I think the SB42FHCL75-6 may get overlooked sometimes because it comes from a company heavily associated with home hifi rather than pro-audio. If this same driver were offered by Failtal-Pro, JBL, Beyma, Eighteen-sounds... it might get more attention.
push pull slot load. The drivers are mounted in a manifold cone to magnet and operate like an accordion pushing the air out the end of the manifold. The opposing force cancels the drivers impact on the enclosure and cancels 2nd harmonics.
Hi Forum,
not knowing the exact room situation my advice is to go either for 3 way plus multiple subwoofers or 2 way plus +2 subwoofers
to be flexible with problems coming from room response you will need 2 subwoofers minimum with up to 4 to 6 subs to be really flexible in your room
a decent two way approach can be a 12 or 15 inch woofer with a 1.4 inch compression driver and a decent wooden horn or a pa plastic or alu horn modded to overcome the bell sound due to material resonances, there are tons of threads around for the topic
high efficiency is the best guarantee for low distortion up to load listening levels
with a room correction system like the Roon DSP convolution filters or Dirac it is nowadays easy to get a decent flat frequency response at your listening place
not knowing the exact room situation my advice is to go either for 3 way plus multiple subwoofers or 2 way plus +2 subwoofers
to be flexible with problems coming from room response you will need 2 subwoofers minimum with up to 4 to 6 subs to be really flexible in your room
a decent two way approach can be a 12 or 15 inch woofer with a 1.4 inch compression driver and a decent wooden horn or a pa plastic or alu horn modded to overcome the bell sound due to material resonances, there are tons of threads around for the topic
high efficiency is the best guarantee for low distortion up to load listening levels
with a room correction system like the Roon DSP convolution filters or Dirac it is nowadays easy to get a decent flat frequency response at your listening place
I have to apologize, I'm having trouble finding those measurements now too but there are a good amount of DIY commentary and projects to look though.
The data bass web site had extensive measurements on the 18N862 but they are inaccessible. here are some discussions. https://data-bass.ipbhost.com/search/?q=bms&quick=1 and https://data-bass.ipbhost.com/topic/310-bms-18n862-sealed-measurements-thread/
Voice coil has this one not the 18N862 https://audioxpress.com/article/Test-Bench-BMS-18S450-18-Pro-Sound-Subwoofer It still looks good and you can see the consistency and motor measurements but I like the n862.
AVS has extensive discussions. https://www.avsforum.com/search/516...&c[searchProfileName]=control-xsm&o=relevance
Bing turns up content by DIY users https://www.bing.com/search?q=BMS+1...F466460B816AB0B854620745&ghsh=0&ghacc=0&ghpl=
And of course http://www.troelsgravesen.dk/The-Loudspeaker.htm
Thanks Jim! I looked this driver more times but in my situation I would trade the very low Fs and high Xmax of this woofer for higher sensitivity/efficiency and lower Mms, that's why I asked for 25-30 Hz Fs. I haven't found this driver yet. On paper, Faital's new 12RS430 looks like what I'm thinking, but it's a 12-inch driver.
Data-bass /forums has/had a good amount of info available, driver testing and testing in enclosures, archive.org might let you dig up some that is gone.
Voice coil test Bench February 2012 has the BMS 18N862 with klippel data etc.
TAD 1601A . Ticks all your boxes. Difficult to find anything better, unless you are looking to drive them hard.
Fostex W400A / A2 series, Alnico, hard to source
Fostex FW405, original model. The newer 405N is impressive in its own way, but fails your qts sprc.
Look through JBL's catalogue, there will be a few candidates of earlier vintage.
I believe i have them save on the pc at home. Will look when i get back from work.
As mentioned above, Voice coil 2012 has the 18N862 measurements🙂
Here it is in the attachement, looks very good below 400 Hz, but that's just the harmonic distortion. I think IMD can be much more obtrusive than HD and for example an old TAD TL1603 in the JustDIYit test topped the BMS 15N850 and the 18Sound 15LW2400 too in this regard.
https://www.justdiyit.com/comparatif-15-pouces-pro/4/
I would for sure go with 2x 12" for a 3-way. Have a look here:
https://www.diyaudio.com/community/...rxl75-8-vs-sb29nrx75-6-vs-sb29nrx75-8.402671/
ScanSpeak 12" is also very good, THD should be on par.
M74 is a great mid driver and can be crossed over lower as some here think. My measurements are in the M74 thread.
Don't forget T25B as tweeter. Not sure if you get the maximum SPL you need but sound is very good at very high frequencies and vertical directivity is way better as every ribbon. For more SPL you could use T34B but I never built something with it, not sure about the Quality in the top octave. But for sure also better vertical as all the ribbons with their pretty long dimension their.
https://www.diyaudio.com/community/...rxl75-8-vs-sb29nrx75-6-vs-sb29nrx75-8.402671/
ScanSpeak 12" is also very good, THD should be on par.
M74 is a great mid driver and can be crossed over lower as some here think. My measurements are in the M74 thread.
Don't forget T25B as tweeter. Not sure if you get the maximum SPL you need but sound is very good at very high frequencies and vertical directivity is way better as every ribbon. For more SPL you could use T34B but I never built something with it, not sure about the Quality in the top octave. But for sure also better vertical as all the ribbons with their pretty long dimension their.
Btw - a classic studio woofer: https://www.beyma.com/en/products/c/low-mid-frequency/115LX60V28/altavoz-15lx60v2-8-oh/
Not sure if it goes deep enough in a closed volume - but Qms of >20 stands for a very low loss mechanical construction. (Beyma can do this, I measured one of their 8" with also crazy high Qms. Sounded also very good).
Not sure if it goes deep enough in a closed volume - but Qms of >20 stands for a very low loss mechanical construction. (Beyma can do this, I measured one of their 8" with also crazy high Qms. Sounded also very good).
But most of these woofers seem to be made to withstand a continuous 120dB in the mid-range, whereas the discussion seems to focus on maximum bass efficiency and a clean high quality mid-range.
Assuming about +/-1mm @ 2.83V, only a few 10s of watts will push most speakers past Xmax circa 20-50Hz. A woofer with a 7mm Xmax will ultimately only have a 6dB higher ceiling than one with 3.5mm, and unless the OP needs a massive power boost in the mid-range for some reason, a sub-200W woofer with a 1.5" - 2" diameter coil could be ample.
Assuming about +/-1mm @ 2.83V, only a few 10s of watts will push most speakers past Xmax circa 20-50Hz. A woofer with a 7mm Xmax will ultimately only have a 6dB higher ceiling than one with 3.5mm, and unless the OP needs a massive power boost in the mid-range for some reason, a sub-200W woofer with a 1.5" - 2" diameter coil could be ample.
@IamJF
I’ve wondered about this- whether we now have a better understanding what affect how it sounds. And help us advance our understanding of figures like Qms.
The historical T/S parameters developed and published over 50 years ago refers to Qms as the Driver’s Q at
2 x pi is a constant. So if a driver has higher Fs and Mms, and lower Rms, the higher the Qms.
Now these small signal parameters, typically measured in the fractions of a volt.
But when real music signals are applied, typically 0.283V to 28.3V (or even more), and they are dynamic, Wolfgang Klippel has shown that Cms (and this Rms) and Fs, can actually vary. It changes according on the cone’s excursion- both in the forward and backward movements, and is not always in a symmetrical manner.
so more accurately it is-
Fs(x)
Rms(x),
& Cms(x),
where x is the displacement of the voice coil from the rest position. And this is affected by now linear the surround AND spider are.
These are the “soft parts” or “suspension” of the speaker.
Does does this refine what we understand?
Perhaps this is the “low loss linear suspension” that was championed by Scan-Speak in the past.
Perhaps it’s Cms(x), Fs(x) and ultimately the linearity and symmetry of Qms(x) that can affect it it sounds.
@lrisbo
What are your thoughts Lars? Perhaps Sd(x) is far more important than Qms(x)…
How does optimisation of the spider further improve (or worsen) things?
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Volt RV3963? I've used the BM220.8 & BM2500.4 and they are superb.
https://voltloudspeakers.co.uk/speaker/rv3863-15inch/#
https://voltloudspeakers.co.uk/speaker/rv3863-15inch/#
That's not easy. As you say these values are by far no constants as TSP may delude. (btw Thiele and Small where totally aware of that. In fact everybody who measures TSPs knows that these are no precision values - more a linearisation at one point of the behaviour of a driver)
There is a good German DIY magazine ("Hobby HiFi") and the author says a low Rms shows low mechanical losses and gives fine detailed audio.
I think there is some truth in that. I searched for an 8" high sensitivity driver for my home cinema 8"/1" with as detailed reproduction as possible (cause I'm used to midrange domes). And Qms/Rms was something I monitored. The driver I use now has pretty high Qms.
Little story - I wanted to settle with Beyma 8P300, did listening tests and was happy. Had an older chassis from an other project to do these tests, ordered a few new ones and did the listening test again - and was not happy. Did all my measurements and detected they changed the rubber surround (it was Covid times) as their supplier couldn't provide or was closing doors. It was stiffer now. The chassis actually measured better around the resonance but THD goes up in the midrange. Still good. But Qms goes down and my impression was midrange was less "open" with less details. So I'm searching for low loss chassis now for my projects.
Here some measurements old vs new 8P300. Sorry for off topic but probably fits the High End theme in this thread? Old in Blue:
Easy to spot difference - that's just the rubber surround (distributor confirmed my suspicion after talking to Beyma)
Btw - I also asked a reputable monitor speaker company what they do about this cause they use this chassis in important models of their lineaup. They told me they use DSP anyways and calibrate each monitor ...
Attachments
What is certain on the other side is that chasing high QMS for the sake of it, makes little sense too.
You would automatically dismiss drivers with demodulation rings, shorting rings, copper sleeved poles etc.
Which is often desirable attributes if designed well.
This a way better analysis of it, that might get one to some conclusions.
The suspension losses are non-linear so reducing Rms may reduce distortion. Moreover, we believe that nearly all suspension elements exhibit hysteresis due to the stick/slip effects on the molecular level. On the other side, damping e.g. from the surround helps tame the frequency response peaks from breakups.@IamJF
I’ve wondered about this- whether we now have a better understanding what affect how it sounds. And help us advance our understanding of figures like Qms.
The historical T/S parameters developed and published over 50 years ago refers to Qms as the Driver’s Q at, considering driver nonelectrical losses only. Specifically, it was defined
2 x pi is a constant. So if a driver has higher Fs and Mms, and lower Rms, the higher the Qms.
Now these small signal parameters, typically measured in the fractions of a volt.
But when real music signals are applied, typically 0.283V to 28.3V (or even more), and they are dynamic, Wolfgang Klippel has shown that Cms (and this Rms) and Fs, can actually vary. It changes according on the cone’s excursion- both in the forward and backward movements, and is not always in a symmetrical manner.
so more accurately it is-
Fs(x)
Rms(x),
& Cms(x),
where x is the displacement of the voice coil from the rest position. And this is affected by now linear the surround AND spider are.
These are the “soft parts” or “suspension” of the speaker.
Does does this refine what we understand?
Perhaps this is the “low loss linear suspension” that was championed by Scan-Speak in the past.
Perhaps it’s Cms(x), Fs(x) and ultimately the linearity and symmetry of Qms(x) that can affect it it sounds.
@lrisbo
What are your thoughts Lars? Perhaps Sd(x) is far more important than Qms(x)…
How does optimisation of the spider further improve (or worsen) things?