New (Small Home Studio) Build, Norway

[studioNorWay]

Merry Christmas everyone

New measurement done. The measurement was done based on description here:
http://www.johnlsayers.com/phpBB2/viewt ... =3&t=21122

My gear setup:
Mic: PreSonus PRM-1
Sound level meter: Extech-407732

Calibration:
Calibration REW to sound card done as explained in the REW help section. Calibration file is the same as done on a previous measurement.

Any help / comments for interpret the REW graphs will be highly appreciated.

Find attached mdat file below.
https://drive.google.com/open?id=1WnNAl ... vEPFTKL7gM

Note
You can find my previous measurement here
http://johnlsayers.com/phpBB2/viewtopic ... 3&start=45

Calibrating levels

measure_01.png

Left side speaker level check

measure_02.JPG

Right side speaker level check

measure_03.JPG

Measurement

measure_04.JPG

[Gregwor]

Your RT60 is very low (often living around 50ms). I understand your room is small but that seems extremely low now. And the <100Hz range seems to have really dropped off with your new measurements. Was there any changes made to your speakers? Do you own a subwoofer?

Also, you seem to have a strong reflection present in your right speaker and both speaker measurements. Here is the how far it is:

Reflection.png

Use the string trick to find out where this reflection is coming from.

Greg

[studioNorWay]

Find attached some measurement comparisons below. The first measurement is before the room treatment (flush mounted speakers, slots and celling clouds).
Second measurement is after installation of room treatment. Still haven’t build the back corner base traps.

COMPARE SLS

compare SPL.jpg

First measurement waterfall

meas_01 waterfall.jpg

Second measurement waterfall

meas_02 waterfall.jpg

First measurement spectogram

meas_01 spectrogram.jpg

Second measurement spectogram

meas_02 spectrogram.jpg

[studioNorWay]

Your RT60 is very low (often living around 50ms). I understand your room is small but that seems extremely low now. And the <100Hz range seems to have really dropped off with your new measurements. Was there any changes made to your speakers? Do you own a subwoofer?

Also, you seem to have a strong reflection present in your right speaker and both speaker measurements. Here is the how far it is:

Reflection.png

Use the string trick to find out where this reflection is coming from.

Greg

Hi Greg.

I will try to research the reflection. The changes to the speakers is that they are now flush monted. I do not own a sub.

Bjorn

[TomessAI]

I've looked at your measurement and I have a stupid question: did you seal the Presonus Eris E5 back after removing the amp from it? I've looked at the specs and they should go down to 53 Hz. The loss of bass and the deep notch at 90 Hz looks a bit like you have an acoustic short circuit. But it could be a nasty room mode, too. Also, it seems like the amp is not inteded to be removed as far as I can tell from the pictures on it's product site. Does the amp supplant a siginifcant amount of air in the cabinet of the speaker? Because if so, you might have detuned the bass reflex resonance frequency, which will also result in a bass roll off.

[studioNorWay]

So, regarding the low RT 60 let’s go in details of what has been done after first measurement.

First. After the first measurement and before the room tuning started the room was a bit too "dry" (slightly too dead). It was almost uncomfortable to be in it. felt like a pressure feeling on the ears. It's a very small room, so the goal was to increase the decay times a bit. Sins the room is built inside out I added I added more reflection surfaces around the room, and some other stuff to deal with a few early reflections, plus some targeted bass trapping for the modal issues (that is coming next).
Anyway, this is what Stuart suggested and I hired a few hours from him to help me with the design. He ended up designing the soffit mounting of the speakers, side slot walls. He was also the one to suggest that I mount the back side of the Eris speakers on the wall.

Anyway today the room feels much better and sounds pretty good. But as we can see the measurements are still not so good.

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Could be I thrusted him to blindly and are now suffering the consequence.

Was there any changes made to your speakers?
Greg

My last respons was a bit unaccurate.
Due to loss in weight of the speakers when removing the amp I had to add a 2 kg concrete blocks inside the speakers together with a thick aluminium back plate. The weight was added due to the speaker is floated on carefully calculated Sorbothane pads inside the enclosure, and the enclosure is then floated on different Sorbothane pads, that are compressed to the exact tension using the turnbuckles. This was also something Stuart asked me to do. After removing the amps, the weight was to low to get the tension right. So, I got the speaker weight to about 5,7 kg for each speaker. The tension could be a bit off sins Stuart left this site and can’t be reached anymore. The actual tension based on his calculation was the last bit I was waiting for from him. But as other people also has experienced hi did not follow though until the end on my project either, so I am missing that part and had to improvise.

IMG_7268.JPG

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IMG_7270.JPG

I've looked at your measurement and I have a stupid question: did you seal the Presonus Eris E5 back after removing the amp from it? I've looked at the specs and they should go down to 53 Hz. The loss of bass and the deep notch at 90 Hz looks a bit like you have an acoustic short circuit. But it could be a nasty room mode, too. Also, it seems like the amp is not inteded to be removed as far as I can tell from the pictures on it's product site. Does the amp supplant a siginifcant amount of air in the cabinet of the speaker? Because if so, you might have detuned the bass reflex resonance frequency, which will also result in a bass roll off.

Thanks TomessAI for chipping in. Yes as you can see I sealed the back side with a thick aluminum plate. I will contact the manufacture of the speakers and ask them about the amp. Could be that I must change both speakers to something more suitable.

I now feel that this was quite a draw back sins I am so close to finish. But what can you do.

[Gregwor]

Due to loss in weight of the speakers when removing the amp I had to add a 2 kg concrete blocks inside the speakers together with a thick aluminium back plate.

This is probably what totally screwed up your low end. The volume (area) of the speaker cabinet has now been drastically reduced which completely changes the performance of the speaker. If the speaker would have sounded equally as good with a volume (area) that small, the company would have built it that size. We all want our material goods smaller in our lives, but when it comes to speaker enclosures, there are rules of physics that we just cannot change. Again, I'm guessing, but I bet this loss of volume (area) is the cause of the bottom end drop off. I also would have used a similar type of wood as the original construction to cover the hole on the back of the speakers as the aluminum could be messing with things as well.

Your construction looks great and you should be proud! Don't be discouraged. Stuart is a brilliant man. Ideally what should have happened was a Sorbothane calculation adjustment based on the new weight of the amp-less speakers.

Greg

[studioNorWay]

This is probably what totally screwed up your low end. The volume (area) of the speaker cabinet has now been drastically reduced which completely changes the performance of the speaker. If the speaker would have sounded equally as good with a volume (area) that small, the company would have built it that size

Good point. Even though the amp itself takes a bit of space the concrete block takes a bit more. That could be the cause. I will take out the concrete block from one speaker and do a measurement so we can compare one speaker with the block and one without.

IMG_6917.JPG

I also would have used a similar type of wood as the original construction to cover the hole on the back of the speakers as the aluminium could be messing with things as well.

Well the back hole is already covered with the amp back plate originally. Witch is aluminium. So I guess that covering the hole with another aluminium plate should work right?.

Your construction looks great and you should be proud! Don't be discouraged.

Thanks Greg. I’m just get frustrated when I must do over stuff I thought was after the book.

Stuart is a brilliant man. Ideally what should have happened was a Sorbothane calculation adjustment based on the new weight of the amp-less speakers.

I know he knows his stuff and then some, just frustrating sometimes when people do not complete what was promised. Anyway, enough about Stuart. I should have done measurements right after the speaker weight enhancement to check. So, note to self: "don’t fill speaker enclosers with concrete". Anyway, when I remove the block from the speaker, I will probably be way of the original Sorbothane calculation. I am bit unsure how this is calculated and how to tighten the turnbuckles for correct tension.

This is the types and setup I have used:
The weight of the speakers without the backside (amp) is 2.72 kg each + the aluminium back plate.
The cabinet for mounting the speaker in the wall weight are 7 kg each.

Bottom pads (under the speaker, inside the enclosure box) (40 duro Sorbothane, 1" thick)
Side pads (40 duro Sorbothane, 1" thick):
Top Pads (40 duro Sorbothane, 1" thick):
Base pads (under the entire enclosure box), (30 duro Sorbothane, 1" thick):

Thanks again
Bjorn

[studioNorWay]

Now I have removed the concrete block on the right speaker, put everything back in place and made a new measurement.

Find attached mdat file below.
https://drive.google.com/open?id=1cCvlH ... 2l3ePLvvQX

Bjorn

[Waka]

I will probably be way of the original Sorbothane calculation. I am bit unsure how this is calculated and how to tighten the turnbuckles for correct tension.

As you can apply tension via the turnbuckles, you don't need to calculate. You just tighten until you get the correct deflection. Measure the height of the sorbathane prior to applying any tension/weight. Then tighten the turnbuckles until the height is 15-20% reduced.

The weight of the speaker would only matter if you were resting the speakers on the sorbathane without any turnbuckles etc.

If the sorbathane underneath the enclosure can't be compressed enough with the lighter speakers (unlikely to be the case), just remove an inner sorbathane pad to distribute more weight on the others.

Dan

[Gregwor]

Removing the concrete gave you ~5dB increase in bottom end and what appears to be a more even response overall. That's good news!

Greg

[studioNorWay]

As you can apply tension via the turnbuckles, you don't need to calculate. You just tighten until you get the correct deflection. Measure the height of the sorbathane prior to applying any tension/weight. Then tighten the turnbuckles until the height is 15-20% reduced.

The weight of the speaker would only matter if you were resting the speakers on the sorbathane without any turnbuckles etc.

If the sorbathane underneath the enclosure can't be compressed enough with the lighter speakers (unlikely to be the case), just remove an inner sorbathane pad to distribute more weight on the others.

Dan

Thanks Dan for taking the time to comment. I will do as you described. There will be no problem to compresse the sorbathane enough with turnbuckles as they are very robust. So, this solves the sorbathane underneath the enclose. But what about inside the enclosure. There I also have sorbathane (underneath, on the sides and at the top). Will the same principle also apply here? 15-20% reduced? Here I can probably apply more sorbathane on top if I’m not able to compress the bottom ones enough. What about the sorbathane on the sides?

enclosre1.jpg

enclosre2.png

[studioNorWay]

Removing the concrete gave you ~5dB increase in bottom end and what appears to be a more even response overall. That's good news!

Greg

Thanks Greg for checking. That is better news! I will remove the other one as well.
Also, I have talked to Presonus teck. He stated:

The modifications that you have made will indeed alter the audio. Each speaker is designed to interact with its individual acoustical environment. The way to restore your bass issues is to restore the amp paneling.

So, this means I have some issues here as well. I’m wondering if I must change my speakers overall. Isn’t it normal to wall mount the amp from the speakers? I have seen studio projects on this site doing the same. Do they have special kind of speakers where the back amp is intended to be wall mounted? If so what kind am I looking for here?

Bjorn

[TomessAI]

Also, I have talked to Presonus teck. He stated:

The modifications that you have made will indeed alter the audio. Each speaker is designed to interact with its individual acoustical environment. The way to restore your bass issues is to restore the amp paneling.

So, this means I have some issues here as well. I’m wondering if I must change my speakers overall. Isn’t it normal to wall mount the amp from the speakers? I have seen studio projects on this site doing the same. Do they have special kind of speakers where the back amp is intended to be wall mounted? If so what kind am I looking for here?

Bjorn

There are some brands of (active) speakers (I only know Genelec, but there are more as far as i know) that have a sealed speaker cabinet where the aluminium back plate with the amp is not the back of the cabinet itself. Therefore, disconnecting the aluminium back plate does not alter the cabinet volume and its acoustic behaviour. But those are quite expensive speakers compared to the Presonus Eris E5 you have. However, replacing the back of the speaker with a sealed aluminium back plate should work fine in general, but your speakers are so small, that the amount of electronics and the air that they supplant seems to have an impact on the bass reflex resonance frequency. And this resonance frequency defines the lowes frequency that the speaker is capable to reproduce.

[studioNorWay]

There are some brands of (active) speakers (I only know Genelec, but there are more as far as i know) that have a sealed speaker cabinet where the aluminium back plate with the amp is not the back of the cabinet itself. Therefore, disconnecting the aluminium back plate does not alter the cabinet volume and its acoustic behaviour. But those are quite expensive speakers compared to the Presonus Eris E5 you have. However, replacing the back of the speaker with a sealed aluminium back plate should work fine in general, but your speakers are so small, that the amount of electronics and the air that they supplant seems to have an impact on the bass reflex resonance frequency. And this resonance frequency defines the lowes frequency that the speaker is capable to reproduce.

I understand. I think I will use this year to investigate different speakers. Until then I will use the once I have. Anyway, I have an extra speaker (same kind) that has not been taken out of the box. When I take out the cement block from the left speaker I will insert the untampered new speaker and run measurement again. I will use this measurement for reference to see the difference of one speaker with amp back plate (left side) and one (right side) with aluminum back plate.

Thanks again for commenting.

Bjorn