AHall
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Posts posted by AHall
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42 minutes ago, Chris A said:
Adam, perhaps Roy will share his views on that subject soon.
In the mean time, I'm guessing that he will probably say something like "put it on the ground in a field" then use some higher-priced microphone and conditioning electronics at some measurement distance. Klipsch's anechoic chamber doesn't do much below 100 Hz due to its limited interior dimensions relative to subwoofer wavelengths and thickness of absorbent material necessary to be 90% effective in absorbing subwoofer acoustic energy, so you've got to move outside for these measurements (as is the case with virtually all anechoic chambers except those huge ones for aircraft measurements funded by the military that the major national labs and defense contractors own). But infrasonic noise shouldn't be a limiting factor when measuring outside in a country setting. In my neck of the woods, however, we've got gas drilling rigs and multiple interstate/major state highways surrounding us that never seem to find the "off button". So outside subwoofer measurement isn't a real option in places like where I live. So we measure inside to get a better noise floor environment.
However, measuring harmonic distortion (HD) I believe is fair game in a home-sized listening room. Moving the microphone as far away from the source as the home-sized listening room will permit is part of that story (as you have done) in order to get out of the near field to the degree possible. This is a subject that will not go away for home hi-fi enthusiasts and is very different from commercial cinema where it is comparatively easy to move 2 wavelengths away to measure out of the near field.
Harmonic distortion is usually not the measure of merit that we seek (rather it's modulation distortion and compression distortion), but when the harmonic distortion is with ~20 dB of the fundamental, then we've got to pay attention, since this will change the timbre of the subwoofer to something that's not in the original recording. I've heard this issue many times in-room, and it's something that buyers need to pay attention to, IMHO, especially those wishing to "keep it clean" as PWK used to say.
There is an option within REW to measure harmonic distortion using a stepped sine option within the RTA facility. The noise floors and relative harmonic distortion levels are much lower using this method. When you get a chance (and a little time in a quiet house--since these are long measurements) you can try this approach to get much better results. Here's a measurement that I did last fall using stepped sine on my right-side Jubilee (the drop-out at 15 kHz was due to intervening noise at the very end of the stepped sine sequence). The green trace is the actual averaged noise floor of the room. These measurements take something like 5 minutes each:
Chris
Once we establish an acceptable measurement method I’d love to see a step by step work method so I could get my data out there for you guys to dig into. Realistically I only care about these pro components being used in a home setting because that’s how I’m using them. Distortion levels included. I know all the designs I’m using are well engineered and regarded, but distortion/performance levels in room are what matters. That way I can adjust or correct dsp, gear, and treatment to reach 100% optimization in my system. I do acknowledge the open field and design numbers are very important so we can analyze what has changed by putting them in a normal room. Whether it be for the better or worse.
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1 hour ago, Chris A said:
I have nothing better to form an opinion. Plotted data doesn't appear to exist on this site for the unit and I don't see any other HD plots for the KPT-1802-HLS in quarter space or half space loading, especially for harmonic distortion levels inside 5 metres microphone distance (i.e., in a home-sized listening room). It would really help to bring that "blessed data" to the table for 4 to 5 m microphone distance to be relevant to home hi-fi listening rooms.
In the mean time, here is a plot of the harmonic distortion levels from a KPT-KHJ-LF (Jubilee bass bin) for comparison's sake. I've been impressed by the cleanness of its output relative to subwoofers, and I've consistently moved the crossover frequency downward over time relative to crossing subwoofer output because of that. Presently, I cross at ~30 Hz to the DIY horn-loaded subs that form rigid false corners directly behind the Jubilee bass bins:
Chris
Is there a standard for conducting a distortion reading or more desirable way to do it to produce better results? On couch or floor? Low spl, high spl, normal listening spl? Distance? Raw or with peq?
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I’m certainly not good at math, but going off the differences in cab measurements and applying it to a 12” and 10” version, they would both still be very big. Of course I’m sure I’m way off and you’d need to take into account the driver surface area and horn length/mouth size. And who knows what else. I think I’ll just have to leave the design stuff up to the people that know what the hell they are doing. It’d be cool to know the actual theoretical external dimensions though.
1802 1502 1202 1002
SA 254.47 / 176.71 / 113.1 / 78.54
H 48 45 42.18 39.55
W 74 68 62.48 57.41
D 31 27 23.51 20.48
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I wonder how well a 1002 would match up between some khorn bass bins for my bedroom setup. If it ended up being about half the size of an 1802 that’d be one cool little coffee table looking sub!
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1 hour ago, Chief bonehead said:
And what about room gain? When you put the door back on did you make sure it sealed correctly? One huge misconception about vented systems is that they don’t have to air tight. The best way to take advanatage of the low end of a vented system and do it efficiently is to boost at the tuning frequency. With a horn sub this large and in your specific room, it will be dry different than say in the lab. Best way is to run an impedance curve to find the tuning of your sub.
Next week when I get back home from work I’ll double triple check the sealing of the back of the cab. I didn’t notice any damage or disfigurement of the seal. Also was very careful to center the board and tighten evenly. I’ll have to have someone help me figure out the impedance curve. I can email REW files to whoever is willing to look at all the specifics in the measurements that I do not understand.
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Also I’m not sure if a second factory driver would be correct in the dual configuration due to the volume. There is 13.75cu/ft inside the chamber. 22x24x45”.
As best as as I can tell the driver is an eminence. Labeled 4ohm. I haven’t had a chance to look through the whole line up and compare the pictures and specs.
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2 hours ago, Chris A said:
Right...if you're talking about going down a half octave to ~19-20 Hz, then the quarter space of the room (i.e., a typical case with the sub against a wall and sitting on the floor) is doable. If however you're thinking of trying to get 10-12 Hz--more than an octave below half space cutoff--then you will likely need eighth space loading, i.e., a room corner. But at these frequencies, there is some blurring of the differences between quarter space and eighth space since even at mid-wall, you're probably within a quarter wavelength of being in the room corner at 10-12 Hz (23.5-->28 ft quarter wavelength), so it gets a little unclear in terms of predicting what's going to happen.
Also, since you're talking about a ported design, at some low frequency I would guess that you're going to get 180 degree inversion of phase from the ports internally, so that really becomes the limiting factor in bass extension. A purely front loaded horn with sealed back-chamber would see that 1/2 wave cancellation from the length of the horn itself (as is seen in the Jubilee bass bin at ~20-25 Hz).
Additionally, the preliminary measurements of harmonic distortion below ~20 Hz show that you're already getting to diminishing returns with the 1802 in its benign ported condition. It may be worthwhile to replace the internal ports with another identical 18" driver (probably wired in series in order to keep the impedance from going too low, or even bi-amping the woofers) and get what you get in terms of resulting frequency response smoothness--and use the Xilica to smooth out what you get. You may be able to EQ using IIR filters, but you can't do much about phase response below ~100 Hz--which is audible. I find that flat phase response is your biggest friend in the deepest subwoofer frequency band in terms of perception of very deep bass.
Chris
I would like to know the results of the dual driver configuration since it was already tested. I wonder if the factory bracing would be adequate in a sealed configuration. It seems like all the designs I’ve seen of sealed subs have massive amount of bracing to prevent enclosure flex and resonance.
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I was told my specific setup(horn mouth flush of front wall) is still considered 1/4 space with the wall and floor boundary.
Roy, do you see anything out of place with the performance I am seeing in my room? Response has never looked better, both raw and eq’d. I feel I may have something out of order causing my driver to bottom out. Any suggestions for setup/tuning parameters I should change? I wasn’t expecting to ever find the limit of this sub and if I did, I was thinking it’d be closer to 130db. Based on the advertised continuous/max spl numbers I can’t help but think I’ve messed up some numbers in the xilica.
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This is the results of no hpf, bessel, butterworth, and linkwitz. 48db slope
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Update on this. With the 2 port closed configuration it seems to naturally be flatter and go lower. Today I found out that this sub will bottom out around 118db for bass heavy music when not using a HPF. So I decided to unplug the ports and let it run as it was designed. Here are my results of doing so. The peq’s were for 2 port closed configuration so I could see the difference.
All measurements taken at the seating position. 13ft from horn mouth.
The butterworth HPF seemed to maintain good response and rapidly dumped anything below that. I figured I would try it to see if it helps the issue.
This is the current eq’d response and peq I’ll be trying. Open to criticism as always.
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10 minutes ago, dtel said:
True, it was rated around 20 and that was halfspace, put it in a room and it goes into the teens, easily if you block another port.
This is the response at the seating position I’m currently getting. And the peq to achieve it. I run my LFE crossover for movies at 120hz, hence the need for higher flatness.
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I use a vta70 with el34 tubes on the 402 and anthem mca20 on the jube bass bin. When I was first learning rew/xconsole and having Chris do all my peq via email I used 4ch on my anthem mca50 amp to simplifies things. Now that I’m more familiar with things I found the gain matching portion very easy. I’m much happier with tubes up top. Best of both worlds.
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Good price. I love my vta70. Sounds fantastic. These amps are often said to have equal or better quality than McIntosh 275 etc.
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1 hour ago, babadono said:
@MisterVego Are you trying to get the 1502 to dig a little deeper? @AHall has been doing port plugging tests on his 1802 to try and get it to go a little lower. Don't know if you've seen his thread.
Erik is a friend of mine thanks to the Jubilee community. We have been brainstorming some ideas including the port closure. He’s much more knowledgeable than I am on most of this stuff. With the help of the experts on here I’m certain he will resolve this.
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Throw a blanket over it. Problem solved. Enjoy the music.
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I wonder how this compares to my sl-1800mk2. I don’t have a quality phono preamp so I’ve never really messed with it. Came with a AT152MLP. I bought a shibata stylus for it, but haven’t never used it since.
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1 hour ago, pzannucci said:
Are they measuring and compensating with eq? How different are the curves with the zxpc horn vs what we have seen posted for say the 510?
Im not certain how different the curve is. Yes it was eq’d using REW and xconsole software. I can only talk from personal experience when I eq’d my k510/Heresy center channel with radian 950. Biamp configuration.
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4 hours ago, pzannucci said:
Good flexibility, you just need to make sure the horn and driver actually sounds good. No eq will fix a problem there.
I run a Radian 950 driver in my k510 center channel. It sounds very good. Premium driver that is fairly inexpensive. The 18x10 zxpc horn is said to perform similar to the k510. Also I have a friend that is running the zxpc with k691 for the HF on his LaScala center channel and is having great luck. Loves it.
16 hours ago, MenloBob said:FleaBay? I haven't had any luck finding cheap xilicas..
Yes. They come up every now and again. I just got the 2040 just to do my cornwall surrounds.
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On 4/21/2019 at 3:42 AM, pzannucci said:
Why active? It will really matter on what driver you are connecting to it as to how hard it will be to manage with a passive network, or active.
I believe it is a cd horn like the k510 and k402. So there will be some peq needed to compensate some boost and drop in the freq. Also does not limit you on which driver you want to use. Additionally my second xilica(2040) was only $400 in like new condition. The massive amount of adjustability in an active crossover is a no brained when coming the price to a passive network.
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I’d like to see some more people use the zxpc 10x18 with an active xover.
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How low can we go without distortion? When we enter below that threshold how audible is the distortion? Is the low end extension worth the added distortion to provide that wow factor for movie ULF?
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2 hours ago, Chris A said:
Perhaps it might be instructive to discuss pressure zone acoustics instead of guessing what it really means. The following was taken from this link: https://www.acousticfields.com/room-pressure-zones/
If I read this correctly, in order for most listening rooms to be considered to be operating in the "pressure zone" using subwoofers having response up to 80 Hz, the room would need to be small enough to be in the pressure zone at subwoofer frequencies. That would mean to me that the maximal room dimension would be on the order of 12-14 feet in order to be operating in the pressure zone at ~40 Hz and below.
So perhaps--you're both right...just at different assumptions of room size and frequency band of interest. In larger-sized listening rooms, there really isn't a pressure zone--say 30-40 feet long (mine is 40 feet long, so I don't deal with pressure zone, but I do have to deal with sitting inside the nearfield of the horn-loaded subwoofers--much less than 2 wavelengths).
Chris
This is still way over my head. Especially with my odd shaped room, half walls, and open floor concept.
I am glad to have a more in depth discussion on this. I’m all ears on trying to improve the current performance and sound quality I already have. I’m sure there is a lot of optimizing in tuning and treatment left on the table. I just have to learn how to achieve it.
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23 hours ago, Chief bonehead said:
thats interesting....since the 1802 was developed for cinema use for......wait for it.....movies. i have never seen a sealed sub used in cinema. wonder why?
Am I incorrect in my thinking? Trying to get an 1802 to play full spl below what it was designed to do? Why not roll it off at 22-25hz and let sealed subs cover that last 10hz?
If there is a way to achieve what I’m looking to do with only the 1802 I’m all for it. I just didn’t want to create a bunch of distortion by boosting its bottom. Or damage the driver with ultra low freq effects.
Edit for clarity -
My suggestion was to use only the 1802 for music due to the seamless blending with the jubes. The sealed subs would not be playing here as I believe they would dirty up the SQ by not being low distortion horns.
And for movie duty I would still be using the 1802 in full force, but using the xilica to do a 24db or 48db high pass filter. The second xlr output on my anthem pre/pro would be feeding sealed subs. All subs would work together until 25hz where the 1802 would roll off and the sealed subs would continue to output down to 15hz or lower.
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12 hours ago, dtel said:
It started out with 2 drivers, the performance was much nicer with one, also a drone was next, the exact words were it got shredded to pieces. It sounds like(from asking) the best change was to block a port or 2. Other options were tried with less success, way before it became a product, the number of ports was to get maximum performance and output to do a certain job, fewer ports by blocking them is what is recommended for more depth with a slight reduction in overall output, but in a home that's not a problem I would think.
I'm just repeating what I was told, and I think I got it right since it's the same thing with the 1502. There are a couple of ports blocked on mine but it was a prototype and was done while tuning, it started out with more ports and tuned by blocking a couple of them off until they were happy. I was told I could block more if I wanted to go lower but have done nothing but may try it one day? I was told the difference in the 1502 to the 1802 was 2-3 db, since I'm nowhere around the limit (I guess) it makes no difference to me.
Be back in a few days, going to work on the museum, it's tough we have to listen to some Kp 600 and an 1802 as we work.
I’ve heard this. I always wondered specifically what “better” means when referring to the performance of a single vs dual driver configuration. Was it better distortion, output, low response, tight sound, general fidelity, etc? Maybe something else that separated them so much?
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1977 Klipsch Cornwall parts for sale? $485 shipped obro
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