I know it seems intuitive that a steady state signal would have less acceleration than dynamically changing signal. But it is not true. A cone/dome making steady state sinusoidal motion (playing a pure tone for instance), undergoes the full range of displacement, velocity, and acceleration each cycle. The louder the steady state tone, the more displacement, velocity, and acceleration.
Converting a measured impulse response to a calculated frequency response is not fiction. Nor is converting a measured swept frequency response to a calculated impulse response. If Fourier math did not work, none of our modern telecommunication systems would work.
... But it does seem like magic sometimes 🙂
j.
Your swept sine is low level signal only it does not account for peak values if you raise level your coil will be destroyed!
True music signal = waveform shape
check out oscilloscope or wave editor program like Audacity or Goldwave (both freeware)
good recordings have around 20dB dynamics that means the tweeter has to deal with 100W on transients assuming 1W average power at playback listening level ... real uncompressed music is even more demanding!
btw - I have some doubts about true beryllium used in todays hifi tweeters .. in days where Steve Mowry was in the biz Materion offered only an alloy called AlBeMet in various grades for deep drawing of domes (cheap method for mass production) ... on their website I see no mention how the manufacturing is done! (vapor deposition/CVD ?) And in the ads you see nowhere a "pure beryllium" statement ... and beneath that it makes not so much sense using Be if you support the dome with plain old fabrics (wide surround in case of the SB tweeters) that delivers the restoring spring force ... it is like you are loading a sports car on the back of an old lame mule and forget to fuel the car no wonder that it has no speed 🙂
regards from the old lame mule
True music signal = waveform shape
check out oscilloscope or wave editor program like Audacity or Goldwave (both freeware)
good recordings have around 20dB dynamics that means the tweeter has to deal with 100W on transients assuming 1W average power at playback listening level ... real uncompressed music is even more demanding!
btw - I have some doubts about true beryllium used in todays hifi tweeters .. in days where Steve Mowry was in the biz Materion offered only an alloy called AlBeMet in various grades for deep drawing of domes (cheap method for mass production) ... on their website I see no mention how the manufacturing is done! (vapor deposition/CVD ?) And in the ads you see nowhere a "pure beryllium" statement ... and beneath that it makes not so much sense using Be if you support the dome with plain old fabrics (wide surround in case of the SB tweeters) that delivers the restoring spring force ... it is like you are loading a sports car on the back of an old lame mule and forget to fuel the car no wonder that it has no speed 🙂
regards from the old lame mule
really you thinks all 10,25w class A or 30-50w ab in the world are broke ? in real world 10db are quite good
Absolutely love these domes and they are currently my dream midrange. A good alternative to the Volt VM752/3, easier spacing with the tweeter, four dome material choices with a shield to protect from little fingers.
I hope Bliesma keeps it up and releases a Super version with a lower Fs and a crossover range around 380-400hz like the ATC75-150s.
I hope Bliesma keeps it up and releases a Super version with a lower Fs and a crossover range around 380-400hz like the ATC75-150s.
It has been posted here or over on audioheritage before.
The vapour deposition method is done by TAD and a few others. They are more brittle with a higher hardness.
Also B&W 800 tweeters are CVD synthetic diamond. Bliesma idk.
While materion in general uses beryllium foil, the material is drawn through dies at xx temp to make the material less brittle and more flexible/harder to shatter, and easier to shape.
As for the exact alloy i got no clue either.
And with the increasing demand and volume use of CVD diamond for machinig purposes that's also a tech that has come a long way in recent years, and the audio market could take more advantage of it.
According to the HiFiCompass review "The confirmed low cutoff frequency for all models is 600 Hz with at least 2nd order filtering. It is possible that 500 Hz will be quite normal if you reduce the requirements for maximum SPL"
What are the limitations if going with an active 6th order or 8th order crossover?
What are the limitations if going with an active 6th order or 8th order crossover?
I have four Lambda SB10s that might work well if mated up in pairs to the M74B. The Lambdas aren't near as sensitive but they're very low in distortion and could be crossed over at 600Hz without too much worry and still carry the low end down to sub 30Hz. Not sure what else would work as well out there in woofer land.
Yes, these are. These were some of the last to be sent out by Nick before he closed up shop and sold off the line.
Do you know if there's any difference to the design now that AE produces the line?
No idea sorry, but if I were you, I'd message John at AE and ask. I bought Nick's second last set of Unitys back on '08.
I have 4 TD10M, 4 TD15X and 4 TD15S. I was contemplating a TD10M below the M74B and T25B with a big 18" pro driver under that. Probably all active. I have designs sketched, as well as one for the ATC SM75-150 I have and might use the new SB Be+WG or the good old SEAS H1499. There's enough drivers for both.
The 15's will go in other designs.
Brett - what are your thoughts on a crossover between the M74B and T25B? There is a broad overlap between the two drivers... Off hand, I would think the two drivers would be comfortable with anything from 2.2k up to 4k... I am curious what you think...
j.
j.
That broad overlap is actually good and provides flexibility to designer to experiment and come with well optimized crossover. I have worked with T25, its very wide dispersion causes very strong diffractions if baffle edges are not properly rounded, and it causes also directivity changes in 2-4kHz region, depending on baffle width. So the resulting crossover slopes and Fc will have to be compromise to balance all these effects.
If there are diffractions in tweeter response around 3k, Fc around 3k or higher could help to mitigate this, midrange will partially smooth it out and fill it in. Also LR2 often helps in that, though that would again require Fc >3kHz, T25 does not like low Fc with shallow slopes.
If there are diffractions in tweeter response around 3k, Fc around 3k or higher could help to mitigate this, midrange will partially smooth it out and fill it in. Also LR2 often helps in that, though that would again require Fc >3kHz, T25 does not like low Fc with shallow slopes.
Hi Jim,
As I don't have either driver on hand, and won't for a while, I have been musing over it. Whilst I trust Yevgeniy's measurements, I want to measure myself on my own baffle to decide where the tradeoff between directivity and distortion is. My OTTOMH guess is somewhere at the lower end of your spectrum, maybe 2k5.
As I don't have either driver on hand, and won't for a while, I have been musing over it. Whilst I trust Yevgeniy's measurements, I want to measure myself on my own baffle to decide where the tradeoff between directivity and distortion is. My OTTOMH guess is somewhere at the lower end of your spectrum, maybe 2k5.
I have done some preliminary directivity+diffraction simulations in VituixCad, and it seems that 2.5k 3rd order is acceptable. I was able to get both a rectangular and a trapezoidal baffle shape to work. As Pida points out, baffle size/shape is a very significant variable with wide dispersion tweeters such as this one.
Thanks for your thoughts....... j.
Thanks for your thoughts....... j.
I just did some measurements with the Bliesma M74 drivers and they are easily useable from 400Hz! THD is a little higher then in this area but depending on your listening leven that will never be a problem. And depending on your low frequency drivers it will probably still be lower at what the LF driver does ;-)
Here are some measurements from the prototype I built. That's far from the finished speaker but good enough to look at the possibilities with these drivers.
Measurement distance is 0,5m but level is corrected for 1m distance. Hypex DSP module as amp, upper filter is 4kHz. SB Acoustics 12" driver which performs incredibly good! But 110dB in 1m ... you need more as one 12" in a closed cab for that for low frequencies. And these measurements schow the M74A - which I prefer over the M74S after some listening tests.
THD at 100dBSpl. The peak at 600Hz is caused of a filter I set there - in reality it's 3dB lower (stays at 0,5%) with the 400Hz crossover. Just forgot to switch it of for these measurements ... happens when you perform hundreds a day ;-)
Even at 110dBSpl it stays <2% of THD and <1% over the most critical range.
And in this graph you see it's mainly k2 which is higher when you choose the lower crossover point. When drivers are on their limit k3 starts to raise rapidly - that's not the case here.
There is plenty more data but I don't want to spam this post. I will try to chose a crossover point at 450-500Hz for my design but would not hesitate to go lower for a living room speaker.
Here are some measurements from the prototype I built. That's far from the finished speaker but good enough to look at the possibilities with these drivers.
Measurement distance is 0,5m but level is corrected for 1m distance. Hypex DSP module as amp, upper filter is 4kHz. SB Acoustics 12" driver which performs incredibly good! But 110dB in 1m ... you need more as one 12" in a closed cab for that for low frequencies. And these measurements schow the M74A - which I prefer over the M74S after some listening tests.
THD at 100dBSpl. The peak at 600Hz is caused of a filter I set there - in reality it's 3dB lower (stays at 0,5%) with the 400Hz crossover. Just forgot to switch it of for these measurements ... happens when you perform hundreds a day ;-)
Even at 110dBSpl it stays <2% of THD and <1% over the most critical range.
And in this graph you see it's mainly k2 which is higher when you choose the lower crossover point. When drivers are on their limit k3 starts to raise rapidly - that's not the case here.
There is plenty more data but I don't want to spam this post. I will try to chose a crossover point at 450-500Hz for my design but would not hesitate to go lower for a living room speaker.
Attachments
Not really, I need to check more extreme situations for my use case. But there is a measurement at 94dBSpl in 0,5m - but these are 2 aluminium 3" drivers in MTM configuration and one 12" low frequency speaker. Cross over about 450Hz and 2kHz.
That would be about 82dBSpl from one mid driver in 1m distance.
That would be about 82dBSpl from one mid driver in 1m distance.