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Re: Low Pass [message #91191 is a reply to message #91187] Mon, 18 November 2019 10:45 Go to previous messageGo to next message
Rusty is currently offline  Rusty
Messages: 330
Registered: May 2018
Location: Kansas City Missouri
Grand Master
Thanks for the heads up on the brand you've tried. I see they have one just for subwoofers. On sale @ bestbuy now. This can eliminate a lot of hard wire headache. Hopefully, if ground loops become evident with wall warts and all the myriad connections, that can be sorted out. Least I'll know the source.
Re: Low Pass [message #91193 is a reply to message #91156] Mon, 18 November 2019 14:11 Go to previous messageGo to next message
Barryso is currently offline  Barryso
Messages: 91
Registered: May 2009
Viscount
Wayne Parham wrote on Sun, 17 November 2019 19:39

And I wonder about Barry, who started this thread. His problems were mostly impedance-matching and lossy inline filters. How's it going there, Barry? Did you find a solution that worked for you?
Hi Wayne,

Even without the fmods there are still impedance issues but very minor. If you attach the cable to the sub amps (without turning the subs on) there is still a change in the sound. A tad less bass or a tad less volume? Don't know exactly what's happening but it's a bit less good with the extra wires attached. Of course when you turn on the subs it's clearly an improvement so it's not really an issue, just an observation.

The mono plate amp doesn't really sound as good as the crown but it still works nicely at lower, more traditional sub crossover frequencies like 60 hz. With the mono subs up front (crossed low) and the REL in the rear the 4's just sound great. The subs add texture to the bass and clear up the midrange beautifully.

I'm still bouncing around researching the crossover solutions. There are too many poor reviews of everything out on the net. And when you read the writings of 10 different audiophiles you get 12 different opinions.

Smile

One question regarding the amp with the bass control at 100 hz. A stand alone 2nd order 100 hz low pass filter should cut output above 100 hz so that by 150 hz the output is down by 6 db and by 200 hz the output should be down 12 db. Easy. But below 100 hz it wouldn't change output. So in a perfect situation you'd see a flat line from way down low to 100 hz and at that point the output would go down as the frequency goes up.

But a 2nd order bass control on an amp would boost the frequencies at 100 hz and then fall off at 12 db in both directions. So the output would be reduced at 150 and 200 hz as it would with a stand alone crossover but wouldn't the bass control on the amp also cut the output below 100 hz on a 12 db slope, too? So at 50 hz there would be a significant reduction in bass?

Rusty,

A friend uses a wireless connection for his rear sub and it works fine. No idea the make/model but it's never seemed to be an issue in a system that always seems to have something not working properly. The wireless unit has been flawless. It seems you have a solution already but if you want to know what he's using just let me know.
Re: Low Pass [message #91195 is a reply to message #91193] Mon, 18 November 2019 15:07 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 17694
Registered: January 2001
Illuminati (33rd Degree)

A midrange tone control is a bandpass filter, but bass is low-pass and treble is high-pass. Boost is sometimes done using a bandpass filter, sort of like a parametric filter. And of course graphic equalizers use a series of bandpass filters.

But the low-pass filter in the bass tone control provides curves that look something like the chart shown below. It's not exactly right, because the slope in this chart changes with amplitude. But you get the idea.

/forum/index.php?t=getfile&id=2470&private=0
Re: Low Pass [message #91196 is a reply to message #91156] Mon, 18 November 2019 16:15 Go to previous messageGo to next message
Barryso is currently offline  Barryso
Messages: 91
Registered: May 2009
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"but bass is low-pass and treble is high-pass"

OK, got it. It now makes sense.

Thanks.
Re: Low Pass [message #91206 is a reply to message #91193] Tue, 19 November 2019 11:26 Go to previous messageGo to next message
Rusty is currently offline  Rusty
Messages: 330
Registered: May 2018
Location: Kansas City Missouri
Grand Master
Quote:
Mon, 18 November 2019 14:11
Barryso

Rusty,

A friend uses a wireless connection for his rear sub and it works fine. No idea the make/model but it's never seemed to be an issue in a system that always seems to have something not working properly. The wireless unit has been flawless. It seems you have a solution already but if you want to know what he's using just let me know.
Sure Barry. Better to have as much information and choices as possible. This subwoofer project of mine will be, (if I ever get going on cabinet building), a long term project. I've had on hand for more than a decade, a JBL sub 1500 driver that I procured in a buyout sale on Parts Express. It's fully vetted over on the Lansing Heritage site. Any who, now I've bought some flanking subwoofers that I'm wrestling with implementation with a 12 db crossover like you are. I'm going to try out this Rolls crossover unit powered by a amp I have on hand. Learning of a reliable bluetooth connection to use the JBL as a distributive sub with a plate amp seems now to give me some more impetus to finally get this thing going. Just need to do the sawdust part. Thanks for sharing your experience.
Re: Low Pass [message #91218 is a reply to message #91156] Wed, 20 November 2019 08:19 Go to previous messageGo to next message
Barryso is currently offline  Barryso
Messages: 91
Registered: May 2009
Viscount
Hi Rusty,

Using four subs is the gold standard but I've been making due with 3 for a while. That 3rd sub in the rear makes a big difference compared to just having the 2 up front. You'll have great luck with the JBL in the rear of your room. The rear sub adds a bit more texture to the bass and really opens up the midrange. A real jaw dropper.

Here is the link for the transmitter. I apologize for not realizing ahead of time he'd pick a pricey solution. He's using JL subs so he went with a JL wireless device.
https://www.crutchfield.com/S-gH8UTY0nXNi/p_136TRX/JL-Audio-JLINK-TRX-High-Fidelity-Audio-Transmitter-Receiver-Kit.html?XVINQ=GLX&awkw=165289662985&awat=pla&awnw=g&awcr=86915025745&awdv=c&awug=9003887&gclid=EAIaIQobChMIwKKfxtT35QIVBaSzCh1JaQ55EAQYBCABEgJKufD_BwE

It's a lot more expensive than the Best Buy gear. He's had no issues with the JL transmitter but he has had many recurring issues with the JL sub amplifiers. He's swapping one of them out every 6 months or so and then months later he has to do another one. It never ends. All the amps have been replaced at least once, one of the subs is on amp number 3. I'm leery of recommending them even though the company replaces them for the cost of shipping.

When you get some time on it please post about your experiences with the Rolls crossover. I'm looking forward to hearing how it works in your setup.

Barry

Re: Low Pass [message #91219 is a reply to message #91218] Wed, 20 November 2019 09:23 Go to previous messageGo to next message
Rusty is currently offline  Rusty
Messages: 330
Registered: May 2018
Location: Kansas City Missouri
Grand Master
Thanks Barry. Whew. Yeah that JL gear is a might bit out of my price range. But thanks anyway. Keeping my fingers crossed regarding the plate amp I have. It's a PE amp. What I'm glad to hear is your description of the benefits you've experienced with this multi sub set up. I've been very curious about it for some time. As we all probably experience is a question of space to accommodate these not too diminutive boxes within our living space. Plus, as you have found out, implementation.
Re: Low Pass [message #91404 is a reply to message #91156] Sun, 02 February 2020 07:22 Go to previous messageGo to next message
Barryso is currently offline  Barryso
Messages: 91
Registered: May 2009
Viscount
Rusty, did you ever get a chance to play with the Rolls crossover?

I've ended up with a quasi minidsp-type fix.

The solution was hiding in an upstairs closet. A DBX Driverack PA was originally purchased 15 or 20 years back to try room correction but I wasn't happy with the results. It was being run full range and seemed to rob a lot of the magic from the tube system at the time. It went into the "sell it" pile and I hadn't thought of the thing in years.

Pulled the Driverack out of exile and added a volume control and a Texas Instruments TPA3255 class d amp. The TI amp is far superior to the old plate amp and the front subs are now in stereo. The bass is cleaner and now has far better texture. I was hoping the sonic shortcomings of the Driverack wouldn't be an issue if it was just being used for the low frequencies and it seems quite fine doing just that.

"Best" settings are still a work in progress but it's sounding great.
Re: Low Pass [message #91405 is a reply to message #91404] Sun, 02 February 2020 07:27 Go to previous messageGo to next message
Barryso is currently offline  Barryso
Messages: 91
Registered: May 2009
Viscount
A couple more sub oddities.

The first oddity is regarding the Amp Camp Amp. The amp reverses phase, which isn't all that odd, but it reverses the speaker outputs inside the amp. It's red speaker terminals are really ground and the black is really positive. This allows you to hookup your postitive speaker wire to the amp positive as if everything was normal.

Long one short, I'd forgotten about the phase and hooked up the REL positive leads to what is really the amplifiers negative terminals.

#$%^!

No wonder it didn't sound right. Changed the connections so the sub positive is now actually on the amps positive terminals (which are the black ones!).

Another oddity:

Came across an article regarding REL subs that clearly states they don't work with a class d amp in the same way they'd work with a class a or a/b amp. Evidently there's still some potential on the class d amp ground and it will create issues with the REL plate amp.

REL recommends using the subs two positive leads normally, as you would on any other amp, but getting ground from an RCA cable coming out of your preamp and running that lead into an RCA input on the sub plate amp. No idea if the added ground potential effects the sonics but evidently it's bad for the plate amp.

Anyway, the TI amp is now running the subs so it's not connected to the REL. But it's worth mentioning as it's a common issue with REL subs now that class d amps are getting popular.
Re: Low Pass [message #91407 is a reply to message #91405] Sun, 02 February 2020 10:44 Go to previous messageGo to previous message
Rusty is currently offline  Rusty
Messages: 330
Registered: May 2018
Location: Kansas City Missouri
Grand Master
I'm curious Barry regarding this Amp Camp amp. Looking briefly online I get the notion it's a class A, low watt stereo amplifier? So I'm confused if your saying it's used on your subwoofer(s). But I'm glad to read your getting use out of a re purposed piece of audio gear with your DBX device. Thus, with that you can achieve the 12 db crossover for the flanking subs? My project is stymied with the cold weather. My table saw is garage bound. And with no heat out there in the midwest winter. My initiative is frozen like the ground.
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