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The parts of my new Altecs

Finally had a good sitdown session with the DCX 2496 all day yesterday.

If you're going to go active, drop the 250 bucks on a 2496 and be done with it. I promise you'll never look at an analog crossover again once you learn and understand full operation of it.

Further if you decide you need more EQ than what's on board(you won't), the DEQ 2496 can be coupled in the digital domain without the need for additional A/D D/A conversion. It's also a great stand alone RTA.
 
bowtie427ss said:
Finally had a good sitdown session with the DCX 2496 all day yesterday.

If you're going to go active, drop the 250 bucks on a 2496 and be done with it. I promise you'll never look at an analog crossover again once you learn and understand full operation of it.

Further if you decide you need more EQ than what's on board(you won't), the DEQ 2496 can be coupled in the digital domain without the need for additional A/D D/A conversion. It's also a great stand alone RTA.
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I will check it out. Thanks :thmbsp:
 
spartanmanor said:
I am now thinking of going with electronic crossovers and bi-amping. Does anyone see a problem with going this route with the current 16ohm horns and 8 ohm woofers? :scratch2:
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You need compensation, i.e., contoured EQ, to tame the 806A mids, but even with that, they will not deliver VHF.

Same's true with BMS, but those WILL deliver. :yes:

bowtie427ss said:
Finally had a good sitdown session with the DCX 2496 all day yesterday.
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Well, now I'm confused. Behringer DCX2496 is the digital crossover, with limited parametric EQ and no RTA, right? DEQ2496 is the digital equalizer with built-in RTA....
 
Zilch said:
You need compensation, i.e., contoured EQ, to tame the 806A mids, but even with that, they will not deliver VHF.

Same's true with BMS, but those WILL deliver. :yes:
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So it is do-able. I will look for an electronic crossover with EQ control.

BTW I just got through reading the 58 page discussion on improving Altec's on the Heritage site, very interesting. I figure with the electronic crossovers I will be able to play with the drivers in these Valencia's. The BMS drivers do sound intriguing and I would like to try them.
 
spartanmanor said:
BTW I just got through reading the 58 page discussion on improving Altec's on the Heritage site, very interesting. I figure with the electronic crossovers I will be able to play with the drivers in these Valencia's. The BMS drivers do sound intriguing and I would like to try them.
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It was a long and tortuous road, no? I particularly like the part where the comparo was a bust because we got the circuit wrong. Ah, science. :p:

There is a parallel thread here on AK, with some additional information:

http://audiokarma.org/forums/showthread.php?t=106759

That's another 10 pages, with a clear-cut conclusion in the current final post:

http://audiokarma.org/forums/showthread.php?p=1152785#post1152785

Those are AK member Jackgiff's measurements on his Valencias, as he also reported in another thread here at AK. Compare to the results I obtained with Srbliss's 846A a couple of days ago:

http://audiokarma.org/forums/showthread.php?p=1467024#post1467024

******

I run bi- and tri-amped here routinely, but only use digital EQ as a design tool to assist in the construction of passive filters to actually do the requisite HFcompensation. That compensation board I showed for 846B is normally in series with the BMS drivers in another system. I need to build up another pair:

http://audiokarma.org/forums/showthread.php?p=1468579#post1468579

Digital equalizers introduce their own signatures and artifacts into the signal path. There are more transparent active analog crossovers allowing response contouring, but that requires construction of custom filter circuits for each driver/horn combination. I have never found their built-in generic HF compensation up to the task. They're designed for sound reinforcement applications, generally, not high fidelity.

Per Theo's request, I'll be reporting more on how the Behringer analog compensation works with Valencia's 806A/811B here soon....
 
Well, now I'm confused. Behringer DCX2496 is the digital crossover, with limited parametric EQ and no RTA, right?
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You're absolutely correct............... sorry for any confusion.

At it's pricepoint the DCX is a very wonderful toy for those who are into active biamping. It's more than a full step beyond a typical analog unit, without mentioning any of the additional onboard functions, it offers amazing tuneability just by virute of the variety of filter types and slopes available.

IMO, the parametric EQ's fall short because of the memory their use sucks up, limiting how many ins or outs you can use them on, but once you become familiar with this thing, you've gotta have a really mismatched buncha stuff to run out of tuneability.

What i find far more useful and impressive in the listening environment is the dynamic EQ.

In all fairness i find the "limits" of the DCX very generous when you consider the pricepoint. It's also my understanding that there are some guys out there doing some pretty radical mods to these things and no doubt a memory upgrade must exist for those who want to use more than whats possible in the stock configuration.
 
RaymondLeggs said:
:sadwave: I dont think I'd EVER buy a set of speakers that big and heavy..
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GIve it a few years.. you're still young... You'll be surprised how once you have the money and the room you'll find a lot of times bigger is better....

Wait until you start stacking PA stuff.. you got the bug young.. it will happen.. :yes:
 
bowtie427ss said:
You're absolutely correct............... sorry for any confusion.

At it's pricepoint the DCX is a very wonderful toy for those who are into active biamping. It's more than a full step beyond a typical analog unit, without mentioning any of the additional onboard functions, it offers amazing tuneability just by virute of the variety of filter types and slopes available.

IMO, the parametric EQ's fall short because of the memory their use sucks up, limiting how many ins or outs you can use them on, but once you become familiar with this thing, you've gotta have a really mismatched buncha stuff to run out of tuneability.

What i find far more useful and impressive in the listening environment is the dynamic EQ.

In all fairness i find the "limits" of the DCX very generous when you consider the pricepoint. It's also my understanding that there are some guys out there doing some pretty radical mods to these things and no doubt a memory upgrade must exist for those who want to use more than whats possible in the stock configuration.
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So you're saying after I decide to buy the Behringer, I can sell my parametric? I'm sure that would be a buying point to let the miss know.. :thmbsp:
 
bowtie427ss said:
IMO, the parametric EQ's fall short because of the memory their use sucks up, limiting how many ins or outs you can use them on, but once you become familiar with this thing, you've gotta have a really mismatched buncha stuff to run out of tuneability.
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The parametric EQ is quite powerful, as you know.

I've never tried working out BMS/811B compensation on the Behringer DCX2496, but if several of us got on the same path here, it might be worth a bit of effort to do that.

There are lots of audio hobbyists using this unit in their systems. As you say, it incorporates amazing versatility for minimal investment.... :yes:
 
So you're saying after I decide to buy the Behringer, I can sell my parametric?
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NO!!!!!!!!

The parametric filters on board weren't really intended to replace a system eq. They're more aimed at dealing with specific tuning as in bringing down a specific peak or filling in a valley in the response of any specific driver/speaker in the system. As Zilch mentions above, useful in adressing the response anomalies of certain drivers, most any driver in fact.

Once the user becomes familiar with accessing the different parameter pages for each input and output channel and how to assign them for their application, it's very quickly accessible for making changes on the fly. Also has a groovy "compare" feature that allows you to compare any new adjustment you have made to the previous settings.

If you don't like the front panel interface you can also completely program and run the DCX from your windows PC.
 
Srbliss Altec 806A Measurements:

1) Windowed MLS (quasi-anechoic) frequency response on Altec 811B horn with and without Behringer CX3400 analog active crossover CD (Compression Driver/Constant Directivity) compensation engaged.

It's a good match, flattening the frequency response and extending it to ~13 - 14 kHz (cursor).

The fundamental frequency response of Steve's 806As is similar to measurement results with other examples previously reported. His driver pair with sequential serial numbers is fairly well matched.

2) Gated SINusoidal frequency response and THD (Total Harmonic Distortion,) which increases disproportionately with the "Boost."

Why's that? VHF is getting up to 10 times the "normal" power with the compensation engaged, +10 dB at 10 kHz and above. Distortion is -30 dB at 90 dB SPL there, which is still within acceptable limts. That's 0.1%, I think. Ray'll tell us, if we ask nicely.

It's also apparent from the THD measurements that a crossover frequency somewhat above 800 Hz may be preferable. I'm now listening crossed at 1.2 kHz.

Bottom line: Biamp using this inexpensive analog active crossover, and you'll achieve a full octave of HF extension plus tamed midrange with the CD compensation engaged. It can also be used three-way to add stereo (or summed mono) subs augmenting the Valencia (and similar) bass response.

20 kHz as with BMS? Forget it; can't happen with these drivers, nope. As observed previously, it'd take 20 dB of boost to get there....

Edit:

3) Compare to the response of Srbliss's 806A drivers with the stock N800-F highpass filter. Clearly, at least insofar as smoothness of frequency response and VHF extension is concerned, the compensated active filter provides considerable improvement.

Can YOU tell which of these two 806A drivers was in Steve's Valencia when we measured it last weekend by comparing the VHF response curves?

http://audiokarma.org/forums/attachment.php?attachmentid=68757&d=1195460008

4) Finally, what happens if the BMS 4550 is substituted using the Behringer CD compensation?

5) BMS 4550 THD.
 

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Why's that? VHF is getting up to 10 times the "normal" power with the compensation engaged, +10 dB at 10 kHz and above. Distortion is -30 dB at 90 dB SPL there, which is still within acceptable limts. That's 0.1%, I think. Ray'll tell us, if we ask nicely.
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So, would you care to speculate if the increase in distortion is being produced by deriving gain from the active device?

Or, is it simply a product of the HF driver receiving more electrical energy at those higher frequencies?

I've always subscribed to the school of thought that netting any kind of signal gain from active devices like crossovers and EQ's was an open invitation to increased distortion, and is best avoided whenever possible.

The consensus among my audio peers has always been "tis better to cut a peak than boost a null".
 
bowtie427ss said:
So, would you care to speculate if the increase in distortion is being produced by deriving gain from the active device?
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Even if you accomplish it with cutting, the net result is likely the same.

Consider a simple case of a stepped HF response where everything above 10 kHz is down 10 db. So, you cut everything below 10 kHz by 10 dB and now it's all flat. BUT, to restore the original output level, you must increase the system gain by 10 dB. Everything below 10 kHz is then running at the original level, but everything above that is now getting 10x the power, the "boost" coming from increased system gain.

Doing it with high-level passive filters, there's no "gain" available, so it's accomplished with contoured midband attenuation. Using compression drivers, there's usually enough excess sensitivity available to accomplish that via frequency-selective attenuation. Net result is the same: the driver gets more power at higher frequencies.

I don't know how the Behringer unit in particular implements the compensation. Clearly there's 10 dB of net differential "gain" at and above 10 kHz, and the contouring equalization provides less and less at lower frequencies down to as low as 1 kHz, from the measurements.

Member Robh3606 and I had this discussion earlier this year in the AK Valencia thread. To some extent, it's semantics, but there are real consequences demanding consideration:

http://audiokarma.org/forums/showthread.php?p=1135983#post1135983

Bottom line, you listen. Geddes would argue you can't hear it, anyway.... :p:
 
I was able to rebuild the fronts of my Valencia's over Thanksgiving. I opted for the original design ported by the tweeters. Next up is building the crossovers.
 

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NICE!!!! Looking really good David... Can't wait to see the finished product...

I sat around yesterday doing a lot of thinking, and I think I've decided I'm gonna use my lone Altec as partial funds for a pair... Pretty hard decision to make..

Part of that decision was I picked up a Behringer MX2004 mixer yesterday on the bay, and to appease the wife, show her I can actually make a few bucks off of buying and selling some stuff, while getting to play with some stuff for a while..

However, part of that decision also came from the fact a matching woofer sold on e-bay for more than I wanted to a guy in Japan, so I figured it would cost too much to find mates.. and then today I see another in better condition starting at $20...

Damn it.. second guessing :scratch2:

SO ANYWAY... How was your holiday? and how was Laura's Bday dinner? Hope all was well...
 
spartanmanor said:
I opted for the original design ported by the tweeters.
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I'm missing something, apparently:

1) How do you propose to tune the system for 416-8C woofers?

2) What crossovers will you build to accommodate the different driver impedances?
 
That's what I was wondering. Why not use the simpler round ports like the 846B's have if you are going to that extreme? The front panel does look nice, though! :thmbsp: Are you going to make the shelf that goes below the horn?
 
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