A how to for a PC XO.

[ShinOBIWAN]

1)It will be really difficult for me to set my system up outside, is there an alternative option?

I don't think most people do this. At least not until a fairly serious level.

More to the point though, DRC is about equalising the system *in-room*. You *want* to see what all the room reflections do to the system. Getting the anechoic measurement is great if you want to know how your system performs in theory (which is somewhat useful actually).

So measure in room and at the seating position for use with DRC.

I take it you haven't done too many DIY speakers Ed

DRC isn't a panacea to fixing all problems though.

Brad was specifically talking about creating an XO and the very best results are obtained by getting your frequency response, phase etc. into best case scenarios that simply aren't possible by talking measurements in room or at least not to the same degree of reliability. This how manufactured speakers work; they hit the designed transfer functions in anechoic conditions. The room is your problem they presume after this.

I've said it before but would you want a speaker that's anechoically tuned or one that's tuned to a specific room and a specific position? Think about it for a second and you'll realise that you need a point of reference and tuning anechoically is that reference. It allows you to move speakers, rooms, houses or whatever and you know that any deviations in performance are room related after this feel free to add DRC to then remove those problems.

So sort your XO out well before you even think about DRC. But don't tune your XO with respect to your room! Otherwise your then locked into that room and positioning. Should you change rooms or positions then you've to rework the XO. Setup the XO sans room and you can move between positions and rooms and only have to apply the DRC. Its a better and easier way of working.

 

[ewildgoose]

Again, I agree and disagree.

Yes, XO and DRC are two different things. I guess I wasn't clear about that. XOs are also probably easier done using an (pseudo) anechoic measurement

I don't see that for midrange up crossovers that it's necessary to move the speakers too far from a wall to get a pseudo anechoic measurement though. You can usually get sufficient time resolution using gated measurements (and I don't see a difference between putting the mic inches from the speaker or across the room? Apart from the drop in levels...)

I DO agree though that designing a good speaker is VERY hard. My point was that you need a lot more info, especially the off axis performance, which then lets you design good crossover points.

In this case though I was simplifying things because this is clearly someone looking to get started... I think that a good bit of practical experience would be learned simply substituting the existing crossovers for some steep linear phase ones. See if you can hear the ringing, or any improvements in off axis performance. After that you can have fun changing the crossover points as well

I'm not sure where you are going with your other points though? XO and DRC are seperate exercises. DRC is basically trying to overcome the room (plus any remaining speaker deficiencies). XO sets up the speaker. Given a choice you should do everything possible to get the room correct before applying DRC - there are quite definite limits as to what is possible using DRC (See my wiki for a good essay on the limits)

In summary DRC excels at:

a) correcting low freq behaviour
b) fixing fairly long reflections in the mid range
c) overall tonal balance

Consider point a) (which is what got me into this whole thing). I have a 20dB bump at 40Hz in my room! Can you recommend *ANY* traditional treatments which can deal with this and still have a reasonable Q on the correction? I have checked the calculations on helmholtz resonator and it looks like I would need a significant fraction of the entire room as a resonator to fix this with any kind of reasonable Q... (Actually if someone could check that calculation and confirm then I would be really interested!)

I haven't heard anyone with horns try DRC. This would be a really interesting bit of feedback...

Ed

 

[ShinOBIWAN]

I seriously doubt the DACs are really the limiting part of anyones system. I haven't yet tested, but I am prepared to put up DRC using the the really nasty built in soundcard on my PC up against a non-eq squeeze or RME card... Perhaps I am wrong, but whilst I think the DAC is a link in the chain I just don't see it being the weakest link. Don't worry about it (yet) to be honest

You do get to a stage though when you do hear the differences if your room and speakers allow you to resolve those differences. I've also learnt from experience that DRC compromises high and mid frequencies with microphones such as the fairly poor Behringer EMC8000, it just wasn't made to do this sort of work. This hit me when I originally used a hired Earthworks M51 mic to capture my impulses, I then later moved the speakers and redid the capture with the ECM8000, pretty miserable results and moved the speakers back to where I had them before and used the m51 impulse capture. I personally wouldn't use DRC without a top notch mic unfortunately that also means that we have to hire one unless we are prepared to front £££'s.
My point is why bother with decent DAC's if your impulse response capture has been smeared by a poor mic and with induced noise has an SNR of 100-90dBA or worse anyway? Get a decent mic and this changes.

Sorry it probably sounds like I'm getting on at you, that's not true at all. Its just I dislike claims that x isn't superior to y when in actual fact I've heard the differences. Its misinformation to say otherwise, its just that sometimes we don't hear these differences due to the fact that the DAC's aren't the weakest link in the system to begin with. I do however, agree that its possible to waste money on big expensive DAC's - I've done that That's diminishing returns territory.

I have 2 UCD amps and 2 Zappulse amps. I would be very interested to run your AKSA against either or both of these. The digital switching amps have a very strong clean bass and mid-range which is way better than my benchmark Meridian 557 power amp. However, the treble is not so superior (which not to say its bad), but I wonder if a top end traditional amp or the AKSA might not suit the treble end of a really high end system better...?

Lest this be damning with faint praise the UCD and Zappulse are full time in my system and the 557 is no longer used. For overall imaging and presence and clean sound I have heard nothing better (at all). However, my first switching amp had a too small powersupply and it acquired a very hard treble and since then I have been a little sensitive to improvements in the treble end (and these seem to have come as I built steadily better and better powersupplies for the amps)

You may or maynot be interested in my thoughts on the new UcD700AD vs. AKSA 55N+

I wrote a review over on Audio Circle comparing a friends recently built 4 channel UcD700AD amp with my own AKSA 55N+ Here were my thoughts:

Its now nearly 6:00 in the evening here in the UK and I've been listening to both amps all day with a wide range of music. I thought I'd got the amp until Monday but it looks like I'll be out all tommorow so I'll have to cut my comparison short I feel confident I have a good idea of the sound of each though. It doesn't take days and days to form an opinion. These are also just opinions based on comparing each amplifier in my system and room so please don't be offended if they don't neccessarily agree with your own experience's, chances are you don't own the same kit, don't have a room dimensioned and constructed the same as mine and your preferences are also probably different.

My comments about the AKSA posted at the very beginning of this thread stand.

When this amplifier is used with very revealing electronics it sounds cold and removed from the performance compared to the AKSA even with the best recordings I have - Chesky et al. Extremely accurate for sure and you always feel that your not missing a thing no matter how loud you play. But when I swapped back to the AKSA a lovely sense of musical pace, layering, smoothness and rhythm was very obvious that the UcD simply didn't have. I should note that it never sounded harsh nor grainy even when driven very hard.

Dynamics on the UcD are great, massive attack, good speed (not the equal of the AKSA though) and a general feeling of control right through the frequency range. The AKSA on the other hand is smoother but equally dynamic *provided* the volume is kept to sensible levels.

Bass on the UcD is much better than the little 55N+ but as Hugh already pointed out its 400w into 8ohm vs. 55w and that's nearly 8 times more power on tap. Elaborating futher on the bass; its got a real sense of power, punch and definition. I'm using ATC SCM7's which are only 83dB sensitivity although they are 8ohm. I know from experience these like power and lots of it 150-250 is recommended by ATC. The UcD has absolute control over these speakers at all times. If you read back to the first post on this thread my thought's on the AKSA bass is there, suffice to say it isn't a UcD700!

Soundstaging on the UcD is average to good. The presentation tries a little too hard though and it comes off as unatural and synthetic compared to a direct comparison with the AKSA. When listening to music recorded in a venue with natural acoustic's the AKSA absolutely destroys the UcD in everyway, much more natural and the reverberation, decay and layering are so real as to be palpable on the AKSA - you feel like you are there and not just listening to a facsimile. You hear all this on the UcD but its presented in a less believable way.

Imaging on the UcD is a big WOW! Soundstaging and imaging are often confused and maybe I'm guilty of that but for me soundstaging is the ability to relay the event, acoustics and overall space of the sound whereas imaging is how well defined and dimensioned individual aspects are within this soundstage. The UcD may suck a little with soundstaging but boy does it know how to image! Even with the most complex of mixes you can follow an individual sound and it remains stable, focused and coherent in respect to the rest of the performance. The AKSA on the other hand is a tad blurred in comparison on very complex material and you have to listen harder to make out what seems to come naturally and without strain from the UcD.

Detail on the UcD and AKSA are around about the same but again I'd definitely give the edge to the AKSA in providing those details with more 'electricity' whilst maintaining a sense of absolute calm and smoothness that the UcD doesn't quite do in the same manner. Its just a difference of presentation and someone's favourite could be easily swayed by preference - I prefer the AKSA here but I do rather like the UcD also. Overall I'd say its down to personal preference rather than absolute superiority of one machine of the other.

The speed/pace of an amplifier is a rather daft idea on the face value. Afterall how can one amplifier be quicker than another? Its all down to presentation, system synergy and tonal balance which really defines how fast an amplifier sounds and the AKSA is perhaps the ultimate amp on the planet in this regard. Its massive speed allied with an effortless smoothness is a huge paradox but one that is utterly alluring and not easily forgotten. There's no way the UcD can even hope to hold a candle to this.

To sum up:

First off, the UcD700AD is a good amplifier and anyone who owns one should be proud. In the right system I imagine it can sound fantastic (my friends for example). However in my system it just doesn't work as well as the AKSA. Maybe the combination of extremely revealing frontend, studio monitoring speakers and the matter-of-fact delivery from the UcD just doesn't gel well for musical enjoyment. I imagine for monitoring and mastering its a doozy though since you can hear everything and know exactly what is going on and what's wrong with a mix.

The AKSA is an audiophile product, proud to be coloured and all the better for it when it comes to actually enjoying music rather than just listening to music.
Whats clear is Hugh has masterfully crafted these colourations into something that bridges the gap between the recording and the original live venue. Is it accurate? Not in respect to the recording no but it does bring you closer to the original spectacle and surely this is what enjoying music is about?

This little test has been great fun and its only cemented my opinion of the AKSA. I suspect that when I do the comparison to Greg's SKA things maybe somewhat closer but as far as 55N+ vs. UcD700AD, I'd take the AKSA for my system any day.

Now to order an 100N+ Hugh are you listening? I want an 100N+, like, yesterday.

The whole thread is here if you wish to read it:

http://www.audiocircle.com/circles/viewtopic.php?t=24944&start=10

 

[ShinOBIWAN]

I'm not sure where you are going with your other points though? XO and DRC are seperate exercises.

Eh?

But I just said:

"I've said it before but would you want a speaker that's anechoically tuned or one that's tuned to a specific room and a specific position? Think about it for a second and you'll realise that you need a point of reference and tuning anechoically is that reference. It allows you to move speakers, rooms, houses or whatever and you know that any deviations in performance are room related after this feel free to add DRC to then remove those problems."

Maybe its still not clear what my point was so to paraphrase my earlier post:

-Do the XO and tune the speaker without room interaction - how you acheive is up to you. I've suggested gated and semi-anechoic and both work. After this marvel at just how close you've come to a theoretically perfect speaker or not.

-Then place them in your room, re do the far field measurement from the listening position and cry at how messed up it all is!

-Apply DRC after this and see it return back to something like its former good self. Don't however use DRC to fix problems in the XO, use it to fix ROOM related problems. If you ensure that your XO is sorted before your speaker enters the room, you can be sure that all DRC is fixing is infact the room. Doing all XO work in semi-anechoic conditions ensures that DRC is only dealing with room issues and not a poorly designed XO as well.

 

[ShinOBIWAN]

Now, coming back to the question asked before as to how you design a crossover. First get a book like Vance Dickason's Speaker Design Cookbook. From this we learn that clean impulse response and smooth off axis response are what makes a really good speaker. ie it's not enough to just have direct sound from the speaker to the listener - you also need to think about what gets radiated sideways and bounces off the sidewalls.

A man after my own heart.

Offaxis response is IMO the most important part of a great sounding speaker. Our hearing mechanism gains detail, information and phase related cues from direct sound but the reverberant sound field gives us the further acoustic cue's such as power response, magnitude and acoustic space. As you've said, it needs to be uniform in magnitude and phase to be considered accurate. Sharp dips in off axis response or shifts in phase considerably blur the music.
It sounds like something simple but it is not! You need drivers designed with these factors in mind AND you must have ones that are intimately compatible with each other. Most importantly you need to build you XO to sympathise with the ideal of uniform off axis response and it could be that you have to sacrifice a little on-axis response to achieve this. Of course this mean lots of testing for off axis response at various angles and then highlighting favourable choices for crossover points between the drivers to ensure smooth magnitude response over a wide angle. Linear phase filters also help ensure that once the fundamentals are determined, that there isn't disruption to the equilibrium you've created in your design.

OK, so 101 time. Assuming you hear the direct sound plus the sidewall echos (etc), then it's clearly important to have really smooth off axis performance. But now check the response plots of that nice driver you were looking at. See the off axis performance... eughh. VERY few pistonic speakers have a really nice off-axis response (the Orion is pretty decent I think?) Bass is omni directional and treble is highly directional and so the off axis performance is not as smooth as the direct sound (often with horribly peaked response at some frequency as the comb filtering from treble and mid combine)

The best approach is omni direction low end and a gradually narrowing response. This is completely natural with all drivers, however its important how smooth that transition from omni to directional is and how quickly or slowly it occurs.

- Combining two drivers causes comb filtering at the crossover frequency (so we want steep crossovers)

Steep crossover can actually make things worse. To explain further; whilst linear phase XO's do exhibit ideal phase in the electrical domain the acoustic domain is a different matter altogether and steep rolloff can cause very audible phase shifts within a narrow range centered around the XO point. To combat this you need to physically time align drivers and ensure similar dispertion properties around the XO point between the two drivers.

- Steep crossovers can cause a large phase distortion (time lag) at the crossover frequency. This can be somewhat fixed using digital crossovers under some circumstances (linear phase)

Agreed but again its important to draw a distinction between electrical and acoustical domains.

- Shallow crossovers sound great but may allow the driver to enter into a range where it's not optimal, increasing distortion

Absolutely agree

So it's a tradeoff, but your Orion uses carefully optimised 4th order crossovers called Linkwitz-Riley which the designer things cause inadible phase distortion. You *might* improve the speakers by using steeper linear phase crossovers which would keep the crossover interval much smaller.

I suspect that the synergy will be broken and the original design compromised by such a move. Better to design with an eye towards steep filters than to design and maybe include steep filters.

So in conclusion look to DRC to improve your speakers in room. Also look to the PC crossovers to give you a chance to play with some steeper crossovers than the ones you use at the moment (but be prepared to decide it's not a good enough advantage to be worth it).

The author of the DRC software believes that his correction is sufficiently good that it can correct for the problems in the LR crossovers you use, meaning that he doesn't think it's worth playing with digital crossovers... So DRC alone should be a high bar to beat..

I'd agree that Brad should probably just try DRC to start off with and forget about the XO part for the time being. Its a subtle improvement in comparison to a competant analogue active design - which surely the orion is? DRC offers an immediate improvement with relatively little hassle and expense, the XO on the other hand requires considerably more determination, experience and time.

 

[ezkcdude]

Sorry to but in here, but I have a quick question. Are there add-ons for the RME cards for digital outs (AES or coaxial), if I want to use outboard DAC's?

 

[Builder Brad]

Shinobiwan + Ewildgoose,

Thankyou for the pointers!

I think that a good start point with my system will be to try DRC first! Siegfried Linkwitz has already invested considerable knowledge and time in the design of the Orion and its ASP. It is very unlikely that I will just copy the Orions ASP functions and end up with a digital XO that works as well, even working would be nice 1st time, it just does not work like that.

I can see the sense in measuring the Orions performance without the reflections produced indoors. I think that this would be the best start point in order to take full advantage of all that DRC has to offer, especially on a speaker like the Orion.

One of the advantages of a dipole design results from the coupling of the sound waves that are reflected by the rear and to an extent side walls with the forward initial signal. By initially measuring the Orions frequency response “in a field” will allow the DRC applications to accurately create filters based on the Orions effect and response in my living room.

I understand that some of the room effects may occur as a result of chosen XO frequencies and slopes, and digital XO solutions allow for easy adjustment for this, however I believe that the Orions ASP has been designed to minimize these effects.


Ewildgoose

I have downloaded and tried to run the various rec_imp.exe files on the WIKI site without success. I am using win2000 with a Creative Audigy sound card. When I run any of the .exe files I see the .dos command prompt window for a few seconds and then … nothing. Tried to look to see if a rec.pcm file was created and found nothing

Shinobiwan.

I would seriously consider using the pro RME soundcard. Would the standard card allow me to take the 2 ch digital output from the Squeezebox, apply the room correction filters, and output either digital or analogue?

 

[exipnos]

The author of the DRC software believes that his correction is sufficiently good that it can correct for the problems in the LR crossovers you use, meaning that he doesn't think it's worth playing with digital crossovers... So DRC alone should be a high bar to beat..

Good luck

Ed W

I'd agree that Brad should probably just try DRC to start off with and forget about the XO part for the time being. Its a subtle improvement in comparison to a competant analogue active design - which surely the orion is? DRC offers an immediate improvement with relatively little hassle and expense, the XO on the other hand requires considerably more determination, experience and time.

A newbie question. Reading the above posts I see that DRC can remove the need of digital crossovers. I wonder if I understand this correctly.

Say I'm building a 2 way speaker and I have no crossovers. Can DRC splitt the signal so that woofer and tweeter can play in their optimal range?

Or are we saying that using DRC with speakers with existing analogue crossovers, will give you the same gain as if you implemented digital crossover and DRC.

Help me get this straight.

Exipnos

 

[ShinOBIWAN]

A newbie question. Reading the above posts I see that DRC can remove the need of digital crossovers. I wonder if I understand this correctly.

I must stress that DRC does not in anyway surplant XO filters in loudspeakers of any variety. All DRC does is help to reduce the room/speaker interaction it does not ensure your tweeter isn't playing a 20hz bass tone for example!

Say I'm building a 2 way speaker and I have no crossovers. Can DRC splitt the signal so that woofer and tweeter can play in their optimal range?

I think your confusing DRC and the crossover. Both are completely seperate entities. DRC is optional but the crossover cetainly isn't on multiway speakers.

Think of DRC as a treatment to the audio of an already compentantly designed speaker.

Or are we saying that using DRC with speakers with existing analogue crossovers, will give you the same gain as if you implemented digital crossover and DRC.

You absolutely do not need to implement linear phase digital crossover's to hear the benefits of DRC. It stands alone and doesn't rely on any particular type of XO technology in order to sound its best.

 

[ShinOBIWAN]

I can see the sense in measuring the Orions performance without the reflections produced indoors. I think that this would be the best start point in order to take full advantage of all that DRC has to offer, especially on a speaker like the Orion.

One of the advantages of a dipole design results from the coupling of the sound waves that are reflected by the rear and to an extent side walls with the forward initial signal. By initially measuring the Orions frequency response “in a field” will allow the DRC applications to accurately create filters based on the Orions effect and response in my living room.

You don't need to measure the speaker at all if your doing just DRC. The need for critical and less room bound measurements is only a requirement if your creating a crossover.

So all you need to do is get an impulse response of your room, pass it through DRC and then use the outputted filters in a convolver.

I would seriously consider using the pro RME soundcard. Would the standard card allow me to take the 2 ch digital output from the Squeezebox, apply the room correction filters, and output either digital or analogue?

The RME HDSP9632 for example will take spdif both coax and optical. It also supports ADAT if needed.
So yes it will do what your asking without the need for expansion boards.

 

[ewildgoose]

Shinobiwan,

Can I ask you to let me give some simplified explanations here without jumping to the assumption that I don't know what I am talking about...?

To clear up some confusion:

Ideally you want a point source which emits a full range of sounds from very low freq up to higher than we can hear. Up to now it has not been possible to create such a speaker driver and instead we need to use multiple physical drive units.

So most modern speakers consist of several drivers, each of which cover some freq range. A "crossover" is the term used for some gadget to split the initial audio into multiple freq bands and redirect them to just the driver which can deal with those audio bands. Crossovers are always a compromise though and cause "distortion" to the sound - you can pick your distortion though and optimise the crossovers to the problem in hand.

Also there are problems introduced by using multiple drivers which are not exactly the same location in space. Consider that the distance from the woofer to your ear is usually longer than from the tweeter to your ear. At certain bounce angles sideways from the speaker though the path length will be the other way around (consider what happens with the ceiling). This means that the sound from one driver tends to re-enforce and sometimes cancel from each driver - this is referred to as comb filtering and hence people often prefer to have steep crossovers to minimise this effect (but steeper crossovers cause other distortion and you have to have a tradeoff)

Eventually you end up with a design for a full range speaker and have at least two of them, one left and one right (plus extra ones sometimes).

Now DRC is a technology to measure the speaker in a room and see all the problems the room causes (plus residual problems in the speaker). You can kind of apply an overlay of error correction to *the whole speaker* which cancels out some of the effects due to the system as a whole (eg reflections off sidewalls and imperfections in crossovers). It doesn't take a genius to see that it's only possible to do this perfectly in an infinitely narrow area (fancy having your head nailed in position?). However, all is not lost because there is still quite a lot of improvement possible if you correct less of the sound and then the correction is useful over a wider area (everything is a tradeoff - make sense?)

So DRC corrects only the whole speaker and room as a single system and needs a measurement which is taken *in-room*. You should previously have built the best speaker possible and optimised your room to remove as many possible problems first (there are limits on what you can do with DRC and it's a bandaid, not a cure - fix the things traditionally as far as you can and use DRC to get to the next level)

However, that is understating the effectiveness of DRC. Consider that fixing room problems around 40Hz using traditional room treatments means loosing perhaps 1.5m to fibreglass batting around the entire room... Usually quite impractical. On the other hand we can digitally *improve* things quite easily.


Does that help understand the difference between designing XO and then subsequently doing a global DRC fix on the end package?


OK, to use my impulse recording app you first need to realise that it's a command line tool. You need to be on the command line and run the commands as given in the documentation. It does NOT have a GUI (yet)

You run the command as given and it might melt your speakers if the volume is too high, but if it's just right then you should get a nice impulse response out. Please heed this warning and keep the sweeps short while you get the levels correct and don't have the volume more than comfortably loud when you take the measurements or you really do risk melting the tweeters (usually this is not as expensive an operation to replace as it might sound, but it's embarasing)

OK, go get 'em tigers...

(So who want to write this up on the wiki for everyone benefit?)

 

[ShinOBIWAN]

Shinobiwan,

Can I ask you to let me give some simplified explanations here without jumping to the assumption that I don't know what I am talking about...?

I was extrapolating on certain points though to save confusion later on. But hey, what do I know...

The thread is all yours maestro.

 

[Builder Brad]

Shinobiwan,

I have ordered the RME soundcard as recomended. I really dont think that the creative Audigy card in my PC is up to the job - I dont even have speakers on this PC. I have a 250gb slave HDD that is full of FLAC audio files that work with my Squeezebox but that is currently as far as I got with PC audio.

Initially I will fit the RME soundcard in a spare Dell PC from my office which is 1.5, maybe 2Ghz and see how I get along. I am happy to build another PC to use in my living room if the benefits of DRC are great enough. i wonder if its possible to find applications that could run on Damn Small Linux, or even Linux. that way I could get away with a lower spec PC that will require less cooling ect ect.

My Orions are currently positioned about 12 inches from the rear walls and 20" from the side walls and the Thor subs are very near the corners of the room. The recomended positioning for the Orions is a minimum of 36" from the rear walls and 24" from the side walls. These speakers sound great but improve significantly when they are moved out into the room, things get even better when I move the subs closer to the Orions, unfortunately my wife does not agree. I am hoping that DRC will allow me to obtain similar performance from the Orions when they are close to the rear walls to that obtained when I move them out into the room. I am interested to see what it possible when the speakers are in their optimum position.

In one of your first posts you recommended a software package called Console, is this still the best way forward with what I am trying to do?

You also mentioned that you were not happy with the clocking speed of the RME card, how did this affect you and how much of an improvement was realized by adding the WorldClock module?

I have recently sold off all of my high end surround sound kit because the Orions were so good compared to £+++ THX ultra spec kit, I just found myself preferring movie soundtracks in stereo which seemed to capture the ambiance better that surround sound. From what I understand of DRC so far I may be able to utilise some equalized low cost rear effect speakers and awesome surround sound!

 

[ewildgoose]

I have ordered the RME soundcard as recomended. I really dont think that the creative Audigy card in my PC is up to the job - I dont even have speakers on this PC. I have a 250gb slave HDD that is full of FLAC audio files that work with my Squeezebox but that is currently as far as I got with PC audio.

Your question was not directed to me, but: the Audigy card is actually not bad. It has a flaw (I think) in that it prefers to output at 48Khz and I think this is one of those cards which if you try and output at 44Khz will do some horrible resampling (which foils the impulse response measurement amongst other things)

I think if you stick to 48Khz and use a decent resampler that you will be quite happy with the Audigy, at least for testing purposes

Please experiment before shelling out too much on hardware. I dont know how well the "DRC" software by Denis will work for you with your dipoles close to the walls - it *may* be that it tries too hard to "correct" for the rear reflection... Certainly some people have had good results though. Also you can use other software to do a DRC style process and improve your setup no matter whether "DRC" (the program) works for you or not.

Ed

 

[geofstro]

Shin,

Thanks for your advice. I'm back from my skiing trip now and will download the console program and experiment with it, along with the free linear phase eq program next weekend.

My crossover requirements are very simple since I've chosen speakers which are crossoverless single driver designs. Of course, no driver can cover the full frequency range. My Lowther DX4's in the Rethm 2nd cabinet does a pretty good job though. Driven by the Nelson Pass First Watt amp it reaches down to between 50-60hz.

I'm interested in your approach to creating XO's between these speakers and my Magellan True Bass VPI active Sub.

For DRC I'll think I'll stick to Denis' DRC program, since I've been very happy with the results. I'll need to redo DRC once I've got the crossover working to my liking. I'll probably wait until I've aquired the RME Fireface before doing that. I may also try to hire a higher quality mic than the Behreinger, if it makes so much difference.

Ed,

You were asking for feedback from anyone who's used DRC on horns. Well I've used it on both the Rethms and a pair of Horn Shoppe horns which I have in my office/apartment. I can only provide a subjective opinion since I didn't carry out any measurements other than making sure I was hitting between 85 and 90db with my SPL meter and checking that the resulting impulse response had what looked to be the right sort of shape within Cool Edit.

My first attempt was actually with a pair of old ProAc Super towers. These are a three way design with a metal dome tweeter in the D'apollito configuration. I had mixed results here. I could hear that DRC was allowing more detail through. At the same tiime though I had some ringing effects and what sounded to me like phase anomolies.

I followed the intructions to the letter in the Jones Rush guide, so I don't know what went wrong there. Perhaps it was the limitations of the Audigy 2 sound card I was using at the time.

Next I tried correcting my Horn Shoppe horns. I actually used the PowerWave which is a USB digital amp/sound card. I used it with my laptop and the Behringer mic and preamp. The results were surprisingly good. It is a difficult room which is overly warm with a tendency to muddy the sound overall whereas at the same time the presence of a lot of glass in the room tends to harden certain sounds.

All of these tendencies were ameliorated to a great extent with DRC, transforming this system into the most enjoyable I'd ever heard in that room. At the same time the speakers disappeared as separate sound sources.

My next attempt was with the Rethms in a much larger and much livelier room. This was after upgrading to an EMU 1212m sound card. The Rethms are not strictly speaking Horns. Their cabinet is a sort of hybrid of Horn loading and transmission line, aimed to squeeze as full a range out of the Lowther DX4 as possible. As I mentioned earlier the First Watt amp assists further in this reagard. This is easily detectable when swapping the First Watt with a digital amp.

The effect of DRC was a little more subtle than with the Horn Shoppe horns in the other room. Still highly beneficial though. I think it is because the Rethms have far more room to breath and the room does not have as many problems as the one where the Horn Shoppe horns are used.

Again, though the Rethms do a better job of disappearing and the soundstage is enlarged in all dimensions. I can also hear more detail and an overall smoother sound. In this system though, it is apparent that dynamics have been slightly compressed compared with not using DRC. The music can sometimes seem a little more exciting without DRC. This could however be due to the fact that the liveliniess of the room is nor being tamed without DRC.

In all these cases I have no other form of room treatment other than the carpets and other furniture that happens to be in the rooms which, of course, all have some effect.

I will probably redo the DRC on the Rethms, if I can get a better crossover between them and the subwoofer using the methods outlined here.

Geoff

 

[seppstefano]

... with a laptop?

Hi all,
a dummy question from a newbye who just ended reading the whole thread... pant, pant...

Is there a practical solution towards a laptop based solution? I'd expect to get less noise (both electrical and physical)...

Besides I have a pre-power amp system using RCA levels (around 2.0V)

I'd like:

first) to get DRC correction on my existent speakers;
second) to get DRC and active X-over for future 3 way speakers.

Are the RME cards fine with a laptop (guess yes with cardbus interface)? Is this cardbus system supported by Linux?

Any news on the Fireface 800?? (on Linux, I mean)

Thanks for sharing,

Stefano

 

[ewildgoose]

I *think* the RME cardbus is supported on linux, better double check on the ALSA web site though under the Hardware table. The cheapo option is surely the PCMCIA Audigy card which is apparently pretty good as long as you run it at 48Khz.

The Fireface is not supported under linux and RME have refused to hand out the technical details to do so. See their NNTP group for a heated discussion about this, but as far as I can see they feel that they are the only people who have figured out how to *properly* do audio over firewire and are not prepared to release that information to competitors. Seems a shame that they won't at least release a binary driver though. Perhaps in 3-5 years timescale we will see this, but I doubt anytime soon

 

[Builder Brad]

Ewildgoose,

cheers for the info on the Audigy soundcard. I have set the command prompt string to 48khz and have managed to run the sweep app.

I tried using a Senheser microphone initially but kept getting reports that the mic input was too low - I guess that tihis is the wrong type of mike as it rejects most background sounds and is designed for someone to sing into it!

Got to get another mike - do you know if there is a kit around for a DIY quality sampling mike?

Also I wondered if it was possible to batch process a large quantity of FLAC audio files with the in room DRC filters, this way I would not need to run a PC in the living room.

 

[geofstro]

Builder Brad,

You can use Foobar 2k's diskwriter to convert the Flacs. You have to make sure DSP functions are turned on within Diskwriters preferences for the conversion, and that Foobars Convolver with your impulse response file is an active DSP using DSP manager.

From memory this does mean you have to actually convert them from one format to another, e.g. Flac to WAV, so you would lose the compression advantage of Flac. I think you would have to convert them back to Flac again (with DSP inactive this time) if you wanted the room corrected versions compressed again.

You could also burn standard CD's with the room corrected WAVS; but this would mean the CD's would become invalid if you ever changed anything in your room or moved location and had to redo DRC.

Hope it helps

Geoff

 

[seppstefano]

I *think* the RME cardbus is supported on linux, better double check on the ALSA web site though under the Hardware table. The cheapo option is surely the PCMCIA Audigy card which is apparently pretty good as long as you run it at 48Khz.

The Fireface is not supported under linux and RME have refused to hand out the technical details to do so. See their NNTP group for a heated discussion about this, but as far as I can see they feel that they are the only people who have figured out how to *properly* do audio over firewire and are not prepared to release that information to competitors. Seems a shame that they won't at least release a binary driver though. Perhaps in 3-5 years timescale we will see this, but I doubt anytime soon

Ciao Ed,
many thanks for your feedback. Would you eventually point me to some resource on having a usb sound card (Swissonic, already bought and working under MS, basically to listen to DVD through my laptop) working on linux?

Thanks a lot again,

Stefano