GoodSoundClub - Romy the Cat's Audio Site

Didital Things
Topic: PLLXO

Page 1 of 1 (9 items)

Posted by noviygera on 01-28-2010

Thanks for that collection of negative information on the DSP effects on music, Romy. I'm not a contributor to your site but you always put me in wierd situations with your unusual findings. For example, I have always used a DBX digital crossover in my system. It was convenient. I could never figure out why it sounded better if I drive the system harder (i mean putting a higher signal into the DBX). Another thing that was "interesting" is that no matter how I tweaked those crossover settings, the biggest effect on sound was made by changing the slopes of the filter (6db was the most natural sounding in my opinoin). I think, now I may have an idea why, based on the topics you saved in "crossover" section. So thanks for making chaos in my peaceful world.

And here why my situation is wierd:

I have a three way system. 12db/octave slopes are currently used, not because I want to but because my 15" vintage mids sound a bit muddy crossed at 900Hz with a 6db slope. So I settled on 12db.
I want to try what you recommend, using a simple line level 6db filters in front of my amps, just for laughs and compare it with a 6db digital filter.

How do I make these line level filters? Lets say I have crossover points of 180Hz and 900Hz. Is there a place to get that information? I have a Fluke 87 meter. I can do basic things and calculations too. Also, I am in Chicago. Are there smart people here who can help out?

Thanks,
Herman

Posted by KLegind on 01-29-2010

This is what you need to know - these are the equations you need for a passive line level filter:
http://www.t-linespeakers.org/tech/filters/passiveHLxo.html

You also need to obtain the input impedance of the power amps in order to calculate RC values.
There is a caveat: The combined input impedance of the power amps must be at least 10 times the output impedance of the preamp. Otherwise the load will kill the sound of your playback.

BTW - what is your opinion of the delay capabilities of the DBX crossover?

Sincerely
Kris

Posted by Romy the Cat on 01-29-2010

Good link, Kris. What is missing in the link is the RL filters. The RC Low-pass filters are fine as the capacitors are not in the band-pass mode. It is arguable what would be better – a subtractive shunting cap or a few miles of coil in the signal pass. The High-pass filters that Art Ludwig use- I do not like them and tend to use RL filters instead of RC filters. Look at the Milq’s 6Ch version and you will clearly see it.

Posted by KLegind on 01-29-2010

Romy the Cat wrote:
Good link, Kris. What is missing in the link is the RL filters. The RC Low-pass filters are fine as the capacitors are not in the band-pass mode. It is arguable what would be better – a subtractive shunting cap or a few miles of coil in the signal pass. The High-pass filters that Art Ludwig use- I do not like them and tend to use RL filters instead of RC filters. Look at the Milq’s 6Ch version and you will clearly see it.

Ouch, you touched a sore spot. I first came upon the idea of using line level RL filters on Audio Asylum. This is a bad f*cking place to learn anything (excuse my language). The RL idea was promoted as a alternative to active linestage filtering and as such a very useful concept. Now, here is where the skin of your face meets the road: This specific implementation was promoted by a follower of a certain "Tube-wrangler" personality that lives in the AA forum. This fella and his acolytes careen around the AA forum like some out of control dump truck leaving garbage everywhere. I have never seen such an amount of inane arguments about SET amps anywhere else (or shameless product placement either). Now would I really want to trust the advice of those unsavoury characters? I was sorely tempted to abandon the idea. Might give it a try if I get around to building that 2 stage 2A3 this spring.

Between pre and power amp it would need extra gain to overcome the dc resistance of the choke. I think I have a diagram of such a beast somewhere...

Kris

** Oooops, sorry - I thought you meant LC filtering! I'll have a look at the Milq circuit***

Posted by noviygera on 01-29-2010

Kris,

thanks. Here's what I have:

>>There is a caveat: The combined input impedance of the power amps must be at least 10 times the output impedance of the preamp. Otherwise the load will kill the sound of your playback.

I use a mixer as a pre-amp and it has two master outputs. (+6db 2V) is a switchable 6db gain for each output. I currently use the 0db setting.quoting specs from the manual:
"
Outputs Level/Minimum Load
MASTER (BAL) 0dBV/600Ω 1V (+6dB 2V)
MASTER (UNBAL) 0dBV/2.2kΩ 1V (+6dB 2V)
"

not sure what "minimum load" means.

and my three amps have the following input impedance:
Jeff Rowland has selectable: 100k, 20k, 600 ohms
Arcam Alpha 5 - "unknown" but can measure
Spectron 1KW - will need to measure

>>BTW - what is your opinion of the delay capabilities of the DBX crossover?
I have not extensively (avoided) used the delay functionality. I had delayed the subs. The function works very well but I am not sure if it screws up the sound out not. I think it's good for subs. I have not used it for mids or highs, I aligned those channels physically.

-Herman

Posted by noviygera on 01-30-2010

Confirming our concern about digital crossovers, by Harman international, the parent co. of DBX, today at 11am, and I will quote, "theoretically they compress the sound" and also I will quote, "it is a concern for live recording and not live sound". I'm sure it doesn't.
Just a friendly reaffirmation of the subject.

A solution I found that may solve the crossover problem by Marchand Electronics, easily. They have an configurable (slopes and frequencies) electronic crossover and also a hardwired passive line crossover. Also they have a tube version of the line crossover. Anyone have experience with their products? I'm motivated to try it.

Posted by KLegind on 01-30-2010

noviygera wrote:
Kris,

thanks. Here's what I have:

>>There is a caveat: The combined input impedance of the power amps must be at least 10 times the output impedance of the preamp. Otherwise the load will kill the sound of your playback.

I use a mixer as a pre-amp and it has two master outputs. (+6db 2V) is a switchable 6db gain for each output. I currently use the 0db setting.quoting specs from the manual:
"
Outputs Level/Minimum Load
MASTER (BAL) 0dBV/600Ω 1V (+6dB 2V)
MASTER (UNBAL) 0dBV/2.2kΩ 1V (+6dB 2V)
"

not sure what "minimum load" means.

and my three amps have the following input impedance:
Jeff Rowland has selectable: 100k, 20k, 600 ohms
Arcam Alpha 5 - "unknown" but can measure
Spectron 1KW - will need to measure

>>BTW - what is your opinion of the delay capabilities of the DBX crossover?
I have not extensively (avoided) used the delay functionality. I had delayed the subs. The function works very well but I am not sure if it screws up the sound out not. I think it's good for subs. I have not used it for mids or highs, I aligned those channels physically.

-Herman

Hi Herman,

Lets say you have three amps 100 K input imp. - that presents a load of ~33 K . The equation is:
R(amps) = 1/(1/amp1)+(1/amp2)+(1/amp N)

So if we have JR=100k and Arcam=47k (might be lower) and Spectron=47k (pure guess work), R_total is 19k
This is fine if you are using the balanced output, but its a stretch with the unbalanced out. As always; listen first.

Now if the arcam or spectron unit is 10k the sound will most likely suffer.

Best
Kris

Posted by KLegind on 02-01-2010
fiogf49gjkf0d I had a look at the pic of your speaker just now - may I ask about the reasoning that went in to choosing a diffraction type horn? Also, your midrange looks like an open baffle type. What kind of back wave/diffraction management do you use? Kris

Posted by noviygera on 02-01-2010

KLegind wrote:
I had a look at the pic of your speaker just now - may I ask about the reasoning that went in to choosing a diffraction type horn?

Also, your midrange looks like an open baffle type. What kind of back wave/diffraction management do you use?

Kris

Kris,
First, let me explain where I am coming from with my system goals. My system serves TWO purposes: 1.music playback and production monitoring; 2.music playback for parties. I host music events at my house, with different DJ's, participating and as a result my system need to have more output capabilities. However, my priority has always been good sound quality.

>>>the reasoning that went into choosing a diffraction type horn

I have not heard many horn loaded systems because I don't know of many people with good horn based sound systems. I wish I did. The two systems that I encountered with good impressions are: Avantgarde Trio; fully horn loaded systems by Funktion One. Both systems, the way I want them, are way out of my budget so I set a goal to make a system that sounds close enough to be satisfying. One step at a time.

Step one:
I was able to get a pair of Funktion One mid/high horns, the ones you saw in the picture. This is a diffraction horn, as you call it, with a phase plug and a 5" cone driver, that covers 530Hz to 15Khz, officially. This was step one for me. I have to say I am happy with the sound. To summarize in two words I would say: dynamic, natural. All I can compare it with is the Edgar 350Hz horns with Altec 288 that I had a chance to hear over this weekend (briefly). I would say that the Fun.One is superior in everything but clarity in the higher end of the extreme freq. but this is not an extensive audition to make any certain conclusion.

Honestly, the only reasoning that went behind using this horn is the positive sensory experience of a full horn loaded Funktion-One system I listened to.
I wish I had a chance to hear more properly done horn loaded systems.

>>>Also, your midrange looks like an open baffle type. What kind of back wave/diffraction management do you use?

I don't. This is a temporary solution to fill the void 200Hz to 1000Hz. If you have better ideas please, please let me know. I am currently trying come up with a good solution for this range.

Also, Kris, thank you for providing information on the amplifier input impedance.
-Herman

Page 1 of 1 (9 items)