Help, tweeter's frequencies dips

[picowallspeaker]

I wouldn't use any class D amplifier
Just see how it works : it's just too much ! ( over-engineering a simple thing such boosting a signal )

 

[Pacogun]

I manage to borrow my son's laptop (also Toshiba but Satelite L500D) for comparison also. It gives similar result with Acer Desktop!
Does it mean the first laptop is not good for these measurement?

 

[Pacogun]

I wouldn't use any class D amplifier
Just see how it works : it's just too much ! ( over-engineering a simple thing such boosting a signal )

Yeah, I know. However, I cannot resist the cheap price of this amp, US$35 delivered and can handle 4 ohm driver. Since this is my first project, I try to keep the expense low to get WA (Wife's Approval)
I tried to secure second hand amps that can handle 4 ohm driver from fleabay, but they end up sold for over AU$100 (beyond my budget)

 

[Greebster]

I tried to create exact same condition to test SB Acoustic 26STC Tweeter, using Toshiba L750D Laptop VS Acer Desktop. I do Not moving the mic and tweeter even a millimeter, only swap the mic plug and audio output plug. The Mic is UMIK-1 calibrated mic, set on 0 degree on axis.
Both desktop and laptop audio output are set to 100% and mic input volume to 65%.
However, bear with me everybody! Before I reveal the result, I found that to produce the same DB level:
- Muse D class amp's Volume has to be cranked up to 90% with Laptop, while
- Only 50% volume with Desktop

I am not too sure why like this. With my current knowledge (I am a noob), probably the laptop produce less voltage than the desktop, so laptop's audio output needs more amplification.

Now, the result for Laptop is in attached image: (still have dip)

Looks like the audio (amp) out of your T750 is the culprit causing the dip. This could be addressed with an EQ to smooth things out.
The reason for the difference in levels is that the Toshiba may only be outputting 0.9vac VS 2.0vac out of the Acer.

Would suggest using a USB sound card if this is really that much of an issue to manually correct.

 

[DavidL]

One thing I noticed on the graphs is that the Acer does not have the soundcard calibration box checked this time. I have to ask if you did calibrate the soundcards in both computers as shown in this link? Calibrating the Soundcard

Does appear that the Toshiba has some sort of problem going on if you did and I would not use it.

Also if you have not already discovered this, it might come in handy. The Online Help and Forum buttons at the top of the page are what you are looking for. Good luck.

http://www.hometheatershack.com/roomeq/

 

[Pacogun]

Looks like the audio (amp) out of your T750 is the culprit causing the dip. This could be addressed with an EQ to smooth things out.
The reason for the difference in levels is that the Toshiba may only be outputting 0.9vac VS 2.0vac out of the Acer.

Would suggest using a USB sound card if this is really that much of an issue to manually correct.

Thanks Greebster.
Yes, at the end Minidsp will be used for EQ ing.

 

[Pacogun]

One thing I noticed on the graphs is that the Acer does not have the soundcard calibration box checked this time. I have to ask if you did calibrate the soundcards in both computers as shown in this link? Calibrating the Soundcard

Does appear that the Toshiba has some sort of problem going on if you did and I would not use it.

Also if you have not already discovered this, it might come in handy. The Online Help and Forum buttons at the top of the page are what you are looking for. Good luck.

REW - Room EQ Wizard Room Acoustics Software

I did not calibrate the sound card as I read at HTS forum. Someone ask about this and they said it is unnecessary while using UMIK-1.

Is soundcard Calibration required with UMIK-1 ? - Home Theater Forum and Systems - HomeTheaterShack.com

MiniDSP UMIK-1 Microphone - Page 41 - Home Theater Forum and Systems - HomeTheaterShack.com

And I'll come back to you regarding unticked sound card on desktop measurement, I don't know why it's unticked, I tried to set both REW on Laptop and desktop on the same setting (puzzle-puzzle)

And what do you think about my son's laptop Toshiba L500D that gives almost similar FR with the desktop?
I prefer using the laptop (both run Win 7), because my desktop is running on WinXP that the support will cease on 2014, while I still need Windows to run the Plug In for Minidsp.

And thanks for the links, I will take my time to read them.

 

[Greebster]

The UMIK-1 has the sound card integrated into it so the cal file includes the sound card frequency response. Many of us have them around these parts, I have two. A real calibration microphone is the actual pickup element with it's calibration and then a separate preamp and it's calibration. The two will add and subtract from one another so it's necessary to have both for accurate results.

Build a new desktop, dual boot config or run XP in a virtual machine. Problem solved

OT... think I just stopped sweating, almost 10:30pm here and it just got down to 74°f ... we broke a record high with 86°f on the first day of bloody winter! LOL

 

[Pacogun]

The UMIK-1 has the sound card integrated into it so the cal file includes the sound card frequency response. Many of us have them around these parts, I have two. A real calibration microphone is the actual pickup element with it's calibration and then a separate preamp and it's calibration. The two will add and subtract from one another so it's necessary to have both for accurate results.

Build a new desktop, dual boot config or run XP in a virtual machine. Problem solved

OT... think I just stopped sweating, almost 10:30pm here and it just got down to 74°f ... we broke a record high with 86°f on the first day of bloody winter! LOL

Thanks Greebster for the info.

Regarding the temperature, there must be feeling like in down-under country here (Melbourne). It is summer here. But we also got unusual early summer chill 15degree Celsius. Now, we got back normal summer temperature again 30 degree Celsius or in your American term 86 degree fahrenheit.