Rythmik FV15HP 10hz Test - AVS Forum
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post #1 of 24 Old 12-23-2013, 07:09 AM - Thread Starter
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In the ULF thread, there was discussion here on whether or not the FV15HP could dig down to 10hz without making horrible sounds or audible distortion. So I did a test in my room to see how my dual FV15HPs would fare. This test was only the FVs, my FTW21s were turned off...

 

This is the response of the 10hz sine wave. The Max SPL (omnimic) for this was 115.8db. The mic was 1.5ft away from one FV, and 3ft away from the other FV.

 

Below is the video:

 

Note: The sound you hear is the door pulsating from the pressure in the room. There was no port chuffing or mechanical distress that I could hear.

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post #2 of 24 Old 12-23-2013, 07:21 AM
 
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Was this a one port, or two port open test? And according to what I see on the graph, the pair of FV15HPs was able to get a usable 7Hz?
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post #3 of 24 Old 12-23-2013, 07:22 AM - Thread Starter
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Quote:
Originally Posted by BeeMan458 View Post

Was this a one port, or two port open test? And according to what I see on the graph, the pair of FV15HPs was able to get a usable 7Hz?

1 port mode.

 

This is a 10hz sine wave, so don't look at extension at all from the frequency response.

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post #4 of 24 Old 12-23-2013, 07:25 AM
 
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With regard to your ULF score, with one port open, how should one expectedly characterize the output of a pair of FV15HPs at 10Hz?
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post #5 of 24 Old 12-23-2013, 07:26 AM - Thread Starter
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Here is the response of my room with the Dual FV15HPs and Dual FTW21s.

 

If I turn off the FTW21s, here is what the FV15HPs response looks like:

 

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post #6 of 24 Old 12-23-2013, 07:30 AM
 
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Thanks. I want door number one, please. eek.gif...tongue.gif

In a couple of weeks, after we get more break-in hours on the new FV15HPs, I'll do a rerun of Anti-Mode and Audyssey XT and do some REW measurements to see how the subs are integrating into the acoustics of our living room.

(from your posted graph, I see a pair of FV15HPs are capable of a usable 9Hz. Am I correctly reading your graph?)

(currently, the next expected add to the Home Theater system will be a Denon AVR 4520ci with XT32)
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post #7 of 24 Old 12-23-2013, 07:32 AM - Thread Starter
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Quote:
Originally Posted by BeeMan458 View Post

With regard to your ULF score, with one port open, how should one expectedly characterize the output of a pair of FV15HPs at 10Hz?

You should not. The ULF score is based on groundplane CEA2010 max burst testing (and estimates). The FV15HP did not achieve a clean test at 10hz.

 

This goes for all subs: just because low extension is not rated in the ULF score, doesn't mean you can't get clean extension in-room below that. That will depend on your room and the design of the sub.

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post #8 of 24 Old 12-23-2013, 07:48 AM
 
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Originally Posted by dominguez1 View Post

You should not.

Got it. Failed the CEA2010 max burst test and did not get a clean test at 10Hz. BeeMan commences to sob inconsolably. tongue.gif

(that's the last time I let our subs pee in a bottle)

...tongue.gif
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post #9 of 24 Old 12-23-2013, 09:14 AM
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Ummm... from Rythmik's site:
Quote:
Please note:

The warranty does not cover abuse, nor incorrect installation. Abuse includes continuously playing sine wave and other test tones for an extended period. A duty cycle greater than 25% is considered abuse, where the test tone plays for 15 seconds followed by a break of 45 seconds.

You need to be careful when you play stuff like sine waves, especially at such a low frequency. Nothing heats up the VC faster or puts as much strain on the moving parts as a low frequency sine wave.
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post #10 of 24 Old 12-23-2013, 09:19 AM - Thread Starter
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Good warning shady. Thx.

I took one for the team... smile.gif
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post #11 of 24 Old 12-23-2013, 09:23 AM
 
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Well poo. Here I was, ready to do something stupid. tongue.gif

Next time I'm hiring a PA so I have somebody else to blame besides myself.

...tongue.gif
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post #12 of 24 Old 12-23-2013, 12:16 PM
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1/2 Touche is definately in order....and I give you full props for testing. My challenge pretty specifically said MLP, and while 1.5feet away may be MLP for some - it isn't for most, and wasn't the idea behind my statement.

However --- I'm very impressed that even nearfield the FV15HP pair weren't violently port chuffing at 10hz and 115dB.

THANK YOU for testing!

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post #13 of 24 Old 12-23-2013, 01:26 PM
 
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My public touché is at the ready...
Quote:
Originally Posted by Archaea View Post

1/2 Touche is definately in order....and I give you full props for testing.

Only half a "touche?" All and all, based on the first quote, I do recall you being willing to give a full touche.

(we both know that a half touche, meets the definition of being tight)

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post #14 of 24 Old 12-23-2013, 01:26 PM
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Was that door rattling when you did the measurement? Could that have thrown off the measurements?
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post #15 of 24 Old 12-23-2013, 02:57 PM
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^^ very good point and thanks Dom so much for testing for the team. Can't believe the pair can do that at 10hz even near field smile.gif
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post #16 of 24 Old 12-23-2013, 03:40 PM
 
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Originally Posted by Cowboys View Post

^^ very good point and thanks Dom so much for testing for the team. Can't believe the pair can do that at 10hz even near field smile.gif

Not only that but two of them, drop harmonic distortion down considerably. Makes one want to add a third FV15HP.........today.

(Dallas won....Seattle lost......Monday Night Football in a couple of hours)

(Romo's back out for the season)

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post #17 of 24 Old 12-23-2013, 06:58 PM - Thread Starter
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Quote:
Originally Posted by Archaea View Post

1/2 Touche is definately in order....and I give you full props for testing. My challenge pretty specifically said MLP, and while 1.5feet away may be MLP for some - it isn't for most, and wasn't the idea behind my statement.

However --- I'm very impressed that even nearfield the FV15HP pair weren't violently port chuffing at 10hz and 115dB.

THANK YOU for testing!

To be honest...I wouldn't believe it either if I hadn't tested it myself. :cool:

 

One thing to keep in mind when measuring nearfield, it more closely resembles an anechoic response (think close mic testing) as you are essentially removing room gain from the equation. How much room gain is removed depends on the distance of mic to sub, proximity to boundaries, etc.

 

In large rooms with little room gain, you might expect that a neafield measurement might have the most output. However, in rooms like mine where there is a lot of gain, it's probably one of the worst positions to measure if you striving for max output in-room. Measuring further away from the subs would factor more room gain into the equation for rooms like mine.

 

I didn't test the farfield response at 10hz compared to my nearfield measurement, but I did test it at 15hz.

 

This response was from a 15hz sine wave with the mic nearfield (~3ft away from each sub), and the main volume at -25db or so. This produced a Max SPL of 96.6db.

 

This was the response of the same 15hz sine wave taken 10ft away from the pair of FV15HPs, at the same main volume as the 96.6db measurement above. This produced a Max SPL of 105.8db.

 

Given that the main volume did not change, and only the distance, the extra ~9db or so can be attributed to room gain. Also note how the distortion changes...no visible harmonic distortion on the frequency response.

 

If I were to perform the same test with the 10hz signal 10ft away, chances are I would get similar results...actually perhaps even more as there is an additional half octave to build more gain. :eek: Granted, I could have been in a room mode at 15hz in that position 10ft away, but regardless, I wouldn't be surprised if the output at 10hz is north of 115.8 10ft away. I'd also expect little to no distortion showing up on the response as well, similar to the 15hz test.

 

Quote:
Originally Posted by rcohen View Post

Was that door rattling when you did the measurement? Could that have thrown off the measurements?

Yes, the door was rattling as the 10hz sine wave was causing the room (and door) to pulse. It should not have had any impact on the measurements since the 10hz sine wave was at such a high output. I guess it's possible the door could have produced 10hz sound as it rattled (if that's what you're getting at)...but no where near a significant level to change the response or output.

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post #18 of 24 Old 12-23-2013, 07:28 PM
 
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Originally Posted by dominguez1 View Post

Also note how the distortion changes...no visible harmonic distortion on the frequency response.

Based on your above experience, how hard can one expect to drive a pair of FV15HPs and at 10Hz, not expect to see any harmonic distortion?

At louder volumes, to reduce harmonic distortion, would it be reasonable to expect a third FV15HP would reduce harmonic distortion to negligible?

And if one used XT32 to EQ the acoustics in the room, at reference level output, how much can one expect distortion to be reduced?
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post #19 of 24 Old 12-23-2013, 07:33 PM - Thread Starter
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Quote:
Originally Posted by BeeMan458 View Post


Based on your above experience, how hard can one expect to drive a pair of FV15HPs and at 10Hz, not expect to see any harmonic distortion?

Distortion in-room is very room dependent. It would be hard to say.

 

Regardless of this test, for the general public, I would still say not to expect anything much under 12.5hz. If you get it, it's a free lunch.

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post #20 of 24 Old 12-23-2013, 08:55 PM
 
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Thanks! I'm okay with free lunches. biggrin.gif

How much would XT32 help with harmonic distortion? The reason I ask, our next AVR purchase will have XT32 installed and hopefully, this purchase will be sooner than later.
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post #21 of 24 Old 12-23-2013, 10:42 PM
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Quote:
Originally Posted by dominguez1 View Post

1 port mode.
14/hi setting or...?
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post #22 of 24 Old 12-23-2013, 10:45 PM
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XT32 can help with frequency and phase response, but not distortion. Maybe XT1000 will do distortion.
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post #23 of 24 Old 12-24-2013, 03:40 AM
 
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Maybe XT1000 will do distortion.

That would be kind of Audyssey. tongue.gif
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post #24 of 24 Old 12-24-2013, 07:18 AM - Thread Starter
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Quote:
Originally Posted by Cowboys View Post


14/hi setting or...?

14/low. Limiter on (Auto).

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