Hi all,
'til now I was designing a 3 way system with a Dayton PA460-8 'cause I'd like to go a bit "mad" with size and also this woofer would satisfy my weird needs with respect to freq. curve, low fs, sensitivity and power.
Recently I somehow stumbled upon the RCF LF21X451 and after having checked all of their other 18-21" drivers I chose this as the most promising monster into the room.
My intention is using 1 big bass driver with very high sensitivity, PA line if possible, good freq. curve and reasonably low fs despite being a normal woofer, not a sub-woofer.
So for your convenience here are the two: 21" RCF LF21X451 and 18" Dayton Audio PA460-8.
Price doesn't matter, they're supposed to serve me for the next 20 years just like my old woofers from my 19 years-old 3-way box I scrapped some days ago.
What I did 'til now:
- I put all Thiele-Small data into WinISD
- Voice coil inductance simulation ON (while it doesn't matter much due to low 1st crossover freq.)
- Low-pass filter 4th order Linkwitz-Riley @ 125Hz
- 430 liter / 15.185 ft^3 planned for the Daytons originally, kept volume for the RCF too
- Dayton tuned to fs=28.3Hz so RCF tuned to fs=28Hz
And I was looking like this when I saw the plot of both drivers:
They're almost 100% identical.
Apart from the max RMS sustainable power of the drivers (Dayton 500W, RCF 2000W) they seem to behave almost the same in the same volume box, tuned to their own fs values (which is also almost the same). At least on paper according to parameters.
As said, filter is a 4th order 24dB/octave steep slope Linkwitz-Riley (for now). Alternative option is the 150Hz but I'll begin with 125.
Box would be big and tall pyramid-like with no parallel walls at all. According to my original plans for the 18" Daytons even these 21" RCFs would fit into a bigger hole withouth changing the box itself (just re-tune the port on the back).
Any pro/contra for a 21" ? First of all it looks dignified and I want to "shock" my family/friend who come to visit me sometimes, on the other hand the parameters are okay at least according to WinISD.
Would you please have a look at their freq. curves ? The Dayton has some more smoothing in it, otherwise they're pretty much the same in this regard too, no big drama, nice rising curve with no huge peaks/dips - easy to plan with.
Max power will never be used, music performance is more important than home theater infra wave generation. I know they're hefty players for a low and moderate hi-fi listening but I just can't go smaller, sorry. My stupidity. 😉
Which one would you choose ? (Woodwork will start next month probably)..
'til now I was designing a 3 way system with a Dayton PA460-8 'cause I'd like to go a bit "mad" with size and also this woofer would satisfy my weird needs with respect to freq. curve, low fs, sensitivity and power.
Recently I somehow stumbled upon the RCF LF21X451 and after having checked all of their other 18-21" drivers I chose this as the most promising monster into the room.
My intention is using 1 big bass driver with very high sensitivity, PA line if possible, good freq. curve and reasonably low fs despite being a normal woofer, not a sub-woofer.
So for your convenience here are the two: 21" RCF LF21X451 and 18" Dayton Audio PA460-8.
Price doesn't matter, they're supposed to serve me for the next 20 years just like my old woofers from my 19 years-old 3-way box I scrapped some days ago.
What I did 'til now:
- I put all Thiele-Small data into WinISD
- Voice coil inductance simulation ON (while it doesn't matter much due to low 1st crossover freq.)
- Low-pass filter 4th order Linkwitz-Riley @ 125Hz
- 430 liter / 15.185 ft^3 planned for the Daytons originally, kept volume for the RCF too
- Dayton tuned to fs=28.3Hz so RCF tuned to fs=28Hz
And I was looking like this when I saw the plot of both drivers:
They're almost 100% identical.
Apart from the max RMS sustainable power of the drivers (Dayton 500W, RCF 2000W) they seem to behave almost the same in the same volume box, tuned to their own fs values (which is also almost the same). At least on paper according to parameters.
As said, filter is a 4th order 24dB/octave steep slope Linkwitz-Riley (for now). Alternative option is the 150Hz but I'll begin with 125.
Box would be big and tall pyramid-like with no parallel walls at all. According to my original plans for the 18" Daytons even these 21" RCFs would fit into a bigger hole withouth changing the box itself (just re-tune the port on the back).
Any pro/contra for a 21" ? First of all it looks dignified and I want to "shock" my family/friend who come to visit me sometimes, on the other hand the parameters are okay at least according to WinISD.
Would you please have a look at their freq. curves ? The Dayton has some more smoothing in it, otherwise they're pretty much the same in this regard too, no big drama, nice rising curve with no huge peaks/dips - easy to plan with.
Max power will never be used, music performance is more important than home theater infra wave generation. I know they're hefty players for a low and moderate hi-fi listening but I just can't go smaller, sorry. My stupidity. 😉
Which one would you choose ? (Woodwork will start next month probably)..
Hi, if you want to thrill more than just yourself, then multiple subs spread around the room will be Much better 🙂
So 4 smaller subs, of say 12" should suffice. Have a look for ones with specs similar to what you want, but around 300W - 500W
So 4 smaller subs, of say 12" should suffice. Have a look for ones with specs similar to what you want, but around 300W - 500W
How a driver behaves in a reflex cabinet (especially at the low end) comes mostly down to Fs, Qts and Vas. Both drivers have very similar values, so similar behaviour is to be expected (few 18" have a Vas that high).
It is as if you have 2 cars that both behave the same if you're using them mostly to go shopping in the city. One of your cars has a top speed of 100 km/h, the other one 290 km/h but if you're never going to go faster than 60 km/h, you won't reap much benefits from the latter.
I think 125 Hz is already a bit far fetched. I would look at 80 - 100 Hz as the maximum.
1. Because most 18" and 21" drivers don't sound well crossed that high.
2. Because you will be able to localise the bass
Johan
I'd like to stick to a 1-box concept (it will be 2 boxes but act as 1 in fact). Midrange and tweeter voice coil planes are aligned vertically to the bass driver's magnet so both of them will sit above the bass and a little bit "deeper" (towards the back) than the bass driver itself.
I also thought about the "mid-high stereo smaller boxes + 2 subs in the corner" option but don't want to try it for now, maybe in my next build. Interesting idea however. (It could only be done well if woofers are crossed no higher than ~80Hz to avoid directivitiy related things, see 1 comment before by Rademakers) - and my comment to him (just writing it now).. 😉
Some may prefer to have more radiating surface, others more excursion.
I would choose Sd.
True Bass in a Large Space: A Pro DIY Subwoofer Project from 1975! | audioXpress
I would choose Sd.
True Bass in a Large Space: A Pro DIY Subwoofer Project from 1975! | audioXpress
Hi Johan,
the example with the cars is very good.. thanks 😀 Made me laugh. 😀 Nevertheless, a Porsche 911 still looks better than a Citroen Xara Picasso, right ? (And yes, I'm going to shop at 50 km/h) 😎 It's about optics and crazyness, when I look onto the stereo setup it's like "whoaaaa I'm gonna drive these babies now f**k yeaaah" - and I double click on my Bach in Foobar2000 .. sit back .. and enjoy the power of the deep organ pipes.
- don't want to go deeper with midbass/midrange 'cause I'm closer to their fs then (~60Hz or so). With 125Hz and 4th order I avoid the resonance freq. and impedance peak of the midranges completely. 2 wins already.
- don't want to go higher with XO freq. 'cause I want Mark Knopfler to sing mainly from my midranges at chest and face-level, not from the floor coming from the big woofer. Looking at the Spectrum Analyzer 125Hz steep crossed is already acceptable for me to put male voices onto the midranges (most of them).
- couldn't find better midranges than these to go this deep, with deep fs (which I can avoid) while maintaining good off-axis directivity at the 2nd crossover point of 2kHz (don't want to drive tweeter lower), remaining flat most of the time and have a good sensibility. NONE.
- I don't want to go 4-way. I'm a little bit afraid of it despite using an electronic crossover and 6 dedicated small amps for the 3-way stereo sections. 8 amps would be insane. Or not, .. dunno. Sounds weird.
So I can't go lower than 125Hz with the woofers' XO point but due to filter slope steepness I still hope for a good sound. Woofer directional pattern is no issue, drivers will be aligned and facing the listener in a classic way: woofer on the bottom, then 4 midbasses on top of it and eachother, then tweeter.
I think for the main question I got my answer from you, however feel free to brainstorm/think about my plans and also feel free to keep on commenting on whatever comes to your mind.. I appreciate (this applies to everyone of course). 
the example with the cars is very good.. thanks 😀 Made me laugh. 😀 Nevertheless, a Porsche 911 still looks better than a Citroen Xara Picasso, right ? (And yes, I'm going to shop at 50 km/h) 😎 It's about optics and crazyness, when I look onto the stereo setup it's like "whoaaaa I'm gonna drive these babies now f**k yeaaah" - and I double click on my Bach in Foobar2000 .. sit back .. and enjoy the power of the deep organ pipes.
Can't go lower due to my midrange selection (midbass actually but I don't want to drive them lower, I spent DAYS with the selection of proper midranges for my needs here..).
I think 'til 200Hz we're still good, even with these ones. Freq. curve extends for the Dayton pretty much higher (and surprisingly flat) while the RCF clearly runs out of midranges earlier but I think you might be right despite the pure fact that they're capable of handling even 200Hz or so..
Well, again, you're right in the sense that I want to cross to midranges at 125Hz originally. I had to meet some compromises with this XO freq. selection:
- don't want to go deeper with midbass/midrange 'cause I'm closer to their fs then (~60Hz or so). With 125Hz and 4th order I avoid the resonance freq. and impedance peak of the midranges completely. 2 wins already.
- don't want to go higher with XO freq. 'cause I want Mark Knopfler to sing mainly from my midranges at chest and face-level, not from the floor coming from the big woofer. Looking at the Spectrum Analyzer 125Hz steep crossed is already acceptable for me to put male voices onto the midranges (most of them).
- couldn't find better midranges than these to go this deep, with deep fs (which I can avoid) while maintaining good off-axis directivity at the 2nd crossover point of 2kHz (don't want to drive tweeter lower), remaining flat most of the time and have a good sensibility. NONE.
I browsed through the WHOLE 2018 product catalog of Parts Express and some other stores, looking at EACH datasheet of almost EACH midbass/midrange driver and one or more of my requirements were failing, for cheap ones just the same way like for expensive ones, I went to manufacturer sites then and again looked at EACH midrange parameter, freq curves, etc. omg, this was hell of a struggle and finally I found this type which I'm going to employ, 4 pieces / side (no MTM with the tweeter).
- I don't want to go 4-way. I'm a little bit afraid of it despite using an electronic crossover and 6 dedicated small amps for the 3-way stereo sections. 8 amps would be insane. Or not, .. dunno. Sounds weird.
So I can't go lower than 125Hz with the woofers' XO point but due to filter slope steepness I still hope for a good sound. Woofer directional pattern is no issue, drivers will be aligned and facing the listener in a classic way: woofer on the bottom, then 4 midbasses on top of it and eachother, then tweeter.
I think for the main question I got my answer from you, however feel free to brainstorm/think about my plans and also feel free to keep on commenting on whatever comes to your mind.. I appreciate (this applies to everyone of course).
Also a valuable input for me .. considering. Thanks. I think the same now.. the Dayton is in danger. Well. Hmm.
Great article (and insane - 30" is omg).. but I think a today's 21" with 2000W RMS withstanding capability (instead of 60W) can produce some decibels too. 😉
With extreme excursions (like the Dayton Ultimax 18") comes a careful planning of port dimensions: air speed & port noise etc. should be kept in mind always. With a low Xmax driver it's also important but not that critical.
Somebody commented in one of my other topics also some "coloration" of the sound or "woofer noise" when we talked a bit about extreme excursions. That's why I don't really need, just another argument for high Sd.
- Status
- Not open for further replies.