how do i know if my hf on my acoustat 2+2 are the same level? - diyAudio
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Old 22nd September 2006, 09:27 PM   #1
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Default how do i know if my hf on my acoustat 2+2 are the same level?

I have this adjustment with a resistance that I slide a metal ring with a wire attached to it,I have a little gauge that tells me approx. where there high frequencies it is leveled but seems not to play exactly the same on each side but they are on the same spot.any type of mesument I can do with a multimetre?and is ther a modification I can do to have a sort of exterieor adjustment like other 2+2?
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Old 22nd September 2006, 11:19 PM   #2
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How about just setting them so they sound the same?

I_F
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Old 23rd September 2006, 01:22 AM   #3
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the only problem with that is I have to undo the back every time and it's quite long so if I can have a reading of some sort,it would help getting the right sound faster.
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Old 23rd September 2006, 05:50 AM   #4
Calvin is offline Calvin  Germany
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Hi,

most important is that both chanels sound the same and in the same volume level. Because of building tolerances it can be possible that different polarizing Voltages are needed. Normally this voltage is set to an operating point where even considerable change of its level only results in a very small change in output volume level of the speaker itself.
If You want to measure the voltage at the output of the HV-generator Youīll need a HV-voltage probe. First a normal multimeter isnīt able to withstand several kV of votage and secondly is the inner resistance of the multimeter too low. The HV-generator canīt supply for such low loads and its output voltage drops. So You need something with an high enough inner resistance and voltage capability. Thatīs what an HV-probe supplies for. You might buy one for Your multimeter, or You may build one. I made mine from 100 series connected 10Megohm resistances, giving an overall resistance of 1Gohm (standard metal film).
When connected to the HV on one side and ground on the other You can measure the voltage over the last resistor (going to gnd). Normally Multimeters have an inner resistance of 10MegOhm. So the last resistor and the multimeter form a combined resistor of 5MegOhms. After the voltage-divider-rule the voltage over this resistance is Umes= UinputHV *(Rmes/R total). With Rmes = 5MegOhm and Rtotal=995Meg (without the multimeter Rtotal=1000MegOhm). From this You can calculate the unknown UinHV of the HV-Generator. UinHV=Umes(Rtotal/Rmes). In my case a 1V reading on the multimeter woud give 995V UinHV of the HV generator.
Thats not perfect and leaves room for quite big measuring failures, but at least You can have two identical readings and a rough idea whats going on.

jauu
Calvin
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Old 23rd September 2006, 10:06 PM   #5
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I think the simplest way to check is to use an SPL meter, run a noise track or FM interstation noise place the meter exactly at the same distance, like 1 foot centered on the middle panel exactly and see what the meter says.

Place the tweeter levels at minimum first (or disconnect)- this will give you base reference to see if the panels are both at the same basic levels.

If not, swap the interfaces - if the level imbalance shifts, probably you have a bad HV string in the multiplier.

Btw, that does not look like a 121 MkII interface...?

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Old 25th September 2006, 01:49 AM   #6
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I like the idea of the SPL meter. I used my measurement software to match both of my ESL to a fraction of a dB. No matter how carefully you build your stators and panels, there will be slight differences. If you design your HV supply to be adjustable, then you can tune out the differences. My panels were only slightly different (fraction of a dB), but my soundstage got much better when tuned.


Sheldon
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Old 25th September 2006, 03:46 AM   #7
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a db meter sounds good,I will take a closer picture of the interface,but it.s a medallion,I 'll write the model tommorrow.
after 3 days of charging It sounds already better...
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Old 28th September 2006, 12:52 AM   #8
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here is a closer look
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Old 28th September 2006, 12:59 AM   #9
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other pics of the inside...just couldn't get the focus right [IMG]Click the image to open in full size.[/IMG]

picture2 picture3 picture3

can those 2 red wires be solder to a lpad or something like that ?
on picture 3.
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Old 30th September 2006, 02:59 PM   #10
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Ok, first thing - no matter what.
Get RID of that blue electrolytic cap that is in parallel to the yellow and silver (polystyrene) cap, I think in pic 2, that is in the audio path!! Replace with polypropylene of the same or similar value.

BIG difference!

Now, I can not see if you have two or one audio step up (drive) transformer in the the interface box or not??

The slider on the HF level control can be replaced with a LARGE like 20 watt or 50 watt rheostat, as is in the 121 MkII interface... but it is not necessary really. Or you could parallel a slightly smaller rheostat with the existing resistor, of course it would be a higher resistance unit... or add taps and put a switch in...

how about a wide shot of the innards?

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