Measuring Amplifiers - Page 35 - AVS Forum
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post #1021 of 1918 Old 06-02-2008, 07:15 AM
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Quote:
Originally Posted by penngray View Post

Hmmmm....I thought for sure I set the amp to GS (Generic Sub) before sending it too Chuck.

I didnt see Chucks Frequency response chart, was it posted?



No chart. Chuck just posted sample FR numbers in the first line of his test results.


Also, I wonder how long the unit retains its memory settings once power is removed!
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post #1022 of 1918 Old 06-02-2008, 07:16 AM
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[quote=LINEARX;13993248]
Quote:
Originally Posted by penngray View Post

Why do you say that, it does not have a hard SFF

Chucks Frequency response chart shows it down 4db at 15HZ and down 25db at 10Hz.


No no no and no, Bosso cannot use this unit...blasphemy!

Ask yourself mortal , do you have as much displacement as me ? The answer is no unless you have a Windmere fan sub.
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post #1023 of 1918 Old 06-02-2008, 07:25 AM
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Quote:
Originally Posted by J_Palmer_Cass View Post

Chuck's test is kind of invalid. The subsonic filter changes along with each preset.
"

That doesn't necessarily make it invalid, only that it needs additional information which can explain why the FR attenuates below 20Hz.

Chuck, can you explain why the amp's FR is attenuated below 20Hz?

My guess is that all the settings will produce a (driver protective) reduction in FR output below 20Hz.
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post #1024 of 1918 Old 06-02-2008, 07:30 AM
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Also, I wonder how long the unit retains its memory settings once power is removed!

I dont know that one, I have asked Velodyne about reseting all EQing and setting it too Generic sub to have zero filters.

When powering up, I set the amp to GS and then I removed all Filters by pressing the presets on the remote in the following order 1 2 3 4 4 3 2 1. That should have removed all filters and EQ stuff.

I now wonder what the amp is set too for Chuck.

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post #1025 of 1918 Old 06-02-2008, 07:32 AM
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Quote:
Originally Posted by LINEARX View Post

That doesn't necessarily make it invalid, only that it needs additional information which can explain why the FR attenuates below 20Hz.

Chuck, can you explain why the amp's FR is attenuated below 20Hz?

My guess is that all the settings will produce a (driver protective) reduction in FR output below 20Hz.



The original test that Chuck noted here used the SC-12 subwoofer setting.


http://www.hometheaterhifi.com/volum...06-part-3.html


I don't think that it was Chucks intent to measure each and every setting of that amplifier. Still, it would be nice to know what settings were used in testing that unit.
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post #1026 of 1918 Old 06-02-2008, 07:53 AM
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This discussion of the SC-1250 amp by Velodyne is showing it to be quite versatile and if all the presets can be bi passed and the natural FR is flat to say 3Hz or 5Hz, then I grade this amp a 'B-' for DIYers . . . . . or is that gonna get me in some kinda hot water?
Penngray, is that FR plot you posted, after adjustment by the room EQ?
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post #1027 of 1918 Old 06-02-2008, 12:52 PM - Thread Starter
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Quote:
Originally Posted by penngray View Post

Hmmmm....I thought for sure I set the amp to GS (Generic Sub) before sending it too Chuck.

I didnt see Chucks Frequency response chart, was it posted?

Yes, you did set the amp to 'GS' because I checked it when I ran the tests to make sure that it was not set to any other mode. It was set to 'GS'.

No, there was no response chart, just the readings directly off the test gear.

Chuck
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post #1028 of 1918 Old 06-02-2008, 12:56 PM
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Penngray, is that FR plot you posted, after adjustment by the room EQ?

Im not sure what you mean by "after adjustment by room EQ", Its the plot using REW with no EQing at all, is that what you are asking?

The sub is tuned to around 16Hz so the FR plot looks about right above, doesnt it?

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post #1029 of 1918 Old 06-02-2008, 12:57 PM
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No, there was no response chart, just the readings directly off the test gear.

it is interesting that there is a big drop off below 20 Hz I did ask Velodyne about any hard wired SSF and they said that in GS mode there is zero protection and no filters should exist....hmmmm.

For my situation, it doesnt really matter, it will do 16Hz very well and I have buttkickers for sub 16Hz stuff

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post #1030 of 1918 Old 06-02-2008, 01:15 PM - Thread Starter
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Quote:
Originally Posted by LINEARX View Post

That doesn't necessarily make it invalid, only that it needs additional information which can explain why the FR attenuates below 20Hz.

Chuck, can you explain why the amp's FR is attenuated below 20Hz?

My guess is that all the settings will produce a (driver protective) reduction in FR output below 20Hz.

Your guess is correct!

Read this excerpt from the review I posted earlier.
http://www.hometheaterhifi.com/volum...06-part-1.html

"The amplifier is of the switching variety, which means it is very efficient, but more importantly, it runs cool. The subwoofer drivers, although having a DC resistance of 8 ohms, have a reactive impedance higher than that, which means the whole system is practically bulletproof, making it an ideal choice for custom installers who want to put a system in, and not have to come back a bunch of times for repairs"

This amplifier is made for subcontractors that come out and install Turn Key systems in homes for people. It is meant to run and run without ever breaking or requiring adjustment. That is why the very low frequencies are limited and rolled off to protect the subwoofers that these installers will use with this amp. (It also protects the end user form themself also!). If you read the whole review you will see that this amp does what it does very well and it is very versatile.
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post #1031 of 1918 Old 06-02-2008, 01:16 PM
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That is why the very low frequencies are limited and rolled off to protect the subwoofers that these installers will use with this amp. (It also protects the end user form themself also!). If you read the whole review you will see that this amp does what it does very well and it is very versatile.

I wonder why Velodyne told me that in GS mode all filters are off and Im unprotected?

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post #1032 of 1918 Old 06-02-2008, 01:20 PM - Thread Starter
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Quote:
Originally Posted by J_Palmer_Cass View Post

I don't think that it was Chucks intent to measure each and every setting of that amplifier. Still, it would be nice to know what settings were used in testing that unit.

I used the 'GS' setting that supposedly eliminates all filters. I am not sure that it does eliminate all filters because Velodyne does not say much at all about the specifications of the amp.

From the Velodyne website:

Specifications SC-1250 Amplifier:
(Class D) 3000 watts Dynamic
1250 watts RMS Power
High Pass Crossover: 80 Hz (6 dB/octave)
Low Pass Crossover: 30 Hz - 160 Hz, Defeatable, 24 dB/octave slope
Inputs: Line and Speaker Level
Outputs: Line-level, 80 Hz up
Speaker level for up to two subwoofers
Phase: 0°, 90°, 180°, 270°

Not much information on frequency response, distortion, S/N, 8 ohms or 4 ohms, etc.

http://www.velodyne.com/products/pro...9&sid=995u498b
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post #1033 of 1918 Old 06-02-2008, 01:30 PM - Thread Starter
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Quote:
Originally Posted by penngray View Post

I wonder why Velodyne told me that in GS mode all filters are off and Im unprotected?

Because there are no filters from the DSP being utilized in 'GS' mode. The below 20 Hz rolloff is built into the amplifier and cannot be defeated. That is not part of the DSP settings! When they say you are 'unprotected', they mean that there is no limiting as far as voltage is concerned. When you select one of their presets, the amplifier is voltage limited for your protection.

When I measured the frequency response I was concerned about the low frequency rolloff and double checked my equipmet. My equipment will go to 5 Hz with -.01 dB deviation.

Also, remmeber that Velodyne is the company that rolled off their flagship SMS unit at 15 Hz before consumers demanded a firmware update.
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post #1034 of 1918 Old 06-02-2008, 01:38 PM
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Also, remmeber that Velodyne is the company that rolled off their flagship SMS unit at 15 Hz before consumers demanded a firmware update.

yeah, and I actually commented about that asking if the SC-1250 did the same thing.

In my case, I think this is a moot point and probably better that its there, there is no need for my TC2Ks to go below 16Hz anyways and it will save me any possible damage.

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post #1035 of 1918 Old 06-06-2008, 03:17 PM
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regarding the SC1250. is that a surprise that is actually produces what it claims? Why does one channel produce 2X the power of the other?
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post #1036 of 1918 Old 06-06-2008, 03:27 PM
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The left channel is actually the data for the 8ohm test. The right is for the 4ohm test.
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post #1037 of 1918 Old 06-06-2008, 03:33 PM
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Quote:
Originally Posted by penngray View Post

Im not sure what you mean by "after adjustment by room EQ", Its the plot using REW with no EQing at all, is that what you are asking?

The sub is tuned to around 16Hz so the FR plot looks about right above, doesnt it?

I am trying to determine if the dips at 50Hz and 75Hz are the room modes produced by the actual room size measurements IE: 12 X 17 X 8 etc. If your chart has no EQ in the response then I might start to understand these same dips in response charted by others with the same room dimensions.

If your sub is tuned to 16Hz the response curve looks correct however if the response curve of the amp has the same curve then which item is responsible for the charted response curve?
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post #1038 of 1918 Old 06-06-2008, 03:42 PM
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I am trying to determine if the dips at 50Hz and 75Hz are the room modes produced by the actual room size measurements IE: 12 X 17 X 8 etc. If your chart has no EQ in the response then I might start to understand these same dips in response charted by others with the same room dimensions.

If your sub is tuned to 16Hz the response curve looks correct however if the response curve of the amp has the same curve then which item is responsible for the charted response curve?

No EQ at all, I double checked to make sure.

The room is 14x25x8.= and the sub is tuned to 16Hz. I do agree that I can not tell if its my amp creating curve or not but Chuck showed that the SC-1250 has a SFF at around that area so we should assume the SC-1250 has it.

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post #1039 of 1918 Old 06-06-2008, 04:30 PM
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Quote:
Originally Posted by Ricci View Post

The left channel is actually the data for the 8ohm test. The right is for the 4ohm test.

thats kind of what I figured, thanks.
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post #1040 of 1918 Old 06-06-2008, 04:38 PM
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RodH, picked up a 3rd SC-1250 Ebay guy had them for $595 shipped but I grabbed two more SC8s and the SC1250 for $830 shipped!

It is not "open-minded" to reject knowledge - Bob Lee
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post #1041 of 1918 Old 06-06-2008, 06:36 PM
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Originally Posted by penngray View Post

RodH, picked up a 3rd SC-1250 Ebay guy had them for $595 shipped but I grabbed two more SC8s and the SC1250 for $830 shipped!


WOW, you must be impressed. Mine is still in the box. I am doing the veneer and finishing of my sub this weekend.
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post #1042 of 1918 Old 06-06-2008, 07:04 PM
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The amp's response can be measured with REW right?

I'll try to measure my K1

Regards,
Dan
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post #1043 of 1918 Old 06-06-2008, 07:11 PM
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WOW, you must be impressed. Mine is still in the box. I am doing the veneer and finishing of my sub this weekend.

Silent, 1000W, remote control, RCA connections, voltage sensitivity closer to AVRs,Crossover, Auto EQing abilities (I have not tried yet) and they look good in my rack! (I think I have posted this once or twice now )

Its the only amp so far out there that I have found with the above needs and it can be found used for under $600. I really wish more amps like this where built!! Im hoping CraigSub and his new company will create an amp like this (Mark/Craig are you guys listening)?

Plus I actually like the twin SC8s in my office with small bookshelves...they are pretty impressive but very small passive 8" sealed subs too for $100 each.

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post #1044 of 1918 Old 06-06-2008, 11:36 PM
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Originally Posted by penngray View Post

Silent, 1000W, remote control, RCA connections, voltage sensitivity closer to AVRs,Crossover, Auto EQing abilities (I have not tried yet) and they look good in my rack! (I think I have posted this once or twice now )

Ya, that a LOT of the reason I bought it as well. The PEQ was HUGE for me, I just didn't want to buy a pro-audio amp and also get a BFD and have to go through the hassle of having to "correct" the numbers on my RS SPL meter, then go the set up of the BFD, etc....... Auto EQ is really really nice, I also like the fact that you can run a movie mode as well as a music mode (I would think the Music mode would be as flat as possble and move a slight boost at the low end).

A lot of people seem to indicate to me that $1000 was too much for this "Amp", I think what they didn't realize is that, 1. It can be had for under $600, 2. It is an AMP and PEQ in one, 3. It is very very attractive, 4. It is pretty dang adjustable, 5. You also get a remote.

For me it was a NO brainer.

I am sure people can get a comprable pro amp and BFD for slightly less, but the all in one unit, remote, no hassle EQ, etc.....was worth the $100-200 extra that I might have paid.
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post #1045 of 1918 Old 06-07-2008, 05:59 AM
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So, rodH . . . . . what're you using the SC-1250 on? What's your quick subjective opinion of the amp and your sub combination? We don't want to kidnap this thread you know.
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post #1046 of 1918 Old 06-07-2008, 07:16 AM
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Originally Posted by LINEARX View Post

So, rodH . . . . . what're you using the SC-1250 on? What's your quick subjective opinion of the amp and your sub combination? We don't want to kidnap this thread you know.

Project isn't done yet, 1 more week. 2 12" TC1000 sealed.
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post #1047 of 1918 Old 06-07-2008, 07:47 AM
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We don't want to kidnap this thread you know.

We aren't its a measured amp and nothing else is going on someone should fork over some dough and send more amps to chuck. $60 is worth it to get your amps measured!!

I was searching to see if any QSCs have been measured, I might send my QSC 1850HD next and maybe one of my Outlaw monoblocks (its not a sub amp but I really like them and Im curious!)

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post #1048 of 1918 Old 06-07-2008, 08:19 AM
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Yeah, penngray keep Chuck on his testing toes. Send him both of your amps. The QSC and the Outlaw would make a great couple of amp tests for us DIYers to analyze. We need amp stats and more inside the amp pictures.
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post #1049 of 1918 Old 06-07-2008, 08:20 AM
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Im waiting for a new fan to mod my QSC so when Im done and back from a business trip, I will send them both off to Chuck in ONE heavy box

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post #1050 of 1918 Old 06-07-2008, 08:20 AM
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And Chuck, don't think I don't appreciate all of the work you've already done testing amps. You've been great!
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