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Posted by boiklox on
01-16-2014
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fiogf49gjkf0d This is my first horn build effort. Been thinking about this since starting to build loudspeakers and finally have a listening space big enough to support a horn system.
This is where I am at now, I know there are opportunities for improvement. And I'm thinking about how to develop my system for the future and build it out into a proper four or five-way system.
Current: - 40 Hz - 1000 Hz: JBL 2226J in BR Enclosure (not ideal).
- 1000 Hz - 9000 Hz: JBL 2445J in 250 Hz Stereolab Tractrix horn.
- 9000 Hz - 20,000 Hz: JBL 2405 (not seen in picture, need to build a frame to support and suspend the 2445).
Thinking about time alignment. Current crossover is a quasi-optimal, asymmetrical 3rd order butterworth/butterworth at 1 kHz. 2226/2445 crossed actively with a miniDSP (not ideal, will build out passive crossover when I "arrive" at a semi-final place). 2405, passive x-over 12 dB/octave.
300b amp drives the 2445 and 2405, SS Rotel for 2226.
To dos: - Need to build a frame to suspend the midrange horn higher, position 2405 in-between.
- Decide and build a mid-bass horn.
- Decide and build a upper mid-range horn (maybe a 600 Hz tractrix?).
- Decide and keep/replace tweeter?
- Decide what to do about bass? (no ports in future!).
- Decide what to do about crossovers and amps (6 dB/octave passive is goal).
- Time alignment.
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Posted by Romy the Cat on
01-16-2014
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fiogf49gjkf0d Danvprod,
I hope you understand that “proper four or five-way system” is some kind of Unicornnish type of animal and we could talk about it only abstractly. Still, since you have mentioned it – what and how are you trying to accomplish with your five-way objective? The reason I ask is because there are zillion ways to do it and they all would be different topologically, financially and hematologicaly.
Regardless your responses here are a few comment about your Dos:
I would not build any frame at this point, at least until you know exactly how many channels and what kind you would like to hang on the frame. The Midbass horn (or most likely an upper bass) is a great project, if it were up to me I would start anything from it as I consider it as the “foundation” of all system. The upper mid-range horn? This is complicated; way do you feel that you need it? You can slice another 22 channels but do you need them? I feel that the presence of a dedicated upper mid-range design from the type of MF driver you use. If your driver does not go over let say 5kHz then you might have another upper mid-range. So, make a final decision about your MF driver and see if you even need/want upper mid-range. Be advised that your preference to MF driver will fluctuate as you progress with your installation. The replacement of tweeter is not the tweeter’s subject. Find the MF driver that you like and THEN, only then find a tweeter that will be able to work with that MF driver. I do not know what you will be doing with bass and many bass channels you desired to make. For sure ports are garbage but if I were you I would not invest any efforts in Bass at this point. I would not think about amplification/crossovers at this point as well. You many times over will override the decision you made at this initial point. Have a good SET that you like with multiple taps in output transformer. That is all that you would need to start.
Rgs,
Romy The Cat
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Posted by Jorge on
01-16-2014
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fiogf49gjkf0d Hello Dan,
Love how you pass that cable through the port, I used to do that too...long time ago.
Why are you crossing your 250hz horn all the way up to 1 khz?
The 2445 should be able to go much lower.
Have you measured the response you are getting from the horn?
Get an RTA and measure what response can you get out of that horn-driver configuration.
I am sure you can get down to at least 500hz, It probably wont go much higher than 6 or 7khz but you got your tweeter for that.
This will free the woofer from playing all the way up to 1khz....
It should sound better.
If you want to go crazy try the horn-driver combination by itself full range at very low volume and see how far down it can go and still sound
good. A 250hz horn is a big one and should go lower, the compression driver is the one that will have trouble.
Maybe get a phenolic diaphragm and make it go down to 300hz and a midrange horn from maybe 1khz up to the tweeter.
If you are into JBL there is a phenolic phram driver out there people swear by, forgot the number.
Get rid of the minidsp and buy a bunch of caps and coils! (not the ribbon ones)
Of course an upper bass horn (100-120hz) is always better...
Just my 2 cents
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Posted by boiklox on
01-16-2014
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fiogf49gjkf0d Romy,Your Macondo system is something that has been a "role model" for what I'd like my playback system to be in the coming years. And much of what I've learned about horn playback systems I've learned from reading your writing and other posts on this site. And thank you for your response.
My objective is to create a system that is able to emotionally re-create music in a powerful and realistic way. My greatest memories are playing in orchestras and sitting in the middle of the violin section with a hundred other players on stage creating music and being completely engrossed by sound. It's magical. That is what I am starving for in my playback system. My system has been organically growing the past two years. The first "ah-ha" moment was vinyl, then tubes and now horns. So I think (I hope!) I am on the right path.
In response to your comments about my to dos (and thank you, a lot of things to think about).
For the time being, I think it is important to be able to arrange the speakers: Woofer -- Tweeter --- Midrange, so I will have to build a bracket to elevate the 2445 up about 12-16", this will let me position the 2405s at ear level, underneath the midrange. And I want to position the VC of the tweeter in line with the midrange. I'll plan on putting some foam on the underside of the horn and on the top of the woofer cabinet to absorb some reflections from the tweeter to these surfaces.
Upper bass is the next project for sure. That will likely give me the biggest "bang for my buck" so-to-speak. Any suggestions on what I should do there? Agree with you about this channel being the foundation of the playback system. Could my JBL 2226 work for this? Or should I consider another driver. You use the Fane Studio 8m for this purpose, correct?
Here is a measurement (gated in-room at 1m) of my current system (without tweeters). The 300b SET amps that I have currently, I like a lot. The output transform has a 8 and 4 ohm tap, I'm not sure if this is what you mean.
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Posted by boiklox on
01-16-2014
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fiogf49gjkf0d Hi Jorge, Thank you for the response. Re: cable, yes I've been too lazy to install binding posts in the back of the cabinet.
I have no good reason, necessarily why I am crossing the 250 Hz horn at 1k. I posted my measurement above, but of course this is with the 1k 18 dB/octave filter.
Here is just the 2445, with the current crossover. I think you are right, 500 Hz - 7 kHz is prob the range. So would you just do a first order bandpass here from 500-7000 Hz? And then a first order LP at 500 Hz for the JBL. I will still have the problem of time-alignment, with the woofer 8" in front of the horn.
I will look for the phenolic.
And yes, a upper bass horn is always on the table.
And thank you for your 2 cents, very good things to think about.
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Posted by mats on
01-16-2014
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fiogf49gjkf0d Good start Dan!
The JBL phenolic 2" driver is 2482.
I would lower the crossover point as far as you dare, 300Hz or so.
Now the 2226 will do what they are pretty good at.
Later you will likely want to filter the 2445 around 2k.
A 600Hz horn with a 1" driver, hopefully with a sweet diaphragm, I prefer phenolic, will take over.
Some day you may go for a tweeter.
I use a sealed cab from 60Hz with 15"driver, and a subwoofer below.
Alnico magnets plus phenolic diaphragms has given me the most joy so far.
Good luck, and enjoy this trip.
Lots of good information here, and helpful folks.
Mats
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Posted by KLegind on
01-17-2014
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fiogf49gjkf0d  mats wrote: | Good start Dan!
The JBL phenolic 2" driver is 2482.
I would lower the crossover point as far as you dare, 300Hz or so.
Now the 2226 will do what they are pretty good at.
Later you will likely want to filter the 2445 around 2k.
A 600Hz horn with a 1" driver, hopefully with a sweet diaphragm, I prefer phenolic, will take over.
Some day you may go for a tweeter.
I use a sealed cab from 60Hz with 15"driver, and a subwoofer below.
Alnico magnets plus phenolic diaphragms has given me the most joy so far.
Good luck, and enjoy this trip.
Lots of good information here, and helpful folks.
Mats
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Hi, I have some experience with the 2482. Sure it can reach 300 Hz but only with EQ. It has a semi hard lower knee slope so you are never going to reach 300 clean. If you have a x-over simulator for passive, or digital EQ, go for it, but I really don't see it reaching 300 with any confident sound.
Maybe one could soften the phenol suspension and add shims to get away from the phase plug - that would be interesting... It was never a high frequency driver anyway.
Best
Kris
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Posted by mats on
01-17-2014
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fiogf49gjkf0d Kris, I agree with you about the unobtainable 300Hz.
Had really hoped for that, but so far no go with my set up:
An old Oris-150 with a 4" throat wood adapter/cradle that John Sheerin made for me,
with the 2482 playing out the back, so you see the entire 4" phenolic diaphragm. Room logistics inspired this solution.
I'm not sure it is ideal by any means, but it works fine.
I can use a relatively large coil, 6mH, on my TAD 1601b. They measure 6.5 ohm.
The 2482 is filtered with a first order PLLXO at 300Hz. This should likely be raised a bit.
I wonder if an exponential horn would raise the bottom slightly?
Also, what could one expect from returning to the 2" throat?
I know nothing about loosening suspensions.
Mats
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Posted by boiklox on
01-17-2014
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fiogf49gjkf0d @Mats -- Thank you! This has already been the best sounding system I have built and designed, but hearing how good it sounds, lets me know how good it can be in the future. Thank you for the info on the JBL 2482. I've considered swapping the diaphragm with a Be 'phragm, but the phenolic also sounds like a good idea.
I think I will drop the x-over on the 2445 at least by an octave this weekend and see what happens. I'll have to run the 2445 a bit higher than 2k for now, since the 2405 won't go that low.
But also good suggestion on the 1" in a 600 Hz horn to fill that gap.
@Klegind -- Thank you for the info on the 2482. EQ is not something I want to do, so maybe I need to push the 300 up to 500. We'll see how it measures. I also thought that the "rule of thumb" was to have the x-over about an octave higher than the horn cutoff.
@Mats -- Interesting on your system, I'd love to see what you've built and how you've designed the electronics. Do you have a build-log here on this forum? Good idea with the PLLXO, I've not thought about approaching the x-over this way.
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Posted by Romy the Cat on
01-17-2014
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fiogf49gjkf0d
| danvprod wrote: | | My objective is to create a system that is able to emotionally re-create music in a powerful and realistic way. My greatest memories are playing in orchestras and sitting in the middle of the violin section with a hundred other players on stage creating music and being completely engrossed by sound. It's magical. That is what I am starving for in my playback system. My system has been organically growing the past two years. The first "ah-ha" moment was vinyl, then tubes and now horns. So I think (I hope!) I am on the right path. |
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I do not want to disappoint you but I do not think that anything that you do in audio would able give you the captivation and attention you get from live sound. If you think that I would be able to pitch to you some kind of cable elevator, speaker topology of tube brand that would do that magic switch then you are mistaken. I think you mislead yourself by expecting this from Audio. Audio is very interesting and much more complicated tool then most of audio people understand. Audio is not about re-experiencing but rather about re-conceiving. It is a big subject and I do not want to go into it here. If I were you and I would embark in many years and thousand dollars project then I would like to see if any light in the end of tonal. Did you hear any horn inhalation that you like? Did you feel that the audio result that you have heard did deliver to you that state of engrossment that you would like to pursuit? If you feel that my inhalation shall do it then spend a fraction of cost that your project will be, fly over and listen yourself. It is possible that you would not find it not worth to be bothered or the efforts that need to be spent is not reasonable.
| danvprod wrote: | | For the time being, I think it is important to be able to arrange the speakers: Woofer -- Tweeter --- Midrange, so I will have to build a bracket to elevate the 2445 up about 12-16", this will let me position the 2405s at ear level, underneath the midrange. And I want to position the VC of the tweeter in line with the midrange. I'll plan on putting some foam on the underside of the horn and on the top of the woofer cabinet to absorb some reflections from the tweeter to these surfaces. |
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Yes, the arranging of the channels is important but from how I see it now if I do not have any playback and my objective were to have one then I would first start from space analyses. I am not taking about running RTA in the room and figure out what and what is not good but I rather to look at the room from a holistic perspective and decide what kind of acoustic system the room would be able to accommodate and what kind acoustic system topology would be the most beneficial in the given room.
| danvprod wrote: | | Upper bass is the next project for sure. That will likely give me the biggest "bang for my buck" so-to-speak. Any suggestions on what I should do there? Agree with you about this channel being the foundation of the playback system. Could my JBL 2226 work for this? Or should I consider another driver. You use the Fane Studio 8m for this purpose…. |
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The selection of a driver is irrelevant in my view. You need to conceptualize what kind of acoustic system you would like to have. If, again if, you decided to have something Macondo-like then you ruled by the uppperbass’ throat. I went for 4” and it was very strategic decision. In Macondo configuration you would hardly be able to accommodate a horn larger then 140”. The 140” is 110Hz to 150Hz, depend of the room, projected to 4” fast opening throat it is about 6dB equalization at bottom knee. The smaller throat is longer horn, more equalization and slightly different sound. The same with the larger throat – size and sound will be consequences. Plus there are consideration of attractiveness and finicality… I would start thinking about uppperbass first….
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Posted by Romy the Cat on
01-17-2014
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fiogf49gjkf0d | mats wrote: | | I wonder if an exponential horn would raise the bottom slightly? |
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Yes, a move from tratrix (or La profile) to exponential profile will yield some raise the bottom, however it come with prolonging of the horn and in some case it would make time-alignment impossible. Also, the character of the bottom knee sound is slightly different between the fast and slow opening horns and it is not only subject of amplitude.
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Posted by Jorge on
01-17-2014
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fiogf49gjkf0d Just a quick note.
I tired a JBL 3" compression driver 2490h model with original Titanium diaphragms on a 120 hz Tacrix horn. I got a response down to 200 hz.
How did it sound? It sounded good clear and transparent but it lacked a little tone imho.
The Fane on the same horn goes down beautifully to around 120 hz, with a great tone and unexpected punch... I can play disco music and bring the house down, it turns out I never do...
Anyway, the Fane was better in every respect to the CD on that range.
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Posted by Romy the Cat on
01-24-2014
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fiogf49gjkf0d ltsv38,
it is an interesting solution for lower midrange horn. If I use something like this for Macondo ‘s fundamental channel (but of cause spherical) then I would flip the horn with driver up and run the neck longer to accommodate a slower, exponential-like profile. The objective would be to get the same 250 cycles but more by the horn EQ then the driver extrusion. I do not know the 2482 driver but all of the 2” exit drivers have in my estimation some unpleasant behavior as lover knee when you stress them to go very low. They might produce sound pressure at marked lower knee musically they do not do well dynamically when they stressed to go very low, they developed some mild, and some of them not mind, compression. I think the reasons is because the drivers are optimized to deal with 2K-5K and the spaces in the driver and within the phase plug are to too small for higher pressure of the longer waves. So, as the driver pumps more at lover knee the bouncing pressure from phase plug over damps the diaphragm. ltsv38, no one would tell you if you have this effect and you need to see of your lover knee of your 2482 channel (lower midrange) sounds as dynamic and your upper knee of your uppperbass channel.
Rgs,
Romy the Cat
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Posted by ltsv38 on
01-24-2014
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fiogf49gjkf0d | Romy the Cat wrote: | | I do not know the 2482 driver but all of the 2” exit drivers have in my estimation some unpleasant behavior as lover knee when you stress them to go very low. |
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Hi Romy
JBL 2482 was mainly designed for very high power public address in a wide range application (voice / 300 Hz to 6 kHz ): diaphragm is weighty and suspension is flexible compared to other 2" drivers. My opinion is that, associated to an appropriate horn, it can be used from 200Hz for domestic application but it must be coupled to another driver above 2 or 3K (1100Hz in my system)
Another solution for such an application could be the ALTEC 288?
Regards
Pierre
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Posted by Romy the Cat on
01-24-2014
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fiogf49gjkf0d Pierre, yes, I understand it. It kind or irrelevant what they destined for and yes, in domestic applications in context of low power we can use it lower. What I am saying is that as we do use it at extreme low range we deal with slightly overdamped diaphragms.
Just think about it. The excessive pressure of that is generated by the driver diaphragm excursion needs to be dissipate somewhere. The diaphragm is 1-2MM from the phase plug and as diaphragm does let say 100Hz then there is very minor acoustic feedback from the phase plug. As the diaphragm does 200Hz then there is much stronger acoustic feedback over that 1MM from phase plug and the super light diaphragm does experience some reactance from it that in my view manifest itself in dynamic compression. I do not know if it happens in your case and I am talking about not about your case but rather about generic concept.
I personally feel that it is a good idea to use drivers in the zone of comfort where they are not stressed. The best bet for me is to consider if the driver can handle lower crossover then it meant to handle. For instance you use 3rd order can the same driver use 2nd order. If not then it might be that the driver is overstressed at the bottom. It might be not the case but it uselessly is.
It is a bit tricky to assess if the driver is stressed as the bottom. You might take a good played quartet but preferable not contemporary recording but something from 50s. Pay attraction how viola and cello grow affected by the octaves. Disconnect other channels and listen only your 2482 channel. As the tone goes down sound shall not loos structure and shape, shall not become fizzy or hollow, shall not change speed unless it untended, shall not obtain or loos testerone, shall decay evenly. I can give you other dozen examples of what it shall and shall not do, but it is not the point. The point is that somewhere down does Sound WILL lose ground. You need to add you’re complementary uppperbass channel, whatever you have and then to repeat your observations. The most important point in here is to have absolutely no event of any kind during sound transition between 2482 channel and uppperbass. You shall not have it even during “sit-down test”.
Using different drivers that I was trying to stress at lower knee I always concluded that my uppperbass was more vivid them the lower knee of my MF. As I rising up the crossover point for 50-100Hz up on my lower MF (that I call Fundamentals channel) and rising up the crossover point at my uppperbass I felt that I have more smooth transition with less “events”.
The 2482 might be different, I do not know. Generally I find that dropping compression in the driver was helpful a bit. I was very slightly open the back chamber of the driver that gave to me some ease at lower knee.
It is also important to differentiate when a driver is choking with wham the horn is choking by driver. In case or Macondo I was rather restricted by horn size then driver but I have chosen to keep this way as I have an expendable uppperbass that does fine upper knee.
Rgs, the Cat
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Posted by haralanov on
01-24-2014
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fiogf49gjkf0d | Romy the Cat wrote: | | I was very slightly open the back chamber of the driver that gave to me some ease at lower knee. |
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Congratulations you have found and use this principle, otherwise the back chamber acts like pneumatic brake for the lower working range of the diaphragm!
If you want to squeeze the last drop of performance out of the compression driver, you need to effectively "attach" some air to the back of the cone, to compress it, and then to gradually release and absorb the energy of the back wave:
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Posted by Romy the Cat on
01-24-2014
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fiogf49gjkf0d | haralanov wrote: | | Congratulations you have found and use this principle, otherwise the back chamber acts like pneumatic brake for the lower working range of the diaphragm! |
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Actually it shall act as “pneumatic brake” in a compression driver and the brake has to be tuned well under resonance of the driver. However, do not use word “brake” as it if from the words of mass-centric drivers. Horns are not about mass and exertion but about velocity and consequential pressure, so in horns there are no brakes but rather damping over rate of velocity change. The mechanism you depicted and I “found” is being used in headphones for years, very effectively. I have to note that very mild relaxing of a back chamber in compression drivers is NOT a universal solution and it works only in some applications and ONLY for very narrow bandwidth. In some cases if your channels cover let say 2 octaves then your drifty back chamber might e benefited for lower knee of those two octaves and act harmfully for higher octaves. A good driver in own secure and comfortable rage shall be back-sealed.
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Posted by haralanov on
01-25-2014
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fiogf49gjkf0d | Romy the Cat wrote: | | However, do not use word “brake” as it if from the words of mass-centric drivers. Horns are not about mass and exertion but about velocity and consequential pressure, so in horns there are no brakes but rather damping over rate of velocity change. |
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This is true only for a theoretically perfect horn, where the diaphragm is loaded symmetrically in both directions. The small closed chamber loads the diaphragm very differently than the horn in front of it, and it acts exactly like a brake, not to mention the influence of the sonic soup of air born resonances that are formed inside that chamber.
| Romy the Cat wrote: | In some cases if your channels cover let say 2 octaves then your drifty back chamber ... act harmfully for higher octaves.
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In all cases - it is exactly the opposite :-))
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Posted by Romy the Cat on
01-25-2014
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fiogf49gjkf0d I also disagree. You circumvent the whole theory if compression drivers. The whole point in a compression driver is that anything in back chamber is irrelevant. Haralanov, all that you need to do is to make your own experiments, the practical experiments. Take a dozen compression drivers and play with back chamber. You will learn that it will have minor effect to the very bottom knee and practically no impact to the normal operation range of the driver.
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