@profiguy : I was ready to suggest a subwoofer built around the Ripole principle, because I personally have excellent results with this design in terms of transient, damping, deep bass extension, compactness, lightweight but... NOT in efficiency !
And then I read from you :
And so the Ripole is certainly to discard : it's intended for infra-bass, and also not for huge volumes that PA and/or HT may require, unless you use high power handling / efficiency / Xmax speakers !
A firend of mine - following my experiments - built a pair of 2x18" Ripoles with success, using SB Audience BIANCO 18SW450...
The efficiency is there, indeed - compared to my little 2x12" unit - but again : it's not really for PA and used in Infra-Bass (below 60Hz).
T
And then I read from you :
And so the Ripole is certainly to discard : it's intended for infra-bass, and also not for huge volumes that PA and/or HT may require, unless you use high power handling / efficiency / Xmax speakers !
A firend of mine - following my experiments - built a pair of 2x18" Ripoles with success, using SB Audience BIANCO 18SW450...
The efficiency is there, indeed - compared to my little 2x12" unit - but again : it's not really for PA and used in Infra-Bass (below 60Hz).
T
Have you ran any sims? JBL used an assisted alignment in both home for 2235's 2245's,B380,B460 subs with BX-63 and 2242's for cinema use. They would low tune to 26Hz and add a Q2 6 dB bump and use a 20Hz high pass. Worked well something to consider may or may not work with these drivers. I used it with Vertec 15's 2266's for HT subs and it worked quite well. Also did it with 2216's in my passive M2 set-up. Here take a look at the F3 numbers compared to a 32Hz box no assist.
That all the same box 26 Hz 26Hz assisted and 32 Hz. JBL also does this a little lower in the M2
Rob 🙂
That all the same box 26 Hz 26Hz assisted and 32 Hz. JBL also does this a little lower in the M2
Rob 🙂
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@Robh3606 No sims run yet. Just basic calculations with a piece of old code I wrote 30 yrs ago for vented and sealed alignments. You tend to get a good sense of what approximately works and what doesn't. Woofers with a mid to high 0.30s Qts are always of interest for vented alignments. Most pro LF drivers have a Qts of around 0.25 - 0.30 which is optimized for smaller vented boxes.
After running some 2268H sims, it's apparent it wants a box of equal or greater volumes than it's 338L VAS to provide much output at tunings below Fs.
The SLAPS M-12 passive radiator Fb is 20Hz in a 120L chamber, so can't take advantage of the larger chambers that provide more output with the 2268H at low tunings.
I usually avoid tuning under driver Fs. I can't give a technical explanation for it, but it never seems to sound that good. In addition to this observation, I notice that drivers with higher Qts (> 0.45) and lower BL (~ less than 10) tend to have rather sloppy/less defined lower bass in any Vb higher than the equivalent driver's Vas. Low BL and higher than usual Fs with extended shelf tuning and increased Vb makes this progressively worse.
Even though the sim in theory suggests the alignment would be ok on paper to tune under driver Fs, it just doesn't sound good. It acts like the driver has inadequate control when it needs to push all that air mass around without enough motor force.
Even higher tunings at lower Vb sound rather mushy, but not quite as bad as lower tuning in higher Vb. It acts as if the driver doesn't have enough motor strength to control the reactive air load well, especially with a higher QL enclosure loss factor.
I've often tried to figure out why my observations were as I described, but never found the physics behind it to back this up. My only explanation is driver BL not being high enough. Trying to increase enclosure dampening (higher QL) makes it alot worse, to the point it sounds like an infinite baffle rather than a large ported alignment. It apparently also affects the bass quality above the effective range of the port output as well.
All this is why I'm asking about the 2268H in regards to a more optimal alignment. I'm not looking to sacrifice lower midbass quality for more extension. The designs I heard the 2268H in have been in enclosures smaller than 10 cu ft (< 280 ltrs). In these instances the driver sounded clean and tight overall. While its not the most optimal driver for doing the lowest register well, it had some of the best overall balance in the whole region under 100 hz and even above that. A big plus is the spider doesn't have the typical resonances associated with lower compliance pro LF drivers. Most of the other affordable higher sensitivity LF drivers all show some kind of junk in the CSD, even though they appear more suitable for my needs.
Being able to play the lowest mids cleanly while going reasonably low is a major prerequisite for this project. I could have tried multiple smaller drivers with lower Fs, but they would have cost more and had lower sensitivity than the 2268H. Weight was also a factor, which rules out ceramic motor drivers, otherwise I would have reconsidered 2 of the SB34NRXLs, which are in my book still the best sounding LF drivers under $500.
Even though the sim in theory suggests the alignment would be ok on paper to tune under driver Fs, it just doesn't sound good. It acts like the driver has inadequate control when it needs to push all that air mass around without enough motor force.
Even higher tunings at lower Vb sound rather mushy, but not quite as bad as lower tuning in higher Vb. It acts as if the driver doesn't have enough motor strength to control the reactive air load well, especially with a higher QL enclosure loss factor.
I've often tried to figure out why my observations were as I described, but never found the physics behind it to back this up. My only explanation is driver BL not being high enough. Trying to increase enclosure dampening (higher QL) makes it alot worse, to the point it sounds like an infinite baffle rather than a large ported alignment. It apparently also affects the bass quality above the effective range of the port output as well.
All this is why I'm asking about the 2268H in regards to a more optimal alignment. I'm not looking to sacrifice lower midbass quality for more extension. The designs I heard the 2268H in have been in enclosures smaller than 10 cu ft (< 280 ltrs). In these instances the driver sounded clean and tight overall. While its not the most optimal driver for doing the lowest register well, it had some of the best overall balance in the whole region under 100 hz and even above that. A big plus is the spider doesn't have the typical resonances associated with lower compliance pro LF drivers. Most of the other affordable higher sensitivity LF drivers all show some kind of junk in the CSD, even though they appear more suitable for my needs.
Being able to play the lowest mids cleanly while going reasonably low is a major prerequisite for this project. I could have tried multiple smaller drivers with lower Fs, but they would have cost more and had lower sensitivity than the 2268H. Weight was also a factor, which rules out ceramic motor drivers, otherwise I would have reconsidered 2 of the SB34NRXLs, which are in my book still the best sounding LF drivers under $500.
Not sure what alignment you are discussing. In the assisted alignments I mentioned the port @ 26Hz is providing the output there is almost no cone motion at box Fb. As long you don't exceed the mechanical limits of the driver using the 20Hz high pass there is no issue at all with driver control.
Rob 🙂
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So maybe you don't like the sound of sealed boxes (vs typical vented boxes)? The lower the tuning, the more the box acts like a sealed box, as the driver damping is higher as you go lower in frequency below Fs.
@Robh3606 It's really just any alignment which pushes Fb under Fs. I usually look not to go considerably under Fs. The sweet spot is tuning between free air resonance Fs and the sealed box equivalent Fb - the same box volume in which the driver wants to naturally resonate when the ports are blocked. I don't prefer assisted alignments because the transient response always appears to suffer. I realize group delay becomes a problem with the lower tunings. Not sure how audible that is at specific tunings.
@YSDR I prefer the sealed box sound. Its more accurate by nature and just sounds better. It also avoids port midrange leakage when using the driver up into the lower midrange. Problem is F3 being too high at reasonable Qtc with the corresponding Vb.
@YSDR I prefer the sealed box sound. Its more accurate by nature and just sounds better. It also avoids port midrange leakage when using the driver up into the lower midrange. Problem is F3 being too high at reasonable Qtc with the corresponding Vb.
Then boost the low-end of the sealed box electronically and/or by speaker placement. Done.
But if that's true, I don't see why you don't like low tuned vented boxes. Of course, they are never equal, but a low-tuned vented box is more like a sealed box and you said you like higher tuned vented boxes more, which in turn tend to be very different from a typical sealed closed box.
@YSDR I dont like the sound of higher tuned vented boxes, especially when the higher tuning negatively affects the midbass and lower midrange clarity. I prefer textbook QB3 tunings at typical box loss (QL~7), which fall roughly in the middle ground between sealed and higher vented alignments. For me, QB3 alignments are a good compromise between less optimal vented and sealed boxes. It may have something to do with the closer balance between the two impedance peaks, but despite listening to all the expert opinions as to the difference between the alignments and their group delay curves, its more apparent that the time domain has alot to do with it. There's been extensive arguing how much group delay is audible and how it practically affects transient response.
I usually prefer aperiodic dampened enclosures for upper bass range but the lowest register is served best by some form of ported or TL style enclosure. The motor noise can be a major issue with smaller enclosures that excessively pressurize the back of the cone. The other problem is long term power compression and overall power handling. Distortion becomes very audible at greater cone excursion with smaller assisted sealed enclosures.
My project here will have to deal with some sort of a compromise for sake of practicality. I can live with a cutoff frequency of mid to lower 30s hz as long as the upper bass and lower mids will blend well. We can always seal the ports and EQ the cutoff to a lower point. I just wanted to ask around whether anyone has done anything different with this fancy balanced coil driver.
I usually prefer aperiodic dampened enclosures for upper bass range but the lowest register is served best by some form of ported or TL style enclosure. The motor noise can be a major issue with smaller enclosures that excessively pressurize the back of the cone. The other problem is long term power compression and overall power handling. Distortion becomes very audible at greater cone excursion with smaller assisted sealed enclosures.
My project here will have to deal with some sort of a compromise for sake of practicality. I can live with a cutoff frequency of mid to lower 30s hz as long as the upper bass and lower mids will blend well. We can always seal the ports and EQ the cutoff to a lower point. I just wanted to ask around whether anyone has done anything different with this fancy balanced coil driver.
Then check what JBL did with it or with a similar driver in their reference monitor M2. In the M2 Vb is about Vas (or maybe slightly larger), Fb is slightly below Fs, when the calculations is based on the classically measured T/S parameters. Of course, that's not guarantees to be satisfactory because you may not like the bass/midbass sound of the M2.
It's very similar to what I already posted. A bit more complicated with shelving but same idea of adding a bump at Fb. The bump a little above, not below as I had stated previously. Fb 27 Hz look at the Parametric filters and the high pass below to tailor below Fb
Rob 🙂
OK
It's a matter of preference. I think it depends on where this is happening at 26/27Hz I am not worried about transient response down there. Any added group delay occurs where EQ is added and at Fb so you do get a double whammy when you add assist. You can see this clearly in the sims I posted. I agree I am not sure if the added delay is even audible that low in your average listening room.
Rob 🙂
@YSDR @Robh3606 The JBL M2 was on my radar regarding the box tuning. They appear to get close to a QB3, just under it which creates a depression, pushing the port output lower. The depression needs EQ to make up for it. I did listen to some M2s and walked away feeling they sounded just a bit shy in the upper bass, giving the impression of looser transients in the lower mids. This is exactly what I want to avoid and I dont think you can fix the lower mids without dealing with the upper bass. It feels like its an inherent tradeoff.
The audibility of group delay is a heavily debated topic. I think it depends alot on how acute your analytical hearing skills are, being able to reference a real live instrument. Its definitely noticeable with instruments like piano, marimba and other percussive melodic instruments. With a piano, there are alot of things going on rhythmically with multiple attack envelopes going on all at once. It takes a fairly trained ear to notice this but its definitely audible.
As a good comparison, take the example of recording a large acoustic piano. This requires multiple mics placed in various locations at the inside, around the groups of strings of the harp. Timing issues are created this way and are extremely difficult (if not impossible) to fix, either by physical or electronical means. First off, you can't place multiple mics in the exact same physical location. It won't pick up all the different parts of the harp evenly. The attack transients won't reach every mic at the same time and will sound different at each mic location. The separate waveform events won't combine correctly and will each have different timing, tonal balance and timbre. No amount of EQ or delay on each mic will fix this. As an example, think of each individual piano mic here as a separate driver in a multi way speaker system with the mixing console acting as the crossover. Just EQing, delaying and mixing it all back together won't add up to a reasonably accurate sounding piano, regardless of how well you correct the phasing of each mic. Some critical reasons for this beyond your control are the structure born vibrations through the piano body arriving earlier at each mic before the sound does. This is due to the speed of sound being higher in the piano body than in air. There's also the issue of using different types/brands of mics, which all have different response curves (just like each driver in a multi way speaker).
So hopefully you can see why trying to fix timing issues in a speaker isn't just down to a matter of applying linear EQ. Its alot more complicated than that. I know alot of people say our ears aren't sensitive enough to notice smaller amounts of group delay, but some of us can perceive other hints which are buried in the more complex sounds of instruments when they don't sound right to us.
The audibility of group delay is a heavily debated topic. I think it depends alot on how acute your analytical hearing skills are, being able to reference a real live instrument. Its definitely noticeable with instruments like piano, marimba and other percussive melodic instruments. With a piano, there are alot of things going on rhythmically with multiple attack envelopes going on all at once. It takes a fairly trained ear to notice this but its definitely audible.
As a good comparison, take the example of recording a large acoustic piano. This requires multiple mics placed in various locations at the inside, around the groups of strings of the harp. Timing issues are created this way and are extremely difficult (if not impossible) to fix, either by physical or electronical means. First off, you can't place multiple mics in the exact same physical location. It won't pick up all the different parts of the harp evenly. The attack transients won't reach every mic at the same time and will sound different at each mic location. The separate waveform events won't combine correctly and will each have different timing, tonal balance and timbre. No amount of EQ or delay on each mic will fix this. As an example, think of each individual piano mic here as a separate driver in a multi way speaker system with the mixing console acting as the crossover. Just EQing, delaying and mixing it all back together won't add up to a reasonably accurate sounding piano, regardless of how well you correct the phasing of each mic. Some critical reasons for this beyond your control are the structure born vibrations through the piano body arriving earlier at each mic before the sound does. This is due to the speed of sound being higher in the piano body than in air. There's also the issue of using different types/brands of mics, which all have different response curves (just like each driver in a multi way speaker).
So hopefully you can see why trying to fix timing issues in a speaker isn't just down to a matter of applying linear EQ. Its alot more complicated than that. I know alot of people say our ears aren't sensitive enough to notice smaller amounts of group delay, but some of us can perceive other hints which are buried in the more complex sounds of instruments when they don't sound right to us.
My son just got the 2268H drivers in today and we did a quick TSP check. They are dead on spec without any noticeable shift testing the driver in warmed up state. They are not the prettiest looking driver, but theyre otherwise well made and very light weight. The cone is definitely their magic ingredient to their clean midrange. The HPL coating is the secret sauce.
Does anyone know the enclosure volume that this driver takes up? I’m just finalizing a 6 cuft 40 Hz enclosure and it seems good.
@ericbrooking Vd works out to be 6 ltrs according to my calculations.
What specs are you going with for your enclosures?
What specs are you going with for your enclosures?