Incorporating MiniDSP With Audyssey XT32

[ski2xblack]

Pogre, I updated a post on the previous page with illustration describing the crossover changes that Andy and I are going back and forth over regarding passive bi-amping and messing up the crossover. I think it may be relevant to you, as you don't want to compound your mid bass issues by not sticking to well established and supported practice when blending your subs to your mains, or, similarly, passively bi-amping your speakers. I'll repeat: those extra binding posts are there due to market forces, not because passive bi-amping is a good idea.

Good luck with the 'crawling for bass' exercise, and keep us posted.

 

[PENG]

Yeah, perhaps you're correct Peng. This is a learning opportunity for me, so let's look further.

If one arbitrarily boosts the low pass part of the above idealized graph, will the new, boosted signal have the same slope? It should, it's going through the same inductor and other passive bits after all. Will the f3 be the same frequency? I'm not really sure, but if it's not, at least relative to the hp signal, then the lp and hp won't sum flat.

I think it depends on how "arbitrarily" mean. If the amps, the drivers and the LP filter used are operating well within their limits, f3 should remain the same. It is no different than adding a more powerful external amp to an AVR. Power increase does not automatically change f3.

Anywho, I still feel that tweaking sub amps, or the amps used for passive bi-amping of speakers, seems like a really expensive and potentially problematic method to affect tonal changes, which is better done upstream by tone controls and eq. Setting up crossovers between subs and mains is fundamental to system setup, and should be "set and forget" once accomplished, for optimal freq and impulse response. Once you have that, then eq to taste.

Agree in general, say 90%. I have amps sitting around but never even bother to try passive biamping because I do not believe the theoretically difference will be audible, not worth my efforts. For those (Pogre) who really want to try, the efforts involved would be relatively simple if identical amps (such as the spare channels of the same amp) are used, otherwise one has to make sure the gain structure of the equipment involved allow for proper matching.

By the way, active sub when used with an AVR's subout, is technically speaking a form of active biamp.

 

[PENG]

What? Sorry, bra, I refuse to get into some sort of pissing match with you about this. I have said nothing that contradicts basic filter theory, but I don't know everything and am here to learn while we discuss Pogre's system (not yours, not RBH, or anything else you hold dear...start your own thread if you want to push gear you're a sales rep for).

If you can answer the question I asked in my previous post, go for it. Here's my take, fwiw:

The f3 will be at the exact same frequency, as nothing has changed that would alter that, and the results of boost would be like so (and @PENG, this should contextualize what I was asking about):

This applies if we're talking sub/main crossover, as pictured, or a mid-woof/tweet crossover in a passive bi-amped setup. Even if those boosted bass plots did manage somehow, miraculously, to sum reasonably smoothly (fat chance), it would exhibit a significant shelf at frequencies below that, which is a problem in itself. I prefer a smooth 'house curve' at the main listening position, not some boomy shelved bass response. But that's just me.

Okay, I didn't read this post until after I responded to your earlier one. I think now we are in agreement and I guessed right that were were talking about different things earlier.

You will have the same effect by boosting the sub channel level in the non biamp case though.

 

[ski2xblack]

Okay, I didn't read this post until after I responded to your earlier one. I think now we are in agreement and I guessed right that were were talking about different things earlier.

You will have the same effect by boosting the sub channel level in the non biamp case though.

Yes, that's true, which is why Pogre should be cognizant of this aspect as he calibrates his rig. He will be introducing issues by using the sub channel gain (or the amp driving the woofs in bi-amped speakers) as a sort of ad hoc tone control, issues that no amount of fiddling with minidsp or Audyssey can correct. If he calibrates his sub/main correctly, those issues won't occur.

 

[ski2xblack]

We're all very proud of you for your material success. Would you like a pat on the head? And what does your rental property have to do with Pogre's bass issues? (Soap opera, indeed.)

 

[PENG]

If NHT powers the separated passive internal bass XO of the Classic Four tower with an external ACTIVE CROSSOVER and AMP, does that make this ACTIVE BI-AMP ?

But did they?

I didn't think you could do this (active external XO & Amp powering the passive internal XO).

I thought you had to remove the passive internal XO first.

That's what I thought too, if you want good result.

Yet, at least 2 big companies have done this.

Which way? With the internal crossover removed, or just separating the LP and HP, please clarify. If they did use external crossover and amp to power the bass section without removing the internal crossover, could you please post a link to a reliable source.

 

[Pogre]

How about moving the LP a little bit?

I have moved the lp around to where it is now. I can either move further away or off center. That's about it. I'm already 14ft from the towers and there's 11ft between them.

Is there an app or online schematic maker or something where I could draw out my room, furniture, etc.?

 

[Andrein]

I have moved the lp around to where it is now. I can either move further away or off center. That's about it. I'm already 14ft from the towers and there's 11ft between them.

Is there an app or online schematic maker or something where I could draw out my room, furniture, etc.?

MS Visio if you are ready to pay

 

[William Lemmerhirt]

I have moved the lp around to where it is now. I can either move further away or off center. That's about it. I'm already 14ft from the towers and there's 11ft between them.

Is there an app or online schematic maker or something where I could draw out my room, furniture, etc.?

Still on vacation so I can't look. I think it's called awesome house? I got it free. It's kinda fun.

 

[KEW]

Is there an app or online schematic maker or something where I could draw out my room, furniture, etc.?

Here is a good summary. If you already know AutoCAD, the student/faculty version is the way to go if you know someone who qualifies (I believe they look for an email address that ends with ".edu"). Otherwise Sketchup is well established and should have some good videos on how to use it.

https://www.thoughtco.com/top-free-cad-packages-485330

 

[AcuDefTechGuy]

But did they?

That's what I thought too, if you want good result.

Which way? With the internal crossover removed, or just separating the LP and HP, please clarify. If they did use external crossover and amp to power the bass section without removing the internal crossover, could you please post a link to a reliable source.

https://www.soundandvision.com/content/nht-classic-four-surround-sound-speaker-system-page-2

Read it over and let me know what you think.

There seems to be about exactly 0.1% interest in this topic, so I can understand if we just move on and talk about something else.

I remember about 20 years ago when I read about how they did that with the NHT Classic Four, I was very interested. But it seems I'm the 0.1% party.

I can't remember which magazine said this, but I recall they said without the external XO and amp, the Classic Four's F3 was like 35Hz or something. But with the external XO and amp, the F3 was 28Hz.

But all they did was remove the JUMPERS and used the external XO & Amp, which means the passive internal XO is still intact.

 

[PENG]

https://www.soundandvision.com/content/nht-classic-four-surround-sound-speaker-system-page-2

Read it over and let me know what you think.

There seems to be about exactly 0.1% interest in this topic, so I can understand if we just move on and talk about something else.

I remember about 20 years ago when I read about how they did that with the NHT Classic Four, I was very interested. But it seems I'm the 0.1% party.

I can't remember which magazine said this, but I recall they said without the external XO and amp, the Classic Four's F3 was like 35Hz or something. But with the external XO and amp, the F3 was 28Hz.

But all they did was remove the JUMPERS and used the external XO & Amp, which means the passive internal XO is still intact.

I read it and to me, that is basically a variation of passive biamp, perhaps a hybrid because the use of external electronic crossover could provide more flexibility that may or may not be meaningful. I can see some potential advantage of such scheme but in my opinion it is much better to save that $800 worth of external crossovers and spend it on two subwoofers. Using a more powerful amp instead of those 200W class D monoblocks for a normal passive biamp scheme is obviously a more straight forward way for more (0.2%) people.

 

[Pogre]

Pogre, I updated a post on the previous page with illustration describing the crossover changes that Andy and I are going back and forth over regarding passive bi-amping and messing up the crossover. I think it may be relevant to you, as you don't want to compound your mid bass issues by not sticking to well established and supported practice when blending your subs to your mains, or, similarly, passively bi-amping your speakers. I'll repeat: those extra binding posts are there due to market forces, not because passive bi-amping is a good idea.

Good luck with the 'crawling for bass' exercise, and keep us posted.

I've never seen those illustrations before. Very interesting stuff. Educational.

I've done the sub crawl a number of times and it keeps pointing me to that front wall where they are now. I do have some ideas for nearfield placement, but that's with buying 2 more subs. I'm gonna look at the couple of suggestions I got from Kew and Liam and see if I can draw a layout of my living room.

 

[AcuDefTechGuy]

I read it and to me, that is basically a variation of passive biamp, perhaps a hybrid because the use of external electronic crossover could provide more flexibility that may or may not be meaningful. I can see some potential advantage of such scheme but in my opinion it is much better to save that $800 worth of external crossovers and spend it on two subwoofers. Using a more powerful amp instead of those 200W class D monoblocks for a normal passive biamp scheme is obviously a more straight forward way for more (0.2%) people.

I was thinking more for the few people who already owned a spare amp and/or didn't want external subs for any reasons.

For people who are already passive bi-amping anyway (at least for the 2 brands I mentioned), perhaps this may be a more effective way than the usual way of passive-biamp because it allows them to tweak only the bass gain/level.

For example, if someone is 100% happy with the mid/highs, but just want to adjust the bass gain without resorting to manual EQ or Tones Control, and didn't want to use their subwoofers for any reasons, this may be a better way.

They wouldn't be messing for the salient mids/highs. They would only be adjusting the bass.

ANYWAY, I think we've said enough on this topic.

 

[Pogre]

Okay! I moved some stuff around, ran room correction again and took measurements and overlayed with the previous set of measurements. I pulled my mains further out from the wall a couple inches and pushed them a little bit closer together. I also moved my subs closer together. They're almost right up against my entertainment stand now and there's more room between them and my towers now.

This is before and after with DEQ on (green is before). It does look a little better now. It's audible too. I'm hearing a definite improvement. My bass response feels more even now.

This is with before and after with DEQ OFF (purple is before). I titled this one wrong, but fixed it before I saved it last night. Again, not huge, but it is audible.

Here I set the crossover at 200hz just for shits n grins. All of my previous graphs are an average of 6 different measurements taken in and around my seat. This one is just a single sweep from the mlp.

Bottom line, I can hear the small improvements shown in the graphs and I'm pretty happy with it, though there's still a little room for improvement. Right now the ports on the backs of my towers are ~20" from the wall behind them and the left speaker is about 20" from a boundary wall. The right one is... I'll post a couple more pics.

 

[Pogre]

These show better where my speakers are in relation to room boundaries.

One big difference I noticed (but haven't measured yet) is the bass bloat from the towers in direct mode is almost completely gone. I think that might make things a little easier for Audyssey?

*Edit: I did move the mlp further back over a foot. The same nasty dips are still there, they just moved up in frequencies so I pushed it back.

 

[MrBoat]

I don't know if it makes a difference because I am new to separate subwoofers but, does upfiring, or downfiring make any difference in situations like this with windows close to speakers or what looks like a sliding glass door in the room?

 

[William Lemmerhirt]

Hey J. You should set your vertical from 45-105 for a 60db window. I think it's more accurate.(also the REW help files mention this too). Anyway, not sure if the shallower roll off is a tuning change, but it looks significant to me. More interesting is the trough from above 50-90hz. To me it's deep enough and wide enough to be an issue, since that's an important frequency range. Especially at a 12db difference. To me since the XO is 80hz, you have a phase issue. Since the subs are gain matched you might try adding and subtracting a foot at a time in the avr and measuring again. If you add feet in the avr it will shorten the delay time to the sub signal and A) possibly level out the trough, and B) improve impulse response. Maybe...

 

[PENG]

More interesting is the trough from above 50-90hz. To me it's deep enough and wide enough to be an issue, since that's an important frequency range. Especially at a 12db difference.

I think he had DEQ on.

 

[ski2xblack]

I think William is correct. Now that's not absolutely certain, but if that is in fact a phase induced notch, you should be able to make it go away. (Kudos on being able to actually have a phase notch show up in your measurements, as it's most often obscured by modal response with 'in-room' measurements from the listening position. The close proximity of your subs to mains, and having a couple of subs for modal smoothing may account for being able to actually measure it. You're in the home stretch with this.)

That sort of notch will appear if the hp and lp are slope and level matched but 180 degrees out of phase. If the subs have a simple two position phase switch, take a measurement with it toggled to the other setting first, before changing sub distance in the AVR. If that does not reduce or eliminate the notch, then do as William suggested and add distance incrementally and re-assess until you get there.

If you can make the notch go away by adjusting the phase/distance settings, next look at impulse response. You'll find that you will get flat freq response, but the impulse response may be off, a full cycle or an integer multiple of that at the crossover frequency, which is more than a simple polarity switch on a sub can accommodate. You can then use the AVR distance settings, which can accommodate this, to restore or achieve optimal impulse response; it may help you dial in impulse response to add distance to the mains rather than to the subs depending on which, hp or lp is leading. The distances you set in the AVR may have no relation to actual distances in your room, or they may. Trust the measurements when doing this.

You get all that taken care of and you'll start to notice more resolution and detail in the critical mid-bass band than you realized was possible.

Excellent progress, Pogre!