3-way floor standing speakers build thread

[TLS Guy]

TLS Guy,

thanks for the feedback: do you have any recommendation on how to reduce the issue? More Polyfill? less?

The box is made by 36mm of wood, thick enough you can walk on it, the internal surface is hardened by paint and it's sealed with putty in every corner. Do you think is "leaking" air? I can make it stronger as much as I like, as long I'm sure I'm doing the right thing

thanks!

cheers

You have made a common mistake. You can use wood as thick as you want, and it will still flex. Interlocked bracing is the only answer to this problem.

The box should be filled wit polyfill but not compacted.

What ever you do you will end up with a high F3 in this design. The impedance curve proves it. I warned you about this at the start of the project.

 

[stonemarten]

TLS Guy,

I did internal bracing, but, based on your comments, I'll try to do more.

About F3: the results is lower than the expected in the previous post (95 vs 105 Hz). I will add the subs of course later

thanks for your review!

cheers

 

[highfigh]

Look at the long dimensions for the answers to what needs to be braced. Since you have a way to measure acoustic response, set it up and tap your finger (fairly strongly) on all of the long sides of the box, in different places along the centerline. You'll notice some spots that excite a particular frequency more than others. Put a piece of tape on those spots. Once you have marked them, press a finger from your other hand next to the spot you marked- you should notice that the frequency which had been excited before, is no longer as strong. If you have scraps of the wood (long grain, not across the grain of a board), cut a piece that's just longer than the space between the sides and round one end, to allow it to be moved into position to stay where it is without glue. Tap on the sides again and check the response- the frequency should be less of a problem and if you move it to different places, you should see different effects. This is like the tuning post in a violin.

 

[stonemarten]

I've made a "test box" that is a replica of the real one, for testing purpose. I notice that with a slightly larger box (you can tell by the F(s)), braced as before, I don't have that "peak"



shouldn't be the opposite? I mean, if the box is not rigid, make it larger just increase the defects, but, based on the previous feedback, not now.
confused... maybe I need to test again the drivers in the main box...
Can you please point me to any documentation on how to understand box rigidity by the impedance curve? Can't find any
what do you think about this one?

thanks!

cheers

 

[highfigh]

I've made a "test box" that is a replica of the real one, for testing purpose. I notice that with a slightly larger box (you can tell by the F(s)), braced as before, I don't have that "peak"

View attachment 17215

shouldn't be the opposite? I mean, if the box is not rigid, make it larger just increase the defects, but, based on the previous feedback, not now.
confused... maybe I need to test again the drivers in the main box...
Can you please point me to any documentation on how to understand box rigidity by the impedance curve? Can't find any
what do you think about this one?

thanks!

cheers

Changing the dimensions moves the peak up or down, depending on whether it was made smaller or larger, respectively. However, different materials resonate at different frequencies, based on density and stiffness. A lightweight, compliant material will resonate freely at a wider range of frequencies than a light, stiff material. Dense materials will require more energy to cause resonance and if the resonant frequency is excited, it may continue to move after the signal stops (called 'ringing'). The speaker's impedance curve has nothing to do with the box until it has been mounted and then, you not only have the air in the box to contend with WRT the Fb (resonant frequency of the box) but the box, itself.

You don't want to tune a box so it has strong peaks in the response, especially if it's ported. A sealed box can be tuned to have a peak, but it's not going to be as strong or as bad for the overall response.

 

[TLS Guy]

I've made a "test box" that is a replica of the real one, for testing purpose. I notice that with a slightly larger box (you can tell by the F(s)), braced as before, I don't have that "peak"

View attachment 17215

shouldn't be the opposite? I mean, if the box is not rigid, make it larger just increase the defects, but, based on the previous feedback, not now.
confused... maybe I need to test again the drivers in the main box...
Can you please point me to any documentation on how to understand box rigidity by the impedance curve? Can't find any
what do you think about this one?

thanks!

cheers

I can't be certain that the previous peak was due to wall flexing, but I think that unlikely. It might have been ripple.

However the new box is very resonant, with impedance ripples due to cabinet resonance at 750 Hz, 1 KHz, and 3.5 KHz. The first two are broad based and will be audible.

The impedance resonance of the speaker is still at 100 Hz.

Your fundamental problem is that you have a speaker with all the disadvantages of a three way and none of the advantages.

To justify the expense and headaches solving the numerous problems of three ways you need an F3 in the low thirties at least. The F3 of this design is at least two octave too high.

The fact is that I could design a diminutive bookshelf, along the lines of the ATC SCM 1 that would blow that speaker out of the water in fidelity.

I'm sorry I don't think that design is salvageable unless you are lucky enough to find a driver that can work optimally ported in that volume. I fear that will be a stretch.

I think you are going to have to cut your losses and chalk that one up to experience.

It is not going to be worth the cost of the crossover components.

I'm going to expand further on the latter. If you add a sub you will effectively have a four way speaker with the first crossover at 120 Hz. This is high enough it needs to be custom. Now in order to handle the bandpass gain you will need the cross to the mid no lower than 720 Hz. The next crossover to handle bandpass gain will need to be at 4320 Hz, at a stretch 4 KHz. So you will need and exotic and expensive mid with a response to 4 KHz that at least rolls of smoothly at that point or has an even greater extended response.

Three ways and even more so four ways with the crossover points too close together sound just awful.

With you next design carefully think the issues though and model, model and model again and again, before your first saw cut and driver purchases.

 

[stonemarten]

Dear experts,

After several hours spent reading, studying and testing my speaker this is the result. I would have your feedback on the outcomes and my assumptions. What I would to do is something like John Lenard Burnett describes in his education articles (http://education.lenardaudio.com/en/06_x-over.html)

I understand and appreciate your comments above, and would know what do you think on a different approach, supported by measurements and Mr. Lenard experience. I think most of us are here for learn and become more creative without real life company profit and time constrain… so again, I will really appreciate your feedback and pro/cons on my project.

I’ve added another woofer, so now the speaker is in the MWMWW configuration.

Crossover points: 600Hz (2nd order BW) and 4000Hz (3rd order BW). Plan to crossover the 2 subs around 120Hz.

I’ve tried higher order (4th and 5th) but I can’t get a real flat curve and didn’t like the sound. I’m using a digital crossover (MiniDSP), so I’m free to change and/or EQ as much as is needed. All the drivers are connected directly to 2 Crown 1000 XLS

All the measurements are done with an UMIK-1 and verified thanks to the great REW forum help. All the .mdat files with the raw results are available

Cabinet stiffness test

Set up: 90dB, mic at 2cm from the cone, indoor, smoothed 1/48



After overlap with the drivers makers FR, I didn’t notice any big differences, except in the woofers after 200Hz where I have a slightly faster roll off, as expected.

Based on that, I assume that I don’t have any standing waves and the box is stiff enough.

Comments?

Acoustic delay

Set up: 80dB, Audissey mic at 1 meter, indoor

I’ve used the loop feature in REW for calculate the acoustic delay, switching the mic because the UMIK is an USB one and it’s not possible to get the value. Below the inverted polarity measurements (80dB, mic at 1 meter, outdoor, gated) for validate the delay



The delay input in the MiniDSP is what was measured.

This is the point where I’m less sure: the reversed spike is clear between T and M but is not exactly on the 4kHz mark, and between M and W there isn’t a clear spike, and the highest point is not on the 600Hz.

What do you think? Is it correct? I can easily modify the delay, so any recommendation here on how this FR should looks like is welcome!!


Single driver response

Set up: 80dB, mic at 1 meter, indoor, gated

Individual driver response



Frequency response

Set up: 80dB, mic at 1 meter, outdoor, gated

EQ: TW high shelf at 17k, 4dB gain, Q=1, WF low shelf at 150, 4dB gain, Q=1



Zoomed



No gate, 1/48 smooth



What do you think? Does the EQ make sense? Too much? Not too much?

 

[stonemarten]

Phase

Same set up

Here is where I’ve really no idea if I’m right or not, and can’t find any good before/after example… every comment and links are more than welcome



Off axis

Set up: 80dB, mic at 1 meter, indoor, gated

Purple: on axis

Red: 15 deg

Green: 60 deg



Do you think it’s ok?

Thanks in advance to everybody!

cheers

 

[stonemarten]

Dear experts,

anybody has got comments? I will really appreciate...

thanks!

cheers

 

[stonemarten]

I read with extreme interest this post about measurements

https://www.audioholics.com/loudspeaker-design/audio-measurements

I think I'm aligned with what Gene is saying... again, any comment appreciated!!

cheers

 

[lsiberian]

For proper alignment in custom systems I always use the listening area as your basis for measurement in a custom system because you control that.
Step 1- Dial in speaker placements based on measurements at the listening position
Step 2- Adjust crossovers and eq based on measurements at the listening position

If you do that you'll have the best sound possible. Obviously you'd do things differently if you planned to sell the speakers, but the beauty of building your own is that you can tailor it for you room specifically.

3db is considered the acceptable tolerance. For that the measurements already look pretty good.

 

[stonemarten]

lsiberian,

For proper alignment in custom systems I always use the listening area as your basis for measurement in a custom system because you control that.
Step 1- Dial in speaker placements based on measurements at the listening position
Step 2- Adjust crossovers and eq based on measurements at the listening position

If you do that you'll have the best sound possible. Obviously you'd do things differently if you planned to sell the speakers, but the beauty of building your own is that you can tailor it for you room specifically.

3db is considered the acceptable tolerance. For that the measurements already look pretty good.

thanks very much for the feedback! I'm planning to do that later: I would start first from a known base for make my life easier
I would achieve the best "house curve" possible

cheers

 

[stonemarten]

Dear Experts,

I would like to know your opinion on the final result that I got from my project. Below the FR, Phase, distortion and polar response
please note that they will be crosser over at 120Hz with the subs, and I'll refine the LF response in room



What do you think?

thanks in advance for all the comments!!

cheers

 

[TLS Guy]

Dear Experts,

I would like to know your opinion on the final result that I got from my project. Below the FR, Phase, distortion and polar response
please note that they will be crosser over at 120Hz with the subs, and I'll refine the LF response in room

View attachment 22412 View attachment 22413 View attachment 22414

What do you think?

thanks in advance for all the comments!!

cheers

You have a nice mid band response, but it looks as if the response is falling off below 200 Hz.