As a general rule, for sealed box applications, I would look for woofers with a Qts value of 0.35 or higher. With proper EQ, you have some flexibility on cabinet size and bass extension, but if the Qts value is too low, it becomes really difficult to get any performance from a sealed box.
To get down to 50 Hz, I would also choose a woofer with an Fs of no higher than 32 Hz, and lower is better.
To get down to 50 Hz, I would also choose a woofer with an Fs of no higher than 32 Hz, and lower is better.
Yes, quite unfortunately, even when a driver is suited for a sealed box, a "forced" bass reflex using the same driver (if feasible at all) may show lesser excursion and lesser amplifier power for the same SPL.
@JukkaM
Have a look at this:
http://redspade-audio.blogspot.com/2011/03/efficiency-bandwidth-product-ebp.html
Have a look at this:
http://redspade-audio.blogspot.com/2011/03/efficiency-bandwidth-product-ebp.html
This is true. Bass drivers seem to be almost universally optimized for ported enclosures. 8~12" woofers with super low resonance (say 18~22 Hz), higher Qts (0.5?) and modest Vas (60-100 liters?) which are best for deep bass. Say F3=45Hz or lower with 0.7 system Q; ideally to 30Hz or better ) in sealed enclosures are quite hard to find.
This might be off-topic but not very, mehopes:
I have a preference for sealed box bass, especially for friends who don't want speakers that have to placed 2-4' away from the wall. I would love to see a recommended short list of 7~15" woofers for sealed boxes. I bet I and JukkaM are not the only ones.
Surely the combined knowledge of the diyaudio community could come up with a good list?
A couple of quick votes (using https://www.diyaudioandvideo.com/Calculator/SpeakerBoxEnclosure/ for quick 3-parameter 0.7 system Q check):
SBA 8″ SB23MFCL45-8 / Polypropylene -- 27.5Hz, 0.43Qts, 37L -- F3=46Hz in 22L box
SBA 12″ SB34SWPL76-4 / Paper -- 19Hz, 0.32Qts, 79L -- F3=42Hz in 20L box (Obviously great for deeper bass in bigger box & easily DSP EQ'ed)
I used OB/IB woofers ~like these, though none had much Xmax,just a reasonable amount of Xlim and when super high Qt, in slightly lossy boxes.
You can try a different approach: build it as a bass reflex box (which will give you lower distortion at the low end and extended LF response) and then EQ it back to fit the shape of a sealed transfer function. You will get the same group delay as the equivalent sealed box.
I did some comparison, mainly for the 15" drivers that I could find from various manufacturers. Anyone is welcomed to look at the spreadsheet: https://docs.google.com/spreadsheets/d/1j6zhuPLrkmy5BYwkw08kY4JQOFrmD7NoLjRpr1ccPhk/edit?usp=sharing
There are some formulas and color codes for a few things.
I went for the Eighteen sound 15ND930, 16 Ohms version, and put it into a ~78 liter, heavily damped closed box. I selected the driver for better fitting to closed box and for the looks. I'm not sure if any other driver would have been significantly better, my simulations stated, that they all perform more or less the same when equalized for the FR. I'm not disappointed. My goal was to make a proper bassleg for my mains and aid with subs. These 15" extend well up to xo at 200 Hz (and beyond) and at the same time outperform my previous 14" subs. So all in all I got what I wanted and more. For home use, but I did host a party in a gymnastics hall, and limits of the speakers were not reached 😀
There are some formulas and color codes for a few things.
I went for the Eighteen sound 15ND930, 16 Ohms version, and put it into a ~78 liter, heavily damped closed box. I selected the driver for better fitting to closed box and for the looks. I'm not sure if any other driver would have been significantly better, my simulations stated, that they all perform more or less the same when equalized for the FR. I'm not disappointed. My goal was to make a proper bassleg for my mains and aid with subs. These 15" extend well up to xo at 200 Hz (and beyond) and at the same time outperform my previous 14" subs. So all in all I got what I wanted and more. For home use, but I did host a party in a gymnastics hall, and limits of the speakers were not reached 😀
I'm not confident it's that easy. When you go below the port tuning frequency, ported response drops like a stone and woofer motion becomes different. Also you need careful execution of port placing and damping to avoid unwanted side effects. And generally you need larger box than with sealed. If I was doing it again, I'd still rather go with a large sealed than ported.
IIRC you can port tune these woofers < 25 Hz, but you need a multi-hundred-liter box, which was a clear nogo for my application. "Hifi" woofers may have lower Fs, but can't handle much power or excursion. Sd is a clear winner in my opinion.
Yeah, manually, so that I could identify good specs when they come by and not just copy-paste blindly. There are other databases online, but with limited search or outdated drivers. I thought to myself "there can't be to many"... Turns out manufacturers have more 15" drivers than 8 and 10 combined lol 😅
Rather than do it manually, sometimes to make a shortlist of suitable drivers, consider using Speakboxlite.
https://speakerboxlite.com/subwoofers/subwoofer-choice
Choose your desired 1) cabinet volume, eg. 50L, 2) choose your cabinet eg. sealed, and 3) choose your desired alignment eg. maximally flat.
And it will spit out a shortlist of drivers and their respective anechoic F3.
Unfortunately the website has some ads. The app is better IMHO, because you can shortlist your manufacturers and driver sizes after step 3.
https://speakerboxlite.com/subwoofers/subwoofer-choice
Choose your desired 1) cabinet volume, eg. 50L, 2) choose your cabinet eg. sealed, and 3) choose your desired alignment eg. maximally flat.
And it will spit out a shortlist of drivers and their respective anechoic F3.
Unfortunately the website has some ads. The app is better IMHO, because you can shortlist your manufacturers and driver sizes after step 3.
That's a prime example why I made my own list. Limited search functions and not up to date with latest drivers (still from years ago). I tried it and it gives me mostly car drivers, most of which are from brands that I have never heard from before. On top that the site is difficult to use for comparing data.