Simulations can give you an idea of what sort of EQ you might need but unless the simulation is based on measured data it would be pot luck as to whether it would be right.
Here is a useful link with practical information on how the structure of the driver relates to it's performance or suitability to a task
Choosing JBL Low-Frequency Transducers
and another with some TS measurement explanation
https://www.bksv.com/media/doc/bo0202.pdf
You can see from mark's screenshots in hornresp that the two drivers have very different native responses. At the very low end of the frequency range going 10Hz lower at the same SPL becomes increasingly more difficult the lower you go.
So the Ultimax has been designed to produce the lowest frequencies it is "happy" doing that. The TD18 has enough Sd and xmax to use for a similar purpose but it needs EQ to change it's native response.
A good way to compare the drivers when EQing to a target is to use Jeff Bagby's Woofer Designer spreadsheet. You can add a Linkwitz transform choosing the Q and frequency to see how much EQ is needed and what effect that will have on xmax power and max SPL.
It's still about displacement a vented sub just has hardly any displacement capability below that point and needs a high pass filter to protect it if played loud.
Probably for an entirely different reason. Unless the driver has to be used in a specific size cabinet it makes no sense.
The FLc and FHm are more applicable for Horn loading drivers more description on them in this Keele paper
https://www.xlrtechs.com/dbkeele.com/PDF/Keele%20(1977-05%20AES%20Preprint)%20-%20LF%20Horn%20Design%20Using%20TS%20Paras.pdf
It should be possible to make both drivers sound very similar within a certain bandwidth.
I don't do probably....If the world known mathematician says that to fairly compare two different drivers...all other variables must be eliminated...along with the idea that it makes perfect sense...it is, what it is lol
This is all doable with Horn Resp isn't it? I just looked xmax since thats the only thing that matters....
I gave up on certainty a while ago
Comparing drivers at the same Q point in a sealed cabinet (if that is what you intend to EQ it to) is comparing the drivers equally. If that doesn't make sense to you so be it.
Yes with more effort and difficulty
When you use the filter wizard you can switch through the different parameters on the fly...except for the power response aspect.. is there any reason sonically I should care about it? Rms is 1000 watts
Is that the word I should have been using the whole time?
What are the sonic differences between the ultimax and the 18h+ playing a 20hz tone in matching sealed cabs, matched spl, within XMAX....I'm going to take a swing and say , probably not a whole lot.
I appreciate the math GM but how do I interpret that to sonic differences...to think of it...has anyone described my attempt at comparison from a sonic aspect..no...(the math) its over my head but here's a chance to apply layman's terms for some of the less mathematically inclined
I can respect matching q as one way to analyze...i also can see the flaw in that neither of the drivers have match qts so augmenting final Q to neutral is one step removed from the clearest of views. I probably showed Martin the two woofers with matching Q when he corrected me on the proper way to compare drivers...mathematical genius > ...if we are going change system q why not change the other specs...I guess we do right? Via eq and spl matching...that comes with consequences (group delay/phase?) so when we neutralize q whats the consequence?.. different box sizes...but it doesn't stop there....different box volumes create different bass efficiency... all this supports comparing drivers in identical boxes.... that doesnt say that it is the only way =)...just one step closer to a clearer view...just like comparing free air specs
The driver in a box = box performance plus driver performance....If wanting to analyze the driver only....its so obvious we must neutralize the boxes performance in the process....(not Q)
Ps - I cant top your comeback on certainty lol!
Is that the word I should have been using the whole time?
What are the sonic differences between the ultimax and the 18h+ playing a 20hz tone in matching sealed cabs, matched spl, within XMAX....I'm going to take a swing and say , probably not a whole lot.
- I can dig this....If we throw Qts in there, since I've neutralized the box out of the equation. I know how Qts can affect sonics...(lower is better)...mass....(lighter is better)....ionductrance....(lower is better).....diaphragm TL and break up modes....I dunno...earlier I did say that performance around Fc should be different.....
I appreciate the math GM but how do I interpret that to sonic differences...to think of it...has anyone described my attempt at comparison from a sonic aspect..no...(the math) its over my head but here's a chance to apply layman's terms for some of the less mathematically inclined
I can respect matching q as one way to analyze...i also can see the flaw in that neither of the drivers have match qts so augmenting final Q to neutral is one step removed from the clearest of views. I probably showed Martin the two woofers with matching Q when he corrected me on the proper way to compare drivers...mathematical genius > ...if we are going change system q why not change the other specs...I guess we do right? Via eq and spl matching...that comes with consequences (group delay/phase?) so when we neutralize q whats the consequence?.. different box sizes...but it doesn't stop there....different box volumes create different bass efficiency... all this supports comparing drivers in identical boxes.... that doesnt say that it is the only way =)...just one step closer to a clearer view...just like comparing free air specs
The driver in a box = box performance plus driver performance....If wanting to analyze the driver only....its so obvious we must neutralize the boxes performance in the process....(not Q)
Ps - I cant top your comeback on certainty lol!
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Haven't given it any thought, I just answered [correctly TTBOMK] your question WRT Mark's statement, no more, no less.
It says
since [Fs] is the mean, so has nothing to do with 30 Hz or this conversation [knew I shouldn't have posted it, but forced to copy/paste as much stuff as I can nowadays].
The [~30 Hz] is based on the 18+'s 29 Hz Fs that either by happenstance or design matches up with the 'classic' frequency response chart I referenced.
Of course! But as has been repeatedly stated at one time or another on most box/driver design threads and 15x on this thread alone; it's a 'horses for courses' situation, i.e. use the driver that best meets the needs of the app or vice versa [change the needs to fit the driver specs].
Once again here is the ultimax vs the 18h+ with the Box performance nuetralized/equalized
Comparing 2 different woofers in 2 different boxes is the equivalent to measuring two different compression drivers in 2 different horns (Hornresp has been updated since this 1-2 year old graph...I just cheacked it out to make sure these graphs were what I thought...the responses are within 1db of each other the Ultimax 1db higher than the 18h+ until AE drivers midrange ability takes flight)
Long story short....the 18H+ as an awesome subwoofer...and an awesome midwoofer. The qts difference is going to make a diff...the mass is going to make a diff...the inductance is going to make a diff...In the terms of accuracy...unless the 18h+ woofer is not rigid enough (it is) The 18h+ is going to be more accurate....
The point missed...some people don't like the sound of technically accurate deep bass.
Comparing 2 different woofers in 2 different boxes is the equivalent to measuring two different compression drivers in 2 different horns (Hornresp has been updated since this 1-2 year old graph...I just cheacked it out to make sure these graphs were what I thought...the responses are within 1db of each other the Ultimax 1db higher than the 18h+ until AE drivers midrange ability takes flight)
Long story short....the 18H+ as an awesome subwoofer...and an awesome midwoofer. The qts difference is going to make a diff...the mass is going to make a diff...the inductance is going to make a diff...In the terms of accuracy...unless the 18h+ woofer is not rigid enough (it is) The 18h+ is going to be more accurate....
The point missed...some people don't like the sound of technically accurate deep bass.
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Well, as high up as the lowest, Fs, Qts' for widest BW shifts it and judging by all the simmed, measured box, horn designs that has proved it to mine and many others satisfaction, it's really accurate.
....and yet they do a fine job for any box designs where I have a use for it, so we'll have to 'agree to disagree'.
Dr. Geddes is several leagues more competent than me to answer, but the 'long and short of it' IME WRT driver specs, construction, sonic comparisons; I've periodically posted that it comes down to pace, rhythm & timing [PRaT], so the lower and/or the narrower the BW, the less likely we can hear any differences'
Comparing the Ultimax to the AE is an 'apples n' oranges comparison that will require significant EQ to 'dumb it down' to even approximate the Ultimax's 'sonic signature' and no way you can 'upgrade' it to compete with the AE's.
Comparing a driver and a so called clone comes down to more than just matching specs, such as component design/construction, manufacturing Quality Assurance [QA] program, etc..
I mean I could call up any of the well known manufacturers and have them build me some 15" drivers that spec near enough identical in every way QA might measure them to an Altec 515-8G and I guarantee you they won't perform even in the same 'ballpark' [according to some folks that did] unless made by Great Plains Audio because they have [new] original tooling, parts, etc., and assembled to OEM specs by 'real' ex-Altec employees who know how to properly dope the diaphragms, etc., to get just the right amount of TL, breakup modes to match the master reference, etc.; and then there's motor design/construction, etc..
As for driver distortion, never given it much thought other than to design, build based on any 'shortcomings' as much as practical, i.e. 'horses for courses'.
True, it's a folded up open baffle, but he chose to more narrowly define it, which I disagree with.
To me this is nonsensical. A good way to design something is to set the needed performance and then find the best way to get it.
In a low frequency sealed box two parameters are very important Frequency of F3 (F10) and Q which sets the slope of the roll off below or how flat the alignment will be. The lower the Q the more demands are placed on the woofer to get it.
The driver and box in combination give this you can't really separate them out. The parameters of the driver will dictate what sort of box will work better. Some drivers are designed to be reflex, some were designed to be horn loaded and so on. You can most likely beat all of them into shape with enough EQ and power but that is hardly the best way to do it.
Eliminating variables in comparisons is good scientific practice but when that variable affects the ultimate performance of the combination keeping them the same will not result in finding the better potential performance just the best in that size.
I wasn't intending to disagree with you, how have you found them to be useful in non horn loaded enclosures?....and yet they do a fine job for any box designs where I have a use for it, so we'll have to 'agree to disagree'.
This is what happens when you put them both in an equal size box that is slightly over 315l....might of been 326l IIRC
Make sense of that when just about every variable we are talking about has an affect on ultimate performance....Looking at the above ~326l boxes....using eq to smooth out mid sensitivity. is going to be detrimental to what? Or is it going to actually boost SQ due to lowered excursion.....
Yet the two drivers with Ultimax with a ~Q 0.7 and the 18h+ with a ~Q 0.35 (looking at my 315 box in HR) and the roll off is the same... The sensitivity is almost identical so both drivers are "trying" the same but one is much more accurate in play.......why isn't your theory playing out?
Two simple non detrimental filters.....do tell (these boxes are smaller than in the graph above hence the lower efficiency...the lower roll off is unchanged by eq...group delay went up ~0.3ms lol) A good change took place as the attenuating filters lowered excursion even further.
When looking at the the first graph where the box has been made a mute point....the true victor stands out....lower Q, lower inductance, lower mass driver, and higher efficiency win. The win for the Ultimax is Higher Xmax....for mycase....something that will never be encroached upon
Who ever designed the 18h+ is a genius in short.
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I can't see your graph to comment on as the attachment is invalid. This is another discussion where I feel like I am trying to explain that the earth is in fact round and not flat and getting nowhere.
In case it wasn't clear my only point was that the drivers were different and were designed for different use cases.
In case it wasn't clear my only point was that the drivers were different and were designed for different use cases.
According to these impedance measurements, the AE TD18H+-4 Apollo version actually has a lower peak than the Ultimax. Might call that one a true sub?