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High Efficiency Speaker Asylum Need speakers that can rock with just one watt? You found da place. |
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High Efficiency Speaker Asylum Need speakers that can rock with just one watt? You found da place. |
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In Reply to: RE: Altec 9844As and N-800-F (1,600 Hz +6dB Peak) posted by VFR800A on January 17, 2011 at 18:10:20:
Hi Jim
Well, if I were starting over, I start with a copy of ARTA, it is an inexpensive software that is very powerful, a screaming deal as they say (I think so anyway). I use it and a TEF machine for most loudspeaker related audio measurements.
That plus a measurement microphone like the one from Parts express or other and few other small bits and you’re on your way.
In the case of your speaker, one can easily derive a filter to get rid of the offending bump BUT unlike the simple filter one might design from a text book, the speaker as a load is often nothing like a resistor.
As a result, an impedance curve AND response curve are needed as the raw data for a filter design program. Thankfully if you have the measurement program for a microphone, one can normally use it for measuring impedance too.
If you can take a response and impedance measurement for me, I will suggest some values to try if you wish. As a general rule, it takes three parts (R,L and C) to dip a peak, more if you’re dealing with a complex impedance, fewer if you can make parts serve multiple purposes.
In the mean time without measurement software, you can do it the old fashioned way taking measurements every 10 or 100Hz or so.
If you have an digital AC voltmeter, you can try the impedance part with that.
The potential problem is that most ac volt meters do not have flat frequency response so that 10Vrms at 60Hz reads correctly but at say 16KHz it’s way off. You can account for that by presenting it with a fixed voltage (like form a power amp) and observing the indicated Voltage to make a correction table (pain in the butt).
Meters used in audio HAVE TO have flat frequency response if you want valid readings.
The solution here is to buy a new meter that is known to work all across the band OR (and the one I suggest) buy a state of the art in the 80-90’s meter.
I have purchased a couple of these (HP-400F) from Flea bay and love them (they made a number of variations as well as an earlier / larger version).
These are an analogue meter that can even be used with music (eyeballing the average voltage) with a 100KHz bandwidth and I think a 10X peak to average voltage ratio (meaning is it correct dynamically within a signal spanning 100:1 power level variation or 20dB peak to average ratio).
Anyway, if you have a VRF800, i bet you will like getting into the technical part of how speakers work (I am slowly working on a 9 yr old Ducati m900 s4 built from a crashed bike & parts). You will find like motorcycle market, there is some folk lore which falls apart once your switching from (using an old analogue) adjusting your carbs by listening to the exhaust or using vacuum gages on each cylinder and if performance is the measure of success, you will like it this way.
Best yet, with speakers being by far the weakest link in the chain, when you make an improvement that shows up well in a measurement, it nearly always sounds better too and not just to you too but globally.
With some hifi tweeks your not fundamentally changing anything and so folks need to make these things visibly obvious to point out what was done for them to be audible.
Best,
Tom Danley
Danley Sound Labs
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Follow Ups
- RE: Altec 9844As and N-800-F (1,600 Hz +6dB Peak) - tomservo 07:34:55 01/18/11 (1)
- RE: Altec 9844As and N-800-F (1,600 Hz +6dB Peak) - VFR800A 18:32:18 01/19/11 (0)
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