Sherbourn PT-7000 & 7/2100 Review

As you know the Sherbourn and Outlaw processors are virtually identical. Audioholics has just posted an interesting review of the Sherbourn PT-7000 & 7/2100 combo.


http://www.audioholics.com/productreviews/avhardware/SherbournPT700072100.html

Interesting, he also notes the 180 deg phase shift that *some* of us have spotted between the analog and digital crossovers.

But ...



This surprises me in that I specifically asked about this, maybe 3 to 4 months ago here in this forum, and Scott said that each set of speakers was high and low passed with the specific freq setting for that set of speakers. (No global low pass to the sub.)

The only thing I can say in Outlaw's defense, if that is correct, is that I have tried to measure freq response using the sweeps on Avia as well, and it's a lost cause. This is a much better way:

http://www.etfacoustic.com/

In general, it's easy to see he did a more thorough review than most HT mags, and in spite of the issues he found, he still liked it a lot.


[This message has been edited by Kevin C Brown (edited June 09, 2003).]

Kevin;

Lets think about this for the moment;
If Mains set to small fc = 40Hz
Center set to small, fc = 80Hz
Rears set to small, fc =160Hz

The subwoofer has to receive one of the three fc's above. Theoretically, it should receive the highest fc to eliminate any bass gaps between the speakers.

I really don't think multiple crossover settings for each speaker is a good idea and I agree with the review in doing so, try to keep them within 20Hz of each other, if not all set equal.

I definately do not agree.

With your example, the *correct* way to do it is this (keeping the slopes in mind):

Mains set to small, fc = 40Hz: main info above 40 Hz goes to the mains. Main's info below 40 Hz goes to the sub.

Center set to small, fc = 80Hz: center info above 80 Hz goes to the center channel. Center info below 80 Hz goes to the sub.

Rears set to small, fc =160Hz: rear info above 160 Hz goes to the rears. Rear info below 160 Hz goes to the sub.

That is the way it should be done, and that is the way the Sony TA-E9000ES did it, and that is the way that we were told the 950 did it. (Lexicons also do it correctly, but a little differently, especially with the newer MC-8 and MC-12.) But based on that dude's review, the 950 would send all main, center and rear info below 40 Hz (the main xover) to the sub. Hence, leaving gaps for the center and rears.

No reason why multiple (individual) low passes cannot be applied to each *signal* before they are combined with the LFE and sent to the sub.

[This message has been edited by Kevin C Brown (edited June 11, 2003).]

Kevin: I agree with your description of the desirable way for the LFE crossovers to work. However, I am unsure if you are stating that the 950 does or doesn't work this way.

That's how I thought the 950 worked based on a question that Scott answered once. (When I get some free time, I'll try to find the exact thread.)

But based on the review, the author is saying that the low pass freq for the mains is the low pass freq that is also applied to the center and surrounds/rears for the info that is sent to the sub.

The early reviews said the Outlaw Model 950 will be the first surround sound product to feature Cirrus Logic's "triple Crossover" circuit. By now, do we know whether many products in aiddtion to Outlaw and their clones, use Cirrus's triple crossover circuit?

Thanks!

Kevin;


From what you are saying, you imply the sub will then be crossed over at 160Hz which is exactly opposite of what Audioholics.com has reported. I know a friend who has the Sony processor that you mention and if memory serves it correctly sets the sub crossover to the highest setting that you choose for your speakers. The Outlaw/Sherbourn, seems fixed on whatever the mains are set to, according to the review at Audioholics.com.

No, that is not what I said. This is what I said:



I don't think you are understanding what I wrote. The way that it is supposed to work, is that each channel is low passed at a different freq, *then* each of those "parts" is added to the LFE signal and sent to the sub. Each of the high passed part of each signal is sent to the respective channel.

You understand that a crossover is two parts, right? A high passed filter and a low pass filter? All of the info above the high pass freq for that channel is sent to that channel's main speaker (left front, center, whatever). All of the info below the low pass freq for that channel is sent to the sub, added to the dedicated LFE channel. The high pass and low pass freqs are typically the same. But in the 950's case, according to the review, they aren't, leaving gaps in the response.

Let's try again for the rears:



This is how it's supposed to work. The problem is that according to the review, the rears are actually low passed at 40 Hz to the sub, but high passed at 160 Hz to the surrounds & rears. So because the high pass is 160 & the low pass is 40, from 40 to 160 Hz is missing.

Make sense?

BTW, the Sony's individual crossovers work correctly. But it can be confusing, because in addition to the crossover for each "set" of speakers, the TA-E9000ES also has a *separate* crossover (low pass) setting specifically for the LFE signal, apart from the info crossed over (low passed) from the main channels.


[This message has been edited by Kevin C Brown (edited June 13, 2003).]

Okay, so where is Scott to help sort this out? A lot of questions could be stopped if Outlaw addressed this. Yes I know that in another thread this was discussed a while back but did Outlaw actually test there triple crossovers? This is like the e-prom issue all over again, deficiencies in the design are being discovered by users and testers. I am glad I spent $899 for the Outlaw vs their clones, and that Outlaw's customer support is first rate. Still, I would like to know how to actually set my crossovers. If we really are missing certain frequencies because our mains are set lower than our surrounds then this defeats one of the main reasons I selected the 950 in the first place.

I am anxious to hear from Scott about this issue.

Kevin, is it possible that, using your example, the information under 160 Hz from the mains is first sent to the main L/R pair, to be crossed over by the settings of the L/R? Then the information wouldn't be lost, but in the L/R mains? That would be an elegant solution IMO, particularly for those of us with tower main L/R speakers. These higher midbass frequencies are better off produced in the main L/R pair anyway, at least IMO. That would be nice.

------------------
Philip Hamm

[This message has been edited by Philip Hamm (edited June 13, 2003).]

I may be imagining things, but I think Scott did address this issue a few months ago in a post here. I thought he said that it works like you'd expect, with the crossovers in the above example sending frequencies above 160Hz to the surrounds, and below 160Hz to the sub, with no hole.

Like I said, I could be deranged from that pitcher of margaritas last night and remembering wrong............

Was it this thread?

http://ubb.outlawaudio.com/ubb/Forum15/HTML/000771.html

JM99- You rock! That's it!

Philip- You should work for Lexicon. That is exactly how the MC-8 and MC-12 work.

(Except that for Lexicon, it uses *the lowest freq high passed main channel as the global low pass filter for the sub*. Doesn't have to be the mains. Although it probably would be in most systems.)

Maybe that *is* how the 950 works...

I have an H/K 525 with the tripple crossover. H/K recommends that you set the sub low pass to the highest level between the three high pass settings FWIW.

So from what I can tell, this would cause a "doubling" of freqs between the lowests of the high pass settings and the highest.

I have just set everything to 60 cycles.

We all know what the manual says, we all read what Scott replied in the above stated thread, BUT does it ACTUALLY do this! The manual tells us how to use the DTS ES but the 950 did not actually function properly until someone noticed a LFE issue, hence the inconvience of the e-prom upgrade. So now a reviewer believes the triple crossover does not funtion as stated. So which is it? Has Outlaw tested this triple crossover system to make sure it ACTUALLY does what it states it's suppose to do? Still waiting for Scott to address this again after this doubt has been cast.

Hello Outlaws,

We have seen all of the comments in this thread, and while it is our general policy not to interfere, some comments are in order.

First, while we have the highest respect for reviewers, there are times where the methodology they employ in testing produces results that do not provide a full picture of how a product operates. Secondly, just to maintain our own sanity, we asked our engineering team to validate the operation of the crossovers, and they reported that everything does work as it is supposed to.

Let's use a configuration scenario to help explain how the triple cross-over
function works.

Settings:

All speakers set to small. (A Large setting by-passes the cross-over
function for that speaker)

Front: 40Hz
Center: 80Hz
Surrounds: 100Hz
Sub: ON

In this configuration the sub will see the entire LFE or ".1" signal. It
will also receive any signal below 40Hz from the front speakers, any signal
below 80Hz from the center channel and any signal below 100Hz from the
surrounds.

Regards,

Scott