Monitoring section

[Ian MacGregor]

Jaako (or anyone else),
Do you know of a US distributor of ELMAs?? I would prefer to use them above all other switches, but I had the idea that they were very hard to get here as well as very expensive.


Ian

 

[poomka]

Please help me

Thanks

 

[Kev]

What's the problem ?
... locating the switches or the whole design in general ?

http://www.goldpt.com/

check out the DIY section for some basic ideas
http://www.goldpt.com/diy.html

 

[poomka]

Thanks Kev for the switch link, I found usefull informations on the website.

I have a few more questions...

1/ I understood that the impedance of my box will change depending of the attenuator position, does it affects the sound ? Should I go for an active way to avoid this ? If so, what kiend of input/output stages I should go to keep the path as transparent as possible ?

2/ Should it be better to keep the signal balanced through the all path ?

3/ How could I measure the inputs/outputs impedances with a simple Ohm Meter (if possible)

4/ How to explain the sonic differences beetween the short and the long path, if the wires and switches couldn't be incrimined ?

Once again, many thanks, and excuse my ignorance...

 

[BradAvenson]

[quote author="Ian MacGregor"]Jaako (or anyone else),
Do you know of a US distributor of ELMAs?? I would prefer to use them above all other switches, but I had the idea that they were very hard to get here as well as very expensive.
[/quote]

They are avaliable from http://www.percyaudio.com/

They also have shalco attenuators (43 position!)

But very expensive.

 

[Ian MacGregor]

Wow, thanks Brad. Finally I can get ahold of some good swedish action! hahah.

 

[Kev]

[quote author="poomka"]I have a few more questions...[/quote]fire away

1/ I understood that the impedance of my box will change depending ....

Yes, impedance is likely to change with position. This can be solved with some trickery however it may not be necessary and can depend on you application and specification.
If you were to go active then your specification and standards will be the judge on what I/O stages are adequate. Everyone has a different opinion to what sounds good and how much headroom and drive is required. Not easy questions to answer definitively.

2/ Should it be better to keep the signal balanced ...

Keeping the signal balanced is possible and may be desirable if you latter find you have noise issues. I still don't see how you can have passive balanced operation with the phase reverse option.

3/ How could I measure the inputs/outputs impedances ...

Not that simple and does require a more sophisticated test method. I think you have more to think about at present.
We could look into this later.

4/ How to explain the sonic differences between ...

:roll:
!!!!!
... err
how long is a piece of string ?
There are some that say that even a piece of wire can impart a sound of it's own.
This can be a can of worms in the HiFi world and so can the above question about I/O stages. Not trying to duck the question but only you can make the ultimate choice here. Budget and final expectations need to be well understood before buying or beginning construction on any project.

If I understand you correctly, you already have some parts and components. It might be better to get them into a working state and then have a think about adding to them or reworking the whole project. In the mean time you will have a something that is working that you can refer to and the parts are not going to waste.

 

[barefoot]

I listened to both files and I hear very little difference, other than perhaps a slightly elevated noise floor in the CR file - which you would expect. I also did some spectral analysis, and the data supports the lack of difference.

The whole premise of this thread actually bugs me a little. If the goal is to improve the transparency of your monitoring system, why are you wasting all this time tweaking on things like "wire nature" and switch quality when their effects are marginal at the most? How about looking at some far more obvious targets first? For example....... your monitors. The BM15(a) is about the least transparent monitor I can think of in its class!

Here is an excerpt from one of my posts over at R/E/P

• "As for the BM15, sorry to say, but a 10" 2-way is simply WRONG, WRONG, WRONG! Nobody has been designing serious speakers this way for twenty-five years. A 10" midbass driver is INCAPABLE of reproducing anything but mediocre midrange at best - not the 24W100, not any 10" using current technology. I personally feel 6.5" is the maximum size for modern high performance midrange. Even then, you have to be very selective.
  
  If you want good midrange performance, get a small 2-way. If you also want deep bass extension, get a pair of subs or a 3-way. Don't mess around with this BM15 anachronism."

I usually don't express such strident opinions about specific monitors, but I can't stress enough how out-of-date the design and sound of this speaker is. Want to significantly your improve you monitoring system? Replace those dinosaur monitors. Then take a hard look at your room acoustics. Once you have the best monitors and room possible, plus a ton of extra time to burn, then you can worry if Teflon insulated wire "sounds" better than PVC insulated wire.


Thomas

 

[sismofyt]

I agree with twoway 10" speakers, allthough the 10" dual concentric Tannoy do sound nice :grin:

6,5" is just about right. But you don't get a lot of low freq extension. My pet peeve is three way systems with a x-over between 250-500Hz, they all sound WRONG to me. That's not the place to x-over, ime/o.

 

[Kev]

Sorry Thomas but as far as I am concerned the point of this thread was to help poomka set up a simple switch box to allow for a couple of options in monitoring.

This would also help other DAW users get from DAW output to Monitor Amp input and still provide just a couple of necessary monitoring needs. This is a big advantage when using powered monitors that are mounted further than an arms length away from you.

Here is his first schematic :

I too want to keep close to this very basic idea and NOT get bogged down in the Elma and Linear Crystal Oxygen Free cable stuff.

So I was trying to get into a position to better use the components he already has :

Running some A/B tests, I found my module to not be so transparent...

I can only take pooka's word on that and assume that it has something to do with the equipment combination and/or use.

 

[poomka]

Thanks for answers

Kev, I really appreciate the time you give me

impedance is likely to change with position. This can be solved with some trickery however it may not be necessary and can depend on you application and specification

Is it the inputs, outputs or both impedances which are likely to change ?
How could I know is that change is critical in my case ?

If you were to go active then your specification and standards will be the judge on what I/O stages are adequate. Everyone has a different opinion to what sounds good and how much headroom and drive is required. Not easy questions to answer definitively

What's your personal recomendation for the more transparency ?


barefoot

I listened to both files and I hear very little difference, other than perhaps a slightly elevated noise floor in the CR file - which you would expect

Thanks for take from your time to listen the posted samples, I understand that from your point the difference is not that critical, do you have any idea of the source of those differences ?

I also did some spectral analysis, and the data supports the lack of difference

Because of my bad english, I'm not sure to understand what you mean in this sentence, could you explain "the data supports the lack of difference" ?

The BM15(a) is about the least transparent monitor I can think of in its class!

I haven't heard all the monitors in its class, I just well know the Genelec 1030/1031 and the Mackie HR824 which from my opinion are much worse than the Dynaudio, I had a look on your website, your monitors looks nice but aren't in the same price range by far...

 

[barefoot]

Here are the spectra. The RMS levels have been normalized and the CR curve (orange) is laid over the XLR curve (Green).

Since perceived loudness is very dependent on the tonal character of the music, simply normalizing the RMS might not be a good comparison. However, the shapes of these spectra are almost identical, so this method is perfectly valid. And when you listen to the two files they indeed sound virtually identical. Like I said, however, the CR file seemed slightly less detailed, but the difference is very subtle. And I attribute this difference to slightly more noise in CR file, since it is single ended and -6dB quieter. The spectra support this as well. You can see that the XLR file has is just a little less smooth. It pokes out above and below the CR line in several places. This makes sense because broadband noise, integrated over time, will tend to smooth out the spectrum. And this is exactly what we see in the CR file. It's just a tiny bit smoother.

Of course there could be other differences in the time domain, but this is a passive circuit without any inductors or capacitors. There is absolutely no reason to suspect such differences at audio frequencies.

So, to my ears and my eyes, the only significant differences between the two signals are the RMS level and relative noise level.

As far monitors, an easy comparison is the BM15 and the BM6. If possibly try putting these monitors side by side. Use a high pass filter to limit the BM15's low end, so the extra bass doesn't bias you. Then listen to the difference in the upper bass and midrange. You'll be astonished.

Thomas

 

[Kev]

Thomas,

The spectral analysis is great and the explanation and interpretation of the noise/smooth bit is very cool. Nice to have the tools and the experience to help understand what our ears can identify.

poomka,

Is it the inputs, outputs or both impedances which are likely to change ?
How could I know is that change is critical in my case ?

The impedances of both input and output don't change but their interaction with the added circuitry that may change the energy transfer between the units.
As to whether this is critical in you case is not easy to answer with a single yes or no.

If the project grows to multiple outputs and the mono section, it is likely that loading effects will be present. You may find that you are happy with the consequences.

The output of the HD192 is not known to me. I think there is a schematic at Berklee PDFs and it might be worth a look to know what we are dealing with. I missed the model of power amp we are talking about ... or do we have powered monitors ?
Either way it is likely that the input will be of the bridging type and therefore an easy load to drive. This could work in our favour.

What's your personal recommendation for the more transparency ?

wow :roll:
can of worms again ...
short signal paths,
quality cable, quality connectors,
no switches :sad:
if we must have attenuators and switches then, again use quality parts.
as with all engineering it is often a compromise between cost and function.

I'm still not convinced that the circuit you have is going to give the performance you want with the HD192 outputs.
If you are trying to use the balanced line as two outputs
the first in phase and the second out of phase with respect to ground ... then I think I'd put the phase switch up first.
The mono mute section has me worried. This is were the load on the HD192 outputs is likely to change the most.
The attenuator, should be ok. This is all down to price and a dual tracking volume pot can be very expensive indeed.

does his make sense ?


Back to Thomas,

from above at the top of the page ...

As for the BM15, sorry to say, but a 10" 2-way is simply WRONG, WRONG, WRONG!
..... If you want good midrange performance, get a small 2-way. If you also want deep bass extension, get a pair of subs or a 3-way. Don't mess around with this BM15 anachronism.

This got me thinking about a DIY project with a difference ...
Source a small two way passive speaker with good efficiency and an excellent x-over region and good midrange ... possibly and probably at the expense of bass.
Use this is along side a second passive box with a single or dual woofer and use a passive or active filter to turn the whole thing into a three way.
By using the professionals to give the critical mid x-over area and then adding the cost benefit of DIY in the additional larger driver x-over and box area ... might work well.

If so, can you think of a current two way that might suit this Mid / Hi function. Cheaper the better, obviously. We might be able to come up with a combination well beyond the sum of the parts would suggest.

 

[Kev]

[quote author="buttachunk"]... your attentuators are the problem.

they are 10k attentuators, and 600 ohms is the average nominal impedence of the boxes you have. [/quote]
Looking at the web site and the PDF from the web site I can't find that info ?


Model BM15A
System 2-way Active Nearfield Monitor
Frequency Response
(+/- 3 dB) 30 Hz - 21 kHz
Max SPL 1m, pair(IEC Long Term) 124 dB RMS
Max SPL 2m, 5.1(IEC Long Term) 125,5 dB RMS
Input level for 85 dB SPL @ 1m (+4/-10) -18 dBu RMS / -34 dBu RMS
Input level for max peak SPL (+4/-10) +16 dBu peak / -1 dBu peak
Power consumption Idle: 40 W / Max: 300 W
Amplifier power Tweeter: 100 W / Woofer: 200 W
Resonance Frequency 39 Hz
Internal Cabinet Volume 27,5 liters
Bass Principle Bass reflex
Crossover Frequencies 1800 Hz
Crossover Slope 30 dB/oct
Tweeter Esotec 28 mm soft dome, rear chamber, Magnetic fluid. 4 mm die-cast alu front,
Woofer 24 cm, One-piece molded polypropylene cone, 100 mm pure alu wire voice coil
Weight 18,6 kg
Dimensions (WxHxL) 290 x 454 x 388 mm


ooo 5th order x-over ... never made one of them before ??? did make one 6th order for something but generally never more the 4th.

.... and from the PDF file,

Instrumentation type
electronically balanced
input stage


I find it a little surprising that it is 600 ohms input. It also offers the -10 input with -1 dBu to peak it out. This too is 600 ohms ???

I think I would be tempted to go with an unbalanced approach considering the functions you are trying to achieve.

Can we confirm that it is 600 ohms ?

 

[sismofyt]

Nobody uses 600 ohm transfer anymore. I'm 99,999999% sure the DynAudios have a regular 10-50kOhm input impedance. The kinda gear they're used with, Mackie etc, can't drive a 600 ohm input at reasonable levels anyway. Just because they have low output impedances, often all they way down to 10 ohm, doesn't mean they can actually drive anything that low.

 

[Kev]

agree'd

I'm still thinking a bridging input.

It is also likely that if you were to double terminate an HD192 it would begin to suffer if the termination did drop below 300 ohms.

Many of the single driver chips like the SSM2142 fall in a heap from 300 down.

This is were Kev's passive VU meter with termination switch can tell you so much about signal transfer. I always have two of these things nearby to check what is going on to a fist level.
Two of them can provide the means to double terminate.
Can also be used to look at stereo
... or one on an input and one on an output.

Things are so often not what you first think.

 

[poomka]

Many thanks for all the inputs,
it's so great to have competent people helping me.

Barefoot

Thank you very much for the detailed explanations about the spectra you made. As Kev said :

Nice to have the tools and the experience to help understand what our ears can identify

I will try to make the BM6 vs BM15 comparison as soon as possible.

Kev
Your inputs are very usefull, thanks so much.

if we must have attenuators and switches then, again use quality parts.
as with all engineering it is often a compromise between cost and function

I opened a summit DCL200 compressor, to see what kiend of switches they use, it seems to be basic switches as mines (speaking about the "bypass" toggle switches), but I'm not experienced enough to understand if their switches are connected to relays or not, Is it better to use relays for sound quality ?

(I opened too a SSL compressor and a Vintech X81, I made pictures, tell me if anyone could be interested, I will be pleased to post them)

If you are trying to use the balanced line as two outputs
the first in phase and the second out of phase with respect to ground ... then I think I'd put the phase switch up first

I just put the "bypass" switch before this one, that switch allows me during normals listenings to not pass by the phase/L-R invert/Mono/Mutes path, do you think it could be a problem ?

The attenuator, should be ok. This is all down to price and a dual tracking volume pot can be very expensive indeed

Here's the link for the attenuator I bought six months ago for about 100$, mine is Stereo (2 decks) version of CT1 in 10k. Does it seems OK to you ?


I send an e-mail to Dynaudio about the input specifications, I'm waiting for an answer.

One more time, many thanks to help me in this new wonderfull world of DIY

 

[barefoot]

[quote author="Kev"]Back to Thomas,

This got me thinking about a DIY project with a difference ...
Source a small two way passive speaker with good efficiency and an excellent x-over region and good midrange ... possibly and probably at the expense of bass.[/quote]
I'm happy to help. I don't have the time to do any building, but measurements and design are doable.

Thomas

 

[Kev]

Thomas,

no bulding required , just suggestions. I'll get back to you with some ideas ... but in the mean time , can you think of any budget 2 way speakers that caught you ears as being better in the top end and mid than their competitors. A very square and flat fronted box might suit my plan better than some sculptured units.


poomka,

Yes DACT was a link of the week at the old place a long time back ... they have more DIY stuff these including some neat little enclosures.

check out the balanced attenuator ...
http://www.dact.com/html/wiring_a_balanced_stereo_passi.html

yes I know
we don't have the 4 stack switch and we are unbalanced.

check out the multiple outputs app note ...
http://www.dact.com/html/multiple_outputs.html

if you were to reverse the idea and use it as multiple inputs ... that being one, the positive and the second, negative.
You now have you inverse phase ...
followed by the unbalanced attenuator
followed by another multiple outputs to create the L to R and R to Left ... this could also give the mute in the third position.

does any of this make sense ?

I'm still thinking about mono ... could be a forth position of the multiple outputs BUT it might be a bit of a hack job.
BUT I think it will work.

 

[poomka]

Thanks Kev, yo my opinion what you said always makes sense.

I have few questions, but I'm afraid not the last ones...

1/ Is it better to use relays instead of basics switches ?

2/ If I want to include a Vu-meter, could I stay with a passive path ?

3/ Could anyone recomend a good quality/cost cable for internal wiring ?

Many thanks again.