Well, that one is actually new to me.
Never seen it, never heard of it, almost everybody says to me it's wrong to design it like that.
.
With you/SB1001 I am not so sure about anything anymore. You are somewhat disproving my beliefs of standard practise in PA. That's why worldly forums are very useful. On the small local ponds it is just a local echo chamber. Not many different ideas.
I still don't get it. Could you please share with us your design - box volume and tuning frequency?
Driver: RCF LF18X451
Box: ported, 95l/3.55 cu.ft net volume without port.
Tuning: 28Hz.
Preset: HPF 35Hz Butt18db/oct, LPF 85Hz butt 18db/oct, PEQ1: 38Hz +2dB steep (Q3), PEQ2: 66Hz -2dB, wide (Q1).
In hornresp, this shows me 14mm of cone excursion at 120Volts (1800Watts). I have a suspicion that the excursion will be little less, but not by much.
The higher tuned design could dish out more SPL above 45Hz, but for high price of power compression below 45Hz, making it not flat sounding design. The F3 would go way higher than 34-35Hz.
Box: ported, 95l/3.55 cu.ft net volume without port.
Tuning: 28Hz.
Preset: HPF 35Hz Butt18db/oct, LPF 85Hz butt 18db/oct, PEQ1: 38Hz +2dB steep (Q3), PEQ2: 66Hz -2dB, wide (Q1).
In hornresp, this shows me 14mm of cone excursion at 120Volts (1800Watts). I have a suspicion that the excursion will be little less, but not by much.
The higher tuned design could dish out more SPL above 45Hz, but for high price of power compression below 45Hz, making it not flat sounding design. The F3 would go way higher than 34-35Hz.
95 l is oversized, not undersized enclosure volume for RCF LF18X451! Nothing wrong with that, but you are constantly talking about undersized volume!?
All conventional alignment for LF18X451 call for volume smaller than 95 l:
All conventional alignment for LF18X451 call for volume smaller than 95 l:
- SBB4: 70.6 l
- SQB4: 61.1 l
- SC4: 64.4 l
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Transfer function in sim
is just the old basic filter alignment.
Problem with sim most people assume to much.
Real world it depends on room, EQ
and if your mixing for live bands, DJ etc etc
Having done live mixing for bands
since the 90's.
Can tell you Bass players instantly whine
about the sub with typical cover bands.
We wind up the high pass and boosting
with EQ is minimal.
Anyways it is a low Qts woofer
so your Default alignments for reflex with such
low Qts
be either typical QB3 or BB4
BB4 will tune at Fs
QB3 which is fairly common and as you noted
yes will likely tune above Fs probably closer to 40 Hz
for typical system.
Since your aware of unloading and low tuning.
Then low Qts basically goes straight to BB4
since tuning is basically at Fs or lower than 3rd order
Its pointless to think what those do or dont do.
Its easy high tune unloads faster.
No need to woory about 2 or 3 dB of port
because EQ can be 6 to12 even 18 dB
till you bottom the thing out.
Its a nice woofer, nobody will run it at 1800 watts
But hey it has so much Xmax it will take a lot
of bass boosting.
Again nothing new, companies either horn load
or know they will get a small box with low Qts.
Only arm chair experts stare at graphs for hours.
Can probably make the box even smaller like 75 liters
it is what it is designed to do. As mentioned 95 liters
might actually be large to normal for low Qts.
is just the old basic filter alignment.
Problem with sim most people assume to much.
Real world it depends on room, EQ
and if your mixing for live bands, DJ etc etc
Having done live mixing for bands
since the 90's.
Can tell you Bass players instantly whine
about the sub with typical cover bands.
We wind up the high pass and boosting
with EQ is minimal.
Anyways it is a low Qts woofer
so your Default alignments for reflex with such
low Qts
be either typical QB3 or BB4
BB4 will tune at Fs
QB3 which is fairly common and as you noted
yes will likely tune above Fs probably closer to 40 Hz
for typical system.
Since your aware of unloading and low tuning.
Then low Qts basically goes straight to BB4
since tuning is basically at Fs or lower than 3rd order
Its pointless to think what those do or dont do.
Its easy high tune unloads faster.
No need to woory about 2 or 3 dB of port
because EQ can be 6 to12 even 18 dB
till you bottom the thing out.
Its a nice woofer, nobody will run it at 1800 watts
But hey it has so much Xmax it will take a lot
of bass boosting.
Again nothing new, companies either horn load
or know they will get a small box with low Qts.
Only arm chair experts stare at graphs for hours.
Can probably make the box even smaller like 75 liters
it is what it is designed to do. As mentioned 95 liters
might actually be large to normal for low Qts.
Keep in mind that reduced port output results in increased driver excursion. Perfect lossless resonator would lead to near zero excursion at resonance. Any resonator loss (e.g. small port) will increase driver excursion at resonance up to full excursion for a sealed box.
Heck there you go.
Sonce made a good point
and noticed it as well when you posted a link to
the driver.
It is well done driver actually.
We dream of woofers like this 25 years ago.
But id say most people be confused or misled
by the low Qts in sim.
It actually wont make much bass in transfer function.
So yes youd get the typical high tuners thinking it does
something useful.
As mentioned in my original comment.
This is why experienced builders go for a 18"
Same bass maybe even less than a 15"
We are shooting for low tuning so it can
actually take EQ.
Which is were all real bass comes from in real
world.
You just use the right alignment depending on Qts
and then done.
The real difference if it sounds mushy with EQ
or doesn't. Somewhat the downfall of sims.
To many pretty graphs to make wild assumptions.
Back in the day you made your own spreadsheet
enter the constants, and done.
You just had to know the actual theory.
No auto alignment. You just knew the relation to
Qts or possible efficiency bandwidth product and went for
3rd or 4th order. no graphs just a volume.
Sonce made a good point
and noticed it as well when you posted a link to
the driver.
It is well done driver actually.
We dream of woofers like this 25 years ago.
But id say most people be confused or misled
by the low Qts in sim.
It actually wont make much bass in transfer function.
So yes youd get the typical high tuners thinking it does
something useful.
As mentioned in my original comment.
This is why experienced builders go for a 18"
Same bass maybe even less than a 15"
We are shooting for low tuning so it can
actually take EQ.
Which is were all real bass comes from in real
world.
You just use the right alignment depending on Qts
and then done.
The real difference if it sounds mushy with EQ
or doesn't. Somewhat the downfall of sims.
To many pretty graphs to make wild assumptions.
Back in the day you made your own spreadsheet
enter the constants, and done.
You just had to know the actual theory.
No auto alignment. You just knew the relation to
Qts or possible efficiency bandwidth product and went for
3rd or 4th order. no graphs just a volume.
(@WhiteDragon)(not so much)
@Sonce
Oh no! I see. We are talking whole different realms here. Modern high motor force drivers are not to be used in conventional alignments really. That's simply wrongful usage due to the mechanical design of the driver and reasonable needs of the design.
Alignments do not work that well on these drivers anymore in exploiting their capabilities to the fullest.
Obviously, 60l box is incapable of creating lot of deep bass, it is restricting cone excursion and cooling, adding to the power compression.
This is not very useful approach to the driver anymore.
The approach is now seen like using hammer for everything. Not very sophisticated.
See, if you simulate lesser driver with weaker motor like B&C 18PS100 for example, it will give you much larger box volume. Now with enough amplifier and processing, there is no point in which switching driver for LF18X451 will give you less performance or will be worse in any concievable way. It doesn't make sense to replace driver, that has more excursion capabilities and pushes more Newtons per watt, to be considered worse performing or unfit. That approach is really outdated for current technology.
I am afraid that's the main reason we are not for one in this.
Go see B&C 15DS115 4ohm version. These standard alignments recommend between 6-30l of box volume , and hopefully you understand that such design is load of nonsense. If not, we might have some mess on our hands to solve here before approaching the original topic.
@Sonce
Oh no! I see. We are talking whole different realms here. Modern high motor force drivers are not to be used in conventional alignments really. That's simply wrongful usage due to the mechanical design of the driver and reasonable needs of the design.
Alignments do not work that well on these drivers anymore in exploiting their capabilities to the fullest.
Obviously, 60l box is incapable of creating lot of deep bass, it is restricting cone excursion and cooling, adding to the power compression.
This is not very useful approach to the driver anymore.
The approach is now seen like using hammer for everything. Not very sophisticated.
See, if you simulate lesser driver with weaker motor like B&C 18PS100 for example, it will give you much larger box volume. Now with enough amplifier and processing, there is no point in which switching driver for LF18X451 will give you less performance or will be worse in any concievable way. It doesn't make sense to replace driver, that has more excursion capabilities and pushes more Newtons per watt, to be considered worse performing or unfit. That approach is really outdated for current technology.
I am afraid that's the main reason we are not for one in this.
Go see B&C 15DS115 4ohm version. These standard alignments recommend between 6-30l of box volume , and hopefully you understand that such design is load of nonsense. If not, we might have some mess on our hands to solve here before approaching the original topic.
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That's taken account for. As the driver will be cut above port tuning, it will not get to full resonator usage, therefore no severe losses. Mind you, this has been tested in real life. It is just that it is not well documented by me, so with any claim, the ball is on my side to proof and explain. But If I had all cards and all data in my hands, we wouldn't be here discussing anything, would we...
Seems now your arguing in circles.
Your trying to support small enclosure and low tuning.
and when I agree after seeing the driver parameters
you then say im wrong LOL
Then you discovered a high pass filter above Fs.
Yup did that too, for likely well over a hundreds
maybe thousands of bands
If you wanted more bass in transfer function.
you wouldn't have started with a low Qts driver.
You dont seem to get it.
BB4 is a alignment invented almost 50 years ago lol
If the title of the thread was low Qts drivers
and why I love putting them in BB4
would have saved time.
Here is another amazing idea.
How about we take a low Qts driver
and make a " adjustable" port from QB3
to QB4 depending on application.
Hmmm EV also did that almost 50 years ago.
Problem is they didnt " make up" alignments
If we had a " weaker" motor back in the day
and it was low Qts. It would go straight to horn loading.
It is what they are designed for.
They went into small boxes because that is what people buy
when they need something small.
EV and everyone else was well aware of unloading and sound quality.
Why they made the ports adjustable for low tuning.
Your trying to support small enclosure and low tuning.
and when I agree after seeing the driver parameters
you then say im wrong LOL
Then you discovered a high pass filter above Fs.
Yup did that too, for likely well over a hundreds
maybe thousands of bands
If you wanted more bass in transfer function.
you wouldn't have started with a low Qts driver.
You dont seem to get it.
BB4 is a alignment invented almost 50 years ago lol
If the title of the thread was low Qts drivers
and why I love putting them in BB4
would have saved time.
Here is another amazing idea.
How about we take a low Qts driver
and make a " adjustable" port from QB3
to QB4 depending on application.
Hmmm EV also did that almost 50 years ago.
Problem is they didnt " make up" alignments
If we had a " weaker" motor back in the day
and it was low Qts. It would go straight to horn loading.
It is what they are designed for.
They went into small boxes because that is what people buy
when they need something small.
EV and everyone else was well aware of unloading and sound quality.
Why they made the ports adjustable for low tuning.
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Ahaha yes! I see. It can be seen this way indeed! It´s because I come from the place where the alignment recommendations for such drivers are complete bollocks, ignoring vital driver properties and bass output possibilities. Well utilized 18" driver should be placed in 130-160l box, and anything less is unconventionally small.
This! It seems to me, that everyone is standing on that approach as on some dogma. I felt you know better, but in the discussion, it was not so obvious.
Basically, I ignore all concerns and issues raised by low Qts driver, as it is unconsequential. Low Qts driver basically means it is more damped, and that it is likely to push more Newtons per watt. At no point it does make sense to me, to strive for weaker driver. Displacement and motor force are main factors in decision.
BUT, stronger motor force driver has no good reason to be stuck in the smaller enclosure in certain design in mind. It CAN, and the sims show that the driver would still be able to somewhat work there, but it is not a rule to be followed strictly. The driver can stay in the large enclosure, and do some "big work".
I get it. In discussions it seems other people don´t get it. But now it seems we all are getting it, but We (I) are uncapable of communicating that properly.
What I ´m saying is, that these alignments do not support physical properties of the modern drivers fully. There is a good reasoning in doing things differently, and not following these alignments.
Oh crap. It is the same thing, but I´m coming from different place. It is somewhat accidental. See, if we benchmark this claim, and imagine driver with Qts of 0.1, we would not have this discussion, because ignoring the ridiculousness, I would not be talking about two litres box. I would still be talking about undersied 95l box. by certain measures, it IS undersized still. That´s why we have so much misunderstanding. It´s all unconsequential, just accidentally related. And as we know, relation does not equal to causation.
I was thinking about adjustable ports. Not very feasible. Maybe, just maybe, two ports, and one being able to be blocked. I could get back to such approach.
I see the latter part as a limited approach.
My choice process is to get lowest Qts driver possible with greatest cone displacement volume possible for money a mortal can pay, and exploit its capabilities given the needs. Alignment utterly completely irrelevant. It just can so happen to be one of these, but it might not. I do not need you to agree with my perspective, but it somehow still seem that people don´t see it fully.
Low Qts drivers are not to be dogmatically stuck in smaller enclosures. It´s wrong view of the transducer design.
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Nobody want that. Extended Bass Shelf (bigger volume than conventional alignment, low tuning) for low Qts drivers was invented many, many years ago:
In actual use, low Qts driver will get increased Qes (by heating from high wattage), so bigger volume actually will end up in a bog-standard conventional alignment.
We are getting to it, wow!. Bunch of very good people here actually. Sorry for underestimating anyone. My bad, sorry.
Well, the conventional alignment is so much off, that even bigger volume than conventional by EBS alignment is still too small for the driver capabilities to be exploited fully at times.
I guess we could communicate that practically. I might do some homework and present the approach. Let´s say we want to get most SPL at 40Hz from B&C Speakers 15DS115-4, while staying within the limits of power input and cone excursion, while maintaining flat frequency response after EQ and processing.
EBS alignment seem to not work well for such task. It offers 30l of enclosure volume, and higher tuning. If we use 60l and sub 40Hz tuning, we seem to extract this kind of performance from the driver easily. So the alignment approach fails you on out way to the goal. That´s the whole issue.
//To finish the thought here:
If we choose much weaker driver, the alignemnt allows us to tune for 40Hz and extract 40Hz performance from the driver. Now we switch for more capable driver with more displacement volume and stronger motor, and all of the sudden, it is not possible? That's where alignments fail us big time. And the thing is that such design will beat all conventional designs in such volume.
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Basically, for simplicity EV just used a removable plate to partially cover a slot port for TL606 and others.
Called it stepdown mode. fB 55 Hz and 40 Hz in step down mode.
55 Hz for basic music playback / midbass 40 Hz step down for bass guitar or low frequency applications.
Yes F3 is actually higher in stepdown cause people dont understand unloading staring at graphs in sim.
Specifically praised by me and people that actually make speakers. It is noted real f3 is lower and does not unload
as fast in stepdown when you use EQ hence where real bass comes from. Not high tuned nonsense.
Was noted in TL606 manual 63 Hz f3 with 55Hz port and no EQ is too be used. f3 in stepdown with EQ 40 Hz
Least you understand low tuning and dont high tune like most do for " more bass"
Aside from poor efficiency and error factors to calculate slot ports.
Yes could make plates to cover flared round ports. Better choice or ideal choice for
velocity ramp AKA port.
Since you like large drivers like 18" or 21"
With typical old school 3 to 6mm xmax drivers with simple spiders
not like reinforced spiders like today.
Large drivers at high power would start cone rocking
specially uneven pressure from single ports increased the likely hood.
For large drivers like 18" was recommended to have equal pressure ports
or 4 even spaced ports one in each corner to reduce cone rocking.
So ideal port blocking system would be actually 6 ports even both sides.
If 2 ports were blocked in middle tuning would be lowered. But there would still be 4
open ports. One in each corner for more equal pressure less cone rocking even with port stepdown blocking.
Less a issue with modern 1800 watt drivers with heavier spiders.
But still very helpful at high power and less likely to cone rock regardless
with equal pressure porting
https://www.rcf.it/en/products/product-detail/lf18x451
I saw your comment and got happy that I found the big bass ina small box driver but then saw the 220L Vas. You can place a 220L Vas driver in a 75L?
@Randy Bassinga: Vas is a speaker parameter, not a need.
From mechanical point of view, it might be optimal for the air spring to be close to equal of the speaker compliance, but quite many modern transducers have so powerful motor, that they basically don´t give a damn what air spring is behind the cone. Yes the speaker´s behavior gets altered by it, but no longer this airspring can dictate speaker performance strongly enough that the speaker designer would take it into consideration as heavily as in past.
Extremely crudely said, The same way as we don´t match other parameters as speaker weight with box weight, we don´t match speaker compliance with box compliance anymore. Because matching the compliances does not bring us best overall performance anymore.
From mechanical point of view, it might be optimal for the air spring to be close to equal of the speaker compliance, but quite many modern transducers have so powerful motor, that they basically don´t give a damn what air spring is behind the cone. Yes the speaker´s behavior gets altered by it, but no longer this airspring can dictate speaker performance strongly enough that the speaker designer would take it into consideration as heavily as in past.
Extremely crudely said, The same way as we don´t match other parameters as speaker weight with box weight, we don´t match speaker compliance with box compliance anymore. Because matching the compliances does not bring us best overall performance anymore.
@WhiteDragon
Clever design for the time. I´m wondering if there is a reason to do that if the speaker would have the cone displacement volume needed. Maybe that situation would make this design redundant, and it seems we are barely getting there
I´m super glad that technology allowed modern speakers to bypass many of these issues.
Clever design for the time. I´m wondering if there is a reason to do that if the speaker would have the cone displacement volume needed. Maybe that situation would make this design redundant, and it seems we are barely getting there
It´s not for nothing. If one runs of speaker cone displacement, one needs to make terrible and desperate compromises. Have some consideration and pitty for these. 🙂
I´m super glad that technology allowed modern speakers to bypass many of these issues.
As Sonce said, the B&C18SW115 is almost identical in response to the RCF LF18X451.
It does require slightly more voltage to hit it's Xmax of 14mm compared to the RCF Xmax of 13.5mm.
Your HP filter puts electrical response -3dB at 35Hz, so basically your cabinet low corner after EQ is around flat to 40Hz.
I'm not following your power compression theory, raising the Fb from 28 to 36Hz in the same size cabinet increases output by +3dB at 40Hz and reduces excursion.
Using the HPF 35Hz BW18 filter, the higher tuning would require less low end boost to reach flat response, and the higher sensitivity would reduce power compression.
Just for fun, did a comparison of the RCF LF18X451 in a tapped horn of double the size of the 28Hz FB. it has +6dB output at ~40Hz.
It would put out the similar LF as two of the BR cabinets using half the power and drivers.
Art
@weltersys
These similarities only stay so close with small signal. Not so in large signal. While I have the feeling that (exactly belowed by me) 18SW115 would hold its own, there are differences. LF18X451 does push more air through the motor, or at least it sounds like it. it has the same coil as LF21X451, which is rated at 2000W, and in my bench test I do to my drivers, it only ate 120VA to get past Xmax. Very little power spent on suspension. When tested 21DS115 against LF21N551, the 21DS115 ate more than double compared to 551 to get there, and at same power, LF21N551 went to 21mm no issue. So in real use, the LF21N551 obviously was less strained and heated by suspension losses. B&C speaker drivers cones are braked sooner. Soon enough to creep into the real world usage. In usage, I did not know that back then, and indeed, I smelled the coil of 21DS115 altgough it wasn´t supposed to be power limited in my design. Simulators will not show you that. I call this "experience payed by wallet".
The sensitivity and efficiency is not the same thing, and that´s where I do believe you are mistaken.
This claim is exactly wrong. Because, if you are working around bassreflex port tuning, you are working around lowest impedance (valley).
It means a lot of power going to the driver, and little cooling for the driver, because it does move very little in the tuning frequency.
It is more sensitive, but very badly efficient. Power burns on the coil like mad. When you apply power compression simulation to it, you fall way down with the output of the speaker, even below my design. We might go step by step in the sims with it to see what´s going on, where is my reasoning and why crude sims without further investigation are misleading or not true, and certainly terribly insufficient.
For the tapped horn thingie - does the design have enough excursion capabilities to hold nearly flat above 40Hz?
What about input power? I have good reasons to think we´d fall good 4dB down if not more in real life.
Now, I do get that bigger enclosure or TH would utilize the driver a lot more, but NO WAY it would outdo two drivers in same volume that are avoiding power compression like plague. Quite few TH people have their noses too high up, lacking some less than basic knowledge. The hype is quite strong and agressive, to a point of sincere discussion not possible.
I owned 18SW115 before, very respectable driver. Now I have LF18X451, and these are very similar in some ways indeed. The approach in construction is different thouh.
These similarities only stay so close with small signal. Not so in large signal. While I have the feeling that (exactly belowed by me) 18SW115 would hold its own, there are differences. LF18X451 does push more air through the motor, or at least it sounds like it. it has the same coil as LF21X451, which is rated at 2000W, and in my bench test I do to my drivers, it only ate 120VA to get past Xmax. Very little power spent on suspension. When tested 21DS115 against LF21N551, the 21DS115 ate more than double compared to 551 to get there, and at same power, LF21N551 went to 21mm no issue. So in real use, the LF21N551 obviously was less strained and heated by suspension losses. B&C speaker drivers cones are braked sooner. Soon enough to creep into the real world usage. In usage, I did not know that back then, and indeed, I smelled the coil of 21DS115 altgough it wasn´t supposed to be power limited in my design. Simulators will not show you that. I call this "experience payed by wallet".
The sensitivity and efficiency is not the same thing, and that´s where I do believe you are mistaken.
This claim is exactly wrong. Because, if you are working around bassreflex port tuning, you are working around lowest impedance (valley).
It means a lot of power going to the driver, and little cooling for the driver, because it does move very little in the tuning frequency.
It is more sensitive, but very badly efficient. Power burns on the coil like mad. When you apply power compression simulation to it, you fall way down with the output of the speaker, even below my design. We might go step by step in the sims with it to see what´s going on, where is my reasoning and why crude sims without further investigation are misleading or not true, and certainly terribly insufficient.
For the tapped horn thingie - does the design have enough excursion capabilities to hold nearly flat above 40Hz?
What about input power? I have good reasons to think we´d fall good 4dB down if not more in real life.
Now, I do get that bigger enclosure or TH would utilize the driver a lot more, but NO WAY it would outdo two drivers in same volume that are avoiding power compression like plague. Quite few TH people have their noses too high up, lacking some less than basic knowledge. The hype is quite strong and agressive, to a point of sincere discussion not possible.
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Yeah isn't the trick to lower the upper impedance peak where most of music meat is, somewhere 40-60Hz for good cooling and low current (high voltage) power. Impedance minima now so low in frequency there is not that much content to heat the system.