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Its likely that people do not take care of peak performance. If you can perform a sweep measurement at desired Peak level, as in transient peak, as in true peak, and the THD is low.... There should be no issues, don't you agree?
Once again, Lowering a X-over point and Making a Lower XO point, achievable.....not the same thing. Its about the mitigation of excursion, I think. Yes, lowering XO point will increase excursion in both situations, but in one, thought has gone into what is needed to lower the XO while keeping excursion low enough.
Its likely that people do not take care of peak performance. If you can perform a sweep measurement at desired Peak level, as in transient peak, as in true peak, and the THD is low.... There should be no issues, don't you agree?
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I agree but why optimize for content that may only be 1-5% of the content? If 85db is your average and you alow for 115db that's a 30db crest factor. 120db? How much program material even has that 30db? Same with 20Hz vs 25Hz?? Hope you find the effort worth it. They are extreme's and as far as excursion I typically just don't worry about it. In a properly designed system it shouldn't be a factor. It should be taken into account looking at the woofer for sure but a compression driver?? I can't imagine being near field and not going deaf before I hit the phase plug short of outright abuse by crossing below the recommend point. Under any normal circumstances it should not be an issues.
Have fun!
Rob
Hi Camplo,
I don't think really think minimizing excursion matters too much, as long as excursion is kept within the motor's, and suspension's, range of linear operation.
I look at it like this....
Take the lowest frequency I'm asking a driver to reproduce....I know that's where excursion will be greatest. As long as the excursion there is clean, all is good insofar as excursion is concerned.
I think the problem is asking the driver to produce too far higher up the spectrum, from that lowest frequency & max excursion point.
Some form of modulation distortion I guess....
It's like a large frequency span equals the breakup mode for high frequency extension, getting stacked on top of max excursion for low frequency extension. How the heck can that work well?
I don't think the details of my listening distance, SPL, etc are going to help you analyze anything.
The remarkable gain in clarity and simply overall gorgeous sound improvement that came from inserting small mids between the CD and woofer, can be heard at low SPL , high SPL, and anywhere in the house.....at normal LP, in the adjacent kitchen, down the hall in my office...out the front door ...you name it...newfound clarity out the gazoo anywhere at any level.
(as a reminder the CD can reach down to the woofer easily without need of the mids.)
So I'm led to believe quite simply, that decreasing span of drivers makes a big difference..
In a design where there is no other compromise that comes along with it there's no good reason to do otherwise.
You have a system and setup that does not invite many compromises, which is great. But would the best overall result be the same if the horn couldn't be as big or multiple entry or you couldn't or wouldn't use linear phase crossovers or it had to be passive?
None of that changes what works best for you, I just think it's important to keep in mind that what works best within any given set of constraints is not always the same if those constraints are removed.
All while considering listening distance riiiiight? 🤔I agree but why optimize for content that may only be 1-5% of the content? If 85db is your average and you alow for 115db that's a 30db crest factor. 120db? How much program material even has that 30db
They are extreme's and as far as excursion I typically just don't worry about it. In a properly designed system it shouldn't be a factor. It should be taken into account looking at the woofer for sure but a compression driver?? I can't imagine being near field and not going deaf before I hit the phase plug short of outright abuse by crossing below the recommend point. Under any normal circumstances it should not be an issues.
Have fun!
Rob
Why are you looking at 115db vs 85db? I know that there are exceptions but I mostly see a crest factor of about 15db over RMS....RMS can easily reach near 100db... in a movie theater, things get way more dynamic than I could of predicted
The spl meter is just capturing max recorded in true peak and max....not sure what the rms was to reach 128db true peak....most of the true peak I witnessed was about 117db.
Narrowing in on my situation of aimingfor clean 115db/1m, crossing at 200hz? Thats asking a lot. Theres the recommended point and then theres pushing the limits. If I cross at 300hz-400hz then you are absolutely right. I think you are wondering why I keep trying to go lower? Well first of all, sometimes "lower" and within "recommended" simply equates to "use a bigger horn".... eventually you are too far past the LF efficiency of the diaphragm, or rather, you run out of excursion regardless of horn size. Still all of this in agreeance with you statement...within a lot of setups, headroom of a compression driver should be able to reach 115db/1m, no problem, being that larger and lower performing set ups are less common due to cost and size. Above ~800hz a large format compression driver doesn't need a horn for high dynamics at 1m. A waveguide is enough. Keeping things closer to 85db average and allowing 15db of headroom, I can run a 200hz XO. I think I can make it to like 110db to be honest lol but its been a while since I experimented
This is a measurement I took outside with a 300hz XO....I think....I am learning look at the effective XO, not the filter used, so its not worth figuring where I actually put the filter in this measurement. I am pretty sure that this measurement was within tolerance but I do not recall the details, other than this is at 1m outside and there was more headroom than this available.
At the end of the day, the 200hz Effective XO desire for me, personally, is the summation improvement that is had by a XO so low... I guess a big part of it is the whole, avoid splitting the voice, and midrange type of thinking? Mostly getting all of midrange on one driver really. A large format CD, on a large horn, allow one to reach pretty low into the midrange to achieve some of the effect. I've first experienced it with my last setup using a 1+4+12 where the 4" covered 130hz to like 2.5khz. It works. So now with the Axi I am trying to keep the theme alive. Stepping into the horn driver plus 15" arena, 800-600hz is a very common area I think. And obviously things can work as well. I'll use the testimony of those impressed by Synergy design to remind us that there is another level of SQ achieved with singularity of sources. Time alignment, I think, can achieve similar results with a 3 way designed well....but it may be one tick shy of summing that is achieved by simply centralizing the source, like in coaxial, FR, and Synergy types. I for one conclude some type of mental image in my brain when I listen and look at a system, then I think about if what I am mentalizing is strongly influenced by what I see. I know that with my system that I have done a job because I can sit so close but the really large drivers and enclosures are spaced father than the acoustic image mentally tells me, is there. Between trying reset my "pallet" by closing my eyes and letting time erase the image of what I know is there.... I can tell that the subbass is below the treble..... it sits just under the midrange woofer, actually....The mental image it gives me might look like below, where ever parts of the music called my attention from the subwoofer only seemed to ride slightly under where I perceived the midrange to come from....Considering the distance of CTC, the close ~54" listening distance, and very small amount of time spent tuning a XO between the 2, as well as voicing... I felt like I had succeeded, Like Earl remarks earlier;
I laid on a hefty portion of "simple", simply, by not trying too hard to fine tune things and seeing what it sounded like, and its pretty great, especially considering the close listening distance and the long ctc. Theoretically I should be able to improve upon the little effort spent already, is my point. If we erase the red portion from the picture, leaving just the blue, I think this how people are mental seeing the popular synergy designs, from sub bass to treble. Time alignment, and FIR, will take things to the next level and that is where I'd be looking to compete with a large Synergy. I only look to criticize the one man experience, do not let that part be ignored, the very small sweet spot, that is.
I still don't have a horn stand in place....I'm trying not to settle, and currently am brainstorming the design. I'm almost certain I am going to have to 3d print something. I also may be able to use my JBL stands with some modifications. I still think my experiments are valid. That is, I can only play with the horns in very un realistic configurations...like pointing up at the ceiling, or leaning over pointed towards myself. In the little bit of experimentation that I've done already, my experience suggest to me that my ideas about lower frequency and localization have some truth. I am not certain now, if this idea of localization vs frequency is simply a result of room mode, directivity, lesser bass resolution/sensitivity to the ear or all the above. Either way, When I lower the XO nearing 200hz, even in the inconvenient configuration, I can perceive a type "Gelling" (to take a definite form or begin to work well). It was also this way with experimentation with the 4" crossing to the 12" (1 meter).....it was at 200hz and falling that a type of summation happened. Oh look, I think I figured it out
13550/200/4
= 16.9375
Bit of room mode and 1/4WL spacing...final answer? lol The horn is father than 16" but still this effect seems to get stronger rounding 200hz and falling.
Long story short, if I can get a lower XO to work, then it sums better. The high peak performance is desired for faithful playback at levels resembling a Movie theater....I am simply learning what my limitations are. I am not going to get as high as 120db/1m crossing effectively at 200hz, but I can do so at lower volumes, and thats a win for me since lower, in this case, is within what many would call, "plenty". With a higher effective XO like ~350 and above, 120db is achievable. Though, it should not sum as well as the Synergy... I guess I am saying that if it can get down to 200hz, it is "synergy enough" to be on par, regarding summation. I also do not think there will be an issue of Accuracy, due to excursion, when volume is kept below a certain true peak. With excursion staying below ~0.5mm as well, within the supposed ~0.8-0.9mm linear travel how could IMD be an issue?
Is it possible treble has a less tolerance to even slight mm of excursion or is it possible the spreading of signal removes heat that effects accuracy. No idea, but maybe me and @mark100 could compare Modulation distortion Test at some point. The lower I place the XO, I can watch modulation distortion rise, using REW. more important is where do we draw the line for where perception kicks in. Then, I would have think about whether its the excursion literally, as in intermodulation distortion or due to machinal strain. In the end, to me, its all excursion derived, and not anything to do with how much spectrum is on one driver.
Lowest frequency and max excursion? That is a matter of excursion, I assure you lol....Lower excursion, lower modulation..... modulation is simply to excurt from one side to the other, as far as the diaphragm is concerned...Given the small ports used in synergy I predict a huge loss in efficiency thus increasing excursion. Of course adding drivers sounded better.....There is an aspect of Accuracy that I attribute to excursion no matter what the motor and suspension is doing. "from that lowest frequency & max excursion point.
Some form of modulation distortion I guess....The ports on those 4" are tiny. About an inch, per, is it not? Excursion at 115db starting to get near 1mm. The dual 10's have about 2" sq inch per hole?
Compared to what? If we attribute the differences to excursion, it fits. Too bad you don't have a large horn to experiment with....The B&C horn with a 300hz fb that should only be used to about 600hz...that aint it. Your Syns are 36" wide, moving directivity lower in the spectrum. Even if you were to cut the Syns off at 600hz and compare it would not be exactly a fair fight would it? At least excursion would be much less due to crossing over away from fb as one should.
At the end of the day, you still end up with more LF, and a wide HF polar, and great headroom....so yeah, its a great deal. I think I am trying to keep up with out actually building a Synergy lol.
To reach towards 120db true peaks at a father distance, like 10ft, might cause me to have to raise my XO even higher.
I am not trying to "outshine you" btw, I just am, as usual, learning from the discussion and the compare and contrast of ideas and specs and measurements, etc etc...You've definitely helped me to be a better designer and I am continued to be impressed with your knowledge and experience.
The late great Paul W. Klipsch would have definitely disagreed with you on that point...
.
The thing is the mains are so big, it only makes sense to match excursion character with any other woofers I match with the mains. By that route alone, I am within the territory of achieving 115db down to 20-25hz at 1m, as a bi-product. Looking at "The Hulk" as an example of some random but "basic" action movie.....20-25hz cutoff looks pretty good to me. Jbl cinema subs fb is 25hz....there is a trend there, likely supported by popular system design and Content design. Why go against the grain? A system with a higher cutoff than 25hz is below par. 115db isn't enough to keep up with the Theater so why act as if something I am doing is extreme? Spreading bass sources in the sound field, on the horizontal and vertical axis, improves FR. Whats not to love? Do you not like the sound system at the movies? Do you wear...ear plugs at the movies? Do you take a spl meter with you, to the movies.....do you go....to the movies lol???
I mean if GM landed pretty much within the same territory of dynamics that the system I've designed with the boards help..... thats confirmation enough for me. Sounds like I've made good use of the information shared in this thread. GM says he found diminishing returns at 117db/1m....thats 2db higher than I claim I am aiming for....since I am truly trying to hit 115db at half Xmax on the accumulation of subs, I am pretty much still in the ball park. Headroom and efficiency is strongly tied to Accuracy of a system. IF Gm found the top of his perception at 117db capability. Theres a big chance that the rest of us are more similar than different. As you properly increase headroom, you usually increase Xmax and lower excursion in effect.... There is an noticeable increase in system accuracy as headroom moves up until a certain point... 115db/1m is logical territory and getting that in 1m with synergy like summation before FIR, with a fairly naturally smooth FR, is the Cake. Having a 25hz system cutoff is the Icing
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I think he meant more words than he used....I think he means excursion isn't isn't the problem as in within xmax and machinal limitation but rather, max excursion achieved by driver, sets a sort of, HF cutoff, where a loss in accuracy becomes perceivable. To which I think is already understood isn't it? I do recall @gedlee saying something along the lines, that Some other distortion has set in long before IMD is perceivable....Maybe he can speak on, what it might be that Mark is experiencing.The late great Paul W. Klipsch would have definitely disagreed with you on that point...
In some of my experiments, I'd set a tone, at say 12khz or 14khz, whatever, 7khz....and then sweep another tone, heading towards sub bass, and listen, using REW, while watching the IMD metric on the RTA.
Lets say that as long as we are within Xmax, a wide band driver handling all HF.....how many different places can a diaphragm be at one time really.....It only makes since to me that a diaphragm that can only exist at one place at a time, could only support so many frequencies at one time, accurately, as required by our media, if excursion is kept low, regardless of Xmax. How low? I dunno....0.5mm??? 2mm??? maybe this is simply made more noticeable from HF content on the same driver.
Tom Danley - "One problem with loudspeakers is they add "free sound" in the form of harmonics of the input signal, noise and delayed radiations of of the signal. The first two problems get louder faster than the sound from the input signal and so "headroom is your friend"."
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Yep, who knows what the overall results would be without the combination in play.
I try to isolate variables in a logical order, where there is a foundational hierarchy to them, but as everything in audio evolves compromise, it's hard to really know what factors are prime, when.
I do tend to think that a synergy vs a conventionally baffled multi-way is a prime root though.....simply for the tighter driver spacing a synergy offers.
But a complicated to build, comparatively ugly, synergy is a compromise for sure.
But conventional baffles are a compromise for sure too.... I can see why folks stick to 2-ways with them, and simple passive xovers......if for no other reason that to solve c2c spacing dilemmas posed by more mult-way
Hi DavidThe late great Paul W. Klipsch would have definitely disagreed with you on that point...
,Why you wanna chop off my qualifier about excursion not being an issue?
" as long as excursion is kept within the motor's, and suspension's, range of linear operation."
Personally, I like to use about 1/2 rated xmax as the design limit for highest SQ.
But that's just based on seeing how Klippel often reports slippage out towards xmax, and not really knowing exactly when excursion matters.
I like to design for 20 dB of headroom. All the live and studio gear I've seen, generally sets the 0dB analog equivalent mixing level level at about -18dBFS.
So I figure 20dB is a pretty good number.
The clarity gains I hear from adding the small mids are in comparison to other similar size/pattern synergy horns that cross the CD str aight to the woofer.
And on this particular build, compared to itself .......with and without the small mids
Here's the raw response of the sections... Blue =10"s woofers; Green = 4" mids; Red = CD HF section; Orange = CD VHF section.
As you can see, the CD reaches down to the woofer just fine without need of the mids.
I've listened to it that way vs inserting the mids, where both setups have close to identical flat mag and flat phase response
(Switching between the two setups is instantaneous and silent...gotta love QSys !)
Again, I don't know why the mids add so much clarity, other than to suspect some form of IMD or other type modulation.
Could it come from simply the CD having less excursion by raising it's xover point.. Sure..I think probably so.
But I'd like to have a measurement that shows such. I've played with IMD and multi-tone and speech intelligibility measurements, but frankly still don't know how to interpret them.
I guess the clarity could also come from the woofer not having to play all the way up to the CD. Since it's excursion doesn't change no matter where crossed higher, it seems if any clarity gains come from the woofer, it would have to be from reducing its upward span.
Related aside: I know folks have long advocated trying to keep vocals xover free, within the span of a single driver.
And i think that has made a lot of sense given the historical use of IIR xovers.
That said, with linear phase xovers I think you can put xovers and multiple driver sections, anywhere in the vocal range without issue.
(of course assuming a good acoustic design.)
I have used recently a Dynavox LW5004PMR-N 5-1/2" Poly Cone midwoofer which has a nice FR curve from 100 Hz to well over 2000 Hz. So it handles the whole vocal range negating the need for an xover until well above it. It features a 3" VC and nice "dome" cap, giving it the dispersion characteristics of a dome, and the added cone area around it is enough to get down to 100 Hz without the diffraction some traditional cones might introduce. It has good power handling and the vocals are very smooth overall, avoiding the harshness some drivers will exhibit with certain singers or recordings. Think Shirley Bassey from Goldfinger days, this will grate your ears without smooth vocals in the driver. It can be crossed wherever you like for a 2-way design, depending on tweeter selection, and I supplement it with a sub (so really a 3-way overall). It's not super expensive. Having a 3" coil in this type of driver is pretty uncommon.
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Hi David
Why you wanna chop off my qualifier about excursion not being an issue?
" as long as excursion is kept within the motor's, and suspension's, range of linear operation."
Hi Mark,
I was thinking of the document linked below when I made my comment.
http://www.readresearch.co.uk/loudspeaker_papers/klipsch_modulation_distortion_article_1.pdf
Paul Klipsch felt that it was desirable to reduce diaphragm displacement even within the linear excursion range. I guess it is understandable given that for commercial reasons he would obviously have been keen to promote the merits of horn-loaded loudspeakers
.Kind regards,
David
I wouldn't so much lean on that, but due to the use of the same horn they have pretty good 'pattern matching'
On the other hand, that is also possible with a two-way. Also the shape of synergy horns is often guided by 'other' concerns.
Hi again David,Hi Mark,
I was thinking of the document linked below when I made my comment.
http://www.readresearch.co.uk/loudspeaker_papers/klipsch_modulation_distortion_article_1.pdf
Paul Klipsch felt that it was desirable to reduce diaphragm displacement even within the linear excursion range. I guess it is understandable given that for commercial reasons he would obviously have been keen to promote the merits of horn-loaded loudspeakers
Kind regards,
David
Thank you for that paper....hadn't seen it before.
If I understand the paper correctly, it appears that the two principal factors behind modulation distortion are the amplitude of the excursion, and the frequency span of the driver.
(That sure squares with my ears, and my speculative understanding)
I particularly enjoyed his "mud index" !
I've built Tom Danley's FLH Labhorn design, and can attest how much cleaner they sound, how reduced harmonic distortion is, vs direct radiator subs that aren't excellently designed (with Hornresp
) and with excellent drivers.I think the same "mud index" principle shown for subs, is at work all the way up to the top of the spectrum.
Give me multi-ways, and the more the better !!!!