Agreed.
Here’s measurements from my prototype using what I had laying around (old boxes and old tweeters- so baffle dimensions, driver placement, CTC distance, cabinet volume and port tuning were all fixed) prior to crossover work.
but still fairly respectable on axis and horizontal response… out to 90 degrees:
https://www.diyaudio.com/community/...er-speaker-builds.352063/page-47#post-6821857
I agree with Pida. T34A/B for a 2 way sans waveguide, if you want to go with a dome…
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Thanks for getting back to me on that. Very interesting. This driver was under my radar. Any chance that you also tested the MAF061.50? It's not the same as the MAN version (has different VC diameter for example) but it would work out better for me. Not too expensive so I may just pick up a pair and give them a try.
What a strange thing, when comparing both datasheets: The T34B has a much bulkier voice coil (larger diameter and higher wound) than the T25B. And both drivers have theirs specified power input capacity declared filtered LR4@2500Hz. So why - surprize, surprize - the T25B is rated 100W, whereas the T34B is rated ... only 80W! Has anyone an explanation for this? Eventually a lager gap for the T34B which does not transfer heat this intensly than for the T25B? Or something else?
This said, crossover flexibilty seems not so brillantly better for the T34B as intuitively admitted. To it's credit, the T34B has a much better sensitivity than the T25B, better than the differences of theirs impedances would show. Looking at the audiocompass measurements, for a SPL of 96dB > 2k5 you will have to input 2.83V for the T34B, but 5.6V into the T25B instead. The bonus for the T25B? Smaller size. And the T25B will give you slightly less THD (-50dB @ 96dB) than the T34B (-45dB @ 96dB) in the range from 2.5kHz ... 10kHz. The waterfall spectrum seems comparable between the two. No winner here, both waterfalls are not perfect, but fair. I wonder how these waterfalls would look like without the protective grill.
There is no hesitation on my side.
Seen from an objective side of things, given to use a waveguide (not just a standard tweeter)
Because the way our hearing works, vertical directivity isn't nearly as important.
Second is that for all speakers involved, distortion (of any kind) is an order of magnitude less important than a good frequency response as well a good linear directivity. Or in other words, the distortion is low enough with all these speakers we're talking about.
Next is that an higher DI will give you less reflections in the first place.
Which in most cases is also more significant than distortion issues.
All these points seen from a rational perspective, some people just like the sound of a more omni directional type of speaker (low DI index). There is nothing wrong with that, just has certain consequences.
Even without a waveguide I would have no issues crossing that Bliesma tweeter lower, even a simple Seas 27TFF can be used easily at 2kHz. I know that Martijn from D&D even pushed it from 1800Hz way back in the day with no issues at all.
If I look at the distortion graph of the T25A or T25B, that doesn't seem to be an issue as well.
Agree. I use a Satori TW29TXN-B with an LR4 filter at 1.6 kHz, and I play music loud, in a big room. The BlieSMA T34B has more capability than the Satori, more Xmax and lower distortion in the 1k-2k region. All in all, it is just a more capable driver. If I was using the T34B, I do not know how low I would be comfortable crossing it, but 1.5k would be no problem.
There is also other benefits by 3 way. You can have much better in room response, when using right crossover frequencies and driver placement. (You can simulate with vituixcad)Exactly this, or the directivity.
I understand that for some people it can be a bit scary to mess around with some speakers.
But first of all there are alternatives, second if we're spending a good amount anyway, I would pay a professional to do these tweaks for me.
At this point it feels a bit like a no-mans-land choice.
With no disrespect btw, I mean if you're happy with it and it sounds incredible to you, happy days!
Anyway, totally off-topic, sorry.
I have totally same opion that pida. With 6" driver 25mm tweeter have it's limit about directivity and usability. T34 is better suitable with ptt6. 25mm tweeter without waveguide works better with 4 and 5" driver. You can see that from directivity pattern just posted. (Ptt6 and millenium). That is nowhere near that good what pida achieve with him's 3 ways.
If we are talking about a real good in-room response, an high(er) directivity index will always win.
Which can only be achieved with a proper waveguide (or horn).
This is objectively many miles better than a 3-way system, in terms of interaction between speaker and room.
(not in terms what you think sounds nicer)
Compared two a traditional 2-way system, yes, maybe.
But at that point were are also completely neglecting any practical difficulties that comes with a 3-way system.
can you point to the evidence of this statement?
It’s not even clear if, in real rooms, directivity is correlated with listening preferences in double blinded studies.
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Point to evidence?
It's an intrinsic result of an higher directivity index?
But in general I would recommend reading Sound Reproduction by Floyd Toole.
He showed very well that directivity is one of the main factors of sound quality.
Earl Geddes showed this as well.
They both have done plenty of double blind tests.
So why this little snippet says it's not, I don't know.
I also don't know the full context of that screenshot since Erin himself knows that a good and constant directivity is very important.
Also it seems to be from Harman?
Which makes even less sense since Floyd Toole worked in behalf of Harman.
If you're talking about if an higher directivity index is preferred?
I never said that it's always the case.
A technical good in-room response isn't the same as listening preference.
An higher DI will give you less reflections and reverberation by definition.
If that's desirable totally depends on the type of room and how well the room is treated. It also depends if one prefers detail or prefers spaciousness.
It also depends on the amount of listeners.
Btw, maybe we could ask the moderators to split this of to a new topic, because it's getting heavily offtopic?
I never said that it's always the case.
A technical good in-room response isn't the same as listening preference.
An higher DI will give you less reflections and reverberation by definition.
If that's desirable totally depends on the type of room and how well the room is treated. It also depends if one prefers detail or prefers spaciousness.
It also depends on the amount of listeners.
Btw, maybe we could ask the moderators to split this of to a new topic, because it's getting heavily offtopic?
The screenshot comes from Sean Olive's presentation notes that he put up while doing an interview with Erin.
Toole did not test directivity index (how directive the radiation is) and listener preference. In fact, he mentions that is one area that needs more investigation. Now smoothness of DI is something that is part of their preference metrics. There is some reason to doubt high DI always wins. There was a well known series of listening tests of the Revel Salon 2 vs JBL M2 put on by a Harman dealer. Toole participated in one. The Revel was preferred at all events. Not by huge margin, but preferred nonetheless.
Right, that's why I added another reply, because I realized that's what he probably meant.
To repeat it again;
An higher DI will give you less reflections and reverberation by definition.
If that's desirable totally depends on the type of room and how well the room is treated.
It also depends if one prefers detail or prefers spaciousness and probably the kind of music as well.
It also depends on the amount of listeners.
That being said, someone with experience, can kind of design something that will likely work in a lot of rooms on average.
Based on my experience, and going back to the original discussion, the DI of a 6,5 inch + waveguide tweeter definitely falls into that category.
In that discussion I was referring to a well constant/smooth directivity.
I already mentioned that a more omni directional speaker could be something that one would prefer.
To repeat it again;
An higher DI will give you less reflections and reverberation by definition.
If that's desirable totally depends on the type of room and how well the room is treated.
It also depends if one prefers detail or prefers spaciousness and probably the kind of music as well.
It also depends on the amount of listeners.
That being said, someone with experience, can kind of design something that will likely work in a lot of rooms on average.
Based on my experience, and going back to the original discussion, the DI of a 6,5 inch + waveguide tweeter definitely falls into that category.
In that discussion I was referring to a well constant/smooth directivity.
I already mentioned that a more omni directional speaker could be something that one would prefer.
It’s been shown that smooth and uniform DI is preferable. Also that smooth on-axis response is preferable. Fairly easy to conjecture - if not already proven - that a good sounding speaker has to have smooth DI and frequency response across the listening window. Does it need to have a high DI? I think b_force is right to ask for evidence on that, which hasn’t been shown so far.
I should point out that all of Harman's (Olive and Toole) investigations about DI and power response, and therefore the conclusions about smooth DI and flat on axis frequency response were compiled using direct radiator loudspeakers in boxes. I build dipole loudspeakers and I find that the flat on axis response sounds too bright in a very obvious way. It's only when I tilt it down by about 6dB per decade using EQ that did the tonal balance start to sound "right". I based this EQ on some of the work that Olive and later Toole published on preferred in-room response curves (e.g. see Toole - The Measurement and Calibration of Sound Reproducing Systems JAES 17839, section 4 - Small Sound Systems). This might be due to the relatively constant DI of the loudspeaker when equalized for flat on-axis response compared to other types of loudspeakers, and so to achieve a similar DI the dipole loudspeaker must have its on axis response tilted down. Just a guess on my part at this point.
I think their early research used the Quad dipole speakers. But yeah, certainly not a large sample or more modern designs. Interesting to hear your thoughts on the on-axis response. I have a dipole I want to build and this was always a question in my mind. I don't see it talked about ever, but my thinking was exactly your experience: the in-room response at the seating position should be sloping, and with a good dipole this would require the on-axis also be sloping.
Yup. I always suggest using the SPIN data to build an estimated in-room response (this can be done via VituixCAD quite easily if you have the data on-hand).
IME, speakers that measure flat on-axis but have a very broad horizontal dispersion (say greater than +/- 70 degrees) start to run the risk of becoming bright in the seated position. This is due to, as you said, the fact that the early reflections are practically as high in SPL as the on-axis response. Notably, ribbon-type tweeters are keen to do this vs dome tweeters due to their wider horizontal radiation pattern.
Of course, the worse the directivity through the crossover region, the worse this becomes because things are relative. If you have a scoop in the mid/tweeter region but the tweeter picks right back up then I find that the treble is more of an issue than if it were more constant directivity.
Either way, though, yes, the less directional a speaker and the more flat on-axis, the "brighter" it tends to sound based on my experience comparing data with what I hear in-room.
I reviewed the ELAC UBR52 last summer (link). It used a concentric mid/tweeter. And it had a broader radiation pattern than most concentrics (Kef / Genelec). The thing I thought was odd was that the on-axis response was sloped downward as you went toward the HF region. But, once I compared my notes from my listening to what I was seeing in the data, I realized that was the entire design. Andrew Jones had designed the speaker to purposely be sloped downard on-axis because he knew if he made it flat, the wide(r) radiation of the concentric was going to cause the speaker to sound bright.
Keep in mind that directivity itself should also be taken a bit on a practical way.
A "perfect" directivity up to 20kHz looks nice, but I really doubt if that's very useful?
Local absorption above around 8kHz is extremely high (this can be actually very easily seen with difference with in-room measurements for example).
I slight tilt is preferred by most I think, although it also really depends on you hearing (which sometimes also means age
)
A "perfect" directivity up to 20kHz looks nice, but I really doubt if that's very useful?
Local absorption above around 8kHz is extremely high (this can be actually very easily seen with difference with in-room measurements for example).
I slight tilt is preferred by most I think, although it also really depends on you hearing (which sometimes also means age
)SL did a similar thing with his dipoles, a -3.3dB shelving EQ centred at about 1740Hz, Orion and LX521 were way too bright for me without it engaged. I still use a variation of that same EQ now. Having a tilt at that point does seem to do something right to the sound.
https://www.linkwitzlab.com/orion-rev3.htm