To Biamp or not to Biamp, that is the question???????

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GRollins said:
Why not try the SOZ for the high frequencies and the Audio Note for the low frequencies?

Grey

Well, I believe that the Audio Note is better (very indeed) than the SOZ in the midrange and High frequencies, and the SOZ is much better in the low frequencies.

I think that valve amps are not very good in bass, but are great in midrange.

PedroPO
 
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Joined 2002
Hi Bill,

You can't have a 1st order slope on a satellite speaker,...

With all due respect, I would have to disagree with this statement. I have found, after years of listening to my system, that a 1st order high pass rolloff works the best for me. I have dual JBL LE10A's in a sealed box for the mid-bass. They have an f3 in the box of about 65Hz and I have an active 1st order high pass filter at 100Hz. The active lowpass for the subs rolloff at 18db/octave at 80Hz. This arrangment works great.

Even if the crossover frequency is 2 x F3 of the satellite, it still won't happen.

I'm don't think I understand this statement. What is it that "...won't happen"?

Rodd Yamashita
 
Steve,

I thing an Apogee loudspeaker is the worst thing for a power amplifier.
I remember when i bought my Divas in 1990 i was using a pair of Rowland Model 7's. What a wonderful sound for the first 30 minutes! After that the amps collapsed. There was nothing wrong with them. They just couldn't drive the Divas at full power in a 70sqm living room.
So i sold the Rowlands and built 4 monoblocks based on the design of the ML2 but with a healthy 120W@8ohm and capable of driving <1ohm (each amp has a 3KVA transformer, 20x10kuf Sprague 36DE electrolytics, Semikron SKKD 46/08 semipacks, 16 pairs of MJ15003-MJ15004 and weighs about 70 Kgrs). The results in passive biamp mode were beyond imagination. I don't know about the sound of Grands or Studio Grands but i think the Divas are among the best full range bipolars ever made.
In 1995 i bought my first video projector and then i realized i needed subwoofers to avoid tearing apart the bass ribbons of the Divas.
I started listening to various high-end active subs of the 15-18-inch variety but the results were disappointing when listening to music.
I decided to build my own. After a brief search i bought a pair of JBL 2235 soft suspension 15-inch drivers. I use them in 100lt vented enclosures tuned at 30Hz and the balance between LF power and transient attack sounds perfect.
I built one more pair of amps (the same 70 kgrs beasts) to drive them and an active crossover with tubes (active 18db/oct for the low pass and passive 6db/oct for the high pass). It has 2 Alps Black Beauty pots for continuous frequency setting of both filters and a Sfernice metal film pot for LF level attenuation (the JBL's are at least 10db more sensitive than the Divas).
The sound of the combination has to be heard to be believed.
Everything is there in full glory, cannon shots in Verdi's Othello, organ pedals in Saint Saens' organ symphony, contrabasses in Dvorak's 8th symphony, Donner's thunder in Wagner's Rheingold etc.
I think you should do the same with the Studio Grands.
Use a good 2-way active crossover and drive the woofers with a separate pair of amps. For the ribbons go for passive biamping.
Good luck.

Nick
 
roddyama said:
Hi Bill,



With all due respect, I would have to disagree with this statement. I have found, after years of listening to my system, that a 1st order high pass rolloff works the best for me. I have dual JBL LE10A's in a sealed box for the mid-bass. They have an f3 in the box of about 65Hz and I have an active 1st order high pass filter at 100Hz. The active lowpass for the subs rolloff at 18db/octave at 80Hz. This arrangment works great.



I'm don't think I understand this statement. What is it that "...won't happen"?

Rodd Yamashita

You may have ADDED a 1st order, 100Hz high pass filter to your LE10 but the fact remains that somewhere around 65Hz the system is starting to roll off the low frequencies at a rate of 18db/o.

You may be satisfied with what you have but I'll bet if you did it right you would even be happier.

By "it still won't happen", I mean that it won't be right.
 
Exactly. That is why an electronic crossover providing a 2nd order high pass at the sealed satellites F3 and a 4th order lowpass at the same frequency is such a good deal.

The same summed response of a LR 4th order network is now happening acoustically. I don't know what else anyone could ask for. It baffles me that this whole question has not previously been laid to rest. From a theoretical standpoint this is pretty much of a no brainer. The hard part is when someone pipes up and speaks on the evils of op-amps. To this I say, "do it discretely" if you wish.

Bury this debate and move on.
 
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Joined 2002
Hi Bill,

I believe you're taking a rather idealistic view of this issue.

That is to say it is certainly possible to achive a true 4th order LR high pass roll off by summing the response of the active filter and freq response of the driver(s) in the bass region, if you have control over most of the system parameters. That is what a good product engineer might shoot for in designing a sat/sub type system. But the average DIY'er usually has to live with what they have to work with. Even if you start from the point of driver selection and crafting your own boxes, there's no guarantee your going achive the perfect B2 alignment or Qt of .707 or .5 or what ever the original goal may have been. Chances are very good that the results will be different then the original goal if your goal was a mathematical ideal.

There are other, practical factors that must be considered as a DIY'er. Factor like what are your available active xover frequencies? You might not get within 15% of your satelites f3. What are the available filter alignments? How good of a woodworker are you? How far are the finished sats from the original concept? That is just scratching the surface of the number of obsticles an average DIY'er will face on just this issue, not to mention the other 1001 other issue they'll have to contend with. But therein lies the beauty of being a DIY'er

I've been working the same tri-amp system for 25 years. There are only a few components left from my original system. But I've had a Heathkit electronic xover from the start. It allows me selectable xover frequencies and slopes from 1st to 3rd order in the high and lowpass sections. Through 4 different livingrooms, 2 different sub drivers, and 3 different mid-bass configurations, the system always sounded the best with a 1st order highpass and a 3rd order lowpass with a sligh gap in their xover frequencies.

I currently use a Bryston 4BST for the LE10A's. I would rather try to optimize the mid-bass speakers transient response then worry about a little (very little) IM distortion in a mid-bass amp like the Bryston.

There is no single "best way", particularly in the DIY realm. The debate is half the fun.

To keep from being to far off topic, I'm building an Aleph 3/5 for my horns above 1200Hz. I should probably build a Zen, but it hurts to think about the electric bills.

Rodd Yamashita
 
But real DIYers DO have control over the system parameters and they don't need to work with what they have. What they ought to do is get what they need. I assume that were not talking here about someone trying to get a system together with a mid range they picked up at a flea market.

As far as the low frequency driver in a SEALED satellite system is concerned all you have do is pick a driver (plenty of recommendations over in the speaker forum), stick it in a box that gives you a Q of .7, find the resonance peak and there you have F3 within 2%. You don't overly rely on published parameters because they vary. You run your own impedance curve and derive the values. OK, so that part's nailed down and it's very, very simple.

Can't run an impedance curve because you lack the equipment? Not to worry, the money you can save by building your own electonic crossover will more than pay for a AC Millivolt meter and audio oscillator which are plentiful on ebay.

And, because this entire forum is DIY based, you hunker down and build your own crossover. A single op-amp, a few caps and resistors (power supply taken for granted) makes a 2nd order high pass filter. Two more op amps, more resistors and caps and you have a 4th order low pass filter. You don't need a multi-section pot to vary the frequency because the frequency is already selected. We're talking $35 worth of parts here. And you don't have to even run a curve because the formulas are very accurate. Add a buffer or two and some way to vary the low freqency output. Construct this on a perf board or a PC board and there you have it. Like I say, it's a no brainer.

To get this far you don't need to be a good woodworker, the room is not an issue and the woofer is not an issue.

I disagree about the debate being half the fun. It's a waste of time. The pleasure comes from doing it right, saving a ton of money and listening to the results.

As to your system. With the info you provided it's clear you have not actually tried my recommendation.
 
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Joined 2002
I work for a German company, so I'm very familiar with the opinion that there is only one solution to a given problem and only a single ridgid path to that solution. I don't agree with it, but I do agree with the right to be of that opinion. Although, it does take the fun out of the debate.

Rodd Yamashita
 
I think the best way is biamping but only with active crossover. You have a lot of playing room and it doesnt cost nothing to swap resistors in and out. To do that with a passive crossover you need a fortune.
Plus its very hard to change Q or phase with passives.
I want to work up slowly to making an Aleph3 for my tweeters after finishing my Aleph5 but to do so I need an active crossover. I really want to see the passdiy crossover but its taking so long.
sigh.......
Maybe someone knows when its coming out......?
 
Buy or build?

Light my path pls..

Do you guys buy or build your crossovers?

Active or Passive?

I'm trying to biamp, but the only thing I have is the 2 amps, preamp, speakers and source.

After reading this thread I FOUND that you shouldn't use the crossover in the speakers...(':D')


Guess we are allways learning..

Pedro Oliveira
 
When you bi amp you can use also the crossovers in your speakers.
With biamping you can feed each speaker with its own crossover. That also works but I dont see the advantage of it if you dont use active crossovers before the amps. Of course in this case you don´t use the crossovers in the speakers.
 
To Biamp or not, that is the question???

Rod and Bill,

I understand exactly where you are coming from with respect to diy crossovers and parameters.

In the commercial version of my system, a now obsolete JBL Pro monitor 2245, the crossover can be rigged for either active or passive operation from the 1st crossover point of 280 herts.

Prior to obtaining the JBL schematic for the crsoover I spent an eternity scewing arround trying to optimise the woofer/mid crossover for 2nd order passive operation until I realised my values were way out by 40 % because I was not aware of the effect of various interactions with the drivers and crossover values.

The point is active operation makes this easier.

I also had to re tune the boxes also to vented 9 cu ft with JBL the 2245 18" woofers tuned to 28hz for an F3 of 32 Hzwith a total Qts' of about 0.285, which takes into account the box losses and DCR of the crossover chokes which are about 5.4mh.

I would like to see a decent active crossover (ie J fet design) but until then I 'm sticking with the passive.

Since this pic I have replaced the mid cone with a JBL 2212 10 Mid driver which weighs 15 lb.

regards

macka
 

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Steve, Pedro,

Since you're both new to the multi-amp system scene, here a suggestion for you to think about.

You can routinely find Rane electronic xovers on eBay. If you stick with the Rane AC22 (2way stereo) or AC23 (3way stereo), you can win the bidding anywhere from $100 to $200 depending on condition, etc. The Rane xover has a wealth of adjustments. It has adjustments for separate hi and lo xover points, slopes, and level. It even has an adjustable time delay for fixing speaker offsets.

You can pick one up and setup your system and then decide whether you want to build one from a kit, or from scratch, or wait for Mr. Pass' new xover. You might decide to go back to a passive. Whatever you decide, when your done with the Rane, you sell it on eBay (maybe for a profit), or you can keep it for your next project. There was even an article in the Audio Xpress on how to spruce up the sound of an AC22 to us in you main system.

Whatever you decide to do, enjoy

Rodd Yamashita
 
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