This is why speaker manufacturers need to produce more small form factor tweeters. I recently criticized Dayton on their new Esoteric tweeter for having an even larger than 104mm faceplate.
Hi Charlie,
Ah sorry, my bad, I mistaked : I wanted to talk about the B&G Neo 8 serie (not 6 : never launched and even planed : my dislexia !), especially the S serie which is almost 600 hZ to 20 k in sealed enclosure :
http://meniscusaudio.com/images/NEO8S-spec%20sheet%20Rev1.pdf
Proraum Vertriebs-GmbH | Shop[shop_articles][action]=details&index[shop_articles][category==11&index[shop_articles][data][shop_articles_id]=105 : is this one a S or a PDR serie ?
But it becomes hard to find it as B&G seems to want to stop DIY distribution !]%[/category]
There are a couple of problem that I see with the 8S as the "F" in an MFM.
#1: the driver doesn't reach much above 10kHz on axis
#2: there is a large peak on axis around 10kHz, and off-axis the response is falling off rapidly at that frequency.
#3: the ribbon is too tall to be used as a tweeter. You can see the effect of this in the vertical off axis plot. Starting at about 2-3kHz the response is beaming strongly.
#4: typically ribbons cannot be crossed over very low unless they are large, like this one. The flip side of that is that the size of the radiating area is contributing to the off axis problems at high frequencies, but you can't have it all. Surprisingly the suggested crossover point is as low as 250Hz (!) but IMHO that is really pushing it. 500Hz could work well, however, and this might be great between 500-3kHz or even a little wider range.
If you are looking at options, I have heard a very nice MTM system that used a 10" or 12" horn and a compression driver as the "T", both of high quality. The size of the horn mouth still prevents a close M-M spacing, but if you can cross the horn low enough (low 1kHz range) then it can work without too much of a hole in the off axis response at the high end of the M's passband. Maybe that would be another option for you to consider?
B&G Radia, previously know as Bohlender-Graebener, was sold around the beginning of 2015. The new owners are not as interest in the DIY market. Websites such as Partexpress and Meniscus Audio state the items are out-of-stock, with negotiations pending with the manufacturer.
David Graebener of the orginal Bohlender-Graebener also passed this January, 2015.
David Graebener of Bohlender-Graebener Fame Passes Away - Article from CE Pro
Ah ! Thanks 🙂
Heard in a sealed some push it at 18 K hZ ! Minimum crossing people experienced with it was 600 hZ ! (datasheet is a little to gentle !)
I don't need especially a MTM, but have close needs as Lewinski01 : we started both with close road map : Beyma TPL150H & Beyma 12P80nd... Lewinski keeped the Beyma AMT as a targett and I keeped Something close to the Beyma woofer philosophy as my main concern is the 80 hZ to 1000 hZ (around) targett with high efficienty !
Btw don't want to pollute Lewinski threads but post sometimes in the hope that helps to a larger thinking around this design as I learn also in the same time !
I never heard a good matching between a horn, a room and the over cones drivers... but I didn't experienced 10 000 different systems listening either ! But hey, if you can link the MTM you talk about, it's great 🙂 !
@ twinter : maybe the ones I linked in the german Audax shop site are not genuine ??? But they used to sell BG planars for a long time ! I know there are chinese conterfact on the markett as well !
Heard in a sealed some push it at 18 K hZ ! Minimum crossing people experienced with it was 600 hZ ! (datasheet is a little to gentle !)
I don't need especially a MTM, but have close needs as Lewinski01 : we started both with close road map : Beyma TPL150H & Beyma 12P80nd... Lewinski keeped the Beyma AMT as a targett and I keeped Something close to the Beyma woofer philosophy as my main concern is the 80 hZ to 1000 hZ (around) targett with high efficienty !
Btw don't want to pollute Lewinski threads but post sometimes in the hope that helps to a larger thinking around this design as I learn also in the same time !
I never heard a good matching between a horn, a room and the over cones drivers... but I didn't experienced 10 000 different systems listening either ! But hey, if you can link the MTM you talk about, it's great 🙂 !
@ twinter : maybe the ones I linked in the german Audax shop site are not genuine ??? But they used to sell BG planars for a long time ! I know there are chinese conterfact on the markett as well !
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It's a DIY system, but I recall it used a pretty expensive JBL compression driver on the horn shown. The flanking mids are Eminence Beta 8A I think, with a plate-amp powered subwoofer in its own subenclosure below. The MTM section had such high sensitivity (around 100dB@1W/1m) that it used a 10W battery powered class A amp per side with a passive network before the amp as the crossover. It was executed very nicely and sounded very good. Here is a pic (it's on the left):
It's truly an honor to have a design of yours held up as an example from which to study.
Hey Charlie. Nice to see you here. While the comments you made are completely honest in their recitation, it's not just theory that makes the design but also how it performs in a real world situation . . . a room.
Nimbus resulted directly from our Stiff Breeze MTM: PE cabinet, dual WF152 fiberglass cone woofers offset to align with the RAAL 70-10D. In both designs we sacrificed a bit of CTC spacing for the option of implementing a 2nd order acoustic slope by aligning the acoustic centers. This is the exact same approach we took on the Nimbus baffle.
When we took the first pair to Newport a couple years back, we were concerned about how well Nimbus would work in a poorly treated hotel room. We took a room response measurement with pink noise as the source. The man who was performing the measurements confirmed my disbelief at seeing an almost textbook perfect room response with only a couple of bass modes at 80Hz and 40Hz. Here we were in a "typical" room, with supposedly improperly placed midranges with vertical lobing "issues" and yet the result was the best this particular measurement taker had seen in his many years of exhibiting at this show. Dumb luck? Sure, why not?
I guess the point I'm trying to make is that just because there are lobing issues well above and below the listening axis does not disqualify a particular arrangement of drivers. The dominant response is the on axis response. Your mind is most impacted by that response. Next is the off axis response and in that area the MTM performs very well with very wide horizontal dispersion and a smooth off axis response maintained with increasing angle. The vertical listening window is plenty wide enough to allow for a seated to standing change in angle and still have a reasonably smooth response.
But the overall power response has been shown to be quite good in real-world applications, design compromises and all.
Hey Charlie. Nice to see you here. While the comments you made are completely honest in their recitation, it's not just theory that makes the design but also how it performs in a real world situation . . . a room.
Nimbus resulted directly from our Stiff Breeze MTM: PE cabinet, dual WF152 fiberglass cone woofers offset to align with the RAAL 70-10D. In both designs we sacrificed a bit of CTC spacing for the option of implementing a 2nd order acoustic slope by aligning the acoustic centers. This is the exact same approach we took on the Nimbus baffle.
When we took the first pair to Newport a couple years back, we were concerned about how well Nimbus would work in a poorly treated hotel room. We took a room response measurement with pink noise as the source. The man who was performing the measurements confirmed my disbelief at seeing an almost textbook perfect room response with only a couple of bass modes at 80Hz and 40Hz. Here we were in a "typical" room, with supposedly improperly placed midranges with vertical lobing "issues" and yet the result was the best this particular measurement taker had seen in his many years of exhibiting at this show. Dumb luck? Sure, why not?
I guess the point I'm trying to make is that just because there are lobing issues well above and below the listening axis does not disqualify a particular arrangement of drivers. The dominant response is the on axis response. Your mind is most impacted by that response. Next is the off axis response and in that area the MTM performs very well with very wide horizontal dispersion and a smooth off axis response maintained with increasing angle. The vertical listening window is plenty wide enough to allow for a seated to standing change in angle and still have a reasonably smooth response.
But the overall power response has been shown to be quite good in real-world applications, design compromises and all.
Pete,
Thank you for joining! I've exchanged a couple e-mails with Ryan, trying to ask insightful questions while avoiding to ask about your intellectual property. He has been very good.
How does the choice of implementing 2nd order acoustic slope crossover affect spacing requirements?
In my design, crossovers will be active, digital, linear phase, and was planning to make them quite steep. The setup also allows for time alignment. How would that affect spacing in an MTM?
FWIW, my tweeter will be a TPL-150H, same you use on your Arcus, but crossed over at 2000 to 2500Hz instead of 1050Hz (Arcus). I noted you xo at 2500Hz on the Nimbus while the midrange drivers seem to be about 17" apart, well beyond the 5.3" wavelength at 2500Hz. The tradeoff you mention above must be why the midranges are not tugged as close as possible to the tweeter, which is what one would do to minimize C-to-C distance between the midranges. Clearly I'm missing a link between spacing and crossover slope.
I'm considering MTMWW and TMWW, where the M are likely going to end up being 5 or 6" for the MTM option or 6 to 8" for the TM option.
The link you're missing is that you refuse to use simulators to find
the answers. 🙂 LR2 acoustic slopes make a lesser hole in the
XO range when off-axis than the LR4, as if you had decreased the
c-t-c.
According to my calculations, the c-t-c distance of Nimbus midrange
units is about 13". Both of them, Pete and Charlie say what makes sense
and as with anything, the eyes are far more offended by the terrible
lobing/combing effects in mtm's than the ears/brains are. Maybe that
is the reason why extensive measurements are not presented in general.
It's true that the difference in spl of the said mtm is not that great between
the sitting and standing position, but only when the distance
from the sound source is great enough.
Hi Pete, didn't know that you were involved with the speaker. Great to have you join in the thread and I am interested in your thoughts and comments.
A question for you: do you have data/plots that show the off-axis responses for the MTM and the power response? I really would be surprised if there were not holes in the midrange off-axis response between 800Hz and 2kHz.
As an example I have attached a plot of the frequency response on and off axis (vertical direction) up to 30 degrees. This used two 7" midwoofers and a very small horn tweeter. I have shown the crossover point with a dashed vertical white line, and point out the holes off axis. Although there were some other issues with the directionality, the speaker sounded so flawed that I abandoned the project. The physical layout is similar in terms of C-to-C spacing and crossover point, so I would imagine that the Vapor Audio speaker has the same holes in its response. You just can't avoid the physics of the situation with this layout.
If you look at the plot, you can see that even in the vertical plane if you cross over low, say below 800Hz, you will still get a rather uniform pattern, since the two midwoofers have not yet started to beam at that point. If you added a small central midrange operating from 600-700Hz up through 3kHz and then crossed over to the ribbon I think you would REALLY have something great. Alternately, you could just slowly roll off one of the midranges starting around 500Hz. Just my 2 cents.
With any MTM, as long as you measure/listen in the horizontal plane that intersects the tweeter center the direct response will be great. That's the case with every well designed MTM. That was the case with my abandoned MTM system too. There is no response hole to be found there!
Also, it's possible to find a room that will compliment a particular loudspeaker's soundfield and power response, by luck or otherwise, so that the combination is perfectly balanced. But move that to another room and the result may be much worse with different room interactions. Might this explain your experience in the hotel room?
The conclusion that Toole reaches is that, for good sound in a wide range of room types/shapes/sizes with varying adsorptive/reflective properties, you need flat on axis and smooth off axis (e.g. no holes) response, with a smoothly varying power response. The original poster asked about opinions of the layout and driver spacing in the Nimbus, and I weighed in based on that work as well as other factors.
It's clear that the Nimbus uses very high quality drivers and if you are behind it then it has a very competent designer as well. But every speaker has its weaknesses, and I am just pointing out the ones that I perceive in the Nimbus.
Attachments
Haha! Fair enough. But please don't take ignorance for refusal 🙂
OK, which simulators should I look at?
I am absolutely sure that the vertical off axis plots of Nimbus will have that same look to them. My point is, "so what?" No one listens to them like that. Sure, that radiation pattern is then projected into the room becoming ambient reverb. But that's only one axis. The off axis horizontally is gorgeous, providing a very smooth response even up to 90 degrees off axis, like many MTM arrangements can do. The real world result in the room showed that even MTM 3-ways can offer beautifully flat in-room response with minimal room treatment. According to Steve Nugent, our room partner who took that measurement and who had also used and tested the TAD Reference 1, among others, as his show speakers, the Nimbus was even better at producing a flat in-room response than this well respected and theoretically advantaged system.
There is nothing wrong with MTMs exhibiting lobing off axis vertically. That's what two drivers will do when separated in space. And while there's a theoretical advantage to doing co-ax drivers like TAD does, you can still get great results doing it another way.
It's fine to be focused on an ideal. We have a speaker that performs as much like a point source as any two way on the planet. The Aurora uses a large waveguide on the tweeter to allow a 1000Hz crossover to woofer whose center is only 8.5" from the tweeter center. Its off axis performance (power response) is as close to ideal as anyone could hope for. But it's the Cirrus with its more traditional layout on a flat baffle that does a better job of imaging and just plain disappearing into the room. Drivers make a big difference which only magnifies the importance of the first arrival over the off axis ambient. I'm not saying that off axis isn't important, because it is. I've just built enough speakers to know that there's nothing inherently wrong with MTM layouts. They can sound fantastic, theory be damned. 😉
Allright, I'm ignorant as well, without the electronic aids.
A good allrounder is the Passive Crossover Designer and
other Jeff's speadsheets. You don't even have to
prepare realistic filters or frd's and zma's. Simply
create idealised impedance of straight 8 ohms and
FR of 90 dB, all the way 10Hz-20kHz and choose
a filter order, then hit the Initialize textbook values.
You can check the results with target transfer function.
Define the vertical offset of the drivers or any other
offset and change the listening distance along with
horizontal and vertical panning. Polarity plays a role too.
Have fun!
As a pure midrange driver (say above 400Hz) I would say I have heard better. The Audax Aerogel for example. Accuton had a nice 50mm midrange too (C50-44) as well. As a bass midrange it is better. I would put it on par with the Excel W15CY001 from Seas. There are slight differences of course with the WF152 winning some and the W15CY winning in other areas but we are splitting hairs here and our personal preferences and room correction will account for more.
I have not heard the B&W FST but for reasons I cant fathom I can clearly recall almost every driver/system I have heard from the 7N515/T120FC focal system in the 80s today.
I agree. I think as a midrange the Aerogel is more "there" aka dynamic.
I don't have access to measuring equipment so I use my ears and what's between them (and live music as a reference). I find that most MTMs I have heard have a tight but very small sweet spot. Now these are all 1" tweeters crossed over to some 5-6" mid. The goes way back to a MTM using Peerless TP165R and a KO10DT, then my own experiment using 18W8546 and the 9900, and others. I build for my ears, my room and my music and the MTMs I tried did not satisfy. Maybe I was doing something drastically wrong.
With a Fullrange does it make any difference to go MFM at say 300hz? One could just go MMF right? What are the advantages of a MFM over MMF at sub 300hz crossovers? Say we get 2 woofers with a power handling of 50W @ 50Hz can we get a small fullrange with a power handling of 100W @ 300hz? The FF85WK for example can barely take 10W. Any larger than 3" and HF response is limited.
In all your experiments with MTMs did you find the sweet spot being tighter but smaller than that with an MTM? I just want to know if anyone heard what I heard.
As long as the C-C of the furthest apart drivers is less thn 1/4 wavelength doesn't make much difference whether it is MTM or MMT.
I pay no attention to the power handling. The FF85wk FASTs we have built play pretty loud -- at least louder than i can listen to for an extended time.
dave
Hi ,
It can play loud but a PA driver will have a larger dynamic gap, a better dynamic headroom ( highest spl at Xmax) and a better damping due to the stronger motor (BL)?
Should we not design with the best dynamic and not the higher average volume with poor dynamic headroom? What is needeed according the todays recordings and the highest spl peaks, 120 dB spl (and we listen at 3 meters...) ?
It can play loud but a PA driver will have a larger dynamic gap, a better dynamic headroom ( highest spl at Xmax) and a better damping due to the stronger motor (BL)?
Should we not design with the best dynamic and not the higher average volume with poor dynamic headroom? What is needeed according the todays recordings and the highest spl peaks, 120 dB spl (and we listen at 3 meters...) ?
...So a 24 bits recording and Dac? (because the dynamic headroom and huger gap between Lowest and highest spl on the tracks?
From Post 34 I don't have access to measuring equipment so I use my ears and what's between them (and live music as a reference).
Before that:
Quote:
As a pure midrange driver (say above 400Hz) I would say I have heard better. The Audax Aerogel for example. Accuton had a nice 50mm midrange too (C50-44) as well. As a bass midrange it is better. I would put it on par with the Excel W15CY001 from Seas. There are slight differences of course with the WF152 winning some and the W15CY winning in other areas but we are splitting hairs here and our personal preferences and room correction will account for more.
Quote:
I agree. I think as a midrange the Aerogel is more "there" aka dynamic.
Sorry to be rude and for the rant below but: How on earth is it possible that you guys keep on commenting on how much better driver X is than driver Y without having he slightest clue to what you are actually listening to. You are not even comparing apples to oranges but apples to french fries or worse. Without proper measurements it is not possible to say anything at all about individual drivers that makes any sense.
Sorry to say, but such statements are completely worthless, and annoy me no end. This is the very same situation as blind people commenting on how loverly the grass looks.
Good Luck,
Eelco
Before that:
As a pure midrange driver (say above 400Hz) I would say I have heard better. The Audax Aerogel for example. Accuton had a nice 50mm midrange too (C50-44) as well. As a bass midrange it is better. I would put it on par with the Excel W15CY001 from Seas. There are slight differences of course with the WF152 winning some and the W15CY winning in other areas but we are splitting hairs here and our personal preferences and room correction will account for more.
Quote:
I agree. I think as a midrange the Aerogel is more "there" aka dynamic.
Sorry to be rude and for the rant below but: How on earth is it possible that you guys keep on commenting on how much better driver X is than driver Y without having he slightest clue to what you are actually listening to. You are not even comparing apples to oranges but apples to french fries or worse. Without proper measurements it is not possible to say anything at all about individual drivers that makes any sense.
Sorry to say, but such statements are completely worthless, and annoy me no end. This is the very same situation as blind people commenting on how loverly the grass looks.
Good Luck,
Eelco
Because for some we had already saw those grass and remember how it sounded...aerogel is différent than raw paper, wooden carbon, etc...of course there is T/S, load, filter....
i guess blind people can't appreciate that the grass exists on the basis that they can touch it to feel it's texture or smell it and know that there's dandelions in the patch.
long before measurements are introduced most people make subjective decisions about what they hear.
long before measurements are introduced most people make subjective decisions about what they hear.
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