HT3 Measurements

DMurphy · « **on:** 11 Feb 2007, 02:51 pm »

I promised to post some plots of the HT3 awhile back, but I kind of forgot. I have them now, but I can't figure out out to insert images. The help menu wasn't much help. Can someone give be a crash course? Thanks.

zybar · « **Reply #1 on:** 11 Feb 2007, 02:53 pm »

Quote from: DMurphy on 11 Feb 2007, 02:51 pm

I promised to post some plots of the HT3 awhile back, but I kind of forgot. I have them now, but I can't figure out out to insert images. The help menu wasn't much help. Can someone give be a crash course? Thanks.

Just sent you a PM.

George

jsalk · « **Reply #2 on:** 11 Feb 2007, 03:17 pm »

Dennis -

Perhaps this would help. I think these are the plots you wanted to post:

HT3 on axis...

And 50-degrees off axis...

Perhaps you'd like to comment on the latter.

- Jim

DMurphy · « **Reply #3 on:** 11 Feb 2007, 03:24 pm »

Thanks Jim Here is the text I intended to include:

Here are 2 plots of the HT3 I have in my work room. If they don't post in the right order, hopefully you can figure them out. One is the standard one-meter on-axis plot, with no smoothing. It bears a strong family resemblance to the V3 plot that Jim posted in that thread. The second shows the response when the mic is moved about 50 degrees off-axis to the right (or left--same result). This is a much more rigorous test of a speaker's performance. It's very difficult to avoid funny dips and peaks due to differences in the dispersion patterns of the drivers, and diffraction effects from the cabinet edges. But if the drivers, crossover points, and cabinet baffle edge treatment have been chosen correctly, you should see a fairly smooth response with the highs trailing off due to inevitable beaming from the tweeter. In this case, the response is still reasonably flat to 10 kHz. The 50 degrees angle is extreme--usually you see plots at 15 and 30 degrees. The fact that things still look respectable way off axis indicates that the G2 ribbon has very smooth, extended dispersion, and that there should be no imaging problems from the stereo pairs.

Toka · « **Reply #4 on:** 12 Feb 2007, 03:50 pm »

Thank guys!

Toka · « **Reply #5 on:** 19 Feb 2007, 08:42 pm »

Oh yea, forgot to ask...Dennis, do you HT3's have the front baffle? Either way, would it make much of a difference?

DMurphy · « **Reply #6 on:** 19 Feb 2007, 10:46 pm »

Mine doesn't have the baffle. But at the wave lengths that are involved, it wouldn't make any difference. I personally prefer the look without the extra baffle, but there's no sonic issue involved.

JoshK · « **Reply #7 on:** 19 Feb 2007, 11:07 pm »

I'd hope that isn't a calibrated plot...else that sensitivity is damn low.

DMurphy · « **Reply #8 on:** 20 Feb 2007, 12:00 am »

Quote from: JoshK on 19 Feb 2007, 11:07 pm

I'd hope that isn't a calibrated plot...else that sensitivity is damn low.

Naaaaaa I just cranked up the amp and shot a plot. There's no correction for drive level or measuring distance. The actual sensitivity is about 15 dB above that.

Kevin Haskins · « **Reply #9 on:** 20 Feb 2007, 12:03 am »

I do the same thing but I push my plots up in reference so I don't take any heat from casual observers.

Looks great by the way. The ribbon really has nice horizontal dispersion.

DMurphy · « **Reply #10 on:** 20 Feb 2007, 02:58 am »

Thanks for the suggestion. I've never paid any attention to the Y-axis markings, but I can see how others would.

BrunoB · « **Reply #11 on:** 20 Feb 2007, 12:20 pm »

Quote from: DMurphy on 11 Feb 2007, 02:51 pm

I promised to post some plots of the HT3 awhile back, but I kind of forgot. I have them now, but I can't figure out out to insert images. The help menu wasn't much help. Can someone give be a crash course? Thanks.

Would it be possible to see impulse, phase and waterfall plots?

Thanks

DMurphy · « **Reply #12 on:** 20 Feb 2007, 04:40 pm »

clean waterfall plots are hard to get for a 3-way--at least I haven't had much luck using Praxis. There aren't any resonances in the drivers aside from the 5kHz break-up of the midrange, which is well suppressed. I can show you the reverse nulls, which will reveal the degree of phase tracking across the crossover regions. I guess I can show you the impulse, although it will just verify that this is not a transient perfect design. No 1st order acoustic slopes with time aligned drivers.

woody · « **Reply #13 on:** 1 Mar 2007, 07:15 pm »

Hi Jim & Dennis,

Thanks for the plots! Very good info to back up what all of us HT3 owners have been hearing.
Is it possible to post a plot of the complete freq response -- 20Hz to 20kHz?

Thanks for such a great product!

jsalk · « **Reply #14 on:** 1 Mar 2007, 09:42 pm »

woody -

Quote from: woody on 1 Mar 2007, 07:15 pm

Hi Jim & Dennis,

Thanks for the plots! Very good info to back up what all of us HT3 owners have been hearing.
Is it possible to post a plot of the complete freq response -- 20Hz to 20kHz?

Thanks for such a great product!

It would certainly be possible to generate such a plot. But it requires a full-blown anechoic chamber (which neither of us has). Without the chamber, you are measuring floor bounce and room modes in addition to the speaker. It wouldn't be pretty.

There is no problem generating a plot above, say, 200Hz. But below that, without a chamber, a simulation is the best we can do.

We can certainly post a computer-generated simulation of the response.

- Jim

DMurphy · « **Reply #15 on:** 1 Mar 2007, 11:53 pm »

[Is it possible to post a plot of the complete freq response -- 20Hz to 20kHz?

Praxis, my measurement software, allows me to capture a plot from 20 Hz to 20kHz. Praxis gives you the anechoic response, free of room reflections, down to 200 Hz, and then it shifts over to a longer sampling period and gives you the 1/12th octave smoothed response below 200 Hz. But as Jim says, it ain't pretty. There's the big dip around 120 Hz from ceiling-floor bounce, and then peaks and dips from room standing waves. I cut the HT3 measurement off at 200 Hz because the response below that would be too difficult to interpret and could lead to all kinds of false conclusions. To really smooth out the room response in the bass, you need equalization equipment. And even then, it may only hold for a specific listening location. I published the full response of my MB0W3 3-way on my site, and I've taken grief ever since. What you see is what any speaker with decent bass extension will give you in my room. But it won't show you what the response would look like in your room, or what the inherent bass response is for that speaker. See http://murphyblaster.com/content.php?f=MBOW1_3-WAY.html

woody · « **Reply #16 on:** 2 Mar 2007, 10:47 pm »

< We can certainly post a computer-generated simulation of the response. >

Jim/Dennis,

Please do so! I would like to see that.

Thanks.

Fatawan · « **Reply #17 on:** 15 Mar 2007, 06:27 pm »

I'd like to see the same measurements for the HTC, especially the 50 degrees off axis

DMurphy · « **Reply #18 on:** 15 Mar 2007, 07:38 pm »

Well, I don't have a center channel anymore. But my basic advice is to not sit anywhere near 50 degrees off axis. MTM's just aren't designed for that, unless you can figure out some way to void basic Euclidian geometry. The relative position of the two woofers to the listener will change as you move off-axis horizontally (when the MTM is on its side, of course). That will change the relative arrival times, and hence the phase relationships, causing interference patterns with a big dip around the crossover region. That actually can sound kind of pleasant, but it's not the design target for on-axis seating. To avoid this in a horizontally oriented center channel, you need to use a three-way design so that the woofers can be crossed very low. The relative position of the two woofers off-axis will be less critical when the sound waves are very large.

Fatawan · « **Reply #19 on:** 15 Mar 2007, 10:47 pm »

I sent Jim a question about this, and I have been researching the MTM arrangement quite a bit. I do this because my setup makes some folks sit far out of that sweet center area, no matter how we arrange things. I don't want to deprive anyone of that centrally anchored sound experience! Ideally, I would get three HT1's. BUT, where to place that middle one becomes the issue. I have no good solution in my setup. So, how much effort would it take to produce an HTC in a three way design?

Does Seas make different sizes of that W18? Some of the graphs I looked at today had serious suckouts even 20-30 degrees off axis in some manifacturer's MTM designs.