John Sayers' Recording Studio Design Forum Archive

Ok. I'm gonna get this.. Now the calibration is looking as it should, flat.

I checked the SPL Meter with an external meter.

Ran the tests from 25hz to 20khz.

Here's the new file:
https://www.dropbox.com/s/t2om7q76dxj9o ... .mdat?dl=0

Thanks for your patience and your help Stuart

Now the calibration is looking as it should, flat.

Yes! That's what a calibration curve should look like. So we are fine there.

I checked the SPL Meter with an external meter.

Yes! You have the levels pegged perfectly now. Don't touch that!

Ran the tests from 25hz to 20khz.

Great! Let's expand that a little more, as it looks like there's some interesting stuff going on at both ends. Make it 18 Hz to 22 kHz.

Here's the new file:

Well, 3 out of 4 ain't bad... There's basically only one reading in that file, repeated 3 times. It's the exact same measurement done at three different levels. But what I need is measurements done with different SPEAKERS! In other words, for the first measurement, walk over to your RIGHT speaker and physically turn it off, so it cannot produce any sound: Allow only the left speaker to produce sound. Do a measurement like that, then WITHOUT TOUCHING ANY SETTINGS, walk over to your LEFT speaker and turn it off, then walk over to your RIGHT speaker and turn it on. Do the second measurement like that. And once again, WITHOUT TOUCHING ANY SETTINGS, walk over to your LEFT speaker again and turn it back on, so that BOTH speakers will be producing sound, and do the final test. Do not touch anything at all in between tests: no settings on your computer, console, pre-amp, interface, and above all, don't touch the mic or any furniture in the room. All three tests must be done with absolutely identical situation in the room.

You are nearly there...


- Stuart -

Awesome! progress haha.

Ok here are the tests with Left and Right separate.

My right monitor is showing 3-7db lower than my left monitor

here's the mdat: https://www.dropbox.com/s/aohbiblp9srhv ... .mdat?dl=0

Well. Sounds like my speaker is blown. ugh.

My local repair shop has a 2 week lead time.. So won't be doing more tests anytime soon..

In the meantime I'm going to get started on framing.. Just finished building some speaker stands instead of using cinder blocks.. Copied the Argosy 420Xi design and I'll be getting the isoacoustic stands for the tops.

Trying to stay positive as I'm sure my monitor fix will not be cheap

Its strange that you say the speaker is broken, the frequency curve is the same as the good speaker. Could it not be that the volume of that speaker is a bit lower that the other? either by the amp being with lower volume or not being as effective on that channel? or maybe due to the proximity to the microfone?

omega-t-k wrote:Its strange that you say the speaker is broken, the frequency curve is the same as the good speaker. Could it not be that the volume of that speaker is a bit lower that the other? either by the amp being with lower volume or not being as effective on that channel? or maybe due to the proximity to the microfone?

I'd say you were correct and I wish it were something like that, but the one woofer is actually distorting. I tried different audio sources, different cables, switching it from Right to Left Speaker setting.. All with the same result of distortion.

too bad then lets just hope they fix it properly with identical parts. dont forget to "break in" the new speaker before measuring again, otherwise you will have differences in sound between the old and new

omega-t-k wrote:too bad then lets just hope they fix it properly with identical parts. dont forget to "break in" the new speaker before measuring again, otherwise you will have differences in sound between the old and new

good news! it was just a loose connection.. only $120 in labor to fix!

So I've made some progress since my speaker problem...

I finished the front and side walls, and the one rear corner bass trap. On the side walls the fabric takes the shape of a resonator, but they are not sealed, nor have any slats. I went this way for looks and to cover up the window completely.

The front bass traps are superchunk tightly in the corner, plus 4 pieces of 16"x48" roxul standing, to help fill that entire space.

I still need rear wall treatment and the door/corner treatment.
I also plan to remove the ceiling fan to install 3 more panels.


I've updated my drawing to show what it currently looks like..

Just ran some new tests too... I definitely am in need of the rear wall treatment. With a simple clap you can hear echo's in certain parts of the room. Also, the rear of the room is all bass at the moment.

Here's the new mdat file: https://www.dropbox.com/s/u1085j0aa5ujf ... .mdat?dl=0

good news! it was just a loose connection.. only $120 in labor to fix!

Cool! The new data is looking more consistent between left and right.

Just ran some new tests too... I definitely am in need of the rear wall treatment.

Yup. ...

That huge spike with the long tail at 134 Hz is your 3.0.0 mode. 3rd harmonic, front/back axial mode. Back wall needs LOTS of treatment...

The big dip at about 90 Hz is likely your 2.0.0 mode. The flip side of the same one above: 2nd harmonic, instead of third.

And the big humpy thing at around 45 Hz is yet another aspect of the same issue! That's your 1.0.0 mode. fundamental. It is probably smaller than the others in the graph because your speakers don't go down that low, but it's clearly there.

So yup: rear wall needs major attention!

There's other stuff going on in there too, but that huge hairy axial monster is masking them: it will be easier to see them once you kill that thing.

You better order some "dragon slayer" special super hyper ultra traps for your back wall!


One other thing: Those speaker stands are going to need a lot more mass on them. They aren't hefty enough like that....

- Stuart -

Soundman2020 wrote: You better order some "dragon slayer" special super hyper ultra traps for your back wall!


One other thing: Those speaker stands are going to need a lot more mass on them. They aren't hefty enough like that....

haha! definitely will get on that

For the speaker stands would I be ok using Isoacoustics stands on them? (http://www.isoacoustics.com/isol8r430_s ... onitor.php)
Or should I rebuild them with maybe 1.25-1.5" MDF?

Thanks for your help on the graphs

For the speaker stands would I be ok using ... stands on them?

Well, I suppose you could if you don't mind spending a lot of money on items of questionable performance... On the other hand, for a few bucks you could put some tried-and-proven Sorbothane pads under the speakers, and get excellent isolation.

Those fancy stands would not solve the issue of lack of mass. Stand need to be MASSIVELY heavy. Some people stack up concrete blocks, others use hollow stands filled with sand. Right now, I'm working with a customer in the USA who is building his stands from 1/4" steel pipe... not that the pipe is 1/4" diameter, but that the steel itself is 1/4" thick! The pipes are 6" diameter, welded to a 1/2" steel plate base, and with a steel grid shelf on top for the speaker. That too will be sand filled. Sorbothane pads both under the entire thing, and also under the speaker. Overkill, perhaps, but he certainly has the right idea! Those speakers will be absolutely isolated and very well decoupled from the floor...

That's what I mean by massively heavy.

Or should I rebuild them with maybe 1.25-1.5" MDF

Something just a little heavier would be in order...

- Stuart -