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Testing the Faital Pro HF200 driver on the Eliptrac400


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I can do impulse but I am confused about it's value.

The Impulse response plot gives a detailed window in time data (at the expense of frequency data viewing) that gives indicaters to ringing, delayed reflections, ..etc.... It's a quick indicator how close to ideal a driver is behaving in the time domain but due to it's high resolution in the time domain frequency data is hidden from view thus the need to also view the Cumulative Spectral Decay plots for viewing amplitude/frequency response versus time for the less than ideal behavior of all drivers/loudspeakers/rooms/..etc....

mike tn

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I can do impulse but I am confused about it's value.

The Impulse response plot gives a detailed window in time data (at the expense of frequency data viewing) that gives indicaters to ringing, delayed reflections, ..etc.... It's a quick indicator how close to ideal a driver is behaving in the time domain but due to it's high resolution in the time domain frequency data is hidden from view thus the need to also view the Cumulative Spectral Decay plots for viewing amplitude/frequency response versus time for the less than ideal behavior of all drivers/loudspeakers/rooms/..etc....

mike tn

Mike,

Something like this that shows how clean the driver/horn combo is, how quickly it can settle, and any resonances would be great.


1210NHTfig7.jpg

Borrowed from © Stereophile - http://www.stereophile.com/content/nht-classic-absolute-tower-loudspeaker-measurements

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Shawn, Rudy,

I just took a closer look at the software you suggested. It looks like it requires a computer with a sound card. My computer has none and there is no spare slot to install one. My old computer did, but it's in the attic! I want to gear everything I do the the HP 3563 analyzer anyhow. It has the impulse generator in it. It has and adjustable window for the time capture feature but I don't think it will look at a narrow enough time interval.

Shawn, I think the SD380 analyzer had this capability as an option. Does the you have / had have it?

Al K.

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Al,

You can get a simple USB soundcard to get audio into your computer.

"It has and adjustable window for the time capture feature but I don't think it will look at a narrow enough time interva"

A waterfall isn't the same as windowing a measurement. Windowing a measurement is basically averaging over the window of time you select. That isn't what a waterfall is about. A waterfall is showing your the response of the system in 3d ( over time), not averaging time and displaying in 2d.

As an example of what you can learn from waterfalls check out this page:

http://homepage.mac.com/marc.heijligers/audio/milestones/acoustical/dampening/dampening.html

Waterfalls can show you problems that are harder to see in 2d. For example I think someone talked about removing ferrofluid in their driver and seeing a little bit better frequency response up high. That is certainly possible but the ferrorfluid also may have been damping the vc/diaphragm and removing it may have added resonance issues. The waterfall would show if that is the case or not.

"Shawn, I think the SD380 analyzer had this capability as an option. Does the you have / had have it?"

I'll have to check, if it does I have never used it on that. I always did waterfalls with ETF.


Shawn

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Al, you do need a sound card that meets certain criteria. I understand wanting to work with just one set of gear. If you ever get bored though, give it a test drive. I use a Tascam external card with my laptop using a USB port. Makes the system totally portable.

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Shawn,

"A waterfall isn't the same as windowing a measurement"

It looks to me that it is. At least one is required to make the other. You are moving a small window in time (a segment or interval of time) and computing the spectrum during that interval. Each segment is converted to a spectrum and displayed one in front of the other which looks like the waterfall.

The "capture pointer" information in the HP 3563 manual is very confusing. I need to look at it again with this idea in mind. I have been using it simply to include everything after the impulse up to but excluding the first reflection to generate anechoic response. I don't think it's adjustable in a way that's going to do this.

The graphic shows a captured impulse off the HP 3563a. The window is between the vertical dotted lines. It's just to wide!

Al K.

post-2934-13819636258336_thumb.jpg

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"It looks to me that it is. At least one is required to make the other.
You are moving a small window in time (a segment or interval of time)
and computing the spectrum during that interval. Each segment is
converted to a spectrum and displayed one in front of the other which
looks like the waterfall. "

OK, from that perspective a waterfall could be considered sort of like a composite of dozens or even hundreds of windowed responses arranged in chronological order. But I think( could be wrong) that the mechanics behind the measurement are a bit more then that. If you measure frequency with a very small time window (one of those composites) you loose low frequency resolution, the waterfall doesn't have that issue.

My main point was just windowing one measurement and looking at it is a 2d display, a waterfall in one graph shows dramatically more information about the behavior of the driver or system or room in the time domain.


Shawn

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OK, from that perspective a waterfall could be considered sort of like a composite of dozens or even hundreds of windowed responses arranged in chronological order. But I think( could be wrong) that the mechanics behind the measurement are a bit more then that. If you measure frequency with a very small time window (one of those composites) you loose low frequency resolution, the waterfall doesn't have that issue.

Shawn the waterfall plots have frequency limitations based on the time window also.

Here is a quick reference about the nature of these measurements. Note: the better programs that display waterfalls eliminate from the display invalid data. I know R+D does anyway.

http://www.libinst.com/wattlar.htm

mike tn

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Mike,

I think you got it! The explanation in the link you gave jives with what my thinking.

I just fiddled with the menus on my HP 3563. There is just no way to narrow that interval window down. All I can do is very the position of the window or delay the impulse in time. It's just not a very good arrangement! Even doing anechoic measurement requires a negative trigger delay to put the impulse into position so that the wide window ending time will be adjustable to before the impulse to some time after it. Unless I'm missing something, it STINKS!

Al K.

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Shawn the waterfall plots have frequency limitations based on the time window also.

Here is a quick reference about the nature of these measurements. Note: the better programs that display waterfalls eliminate from the display invalid data. I know R+D does anyway.

http://www.libinst.com/wattlar.htm

mike tn

Odd that they state that the measurement isn't very valuable, or did I read that web page incorrectly.

It would seem that a driver that can return to rest quickly after the impulse and show minor resonances would be very good in that domain. As the folks at North Creek Music Systems had to say about the G1 Ribbon:

http://www.northcreekmusic.com/Manifest/ManifestInfo.htm

Quote: Above is the Aurum Cantus G1 waterfall plot
over a 4msec window, with a waterfall depth of -30dB. The first 0.5msec
is the actual frequency response during the impulse, and the first
decay slice takes place at 0.6msec. What is of special importance is that the decay is nearly complete by
0.8msec, of an incredible 0.2msec after the impulse is turned off.
Within 1msec, the ribbon diaphragm is completely back to rest. End Quote

Seems speed and low resonance would be a key factor.

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Odd that they state that the measurement isn't very valuable, or did I read that web page incorrectly.

"CSDs often show the user’s technique more than the speaker’s quality! "

"The data shown is VERY SUSCEPTIBLE to measurement and display conditions."

It's not that the data isn't very valuable but more about the fact that if test conditions aren't consistant and good choices about parameters (such as reference drive level and were in the frequency spectrum to match SPL as a reference point for the driver comparisons for example) made during driver comparisons the results can lead to invalid conclusions.

Like Shawn said earlier the main benefit of the CSD Plots is identifying resonant behavior when comparing different drivers but again parameters must be consistant for valid comparisons.

miketn

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  • 3 weeks later...

Interesting discussion on 8 or 16 ohm here. (especially interesting are comments by member sumaudioguy)

http://www.diyaudio.com/forums/multi-way/163536-1-compression-driver-8-ohm-vs-16ohm-2.html

mike tn

After reading as much as I could on the subject of 8 vs. 16 Ohm drivers I have decided on trying the 16 Ohm version. If what I read is correct, on an active setup the 16 Ohm driver should perform better, with less distortion and improve the effective damping factor of my amps. My Hafler amps should have plenty of power to drive the driver directly. I currently have the amp sensitivity set at absolute minimum to keep the P. Audio drivers from drowning out my bass bins.

Just sent in my order and will try to run some sweeps outdoors between the Faital Pro and the P Audio BM-D750 (K69). I currently have the P. Audio CD horn and hope to be able to build a round tractrix horn as well. Of course, who knows how long it will take me to make a round tractrix horn.

When I get an eliptrac for my center channel I will run a comparison of that combination as well.

This speaker upgrade thing just never ends....I guess that's a good thing since I am enjoying the upgrades and the DIY projects as much as the sound.

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