# Xmax

#### Randy Bassinga

What you need is higher magnet diameter or surface, nobody does that.
These drivers already appear to fill out the form with a magnet almost as wide as the cutout. You must be talking about drivers that can only be mounted from behind the baffle if the magnets get any larger

#### Randy Bassinga

Hmmmm, is there no end to units and measurement condition inconsistencies in datasheets?

Even google couldn't teach me how to convert 818.8m mH to mH

Apologies if this one is well understood by folks, my maths and things are very poor

#### witwald

I would like to see a BL(x) curve of these things.
As well as all the other things.
There is a Stereo Integrity 18-inch HT-18 v3 woofer that has an Xmax of "25 mm one-way 70% BL". And the published BL(x) curve is as follows:

#### witwald

Even google couldn't teach me how to convert 818.8m mH to mH
I wonder whether "m mH" is shorthand for "milli millihenries", or microhenries (μH). If so, then that value corresponds to 0.8188 mH. The extra "milli" makes it necessary to divide the 818.8 value by 1000.

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#### Randy Bassinga

I wonder whether "m mH" is shorthand for "milli millihenries", or microhenries (μH). If so, then that value corresponds to 0.8188 mH. The extra "milli" makes it necessary to divide the 818.8 value by 1000.
Is that like trying to say milli millimetre? Boggles the mind!

Thanks for translating that man

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#### JMFahey

Is there something wrong with that approach? I thought the law work in three aspects. So, when space is the premium, what is so wrong about turning size down while increasing drive?
Constraints apply but they could have designed a WAY better woofer with the materials available.

#### JMFahey

These drivers already appear to fill out the form with a magnet almost as wide as the cutout. You must be talking about drivers that can only be mounted from behind the baffle if the magnets get any larger
I am talking by what you need applying Physics laws.
Mounting considerations are something else.

If they can't mount a larger diameter/surface ferrite magnet there, then they should not use a ridiculous 30mm thick top plate.

Or use a stronger magnet material, such as Neodymium.
Which they did not and turns that speaker into a joke.

#### JMFahey

In the 80s , together with a couple partners, we made a 30" speaker, with a 6" diameter voice coil, a monster.
I designed it, and could NOT find a large enough Ferrite ring magnet.
So I used a field coil.
It had to "perform", not just "look good" 🙄

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#### Randy Bassinga

Constraints apply but they could have designed a WAY better woofer with the materials available.
Maybe look at it from another perspective. Looks like they took a different approach. There are different configs within each driver size, especially the 12 and 15s. Within a narrow price range, you can get a 12 that is designed for 118dB'ish SPL but needs lower power and a large cab, then there is another that is designed louder but doesn't go low and needs only a tiny cab. Then there is another that also needs only a tiny cab but goes low beyond 20Hz and flat and loud. Then there is one that almost goes as low but in an even smaller cab and a little less output. Then I think there are two models that fit in between the mentioned ones. That's quite a few different series within just one driver size. All meant for a different job and folks of varying music tastes, budgets, needs such as daily driver, show car, SPL comp contender, SQ comp contender. Anyone who can see that can't help but respect and support that. Especially nowadays when brands are consolidating model lines and many only offering just one series per size. Both JLAudio and DS18 offer this wide range of choice

Most folks here try to ignore the fact that accommodations for many are getting smaller. Where in 1992 I had dual 15"+ horn PA bins in the bedroom. Now my whole house almost as small as that bedroom. You and similar mined folks are all about pro builds and use at a large scale. Is there any reason why the balls need busting and holy smitting when folks turn to more highly engineered drivers designed for extracting clean very low bass from very very small volumes

The car audio scene is cut-throat. More money is prolly spent in one year in this scene in development than so called Hi-fi and Pro Audio, where many are still offering small drivers that need a wheelie bin class cab. They great for those with the space, but there are also folks like me who do do things with music and sorely need much smaller and more capable gear. Unlike me, most of these folks actually shy away from Hi-fi type forums and have their own fellowships through social media

I refuse to lug huge bins and things. Neither do I wish to see boxes larger than the microwave in the house, unless it is an actual microwave! I also wish to learn more about correctly applying this tech. I really don't see why such drivers such as JL's W7s and DS18s ZRs and the nuts ZXIs offend folks like you? I would have thought that you of all people would have been at the front of guiding the development towards ease of living and working. The regular PA and Hi-fi market is already very well covered. I hope you will be up for the challenge of developing for folks with more compact needs

With all respect
Randy

#### Randy Bassinga

Btw, in those various series in the 12" size meant for different roles, those three aspects of the law are getting tugged variously to arrive at different results

#### weltersys

If they can't mount a larger diameter/surface ferrite magnet there, then they should not use a ridiculous 30mm thick top plate.

Or use a stronger magnet material, such as Neodymium.
Which they did not and turns that speaker into a joke.
Certainly the driver's weight could be reduced using Neodymium, but the 35mm Xmax Stereo Integrity 18" is no joke, it comes in about +12dB SPL (+6dB for each doubling of excursion) over the 9mm Xmax JBL 2242HPL in the low frequency range below 50Hz, in line with it's rated Xmax.

These are 2meter outdoor tests:

https://data-bass.com/#/systems?_k=vhj336

Josh Ricci's data-bass comparisons don't joke around, he's wrecked plenty of drivers finding their limits

Art

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#### Randy Bassinga

Art, thanks for sharing resources like these. You may have noticed my attempts to build some sort of mental context and reference re output levels. If I peruse the 31Hz and 40Hz columns in the Max Ouput tab, I can see most drivers outputting between approx 94dB and 122dB with some exceptions going higher. Can I take this a sort of industry baseline for powerful single driver subs?

And then can I use that to assume that;

A 95dB at 20Hz
And rising to 109dB at 30Hz
And holding steady to around 70Hz
Then dropping slowly back down to 95dB around 200Hz
And up to 20kh

Would make for a very loud and bass solid loudspeaker for a 3m x 6m living room. That is the prediction for one speaker with 600w and no boost, with another 600w in reserve for any boost. Actual use is 4 such speakers. One in each corner for a phantom centre channel based HT, Karaoke and just general music listening while having a mixer connected too. Should I try to get rid of that rising response over 30-70Hz by tuning lower and closer to 28Hz Fs from the current 33hz? I did that to dial in more SPL over the 5-string band by sacrificing some HT low end

The key point from the above though is that I am trying to come to terms with some sort of mental context on how loud and powerful in bass would such a single loudspeaker be in that room. I currently don't have anything to try to create these levels with to learn in real time. Also not targeting these levels specifically. These are the results of driver choice for the 3-way loudspeaker and space and available power. Is this not near powerful enough or excessive, I have no idea based on not knowing how loud 109dB is at 30hz or 95dB is at 40Hz. The higher frequencies, I can create and feel/listen to those levels easy enough

#### Randy Bassinga

If that sounds like a good output performance, than I am good to start on my most important project that I would like to start using seriously by August. Guys, please help a noob out

#### Randy Bassinga

I should mention, in the above setup. The mid and tweeter are limited to 10w to match up with the LF driver. I will be using EL34 based tube amp for the top section. At full power these predict flat down to around 80hz doing 119dB, but I wouldnt be using full power, only 10 tube watts and 75Hz tune. More interested in a heavy capable bass response then loud uppers. Think, getting the effect of the bass knob turned up natively present in the 3-way cab. I have very many projects across many fields to tinker with, but this one is my fav. I can use such a loudspeaker either individually or in full set, with home tube + class d power or away with full power on a dialy basis with all our student practice and family movies and karaoke as well as music and karaoke at others places at birthdays and parties or just chill and music nights. I will be bolting the 2 each of the 4 cabs back to back to get bidirectional response when using these away from our living room

Something like this high power, point source has been on the mind for a long time, but now I have an immediate need for it with the students band practising in the school hall and a hut in the park. The school PA is quite muddy and lacking in any bass. The reggae type practise is our initiative, not the schools. I don't have the space to keep a regular type PA or any large speakers. A loud full range loudspeaker set that is daily home use and micro-pro use. Something that I can pack up and deploy easily and safely. At home source is a HTPC fed through a digital mixer and away, an analogue console mixer via a digital mixer

The two-way coaxial available are used as HF and 12" sub as LF in a single cab with independent 35L and 8L volumes in an active format with built-in 600w modules x2 for each voice coil on the LF driver and a 300w mono module for the coaxial but this will have bypassing for home use with tube for the top

I have attempted and failed a number of DIY speaker projects due to not being able to get valid sim models and not knowing enough about things. This is one that i want to get right. I am limited by choosing from SBA and DS18 brands due to budget and accessibility from my regional rural location 1400kms from Sydney city. Most vendors send messages either requesting a cancel or demanding massive postage or just say out of stock for heavier items

#### wg_ski

Is there something wrong with that approach? I thought the law work in three aspects. So, when space is the premium, what is so wrong about turning size down while increasing drive?
A 12” driver that can do that 25 mm will require a box the size of a microwave oven, just to house the damn thing. To hell with tuning. The motor is as big around as the frame, and darn near as deep. That’s a cubic foot internal just for starters. And you probably want inch and a half material to build the box. Power requirements will force you to a 2U rack mount amp - a Labgruppen clone or similar In the 4kW range. Add that to the required cubic footage.

If microwave oven size is “too big” where do you go from there? An 8” driver with a 50 mm linear stroke? Can it even be made? Will the motor even go IN the mounting hole? Going from 4 to 8 kW won’t make the amp any bigger, but will make it cost more.

The fact of the matter is that for practical purposes you don’t need that kind of bass in a small apartment space. It will bring the cops and make a lot of irate neighbors. If the place is a jungle where the police fear to tread you’ll find yourself shooting someone over it. You‘ll either be at war with someone over it, or they’ll break in and try to rob you. SPL requirememts go down, box sizes get practical. It’s self-correcting. A practical 8 or 10 with a 15mm stroke and 200watts, perhaps.

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#### Randy Bassinga

The fact of the matter is that for practical purposes you don’t need that kind of bass in a small apartment space. It will bring the cops and make a lot of irate neighbors
Doesn't make sense, I thought the consensus was that my sim results were called for being as loud as a poot in a tunnel!. After working and shopping hard to add a few more decibels to just enter some semblance of loud ability for an occasional away trip, and to hope to fill in as a lil PA system for the girls practice....you say "that kind of bass"

Been asking for help forever now to get some idea how loud my sim results are, starting from the mid 90s to low 100s dBs in the failed Club Sandwich project to iteration after iteration uipping the SPL. Always with the qualifier that my only experience with knowing how loud something measures is the low to mid 80s dB bass levels at my regular listening position with the highest volume that we are comfortable with during weekend karaoke

Even in this thread, I think I made a couple of requests if 96 odd dB at 20Hz can be considered fairly loud and that I do not currently have any built gear to create this level and no idea how much louder this would sound or doing 109db at 40Hz because my current system can only go 104dB. I have no way of knowing how much louder another 5dB is when already at 104dB. This business of thinking that my sims aren't making enough SPL is the reason for going from the 6.5" driver of the twice failed Cub Sandwich project and thrice failed soundbar project

I do wish folks coming to a consensus if the response that I am getting in the current sims is finally loud enough to monitor and record a small ensemble while entertaining a dozen on the porch or deck while spending the rest of it life in the home studio/living room as one pair on the desk as monitors/fronts and one pair in the back corners for a centre less and sub on the floor less HT

Btw, mention was made through all the failed project attempts that the deck/tiny home install is a home away from home DIY houseboat currently also under construction in Hervey Bay with a couple of hundred km of people free lee shorelines with open mooring conditions. Other places of use are an occasional small function DJ or karaoke gig and school hall. Also that the on land home is also a detached tiny and not apartment type

The current sims are showing a peak 109dB over 40Hz and 96dB at 20Hz in a single microwave sized cab with plans for 3 more. One per channel in a four channel surround for HT and back to back bidirectional for away PA use and built as 4x 3-way cab or 4x satellites and 4x subs in yet another project attempt thread. With the assumption that the tops can be run with tubes at home use and volume can be turned to to acceptable levels depending on the time of the day

May I at least take your comments as confirmation that I have a successful result with getting loud now

#### Randy Bassinga

A 12” driver that can do that 25 mm will require a box the size of a microwave oven, just to house the damn thing. To hell with tuning. The motor is as big around as the frame, and darn near as deep. That’s a cubic foot internal just for starters. And you probably want inch and a half material to build the box. Power requirements will force you to a 2U rack mount amp - a Labgruppen clone or similar In the 4kW range. Add that to the required cubic footage
Bear in mind that I am the uneducated speaking to the educated please
Lats take that cubic foot for starters, does common sense not say that just a few cm of expansion in any of the three axis would start yeidling an increase in volume to regaining that much volume back as the working volume?

Please see the Cub Sandwich thread on how I am able to fit a tuned working driver and dual passive radiators as well as 900wrms and DSP and dual fans and comprehensive driver and electronics heat disposal in total 17L of external volume rated at 30kwk of reciprocating motor on the transom panel making the baffle to extract 105dB over the bassline and house the amps for the mains. This was deemed as would disappear on the porch, in other words, a poot in the tunnel. In another situation, when showing a 118dB plot to someone presenting as a studio guru, was deemed to not even bother and stick with cans

So please tell me, do I turn it back down to dual PR based 6.5" again or turn up to the dual 12" + coax inna microwave with a 122db flat plot iteration that I have been siming over the past two hours

I have to say that I am thoroughly lost now on how much SPL to target to match things like a dholak and harmonium on the floor with electronic kick and electric bass and when not working, be able to replace the current 2 pairs of Logitech z623s providing the four channel HT and home studio

#### Randy Bassinga

Fearing that current sims would be more baked beans materials, here is latest sim for dual ZR12.4Ds and the coax idling Xmax inna microwave. Is it loud yet? Seriously?

#### weltersys

If I peruse the 31Hz and 40Hz columns in the Max Ouput tab, I can see most drivers outputting between approx 94dB and 122dB with some exceptions going higher. Can I take this a sort of industry baseline for powerful single driver subs?
94dB to 122dB is almost two orders of magnitude, like comparing a car that gets 2 kilometers per liter to one than gets 200 kilometers per liter.
There is no "industry baseline" for "powerful single driver subs".
Those levels are measured at 2 meters outdoors. Peruse the cabinet volumes and designs.
And then can I use that to assume that...

Would make for a very loud and bass solid loudspeaker for a 3m x 6m living room.
No, you can't make easy predictions about room response, but you can measure an speaker's response outdoors and then inside to determine what gains and losses will occur.
I currently don't have anything to try to create these levels with to learn in real time.
You have small speakers. At any given level outside, as you move to half the distance, they will be ~+6dB louder.
Also not targeting these levels specifically. These are the results of driver choice for the 3-way loudspeaker and space and available power. Is this not near powerful enough or excessive, I have no idea based on not knowing how loud 109dB is at 30hz or 95dB is at 40Hz.
Stick your ear next to your little sub and you can get levels like that.
The "feel" won't be the same on your body, but that's another measure only you can make for yourself.
Is it loud yet? Seriously?
Simulations are not loud.
Seriously.
I will be using EL34 based tube amp for the top section.
With ~ten watts that could sound too loud for small room practice (I use a -10dB attenuator on an 8" guitar speaker) or be about "hardly heard", as I found out taking my Valve Jr. amp to a house party.

#### Randy Bassinga

Ok cool, makes sense. I suppose if the major limitation is space. And packing in as much hardware as possible in that space is another constraint

DSP is available to take care of attenuation or boost