Sealed Ultimax15 with Crown XLS 1002 - crossover / settings help please

[KEtheredge87]

Hi Everyone,

I'm looking for some help with the crossover settings and general setup of my sealed Ultimax15 in my living room 3.1 home theater setup. The subwoofer / box combo is the Ultimax15 with sealed 3.0 ft^3 box knockdown kit from parts express, stuffed with 3lb of polyfill as recommended. The system setup right now is a Marantz SR6009 receiver with the LFE channel connected to a new Crown XLS 1002 amp. I have the Crown set to high input sensitivity (0.775V) to match the consumer pre-out voltage from the receiver, and have the sub connected as 4 ohm bridged load on the amp to get 1100W. I have the LFE low-pass crossover in the receiver set to 120 Hz, and currently NO additional crossover setup in the crown amplifier (have the option of additional low pass, high pass, or band pass within the Crown itself). The subwoofer has been calibrated in the system by Audyssey using "12-noon" gain settings on the Crown amp, and this resulted in 0 dB of additional gain being added from the receiver's channel level options. The subwoofer is physically located in the corner of my room, which was the best spot available via the "subwoofer crawl" method.

My question is whether I should leave the crown amp as no-crossover ("full range" signal from LFE channel), or add an additional high pass filter to protect the subwoofer? The Crown provides options for high pass with frequencies starting as low as 30Hz... and the F3 = 35Hz for that subwoofer in a sealed setup at 3 ft^3.

I am concerned a bit because I was watching Netflix last night (specifically Wet Hot American Summer - First Day of Camp, episode 4, the scene where toxic sludge starts to expand out of the hole), and ran across some pretty raucus LFE content that I believe made the subwoofer distort. I did not increase the receiver LFE channel level over 0 dB, but the bass dipped into very low frequencies and made a loud flapping sound rather than any controlled bass reproduction.:eek: I assume this was the subwoofer, not my house shattering around me... but it was dark, and I wasn't watching the subwoofer cone to see if anything looked amiss! If I added the high pass filter at 30 Hz on the Crown amp, would that safeguard me against this kind of thing, or would that just rob me of additional bass content that I can safely use otherwise?

Thanks in advance!

[Wolf]

Re: Sealed Ultimax15 with Crown XLS 1002 - crossover / settings help please

If you ask me- 120Hz is too high for your typical HT sub. I've never had one integrate well xover'd above 90Hz, with typical being 70-80Hz.

You don't want to HP the sub in a sealed box as it's not required, and you may miss out on LFE content. Something tells me you should have gone vented and tuned low to get the sub to perform as you require.

Also- the Drivecore amps are digital types, which generally means you lose bitrate when you turn it down. I would reduce the volume on the level setting, and keep the Crown maxed out. You may also want to try the pro-fi level input and max it out instead if you are getting too much for the driver.

Lastly, what is the voltage out from the Marantz rated at that drives the sub? Some receivers run hotter outs than others, and you could be clipping the amp.

Later,
Wolf

[KEtheredge87]

Re: Sealed Ultimax15 with Crown XLS 1002 - crossover / settings help please

If you ask me- 120Hz is too high for your typical HT sub. I've never had one integrate well xover'd above 90Hz, with typical being 70-80Hz.

You don't want to HP the sub in a sealed box as it's not required, and you may miss out on LFE content. Something tells me you should have gone vented and tuned low to get the sub to perform as you require.

Also- the Drivecore amps are digital types, which generally means you lose bitrate when you turn it down. I would reduce the volume on the level setting, and keep the Crown maxed out. You may also want to try the pro-fi level input and max it out instead if you are getting too much for the driver.

Lastly, what is the voltage out from the Marantz rated at that drives the sub? Some receivers run hotter outs than others, and you could be clipping the amp.

Later,
Wolf

Thanks Wolf,

I admit, the 120Hz LFE crossover point was based on a suggestion I read on the Audioholics website. They also recommended 80Hz crossover for my LCR speakers, which I have done so far. I don't have a microphone for measurements, so I'm kinda trusting it right now. Thanks for the advice on not applying an additional HP filter to the sub, I'll avoid doing that. I went with the knockdown sealed box design because it was smaller (I can still see my wife's eye twitch when she sees the big 3 ft^3 box... so going any bigger for the right vented volume was a no-go). I'm also incredibly slow at building things, and just finished those LCR speakers that I started last January, so my time for design and construction of a box was minimal!

On the drivecore amp and receiver thoughts... I don't think I'm clipping the amp. When I was messing around before doing a proper Audyssey setup I had the Marantz's channel level up at max and the crown gain set at 3pm, and high sensitivity mode engaged. All of that was just starting to make the -20dB lights on the crown flicker when playing back at moderate but not ear splitting volumes.

Trying to look at the Vout from the receiver is a bit confusing to me. The Marantz manual says Analog rated output = 1.2V, and Digital "D/A" rated output = 2V (at 0 dB playback). Am I overthinking it here? I was looking for "Preamp Output Voltage" somewhere, but maybe that's one of those two ratings? If so, maybe I don't need the high sensitivity setting engaged on the Crown and should use the Pro-fi 1.4V sensitivity setting... Care to share more knowledge here?

Thanks!

[Wolf]

Re: Sealed Ultimax15 with Crown XLS 1002 - crossover / settings help please

Thanks Wolf,

I admit, the 120Hz LFE crossover point was based on a suggestion I read on the Audioholics website. They also recommended 80Hz crossover for my LCR speakers, which I have done so far. I don't have a microphone for measurements, so I'm kinda trusting it right now. Thanks for the advice on not applying an additional HP filter to the sub, I'll avoid doing that. I went with the knockdown sealed box design because it was smaller (I can still see my wife's eye twitch when she sees the big 3 ft^3 box... so going any bigger for the right vented volume was a no-go). I'm also incredibly slow at building things, and just finished those LCR speakers that I started last January, so my time for design and construction of a box was minimal!

On the drivecore amp and receiver thoughts... I don't think I'm clipping the amp. When I was messing around before doing a proper Audyssey setup I had the Marantz's channel level up at max and the crown gain set at 3pm, and high sensitivity mode engaged. All of that was just starting to make the -20dB lights on the crown flicker when playing back at moderate but not ear splitting volumes.

Trying to look at the Vout from the receiver is a bit confusing to me. The Marantz manual says Analog rated output = 1.2V, and Digital "D/A" rated output = 2V (at 0 dB playback). Am I overthinking it here? I was looking for "Preamp Output Voltage" somewhere, but maybe that's one of those two ratings? If so, maybe I don't need the high sensitivity setting engaged on the Crown and should use the Pro-fi 1.4V sensitivity setting... Care to share more knowledge here?

Thanks!

Since the rated power at load on the Crown is at 1.4Vrms input, and your Marantz puts out 1.2Vrms, you'll be getting pretty close to rated power at the Pro-fi setting. You found the right spec I was interested in knowing. You may be clipping the input stage, and not the output stage at the higher sensitivity setting. I know I've done it on other amps before that were rated at much lower power output. I would leave it on the lower spot, and see what the Crown does full out.

EDIT: You can also increase the slope of the sub's rolloff by setting the Crown amp's LP to the same frequency to make the slopes add. The Crown I think is 12dB/oct, and if our receiver's out is also 12dB/oct, then you have a 4th order slope.
Later,
Wolf

[Blenton]

Re: Sealed Ultimax15 with Crown XLS 1002 - crossover / settings help please

+1 to pretty much everything wolf said. I've never been satisfied with 120hz low pass on the receiver; 70-80hz, as mentioned, has always worked out very well for me. I'm running an XLS 1500 on my SI18 in a vented enclosure with amp gain set abt 3pm. It is absolutely amazing...

[fastbike1]

Re: Sealed Ultimax15 with Crown XLS 1002 - crossover / settings help please

The Crown xls filters are all LR 24.

[trevordj]

Re: Sealed Ultimax15 with Crown XLS 1002 - crossover / settings help please

Another reason not to add a high pass filter is the Crown XLS amplifiers already have a non-defeatable roll off at about 12db/octave starting just above 20hz. Essentially your amplifier already has a 2nd order high pass filter whether you want it or not.

[Face]

Re: Sealed Ultimax15 with Crown XLS 1002 - crossover / settings help please

Another reason not to add a high pass filter is the Crown XLS amplifiers already have a non-defeatable roll off at about 12db/octave starting just above 20hz. Essentially your amplifier already has a 2nd order high pass filter whether you want it or not.

Not so sure about that. http://www.avsforum.com/forum/155-di...l#post33915818

[Wolf]

Re: Sealed Ultimax15 with Crown XLS 1002 - crossover / settings help please

The Crown xls filters are all LR 24.

You are correct. With a receiver at 12dB/oct, that would make the net slope 6th order or 36dB/oct.

Later,
Wolf

[trevordj]

Re: Sealed Ultimax15 with Crown XLS 1002 - crossover / settings help please

Not so sure about that. http://www.avsforum.com/forum/155-di...l#post33915818

The information about the rolloff came directly from Crown. They could be wrong but several others have reiterated the same information. I'm not sure why they would lie about that.

[Blenton]

Re: Sealed Ultimax15 with Crown XLS 1002 - crossover / settings help please

I found this little blurb on Crown's forum. The response was from Kevin Heber, a member of Crown's staff.

It's tough to speculate what happens below 10Hz. For one, my Audio Precision measuring system doesn't go below that. Another problem is that although the amp might pass audio there, at some level, and at some load, the amp will think it has a shorted output and will shut down to protect itself. And we just don't know the exact conditions under which that will occur.

I've seen several folks claim that the XLS amps roll off below 20 hz, but I've yet to see anything from Crown. I'm not saying it isn't true, but I am skeptical about it. I'm wondering if any roll off shown on a graph, for example, is actually just the limits of the measuring equipment.

Forgot to cite the quote: http://www.crownaudio.com/forums/ind...showtopic=3906

[KEtheredge87]

Re: Sealed Ultimax15 with Crown XLS 1002 - crossover / settings help please

Since the rated power at load on the Crown is at 1.4Vrms input, and your Marantz puts out 1.2Vrms, you'll be getting pretty close to rated power at the Pro-fi setting. You found the right spec I was interested in knowing. You may be clipping the input stage, and not the output stage at the higher sensitivity setting. I know I've done it on other amps before that were rated at much lower power output. I would leave it on the lower spot, and see what the Crown does full out.

EDIT: You can also increase the slope of the sub's rolloff by setting the Crown amp's LP to the same frequency to make the slopes add. The Crown I think is 12dB/oct, and if our receiver's out is also 12dB/oct, then you have a 4th order slope.
Later,
Wolf

Wolf, I hadn't considered clipping on the input stage before, but that makes plenty of sense. I had an impatient engineer moment on Tuesday night and decided to re-run Audyssey setup with the crown amplifier set to normal (1.4V) sensitivity. Everything passed Audyssey setup just fine. This time the software chose to set the LFE channel gain set to +5dB this instead of 0dB as it did previously. My crown amplifier gain was/is still set at 12 noon, so I am tempted to crank that gain to 3pm and reduce the pre-amp gains back toward 0dB like you suggested and see if I notice a difference. I've got more reading to do about class D amplifiers, with respect to your comment about amplifier resolution.

As always, thanks for the help!

EDIT: I forgot to mention, I replayed the Netflix scene in question after making these tweaks and did not experience the same awful distorted subwoofer noises. I changed more than one thing at a time with this experiment, so I'm not entirely sure what the difference was... but I am inclined to think it was the differences in high sensitivity vs. normal sensitivity on the crown amp and the input stage clipping that you suggested! Either way, the problem seems to have been tamed until further evidence presents itself.