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Old 5th July 2017, 01:07 PM   #11
just a guy is offline just a guy  Canada
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Quote:
Originally Posted by David McBean View Post
The Power Compression tool can also be used, rather than having to manually adjust Re.
Yes but I can't use it to good effect. For example I do know that when pushed hard a driver's Re can measure 2x higher than it's original cold value. BUT I have no idea what VC temperature is equivalent to this phenomenon. Either way, predicting power compression is always going to be a rough estimation (as far as I know) so I like to keep the variable in the sim as realistic as possible - I do know Re can double but I'm not as confident specifying that in a temperature related way.
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Old 5th July 2017, 01:21 PM   #12
just a guy is offline just a guy  Canada
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Just for fun, let's look at what good design looks like as far as power compression is concerned. This is a tapped horn I built back in 2009. I designed it but it's basically just a scaled down TH_SPUD with a single much smaller driver. So in effect you could say this is how Danley designs, and if you sim his designs you will see this behavior over ad over.

Some things to note are that under heavy power compression, ideally the low knee will shift just a tiny bit lower. This doesn't happen in your design. And ideally under heavy power compression the frequency response should actually either get better or at least stay moderately viable. Again, this is not what happens in your design.

The only way for the frequency response to stay viable with heavy power compression is to start with a box that seems a bit too large in the first place so the initial low power response looks a bit undamped like so -

Bottom row left - response at low power level
Bottom row right - estimated response under heavy power compression, Re doubled

Note how the frequency response actually gets FLATTER as power is increased and losses incur. What would Danley do? THIS is what Danley would do. Note that this sub is no exception, it also changes character under heavy compression, but at least the frequency response doesn't fall apart into a hot mess.

Click the image to open in full size.
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Old 7th July 2017, 07:26 AM   #13
Mrscy is offline Mrscy
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Just a guy, what modifications would you advice be done on the ROAR series for flatter response?
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Old 7th July 2017, 08:12 AM   #14
Circlomanen is offline Circlomanen  Sweden
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@Mrscy

Just build it as per the plans. The measured respons is much flatter the the theoretical simulated hornresp respons indicates. Hornresp does not account for frictional losses in the tapped pipe sections.

Cheers
Johannes
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Old 7th July 2017, 10:07 AM   #15
Circlomanen is offline Circlomanen  Sweden
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HiFiForum.nu - ROAR-12 på G

There is some measurements a few posts down in the link above. The dark blue line with the word "Mynning" is a near field measurement of my roar12 with a new B&C 12PS100.
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Old 7th July 2017, 11:53 AM   #16
Mrscy is offline Mrscy
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Thanx alot Circlo,
Whats the best way to extract accurate measurements from the plan,must I redraw the plan it in AutoCAD?
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Old 7th July 2017, 02:06 PM   #17
martinsson is offline martinsson  Sweden
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@Mrscy

I'm responsible for the published design documentation of the ROAR series, let me know what measurements are you missing or need to refine and I'll se if I can help you, the ROAR series was designed using CATIA v.5. and I'm not sure about 3d model file format compatibility with the Autodesk suite.

CATIA offers good tools for geometry analysis, such as areas, path lengths and volumes, it is also most useful for analyzing driver mounting/demounting envelopes and tool space, let me know if you have any questions.
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Old 7th July 2017, 03:08 PM   #18
just a guy is offline just a guy  Canada
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Quote:
Originally Posted by Mrscy View Post
Just a guy, what modifications would you advice be done on the ROAR series for flatter response?
Start from scratch. It's a terrible design.
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Old 7th July 2017, 03:13 PM   #19
just a guy is offline just a guy  Canada
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Quote:
Originally Posted by Circlomanen View Post
@Mrscy

Just build it as per the plans. The measured respons is much flatter the the theoretical simulated hornresp respons indicates. Hornresp does not account for frictional losses in the tapped pipe sections.

Cheers
Johannes
Frictional losses in the path have nothing to do with anything. It's been proven over and over that if you accurately sim what you built the sims will match the measurements at small signal levels.

You don't know how this particular sub is going to measure because no one has built it and you didn't bother to simulate it properly. All you can say for sure is that the frequency response is going to be terrible, nothing is going to get rid of that terrible massive dip right outside the passband, which will ensure there's no way to properly cross it over to the mains.

Quote:
Originally Posted by Circlomanen View Post
HiFiForum.nu - ROAR-12 på G

There is some measurements a few posts down in the link above. The dark blue line with the word "Mynning" is a near field measurement of my roar12 with a new B&C 12PS100.
Where's the sim to go along with that? Where's the measurement details? Measured inside or outside? At what distance? How much smoothing in the measurement?

You can't say this new design is going to measure flatter than Hornresp predicts based on a measurement of a completely different design with no sim comparison and no measurement details.

This whole thread is ridiculous.
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Old 8th July 2017, 07:37 AM   #20
Circlomanen is offline Circlomanen  Sweden
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M_tningar-_ROAR12.jpg

The blue line is with the microphone in the mouth of the ROAR12.
The red line is with the microphone at the exit of the tapped pipe section at the bottom of the front-resonator.

We did not think that a very low compression was enough to prolong the working life of the driver. We tried to use an as symmetric loading of the driver as possible in order to avoid warping the cone and the suspensions of the driver at high excursions. The ROAR-series has two quarter-wave resonators tuned to two different frequencies loading the two sides of the cone in an as symmetric way as possible. In a "normal" tapped horn like the THAM-series the driver couples into an expanding unsymmetrical horn throat. This will warp the cone and the suspension when the driver is being pushed hard. With the magnet protruding into the mouth of the horn you get turbulence and a discontinuity of the horn-expansion curve.
Even though driver-failures seems very rare in the THAM-series, we wanted to maximize the working life of the drivers and minimize the risk of driver-failures as much as possible in our new ROAR-series. As linear excursion, Bl and power-handling keeps on increasing in every new generation of drivers we though we needed a new approach to take advantage of these factors.

Based on my first ROAR12, we feel we have achieved our goals. Due to my illness I have not had the health and strength needed to properly test and evaluate it. The posted measurements above is with a raw driver and indoors. I use an Umik and REW.

I hope you build a ROAR18. If you like the THAM-series then I am certain you will like the ROAR-series.

Cheers,
Johannes
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