My short cut dsp with Dayton DSP 408 is working wonders

[newlash09]

Hi all...

I guess there are lots of threads dealing with mini dsp and REW. I got a umik-1 measurement microphone about 2 years back. But REW was always Greek and Latin to me. So after an initial tryst, I never bothered about either.

So in order to go active biamping as well as adress room nodes which were driving me crazy, I decided to give the Dayton dsp 408 a spin. Which at only USD 150/-, was also the cheapest and easiest around.

Despite being completely dumb at crossovers and room Eq,  two things that gave me confidence were :

1) It has a easy windows based desktop app, that enables one to change settings on the fly in real time, as long as it is plugged via usb into the laptop

2) It has 8 channels of outputs, and provides 10 point parametric Eq on each channel. Each Eq point allows "Q" value and "gain" setting per each Eq point. 

That was the easy part. Normally most folks would measure their room and apply Eq to try to cancel the peaks and leave the troughs alone. 

Since I didn't want to dabble in REW again, I used a simpler method. I used online room mode calculators, and fed in my rooms exact dimensions till the last CM. 

http://www.mcsquared.com/modecalc.htm

Below are the two room mode tables I got from the above online calculators. Then as can be seen in the attached paper pic below, I listed down all these frequencies, and marked those frequencies that were repeating in both tables. 

Next I applied eq uniformly of -3db, at all these room mode frequencies. Or where these frequencies were differing by 5 Hz, I took the center average. For "Q" value, as can be seen I've kept it uniform at 3.997 to keep it narrow, as I read room nodes are very narrow, and usually only 5 Hz wide.

I also forgot to mention that I also split the frequencies to the bass driver being driven by the krell till 600 Hz. And mids and treble being driven by tube amp below 200hz. All with the available linkwitz riley 24db per octave slope cross overs. 

The result it the best sound I've ever had in my room. It is sounding bloody marvellous now. Absolutely no bass boom.or bloat. The mid rnage , vocal clarity and treble have really opened up. The improvement is so promising , that the addition of some absorbers at first reflection points should take the system to another level. So Iam really over the cloud now. 

I know this is not the most scientific way of doing Eq.  But if some one has been wanting to give it a try, but hesitant like me. Then I fondly hope they find my post useful.

Another important thing was that I had my doubts if adding a cheap dsp in the chain would add unwanted noise. But I got a ifi ipower ultra quiet 12v psu for powering the Dayton, instead of using its supplied LPSU. And I find the back ground pitch dark. I have actually removed the preamp from the chain , and feeding the Dayton directly from esoteric via its inbuilt volume control. And the music now emanates from the darkest , most noiseless background ive ever had. And the dynamics are off the charts too

Thanks for reading my long rant

 

[PuritéAudio]

I would have another grapple with REW, it really isn’t that complicated, and once you have made one measurement , you can save the Mdat file and share it.

Then everyone can chip in with suggestions.

Keith

 

[newlash09]

I would have another grapple with REW, it really isn’t that complicated, and once you have made one measurement , you can save the Mdat file and share it.

Then everyone can chip in with suggestions.

Keith

Thanks sir

I will eventually do it at some point. But Iam over the moon at the moment

It took me 4 frustrating years to get to this sound quality. Maybe the sound I now have is not what the engineer intended. But Iam still blown all the same

But I will definitely post a REW graph, once Iam over the initial euphoria. Thanks a lot

 

[Camverton]

When setting up REW be careful with the volume. Start with the level low and increase slowly. There is a danger of a beginner blowing their tweeter, not to mention their ears.

REW is a great piece of software but does require a fairly steep learning curve to use effectively and understand the results. A little knowledge is a dangerous thing and for that reason I will not post my files here because one then has to decide between who is knowledgeable enough to make useful comments and who hasn’t really grasped the complexities of setting up the software and measurements and interpreting the results.

 

[tuga]

@newlash09 your post is a bit confusing.

It is obvious that you are bi-amping.

Which speakers are you using?

Are you bypassing the speakers' internal crossover or have you just removed the shunts?

Why did you decide to drive the krell up to 600Hz and the tube amp down to 200Hz?

Are the two amps overlapping between 200 and 600Hz?

 

[newlash09]

@newlash09 your post is a bit confusing.

It is obvious that you are bi-amping.

Which speakers are you using?

Are you bypassing the speakers' internal crossover or have you just removed the shunts?

Why did you decide to drive the krell up to 600Hz and the tube amp down to 200Hz?

Are the two amps overlapping between 200 and 600Hz?

Yes sir...it is a kind of semi active setup. The speakers are PMC twenty 26. The passive crossovers in the speakers are still there. But I've removed the connection links at the binding posts. 

The tube amps are connected to the mid range and treble bindings posts by biwire cables. 

The krell is connected to the bass driver binding post with a separate wire.

Considering the expenses involved in getting new drivers if something  went wrong, Iam leaving the passive crossovers in place. 

The bass to mid range crossover point is at 380 Hz. So to get a proper overlap Iam running the tube amps from 200hz upwards. And the krell from 600 Hz downwards. Both being linkwitz riley 24db per octave slopes. I would love it if I could move the tube amps further up the frequency range. So any suggestions are most welcome

 

[tuga]

Yes sir...it is a kind of semi active setup. The speakers are PMC twenty 26. The passive crossovers in the speakers are still there. But I've removed the connection links at the binding posts. 

The tube amps are connected to the mid range and treble bindings posts by biwire cables. 

The krell is connected to the bass driver binding post with a separate wire.

Considering the expenses involved in getting new drivers if something  went wrong, Iam leaving the passive crossovers in place. 

The bass to mid range crossover point is at 380 Hz. So to get a proper overlap Iam running the tube amps from 200hz upwards. And the krell from 600 Hz downwards. Both being linkwitz riley 24db per octave slopes. I would love it if I could move the tube amps further up the frequency range. So any suggestions are most welcome

I would like to suggest that you don't use the digital crossover. The passive crossover is still doing its job and you are probably introducing distortion by adding a second crossover.

I haven't looked at the manual, does removing the shunts will split the woofer from the other 2 drivers/ways?

 

[newlash09]

I would like to suggest that you don't use the digital crossover. The passive crossover is still doing its job and you are probably introducing distortion by adding a second crossover.

I haven't looked at the manual, does removing the shunts will split the woofer from the other 2 drivers/ways?

Yeah removing the binding post links in the back completely disconnects each driver from the other .

 

[tuga]

Yeah removing the binding post links in the back completely disconnects each driver from the other .

Does it have a pair of binding posts for each driver?

 

[MartinC]

I'll be honest I'm surprised what you've done has worked well @newlash09 but if you're really liking it then great  :^ .

A couple of quick comments based on what you posted are that 3 dB dips to counter major room modes would normally be rather less than would be needed, and the Q of 4 you've used is actually not particularly narrow but this isn't necessarily a bad thing. Narrow filters (high Q), particularly with higher gain, can have a negative effect because they can cause 'ringing' - meaning that sounds at that filter frequency take longer to decay than they should.

I'm with @tuga in that I'd question the wisdom of using the high and low-pass filters. To explain why below is a graph showing what the crossover to your Krell should currently be doing, which you'll note is something like 1 dB down at your 380 Hz crossover frequency. To not be having an adverse affect you'd want it to have a flat response right through the crossover region, which will extend above 380 Hz, and how far will depend on the specific crossover. Note that the graph only shows the amplitude effect and that there will be phase changes around the region where the response falls off as well. The safest plan is to not apply such a filter.

 

[newlash09]

I'll be honest I'm surprised what you've done has worked well @newlash09 but if you're really liking it then great  :^ .

A couple of quick comments based on what you posted are that 3 dB dips to counter major room modes would normally be rather less than would be needed, and the Q of 4 you've used is actually not particularly narrow but this isn't necessarily a bad thing. Narrow filters (high Q), particularly with higher gain, can have a negative effect because they can cause 'ringing' - meaning that sounds at that filter frequency take longer to decay than they should.

I'm with @tuga in that I'd question the wisdom of using the high and low-pass filters. To explain why below is a graph showing what the crossover to your Krell should currently be doing, which you'll note is something like 1 dB down at your 380 Hz crossover frequency. To not be having an adverse affect you'd want it to have a flat response right through the crossover region, which will extend above 380 Hz, and how far will depend on the specific crossover. Note that the graph only shows the amplitude effect and that there will be phase changes around the region where the response falls off as well. The safest plan is to not apply such a filter.

Thanks for your detailed reply Martin C...

The krell being 1 db down at 380hz due to the crossover might be true. But the tube amps have a gain of around 28 to 29 db.  And the krell has a gain of around 26db. Iam presently running the krell with no reduction in gain. But the tubes are being run at -2db gain on the crossover. Besides the tubes stated gain is at 100% gain setting on the gain knob placed at the back of each mono block. I've also reduced this to 50% to prolong tube life. 

The entire crossover frequencies, relative gain levels of amps and PEQ filters have been tuned by ear at my listening position. And so far Iam unable to make out any gremlins at the crossover range.

However on some tracks Iam finding the bass one notey at times. 

Iam not saying the blend is most ideal...but the sound is way better now. I have some long usb cables being delivered by tomorrow. Will post the REW graph with all peq filters removed. Then maybe you all good sirs, can suggest the exact shelving I need to add to remove the bass nodes. 

Coming to the topic of biamping.  The idea was to spare the tube amps the strain of producing heavy bass notes. And it definitely seems to be working. The mid rnage and treble have really opened up. And I feel the tube amps have become more nimble,  and are now matching the pace of the krell. Whereas on fast EDM numbers with deep bass....I felt the tubes were a tad slow at the pace I was used to with the krell. And no additional distortion has been added in the sound either

 

[newlash09]

Hi again @Martin C 

You were right...I had double checked and Iam running  actually -6db at both 37 and 74 Hz. With the others at -3db. Have removed every other PEQ  shelving, and just left the 37hz at -6db, and 74hz at -3db. Now I have better defined bass, instead of it being single note

Now really looking forward to REW measurements as soon as possible . Thanks

 

[tuga]

Thanks for your detailed reply Martin C...

The krell being 1 db down at 380hz due to the crossover might be true. But the tube amps have a gain of around 28 to 29 db.  And the krell has a gain of around 26db. Iam presently running the krell with no reduction in gain. But the tubes are being run at -2db gain on the crossover. Besides the tubes stated gain is at 100% gain setting on the gain knob placed at the back of each mono block. I've also reduced this to 50% to prolong tube life. 

The entire crossover frequencies, relative gain levels of amps and PEQ filters have been tuned by ear at my listening position. And so far Iam unable to make out any gremlins at the crossover range.

However on some tracks Iam finding the bass one notey at times. 

Iam not saying the blend is most ideal...but the sound is way better now. I have some long usb cables being delivered by tomorrow. Will post the REW graph with all peq filters removed. Then maybe you all good sirs, can suggest the exact shelving I need to add to remove the bass nodes. 

Coming to the topic of biamping.  The idea was to spare the tube amps the strain of producing heavy bass notes. And it definitely seems to be working. The mid rnage and treble have really opened up. And I feel the tube amps have become more nimble,  and are now matching the pace of the krell. Whereas on fast EDM numbers with deep bass....I felt the tubes were a tad slow at the pace I was used to with the krell. And no additional distortion has been added in the sound either

If I understand your amplification setup correctly then all you need to do is adjust the gain of the tube amplifier to that of the transistor amplifier and you should use a microphone for this purpose.

The speaker's crossover will deal with the filtering so no extra (digital) filtering is needed and there's a chance that it will actually be detrimental.

How many binding posts do the speakers have?

Regarding EQ of room generated peaks and "bass one notey at times", if before you were driving your speakers with the tube amp it might not be a bad idea to fine-tune the speakers' positioning. A transistor amp like the Krell should be giving you the opposite.

 

[newlash09]

If I understand your amplification setup correctly then all you need to do is adjust the gain of the tube amplifier to that of the transistor amplifier and you should use a microphone for this purpose.

The speaker's crossover will deal with the filtering so no extra (digital) filtering is needed and there's a chance that it will actually be detrimental.

How many binding posts do the speakers have?

Regarding EQ of room generated peaks and "bass one notey at times", if before you were driving your speakers with the tube amp it might not be a bad idea to fine-tune the speakers' positioning. A transistor amp like the Krell should be giving you the opposite.

Thanks sir

The speakers have 3 separate binding posts.

Yeah the positioning was done with the bass driver being 1/3rd the length of the room from the wall behind the speakers. I found this position to give the more natural bass in my room. The krell has only tightened up the bass further. I think using too many shelving filters below 300hz was leading to the one notey bass. Now it has been corrected after removing all the peq points, except at 37 and 74 Hz respectively.

 The only reason I am also using an external crossover is to prevent the tube amp getting bogged down driving bass frequencies.  As I notice a certain clarity and purity when it is just running mid range and upwards. And most importantly speed. 

I was just listening to "diesel power" from prodigy. Only in this active biamped configuration are the tubes able to keep up with the speed and bass of the krell on this very fast track. 

 

[tuga]

The only reason I am also using an external crossover is to prevent the tube amp getting bogged down driving bass frequencies.  As I notice a certain clarity and purity when it is just running mid range and upwards. And most importantly speed. 

If the shunts between binding posts were removed the tube amp won't be driving/seeing the bass drivers anyway; it is unlikely that high-passing the signal going into it will make a difference but it may not do any harm either as long as the knee is kept low enough (an octave perhaps below the passive crossover point in the speakers?).

I would rather not low-pass the Krell though.

 

[MartinC]

Yeah the positioning was done with the bass driver being 1/3rd the length of the room from the wall behind the speakers. I found this position to give the more natural bass in my room.

This is probably obvious but note that where your listening position is will be a factor here too. If you can vary both then it's the best combination you're after.

It will be interesting to see a measurement of what you have right now to see how well you've done by ear .

On one other point, even without your digital high-pass filter your tube amp won't be being 'asked' to provide the low frequency current for your bass driver.

 

[tuga]

This is probably obvious but note that where your listening position is will be a factor here too. If you can vary both then it's the best combination you're after.

Indeed. @newlash09 you can try positioning your seat 1/3 or 1/6 into the room as a starting point.