Speakers measurements with Room EQ Wizard

[marcop999]

Hi,

Today I have used for the first time Room EQ Wizard with my mic behringer ecm8000 to measure my old DIY speakers.

All drivers was measured at only 2 cm from mic.

After these measure I got confirmation that the crossover need an upgrade.

First is clear that the woofer is not 90 dB like the midrange and the tweeter (as usually happens).

There is a strange unstability at 170/200 Hz that happen only if the woofer is inside the box, but is not clear the cause.

The measurements are very different from the simulation (2010) like I expeced but I don't sure how I can interpret these differences.

I have simulated a possible crossover update (2023) with more flat frequency response.

Any suggests ??

Thank you !!

 

[ctrlx]

measure the tweeter and mid farfield gated at least 60cm
for bass use nearfield around 5mm

 

[63781]

Some suggestions :

• Position the speaker as far from room surfaces as possible.
• Measure all drivers with the same mic position and use gating (IR Windows in REW) to avoid early reflections. 6-10 ms will usually work.
• Measure at 1 meter distance. Near-field measurements will get proximity effects and will not capture the effects of baffle diffraction.
• Measure each driver individually. Disconnect the other drivers when measuring one of the drivers.
• Use 1/6 oct smoothing on your measurements.

And please share which drivers you are using, and the current crossover schematic.

 

[picowallspeaker]

There is a strange unstability at 170/200 Hz that happen only if the woofer is inside the box, but is not clear the cause.

2 cm in front of the cone is different than 200 cm. I guess after 20 cm it already starts to be omnidirectional, so it looses some pressure, the one you measured
it's called baffle step loss

 

[63781]

Baffle step does not look like that at all. I guess its a resonance inside the box itself. What kind of stuffing is used inside the box?

 

[picowallspeaker]

Why not? All the radiation scientology talks about that!

 

[marcop999]

Thank you all for your reply, but I think I have found the cause: there is a lack of damping material. What's inside is not enough.

I will add it on the bottom and on the top.

I have already purchased this (sonofil):
https://www.audiokit.it/it/fonoassorbente-fonoassorbente/273201-sonofil-black-fonoassorbente.html

What do you suggest to fix it on top ? on the bottom I think is more complicated.

 

[63781]

Why not? All the radiation scientology talks about that!

In Scientology perhaps, but in science? Not so much.

A typical baffle step response looks like this:

And not in any way like that :

 

[63781]

From your measurements it looks like you have a bass reflex box, so filling the entire volume is not a good idea. However, covering the crossover should not be a problem. Put in at least 5 cm damping on all internal surfaces, and measure again to see if that resonance at 200 Hz is reduced.

 

[picowallspeaker]

I see some (several) errors ( most common) in that inside of the enclosure.
Whos's gonna spot the errors?

 

[marcop999]

Hi picowallspeaker,

After ask to other this matherial:
https://www.audiokit.it/it/fonoassorbente-fonoassorbente/273201-sonofil-black-fonoassorbente.html

and they tell me that probably is not enough for this reason I would try to combine other matherial like this:
https://www.monacor.com/products/components/speaker-technology/diy-/mdm-2/

but is not clear to me what glue use to combine the two and fix it to the wood.

I thought of the classic 'Attack' that we have in Italy but I don't sure if is good this this purpose.

 

[picowallspeaker]

First of all, I'd take all those boards outside. And remove all the plug system, the less contacts, the better
Second, I'd put T-nuts for allowing a tighter hold of the speakers. And remove that foam around the perimeter of the woofer.
Third, yes, put better damping material. Use "mastice" (bostik)