Multi-Channel, Multi-Amplifier Audio System Using Software Crossover and Multichannel-DAC

[Keith_W]

@dualazmak why did you decide to do volume control in JRiver instead of EKIO or OKTO Dac? My Motu 828es has 32-bit processing (the same as the OKTO I believe) so I am currently doing volume control for my multi-amp setup at that point.

I have a similar setup to Dualazmak, and I too implement volume control with JRiver. There are a few reasons I do this:

- Remote control. All apps that control JRiver are able to control JRiver's remote control. No need to reach for a separate physical volume control (for DAC) or another app or web interface (to use the VC on the convolver).
- ISO226. JRiver has this. Nothing else does, except Acourate Convolver and (maybe?) Hang Loose Convolver.

 

[dualazmak]

i feel like this is a good way to re-use multichannel HT amps

if you have a 5-6-7 channel amp not being used then why not use them channels?

in theory if you have a 6 channel and a heap of wire and speakers you can tri-wire and some way to run the crossovers then you could have some experimentation to do

Thank you for your attention and interest on my DSP-based multichannel multi-SP-driver multi-amplifier fully active audio project.

I understand your point. In my case, however, I have been sticking to "right-person-in-right-place" approach/policy throughout my amplifier selection exploration/journey. Just for example, we do not need big powerful amplifier(s) to directly drive highly efficient tweeters and supertweeters, but we do need small but transparent high S/N low THD excellent amps.

Just for your (our) reference, I once intensively tested/evaluated YAMAHA MX-A5200 (Class-AB) 11-Ch AV amplifier at the beginning of my amplifier selection, and that was actually the very beginning and motivations for my rather long and intensive amplifier exploration journey at least in my HiFi multichannel audio project. You would please find here the (intermediate) summary of my amplifier exploration. I hope that you would very carefully read through my posts on my step-by-step amplifier selection exploration. You can find here and here the HyperLink Index of this long/intensive thread.

My post here would be also your interest and reference;
- Even Greg Timbers uses "reasonable and budget" Pioneer Elite A-20 for compression drivers (super tweeters) in his extraordinary expensive multichannel stereo system with JBL Everest DD67000 which he himself designed and developed: #435

 

[adLuke]

Just for my curiosity, @dualazmak have you ever listened to the Yamaha RX-Z9 AV amplifier? Old SOTA Yamaha AV Receiver/Amplifier.
I think it came out 20 Years ago.

 

[dualazmak]

Just for my curiosity, @dualazmak have you ever listened to the Yamaha RX-Z9 AV amplifier? Old SOTA Yamaha AV Receiver/Amplifier.
I think it came out 20 Years ago.

I am sorry but I never listened to it...

 

[gac800]

Hi @dualazmak . Thanks for your help! This is how I have set up my current system. The VU meters on the reel-to-reel are linked to the EKIO output so that they measure the L & R of the entire system. I am still looking for a suitable Subwoofer and Supertweeter and Amps to complete the system. Please let me know if you can see any way that I can improve the current set up. My next step is to attenuate the amps to that I can have the volume control on the Motu 828es set to -20 to 0 dB instead of the current -30 to -15dB.

 

[dualazmak]

View attachment 335641
Hi @dualazmak . Thanks for your help! This is how I have set up my current system. The VU meters on the reel-to-reel are linked to the EKIO output so that they measure the L & R of the entire system. I am still looking for a suitable Subwoofer and Supertweeter and Amps to complete the system. Please let me know if you can see any way that I can improve the current set up. My next step is to attenuate the amps to that I can have the volume control on the Motu 828es set to -20 to 0 dB instead of the current -30 to -15dB.

Thank you so much for sharing your on-going multichannel audio project by using similar diagram-style like mine! Your total signal path can be so nicely illustrated and it is a invaluable reference and actual example case not only for myself but also for many people periodically visiting this thread!

Protection capacitors for midrange-squawkers, tweeters, super-tweeters
If you are currently do not using protection capacitors for your treasure midrange-squawkers and tweeters (also for your planned super-tweeters), I would like to highly recommend to use them.

As I chimed again recently in my post here #861, even with all the other safety measures, you (we) need to have protection capacitors for our treasure midrange-drivers (I use 68 microF film caps), tweeters (I use 10 microF film caps) and super-tweeters (I use 10 microF film caps); ref. here and here. Of course, I carefully measured the SPL curves before and after the protection caps confirming their transparences in audible sound (ref. here and here).

These protection capacitors actually protected/rescued my SP drivers several times during my multichannel exploration when I stupidly did mis-routing the signals, and even when I mis-connected the SP cables by careless mistake.


Selection of amplifier for super-tweeters
I assume you well understand that we do not need powerful amplifier to drive super-tweeters, but we need small-power high S/N and very-low THDN amplifier in very high Fq zone. In this context, my post here #435 would be of your reference;
- Even Greg Timbers uses "reasonable and budget" Pioneer Elite A-20 for compression drivers (super tweeters) in his extraordinary expensive multichannel stereo system with JBL Everest DD67000 which he himself designed and developed: #435

I am much curious and looking forward to hearing your coming super-tweeter and its amplifier selections.


Group delay settings?
Your diagram indicates that you set 15 ms group delay in LF (woofers) against ULF (subwoofers), also 15 ms group delay in HF (tweeters), but no delay (0 ms) in MR (midrange drivers); why no delay in MR?? And, how could you measure/decide/confirm the group delay values?
Have you ever tested/tried my "time-shifted multiple tone burst method (ref. here)" for assessment and tuning of time alignment between the SP drivers?

 

[gac800]

Thanks for the feedback @dualazmak. I recently split this system from the 3-way system in my living room. It is still a work in progress, I am going to build a more permanent support for the horns to replace the temporary setup I have now.

Protection capacitors

This is something that I am very interested in pursuing. When I restart the Motu828es, there is quite a loud pop, so I believe this would help to protect the HF drivers.

Selection of amplifiers for supertweeters

I currently use a Fostex T90A in my living room system. It is crossed passively to my Fostex 206nv backloaded horns and I am quite happy with its performance. I am strongly considering another Fostex supertweeter but also a ribbon supertweeter so I will review your research into a suitable amplifier.

Group Delay Settings

The group delay settings are based on the fact that the MR horn places the MR driver quite a bit farther back than the LF and HF drivers (see attached picture below). I am sure that this setting is not precise, and I will be exploring the time-shifting multiple tone burst method that you have linked to In order to get a more accurate time-alignment.

Amp Attenuation/Channel Volume Control

As I am using quite sensitive compression drivers, I need a way to attenuate the line level signal coming into the amplifiers so that the volume adjustments on my Motu 828es are between -20 an 0 dB. Currently they are between -30 and -15 dB and this is not ideal.

I am using the volume control on a Schiit Sys passive pre-amp to adjust the line level signal going to the MR amplifier.

Do you have any suggestions for line-level attenuation? I can also control the volume on the individual channels in EKIO or the Motu 828es, but I am not sure what the best practice would be.

 

[dualazmak]

Hello @gac800,

Thank you for the photo of your ongoing multichannel project; it looks unique and quite interesting.

Protection capacitors
This is something that I am very interested in pursuing. When I restart the Motu828es, there is quite a loud pop, so I believe this would help to protect the HF drivers.

Yes, highly recommended. You need those protection caps as early as possible before some mistake and/or accident would completely destroy your treasure SP drivers!

Furthermore, you would be better to standardize your routine "startup/ignition sequences" and "shutdown sequences" like I do my sequences everyday (ref. here).

Group Delay Settings

The group delay settings are based on the fact that the MR horn places the MR driver quite a bit farther back than the LF and HF drivers (see attached picture below). I am sure that this setting is not precise, and I will be exploring the time-shifting multiple tone burst method that you have linked to In order to get a more accurate time-alignment.

Now, I fully understood you are using very much efficient horn drivers, and in your present setup the longest throat midrange driver (placed in most rear position) would be the time zero reference for time alignments of other drivers. This means that you would need new time-alignment tuning again after your coming introduction of sub-woofer(s), right?

As for my "time-shifting multiple tone burst method (ref. here)", I will be more than happy to share with you the test tones I prepared for these measurement and tuning;

Spoiler

- Precision measurement and adjustment of time alignment for speaker (SP) units: Part-1_ Precision pulse wave matching method: #493
- Precision measurement and adjustment of time alignment for speaker (SP) units: Part-2_ Energy peak matching method: #494
- Precision measurement and adjustment of time alignment for speaker (SP) units: Part-3_ Precision single sine wave matching method in 0.1 msec accuracy: #504, #507
- Measurement of transient characteristics of Yamaha 30 cm woofer JA-3058 in sealed cabinet and Yamaha active sub-woofer YST-SW1000: #495, #497, #503, #507
- Identification of sound reflecting plane/wall by strong excitation of SP unit and room acoustics: #498

In case if you would be interested in the test tone files/tracks, please simply PM me writing your wish.

Do you have any suggestions for line-level attenuation? I can also control the volume on the individual channels in EKIO or the Motu 828es, but I am not sure what the best practice would be.

Before starting this multichannel project thread, in the beginning of 2020, I actually had very intensive discussion with one of the highly respected audio engineers in Japan regarding pros and cons of various line-level attenuation methods.

Spoiler

If you would be interested, you can read Mr. BOWS's very nice and thorough comments (almost an textbook on the issue!) started here and thereafter; I hope your web browser would properly transrate Mr. BOWS's comments on that Japanese thread into English.
https://bbs.kakaku.com/bbs/-/SortID=23181110/#23182184
(You would please read through Mr. BOWS's nice comments thereafter by ignoring other people's, include me, frequent intrusions.)

My (our) compromisable (almost) best conclusion after such discussions was/is "to use HiFi grade excellent preamplifier or integrated amplifier, both capable of XLR balanced input" based on the "right-person-in-right-place" policy and practice, in case if you (we) would need attenuation in analog domain after the DAC(s).

I would like to suggest you, therefore, to test and evaluate small but high-quality HiFi preamplifier(s) of XLR balanced input capability for your "safe and flexible" line level attenuation.

Even though SOULNOTE A-0 would be a very nice candidate as preamplifier/integrated-amplifier for tweeters and supertweeters (and even for woofers as preamp), I do not know its availability in Canada. I assume and hope you may find similar spec amps in Canada and in the USA.

 

[gac800]

Yes, highly recommended. You need those protection caps as early as possible before some mistake and/or accident would completely destroy your treasure SP drivers!

Yes, it is a priority for me. I read that you were using the Jantzen capacitors, but I could not find any information on your crossover points. How did you determine which capacitor/crossover point to use?

Now, I fully understood you are using very much efficient horn drivers, and in your present setup the longest throat midrange driver (placed in most rear position) would be the time zero reference for time alignments of other drivers. This means that you would need new time-alignment tuning again after your coming introduction of sub-woofer(s), right?

As for my "time-shifting multiple tone burst method (ref. here)", I will be more than happy to share with you the test tones I prepared for these measurement and tuning;

My plan is do build a shelf for the compression drivers so that the woofer, Midrange, Tweeter, and super tweeter are in a better physical alignment. I will then do any additional timing adjustments in EKIO. This will include adding the subwoofer. This will most likely be a folded horn, so the subwoofer would end up being time zero in EKIO. I will be messaging you for the tone bursts.

Before starting this multichannel project thread, in the beginning of 2020, I actually had very intensive discussion with one of the highly respected audio engineers in Japan regarding pros and cons of various line-level attenuation methods.

Looking forward to reading the translation. I am currently using a passive pre-amp Schiit Sys for this purpose before my midrange amp. So I am happy to see that I am on the right track.

Even though SOULNOTE A-0 would be a very nice candidate as preamplifier/integrated-amplifier for tweeters and supertweeters (and even for woofers as preamp), I do not know its availability in Canada. I assume and hope you may find similar spec amps in Canada and in the USA.

I often purchase my audio equipment from the USA so that should not be a problem. Thank you for the recommendation.

 

[dualazmak]

Yes, it is a priority for me. I read that you were using the Jantzen capacitors, but I could not find any information on your crossover points. How did you determine which capacitor/crossover point to use?

The purposes of the "protection capacitors" are not for crossover, but for protection of the SP drivers from accidental/unintentional intrusion of very-low Fq (or even DC) signals which highly possibly would damage/destroy the SP drivers.

Consequently, the capacitance of the "protection capacitors" should be selected that it would be almost transparent (almost no SPL suppression) in the Fq zone for which the specific SP driver would be intended to sing configured by DSP.

I selected, therefore:
68 microF Jantzen Standard Z-Cap 400 VCD to protect my 8 Ohm Beryllium midrange-driver covering 500 Hz - 6 kHz (by EKIO XO),
10 microF Jantzen Standard Z-Cap 400 VCD to protect my 8 Ohm Beryllium tweeter covering 6 kHz - ca. 14 kHz (by EKIO XO),
10 microF Jantzen Standard Z-Cap 400 VCD to protect my 8 Ohm metal horn super-tweeter covering ca. 8.8 kHz - 25 kHz (by EKIO XO + 3.0 microF cap)

One capacitor placed in series in the SP high-level signal reacts as -6 dB/Oct high-path (low-cut) filter, and incase the nominal impedance of the SP driver is R Ohm, and the capacitance of the protection capacitor is C microF, the cut-off Fq point is Fc Hz, then;

C=159,000/(R*Fc),
or
Fc=159,000/(C*R)

So, in my case,
with 68 microF Protection Cap for 8 Ohm midrange-driver --> Fc=159,000/(68*8) = 292 Hz
with 10 microF Protection Cap for 8 Ohm tweeter and super-tweeter --> Fc=159,000/(10*8) = 1,989 Hz = 1.99 kHz

And, of course I measured and confirmed the transparency of the protection capacitors by measuring the SP-high-level SPL curve (with DSP XO applied) before and after the protection capacitors, as shared in my posts #402 and #485.

will be messaging you for the tone bursts.

You are quite welcome! I have responded to your PM message with the various specific information.

 

[dualazmak]

Hello again @gac800,

Just for your additional reference and interests, I have intentionally inserted parallel 22 Ohm resistor in SP high-level line for midrange-drivers, tweeters and super-tweeters; this is simply always giving a little bit of extra workload to the each of the dedicated amplifiers.

You would please refer to my post #248 and #251 for the detailed background story and rationales on these parallel 22 Ohm resistors.
Our discussions in this regard shared #99(remote thread), #100(remote thread), #101(remote thread) would be also of your reference.


Furthermore, since you are using highly efficient and sensitive horn drivers, I assume my below two posts would be worthwhile for your attention;
- Elimination of magnetic susceptible metals in SP signal handling: #250, #013(remote thread)
Relating to this issue, you would be also reminded that the audible/measurable distortion was caused by iron (steel) plates at the SP binding posts of old-version of BUCKEYE 3 Channel Purifi Amp, and the cause (=steel plate on SP binding posts) were found/identified, then BUCKEYE replaced the parts with blass plates by a kind of recall announcement; please refer to the specific thread.

 

[gac800]

@dualazmak Thanks for the information on the protection caps and the resistor. I look forward to reading it, and I will keep update the thread when I have made the suitable changes to my system.

 

[gac800]

You would please refer to my post #248 and #251 for the detailed background story and rationales on these parallel 22 Ohm resistors.

@dualazmak do you recommend 20-22 Ohm resistors as a good option for most multi-way systems? I see that you are using the same resistors for all of your speaker drivers.

 

[dualazmak]

@dualazmak do you recommend 20-22 Ohm resistors as a good option for most multi-way systems? I see that you are using the same resistors for all of your speaker drivers.

You need it or do not need it; the feasibility would depend on system to system, and what amplifier what SP driver you would use (i.e. how sensitive they are), as well as how your ears and brain would be sensitive for the faint difference of sound quality with and without the parallel 20-22 Ohm resistor.

I recommend "Low-Inductive Wire-Wound non-polarity 22 Ohm audio-grade 10 Watt resistor(s)", like the one I use (ref. here), for your initial tests.

You may understand that usually our SP driver's nominal impedance is 4 Ohm to 8 Ohm, and 20-22 Ohm tuning parallel resistor would give mild extra workload to amplifier (i.e. extra electricity consumption, slightly increase your electricity bill, though!); I feel, therefore, 20-22 Ohm would be generally OK for slightly raising up the amplifier from the zero-cross level.

Yes, you need to perform very intensive listening tests for the preferable effect of parallel resistor or not with each of your SP drivers and dedicated amplifiers in midranges, tweeters and super-tweeters.

 

[dualazmak]

Semi-annual intensive cleaning of all the metal-to-metal connectors/contacts, and complete renewal of all the tin-electroplated copper terminals with heat-shrink insulators

Abbreviations in this post;
- L&R sub-woofers (SWs),
- L&R woofers (WOs),
- L&R Beryllium-midrange-squawkers (MD-SQs),
(I know nowadays very few people use the word "squawkers", but please let me continue using "SQs" for midrange "MD-SQ" drivers.)
- L&R Beryllium-tweeters (TWs),
- L&R metal-horn-super-tweeters (STs),
Each of these is driven directly (with no LCR-network nor attenuator) by dedicated HiFi amplifier; SW has powerful built-in amplifier, and I use four stereo HiFi integrated amplifiers for others.

Edit on January 31, 2024: please also refer to my post here #906
- Renewal of SP cabling boards beside SP systems: #906

During the end-of-the-year week in December 2023, I did my semi-annual intensive cleaning of all the metal-to-metal connectors/contacts (ref. here #671).

You would please refer to my post here #774 for the details of my latest (as of August 3, 2023) setup of my DSP-based multichannel multi-SP-driver multi-amplifier fully active audio setup.

Furthermore, this time I also completely renewed all the tin-electroplated copper terminals with heat-shrink insulators.

EDIT:
Just for your info, these are really cheap, but very much reliable and robust; non-magnet tin-electroplating pure copper (industry use) crimp terminals (about USD 6.3 = JPYen 900 per 100 pcs box!) together with very cheap heat-shrink insulator covers (USD 7.0 = JPYen 1,000 per 10 m!) which I use only 2 cm for one crimped terminal.

As I have already shared here #28 and here #137, I use AWG10 and AWG12 multicore Vinyl Cabtyre (VCT) cables as SP cables in my audio setup since I do need so many rather long (about 8 m) SP cables from amplifiers to SP drivers, and I have been sticking to "tin-electroplating pure copper cable terminals".

Throughout my long-year journey in audio DIY, I have noticed (at least for myself) the tin-electroplating copper terminals would be better than banana plugs since the very thin tin film on the surface of pure copper, by tightly screw-up, effectively increases the nice metal-to-metal contact surface areas. For further safety measures, this time I installed heat-shrink insulator covers to all the terminals.

We do need to use suitable reliable and robust cable strippers and crimpers;

And, robust and quickly-heating-up heat gun for heat-shrink the insulator covers;

After such renewal of SP cable terminals, the SP binding posts of the four HiFi integrated amplifiers are now like in this photo;

The L and R SP cabling boards beside the SP systems are like in this photo now;

The backside view of the right SP system is now like this photo, and the same for left SP system;

BTW, after sharing my latest setup in my post #774, I decided to replace ASIO4ALL with VB-AUDIO MATRIX which now works as system-wide one-stop ASIO/VASIO/VSIO routing center (ref. #851, #854 and #858) within my upstream Windows 11 Pro PC.

The standard (default) PC screen layout during my daily audio listening sessions is now like this; I can see/monitor all the on-screen peak meters of DSP "EKIO" output panels, all the peak-meters for the input and output channels of VB-Matrix.

As intensively shared here #535, and also shown in above photo, the DIY-built 12-VU-Meter Array (IEC 60268-17 compatible) also monitors;
- total sum input signal,
- line-level input into the active L&R sub-woofers,
- SP high-level outputs of all the four amplifiers


Edit on January 31, 2024: please also refer to my post here #906
- Renewal of SP cabling boards beside SP systems: #906

 

[gac800]

Wow! that is quite an intensive cleaning. Your wire set up looks amazing.

i just received my protection capacitors, so I am looking forward to implementing them and sending an update.

I have also been evaluating amplifiers for my super-tweeters, and I am between the Topping PA-7 Discrete, Pioneer A-10AE and the same Yamaha A-S301 you have. The Topping has a very good review but it is twice as expensive as the other two.

 

[SSS]

Nice cabling work. But why "protecting" capacitors? There is no need for but may influence the sound.
Further I would crimp and solder the spades. Myself I prefer for the cable banana plugs to connect to the amplifier outputs.
Non-magnetic is OK but also not necessary to my experience and opinion.

 

[gene_stl]

Protecting capacitors are there, to prevent an amplifier output device failure, from blowing the unobtanium (Be)midrange and tweeters. ( by applying a power supply rail voltage at high current availability) When properly selected which @dualazmak has done they are unlikely to be audible. They are essentially electronically transparent.

 

[SSS]

Protecting capacitors are there, to prevent an amplifier output device failure, from blowing the unobtanium (Be)midrange and tweeters. ( by applying a power supply rail voltage at high current availability) When properly selected which @dualazmak has done they are unlikely to be audible. They are essentially electronically transparent.

Of course I know this and capacitors can be used. The argument to prevent bass tones from the midrange and tweeter is questionable since the crossover should do this. What about the woofer? Is there no protection capacitor? Prevention from high DC value can be done with so called crowbar circuit which shortens in case of DC. I agree that a capacitor is easier to implement. And using relais like in many amplifiers might not be perfect over time due to contact degradation.

 

[gene_stl]

@dualazmak performs more maintenance on his system than most of us and if he used relays for protection I am sure he would maintain their contacts.
Woofers don't get blown as easily as midranges and tweeters and are rebuildable too. There are people that are rebuilding Yammie Be drivers but it's better just to protect what you have. In my system I used 250 ma fused in series with the MR and TW and had 500 ma at the ready for when they blew. they never ever did. In spite of some very loud
listening.

Crowbar circuits and relays may not be fast enough to protect tweeters.