The scale is a relative dB one and it does show that the the bulk of the waveguide loading is centred on 2.5K. That has to be cut and the downward trend equalized which will create a very different look to the graph.
You can see in the Throat Impedance graph from the previous page that there is a big hump around 3K and that by 1K the real value has dropped to next to nothing. The driver is well and truly on it's own by 1K and distortion would be very much the same as a flat baffle at that frequency.
This is more difficult to see than normal because each of the separate parts of the tweeter creating output have been plotted separately.
🟡 Hello Friend! How do I run this project? I searched the fórum audioheritage but it's all very confusing, there's no cut project, speaker suppliers, step-by-step assembly scheme, etc.Back on topic: another nice M2 build from the audioheritage forum:
The builder's comment on the M2 vs his Dynaudio acoustics studiomonitors :
"I already liked the Dynaudio a lot, but the M2 sound much better in many aspects! Strings (violin, cello) sound more realistic and less aggressive. Low frequencies are much cleaner (and deeper) and directivity considerably lower! All in all, a nice improvement."
Do an M2 search or start a thread. If you go through the larger threads the info is there. That's just one of many build threads. Just PM the OP's and I am sure they will help you.
http://www.audioheritage.org/vbulle...ject-M2-DIY-Thread&highlight=active+crossover
Components can be found here:
https://reconingspeakers.com/?s=jbl+m2&post_type=product
Bjorn Kolbrek can provide some
"Both exponential and hyperbolic horns have a property called cutoff. Below this frequency, the horn transmits nothing, and its throat impedance is purely reactive. But what happens at this frequency? What separates the exponential and hyperbolic horns from the conical horn that does not have a cutoff frequency? To understand this, you first must look at the difference between plane and spherical waves. A plane wave propagating in a uniform tube will not have any expansion of the wave-front. The normalized acoustical impedance is uniform and equal to unity through the entire tube. A propagating spherical wave, on the other hand, has an acoustical impedance that changes with frequency and distance from the source. At low frequencies and small radii, the acoustical impedance is dominated by reactance. When kr = 1—i.e., when the distance from the source is 2 λ π —the reactive and resistive parts of the impedance are equal, and above this frequency, resistance dominates. The difference between the two cases is that the air particles in the spherical wave move apart as the wave propagates; the wave-front becomes stretched. This introduces reactance into the system, because you have two components in the propagating wave: the pressure that propagates outward, and the pressure that stretches the wave-front. The propagating pressure is the same as in the non-expanding plane wave, and gives the resistive component of the impedance. The stretching pressure steals energy from the propagating wave and stores it, introducing a reactive component where no power is dissipated. You can say that below kr = 1, there is reactively dominated propagation, and above kr = 1 there is resistive dominated propagation. If you apply this concept to the conical and exponential horns by looking at how the wave-fronts expand in these two horns, you will see why the cutoff phenomenon occurs in the exponential horn. You must consider the flare rate of the horn, which is defined as (rate of change of wave-front area with distance)/(wave-front area). In a conical horn, the flare rate changes throughout the horn, and the point where propagation changes from reactive to resistive changes with frequency throughout the horn. In an exponential horn, the flare rate is constant. Here the transition from reactive to resistive wave propagation happens at the same frequency throughout the entire horn. This is the cutoff frequency. There is no gradual transition, no frequency dependent change in propagation type, and that’s why the change is so abrupt."
"The OS waveguide does not have a sharp cutoff like the exponential or hyperbolic horns, but it is useful to be able to predict at what frequency the throat impedance of the waveguide becomes too low to be useful. If you set this frequency at the point where the throat resistance is 0.2 times its asymptotic value30, so that the meaning of the cutoff frequency becomes similar to the meaning of the term as used with exponential horns, you get 0 c t 0.2c sin f r θ = π (24) You see that the cutoff of the waveguide depends on both the angle and the throat radius. For a low cutoff, a larger throat and/or a smaller angle is required. For example, for a 1″ driver and 60° included angle (θ0 = 30), the cutoff is about 862Hz. The advantages of the OS waveguide are that it offers improved loading over a conical horn of the same coverage angle, and has about the same directional properties. It also offers a very smooth transition from plane to spherical wave-fronts, which is a good thing, because most drivers produce plane wave-fronts."
https://www.grc.com/acoustics/an-introduction-to-horn-theory.pdf
Thanks a bunch fluid!
That answers quite a few questions that have been debated many times on the forum. I'm not sure I can completely and fully understand all aspects of it but it helped me quite a lot (I hope).
Would it be fair to say that as a horn/wg gets reactive, the driver is moving but the pressure energy gets produced and consumed within the horn/wg and nothing gets out of the system? That a wg with Re 0 and Im=1 would be silent?
Looking at one of these:
Is it possible to read out the CO freq?
Below the CO, it would be like the driver was without a WG and no directivity control can be offered by the WG?
// (sorry for a bit of OT)
That answers quite a few questions that have been debated many times on the forum. I'm not sure I can completely and fully understand all aspects of it but it helped me quite a lot (I hope).
Would it be fair to say that as a horn/wg gets reactive, the driver is moving but the pressure energy gets produced and consumed within the horn/wg and nothing gets out of the system? That a wg with Re 0 and Im=1 would be silent?
Looking at one of these:
Is it possible to read out the CO freq?
Below the CO, it would be like the driver was without a WG and no directivity control can be offered by the WG?
// (sorry for a bit of OT)
No, not really. It depends a lot on the capabilities of a particular driver and the power requirements, whether is it for a home use or not.
And it's not possible to tell what the directivity is based on the throat impedance alone - that's virtually unrelated.
Think of a woofer and how many times you looked at the acoustic resistance it radiates into - it's almost nil at the very low frequencies as well. That doesn't mean it can't reproduce those frequencies at high enough level, if it has the volume displacement capabilities needed. The real part of the impedance is never zero.
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You're welcome.
I don't know that it would be a yes or no answer but horns with defined cutoff's become problematic at or below cutoff due to the rapid phase and frequency change.
According to Bjorn when the real drops to 0.2 from an asymptotic 1.0 that is the point where an OS throat impedance is too low to be useful. If the driver itself is still capable of producing the required SPL then that becomes a moot point.
In loading or output terms maybe but as mabat says directivity is not linked directly.
Hello Hobh3606!
I've been reading this whole time on the forum you indicated and looking to listen to the M2, there isn't a video with a good capture or a song to analyze.
Something tells me I would be happy with blue monitors like the JBL 4365 DIY JBL 4345 DIY JBL2235H. Here at Bazil we don't find these monitors to listen to them, I don't believe they exist here.
I came to take up your experience again. What is the best DIY JBL monitor in your opinion?
Silvio, If you want to have a listen to the big JBL monitors an obvious place is Kenrick sound on youtube. Nice recordings. I don't recall seeing an M2 there though...
Hello Silvio
I have limited experience with the old "blues". I have heard 4331's 4333's 4350's and they are great for what they are. I own a pair of 4344 clones and again really like them but they have limitations just like any other design. The real problem now is that JBL/Samsung has stopped supporting the drivers so there are no longer "original" re-cone kits. The generics are just that and completely a hit or miss compared to the originals kits.
When I built my 4344 clones years ago you could purchase frames and new kits and end up with essentially brand new drivers. Those days are gone and I would not try for a clone one of these older stock systems. About the only drivers you can still get new kits for would be the compression drivers and even these are more modern ones that fit. So that "stock" sound is going to get lost in the translation.
The original 4300 series used exponential horns so there are issues WRT polar response and changing DI. I think the latter 4400 series like the 4430/4435 sound better with the 2344 Horn but again this is a 1980's vintage system. I like these horns but when used above 1.5K but then there are some that see a diffraction slot and immediately dismiss them.
4365 is a modern system not to be confused with the original "blue" monitors. I would give them a listen if you can. I would go with the M2 over the older systems.
I have a passive M2 based speaker but use a large format 4" compression driver. I like them better than the 4344's. A video is not going to capture the imaging and sense of immediacy that the M2 components seem to have.
Rob
Hello Silvio
I also liked JBL 4348
This JBL 4425 It has a very pleasant sound, we know that the listening room and the equipment favor everything
01 - Galicia Flamenca
02 - Long After You're Gone
03 - 'S Wonderful
Anyone, there's no rush or deadline 😊
Rob
Is there any supplier more reputable than another?
Is the JBL 4425-MKII possible to make? I liked his sound from the video.
I also liked JBL 4348
This JBL 4425 It has a very pleasant sound, we know that the listening room and the equipment favor everything
If it's not too much trouble I would ask you to record a specific song for me to listen to.
01 - Galicia Flamenca
02 - Long After You're Gone
03 - 'S Wonderful
Anyone, there's no rush or deadline 😊
Rob
There is this other thread by the same OP where he explains how such horns could be made from scratch.
https://www.diyaudio.com/community/threads/how-to-make-a-new-wave-biradial-horn.315625/
Thus, it maybe possible to replicate the 4425mkII, provided the exact dimensions of the horn and baffle are known. However, there's very little information on the 4425MkII in the public domain, with no proper drawings apart from the technical manual.
Thanks for helping me!
No friend, I do not take into account appearance, I like deep bass but velvety, I appreciate the musicality of the speaker and not the music in question.
When you're on the other side of the planet the only thing you have left is a video, it gives me an idea of how good it "can" be. I know what I'm hearing is my HD600 and not the JBL. You wouldn't be able to record a video with sony muteki and convince an audiophile that it sucks. A video helps a lot in the decision of those who do not have direct contact.
If the microphone captures the full audible range I will know the intensity of the bass or if the treble is too colored, that's all I can judge, the timbre depends on being present at the performance event.