought to the same plane in the time domain, through DSP. What is the significance of the high crossover point?

I try to avoid DSP manipulation, that often causes aa lot of other drawbacks.

Regardless of that it distance of the acoustic centers is still very important for the drivers to blend well.

This one might help a little:  https://www.youtube.com/watch?v=HByEmfg7kis&list=PLUFNGRKZZWXzCt2Syx4yjR4Oy7V-uiePB&index=19&t=10s

The actual physical distance matters for the room reflections is affected, even if the on axis distance can be manipulated in the time domain with DSP. Did I get it correct?

Quote
How is elevating the back side pressure on the diaphragm advantageous?

So long as the driver doesn't need back pressure for control or as part of the total Q then taking away that pressure reduces stress on the cone and can allow upper ranges to be a bit more transparent.

Danny, I wonder if you meant "alleviate" and not "elevate". It makes more intuitive sense to think a 10 degree outward taper reduces the back pressure. Or I must have missed some critical detail.

Quote
You literally did gave the farm away with that post. If I understood correct, it's a matter of experimentation, more than anything else. Or is a 2" shorter wing a decent rule of thumb?

Experimentation is best because it is really hard to model. Plus it is real easy to swap out side wings. For measuring purposes they can even be cut from Styrofoam. And you can see the effect immediately and then replicate it in MDF.

Styrofoam is pretty cheap and the test set-up is quite doable. Thanks for the tip.

Giri

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Tuesday Tech Talk: Selecting Drivers and Why it Matters
« Reply #5 on: 18 Nov 2019, 03:55 am »
Hello Danny,

Your talk about driver selection was quite informative, especially about how expensive components in a poor design can drive the price up without complimenting performance. I was pleasantly surprised that you mentioned Peerless Audio India as a preferred supplier. I wrote to them several years go asking quotes for drivers etc. But as I recently rekindled my desire to build a DIY stereo speakers, I was glad that market is now inundated with imported choices. I looked at Peerless as some cheap manufacturer for local markets. Maybe their website put me off and I didn't know any better. Your endorsement of their engineering, quality control and professionalism impressed me and I sense your endorsement doesn't come easy.

1) I am looking for a woofer and lower mid range drivers for open baffle use. Can you recommend any of Peerless drivers for the purpose? What are you recommendations from their line of products, for a newbie DIYer, in general?

2) I want to suggest a couple of topics/themes for your future Tuesday Tech Talks;

    i) Most audio reviews seem very subjective. It would be interesting to see a very well reviewed speaker measures out in reality. Also,
    commentary on what insights the measurements can provide into the design process. One candidate can be from your own GR Research stable
    and another from any of the popular loud speaker brands.
    ii) The electricals, viz., amplifier selection, wiring, wire gauge, connectors, power supply plug hole ratings, types of power supplies etc.

Thank you

Danny Richie

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  • Posts: 12793
    • http://www.gr-research.com
Re: Tuesday Tech Talk questions
« Reply #6 on: 18 Nov 2019, 05:11 pm »
Quote
The actual physical distance matters for the room reflections is affected, even if the on axis distance can be manipulated in the time domain with DSP. Did I get it correct?

You can delay one driver in time verses another using DSP, but only for one point in space. Move up or down and all the correction for for nothing. So driver spacing is very important. A wide spacing means phase relationships (differences in time arrivals) change more easily with different distances.

Quote
Danny, I wonder if you meant "alleviate" and not "elevate". It makes more intuitive sense to think a 10 degree outward taper reduces the back pressure. Or I must have missed some critical detail.

Yes, thank you.

Danny Richie

  • Facilitator
  • Posts: 12793
    • http://www.gr-research.com
Re: Tuesday Tech Talk: Selecting Drivers and Why it Matters
« Reply #7 on: 18 Nov 2019, 05:31 pm »
Quote
Hello Danny,

Your talk about driver selection was quite informative, especially about how expensive components in a poor design can drive the price up without complimenting performance. I was pleasantly surprised that you mentioned Peerless Audio India as a preferred supplier. I wrote to them several years go asking quotes for drivers etc. But as I recently rekindled my desire to build a DIY stereo speakers, I was glad that market is now inundated with imported choices. I looked at Peerless as some cheap manufacturer for local markets. Maybe their website put me off and I didn't know any better. Your endorsement of their engineering, quality control and professionalism impressed me and I sense your endorsement doesn't come easy.

They make drivers for a lot of companies. They won't be real responsive to an individual though. They are not set up for small runs of drivers.

Their engineering and quality are top notch. They came to visit me back in the spring. I took them to a local BBQ for lunch. They loved it.



Quote
1) I am looking for a woofer and lower mid range drivers for open baffle use. Can you recommend any of Peerless drivers for the purpose? What are you recommendations from their line of products, for a newbie DIYer, in general?

Have a look at these kits: http://gr-research.com/obseries.aspx

Quote
    i) Most audio reviews seem very subjective. It would be interesting to see a very well reviewed speaker measures out in reality. Also, commentary on what insights the measurements can provide into the design process. One candidate can be from your own GR Research stable and another from any of the popular loud speaker brands.

Unfortunately some reviews are really creative writing, and not a real review with real comparisons.

I have designed commercially available products that are well known and have received tons of awards. Those are usually good for making comparisons. That way I am really comparing my own products to my own products.

Quote
    ii) The electricals, viz., amplifier selection, wiring, wire gauge, connectors, power supply plug hole ratings, types of power supplies etc.

I am trying to avoid some of the topics that will just turn into a subjective verse objective debate with the flat earth community.

Captainhemo

Re: Tuesday Tech Talk questions
« Reply #8 on: 18 Nov 2019, 05:46 pm »
Another thing to  mention regarding digital time alignment  in OB is that you are dealing with front and rear firing  waves.  So delaying one will delay the other as well.
Physically aligning the   vc's  is  the way to go

jay

Giri

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  • Posts: 5
Re: Tuesday Tech Talk: Selecting Drivers and Why it Matters
« Reply #9 on: 19 Nov 2019, 03:47 am »
They make drivers for a lot of companies. They won't be real responsive to an individual though. They are not set up for small runs of drivers.

I wrote to them 8 years ago with a very general inquiry and near zero knowledge but they responded quite elaborate and with a kind offer of assistance, probably sensing that I was out of my depth.
They have some of they products listed on their site. I can give another try.

revg1952

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  • Posts: 82
Re: Tuesday Tech Talk questions
« Reply #10 on: 19 Nov 2019, 06:00 am »
. Episode 20 ( and all of them).Continued common sense, excellent insights, expertise, wisdom and some humor;always look forward to Tuesdays.
RevG