Well, there're plenty of measurements combined with the Thiele-Small parameters which help a box designer software calculate how your complete speakers might behave in some aspects - like freq response.
Let's have a look at a very simplified drawing around this theory: if I understand you correctly, I'd need to design a box with a freq response like below, to get a flat result, for a speaker like on the left ? Free air of course.
My baseline is then the manufacturer's datasheet, I look at the measurements, red line. I design my box then accordingly (blue line), taking the 'inverse' of red line 'til flat.. and I should be good overall. Not perfectly, but somehow closer than without the simulation sw. Right ? In theory.
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But noooooo - we don't design complete speakers like on the upper-right sketch to get such a curve.
With all of the others I agree, except with that, what a speaker designer program is showing me (not accurately but it gives a good reference point if I'm shooting at the right direction at all or will completely miss the target).
'Cause you tell me I should consider speaker's own freq. curve and modify the end result with that in my brain. I think it's already done by the software, with the help of Thiele-Small parameters and tons of mathematical equations which come partly from theory and partly from experience. The software is able to assume the drivers own curve indeed, not exactly of course but approximates it from mass, areas, suspension stiffness, etc.... so at the end of the day if I design a speaker with a linear freq response and measure it in the middle of a golf club at 1m giving it 2.83V into 8 Ohms at sea level 20 °C no wind and it's f* quiet, I think I should get more or less (in that you're right, it's not exact) what I planned, a somewhat-linear curve in the region what matters.
At that point if I measure this completed speaker I will definitely NOT add speaker frequency curve once more with my brain 'cause it's included in the box design calculations, that's why I use software to free my brain of the task of an op-amp-like signal combiner
However what I would take into account and would use brain capacity are:
- how far I place the boxes from my walls inside the room, sides, behind
- to estimate/measure/hear how this modifies my overall freq response
- how high I lift them from the ground
- rotating them - or better not ? (horizontal dispersion)
- direct the drivers or better not ? (vertical dispersion - see MTM & other theories)
- crossover types and their effect on SPL, phase, group delay, ringing, soundstage (hell yeah), imaging - Mr. Linkwitz could teach us a lot about these all ..
.
.
.
- weighing all these with a number and adjusting the whole setup beginning with the biggest number.. kind of giving prios 'cause ALL parameters cannot be adjusted perfect.
So back to Eminence: f* expensive. I appreciate your input saying they're crap but this is just 1 opinion. During the next years I might gather some more inputs about these and as the number of samples increase (let's call it "Eminence evaluation sample rate") I might be always a bit closer to a real fact if they're really thaaat bad or not. Until than - a fat "thank you".
Back to the plots:
1. I don't believe all manufacturers measure their speakers and plot their curves the same way
2. I believe they might apply little or even more cosmetics as well so at the end what an enthusiastic DIY-er builds might be a complete mess - or even not. But luck plays a strong factor, especially with environment and everything else in mind.
OP amp signal combiner. Nice one
And nice drawing also. That's exactly what I meant. I use that principle in all of my subs with great results.
Luck is always a factor. Luck to know about such things and to be able to build speakers. Etc.
Where the vendor plots differ is spl. Some measure with higher power and some mounted on a baffle and some even in a enclosure but then again they tell you about it. Of course this needs to be taken into account. And yes some use smoothing. Some use a "nice" dB axis where peaks and dips dont look that bad "on paper".
If you want to be sure you need to measure yourself anyway. But from reputable vendors the plots are pretty accurate in my experience.
Also impedance measurement helps to nail the tuning frequency.
Regarding TSP.
These are just measurements of the properties of the driver ONLY at the (specific) resonance frequency.
No chance to create a (accurate) SPL graph from that. Not that I know of. But maybe I am wrong.
I built many subs using this theory and they measured flat outside using a calibrated mic. And they went lower than the speaker roll off.
Regarding room effects and placement.
Imho the best basis is flat response.
Outdoor it will work like a charm without EQ and indoor there will be no worst case scenario where room gain adds to a possible already existing peak in response.
Or cancellations "add" to a dip in response.
All you need to do is EQ the room gain out when flat.
So you need less power, less cone movement, less distortion.
If theres a cancellation only a small boost is needed.
When response is not flat and there is a dip. Let's say 6dB for example you need to boost that freq and would need 4x the power to compensate.
Worst case: dips add to dips, peaks add to peaks. Therefore my theory is: flat is the king.
If you design for a specific room then you can take room gain, cancellations into account also. But then again response is only optimal in that specific room.
Of course there is the small chance when ignoring "everything" maybe it will magically fit in the end somehow although not optimal. But maybe even very good. I already experienced such interesting circumstances.
In this spirit,
Good luck
To go with your 18" Volt for a 3way I think I'd go for an 8" BMS driver (they do 3, ferrite and neo) and the Audax TWO34 with Jantzen's waveguide (Audax TW034 Waveguide - Jantzen-audio.com).
There are plenty alternatives to the BMS mid but they look rather tasty considering the published distortion plots are taken at 100W input.
Cone Drivers
BMS 8 PA Speakers
There are plenty alternatives to the BMS mid but they look rather tasty considering the published distortion plots are taken at 100W input.
Cone Drivers
BMS 8 PA Speakers
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OP amp signal combiner. Nice one
And nice drawing also. That's exactly what I meant. I use that principle in all of my subs with great results.
Moin moin
So you design your subs with an intended peaking towards deeper freqs to compensate the driver's slope stated on data sheets. Hmm. Interesting. Really. I've also designed some boxes which sound very nice (better said: the closed boxes have less bass except I put them a bit more close to the wall and corner). So the issues are:
- placement of boxes
- manufacturer speaker data and freq curve (open-air, open-baffle 1 wall only or even a ported/vented baffle of some sort of optimum they never specify)
The best I'll do is:
- buy the Daytons (most probably, despite high VC inductance)
- connect them to one of my amps and do a burn-in in free air for couple of hours with low-medium signal
- measure TS parameters again with DACT in an environment close to ideal
- design a box with WinISD or equivalent
- adjustable reflex tube
- put into final place in my living room
- listen, measure, listen, measure, damp walls, damp box (a bit), adjust port length, listen, measure, damp walls, adjust port length, and begin again..
- if 1 box is more or less okay, producing what I've imagined, I'll have the 2nd one made as well and have them lacquered to look at least like some kind of furniture instead of raw mdf. This is what I call girlfriend-compatibility
- I'm going to be f* precise else I can trash the 1st mdf box with an axe and begin a different approach & new box.
- I'm always talking about a box.. it will be a cylinder lol
Anyway I begin to get your logic and will keep all these in mind. Thanks for the great conversation and pls let me know if you come to Plattensee irgendwann mal im Sommer..
When the beasts are ready I'll post pics in my topic.. don't want to flood this here anymore. 
Cheers
This one:
BMS 8S219 8 250 Watt Ultra Low Distortion Low Midrange Driver 8 Ohm
It is the ferrite version of the 8N519 and they seem to measure a little bit better than the Nd ones. They are also cheaper so unless you have to move your speakers a lot there is no reason to pay extra.
BMS 8S219 8 250 Watt Ultra Low Distortion Low Midrange Driver 8 Ohm
It is the ferrite version of the 8N519 and they seem to measure a little bit better than the Nd ones. They are also cheaper so unless you have to move your speakers a lot there is no reason to pay extra.
Moin moin
Hmm. Interesting. Really. I've also designed some boxes which sound very nice (better said: the closed boxes have less bass except I put them a bit more close to the wall and corner). So the issues are:
- placement of boxes
- manufacturer speaker data and freq curve (open-air, open-baffle 1 wall only or even a ported/vented baffle of some sort of optimum they never specify)
The best I'll do is:
- buy the Daytons (most probably, despite high VC inductance)
- connect them to one of my amps and do a burn-in in free air for couple of hours with low-medium signal
- measure TS parameters again with DACT in an environment close to ideal
- design a box with WinISD or equivalent
- adjustable reflex tube
- put into final place in my living room
- listen, measure, listen, measure, damp walls, damp box (a bit), adjust port length, listen, measure, damp walls, adjust port length, and begin again..
- if 1 box is more or less okay, producing what I've imagined, I'll have the 2nd one made as well and have them lacquered to look at least like some kind of furniture instead of raw mdf. This is what I call girlfriend-compatibility
- I'm going to be f* precise else I can trash the 1st mdf box with an axe and begin a different approach & new box.
- I'm always talking about a box.. it will be a cylinder lol
Anyway I begin to get your logic and will keep all these in mind. Thanks for the great conversation and pls let me know if you come to Plattensee irgendwann mal im Sommer..
Cheers
Moin
Very good plan.
The Dayton is a good choice for keeping costs low.
Anything but the Eminence lol. No, it is a good driver (the Dayton).
Variable ports will make tuning to a room or a specific response easy.
A Cylinder!
Good luck
Well at least damping will be easy.
I would just cover the back wall with 3-5mm thick lightweight non woven air permeable polyester. Maybe you will need a little more (taste differs) then just add on the "side wall" on the back right at the other damping a few cm`s in tube shape). This will kill the hollow sound and produce a more hifi sound and better decay. I use installation glue since it will be hard when dried and will be easily removable when experimenting.
Thank you too and thanks for the offer
I love Hungary and the people, especially Budapest and have been to Balaton many times.
Nem tudom.
Sorry pal, not sure where you've got this, but it isn't right.
When you put a driver in a box, those two working together produces the frequency response curve at the low end, which is shown in WinISD, Hornresp, etc. If you remove the speaker, the box does not have an inherent response of it's own. How could it? It has nowhere to connect the amplifier, and no way of making the electrical signals into sound.
I think perhaps the reason you've found simulations to be based on "luck" is that you haven't been using them correctly. There are a lot of simulations and measured results around here, and they often line up very well.
To the original poster, I wouldn't worry too much about a dB here or there in the bass. Moving your head 6" in the room can give changes of the order of 6dB. Pick a woofer that goes nice and low, and has enough clean excursion to go as loud as you want it to.
Chris
Moin
...
A Cylinder!
Good luck
Well at least damping will be easy.
Yeah, a cylinder. But it's apparently a horrible project in this size. Cutting circles out of ca. 240 (!!) pieces of mdf plates to get outer diameter, then again cutting the inner part out of the circles, again 240 times. Insane work and even by doing this like here, to produce such an inner shape similar to this: scroll down for inside..
I talked to 2 carpenters, both stated it can be made but insane project and they'll most probably loose their machines, at least a couple of cutting tips for sure.
I told them to calculate it into the cost .. -> they came at around ~USD1500 converted, for 2 big cylinders, raw mdf. No piano finish, nothing else, just raw costs. Insane for a DIY box. But hey, it will last for 30+ years (I hope). 
Yesterday I just wrote to a cooper (wine barrel maker) how about .... .. and if rigidity would be sufficient ... we'll see. Just waiting for his answer. link I'm sure he'll have some interesting comments to this. 
Due to cylinder complexity I'm also considering a rounded-triangle-shaped box with absolutely no parallel walls, not even on the back. Inspired by this.
I am checking out two Volt Bass/Mid drivers at the current time the BM 228.8 and the BM165.1
This model from ScanSpeak is also under investigation, the Revelator 18M/8631T00
This model from ScanSpeak is also under investigation, the Revelator 18M/8631T00
Not sure about the Scanspeak.
Seems imbalanced in the sense that at raised levels where the Volt radial is still loafing along the Scanspeak would be begging for mercy and contemplating suicide.
Hence my suggestion of the BMS and Beyma AMTs: They are loafing when the Volt is loafing and get stressed roughly when it gets stressed and that should be way beyond anything you ever need.
Which is a good thing because sufficient headroom is essential for high quality, dynamic music reproduction.
They are also very, very low distortion options up to and beyond civilised party levels.
The Beymas in particular are amongst the very best tweeters available for any price.
Seems imbalanced in the sense that at raised levels where the Volt radial is still loafing along the Scanspeak would be begging for mercy and contemplating suicide.
Hence my suggestion of the BMS and Beyma AMTs: They are loafing when the Volt is loafing and get stressed roughly when it gets stressed and that should be way beyond anything you ever need.
Which is a good thing because sufficient headroom is essential for high quality, dynamic music reproduction.
They are also very, very low distortion options up to and beyond civilised party levels.
The Beymas in particular are amongst the very best tweeters available for any price.
Yeah, a cylinder. But it's apparently a horrible project in this size. Cutting circles out of ca. 240 (!!) pieces of mdf plates to get outer diameter, then again cutting the inner part out of the circles, again 240 times. Insane work and even by doing this like here, to produce such an inner shape similar to this: scroll down for inside..
I talked to 2 carpenters, both stated it can be made but insane project and they'll most probably loose their machines, at least a couple of cutting tips for sure.
Due to cylinder complexity I'm also considering a rounded-triangle-shaped box with absolutely no parallel walls, not even on the back. Inspired by this.
Wow.
Very complex inside, and the cost... this will be like almost 20 of the Fane 12-250TC !
I vote for triangle since I had good results with this shape.
Sound waves seem to like it.
Somehow I don`t trust a cylinder.
It surely is a nice looking piece of "furniture".
The eye is listening, too.
So you probably should build it lol.
..
The eye is listening, too.
So you probably should build it lol.
Oh nooo.. I might reroute the trip to 2 cylinders for bass. At least for 18" bass these wouldn't be cylinders but BARRELS. Size of wine barrels
I recalculated my would-be-nice needed volume and came to AT LEAST 400 liters which is .. ehh.. still an insane big something if made in a cylinder shape, apart from construction crazyness and waste of material, etc. Came to a crossroad, what now.
So then for me the triangle shape came to my mind (Option "A") like in case of the Titus 8T but I insist on 1x18" and to achieve a big volume without being very intrusive optically in the living room I cannot just proportionally increase size but have to maintain a medium sized base footprint and grow upwards -> tall trapezoid shape. The front will be interesting since I want to place mids and tweeters aligned with eachother's and the bass' voice coil while also keeping them close to the woofer to avoid placing the tweeter too high for a listening position. Dont't want to give the upper part a somewhat down-pointing angle like on the Wilson Alexandria X2 lol.
Option "B": slim cabinet with side-firing woofer, bass crossed pretty low anyway.
So.. no cylinder.
I just gave up..
Yeaaaah, 18" woofer = 46cm diameter. 
Haven't seen such since 20 years. Great to hear that about triangle shapes. I prefer them still a little bit more than slim tall boxes with side firing woofers. Project starts in the spring, I'll show the results when ready. It will be an interesting box to maintain size and still fit into a living room quite nicely:
- symmetrical trapezoid base pointing forward: tall box with a narrow front panel (20cm, for the mids and highs), wide back panel (70cm), wide sides (65cm depth) and 1.8m height. This gives overall ca. 500 liters in volume to achieve my frequency curve and f3 point targets with this monster woofer
- bass driver put into one side, directly below the lowest mid woofer
- reflex port onto opposite site at magnet-height, adjustable port first and if measurements are ok and calibrated, will be swapped to a fixed one
Since side panel is somewhat visible by the listener (due to trapezoid base shape extending towards the back wall), the woofer on this side panel will not point 90° to the right but somewhat rotated to the listener a bit, final angle at around 60-70°, don't know. But it won't mess up bass and overall characteristics at my frequencies. That's what I already discussed with others - we'll see. Kind of an interesting experiment.
Haven't seen such since 20 years. Great to hear that about triangle shapes. I prefer them still a little bit more than slim tall boxes with side firing woofers. Project starts in the spring, I'll show the results when ready. It will be an interesting box to maintain size and still fit into a living room quite nicely: - symmetrical trapezoid base pointing forward: tall box with a narrow front panel (20cm, for the mids and highs), wide back panel (70cm), wide sides (65cm depth) and 1.8m height. This gives overall ca. 500 liters in volume to achieve my frequency curve and f3 point targets with this monster woofer
- bass driver put into one side, directly below the lowest mid woofer
- reflex port onto opposite site at magnet-height, adjustable port first and if measurements are ok and calibrated, will be swapped to a fixed one
Since side panel is somewhat visible by the listener (due to trapezoid base shape extending towards the back wall), the woofer on this side panel will not point 90° to the right but somewhat rotated to the listener a bit, final angle at around 60-70°, don't know. But it won't mess up bass and overall characteristics at my frequencies. That's what I already discussed with others - we'll see. Kind of an interesting experiment.
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Port would be opposite side, not back side. I'll try to show. This is it so far.. using this thing for the first time.. couldn't get drivers ( = circles ) into the walls. Just imagine them somewhere Tweeter to the upper front above midranges, after the step. Woofer to the right side below midrange, port to the opposite side (which is then the left side).
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Tweeter to the upper front above midranges, after the step. Woofer to the right side below midrange, port to the opposite side (which is then the left side).<spam image removed by moderators>
Rethinking this paper exercise definitely active on the bass, as this is more of a hifi speaker than a sound reinforcement device I am looking at the Volt bm2288-8 or more likely the Jantzen JA-8008 HMQ 8" unit which is more sensitive and would match better with both the Volt and the Audax with waveguide.
Example shown of modest width front baffle with 18" woofer on the side.
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The 8" Faital 8PR200 has gotten good reviews as a midwoofer.
The $64 Peerless 1" compression driver DFM-2544R00-08 can reach 20kHz.
The SEOS-12 would hold both horizontal and vertical pattern control for a 1500Hz crossover. A deeper horn like the LTH102 requires less high frequency boost.
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The 8" Faital 8PR200 has gotten good reviews as a midwoofer.
The $64 Peerless 1" compression driver DFM-2544R00-08 can reach 20kHz.
The SEOS-12 would hold both horizontal and vertical pattern control for a 1500Hz crossover. A deeper horn like the LTH102 requires less high frequency boost.
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