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Audio/Video Gear and Systems => The Lab => Topic started by: Florent on 10 Feb 2020, 03:16 pm

Title: First DIY 2 way stereo speakers. What am i doing ?
Post by: Florent on 10 Feb 2020, 03:16 pm
Hello everybody,

I'm from Belgium. Always been a fan of various kinds of music, jazz is on the top shelf, but never really had good speakers. So recently, i started looking every videos i could find and forums to try to understand all of what make a good speaker.

I started designing a pair of 2 way speakers. This is a budget build but i start from SCRATCH, i don't even own an amp ! So i have to buy everything...

The first project that ended up in the dumpster was a 8ohm speaker. Then i realized an amp for 8 ohm speaker is way more expensive than those 4ohm ones. So i picked some amp module from wondom, and looked for speakers, started designing the crossover, the enclosure and here i am full of doubts !

Here below you can see all the info about the speakers i am trying to make. And one thing that bothers me is that i have no idea what the phase graph should look like.
Besides that, i can imagine some of you will comment "that is never going to work" and start pointing problems at my design. And THAT IS WHY I AM HERE, shoot ! Fire at will !

My point is to make a 2way bookshelf stereo pair that sounds decent for 350 ~ 400 euros. AMP INCLUDED.
I am very excited to press that purchase button with all the stuff i think i need to build this but i thought i needed some opinions from people with knowledge of all this.

So here is my parts list and the crossover design and some graphs.

Drivers :
Dayton audio ND25FW-4
Dayton audio RS180P-4

Amp :
Wondom T-amp Class D 2x400W 3Ohms 48V

Power supply :
Mean Well 48V 7.5A 350W

Enclosure :
24 liters
30,8*2*21cm (LxHxW) vent

I inverted polarity on the woofer. It gave better results on the frequency response graph but is it OK to do that ?

(http://HTTP://www.audiocircle.com/image.php?id=204466)
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: Florent on 11 Feb 2020, 06:21 am

(https://www.audiocircle.com/image.php?id=204507)
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: S Clark on 11 Feb 2020, 04:00 pm
How did you measure your response?  As it is, it looks pretty good.  You might try a 4 ohm instead of the 5.6 if you'd like to lift that treble response a bit. 
But that is that an impedance graph in the lower left?  If so, you'll melt down amps with it. 
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: Florent on 11 Feb 2020, 04:28 pm
How did you measure your response?  As it is, it looks pretty good.  You might try a 4 ohm instead of the 5.6 if you'd like to lift that treble response a bit. 
But that is that an impedance graph in the lower left?  If so, you'll melt down amps with it.

Thanks for your answer !

For the response, i downloaded the FRD and ZMA files from parts-express and loaded them into VituixCad2. Then noodled around with the crossover until this result !
And yes, it is an impedance graph in the lower left. What do you mean i will melt amps with it ? What i read about it is that it is the lowest figure that can be a problem, which is 3.3ohm. So i was thinking on buying the Wondom 2x400W 3Ohm amp, wich is super cheap btw. Would this be OK ?
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: wushuliu on 11 Feb 2020, 05:17 pm
Thanks for your answer !

For the response, i downloaded the FRD and ZMA files from parts-express and loaded them into VituixCad2. Then noodled around with the crossover until this result !
And yes, it is an impedance graph in the lower left. What do you mean i will melt amps with it ? What i read about it is that it is the lowest figure that can be a problem, which is 3.3ohm. So i was thinking on buying the Wondom 2x400W 3Ohm amp, wich is super cheap btw. Would this be OK ?

He's looking at your rear port graph, not impedance. Your impedance looks fine. However, I think you are going to need to increase the woofer inductor. .56mh seems very low and your crossover shows a peak at 1.4k for the RS180. You will want to flatten that out, probably by increasing the inductor value. Typical 4ohm woofer would be more like 1-1.5mh.

No. You should not need to invert woofer polarity.
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: Florent on 11 Feb 2020, 05:31 pm
He's looking at your rear port graph, not impedance. Your impedance looks fine. However, I think you are going to need to increase the woofer inductor. .56mh seems very low and your crossover shows a peak at 1.4k for the RS180. You will want to flatten that out, probably by increasing the inductor value. Typical 4ohm woofer would be more like 1-1.5mh.

No. You should not need to invert woofer polarity.

(https://www.audiocircle.com/image.php?id=204523)

Polarity reset to normal. This is as close as i can get to flat with this crossover. But isn't it the gray line that represent the average frequency response between woofer and tweeter ? That red bump in the initial graph is going to be heard ? Because at 1400Hz with polarity inverted, that gray line is lower than the red one.
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: wushuliu on 11 Feb 2020, 05:59 pm
(https://www.audiocircle.com/image.php?id=204523)

Polarity reset to normal. This is as close as i can get to flat with this crossover. But isn't it the gray line that represent the average frequency response between woofer and tweeter ? That red bump in the initial graph is going to be heard ? Because at 1400Hz with polarity inverted, that gray line is lower than the red one.

Yes, the red line (woofer) and blue line (tweeter) will be heard. The gray line just shows the mix of the two.

Normal polarity is what you want for your 2-way (especially for your first time). The reverse polarity will not sound right.

Now look at the graph: see that woofer peak? You should be able to flatten that by increasing inductor value and changing capacitor value. If not, you may need to add a 'notch' filter to flatten it.

Also you are crossing that tweeter too high for this woofer. You need to crossover lower if possible - 2.5-3k.
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: wushuliu on 11 Feb 2020, 06:09 pm
Okay, I bet your are doing this based on Kirby Does Audio tutorial on YouTube.

*sigh*

It's a bad tutorial. I am guessing you did not account for baffle step loss, nor did you account for real impedance inside a box. Correct?
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: Florent on 11 Feb 2020, 07:14 pm
Okay, I bet your are doing this based on Kirby Does Audio tutorial on YouTube.

*sigh*

It's a bad tutorial. I am guessing you did not account for baffle step loss, nor did you account for real impedance inside a box. Correct?

Correct ! I have no idea what you are talking about, I am all ears...
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: wushuliu on 11 Feb 2020, 08:00 pm
Correct ! I have no idea what you are talking about, I am all ears...

1. Know what the enclosure dimensions are: LxWxH

2. Use a program like Jeff bagby's Box Response Modeler to model frequency response based
on your enclosure dimensions.

3. Export the adjusted frequency response and zma/impedance files.

4. Import back into Vituicad or whatever software.

OR

Use Vituixcad Diffraction Calculator. It looks like it can do the same thing and would be easier since it's the same software, but I have never used it so I don't know for sure.

Paul Carmody has some instructions that may be helpful. Start at Step 5:
https://sites.google.com/site/undefinition/simulated-measurements

Speaker design is *not* simple. The Kirby Meets Audio video is misleading. Without modeling response based on actual box dimensions and baffle step your results will be terrible and not match real world response. That said, the Vituixcad software does look a nice tool for speaker design.

What you need as a first-timer is to have an actual microphone for measuring. Otherwise how will you know if what you design is even accurate? You will have no idea. Designing without measurements is usually suggested AFTER you know the basics.

I strongly suggest you just pay the ~$90 for a calibrated measurement microphone and start there. It will make your life much easier.

http://www.cross-spectrum.com/measurement/calibrated_dayton.html
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: Florent on 11 Feb 2020, 08:08 pm
1. Know what the enclosure dimensions are: LxWxH

...
:thumb:

I will come back when my head is a little less empty ! =P

I have to say that i didn't think for a second that it would be easy, i am far from quitting this !! Thank you for your help. I very much appreciate it.
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: S Clark on 11 Feb 2020, 09:29 pm
He's looking at your rear port graph, not impedance.
No, it was just that the graph was so small it looked like the impedance was just above zero.  3.3 is low, but some amps will handle it (and some won't).
Yep, it's clear that no baffle step correction is in the crossover.  Also, there may be phase issues that won't show up in that model... and they can cause wild deviations in output. 
Like Wushiliu mentioned, real time measurements are crucial to real success.  For most, the easiest (and best) answer is to build a kit. 
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: S Clark on 11 Feb 2020, 10:14 pm
I can't find either woofer nor tweeter at the Parts Express web site.  Are these discontinued drivers?
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: Florent on 11 Feb 2020, 10:32 pm
https://www.parts-express.com/dayton-audio-nd25fw-4-1-soft-dome-neodymium-tweeter-with-waveguide-4-ohm--275-051
https://www.parts-express.com/dayton-audio-rs180p-4-7-reference-paper-woofer-4-ohm--295-375

I spelled it wrong earlyer, sorry
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: hdspeakerman on 11 Feb 2020, 11:22 pm
Go to Parts Express Tech Talk forum for help.  Good group and lots of newbies.
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: wushuliu on 12 Feb 2020, 12:05 am
Go to Parts Express Tech Talk forum for help.  Good group and lots of newbies.

Agreed, he should go to Parts Express Techtalk. Especially since he is using their woofer and tweeter.
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: Folsom on 12 Feb 2020, 12:22 am
Wush is doing a pretty good job.

But the whole point of measuring in box and going from there can't be understated. I'd save money for replacing crossover parts to fine tune anything you make. And I'd want to build/buy a box that I could replace the front plate on incase I couldn't get the woofer/tweeter to match up. It would be wise to ask someone if a tweeter and woofer would be very compatible. DIYaudio & TechTalk are the go to places in the US but there's other euroforums, too. (does Visaton have one?)

Welcome to the craziness, the difficulty, the fun, of true DIY.

P.S. I like Kirby but the way he's doing it he'll have to measure real world performance and redo the crossover again a few times perhaps. It's unlikely he'll get any true performance of a studio monitor any time within the next two videos but he'll probably be happy with them. I just enjoy that people are building anything at all from watching him.
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: Florent on 12 Feb 2020, 05:50 am
I think i will dig a little more into all this and order the parts + microphone. Making different sized enclosure and baffle is no problem for me since i am a cabinet maker and i have my own workshop !
From the measurements i will get, i Will order some more parts for the crossover.

Thanks for the help !
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: wushuliu on 12 Feb 2020, 05:55 am
I think i will dig a little more into all this and order the parts + microphone. Making different sized enclosure and baffle is no problem for me since i am a cabinet maker and i have my own workshop !
From the measurements i will get, i Will order some more parts for the crossover.

Thanks for the help !

Great! Making the cabinets is half the battle. Keep us posted on your developments.
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: Florent on 12 Feb 2020, 07:24 am
Great! Making the cabinets is half the battle. Keep us posted on your developments.

So i read everywhere that your amp should be way more powerfull than what you need to have minimum THD so i chose 2x400W for that 2x80W build. If i am correct, at 3Ohm, 15,5V i should have 5,15A and 80W (woofer+tweeter)
Can i just add a 10A fuse (Left + Right) between amp and power supply ? I guess the amp itself will draw some power and won't transmit 100% of what the power supply gives but, let assume it does for now. Would it add noise ? It would be supper handy, if i blow up the fuse, there you are, i know how far i can push the knob on the amp before destroying my drivers...

Inner impedance has to do with excursion right ? On vituixcad i see that at 60W (the woofer), the excursion graph looks good, stays under the 6mm Xmax

About the baffe step loss, i read here and there that rounding the edges is a good idea, will it make any difference ?  What are other things that can be done here to reduce Baffle step loss ?

EDIT : For those like me who don't really understand all this, here is an interesting video about baffel step. https://www.youtube.com/watch?v=sttbT1ONP80
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: richidoo on 12 Feb 2020, 03:13 pm
Florent, welcome to AudioCircle! Thanks for sharing your project with us.

I generally recommend people build a kit for their first DIY speaker for the main reason that they can have guaranteed success on the first try. It is difficult to avoid failure on the first try of any sport. But since you are so committed, hopefully you will persevere through the many challenges and find success. Speaker design is pretty difficult. I have built about 25 speakers in the last decade, and I am only now confident enough to do my own design from scratch and it is still based loosely on someone elses successful design that I know works.

Your drivers are good choice and your sim looks fine. Make sure your drivers are time aligned on Z axis when you are using symmetrical order crossover. You will like the flatter phase response. This may require a tilted baffle, but you can handle that.

Sorry I joined late so I won't jump on the fine advice you already got. But I'll pick up on your latest post.

Digital amps usually have flat or decreasing distortion up to max power. So the sound quality doesn't change much, and old rules about the first watt don't really apply to modern class D amps. Your amps are quadruple what you really need for residential listening, but there's no harm in having extra power. It will allow further DIY speaker experimenting in the future.

The best way to protecting your speakers from damage is using your ears. It will sound frightfully awful when they are in danger of damage. But you have to be paying attention and also willing to turn it down. If less responsible people will use the stereo besides you then automatic protection is prudent, but it's just you then it is not needed. 100dB is very very loud and that falls within the driver power rating. Jazz and other brain music is not usually played loud enough to damage. Even short peaks above the power rating are OK. It's the sustained compressed signal over power rating that gradually overheats or melts the voice coil, or less likely, the full scale transient pop at high gain that can damage the suspension. A little care and thought will prevent accidents.  ymmv   Yes you can put a fuse anywhere you want. Usually fuse is put before power supply. It adds resistance so between the PS and amp not ideal.

There is nothing you can do to prevent baffle step loss, except mount the drivers flat into the wall of your room, or make them a bipole speaker with identical woofers on the front AND back sides of the box. Aside from those options, the sound will diffract on the front baffle edges and the diffraction will attenuate the LF on-axis SPL. So you have to equalize the response to compensate. In a passive crossover speaker the compensation is made by attenuating the frequencies above the baffle step freq. In an active speaker you can boost the freqs below the baffle step. It looks like 6dB first order, but it is actually shallower than 1st order. You probably only need 3-4dB of compensation (instead of the full 6dB) since the diffracted LF energy is still in the room and is reflected back to your ears. 3-4 usually sounds best, depending on the size of the room.

Rounding the edges can smooth out the FR bumps caused by diffraction, but the smoothing effect of rounding is proportional to the radius of the roundover, and the wavelength being smoothed. The smoothing effect begins with radius 1/10 of the wavelength, but if you want a perfectly smooth baffle step you need a large enough spherical enclosure which is highly impractical! https://trueaudio.com/st_diff1.htm  A roundover of 1/2" radius will mostly affect the high treble. If you want audibly smoother upper midrange you need 2-3" radius. As an aside: Spherical speakers are hard to build, but if you ever hear one you'll remember the smooth response they have. The larger sphere the better!  Once at RMAF 2008 a guy brought a 3 foot diameter sphere speaker from Japan. It had a tiny 3" full range driver but it sounded really smooth and natural.

Be sure to post some pictures, especially of your wood shop!!
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: Florent on 12 Feb 2020, 08:24 pm
Hi richidoo !

I guess i didn't take a kit because i wanted to do it myself. Didn't see the point on buying this stuff if i can make it with scrap parts from my shop !
Now, a few weeks and dozens of hours re searshing on the subject later, I think kits are the way to go for noobs like me ! :P But still, i want to make it myself. Now that i am this far, let's go the extra mile right ? I guess there is a 50/50 chance it won't turn out good...

I bought the parts that i think i will need for the first step, drivers, simple crossover, and the amp with power supply. I will look up for a microphone tomorrow to make measurements as soon as i get one.

First step will be assembling everything and test it ! Looking forward for the soldering  :P

Second step will try to improve that... And if it reaaaally doesn't work, well, i still can buy a DSP right ?

Pictures of the wood shop is out of the question right now it is a complete MESS !!!  :roll: 

Got the parts today. Here is where i am at ! Finishing the aesthetics (and gluing the enclosure) will be for when the sound is right ! And my brother will 3D print me a case for the amp and power supply...
(https://www.audiocircle.com/image.php?id=204555)

(https://www.audiocircle.com/image.php?id=204556)
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: wushuliu on 12 Feb 2020, 11:39 pm
I bought the parts that i think i will need for the first step, drivers, simple crossover, and the amp with power supply. I will look up for a microphone tomorrow to make measurements as soon as i get one.

First step will be assembling everything and test it ! Looking forward for the soldering  :P

Second step will try to improve that... And if it reaaaally doesn't work, well, i still can buy a DSP right ?

Pictures of the wood shop is out of the question right now it is a complete MESS !!!  :roll: 

Got the parts today. Here is where i am at ! Finishing the aesthetics (and gluing the enclosure) will be for when the sound is right ! And my brother will 3D print me a case for the amp and power supply...


Too bad you bought crossover parts before understanding how to design one but I guess that will be a learning lesson for you. I can almost guarantee you will need larger .9-1.25mh inductors for the woofer. However, you do not need to do any soldering until you have it right. Just use alligator clips instead to connect the leads:

(https://www.audiocircle.com/image.php?id=204560)
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: S Clark on 13 Feb 2020, 12:59 am
Yep, you build your crossover with alligator jumper wires.  Get a pack from Amazon, because you'll need several. 
Take some time to get used to taking measurements- there's a learning curve.  Danny Richie of GR-Research
may have a video on his approach to measurements.  If so, watch it and learn. 
Like Rich, I've built or supervised lots of speakers--- 50+ pairs.  It's begins to follow a pattern after a while.  You may find some designs using the same woofer.  If so, you might be able to use their crossover as a starting point. 
Good luck.   
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: Folsom on 13 Feb 2020, 01:33 am
I have bundles of alligator clips dangling off of my audio rack and other places.  :lol:
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: richidoo on 13 Feb 2020, 02:08 am
(https://www.audiocircle.com/image.php?id=204555)

Wow, those look awesome!!   boiz got skilllllz....  8)

The first try of a simulated crossover rarely works perfectly, especially if the simulation is not based on measurements of your actual speakers. After you measure your new sim will show what tweaks are necessary.

The waveguide time aligns the tweeter with the woofer so you're all set on that.
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: Florent on 13 Feb 2020, 09:40 am
Revised the crossover, SPL looks better, only -2.5db in that 2.3kh dip. But Phase doesn't look gooed ! How can i fix that ?
(https://www.audiocircle.com/image.php?id=204579)
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: JLM on 13 Feb 2020, 02:08 pm
DSP should only be used as "icing on the cake" or a bandaid, not a fix all solution. 

Good speakers start with good parts (drivers, crossover, cabinet).  There's no getting around a flawed design with DSP. 

Note that Buchardt is using DSP to tune out system minor resonances and diffractions of their new A500 monitor after taking 2700 measurements of each driver, but only after starting with properly paired drivers/cabinet/amps (in the lab, not by guess or by ear). 
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: Florent on 14 Feb 2020, 06:29 am
Ok, so yesterday i soldered the power input to the amp module, made a cable with wall plug for the power supply, wired everything, took dozens of measurements with my multimeter and finaly hooked up two litle speakers i had in the atick. It works perfect.
Ordered a microhpone, the DAYTON AUDIO UMM-6 USB. I will have it on monday i guess, it comes from a french website.
(https://www.audiocircle.com/image.php?id=204603)
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: wushuliu on 14 Feb 2020, 07:14 am
Revised the crossover, SPL looks better, only -2.5db in that 2.3kh dip. But Phase doesn't look gooed ! How can i fix that ?

Revised the crossover based on what? Have you done any of the steps recommended earlier? Until you do those first, what you're simulating isn't going to be much help. Also, those images are too small to see in detail.
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: wushuliu on 14 Feb 2020, 07:41 am
Below is a first timer thread using the same tweeter but a different 4ohm woofer. It's a good thread. Yes some will be over your head but you'll get an idea of what's involved to do it right and just how much Kirby left out. Notice his tweeter crossover (remember I said you'd want to cross more like 2.5-3k?):

http://techtalk.parts-express.com/forum/tech-talk-forum/1343815-the-super-bees-garage-two-way-build/page7

In my opinion, this tweeter is not a good choice for a first timer. Even Parts Express' kit that uses the tweeter has a lot of parts - and it's in their best interest to use the fewest parts possible.

So another lesson - A lot of cheap woofers and tweeters require more crossover work than the expensive ones. That's why they're cheap.

EDIT: Actually I take that back some, since really it's just a 3rd order electrical/4th order acoustic with an L-pad but still...
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: Florent on 14 Feb 2020, 10:03 am
Below is a first timer thread using the same tweeter but a different 4ohm woofer. It's a good thread. Yes some will be over your head but you'll get an idea of what's involved to do it right and just how much Kirby left out. Notice his tweeter crossover (remember I said you'd want to cross more like 2.5-3k?):

http://techtalk.parts-express.com/forum/tech-talk-forum/1343815-the-super-bees-garage-two-way-build/page7

In my opinion, this tweeter is not a good choice for a first timer. Even Parts Express' kit that uses the tweeter has a lot of parts - and it's in their best interest to use the fewest parts possible.

So another lesson - A lot of cheap woofers and tweeters require more crossover work than the expensive ones. That's why they're cheap.

EDIT: Actually I take that back some, since really it's just a 3rd order electrical/4th order acoustic with an L-pad but still...

Thank you for your help, I do realise, more and more actualy, how much there is to learn, and i am exited about it !
I just fooled around with the measurements i got from parts express but you are right, there is no point going on with those measurements.
I have to make my own ones. I am currently waiting the delivery of my mic. I guess the next step for me is to wait until i have it, make FRD files and then start again on Vituixcad. Then only i will be able to know what parts to buy for the crossover. As you said, my first try will be to crossover at 2.5-3k.

You are right about the tweeter too, i should have picked another one... We shall call it a rooky mistake, and a good lesson.

As I said, the mic should arrive monday. Until then I guess that I'll just have to wait ! In the meantime, I'll keep educating myself !

About the phase, delay and Z axis, this is still a bit confusing for me. Pushing the tweeter backwards on Z axis changes it's delay ? Changing the delay makes drivers out/in phase ?
To illustrate my question..

In this picture, the drivers are out of phase, correct ? Z axis 0mm for both drivers.

(https://www.audiocircle.com/image.php?id=204605)

If i push the tweeter on Z axis by 34mm, the delay is -100 and the graph looks like this. Are the drivers "in phase" ? What about that peak from the woofer ? Since that peak is above the low pass, do i have to worry about it ? Or am i completely missing the point ?

(https://www.audiocircle.com/image.php?id=204606)
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: Florent on 14 Feb 2020, 11:57 am
Or should it look like this ?


(https://www.audiocircle.com/image.php?id=204607)
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: wushuliu on 14 Feb 2020, 04:39 pm
Or should it look like this ?
(https://www.audiocircle.com/image.php?id=204607)

Yes, more like this. It sounds like you are talking about the z offset (acoustic center) values. You will just have to do an educated guess, but yes that is what in phase looks like. With an RS180, the offset is usually ~.025m, but since you have the waveguide tweeter which is also recessed that means it will be a bit less, maybe .020m? Anyway, don't worry about that so much for now.
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: wushuliu on 14 Feb 2020, 04:46 pm
Here is a useful step by step guide you can look at until the mic arrives. References different software but you get a grasp of all the steps involved. Maybe study what you can replicate in Vituicad:

http://audio.claub.net/software/DaveDalFarra/Simple%20Loudspeaker%20Design%20ver2.pdf

Here is a guide on doing measurements by the great Jeff Bagby:

http://audio.claub.net/software/FRD_Blender/White%20Paper%20-%20Accurate%20In-Room%20Frequency%20Response%20to%2010Hz.pdf

He uses different software so you can use his or study how to do the same with Vituicad. But same principles apply.
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: Florent on 14 Feb 2020, 09:48 pm
Here is a useful step by step guide you can look at until the mic arrives. References different software but you get a grasp of all the steps involved. Maybe study what you can replicate in Vituicad:

http://audio.claub.net/software/DaveDalFarra/Simple%20Loudspeaker%20Design%20ver2.pdf

Here is a guide on doing measurements by the great Jeff Bagby:

http://audio.claub.net/software/FRD_Blender/White%20Paper%20-%20Accurate%20In-Room%20Frequency%20Response%20to%2010Hz.pdf

He uses different software so you can use his or study how to do the same with Vituicad. But same principles apply.

This is fantastic ! It will take some time to digest tho !

Edit : Started back from scratch based on those pdf's. Using unibox, i am pleased to see that my original enclosure and port design are ok !
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: Florent on 21 Feb 2020, 07:16 am
Hi !

Not much time lately, hard working.. Managed to take some measurements. Does this looks like ok ? Took those outside but not sure if my method was the best. The Jeff Bagby's way seems a little complicated to me. I Think outside is more simple/accurate, when the weather allows it...
I was surprised by the difference of dB of the two drivers, but i didn't change any parameter when measuring one or the other...

(https://www.audiocircle.com/image.php?id=204977)
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: wushuliu on 21 Feb 2020, 07:57 am
Hi !

Not much time lately, hard working.. Managed to take some measurements. Does this looks like ok ? Took those outside but not sure if my method was the best. The Jeff Bagby's way seems a little complicated to me. I Think outside is more simple/accurate, when the weather allows it...
I was surprised by the difference of dB of the two drivers, but i didn't change any parameter when measuring one or the other...

(https://www.audiocircle.com/image.php?id=204977)

I have no idea what you did. You need to explain things in detail. Where was the mic positioned? How far away was it from the drivers? Why did you measure both at once? I'm very confused.

Honestly, just sign up at the Parts Express TechTalk speaker forum. There are a whole bunch of people who will walk you through what you need to do. It's the best place for beginners in learning diy speaker building, period.

http://techtalk.parts-express.com/
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: Florent on 21 Feb 2020, 08:20 am
OK ! Thank you for your time anyway.
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: Florent on 21 Feb 2020, 08:40 am
To answer your questions, the speaker was on a table outside, with no walls within 6 meters, the mic at the same level as the speaker, at 1m away from the speaker.
I did not measure them both at once. I hooked up the woofer only, with no filter at all, used REW and umm6 mic to measure. Then, did the same with the tweeter only. Didn't change volume on computer or volume on amp. Saved those two frequency responses as txt files, imported them in vituixcad and that is what you are looking at.
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: wushuliu on 21 Feb 2020, 09:11 am
To answer your questions, the speaker was on a table outside, with no walls within 6 meters, the mic at the same level as the speaker, at 1m away from the speaker.
I did not measure them both at once. I hooked up the woofer only, with no filter at all, used REW and umm6 mic to measure. Then, did the same with the tweeter only. Didn't change volume on computer or volume on amp. Saved those two frequency responses as txt files, imported them in vituixcad and that is what you are looking at.

Your images are still too small to see the db scale so I'm guessing what it's showing is the almost 10db difference between the woofer and tweeter. If you look at the original specs for both of them on PE website you'll see the tweeter goes as high as 96-97db, the woofer only 87 or so through most of its response.

When you measured did you keep the mic at the same spot for both woofer and tweeter? You want to make sure to do that. Don't move the mic height from one to the other. Usually for 2ways people keep the mic at a point between the tweeter and the woofer.

It's also easier to analyze if you just show one image of the woofer response and then one of the tweeter. It's really hard to see details in this images.

Hopefully you measured with the speaker at the very edge of the table. Otherwise it sounds like you did okay. It's a start!
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: wushuliu on 21 Feb 2020, 09:34 am
Also you can do these measurements inside, as long as you have a general idea where they are going to be. Although it's more standard to do them outside with wide space and height, this isn't realistic for most people and is really just best practice if you want your design to be built by other people.

For a beginner who knows where the speakers are going to be I think it's just easier to do them inside as long as you keep the measurements at 1m or less. Even Kirby admits that even though, again, he only gives you part of the process (he doesn't tell you how to position the mic at all which is *important* as I mentioned above). He is doing his outside because he has to for the kits he sells.

Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: JLM on 22 Feb 2020, 01:51 pm
Not uncommon for "matching" drivers to not match (measure the same), even high-end drivers.  Don't know how many manufacturers measure each driver they install (or to allow for 20 hours or so of break-in first before measuring). 
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: wushuliu on 22 Feb 2020, 08:21 pm
Not uncommon for "matching" drivers to not match (measure the same), even high-end drivers.  Don't know how many manufacturers measure each driver they install (or to allow for 20 hours or so of break-in first before measuring).

True, but in this case it's not the matching between two of the same drivers he's referring to, it's the disparity between the woofer spl and tweeter spl. They are about 8db apart. Which is fine, just means padding the tweeter down with some resistors. It looks particularly bad though in his measurement because of the baffle step drop which causes a massive peak where the sound waves start to wrap around the baffle around the 1.5k mark before plummeting. This is why I was pushing for using the baffle diffraction simulation tools in his software. Then he would have seen it coming.
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: S Clark on 22 Feb 2020, 08:28 pm
And it's worth noting that baffle step compensation usually means lowering woofer output another 3 db or so across most of it's range.  These puppies are going to need a lot of watts to get some volume. 
This is another example of why I always try to steer first time DIY'ers toward a kit.  Building speakers on your own requires a rudimentary knowledge and a pretty decent measuring system... and even then it doesn't always work well. 
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: Tyson on 22 Feb 2020, 08:48 pm
Re: baffle step, I always wonder why 2.5 way speakers aren't more popular - it's a nice elegant solution to the baffle step loss and doesn't cost you anything in efficiency from the midwoofer.
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: wushuliu on 22 Feb 2020, 09:27 pm
Re: baffle step, I always wonder why 2.5 way speakers aren't more popular - it's a nice elegant solution to the baffle step loss and doesn't cost you anything in efficiency from the midwoofer.

Agreed. But there are the trade-offs IIRC:
lower impedance (8ohm-ish builds are still more popular then 4ohm).
Parts cost increase: the .5way woofer usually needs a hefty inductor
Frequency response: possible lobing issues since one woofer is closer to the floor (more theoretical than audible probably)

Usually what happens is someone asks this question, we go yeah why not, then someone convinces that you might as well just build a 3 way. Sometimes the most convenient option is less appealing I guess.

Lastly, I think the 2.5way concept is relatively 'new'. I believe Jeff Bagby said he is the originator only some 20yrs ago.
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: mick wolfe on 23 Feb 2020, 04:05 pm
I could be wrong, but I believe my JSE Infinite Slope Model 1's were defined as 2.5 ways. This is pushing roughly 40 years ago. Great speaker that I thought bested the rave of that time period, the Vandersteen 2c.
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: Florent on 25 Feb 2020, 09:06 am
I'm working hard on this ! Just bought some more crossover parts so i can try multiple arrangements and measure them, just found a store nearby that sells all i need and this is cheap stuff.
By wiring them in parallel or series i have plenty of room to experiment and it gives me the opportunity to learn a little more about how those values actually impact the frequency response. (and it's fun)
But I'm worried about metling the amp, so i go sometimes back to the computer and enter the values I'm about to try, so I'm sure about the minimum impedance.

I think i am getting closer to an acceptable result. But I was wondering, in REW, just how much smoothing is OK ?

Is a flat frequency response the best target or "house curve" should be preferred for a more "easy listening experience" ? Not that i actually am going to achieve one or the other with success but for knowledge, which would you choose ?


I will try to come back this week end with plenty of details. Pictures and measurements.

In the meantime, here is a picture of the last measurement i made. In my workshop, mic at 1 meter, speaker at the edge of the table, psychoacoustic smoothing, and the difference in db from the highest peak to the lowest dip is approx 10dB. So yes, improvements are yet to be made and that is also why I am asking about smoothing because unless it is Var or Psycho smoothing, it looks like a wild roller coaster.

Critics are welcome !

Sorry for the poor quality of the picture.

(http://www.audiocircle.com/image.php?id=205176)
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: Florent on 25 Feb 2020, 12:54 pm
Here you can see the inside of the enclosure and the port.

(https://www.audiocircle.com/image.php?id=205177)
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: wushuliu on 25 Feb 2020, 04:20 pm
I think i am getting closer to an acceptable result. But I was wondering, in REW, just how much smoothing is OK ?

Is a flat frequency response the best target or "house curve" should be preferred for a more "easy listening experience" ? Not that i actually am going to achieve one or the other with success but for knowledge, which would you choose ?

I will try to come back this week end with plenty of details. Pictures and measurements.

In the meantime, here is a picture of the last measurement i made. In my workshop, mic at 1 meter, speaker at the edge of the table, psychoacoustic smoothing, and the difference in db from the highest peak to the lowest dip is approx 10dB. So yes, improvements are yet to be made and that is also why I am asking about smoothing because unless it is Var or Psycho smoothing, it looks like a wild roller coaster.

What does it look like with 1/24 or 1/12 Octave smoothing?
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: Florent on 25 Feb 2020, 05:00 pm
What does it look like with 1/24 or 1/12 Octave smoothing?

Each horizontal line is 5dB.

I think I mislabled this measurement. It seems to be the previous version of the crossover shown earlier, there is a differnce...

1/12
(https://www.audiocircle.com/image.php?id=205207)
1/24
(https://www.audiocircle.com/image.php?id=205208)
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: wushuliu on 25 Feb 2020, 05:19 pm
Each horizontal line is 5dB.


What you are seeing is based on the speaker and mic placement. Below 800hz you are getting reflections from somewhere - the floor or a wall that's too close. That's why you have the dips at precise intervals from the woofer. The 1/24 is the more accurate and you can see the dips are really narrow, so not that bad. So you can either move the mic 6in-12in closer, raise the speaker off the table even higher, or move it away from any walls closer than 3ft/1m. You'll see the response change.

What's more important right now is the overall response, which looks really good! You seemed to have handled the tweeter well. Now you can start playing with tweeter level values depending on your taste. Some people like very flat, some people like a slight tilt down like yours. Up to you.

Can you show the current crossover?


Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: Florent on 25 Feb 2020, 05:44 pm
What you are seeing is based on the speaker and mic placement. Below 800hz you are getting reflections from somewhere - the floor or a wall that's too close. That's why you have the dips at precise intervals from the woofer. The 1/24 is the more accurate and you can see the dips are really narrow, so not that bad. So you can either move the mic 6in-12in closer, raise the speaker off the table even higher, or move it away from any walls closer than 3ft/1m. You'll see the response change.

What's more important right now is the overall response, which looks really good! You seemed to have handled the tweeter well. Now you can start playing with tweeter level values depending on your taste. Some people like very flat, some people like a slight tilt down like yours. Up to you.

Can you show the current crossover?


(https://www.audiocircle.com/image.php?id=205220)
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: wushuliu on 25 Feb 2020, 06:37 pm

(https://www.audiocircle.com/image.php?id=205220)

Okay, that seems more in line with a proper 2-way crossover, good work!

1. Looks like you have the tweeter L-pad resistors (3.9 and 1ohm) before the 22uf. Never seen that before. L-pads are almost always placed last. So you might want to have them switch places. Ignore that. I'll rephrase that shortly.

Edit: You put an L-pad first for the tweeter crossover. I have never seen that done before. Typically L-pads are placed last. Typically what people do is have a resistor value first, then another resistor AFTER the cap and inductor to adjust tweeter levels. So try removing the 1ohm and instead add a resistor after the cap to get the desired result.

2. 1.8mh on a 4ohm woofer seems excessive and your crossover does look a bit boomy in the low frequencies. So you might want to lower that value and see how it sounds. Your simulation had too little BSC, now you might have too much.

Could you show the individual woofer/tweeter crossover results in REW?
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: wushuliu on 25 Feb 2020, 06:49 pm
I should also say, please make sure to listen to both speakers as you make all these changes. That way you get a feel for what each change does and whether you like what you hear.
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: Florent on 25 Feb 2020, 08:07 pm
About the lpad i Will try it.

For the 1.8mH, i tried 1.2, 1.6, 2, and 2.2mH
<1.8 there were big bumps in the 600~1200hz but less boomy
>1.8 no difference. It will probably sound boomy but i think i was at less than 2ft from the wall. On the other hand, it Will give me the oportunity to cut those peaks in the low end with dsp without sacrifying to much volume. Does that seem correct ?
But i will try ! I am far from done with all this :-p
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: Florent on 25 Feb 2020, 09:02 pm
I found that "equalizer apo" software on windows that let you import REW filters. Seems to work prety well
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: Florent on 27 Feb 2020, 07:14 pm
I improved my setup for taking measurements, did another round of tests by switching values one the caps, inductors and resistors,

I tried to lower the inductor's value but couldn't get the 500-1000Hz to stay flat so went back to 1.8mH
As for the Lpad, tried to put it before and after the cap, one resistor before, one after, but it didn't change anything by measurement or ear (wich are not really great in my case) So I kept the same values and set it after the cap, as suggested.
I also changed the value on the cap, looks better.
After "noodleing around" I measured the drivers separately and was kinda surprised that they cross at only 1500Hz.

As you can see, I have a bump in the <100Hz, up to 8dB, I kinda like that so I'll leave it that way but if I wanted to damp that, what can I do ? Add a capacitor ? Lower the enclosure's volume ?
Each horizontal line is 5dB

Did some paint job, not satisfied, cheap spray can... I will sand it again and paint it with better quality paint.

What do you think ?

(https://www.audiocircle.com/image.php?id=205278)
(https://www.audiocircle.com/image.php?id=205279)
(https://www.audiocircle.com/image.php?id=205280)

Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: wushuliu on 27 Feb 2020, 07:49 pm
I improved my setup for taking measurements, did another round of tests by switching values one the caps, inductors and resistors,

I tried to lower the inductor's value but couldn't get the 500-1000Hz to stay flat so went back to 1.8mH
As for the Lpad, tried to put it before and after the cap, one resistor before, one after, but it didn't change anything by measurement or ear (wich are not really great in my case) So I kept the same values and set it after the cap, as suggested.
I also changed the value on the cap, looks better.
After "noodleing around" I measured the drivers separately and was kinda surprised that they cross at only 1500Hz.

As you can see, I have a bump in the <100Hz, up to 8dB, I kinda like that so I'll leave it that way but if I wanted to damp that, what can I do ? Add a capacitor ? Lower the enclosure's volume ?
Each horizontal line is 5dB

Did some paint job, not satisfied, cheap spray can... I will sand it again and paint it with better quality paint.

What do you think ?


Since the goal (IMO) is learning the basics, I think you are off to a solid start, especially considering how little information has been provided.

1. Below, say 300hz, the room will dominate your response measurements at 1m. So what you are seeing is I assume the effect of the speakers being closer to a wall/boundary. If you want to reduce that the easiest way is to stuff the port. You also want to make sure to have stuffing inside the speaker like polyfill or cotton batting or wool (I prefer wool). Adjusting all of that will impact the bass response.

2. I didn't realize you were crossing the tweeter that low. I don't think that tweeter can handle down that far. You never want to cross down to the tweeter's Fs. You want to cross no lower than double the Fs. In this case the Fs of the ND25 is 1350. So you need to be crossing no lower than 2.5k - which is what PE recommends in their specs. It's possible you may damage the tweeter if you cross that low at high volumes.

So again there are some really critical basic steps/info you are missing. I encourage you, again, to go to the PE Techtalk forum and get help there. They are really helpful to newbies and you will get a ton of responses and even crossover schematic recommendations. It's been interesting but I'm not going to offer any more help here because I think it's doing more harm than good.
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: Florent on 27 Feb 2020, 08:38 pm
Since the goal (IMO) is learning the basics, I think you are off to a solid start, especially considering how little information has been provided.

1. Below, say 300hz, the room will dominate your response measurements at 1m. So what you are seeing is I assume the effect of the speakers being closer to a wall/boundary. If you want to reduce that the easiest way is to stuff the port. You also want to make sure to have stuffing inside the speaker like polyfill or cotton batting or wool (I prefer wool). Adjusting all of that will impact the bass response.

2. I didn't realize you were crossing the tweeter that low. I don't think that tweeter can handle down that far. You never want to cross down to the tweeter's Fs. You want to cross no lower than double the Fs. In this case the Fs of the ND25 is 1350. So you need to be crossing no lower than 2.5k - which is what PE recommends in their specs. It's possible you may damage the tweeter if you cross that low at high volumes.

So again there are some really critical basic steps/info you are missing. I encourage you, again, to go to the PE Techtalk forum and get help there. They are really helpful to newbies and you will get a ton of responses and even crossover schematic recommendations. It's been interesting but I'm not going to offer any more help here because I think it's doing more harm than good.

I ordered stuffing, for now i filled the speaker with a sweather...
I didn't know about the correlation between Fs and crossover point ! I'll try again with that in mind. I REALLY appreciate all the help you gave me ! I think i'll try to find some "speaker building for dummies" kinda book, to fill the gaps and go further but it's hard to find something in french.

Thanks again, hope to be back in no time with a new project and some more knowledge !
Title: Re: First DIY 2 way stereo speakers. What am i doing ?
Post by: wushuliu on 27 Feb 2020, 08:42 pm
Then maybe try Diyaudio.com forum. It's more international with a dedicated multi-way speaker section. Plenty of french-speaking/bilingual folks there as well.