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Loudspeaker Management Systems

gene_stl

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The granddaddy of all these systems and maybe the most wonderful piece of stereo componentry ever made is the Pioneer Series 20/Elite D-23 analog four way electronic crossover network.



There were other similar ones from Sony and others. But most of them required modules to change the crossover frequencies.
I have used one of these since late 1976 along with various gadgets to confirm the settings (RTAs)
 

Scrappy

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Ha there’s only one board in LM’s, there are even transformers in the PCB!

There are known issues with ‘26 output stage, but never with “analog” linear non-switching amps..
 

Scrappy

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I have not seen those. Interesting that they're quoting some guys from Brit Row, which is owned by Clair Global now.
Sure hope that they stay on the Queen’s island...
The granddaddy of all these systems and maybe the most wonderful piece of stereo componentry ever made is the Pioneer Series 20/Elite D-23 analog four way electronic crossover network.



There were other similar ones from Sony and others. But most of them required modules to change the crossover frequencies.
I have used one of these since late 1976 along with various gadgets to confirm the settings (RTAs)
Whoa those stacked rotary switches ! A fixed-filter version of that for certain touring PA cabinets is the origin of “frame” and “module” nomenclature.
 

Dion_Sinewave

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Ha there’s only one board in LM’s, there are even transformers in the PCB!

There are known issues with ‘26 output stage, but never with “analog” linear non-switching amps..
I did think it was strange that my 2004 Contours sound perfect, and a 2018 LM26 had awful hiss.
regrding your second sentence: I can see/ hear the hiss with *any* component downstream of the LM26 from its XLR outs, in 2 way or 3 way but not in 1 way (just stereo out)
 

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Scrappy

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in 2 way or 3 way but not in 1 way (just stereo out)
That’s very very interesting. If I recall, LM26 has 3 pair of output devices, so utilizing 2 out (on 1,2 and 4,5) would only double up the first out chip. As I’ve posted, I test these fu-, devices every day on purpose-designed rigs, never see noise.
 

Dion_Sinewave

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That’s very very interesting. If I recall, LM26 has 3 pair of output devices, so utilizing 2 out (on 1,2 and 4,5) would only double up the first out chip. As I’ve posted, I test these fu-, devices every day on purpose-designed rigs, never see noise.
So what do you think the problem was for me? Amplifier gain? I’m truly at a loss to explain it.
 

Dion_Sinewave

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That’s very very interesting. If I recall, LM26 has 3 pair of output devices, so utilizing 2 out (on 1,2 and 4,5) would only double up the first out chip. As I’ve posted, I test these fu-, devices every day on purpose-designed rigs, never see noise.
I certainly know how to operate them, but you clearly know much more about their design that I do
 

dualazmak

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I wonder what do you mean by "Loudspeaker Management Systems"?! In our private home listening room, or in professional recording studio?

My latest setup of home "Loudspeaker Management System (IMHO)" can be found here. It is multichannel multi-driver multi-way multi-amplifier fully active stereo audio system in my home listening room with 0.1 msec precision measured/adjusted time alignments between all of the SP drivers...
 
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G|force

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Shameless advert: I have a BSS BLU160 with 1 AES in card and 2 AES out cards for sale if anyone here is interested. :cool:
 

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SeshatCZ

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There were other similar ones from Sony and others. But most of them required modules to change the crossover frequencies.
I have used one of these since late 1976 along with various gadgets to confirm the settings (RTAs)
Hi gene_stl, what gadgets have you used? I am now in a similar situation with my newly acquired vintage crossover Sony ta-d88b.

I have contemplated to use some gear from professional ones Loudspeaker Management Systems to do some measurements for Room treatment, which I would use manually for setting The Sony in a more sophisticated manner.

I have thought of Dbx Driverrack 260, or Ashly Protea 3×6. Or maybe some from consumer ones like MiniDSP Flex. I would like something with PC connectivity, and with a rather simple graphic interface. I can use this digital gear in some other way then, separately from this setup.

Is it a technically meaningful way from Your stand point, with Your own personal experience with active analog crossover during tens of years?

Thank You in advance for Your reply,
Pavel

P.S.: I am inclined to use an analog only gear as much as possible in this set-up. I need to play several of my vintage FM tuners, the digital one gear like CD or streaming as an add-on only...
 

gene_stl

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When I first built my speakers I knew two people who had supposedly calibrated microphones and audio FR analyzers. One was a General Radio which I borrowed from a physicist friend who was a Professor at a local university. The Analyzer belonged to the U. Another one was more intended for professional use but I don't remember what brand it was. It might have been something on the order of a Sound Craftsmen. I also can't remember who it was that loaned it to me but I remember using it. This was from the time I built the speakers in the first house until a couple of years in the second house (1977-83)

Then I was able to purchase a gadget from Technics that had a Warble oscillator and a supposedly flat microphone and a VU meter. It warbled in narrow bands and you set your levels accordingly. (Mid 80s)

I had to buy a new mic for the above because a battery leaked and ruined the original.

Then about twenty years ago I got my hands on a couple of Audio Control RT-3051 rtas. These are much loved by the car audio guys and were used in their loudness competitions.

Sooner or later I will start using REW. I have a local friend who bought a calibrated microphone which he will loan me.

I was very interested in the Sony when it came out which was distinctly later than the Pioneer D-23. It had some interesting filter characteristics available (Chebyschev rather than just Butterworth) But you had to get modules to change everything. The Pioneer you just turn a knob.

In spite of that convenience once you get it zeroed into the room it is in. (It has been in three rooms. Plus my friend had one) there is a tendency to leave it mostly alone. Sometimes one uses it as a tone control on a weirdly equalized source. But mostly after I get it set and listen to a few of my favorite albums it can go for very long times without the knobs being disturbed.

An interesting and very little known fact about the Pioneer. When set to 12 db per octave crossover slope the crossover point is at the minus 6db points as laid out in Linkwitz-Riley criterion for stable radiation pattern. However the D-23 had to have been designed very much BEFORE Linkwitz published his seminal paper in about 1976. Could it be that Pioneer Electronic Engineers figured the same thing out and kept it as a trade secret?? I don't know and Sigfried Linkwitz has passed away not too long ago. I somehow ran across his paper when it was published and always had a Xerox copy of it in my audio stuff. I gave it away often enough that I finally wrote on one copy "Gene's Copy --- No Loan! and drew a skull and crossbones next to that caption)

A local symphony musician friend of mine uses the dbx Drive Rack but he did not buy the microphone with it. We have used my audio control to try and set up his system. I am not sure he would buy that system again. I have looked at the drive rack and also the Behringer and a couple of other pro systems and mostly concluded that I want to stay with what I have. I do have a stack of four identical pro crossovers. I have never yet used them.

There are various other crossovers available. If I needed to replace the Pioneer I think I would mainly look at this guy's stuff:
 
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fpitas

fpitas

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I wonder what do you mean by "Loudspeaker Management Systems"?! In our private home listening room, or in professional recording studio?

My latest setup of home "Loudspeaker Management System (IMHO)" can be found here. It is multichannel multi-driver multi-way multi-amplifier fully active stereo audio system in my home listening room with 0.1 msec precision measured/adjusted time alignments between all of the SP drivers...
What I originally meant was the typical 1U rack mount units intended for Pro audio. But the discussion has widened, and as the OP I'm perfectly happy with that. Thanks, and thanks to everybody else chiming in.
 

kipman725

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I have performed some tests on a Symetrix Radius AEC this is a sophistcated free form DSP with FIR capability upto 1024 tap filters. The fans on these units are tempreature controled blower fans so while not super annoying the cooling system would have to be modified for home use with the unit in the same room as the user. This unit has the specification THD + Noise < -94 dB, unweighted; 1 kHz @ +22 dBu with 0 dB gain, I'm presuming this is a loopthrough measurment (analog input directly connected to output). The unit also has 64x64 Dante digital audio IO but I will need to spend some time working out how to use that. The unit is specified to work with levels up to 23/24dBu (in/out).

For these tests I am using my TASCAM US-2x2HR interface which achives SINAD (20-20kHz) 98.5dB in loopback at 4V output (note not much margin over these results better measurment equipment could show improved numbers).

4V input loopthrough line input 1 to output 1:
1662238142439.png

So we are hitting the spec here, SINAD is 4dB degraded compared to if I just connected the input of my interface to the output.


4V input loopthrough line AEC input 1 to output 5:
1662238277930.png

The AEC inputs have additional processing that can be used for acoustic echo cancelation, it can also be turned off to use them as normal inputs. The performance is the same as the line inputs.

Loop through frequency response and delay:
1662238481205.png

I'm not sure what kind of mad antialias filter they are using or if I'm seeing some strange alias effects but the attenuation at 24kHz is lower than it should be (kind of imposible to read due to the oscilations but around -30 to -60dB). LF corner is around 5Hz.

1662239238810.png

I think this is specified as 0.88 mS by the datasheet (sum input and output delays).


Inline attenuator on my soundcard input (~-14dB) 0dBfs internal signal generator (clip indicator on output red):
1662238866290.png

starting to clip here but not too bad.

Internal generator -2db (inline attenuator):
1662238960417.png

not clipping anymore.

Internal generator at 14dBu (no inline attenuator):
1662239068453.png

SINAD Is +2dB improved over using analog input.

Performance looks simlar to a drive rack PA2: https://www.audiosciencereview.com/...riverack-pa2-speaker-management-system.14134/ in my view pretty decent with the performance reduction compared to gear that is normaly tested on ASR partly due to the capability to handle 24/23dBu signals (10dB more than typical for Hi-Fi gear). At home I use inline attenuators between my DSP and amplifier matching the amplifiers sensitivity to full scale output to reduce the output noise of the whole system.
 
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kipman725

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I found some data on my hard disk of some rough and ready tests on a Biamp Nexia unit. This unit has an output full scale option so you can adjust the full scale in several steps. In use I found the nexia units quite noisy (output noise - the fans are quite quiet). I think these measurments are looking into this noise issue.

Frequency response:
1662240912100.png



18dBu input, 1kHz, input gain = 0, output FS = 24dBu:
1662240925367.png



18dBu input, 1kHz, input gain = 0, output FS = 18dBu:
1662240940053.png



18dBu input, 1kHz, input gain = 0, output FS = 12dBu:
1662240946837.png


18dBu input, 1kHz, input gain = 0, output FS = 6dBu
1662240970475.png


so with noise in the default setting only at -73.4dBu you can see why I was having noise issues!
 
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