Thank you. Can you share a little about the measurement conditions (on floor, baffle dimensions, etc)?
Would it be possible to take a measurement about 20cm from the center of the dome? If you have sound absorbing materials, they can create a barriers against reflections. Would be useful to see the distortion with less room interaction, and the -30dB waterfall response to 5 or 10ms.
Thank you. In addition to 1m frequency response measurements, I do 20cm and sometimes 2cm tests to get a clearer picture of the waterfall/CSD behavior and harmonic distortion. I use thick open cell foam panels arranged behind the to mic to absorb energy and reduce reflections. By no means do you have to take it to that point.
I’m away from my measurement setup at the moment, but I’ll try to post the REW settings I use to help filter out reflections while not smoothing over critical results.
I’m away from my measurement setup at the moment, but I’ll try to post the REW settings I use to help filter out reflections while not smoothing over critical results.
Thanks for the measurements.
103dB @ 1m is a big ask for any driver 6-7" driver.
I can tell you have issues with mounting/cabinet because the bunching up of all distortion products around 500Hz is an artifact.
Usually of something vibrating (cabinet, screw, fastener etc), in my experience.
Consider measuring at 31.6cm is also helpful because it is exactly 10dB louder than 1m, and thus you get higher signal to noise ratio than measuring at 1m. The downside is that you have to be careful not to overdrive your mic, which exhibits distortion of it's own but starts to get overdriven as you reach it's limits (you will see plenty of HD2/HD3 if this happens)
@HiFiCompass does some of the best measurements around; a good way to learn how to measure is to read Yevgeniy's website-
eg.
References:
https://hificompass.com/en/speakers/measurements/purifi/purifi-ptt65m08-nfa-01a
https://hificompass.com/en/speakers/measurements
under Measurement Setup Description (click to unfold)
103dB @ 1m is a big ask for any driver 6-7" driver.
I can tell you have issues with mounting/cabinet because the bunching up of all distortion products around 500Hz is an artifact.
Usually of something vibrating (cabinet, screw, fastener etc), in my experience.
Consider measuring at 31.6cm is also helpful because it is exactly 10dB louder than 1m, and thus you get higher signal to noise ratio than measuring at 1m. The downside is that you have to be careful not to overdrive your mic, which exhibits distortion of it's own but starts to get overdriven as you reach it's limits (you will see plenty of HD2/HD3 if this happens)
@HiFiCompass does some of the best measurements around; a good way to learn how to measure is to read Yevgeniy's website-
eg.
References:
https://hificompass.com/en/speakers/measurements/purifi/purifi-ptt65m08-nfa-01a
https://hificompass.com/en/speakers/measurements
under Measurement Setup Description (click to unfold)
This was more sloppy messy setup real quick to see how low it could go with excellent thd at 105db. I'm aware 500hz is absolutely the box here's a pic of the distrotion before I got some weather stripping but when I crank down the screws it leaks air so I'm kinda stuck in between. As a master furniture maker the box bring great shame to my family and you guys can't see it lol. I gotta build some built in desks maybe next week I can throw something together out of mdf that's nicer.
Attachments
so the big old peak at 1.2k is caused by reflections from inside the box some cheap acoustic foam arrived yesterday and i stuffed the cab to the limits and it destroyed the peak. So the peak in the datasheet is also just a reflection from the rear side. heres a waterfall at 1 inch with 4 inch of cheap foam behind it besfore i had 1 inch foam 4 inchs of wool.
Hi, do you know how datasheet measurement is done? it would be quite a coincidence if you had exactly same dimension enclosure as they had. While it is possible response around 1.2kHz is due to enclosure its more likely the only common thing with your and their measurement setup is the driver, which would suggest the peak is acoustic property of the driver itself. 142mm is half wavelength of 1.2kHz for example.
If damping straightens it out its not a problem though. Have you tried damping "inside" the driver?
Nah I'm in measurement mode havent listened to it. I don't think there's a driver on the market at this size that can do 115db/3ft with 1 percent thd ? 110db at 250hz 1 percent thd is pretty damn good too. This little guy can also go upto 120db from 250hz up which ended up being 1.5 percent thd.
So my box is 9"x14"x7" with a double baffle thickness that puts the inside at around 5.5" it's shallow so that's really not good for a mid anyways . I'm going to mess around with cardioid this coming week.
So my box is 9"x14"x7" with a double baffle thickness that puts the inside at around 5.5" it's shallow so that's really not good for a mid anyways . I'm going to mess around with cardioid this coming week.
What do you don't like with the distortion of the M74? Which driver is better?
Btw there IS a M142B, got a datasheet. Not sure if they have some on stock but the price I know is 3500,- per piece.
Well, the M74B-6’s distortion stood out as higher than I had expected below 1kHz. Above 1kHz it was excellent, but this is not a low-cost driver. With the advancements in production versus-cost, I had hoped it would bare performance similarities to the old thorns in the side of the audio business, Yamaha’s JA-0801 and 0802.
The M74B-6 had excellent distortion of -60-63dB at low levels above 1kHz, but below this, distortion rises over 20dB. At just 1W and 500Hz, it produced -45d and that just kept going higher as the level was increased. There could be grounds for debate on the audibility of such, but when a driver costs that much, I believe that isn’t state of the art performance. The JA-0801 was -70dB from 400 or 500Hz, and they are from the mid-seventies. They were quite astonishing in several areas.
Based on what is seen here, the M142A seems like a better choice over the M74B-6. Momomo67890’s distortion measurements look good considering the reflections, and the waterfall puts aside my concern of resonance in the 1-2kHz region caused by the dimensions. Stuffing appears to fix that issue. It will depend in the loudspeaker planning stage and I think more testing is warranted, but if I intended to high-pass at 300Hz-500Hz and low pass around 2-4kHz, the M142A seems more appealing than the M74B-6.
Do you have some measurements of the JA-0801? Never saw anything useful to this drivers. The ATC is also a very old design and still top.
The main benefit of the Bliesma is the small footprint, you can bring the tweeter really close. And it's easy to mount and you don't have any "waveguide" thing or mounting from the back etc. And the system implementation is not a little part of the deal ;-)
I just make measurements of the influence of the 3"s to the tweeter - would be interesting what the ATC is doing in this regard ... probably a reason where there are no such measurements ;-)
Here some more data (2x 3"! So 6dB louder as one). Don't forget - one M74B at 2,83V already gives you 97-98dBSpl! With an Accuton C90 you would need 9-10V to get that level - and it's a 5". Scan Speaks 3" about 6-8V, TangBand also. You have to compare THESE THD ratings or measure the Biesma at 1-1,5V.
THD is insanely low in the 700Hz-2kHz area but still better as your low frequency driver below
When you cross at 500Hz you already dampen at that frequency 3-6dB - so THD goes down further.
And it's only H2 - H3 is not rising at all and stays at -65dB at 500Hz.
So while of course you could whish for a better result - there is no driver I know (and you can buy) which is really better in this regard.
Hope I find time this week to compare the sound between M74A and M74B ...
The main benefit of the Bliesma is the small footprint, you can bring the tweeter really close. And it's easy to mount and you don't have any "waveguide" thing or mounting from the back etc. And the system implementation is not a little part of the deal ;-)
I just make measurements of the influence of the 3"s to the tweeter - would be interesting what the ATC is doing in this regard ... probably a reason where there are no such measurements ;-)
Here some more data (2x 3"! So 6dB louder as one). Don't forget - one M74B at 2,83V already gives you 97-98dBSpl! With an Accuton C90 you would need 9-10V to get that level - and it's a 5". Scan Speaks 3" about 6-8V, TangBand also. You have to compare THESE THD ratings or measure the Biesma at 1-1,5V.
THD is insanely low in the 700Hz-2kHz area but still better as your low frequency driver below
When you cross at 500Hz you already dampen at that frequency 3-6dB - so THD goes down further.
And it's only H2 - H3 is not rising at all and stays at -65dB at 500Hz.
So while of course you could whish for a better result - there is no driver I know (and you can buy) which is really better in this regard.
Hope I find time this week to compare the sound between M74A and M74B ...
I also don't see a significant improvement with Beryllium here - but dome resonance is insanely high. And easy to deal with.
I really find the backside frequency response interesting and would love to work on an inverted use of these drivers! Just a hole in the baffle and there is comming this incredible midrange out ... I'm sure we could make up great stories for selling in the highEnd market about that
But for my use the 3" BE is good and expensive enough ...