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lucianbaban
(@lucianbaban)
Active Member Registered
Joined: 1 year ago
Posts: 8
14/11/2020 4:54 am  

Hello,

I've been trying very hard to understand how to build the best enclosure for any specific speakers. My last project was a small bluetooth DIY speaker using two Visaton FR10 and a TDA7492P Sanwoo board which didn't please me that much.
I currently have some old car speakers laying around and i'm trying to use them to build another stereo speaker system. The speakers are two Hertz EV 130.5 4 ohm, two tweeters Hertz ET 26.5 4 ohm and two cross over Hertz CH200. Essentially they came as a kit. I also have an Yamaha rx396 amplifier with 50w at 8 ohm that i will use.

I've used WinISD to calculate the volume for the enclosure but that's where pretty much where i got stuck. It gave me a 31.9 litter cabinet with a 4.7 cm vent diameter and a 3.19 vent length.

Now, the vision in my mind is that i want them to be tower like enclosures. I don't know how to determine the best design for this(widh, height, lenght), where to place the vent port (the middle, down or how far from the speaker).

If anyone can help me with specific details due to the fact that i am very new at this and trying to understand logical way how to do it. Or any links to youtube or this forum tutorials (i've tried search but i don't know key words what to look for) i would appreciate it very much.

@tvor-ceasar i've seen in a previous post your recommendation for best ratio. I don't understand how to calculate that ratio on "cube root" (cube root of what?)

Thank you in advance !

 

 

bluetooth 2
bluetooth 1
win isd 2
win isd 1

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TVOR-Ceasar
(@tvor-ceasar)
Honorable Member Moderator
Joined: 2 years ago
Posts: 523
14/11/2020 12:26 pm  

@lucianbaban

Looks like a nice build. can't wait to see and maybe hear what it sounds like. Maybe grab some Royalty Free tracks to put up on YT??

Thanks for the question. 
The internal volume is what you would need to use to figure out your basic interior dimensions.I'm going to paste my Qbasic code for the 2 types of boxes that were prevalent at the time (has it really been that long ago?? OMG I'm getting old! LOL), the Golden Ratio and the Acoustic Ratio.

*****
PRINT " THIS PROGRAM WILL DESIGN A BOX OF REQUIRED SIZE"

PRINT " FOR YOUR PARTICULAR NEEDS"

PRINT : PRINT

INPUT " WHAT IS THE BOX SIZE IN CU.FT."; A

PRINT

INPUT " WHAT IS THE THICKNESS OF THE BOX WALL"; B

PRINT

LET C = A ^ (1 / 3) * 12

'GOLDEN

LET D = C * .618

LET E = C * 1.618

LET F = C + (2 * B)

LET G = D + (2 * B)

LET H = E + (2 * B)

'ACOUSTIC

LET I = C * .7937

LET J = C * 1.2599

LET K = F

LET L = I + (2 * B)

LET M = J + (2 * B)

PRINT " THE FOLLOWING ARE TWO POSSIBILITIES FOR OPTIMUM"

PRINT

PRINT " BOX SIZES BOTH INSIDE AND OUTSIDE DIMENSIONS"

PRINT : PRINT

PRINT " GOLDEN RATIO"

PRINT

PRINT " INSIDE DIMENSIONS ="; E; "H,"; C; "W,"; D; "D."

PRINT " OUTSIDE DIMENSIONS="; H; "H,"; F; "W,"; G; "D."

PRINT : PRINT

PRINT " ACOUSTIC RATIO"

PRINT

PRINT " INSIDE DIMENSIONS ="; J; "H,"; C; "W,"; I; "D."

PRINT " OUTSIDE DIMENSIONS="; M; "H,"; K; "W,"; L; "D."

*****

As you can see, this is written with Imperial measurement  in mind, but you can use it directly (removing the "*12") with Metric, changing the finished inches (") to decimeter (dm). The only thing you'd have to do is convert the "Thickness of the box wall" to dm.

Let's look at this from the top.
The most important thing is the box volume, which is the interior volume. You need the Cube Root of this. Since Qbasic does not have Cube Root as a function, I use the equivalent function of "raise to a power", the carat key "^", and go to (1/3). This gives you your base interior width ("C") on which to calculate everything else, just by using the supplied multipliers. To get the outside dimensions, just add 2x's the "Thickness of the box wall".

What is nice about just about all of  today's computers and phones is that they have extended calculators built in. My Win7 calculator can display the Scientific version by using the pull down VIEW menu in the top left corner. It can also show the Unit Converter too, which is very powerful in itself, configuring types and initial units to choose from.

image

Same thing for my Phone's calculator, except mine requires it to rotate to landscape to see the extended options.
If you take note in the screenshot, there is a "Cube Root" button

image

and a "Raise To the Power of" button

image

 which can be used directly (CR) or with the extra work shown up above (RTP).

Now, as I said in a previous post, this is just a starting point. You are not 100% beholden to these numbers. If you mock up a box that is more pleasing to your design taste, as long as you can achieve the required interior volume (accounting for extras such as bracing, etc), then the sky is the limit. If you want to turn the box sideways for the front, go ahead. Lay it on it's side, go ahead. Use the top as the face, go ahead. The experimentation is what this hobby is all about. 

For reference, this is what I get when I convert 31.29L to Cu.Ft. (1.105) and a wall thickness of 3/4" (0.75"):

image

Grab your calculator and check it out in the conversion menu. It'll be very, very close (3rd or 4th place past the decimal, usually)

I hope this helps clarify how to get the basic numbers. 
Cheers!

-Charlie


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TVOR-Ceasar
(@tvor-ceasar)
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Joined: 2 years ago
Posts: 523
14/11/2020 12:59 pm  

BTW, when using Liters, if you want to change the initial Cube Root  calculation (C) to cm, replace the *12 with *10. Then you can use cm for the wall thickness.

-Charlie


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lucianbaban
(@lucianbaban)
Active Member Registered
Joined: 1 year ago
Posts: 8
14/11/2020 3:09 pm  

Thank you very much for the reply.

From what i understand from that, is that i can either go for golden or acoustic dimentions. Meaning that my w,d,h cuts will be the outside dimensions with a 1.9 cm thick birch or MDF. Right?

 

Oh and how do i install Qbasic software on windows 10. I downloaded but it won't start. 


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lucianbaban
(@lucianbaban)
Active Member Registered
Joined: 1 year ago
Posts: 8
14/11/2020 3:49 pm  

I thought about something and i wanted to ask..

1. Since this is a car woofer, isn't it designed to work in tighter spaces like cars doors? So maybe a closed enclosure will do better?

2. Do i make a baffle for the tweeter or just keep it outside?

3. A friend is telling me i shouldn't do 31.9L, but arround 12L. Is that correct ?


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TVOR-Ceasar
(@tvor-ceasar)
Honorable Member Moderator
Joined: 2 years ago
Posts: 523
14/11/2020 4:43 pm  

@lucianbaban

Yes, get your initial measurements and then add 2*1.9 cm to the H, W, D to get the outside dimensions.

I have to use DOSBox to run Qbasic, and I'm on Win7. Once you get it installed, there are a few tricks to make it more user friendly. Let me know when you have it installed and I'll help out.

-Charlie


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TVOR-Ceasar
(@tvor-ceasar)
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Joined: 2 years ago
Posts: 523
14/11/2020 5:07 pm  
Posted by: @lucianbaban

I thought about something and i wanted to ask..

1. Since this is a car woofer, isn't it designed to work in tighter spaces like cars doors? So maybe a closed enclosure will do better?

2. Do i make a baffle for the tweeter or just keep it outside?

3. A friend is telling me i shouldn't do 31.9L, but arround 12L. Is that correct ?

Give this article a read. You have an automotive style driver which, if it is to be installed in a factory location, is really more of an Open Baffle type of driver. Think about what they have to contend with - most places they would be mounted are not even close to being a sealed box, and they wouldn't be able to be used in a particular ported area without a recalculation for the existing "box" volume and port size. Looking at the Qts, 0.68, it is very close to Open baffle territory. And even with it being on the border between sealed and OB, the box you'd need for a sealed version would be prohibitive and most likely underwhelming.

Ask your friend to show you the calcs that support his claim. Not all drivers are the same, and he cannot base one design off another just based on the driver size alone, unless it is a Transmission line design. That is the only one I know of that bases most of the design on the driver size and Fs alone.

-Charlie


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lucianbaban
(@lucianbaban)
Active Member Registered
Joined: 1 year ago
Posts: 8
14/11/2020 5:34 pm  
Posted by: @tvor-ceasar
Posted by: @lucianbaban

I thought about something and i wanted to ask..

1. Since this is a car woofer, isn't it designed to work in tighter spaces like cars doors? So maybe a closed enclosure will do better?

2. Do i make a baffle for the tweeter or just keep it outside?

3. A friend is telling me i shouldn't do 31.9L, but arround 12L. Is that correct ?

Give this article a read. You have an automotive style driver which, if it is to be installed in a factory location, is really more of an Open Baffle type of driver. Think about what they have to contend with - most places they would be mounted are not even close to being a sealed box, and they wouldn't be able to be used in a particular ported area without a recalculation for the existing "box" volume and port size. Looking at the Qts, 0.68, it is very close to Open baffle territory. And even with it being on the border between sealed and OB, the box you'd need for a sealed version would be prohibitive and most likely underwhelming.

Ask your friend to show you the calcs that support his claim. Not all drivers are the same, and he cannot base one design off another just based on the driver size alone, unless it is a Transmission line design. That is the only one I know of that bases most of the design on the driver size and Fs alone.

Can the speaker values just be marketing?


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TVOR-Ceasar
(@tvor-ceasar)
Honorable Member Moderator
Joined: 2 years ago
Posts: 523
14/11/2020 9:13 pm  
Posted by: @lucianbaban

Can the speaker values just be marketing?

It very well could be. Since you used WINISD, I have to conclude that you input the driver parameters that are on the PDF to create a driver profile. Were there any discrepancies that showed up after you did that? IIRC, the problems would show up red, or change when you add another value. Did you have the FRD and ZMA files?

-Charlie


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TVOR-Ceasar
(@tvor-ceasar)
Honorable Member Moderator
Joined: 2 years ago
Posts: 523
15/11/2020 1:38 pm  

I actually want to thank you for this thread. It has given me an idea on something I can implement in the re-write of my "overall new program" listed in a previous thread. I haven't had a whole lot of time to work on it lately, but I need to write down this thought (since I'm not at home):

" When choosing either Imperial or Metric units (set flag), be sure to set the variable constructs via IF/THEN statements with the correct formulae. ie, like the change above^^."

Ok, I've got it now. 🤔 

-Charlie


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123Toid
(@123toid)
Illustrious Member Admin
Joined: 3 years ago
Posts: 1094
16/11/2020 12:49 pm  

@lucianbaban

This sounds like a great project. You are correct to assume this would be better suited for a sealed enclosure. And like Tvor had said, you can also try it open baffle. But off you really want more bass, if go ahead and try sealed first. 


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kanaaudio
(@kanaaudio)
Trusted Member Registered
Joined: 5 months ago
Posts: 71
17/11/2020 3:42 am  

@tvor-ceasar

I apologize for jumping in to your discussion. I am just trying to figure out what you mean by this, that the speaker values might just be marketing?

Posted by: @lucianbaban

Can the speaker values just be marketing?

It very well could be. Since you used WINISD, I have to conclude that you input the driver parameters that are on the PDF to create a driver profile. Were there any discrepancies that showed up after you did that? IIRC, the problems would show up red, or change when you add another value. Did you have the FRD and ZMA files?

I mean, when designing a box, vented or sealed, I should be able to use the spec values directly from the accompanying pdf's, found for example on partsexpress or soundimports? Or is there something more/else to be aware of?

 

Also, I following the link to the article you shared with the EBP Calculator - closest to 100 is best suited for ported enclosures, closest to 50 best for sealed. Using the values for the Dayton Audio ND91-8 I get an EBP of 133, which I guess points to ported?
However, reading directly below, using the Q of a driver approach, I have a QTS of 0.47 pointing to sealed enclosure? What causes this difference?

 

Thanks,

 

 

 


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kanaaudio
(@kanaaudio)
Trusted Member Registered
Joined: 5 months ago
Posts: 71
17/11/2020 3:51 am  

@tvor-ceasar

Sorry, I see I need to clarify my last question. I read at the button, that both are rules of thumb and that they might point in difference directions. My real question is, which should I trust, or would I always need a program like WinISD to make sure?

(my problem is, that I am not able to install WinISD, because I only have a company computer, which is very restricted. And my wife only has a Macbook which doesn't seem to support the program)


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TVOR-Ceasar
(@tvor-ceasar)
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Joined: 2 years ago
Posts: 523
17/11/2020 9:38 am  

@kanaaudio

Let me try to get to both posts here.

Re: actual published numbers - Many of the numbers you see listed for a specific driver may or may not be 100% correct. As you can see with the EBP, it is a calculated number from 2 other parameters. I have seen Nick's explanation of Thiele Small (T/S) parameters, but some of the most thorough explanation and graphic demonstration to date has been done by Hexibase. Scroll down to his T/S Parameters explained videos. I've done screenshots from here that I use for reference, because some things he explained were very hard to find. (Sorry Nick, I just think Hexibase digs deep and really puts it together well)

Now, if you watch those videos, you can see how so many of these parameters are actually calculated rather than measured, and are open to "Fudging" the numbers, or just throwing something in there to fill it out. That's why programs such as WinISD and BassBox have parameter checking built in. That's also why the absolute best way to design stuff is to measure it yourself. That removes any questions you may have. As to the EBP vs Qts, you'll remember from Nick's discussion that the 2 numbers do not always agree for box type. When that happens, you'll have to follow the advice in the discussion, or just experiment. 

For the Apple and Win-WORK computer scenario, if either have the ability to run Excel, then you can use Jeff Bagby's spreadsheets to do your calcs. You can find links here and here.

Or you could be where I was many years ago with no computer and just notebooks, pencil, and calculator. I got really fast back in the day running scenarios based Qts, Vas, and Fs. Only a few minutes needed. Now if you set up a paper spreadsheet with all the pertinent formulae and spaces for the info, you could run them rather quickly by hand and verify any manufacturer's number sheets within 5-10 minutes.

-Charlie


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123Toid
(@123toid)
Illustrious Member Admin
Joined: 3 years ago
Posts: 1094
17/11/2020 11:44 pm  

@tvor-ceasar

I agree.  Nothing ever to be sorry about. We can and should all learn from each other.  

@kanaaudio

The way I like to look at it is in the same way I do the wattage of an amplifier.  Some companies are just dishonest with their published specs.  Some are honest, but their quality control,  isn't the best.  While others are honest and their quality control is good.  You need to have both in ordder for the T/S specs to be worth it's salt.  That is why you see many of us stick to good name brands, such as Dayton, Eminence, Peerless, etc. 


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