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"near field vs far field presents a completely different frequency response to the ears/senses."


that is the understanding many folks have. however, it is inconsistent with what folks experience. nearfield bass (less than 1 meter) is more tactile than farfield bass even though the reflections from room gain dramatically increase the measured spl in the farfield.


to properly measure the nearfield experience (at less than 1 meter), it may be necessary to move toward a more complete measurement system that considers sound "intensity" as somebody already mentioned, but I'm not even sure if *that* goes far enough.


we don't have enough data to know and the science isn't even very well understood. the paper that i linked to is a 2014 publication citing 28 other studies on the matter (sound behavior in the nearfield) and there is no consensus on what is going on in the region of space very close to the source.
This topic seems to be popping up a lot recently... :)

I'm surprised it doesn't come up more frequently, as doing it correctly, really adds another level to the ULF experience. If PVL (Particle Velocity Level) varies with different designs and drivers (which I believe it does), it's brings a whole new dimension to subwoofers that has not really been explored.

What sort of measurement system includes intensity? And how much is one?
Sound Intensity Meter - Microflown

Great link LTD02.

My initial tl;dr takeaway as it applies to the topic at hand is that, a good portion of the nearfield sound intensity ("reactive intensity") is a vector quantity where pressure and velocity are 90 degrees out of phase and so, while being very much real and contributing to the user's experience, it doesn't radiate out into the room and doesn't sum with the scalar quantity know as "active intensity" in a straightforward way, so SPL measurements don't show it. Sound about right?

Also here's a link with purty animated pictures that show some of this stuff, still trying to wrap my brain around it all: http://www.acs.psu.edu/drussell/Demos/Burns_PhD_animations/Burns_PhD_anim.html
Yup, sounds right. PVL is the game changer in the nearfield. I indirectly measured Sound Intensity here using an accelerometer.

Like LTD, one of my sources was that B&K doc. I also have several other sources listed in that post. :cool:
 

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I will dispel a few assumptions on your part. One is we hit that driver with more than just the few samples that Shreds posted. We ran some sine sweeps/tones through it free-air as well as in the box. I have actually done this with the 24 on multiple occasions. TBH I don't remember if that was when we had it on a single channel of the Peavey or after we wired the coils separate, but I think we did at least a little testing after the re-wire. previously, the sub was only getting around 3600 watts :rolleyes:

When it comes to my electrical situation, I am in an area that has never experienced a "Brown-out" nor high demand issues that you would assume in more populous places. Matter of fact, as the electrical company was working on some lines this past summer, I was querying him about several aspects of the the particular line I was on and the type of demand I personally put on my system, coupled with any possible situation that could arise in my area. He assured me the capacity was ample, had been ample, and that they had never come CLOSE to seeing any issues that you might have thought could play a part in brownouts or undervoltage situations...

All things considered, 8000 watts can kill this driver. 4000 watts CAN kill this driver, but in real world situations, at the levels that most would be playing, to the levels that some that like to push the envelope would like to play it, the hs24 did admirably well. Whether it was the impedance load on the amp, or whatever else electrical MIGHT(however unlikely) have put the amps into protection, the driver excelled. Let's just say, it survived a test where it was overpowered, grossly boosted over standard reference levels, and played through above standard HT and music material that most would consider high peak output requirements.

It's all good, I am going to have another pair of 24's to have fun with. Using some very powerful amps. And my objective is to kill them. Both of them...To find their limit. WITH NORMAL MATERIAL.
I'm not assuming anything, just pointing out there are other factors (including factors outside your house) that can cause an amp to go into protection. Regardless of what the electrical company man said, line voltage is not constant anywhere, it fluctuates throughout the day in both voltage and frequency.

I have no doubt the driver performed admirably at the GTG but I'm more interested in what caused the amp to turn off and how much power the driver was actually consuming. And I'm even more interested in real data like power compression and distortion. A simple story about how you were unable to destroy the driver because the amp stopped isn't data and isn't useful.

This driver is probably more similar (for thermal considerations) to the Sundown ZV3 than different, and as data-bass shows the ZV3 can take a ton of power (at least for a 24 second frequency sweep). But data-bass also shows that there's a point of diminishing returns where adding more power doesn't make much sense because the thermal considerations like power compression outweigh the gains.

For that reason I'd rather see data than stories about trying to blow up drivers. These attempts make good stories but reveal no actual useful data at all. N8DOGG melted a couple of SI 18s with a couple of 500 watt amps with what you would call "normal material". So the moral is that if you aren't able to blow the driver up you just weren't trying hard enough.

Do some tests that include ACTUAL measured voltage from the amp, power compression testing and distortion testing at varying levels, preferably outdoors like data-bass does. That would provide some actual useful data and you don't have to blow up drivers.
 

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Discussion Starter #724
I'm not assuming anything, just pointing out there are other factors (including factors outside your house) that can cause an amp to go into protection. Regardless of what the electrical company man said, line voltage is not constant anywhere, it fluctuates throughout the day in both voltage and frequency.

I have no doubt the driver performed admirably at the GTG but I'm more interested in what caused the amp to turn off and how much power the driver was actually consuming. And I'm even more interested in real data like power compression and distortion. A simple story about how you were unable to destroy the driver because the amp stopped isn't data and isn't useful.

This driver is probably more similar (for thermal considerations) to the Sundown ZV3 than different, and as data-bass shows the ZV3 can take a ton of power (at least for a 24 second frequency sweep). But data-bass also shows that there's a point of diminishing returns where adding more power doesn't make much sense because the thermal considerations like power compression outweigh the gains.

For that reason I'd rather see data than stories about trying to blow up drivers. These attempts make good stories but reveal no actual useful data at all. N8DOGG melted a couple of SI 18s with a couple of 500 watt amps with what you would call "normal material". So the moral is that if you aren't able to blow the driver up you just weren't trying hard enough.

Do some tests that include ACTUAL measured voltage from the amp, power compression testing and distortion testing at varying levels, preferably outdoors like data-bass does. That would provide some actual useful data and you don't have to blow up drivers.
I'm under the impression that @Ricci has a SI 24" and recently got his hands on @beastaudio 's old box. I think I recall mention that Josh was going to beef up the box a bit and he should be ready to test when it warms up... Need confirmation on all that, because I can't find the original post at this moment...

Regardless, we should have all the cards out on the table in then near future.
 

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I'm under the impression that @Ricci has a SI 24" and recently got his hands on @beastaudio 's old box. I think I recall mention that Josh was going to beef up the box a bit and he should be ready to test when it warms up... Need confirmation on all that, because I can't find the original post at this moment...

Regardless, we should have all the cards out on the table in then near future.
Sure, I saw the same thing, and that is good news. I'm just suggesting that the "try really really hard to blow up the driver with an unmeasured power level and random program material" test is basically useless as data. It's great for generating hype but it's useless for anything else. I'm suggesting there are tests that could be done that would provide useful data for everyone.

For example, how about distortion measurements at increasing levels of measured voltage? Data-bass isn't going to do that, and it would give some indication of usable excursion.

How about testing the driver power handling the same way the pro industry does? Apply an AES signal for several hours, check power compression levels after 2 hours and again after 10 hours. Repeat the test with higher voltage, and keep repeating until it's clear the driver can't take anymore (too much power compression). Then you would have a REAL power handling figure that no one could argue with instead of the current method which from forum posts by Electrodynamic (and N8DOGG's experience) reads like "1500 watts RMS is the power handling. I won't tell you how we came up with that number or what it's based on but it's very conservative. (This is strongly hinting that it can handle a lot more than rated, even if you can destroy the driver with an amp smaller than 1500 watts.) But I won't honor the warranty if you melt the voice coil."

How about doing the same testing as data-bass is going to do, but with different box sizes, which will provide dramatically different results?

How about doing anything with actual measurements? Any data is better than no data, and Beast's proposed testing will provide no useful data of any kind.
 

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Sure, I saw the same thing, and that is good news. I'm just suggesting that the "try really really hard to blow up the driver with an unmeasured power level and random program material" test is basically useless as data. It's great for generating hype but it's useless for anything else. I'm suggesting there are tests that could be done that would provide useful data for everyone.

For example, how about distortion measurements at increasing levels of measured voltage? Data-bass isn't going to do that, and it would give some indication of usable excursion.

How about testing the driver power handling the same way the pro industry does? Apply an AES signal for several hours, check power compression levels after 2 hours and again after 10 hours. Repeat the test with higher voltage, and keep repeating until it's clear the driver can't take anymore (too much power compression). Then you would have a REAL power handling figure that no one could argue with instead of the current method which from forum posts by Electrodynamic (and N8DOGG's experience) reads like "1500 watts RMS is the power handling. I won't tell you how we came up with that number or what it's based on but it's very conservative. (This is strongly hinting that it can handle a lot more than rated, even if you can destroy the driver with an amp smaller than 1500 watts.) But I won't honor the warranty if you melt the voice coil."

How about doing the same testing as data-bass is going to do, but with different box sizes, which will provide dramatically different results?

How about doing anything with actual measurements? Any data is better than no data, and Beast's proposed testing will provide no useful data of any kind.
You have provided so many intelligent counter points to SI's propaganda. I have thoroughly enjoyed reading everything you have been writing. Just wanted to say Thank You.
 

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You have provided so many intelligent counter points to SI's propaganda. I have thoroughly enjoyed reading everything you have been writing. Just wanted to say Thank You.
Clearly it's a mixed bag. I've received equal amounts of support and hate mail.

More - Thanks.

Fat - I didn't bring this up, IIRC Mark Seaton brought it up in post 611. Since then dgage, LTD02, Electrodynamic, Shreds, Beast and myself have all commented on the power issue, and a few others commented on those comments. But I'm guessing it's me that you have an issue with since you unsub'ed directly after my post.

I made maybe 5 posts about inductance and about 5 posts about power handling in this thread. I don't think that's out of line on the AV SCIENCE forum. I don't think it's out of line to talk about questionable specs or request data instead of hype.

I've only commented on the SI 24 in 3 threads on this forum, and I NEVER brought it up, I only responded to other people that brought it up. I didn't intend to discuss the driver itself (other than inductance issues causing simulation problems) in this thread, but several people brought it up and so I commented as well.

I would urge you to resub and just put me on your ignore list. That should take care of your issue and allow you to follow the thread.

Popalock, if you would like to to leave your thread I will, it's not my intention to cause people to unsubscribe from your thread. I don't plan on commenting on the driver itself any more in this thread, but if other people continue to bring it up I might, unless you want me to go.
 

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"one of my sources was that B&K doc. I also have several other sources listed in that post."


missed that. my bad. :eek:


I'm not sure if it was that doc or another, but there was something about the distance between the mic capsules being necessarily larger for measuring intensity at low frequencies. not sure if the microflown linked to has sufficiently low frequency measurement potential, but I really haven't dug into it.


---
 

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All of this talk is great, but I think one of you guys should ship me a free SI-24 to torture with my iTech-8000 (which is on a 40amp breaker fed by triple 2awg wire on a 200amp breaker, fed by a 400amp breaker, fed by 3 medium-sized 10kV transformers.)
I highly doubt the amp or breaker or poco will give out before the driver does. But if it does, there is always a bridged clone in 14000watts-mode to try (hehe!)



I'll even put a voltmeter on the speaker wire and measure the db's and harmonic distortion with some sinewaves; and then afterwhich, give it the same "Carbon Prevails" and death-trance music signals that my SDX-15's smoked with.

I think that would be great fun if you ask me. :p
 

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Discussion Starter #733
Clearly it's a mixed bag. I've received equal amounts of support and hate mail.

More - Thanks.

Fat - I didn't bring this up, IIRC Mark Seaton brought it up in post 611. Since then dgage, LTD02, Electrodynamic, Shreds, Beast and myself have all commented on the power issue, and a few others commented on those comments. But I'm guessing it's me that you have an issue with since you unsub'ed directly after my post.

I made maybe 5 posts about inductance and about 5 posts about power handling in this thread. I don't think that's out of line on the AV SCIENCE forum. I don't think it's out of line to talk about questionable specs or request data instead of hype.

I've only commented on the SI 24 in 3 threads on this forum, and I NEVER brought it up, I only responded to other people that brought it up. I didn't intend to discuss the driver itself (other than inductance issues causing simulation problems) in this thread, but several people brought it up and so I commented as well.

I would urge you to resub and just put me on your ignore list. That should take care of your issue and allow you to follow the thread.

Popalock, if you would like to to leave your thread I will, it's not my intention to cause people to unsubscribe from your thread. I don't plan on commenting on the driver itself any more in this thread, but if other people continue to bring it up I might, unless you want me to go.
I don't get the sense that you are trolling. Every response I have seen from you seems objective and fact based. I think we all get that there are still questions that need to be answered and you clearly have a substantial knowledge base to ask the questions that many other haven't really thought about. I've learned a lot from the back and forth over the past few weeks. This isn't the first time this has happened...I've had people unsubscribe in the past when things got really technical (@bossobass & @FOH talking PVL...lol).

It is what it is, I'm a huge fan of the S in AVS.

You have provided so many intelligent counter points to SI's propaganda. I have thoroughly enjoyed reading everything you have been writing. Just wanted to say Thank You.
Motha F^&*in Google said:
prop·a·gan·da
/ˌpräpəˈɡandə/

information, especially of a biased or misleading nature, used to promote or publicize a particular political cause or point of view.
:rolleyes:^...Meh, now that seems a bit on the trollish side... I guess we can call a spade a spade, but it seems to me like you are relying on DIY Sound Guy as a crutch to support whatever beef you may personally have against SI... Like SI is continually spreading lies and trying to be deceitful... It's been mentioned before, SI provides more information that a lot of other manufactures. I would imagine that maybe only a handful of manufacturers in the world have all of the information that DIY Sound Guy is asking for readily available...

JBL Pro... and who else?
 

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I'm not going to unsubscribe, but between this and the "AE may be cooking up a 24" thread, I've lost a lot of interest. I come to check out this @popalock thread several times a day for cool updates, some impressions, some laughs, some further build details and maybe some room measurements. I am all for having scientific discussions on this forum, I think it just needs to be thread appropriate. Many would argue that this thread is where it's appropriate. I disagree. The exact same thing happened to the AE thread where just about as soon as N8DOGG posted the thread, it mostly all became a rant about SI's 24" and false claims.

I personally would love to own an SI 24". Before I bought 2 more HT18"s last year, my wife and I talked about the possibility of buying a 24" instead since they were still at their pre-order price. In the end, space constraints won out. If the chance comes up again at some point and the price is right (not $1600) and I had the space, I would definitely scoop one (or two) up.
As for the AE driver, all AE drivers are out of my price range, so I'll pass. I know they make incredible stuff, because of posted measurements and subjective impressions (and people wanting to justify the money they spent on them) but all the talk about inductance control and Re in a huge 24" subwoofer makes almost no sense to me. It's all great to talk about but when it comes time crank that thing up, subjective opinion is what wins out. When I invite over my friends for a demo, nobody could give a F#$% about inductance control or what the Klippel measurements may or may not show for my (lowly) HT18's. In fact, none of them would know what the hell I'm talking about anyway. Instead, the reaction is "HOLY $HIT!, THIS IS AWESOME!". And I agree with them.

Maybe @diy speaker guy could start a kind of "Mythbusters" thread of his own where he can scientifically debunk all of the false claims that speaker companies make. I think that would be an added value to the community, and I know I would subscribe to it. As for clogging up Popa's build thread and an AE thread, I've just had enough. My $0.02.
@popalock I can't wait to see what you cook up next! Keep smilin....keep shinin.... :D
 

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For example, how about distortion measurements at increasing levels of measured voltage? Data-bass isn't going to do that, and it would give some indication of usable excursion.

How about doing the same testing as data-bass is going to do, but with different box sizes, which will provide dramatically different results?
???
I've been measuring distortion at various drive levels since nearly the beginning. Voltages are now listed for anything in the past few years as well.

Multiple box testing is nice but not really required for every driver. What is better is a baseline with a good driver in 3 or 4 different alignments. The way that driver reacts to each will provide a guideline for how any driver would react in a broad sense. The drivers being tested in one standard enclosure give plenty of data on each driver relative to the others.
 

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@diy speaker guy

If I read the word inductance one more time...

Good gravy man...yes, it's good information, but you have to cut back a little bit. Who cares who brought it up, that doesn't mean you need to reply every single time...
 

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???
I've been measuring distortion at various drive levels since nearly the beginning. Voltages are now listed for anything in the past few years as well.
Yes, not sure how I forgot about that, sorry. It was late when I posted that.

Multiple box testing is nice but not really required for every driver. What is better is a baseline with a good driver in 3 or 4 different alignments. The way that driver reacts to each will provide a guideline for how any driver would react in a broad sense. The drivers being tested in one standard enclosure give plenty of data on each driver relative to the others.
Agreed, but most people won't pick up on the differences due to the fact that some drivers are tested in 4.2 cubic foot (or whatever size your standard test box is) boxes and this driver will be tested in a 15 cubic foot box. It makes a big difference.
 

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I'm not going to unsubscribe, but between this and the "AE may be cooking up a 24" thread, I've lost a lot of interest. I come to check out this @popalock thread several times a day for cool updates, some impressions, some laughs, some further build details and maybe some room measurements. I am all for having scientific discussions on this forum, I think it just needs to be thread appropriate. Many would argue that this thread is where it's appropriate. I disagree. The exact same thing happened to the AE thread where just about as soon as N8DOGG posted the thread, it mostly all became a rant about SI's 24" and false claims.

I personally would love to own an SI 24". Before I bought 2 more HT18"s last year, my wife and I talked about the possibility of buying a 24" instead since they were still at their pre-order price. In the end, space constraints won out. If the chance comes up again at some point and the price is right (not $1600) and I had the space, I would definitely scoop one (or two) up.
As for the AE driver, all AE drivers are out of my price range, so I'll pass. I know they make incredible stuff, because of posted measurements and subjective impressions (and people wanting to justify the money they spent on them) but all the talk about inductance control and Re in a huge 24" subwoofer makes almost no sense to me. It's all great to talk about but when it comes time crank that thing up, subjective opinion is what wins out. When I invite over my friends for a demo, nobody could give a F#$% about inductance control or what the Klippel measurements may or may not show for my (lowly) HT18's. In fact, none of them would know what the hell I'm talking about anyway. Instead, the reaction is "HOLY $HIT!, THIS IS AWESOME!". And I agree with them.

Maybe @diy speaker guy could start a kind of "Mythbusters" thread of his own where he can scientifically debunk all of the false claims that speaker companies make. I think that would be an added value to the community, and I know I would subscribe to it. As for clogging up Popa's build thread and an AE thread, I've just had enough. My $0.02.

@popalock I can't wait to see what you cook up next! Keep smilin....keep shinin.... :D
Agreed about the thread appropriate factor, but remember I didn't bring this up in EITHER of the recent threads.

Subjective impressions are nice and all but they aren't that useful as data, and in a lot cases the GTG impressions are being presented as data.

There's literally hundreds of pages of subjective opinion on this driver. I'm sorry my 40 or 50 total technical posts about this driver in both recent threads combined were so offensive to you. I realize this forum's culture usually gives a lot more likes to meme pics and OT one line posts than long technical posts but there is a place for technical discussion too.

@diy speaker guy

If I read the word inductance one more time...

Good gravy man...yes, it's good information, but you have to cut back a little bit. Who cares who brought it up, that doesn't mean you need to reply every single time...
How is that fair? I'm not allowed to reply in a discussion? Only one side is allowed to present their point of view? I didn't bring it up and I wasn't talking to myself, there are at least two people involved in a conversation.

Inductance is a big issue in high excursion drivers that isn't talked about much. This is exactly why TC and AE drivers are so expensive. People show sims all the time that don't include inductance effects and no one says anything. People say the UXL will have 95 percent of the performance of the TC driver in the Gjallerhorn but no one mentions that the frequency response will be different due to the inductance. And while it's not talked about a lot, some people other than me do talk about it.



FWIW, points taken. Too much technical discussion is not appreciated in threads that are not strictly technical discussions. If other people didn't bring it up first I never would have commented. If other people do not bring it up in the future I won't continue to comment. At this point there isn't a lot left to say anyway.
 
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