Bjorn
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Posts posted by Bjorn
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Hi Langston. Did you find a measurement that correlated with your experience?
I've used class D amplifiers for a while and have not really recognized the same. There are some people here in Norway who AB tested the best class D vs the best measurable class AB and they haven't able to hear a difference.
Here's an intermodulation measurement of a Vera Audio power amplifier. Showing left and right channel.
You mentioned Bill Whotlock and his expired patented CMRR solution. Vera Audio used a similar design and developed it further. The CMRR of this amp is at least 89dB@100Hz and better than 94dB@1kHz.
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An off-topic question. Does anyone know which DSP the new Jubilee is using?
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Here's the raw measurement of the Celestion Axi2050 in the K-402 horn at 85 cm distance. 1/24 Oct. smoothing.
And here's a measurement at 1m distance of AXi2050 (green) vs Radian 950BePB (red). 1/24 Oct. smoothing.
As can be seen, the Celestion AXi2050 needs more boost in the highs. Or simply lower the frequencies below to get a flat response before adding the desired shelving. It's a large driver with a 5" voice-coil.
While the AXi2050 does give more level in the lows, it drops quite significantly below 250 Hz in the K-402 horn. Meaning a crossover of 4th order much below 500 Hz here might not be ideal, but this is up for discussion and is best to test by listening. The Radian 950BePB is best to crossover around 600 Hz if it's a 4th order. A steeper crossover might enable a little lower crossover for both. Depending on the distortion and directivity.
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1 minute ago, Chris A said:
I've got some in-room REW measurements taken at 1m with absorption on the floor between the microphone and front baffle. The Cornwalls are 1979 models with replaced tweeters--Crites CT125s (which at about 3-4 dB lower sensitivity than the midrange) which were already replacing the K-77 tweeters when I bought the Cornwalls used in ~2008. I also have measurements using an EV Dx38 DSP crossover that simply EQs the Cornwalls to a little flatter SPL response--but no bi-amping or tri-amping.
I know this isn't what you've actually requested, but it is available in case you get no other offers. Just PM me with an email address where I can send the REW measurement files (*.mdat). If you want me to extract plots from the measurement files, I'd be willing to do that, too.
Chris
Thank you Chris. Still of interest, though it's an older Cornwall speaker. And 1m distance with absorption on the floor is great. I'll send you a PM with email address.
Surprisingly very difficult to find measurements of these speakers, considering they have been in the market a long time.
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Has anyone measured one of these speakers and can post at least the frequency response? Anechoic, gated or nearfield measurements would be best, but even in room responses would be interesting to see.
Preferably one of the later versions but older models are also ok.
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It uses a 5" voice coil.
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1 hour ago, Tarheel TJ said:
Thanks for the response! Sounds like any of the Be drivers are a good choice.
I have seen that Keele horn referenced a few times on the 'net. Any more information you can share about it? Are they commercially available?
I'm not allowed to share any such information here. That would kick me out of here.
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14 minutes ago, Tarheel TJ said:
Slightly off-topic, but you are one of the few I have seen to have tested the Radian 950BePB. Have you also tested or heard TAD beryllium drivers? Can you compare the two?
I have always been curious about the Radian, as they are available new for somewhat less than the TAD drivers are used. They seem like they could be a good alternative if they perform similarly. Very hard to find any information from those who have experience with both. Thanks.
No. I haven't tested TAD drivers. Today I'm using Radian 951BePB (1.4") exit with a horn that I got developed together with Don Keele. Picture below and the best horn I've heard by far.
But I know some who have tested Radian Be (950 I think), different JBL drivers with Truextent Be (i.e. 2451) and different TAD drivers and have also measured them. If I remember correctly they were basically very close and perhaps not possible to distinguish audibly after applying EQ, apart from TAD 4003 which the person found to be slightly better than JBL 2451 Be (I don't think he tested Radian 951BepB). TAD 4003 is also the driver that measures overall best and seems to both go a bit lower in frequency and has more level/SPL in the highs. Unfortunately it's an exceptional expensive driver (not sold new anymore) and I assume we're talking about a minor improvement after equalization. The horn is certainly way more important, which the person who has tested these drivers also agrees to.
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Found a measurement at 2.3 m distance with both drivers that includes EQ. Hope that answers your question.
Red=Radian
Blue=Celestion
1/12 oct. smoothing.
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54 minutes ago, Chris A said:
If I might ask, how flat did you EQ the top end of the Axi2050, Bjorn? The TAD 4002s actually require a little attenuating PEQ on the top end, and easily extend their response somewhat above 20 kHz (which I typically don't test beyond 21 kHz). For younger folks that are still bothered by/can hear the ballast buzzing of fluorescent lights (about 16. 5 kHz), I can understand that you might perceive this difference much more than I would.
I added an 8 dB, 0.21 octave (BW) boost at 18 kHz, the differences between the TAD TD-4002 on the left and the Axi-2050 on the right were significantly decreased in terms of the high frequency "air" (for my hearing), but still present to a fairly subtle degree, which is what I reported.
I typically don't hand out poor reviews on audio equipment based on very slight differences--like I perceive in this case--but I'm the first to acknowledge that presbycusis is a factor in the differences we're reporting. For my ears, the difference is like listening to the TADs using a Crown D-75A amplifier vs. something with a much better bandwidth /slew rate (like the First Watt F3 that I use)--which is more of a subconscious difference rather than an overt difference.
I can both hear and measure the effects of the decrease in crossover frequency--listening to voices and their relative fullness, but it's not a strong difference--more like something that I could hear after listening to them A-B over a period of more than a couple of days of listening. The Jubilees have a tendency to sound a bit muffled when one is listening to them while laying on the floor between them about 6-8 feet away, and listening to them while seating properly in the reclining chairs just behind (i.e., vertical lobing), but not really in the horizontal direction, which seems basically unchanging from side wall to side wall (the room dimensions can be found in my profile page).
Chris
I'm certainly now talking about the frequencies around 16.5 KHz. I said upper midrange and treble. Obviously it's quite difficult to pinpoint what frequencies one is hearing the difference at, but my experience was this was also lower than only the very highest frequencies. Besides, my distortion measurements confirmed that the distortion already above 550 Hz was higher for the Axi2050. Below 180 Hz I saw lower distortion with Axi2050.
Actually, when listening to AXi2050 in the beginning I didn't notice it. When listening more I starting asking myself if something wasn't missing and it lacked some openness. I then started doing more serious AB listening tests and with various music material it became very evident. That being said, I'm a critical listener and details might be bigger for me than many others. So your mileage may vary. I know of two others in Norway have tested the AXi2050 with different horns and they came to the same conclusion as me by the way. One ended up using a tweeter crossed at around 4 KHz (bad place to cross IMO).
Below is a raw measurement of both drivers at 1 m distance. I need to look at EQ setting or measurements to answer your question, but I don't really think the super high frequencies are relevant here.
Red=Radian
Blue=Celestion
1/24 oct smoothing.
The cancellation at 700-800 Hz for Radian seems to be something with the combination of the driver and K-402. I haven't seen that with other horns.
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I tested the AXi2050 on K-402 in 2019 and did a direct comparison to Radian 950BePB. Back and forth for several days both in mono for quick comparisons and listening in stereo, though swapping for stereo takes time when you only have one pair of speakers.
My experience was quite different from Chris'. The Radian with Be sounded considerably clearer and more open in both the upper midrange and tweeter. Distortion measurements confirmed this. Crossover lower was nice though and mye experience her was also different. While it didn't experience this as night and day, it was still more than a subtle improvement in a coherent sound stage and vocal presentation. But overall, the Axi2050 sounded dull in the upper frequencies making it boring to listen to compared to Radian.
But I'm not surprised Klipsch is choosing such a driver for a commercial speaker and that solved issues with the bass bin they use.
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Stacking AMTs will cause both comb filtering and serious vertical lobing. That's simply physics with large center og center spacing, thus "small gap" doesn't help much here. How much that bothers people probably depends a lot on references and what's being compared to as well as the benefits. Almost all commercial speakers suffer from this to various degrees. It's something best to try out and hear for yourself.
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A poly isn't really considered a proper diffuser anymore. It focuses the sound at certain directions at certain frequencies strongly, thus doesn't evenly spread out the sound like a good diffuser will do. It can diffuse spatially well however, if several units with a weird dimension are placed next to each other. But it will not offer any temporal diffusion either way and is IMO an outdated product that's been replaced by something better.
Obviously I can't argue with you if you like the effect of it.
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Chris A:
You forget that a speaker which has a good power response, reflections don't contribute negatively anymore. Just ask Toole and his followers!
Kidding and sorry couldn't help myself. But it's quite disturbing and sad to see that what I wrote above is considered by many as science now and isn't even ut for debate! Just read some of the posts in the discussion I had with amirm and Toole at audiosciencereview forum.
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Each instrument and each vocal is a point source though. There's no doubt that a speaker that has a driver that covers most of both the treble and midrange sounds considerably more coherent. When you have gotten used to it it's difficult to go back to a speaker with a traditional crossover in the 2-4KHz region.
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3 hours ago, Chris A said:
I think that you may need to reexamine your comment:
In Toole's 3rd Ed., he references research that directly negates what you've said here, depending on your definition of "early". So does Griesinger's latest presentations on clarity.
Chris
No. This is very well established. And also extremely easy to hear for oneself by experimenting.
Your link talks about clarity in a different matter (large room acoustics) and has zero relation to this.
It saddens me that I actually have to defend this. I think this one of the reasons why very knowledgeable people don't bother to discuss as forums any more. Getting through the forest of confusion is difficult.
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High fidelity is accuracy. High gain lateral reflections isn't accurate no matter how constant the directivty of the speaker is. Early arriving reflections always has a negative effect on intelligibility, clarity and localization, thus accuracy. How much of the tonality is effected is dependent on the speakers directivity and surface of the room.
If one wants the combination of high fidelity and enveloping sound, the way to achieve this by attenuating early reflections and have late lateral diffuse energy. Which implies diffusion in the rear of the room with a good distance. This is something Toole never tried in his experiments by the way. It's also worth mentioning that Tool's research did on preference of lateral reflections wasn't very conclusive. One study was conducted in a anechoic room and it's no surprise that people preferred naked side walls in such dead environment.
But either way and preference set a side; high fidelity and early arriving side wall reflections is a contradiction.
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What would you choose a horn speaker like K-402 if you desire lateral reflections? A horn like K-402 minimizes side wall reflections with it's high DI. If you want lateral reflections, a horn is isn't the right choice and you might want to condsider a CBT speaker.
A traditional CBT speaker has a wide horizontal dispersion, avoids the floor bounce and minimizes ceiling reflections. FIY: I'm working on a CBT design with Don Keele.
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Seems to me your best bet is to go with stacked woofers. Sealed enclosure will give you the smallest footprint. Well designed horn subs become big.
Toole and objective high fidelity; Does that go together?
IMO he advocates mediocre quality in every area. Speakers with serious vertical phase issues and quite high distortion, and poor acoustic environment with lateral high gain specular reflections. Not much high fidelity in that if you ask me.
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I don't have experience with tapped horn subs myself but from what I hear from other that do, they don't seem to equal a front loaded horn in quality.
Personally I would go with a large front loaded horn or stacked 15" bass reflex subs. The latter equals a horn sub in quality when you have several, but the price is higher due to more drivers, cabinets and amplifier power needed to drive them. An advantage though is they can be crossed over high without any issues.
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9 hours ago, jazzmessengers said:
I thought the research showed that bass localization couldn't be detected below 80 Hz which is why I set that as my cut off. If it's 100 Hz then that does make it much easier.
You can cross over as high as 120 Hz to a single bass unit without having it conflict with the stereo image in my experience. Perhaps slightly higher to, but around 150 Hz one either need two separate units close/behind the fronts or a single unit in the middle between the speakers.
It's also somewhat depended on how far it is from the mains. Placing it on the opposite side of the room to the mains would obviously not work well with a cross over at 120 Hz.
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On 26.11.2017 at 5:20 PM, jazzmessengers said:
There was some discussion about this in the "dissect polar patterns" thread.
Bass horns to operate below the K-402 beside the Jubilee bass bin for a couple of reasons.
To get the K-402 at a lower height to facilitate listening to the speakers closer and still get a point source image. There are a couple of designs that I can think of that do this and I think that 3 feet tall bass horn is a decent upper limit to shoot for. For instance Inlow Sound has a dual 15", 60 Hz straight horn that is 36x36 at the mouth and 48" deep.
And a horn that can match the wide polar pattern of the K-402 at its lower limit.
For me 60-80 Hz lower cutoff for the bass horn is fine because I will be using multiple tapped sub horns to fill in the bass below that as well as smooth in room response. And my preference is for straight horns to cover that critical 60-450 Hz region. @Bjorn created a 100 Hz horn that had very nice response, and started a thread about it, I'm looking for something that will extend lower.
The midbass horn I got designed would have to be deeper if it were to go lower. I didn't want to do that because:
1. The depth it requires.
2. I believe crossing over higher is really a better option in terms of quality. Both related to frequency response and distortion, a separate bass solution will perform better. And as a side-not; contrary to what many audiophiles believe, there's no reason to run stereo below these frequencies.
If we use the acoustic roll-over of the horn in the filter, around 90 Hz is about the lowest it can be crossed.
I personally don't think a dual solution is a very good option for something crossed over in the 450-600 Hz area. The drivers will not sum very well and create phase issues in what I consider to be a critical range. So if you desire to extend lower, I would simply increase the depth of the horn with a single driver. A simple straight horn will not minimize the floor bounce as the horn I have, and probably not have an equal uniform polar either but it will still work well.
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The throat of the midbass horn is 110 mm if I remember correctly.
Not sure about the top horn, being still in the design process.
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The midbass horn has a mouth that's 120 cm wide and 85 cm high.
The top horn will be about 1 m wide and 76 cm high, but that may change. The vertical directivity will go lower than K402.
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miniDSP SHD Power & Hypex NC400 Class D Amps
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Thanks for the information.