I feel another bout of High-enditis coming up

[Robert Schulze Lutum]

I recentlty bought an SACD player and now it's happening:
I am seriously thinking about souping up my Hifi with active speakers and expensive preamps etc.

So before I go completely mad with voodoo cables, magic speaker pucks and so on: Paavo, what is your system at the moment?

Do you believe in active speaker electronics?
Full range horns?
Tube amps?

Are you using of your EQing savvy in your Hifi setup?
I can imagine that Har-Bal technology could come in handy when you are attempting to build speaker crossovers for for active speakers.

Have you thought about this?

Love,

Robert

[HarBal]

Hi Robert,

I'm an engineering pragmatist so my system is probably far from an audiophiles dream and it is aging too. My electronics (except speakers) are all Yamaha of 10 y.o. vintage. I have a CDX750 CD player and an AX300 amplifier.

I also have a 10 band graphic EQ which I generally don't use because the frequency selectivity is not good enough to be of any significant use and my speakers don't need EQ anyhow. It did and does come in handy in trying to figure out problem areas when tweeking speaker designs.

The speakers I have are of my own design. They are a 3 way four driver coupled cavity (band pass) enclosure design. The woofer is entirely enclosed in the cabinet that has two chambers on either side of the driver with one vented. This gives a bandpass response that covers about 1.5 octaves from 45Hz to 120Hz. The woofer is a 6 inch Peerless. The midrange drivers comprise 2 Vifa 5 inch woofer-midrange units which cover from 120Hz up to about 2 kHz. The tweeter is an inexpensive Philips 1" dome that I couldn't better. It just seemed to work exceptionally well with the other drivers. The crossover is passive with a 1st order section at 120Hz and and third order butterworth section at 2kHz. The midrange and tweeter units have impedance equalization networks to make them look resistive to the crossover. Although the crossover is electrically 1'st order at 120Hz, acoustically it is more like 3'rd order owing to the effect of the coupled cavity and the fact that the midrange units are running at a box tuning of around 120Hz. Generally I'm very satisfied with them. I did continuely tweek the padding between the drivers prior to realising that the main reason I needed to do so was more to do with the quality of the recording and not the loudspeakers themselves.

I do have reasonable quality speaker cable but certainly not the voodoo type. It is low resistance OFC but I didn't go overboard. Certainly, good quality cable can help if you have long runs and the speakers have highly reactive impedance. In my case the speakers are laregly purely resistive with the exception of the resonances of the couple cavity at around 45Hz and 120Hz. I don't have voodoo cable for RCA connections. Just the stock standard stuff that came with the equipement.

My listening room is pentagonal (in our new house) which works well although it is too wet because it has no damping in it yet (ie. no rugs, curtains etc). When I fix this up the sound should be pretty damned good. It is pretty damned good now in terms of imaging but the stridency in the mid range tends to make everything sound a little baroque.

Active crossovers can certainly simplify speaker design considerably. You don't need to worry about impedance equalisation for a start, and you can easily use much higher cutoff slopes without much problem in implementing them. You can even use linear phase digital filters if you so desire. But certainly a self contained speaker system with passive crossover is convenient (ie. less stuff to buy / connect and more easily transported).

I have no experience with full range horns so I can't give you much of an opinion. I've never even auditioned a full range horn speaker so I'd rather not offer an opinion.

Tube amps over transistor I don't really have an opinion on. Personally, a well designed transistor amp is something I have no problem with. The only EQing I use in my current set up is the EQing I've applied to a number of commercial CDs in my re-mastering attempts.

I can see that HarBal could well be useful in designing / testing active crossover designs though I haven't tried it. I have thoughts on adding EQ compensation to HarBal though. The idea hear would be to measure the frequency response of your set up and create an inverse compensation response that you can include with HarBal to take your speakers out of the equation (to an extent). It's only an idea at the moment though.

That's pretty much it. I tend to believe that you should spend about 80% of your budget on getting the speakers plus room correct. When you do they'll sound good with almost any electronics driving them. Big problem is most people spend a reasonable amount on speakers but virtually nothing on acoustics and the net result is usually disappointing. But I guess you'd already know that.

Cheers,


Paavo.

[kinetic]

Your idea for adding compensation for a user's room/speaker combination is a great one Paavo. I hope you do pursue that one.

If Robert is still following this thread, whether to buy active speakers depends on what he wants to use them for. If he was talking about hi fi, then as I'm sure you know there are many esoteric combinations that hi fi buffs rave about. I'm over that now, but I do have a pair of Grant 60 watt mono block valve amps that I just love. I used to have one of those Jaycar mosfet kit power amps driving a pair of Tannoy Ardens and that was a great combination. In fact when I had my studio in Sydney thats what we used and it was a great combination in a great control room (for the market we were in). But when I bought these mono blocks I realised the power and the glory of valves! People talk about warmth, but what I noticed most of all was the open-ness and dynamic range. Truly awesome. These days I drive a pair of Rogers Ls7ts with them, but those speakers have a titanium tweeter, which I find too bright/harsh. Maybe a valve pre-amp would be the way to go, but I can't afford one. Currently I'm just using another Jaycar kit preamp which is based on ICs, and that probably isn't helping the sound much!

But for my music and studio room, and this is for Robert again, I use Dynaudio Bm6as. These are really nearfield speakers, even though they do pack a punch but I love them and I'm not alone. They are very detailed and are a great mixing monitor - if it's a bad mix you'll hear it! But of course as you alluded to, the room is so important for any serious listening or monitoring. I started to cringe when Robert started talking about horns - it would have to be a damn good (and probably large) listening environment to support speakers with horns. I knew a studio once that had some Altec or JBL cabinets with horns and the mixes that came out of there had no top end - I wonder why!! (they were just a demo studio, but still).

The other aspect that really interests me, and I'd be interested to know what your thoughts/experiences are on the subject, is time alignment. I had a friend once who was mucking around with time aligning Tannoys and the difference in sound was amazing.

Thanks for version 1.5 which I downloaded today. Haven't had a chance to have a play yet, but I'm just mixing a song now and can't wait to 'HarBalise' it.

You or Robert can contact me at kinetic@optusnet.com.au if you wish

Thanks for a great product

[HarBal]

Your idea for adding compensation for a user's room/speaker combination is a great one Paavo. I hope you do pursue that one.
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The other aspect that really interests me, and I'd be interested to know what your thoughts/experiences are on the subject, is time alignment. I had a friend once who was mucking around with time aligning Tannoys and the difference in sound was amazing.

kinetic,

I'm sure going to add speaker compensation to HarBal at some stage but it'll take a back seat for a while as we try to get this Mac port done.

I haven't done a lot of experimentation with time aligment but it can certainly make a lot of difference to overall performance, more out of phase cancellation problems around the crossover frequency than "pulse coherence" in my opinion.

It seems common for people making there own speakers to assume that the drivers are time aligned so that the theoretical summing or the ouput of their crossover will do what they expect. The fact of the matter is that if you don't pay attention to it in your design then the behaviour around the crossover frequency is not going to be good.

On the other hand I believe you don't need the drivers to be time aligned to get a good sound provided that the crossover has a reasonably good cutoff slope and makes allowances for the phase difference between the drivers at the crossover. Third order butterworth works well for crossovers. I've always found second order problematic because of the impedance looking into the speaker (it makes a big resonant peak in the impedance at the crossover frequency). It really should be equalized and if you going equalize it why not just use a third order filter which has a resistive impedance looking into it.

My feeling is that the most important aspect of a loudspeaker design is have a good uniform polar response. After all, a fair proportion of what you will be hearing is going to be reflecting off walls and the like and if the off axis response of the speaker system is colour then so will what you hear be. For that reason I feel it is critical to have a good cutoff slope in the crossover to avoid interference patterns between the drivers.

I don't think the Duntech approach of linear phase "pulse coherent" speakers using 1st order passive crossovers is a good one for this very reason. It may sound good on axis in dead room but the problem with dead rooms is that they're oppresive to work in. If you really want linear phase "pulse coherent" response then I'd suggest using an active crossover that uses linear phase digital filters to implement the crossover. Then you can get the high cutoff slope required and still maintain pulse coherence. You could even add frequency response compensation for the drivers to make it as even as possible. Not sure what the "state of the art" is in this respect but I think Meridian make active crossover speakers along these lines. This is something I might try in the future if I happen to find some free time.

Paavo.

[kinetic]

Thanks for your interesting response Paavo. I had a friend who asked me to try to sort out his problems in his listening room once. When I got there there were 4(!) of those huge Duntechs (at $25000 a pair back then) - one in each corner. The room was in an upstairs terrace, and the barrister who lived next door (sharing the same wall) threatened legal action when the Batman DVD knocked one of his pictures off his wall. My poor friend couldn't get the sound right - he was driving the speakers with some huge amps (Krell?) and active crossovers. I told him if he was going to continue to use the room sell everything and buy something more fitting for the size. He wasn't very happy!

Keep beavering away at your speakers and HarBal. I look forward to further developments.

[HarBal]

Ok. If you spend that amount of money on speakers of that size and then set about putting them each in one corner of the room you need some education. That must of sounded dreadful. I like your advice though!

Did you mention to him that corners should be avoided cos the corner of the room is the place you put a driver to excite every supportable standing wave mode in your room. The bass must have sounded awful.

Thanks for the words of encouragement!

Paavo.

[Guest]

Thank you Paavo!