Unfortunately, I do not know this value in numbers. The description for my speakers says this:
Output sound pressure level 95 dB/W (new JIS)
But it seems to me that this is indicated by the sensitivity of the acoustics, but not by the sound pressure ... Or is that what you had in mind? If so, then the sensitivity should be at least 95 dB, because in the future I want to use a tube amplifier, which I also want to make myself.
🙂
Thank you very much!!! I'll be studying this all night! This is very interesting and useful for me.
There is a saying in Russia: beginners are always lucky. Besides, the world is not without good people - I believe in it. For example, I have already found good people - you help me, and this is the main thing for me. I can always show you drawings and calculations, and you can always correct me.
Don't misunderstand me: you need to do it right the first time and the way you want, or don't do it at all. Experience comes with time, and I know that this project will not be one day. At least a year. I've been fiddling with super tweeters for almost a year. I spent four months inventing a design, drew 6 options, and only the last one made me wince. When it is completely ready, I will post a photo in the thread of this forum in which I asked questions.
To achieve a wide listening area there is multiple approach.
To me the best is to target Constant Directivity (CD). This is Earl Geddes or Wayne Parham (Pi Speakers) approach.
http://www.gedlee.com/Papers/directivity.pdfhttp://www.gedlee.com/Papers/Philosophy.pdf
https://www.pispeakers.com/Pi_Speakers_Info.pdf
Is this approach compatible with a vertically aligned system? Well both choosed a different approach (as Jbl ( Theater/cinema system) and others too.
But that does not say it is not possible.
I think Stv talk about Atc philosophy. They constrain their design goal to use drivers in the pass band where they radiate omnidirectionaly( ka:2 max).
This gives a loudspeaker which have a uniform radiating pattern for the most of the range ( there is narrowing in the high end though) but it spread very wide whereas CD constrain the radiating beam to a defined area. It does change the rendering as the interaction with the room is different between the two.
What you call D'Appolito* should behave to the Atc camp if there is no way to control the directivity on the tweeter ( iow if no waveguide is used).
A kind of loudspeaker which is vertically aligned and use a waveguided tweeter is Snell Xa reference designed by Dave Smith ( he was active here as SpeakerDave)
https://www.stereophile.com/floorloudspeakers/556/index.html
https://www.tnt-audio.com/intervis/david_smith_e.html
As can be read from his interview the waveguide is not used for constant directivity but he target a wide listening spot however as design goal.
There is many ways to skin a cat...
Dunlavy's are in the Atc camp too. It is worth reading why he decided to choose this kind of layout too:
https://www.stereophile.com/interviews/163/index.html
Kyle Neuron is spot on about d'Appolito limitation and if you study Horbach-Keele paper you'll see what he meant.
This article should help too:
https://www.birotechnology.com/articles/VSTWLA.html
*D'appolito configuration is often used as a general description for verticaly aligned systems but what D'Apolitto implemented is an MTM with initially 18db/octave filters which he then switched to 24db/octave. This is nitpicking but...
My warnings are not about the theorical side of things but the built. You'll need some serious carpentry skills, tools and space.
It's not impossible as some members here show masterpiece regularly but i would seek input and advice from members like Noahm Geller or Mark Kravchenko or,... one of those master carpenters.
That's quite a challenge and will narrow down choice of suitable drivers (mainly: woofers). Depending on baffle step you will need a bass driver around 98 dB sensitivity.
You will need high efficiency pro drivers. Those will not easily go down to 20 Hz.
Or you decide to drive your woofers actively.
That appears to be the sensitivity, db @ 1w 1 m. That should easily be achievable from 54 hz up, but the subs are watt hogs. That is not a problem in a market with 2000 W solid state amps for $500. You even up the sub channel to the mids & tops by having a lot more power on it.
You dayton dc380-8 has fs 19 hz qt of 0.3 and vas of 13.8 cu ft, which is good for a 20 hz sub, but it only allows for 100 RMS watts. You haven't said yet how big a room you will install the speaker in or how many people will attend. Larger requires more watts, people's clothes soak up a lot of power. The eminence Lab15 allows 600 w rms and costs 3.2 times as much as the dayton dc380-8. No B&C 15" (380) driver I looked up was suitable for f3 of 20 hz, but their 18PS100 has Fs 30, qt .39 & vas of 245 L or 8.6 cu ft., RMS power 700 W. With that qt the 18ps100 could be used in a sealed box which could be smaller than ported.. An 18" is even bigger than a 15" of course. DC380-8 sensitivity is 92 db 1w1m, Lab 15 is 88 db 1w1m, 118ps100 is 96 db 1w1m.
Maximum sound level shouldn't exceed 120 db to prevent ear damage. db power is 10log(p2/p1) so to go up from 95 db to 115 db you need to go from 1 watt to 100 watts. 250 w versus 1 watt gets ~120 db from 95 db 1w1m. Those are anechoic chamber response, the way the speakers are measured for the datasheet. Loudness in a room full of people will be much worse at the back of the room, requiring more watts. One reason speakers in bars & auditoriums & outside are installed high, to even the distances between all the audience members and avoid blowing out the ears of the people in front.
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Since just in my case, a super tweeter with a waveguide will be used. I already ordered it. Here is its name:
Viawave GRT-145W-8
@krivium ,
bow to the ground to you! For the work done, that you carefully put everything on the shelves, and even to me, who does not speak English well, everything is clear. Thanks again!
I read and understand that I chose the right direction, I just need to study the material more before taking on something physically. Thank you thank you thank you! 🙂
bow to the ground to you! For the work done, that you carefully put everything on the shelves, and even to me, who does not speak English well, everything is clear. Thanks again!
I read and understand that I chose the right direction, I just need to study the material more before taking on something physically. Thank you thank you thank you! 🙂
During this week that I was absent, I thought a lot. And now I am inclined to agree with you, I am taking on a project that is too tough for me. On my own, alone, I will not pull out this project. However, I am stubborn. 🙂 I still dare to make a masterpiece. I hope I succeed. 🙂 And it will sound better than my Diatone DS-90C.
I already understand it. 🙂 What I want, and I want exactly this: woofer - midrange - tweeter - midrange - woofer, and on four 15 inch speakers it turns out very very expensive. 🙂
Putting aside the fact that I'm trying to bite and chew on a rock and imagine that I can get it right, what speakers would you recommend to use?
Thank you for your work and help!
Believe it or not, my listening room is only 18 square meters. 🙂 And the amp I'm currently using is Threshold T200. Here is a photo of my system ():
Attachments
I have no experience with such loudspeakers, but i would suggest looking at troels gravesen's projects with 15" drivers. If i remember correctly you want to use valve amp, so 4 ohm version in series (resulting in total 8 ohms) may be sensible.
http://www.troelsgravesen.dk/Faital-3WC-15.htmhttp://www.troelsgravesen.dk/The-Loudspeaker-III.htm
You should definitely model your speaker in software (vituixcad?) before choosing drivers, this is even more important with your symmetric driver arrangement.
All the drivers to build a system of yours are already at grasp of your hand. Diatones may serve a purpose of a parts donor, so build a new cabinet and put your x/o design abilities to a test. This is the most logical course of action I can think of right now. Failing to design a good sounding loudspeaker should be enough of a proof to direct you in search of a kit.
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It uses EighteenSound 15W700/8 woofers, which have a frequency response of 38Hz. And I need from 20 Hz.
Colleagues, sorry for the stupid question: if the speaker is not cut off at the lower frequencies with the help of a crossover, but only at the upper ones, won’t it already reproduce the sound below the declared 38 Hz if there is a sound lower in the recording, for example, 30 Hz?
This is the easiest way, but there are nuances in this method: that's why I want to collect something new and my own, because there are problems with Diatone. From old age. I took measurements and the THD level at a frequency of 7 kHz reaches 15%. It's a lot. By ear with the new amplifier, these distortions are almost inaudible, but the microphone picks them up.
Thanks for the good advice! I will definitely do that. Today I have been studying the materials kindly provided by the respected @krivium all day long. I became a fan of John Dunlavy. This is a man of genius. And I even felt a little sad, I understand that in a few months I will not be able to achieve the knowledge that Mr. Dunlavy has, and as a result, even if I come up with a cool cabinet, my acoustics will not sound as good as Mr. Dunlavy's acoustics , I'm already silent about "sound better". 🙂
However, if I don't try to do it, then I won't know if I can or not. 🙂
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It will, but at reduced level.
If you start simulating with real driver parameters you will realze quickly that
95 dB AND 20 Hz is absolutely impossible to get (unless you build a 20 Hz horn).
But as i mentioned before you could drive the woofers actively and either use more power with less efficient drivers (that may actually go to 20 Hz) or equalize efficient drivers to allow them to play 20 Hz.
Or you use an insane amount of driversused in pairs in series/parallel combination( direct radiators)!
First as i talked about Atc design philosophy:
http://www.acousticfrontiers.com/speaker-off-axis-ka-and-driver-diameter/