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B&C 21-IPAL Driver and Measurements Discussion


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#21 SME

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Posted 22 June 2016 - 09:38 PM

Interesting.  That almost sounds like a more "honest" rating.  How many amps with 2 ohm / 4 ohm bridged really double the power output versus 4 ohm / 8 ohm bridged?  I wouldn't be surprised if a lot of 2-ohm rated amps are capable of giving just as much or even more power into 2.6 or 2.8 ohms as into 2 ohm.



#22 MemX

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Posted 23 June 2016 - 09:10 AM

If those amp specs are genuine, that's crazy in a 1RU box :blink:



#23 Ricci

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Posted 23 June 2016 - 03:05 PM

Interesting.  That almost sounds like a more "honest" rating.  How many amps with 2 ohm / 4 ohm bridged really double the power output versus 4 ohm / 8 ohm bridged?  I wouldn't be surprised if a lot of 2-ohm rated amps are capable of giving just as much or even more power into 2.6 or 2.8 ohms as into 2 ohm.

 

Or it indicates that the amplifier does not do well at all with impedances lower than 2.6ohm and the output is limited greatly. Nothing wrong with that. None of the modern big burst amps really sustain the types of current needed for continuous output into low impedances. I'd love to see detailed testing on this amp and a bunch of others but nobody seems to be doing it any more.



#24 radulescu_paul_mircea

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Posted 04 July 2016 - 06:09 PM

Hi all,

Trying to develop a very powerful and efficient subwoofer, I noticed something interesting. When comparing the Othorn Ipal with other sub designs like K-Array KS8, KV2 VHD4.21 or martin MLX and ASX, I notice that the bandpass and hybrids works better and more efficient than the Othorn. that seems odd since from what I know, TH are more efficient than Bass reflex and shoud be more efficient than band-pass. but not using the Ipal or M-force drivers. You can see in the pics that when using multiples, the efficiency increases very quick and with 4 large ported BPH  enclosure using 2*21 Ipal the output is huge using less energy than with 8 Othorns.

So whats the catch? Would 2200 sq cm ports avoid compressing at those SPL? 

Attached Thumbnails

  • 4 dual m-force30 Asx Efficiency.JPG
  • Othorn.JPG
  • VHD Vs 2 Othorn.JPG
  • 4 KV2 vs 8 Othorn Ipal Efficiency.JPG
  • 4Dual 21 Martin ASX eff.JPG


#25 radulescu_paul_mircea

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Posted 04 July 2016 - 06:53 PM

Ricci,if you still have those bass reflex enclosures made for the 21sw152, you could put the Ipal driver inside to see when and how much those ports would compress and how different those drivers behave.
Also, regarding the low impedance stability of the K20, on some of the Powersoft datasheets and white papers they say the M-Force driver can work also with K10 or K20. But that one has a RE of less than 0.26 ohms.

#26 Ricci

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Posted 05 July 2016 - 05:20 PM

Hey Paul it is impossible to tell much of anything from your graphs without the inputs used. We would have no idea the comparative sizes used, tunings, what loading, etc...One very easy way to increase efficiency is tune higher and/or allow a bigger airspace. It makes a HUGE difference that cannot be understated. Also I would never compare multiple cabs versus multiple cabs. I know that HR has the tools for it but I just don't quite trust it because I've never seen sufficiently detailed measurements of adding additional cabs of the various types of alignments. Just my personal preferences but I always use either half or full space loading and compare the minimum amount of cabs. If it would be 4 of one versus 8 of another I'd reduce it to 1 vs 2.

 

I'm not remembering the datasheets where they suggest the M-force be used with the K10 or K20? They may say that but here's the thing. The IPAL and M-Force systems are designed for maximum efficiency/higher order loadings (BP, TH, FLH or vented at minimum) and are made for relatively narrow band response. The drivers are so efficient that the average impedance is much higher than "normal" or what the Re would suggest. Once they are loaded in a band pass or horn there are multiple peaks of impedance in the bandwidth and then the intended bandwidth is restricted to something like 30-90Hz. This keeps the actual impedance seen by the amps much higher than you would think. something like a full bandwidth sealed or IB system would cause serious limitations. The amps will not like that I assure you. It's heavily APP dependent. I certainly haven't seen optimal performance from the PS digam series into impedances that low.



#27 radulescu_paul_mircea

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Posted 05 July 2016 - 10:22 PM

Thank you for your response. I don't have access now to my PC, but the VHD 221 is measured by me when I opened two for changing drivers and glueing some wood and the simulation is made exactly from those dimensions comparing it with 2 Othorn both using the Ipal driver. The other design is a simple ported band pass horn at under 1000 litters. The tunings are all at 30 hz or so. The K-Array KS 8 is the same as VHD 221 but a bit smaller.I am sure that the ports will compress, and the K-array will be worse but could it be there a mechanisms trough which this compression can be compensated?
After seeing those efficiencies, I was stunned but after that My thought was that there should be a catch somewhere and it probably is the way HR is simulating multiples.

#28 Ricci

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Posted 06 July 2016 - 03:50 PM

If you feel like posting the HR inputs I could take a look. You said that one system is close to 1000L? Othorn is about 420L so the bigger cab likely would be much more efficient.



#29 radulescu_paul_mircea

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Posted 06 July 2016 - 10:01 PM

The file where I saw you could use the M-force driven by K10 and K20 is in this link

http://www.powersoft...-kit-guide/file

 

Also in the next link, at Super Bowl they said they used an M-drive driven by a single K10 (although I suspect it wasn't really used at a very high power)

http://www.fohonline...subwoofers.html



#30 radulescu_paul_mircea

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Posted 06 July 2016 - 10:43 PM

The VHD sub is measured as you can see in REW and the simulated response usinng basic band pass crossover looks almost Identical. The sub was measured outside on a beach close rangeand also at 10 meters with no object around closer than 20 meters. the graph is close mic.

When I was comparing the efficiency and output of the KV2 vs Othorn i was comparing 1 VHD 2.21 IPal vs 2 Othorn Ipal.

The other sims are fictive, based on what I think the Martin Asx looks like inside, but larger with 2 drivers inside. first would be with Ipal and second with M-force.

My main question is if the Ipal technology has a way of compensating for the port compression at very high output.

From what I know, a Helmolz resonator works well when alt the air mass from the port is resonating. when turbulences occur the efficiency drops and after a certain air speed the sistem tends to be nonliniar and the speaker starts to behave almost like in a leaky sealed enclosure with a higher tune and a good cooling system, but that port will not really help the driver to get more sound . That is why I always thought FLH and TH are more suited for extreme SPL than Bass reflex or Band pass. But then I thought that this tech from Powersoft could have some methods trough which they can overcome this problems or compensate for them in a way.

Attached Thumbnails

  • KV2 VHD2.21.jpg
  • VHD2.21 screws and glue.jpg
  • ASX dual ipal input.png
  • ASX M-force.png
  • KV2 VHD2.21 input ipal.png
  • KV2 VHD2.21 input.png
  • 2.21 Paul small.png


#31 SME

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Posted 07 July 2016 - 06:40 AM

I can't speak for Powersoft's technology directly, but I can reason a bit from theory.

 

It may be possible to wring a few dB more compression-free output from an overloaded vent using some kind of DSP, but I wouldn't expect any big gain.  Furthermore, this assumes that you have extra power to give to the driver because no DSP can correct the loss in efficiency due to port compression at higher playback levels.  So I'd argue that such capability would be only marginally useful anyway.



#32 Ricci

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Posted 07 July 2016 - 07:27 PM

Hey Paul,

 

Vents will compress but so do horns believe it or not. Pressures and air speeds get very high inside horns as well. The vent sizes that you have are gigantic and larger than many horn segments near the throat, so they should be quite capable of supporting high airspeeds. The DPC circuit may try to combat vent non-linearity but I'm not sure how effective that would be at the extremes when the vent is heavily compressed.

 

Looked at your HR sims. Yes those cabs do have a very high efficiency. Higher than the Othorn for sure. They are around twice the size though and the corner is a little higher on them. I've attached the HR inputs for a dual Othorn cab with the 21 Ipal drivers for your comparison. I designed the Othorn quite a few years ago now. One thing you have to remember is that it had to be exactly 36x36x24 due to restrictions I had on size, prior to any design work, while also having high output all of the way down to 25Hz. It isn't the loudest cab on the block. The real trick was the package of extension, size, clean sound and output. IMHO of course.

 

I will send you a pm shortly to discuss a few things.

 

DUAL OTHORN CAB.png


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#33 radulescu_paul_mircea

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Posted 07 July 2016 - 09:40 PM

That package is quite good, and possibly even better with the Ipal driver module combo. Also a design a bit larger with a bit lower extension could be a game changer for me.
Yes , those ports are huge , as are also those in VHD sub, but even with those sizes I measured about 2-3 dB compression at vent running. But for a fact I know that a part of that is because of the power amp because although I had 2 K8, an X8 and a K20 with me that I installed on another location afterwards, I only used the VHD 3200 because of the special connections and I didn't have the time to change them.

#34 manninen

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Posted 08 July 2016 - 06:26 AM

Martin audio MLX says its 8ohm driver

 

"DLS18002 18" Driver 8 ohm MLX £1,083.00"

 

https://martin-audio...ets/MLXspec.pdf

 

8ohm B&C ipal 18"?



#35 Ricci

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Posted 08 July 2016 - 03:21 PM

That package is quite good, and possibly even better with the Ipal driver module combo. Also a design a bit larger with a bit lower extension could be a game changer for me.
Yes , those ports are huge , as are also those in VHD sub, but even with those sizes I measured about 2-3 dB compression at vent running. But for a fact I know that a part of that is because of the power amp because although I had 2 K8, an X8 and a K20 with me that I installed on another location afterwards, I only used the VHD 3200 because of the special connections and I didn't have the time to change them.

 

Checked out the Kv2 website. Looks like a well established company with a full lineup of products. Can't believe I'm just now hearing about them. Amplifiers seem to be big,heavy and slightly underpowered. I am a little suspect of some of their claims in their technology segments. There are a lot of claims but very little measurements, explanation of the conditions,  or data to back any of it up. I'm sure they make good products but the claims of "pulse" response and the like being so much better than other products is not passing the initial sniff test.

 

Minor rant here...

Actually this is a trend I've been noticing with the pro companies in the last few years. It seems that less concrete data is being offered for their speakers. It is becoming rare to see an impedance, or response measurement for a cabinet anymore. Now it is mostly a basic FR spec of +/-3dB and +/10dB, a max peak output, usually calculated and often with no qualification of what frequency it occurs at. Same thing for sensitivity. Sensitivity sometimes gets fudged by putting 2.83v into a 2ohm minimum impedance and then quoted at the single peak frequency. The FR flatness claims often involve either DSP for active systems and/or significant smoothing of the measurement, which is then not shown in any case.

 

Martin audio MLX says its 8ohm driver

 

"DLS18002 18" Driver 8 ohm MLX £1,083.00"

 

https://martin-audio...ets/MLXspec.pdf

 

8ohm B&C ipal 18"?

 

Hmmm. I don't see that anywhere in the literature. Is that from the replacement parts list? Would be odd for them to use 8ohm drivers when the IPAL module is being used and it is designed to work with a pair of the 18's wired parallel at 1 ohm. Martin is a big enough company to have it done if they want though. Could be??? Interesting sub. Looks like a number of people seem to have hit upon the same idea for bass cabs around the same time.



#36 radulescu_paul_mircea

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Posted 08 July 2016 - 07:53 PM

The KV2 specs for the sub's continuous output when two are used is spot on! 141 dB from a pair and 147 from the Ipal version with 34 Hertz extension is the most sincere spec I'be seen for a while :)) that's if you don't read the rest :))
The Martin ASX user manual is more than interesting. it said about the driver being capable of a 30 mm one way stroke and 152 dB SPL, even saying to limit the peak output if one cannot keep the minimum distance at 4 meters.
We, DIY-ers have some things to compete with now, not only bass reflex subs ;)

#37 SME

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Posted 09 July 2016 - 06:02 AM

Interesting.  IIRC, OSHA limits exposure to peak level of transient/impact noise to 140 dB (C-weighted, I think).



#38 radulescu_paul_mircea

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Posted 09 July 2016 - 03:22 PM

Martin audio MLX says its 8ohm driver

"DLS18002 18" Driver 8 ohm MLX £1,083.00"

https://martin-audio...ets/MLXspec.pdf

8ohm B&C ipal 18"?

If you look into Ipal AES convention paper, you can see that it "can be matched to any high performance low frequency high excursion transducer, even though it's performance can be maximized if used in conjunction with some specific transducer" and I believe being a matter of cost and profit, it isn't always the best choice to make the best one can do, because for 3 dB extra, it is better for them if you buy an extra box than to spend more to use the best driver. ;)
I never opened a MLX sub so I cannot know, but they definitely use the Ipal module controlled by their own software

#39 radulescu_paul_mircea

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Posted 09 July 2016 - 03:35 PM

The thing in the Ipal system that is most important and interesting is the fact that as far as the designer is concerned, there is an electric input and an acoustic output, size and weight constraints and maximum Spl/cost. Using that DPC allows one to choose a desired transfer function and no matter of the inherent nonliniarities of the drivers, that BI is overwhelming them so it is easy to modify the system to match the target response.
Even though this 21Ipal driver is formidable on it's own, I really love what it can do in a complete system, in the pro audio domain. Taking into account only the fact that the effects of aging are largely diminished, can expand the life of one's investment and that is a serious advantage.

#40 Ricci

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Posted 09 July 2016 - 04:21 PM

IPAL system is powerful but it still has the limitations of any other setup. The amplifier voltage and current limits, the driver excursion limits and thermal handling etc. The driver simulation circuit can only work up to the point that some limitation is met. In that way you want the highest power handling most efficient driver possible. True efficiency of the system cannot be changed. In that way the driver modeling is interesting to me but I would concentrate more on using a very high performance driver and match the cab to the driver as much as possible so as to use very limited signal shaping. To me the DPC feedback system is the real item of note with the system.
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