I haven't posted any details, but the magnet structure of the 18XL1800 makes it pretty straightforward. All I did was cut a few donuts from MDF, stack them, and then position that stack on the back wall of the enclosure (which has a matching hole cut). Add some foam gasket to the top of the donut stack, and that seals against the backplate of the driver.
There's a 3" long tunnel of approx 2" diameter for the air to travel through, so it can be exchanged with the outside world.
I suspect there's a small output penality, since I've effectively introduced a leak**, but I haven't measured this yet. There doesn't seem to be any noticeable difference between the prototype cabinet (no tunnel) and the final versions.
**NB - the "leak" forces air through the motor structure before it can exit the cabinet via the pole vent.
I'd like to try these drivers in a big ol' ported box to see what they can really do, but the small sealed boxes let me run down to infrasonic for special effects. Good fun.
Chris
I built an 18" ported for a customer, and even using a top-of-the-range B&C neo driver, I preferred the sound of my little sealed subs by a long margin.
The ported was scarily efficient though...
Yes +70 cm long port´s is a big problem by it self ( if tuned to 21 hz)
And it not that much that i "want" small boxes, it´s more about i want them not to wide and to be possible to place "in normal" room´s.
As they are now "the front" is 62 cm wide, and it is not particularly beautiful or placement-friendly.
And if i have them play sideway´s it´s still 55 cm wide, so still not "beautiful or placement-friendly"
When i test these hard in my "big" room ( 50 m2) in the basement 3-4 years ago, the grills flew off.
& I sensed the port was "working hard", but the cone wasn't moving much.
Had 2 of them connected in parallel so 4 ohm´s load, and tested with a Crown XTI 6002 and also with my Krell F.B.I
Regards John
I understand you!
So far I have the same experiences, and Im almost sertain it´s about them "power-hungry-stiff as hell-Big-woofers-problem"
If i will buy a new big woofer today, I will never go over 5-600 watt power handling.
Because the stiffnes and superhigh power handling, make the woofer "not musical".
And unother problem with this type of woofers is that "almost nothing happens" BEFORE enough current forces the powerful motor "to go to work", so it won't be a slowly rising curve, but relatively flat until enough watts force the "curve" to sharply rise upwards.
And when this "curve" rising the SPL in ALL its frequency band have to large differances.
Hope you understand what im trying to explain, English is not my native language
regards John
Not totally clear on the design goals here but if size is the main concern, isobaric boxes would limit the needed volume for the drivers.
I alway´s take room gain into it 👍
But "never" in my diy´s use bass-weak drivers, for bass is fundamental in my musiclistening.
Because if you only have one exact spot to place the pair of speaker at in your livingroom "to get" sufficient bass, that it self become a big problem.
And i had have that problem with many of the commercial speakers that I owned, and was one big reason that i get into diy.
Regards John
The person in question was actually James Novak of Jensen loudspeakers, who very much did know how to design for residential buildings 😉 and largely pioneered lumped-element analysis before Thiele & latterly Small, Keele, Parham et al extended this field, as well as making the first mathematical analysis of practical multi-driver arrays and their interactions.
It can be quite useful actually, since it's not really a rule of thumb as such. However, you have to
a/ Accept that it has different priorities to many subsequent approaches -they're not the same thing, and it isn't targeting a fixed frequency / amplitude alignment in the sense it's usually taken as being today. And
b/ It needs to be viewed in the context in which it was created; Novak was expecting (explicitly set out in his design guidelines) people to use the click test to achieve appropriate damping for a given situation -both for the speaker alone & when in situ. Which to be honest is probably a more sensible approach than is often taken these days.
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Hi,
this seems like an opinion more than fact. Although I've seen same thing mentioned few times it's hard to imagine what mechanism would be reponsible for it to happen. Such driver would have highly non-linear suspension and be quite unusable as you suspect, I just don't think these are available anywhere as they would not sell any.
If suspension is stiff it just means resonant frequency goes up, compared to looser suspension. Actually, all drivers have some non-linearity in suspension, but it's most linear with very little excursionand gets worse with more excursion, exactly opposite what you describe. So, what you describe doesn't make sense to me with my current understanding. Do you have any data to back this up?
Based on my experience I have to disagree strongly with both these assertions.
A good (large) PA subwoofer using very low excursion will usually sound better than a tiny hifi one working hard to move the same amount of air.
(In reality, the larger a driver's area, the less air it has to move for a given spl, as it is acoustically better coupled to the surrounding air's acoustic impedance).
My PA subs working at domestic levels sound far more 'musical' to my ear than any hifi sub I have heard, and continue to sound good up to high spl PA levels.
As tmuikku rightly asks, data to show that PA drivers have a significantly different and decidedly non-linear power-to-spl ratio compared with hifi drivers would be most interesting and educational.
If anything, I suspect the opposite is true, as a large PA driver will not suffer the power compression of a small hifi unit.
You mean less excursion they need for a given SPL if the diaphragm area is larger.
Gentlemen
I have never stated that this is a "fact", i said that it was my experiences from my hifi-life until today.
Have own so many "big" speakers, been to hifi fairs and at home of many hifi friends, who had "everything between heaven and earth".
I have today 3 Peerlees 12 inch XXL 830847 woofers (2X8 ohm voice coils) in 100 liter each per side in my basement setup.
And together with an MTM with 99 dB midrange drivers, many will call these PA
In general PA drivers are really good these day´s, but not if we speak about real large "power-hungry" PA drivers.
Allmost any of them play´s lower then 35-40 hz, and for me music begains with lower 20 hz because that is the "fundament" for "good sound" ( It fills the room from "the floor" and up, and make listening on music very valuable & unique)
All woofer drivers designers have to choose a compromise, and i think PA woofer designers never ever goes for "lower power handling".
My Peerlees XXL 830847 have 350 watt power handling and BL 10,2, Faithal XL1600 have 3200/1600 watt power handling and have BL 26,7
But remember, this is MY opinions....Only mine!
Sheeeeeeers
Best regards John
Hi, yeah your observation might be true but the explanation seems a myth so had to comment on it 🙂
If one woofer needs volume pot more than another, in order to make bass, there must be some explanation. Since compression and other non-linear effects increase with volume pot the explanation very likely involves auditory system.
For example, if the systems were calibrated with some nice loud playback level for same frequency response, and now if you turn the systems SPL down and the other makes anemic/lean bass while the other stays balanced the reason would be that the "better one" might have been compressing while the other had not, and now equal loudness curvess make the more linear system sound weaker. Check frequency responses and it should be apparent there, the anemic system had same frequency response all along while the "good sounding" has some shenanigans.
Another related, lack of distortion and flat frequency response makes bass disappear from perception on low SPL level, but if you increase distortion or boost the lows they come audible again. This is how the small bluetooth speakers make bass, there is no real bass but added harmonics and the brain is tricked it sounds bassy. Thisnis why some receivers have loudness button, bass disappears on low listening level due to auditory system.
While this is all fine, do what ever needs to be done to make a nice system, it's sometimes hard to explain why something is like it is and "better sounding" might be the one with "issues". The more linear system likely sounds way better, as long as it is tuned properly, not the same way as the more non-linear one.
Of course I do not know your observations so could be wrong, wanted to give another point of view on the subject though.
If one woofer needs volume pot more than another, in order to make bass, there must be some explanation. Since compression and other non-linear effects increase with volume pot the explanation very likely involves auditory system.
For example, if the systems were calibrated with some nice loud playback level for same frequency response, and now if you turn the systems SPL down and the other makes anemic/lean bass while the other stays balanced the reason would be that the "better one" might have been compressing while the other had not, and now equal loudness curvess make the more linear system sound weaker. Check frequency responses and it should be apparent there, the anemic system had same frequency response all along while the "good sounding" has some shenanigans.
Another related, lack of distortion and flat frequency response makes bass disappear from perception on low SPL level, but if you increase distortion or boost the lows they come audible again. This is how the small bluetooth speakers make bass, there is no real bass but added harmonics and the brain is tricked it sounds bassy. Thisnis why some receivers have loudness button, bass disappears on low listening level due to auditory system.
While this is all fine, do what ever needs to be done to make a nice system, it's sometimes hard to explain why something is like it is and "better sounding" might be the one with "issues". The more linear system likely sounds way better, as long as it is tuned properly, not the same way as the more non-linear one.
Of course I do not know your observations so could be wrong, wanted to give another point of view on the subject though.
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Which driver would you expect to be more 'power hungry...' for any given output level? The Peerless at 86dB/W1m sensitivity, or the Faital at 98dB/W1m...
I'm sure that commenters here accept that your experiences are opinions, but in matters of physics it's no surprise that we are compelled to question/correct some of them! It's how we all learn, after all...
I tell ya the ultimate solution here….IF….this room’s feature wall was adjacent to another room for storage, using that wall as an infinite baffle and mount the drivers on it?……4x18?……..woah.
Exactly. There is efficiency to be gained by increasing the speaker's surface area (Sd) as it couples better with the surrounding air. It's a little like adding a horn to a tweeter in its effect.
It we take an 18" speaker and a 10" speaker reproducing say, 40Hz at 90dB, the actual displacement volume (Vd [cone area x excursion]) will be less for the larger speaker. It's a win-win scenario.
Actually win-win-win, as the smaller movement of the large cone introduces less non-linear distortion, other things being equal - the smaller the cone, the harder it has to work, until we get to the ridiculous car audio speakers with more more surround than cone and massive excursion...
Now that is something I would like to try, and could, as I have a 1m high void under my living room!
This is true for strict subwoofer task (let's say below 100Hz). But usually, other things are not equal. One of the main problem with large cones is cone flexing and resonances at lower frequencies, starting even around 150-200Hz on some models.
The Peerlees 830847 have 92 dB sensivity, and 3 of them per side in parallel ( = 5,66 ohm) as i have must be near 98 dB.
And im greatful to have all great knowledge to share on this forum, and to learn more.
Apologies - for some reason my search threw up the 830845 and I didn't notice!