[HAL]

Here is a question.

Do both A370PEQ amps have the OB correction filter?  Since that is a 6dB/Oct low pass style shelf, it would add to the existing 12dB/Oct filter response, making it about 18dB/Oct over that range.  If one were for sealed subs and the other for OB, that would be the difference. 

[emailtim]

Here is a question.

Do both A370PEQ amps have the OB correction filter?  Since that is a 6dB/Oct low pass style shelf, it would add to the existing 12dB/Oct filter response, making it about 18dB/Oct over that range.  If one were for sealed subs and the other for OB, that would be the difference.

These test measurements are for a single triple-12 OB/Dipole sub, not to introduce stereo sums/cancellations into the mix.

I bought the 370 amp for the 16Ohm 12" OB/Dipole speakers.  It has a board labeled "SW12-16V2" on the back of it which I assume is the OB/Dipole version as requested.

Is there any other way to identify the specific OB/Dipole versus Sealed versions ?

[Danny Richie]

You haven't eliminated your room from the equation. What I see in your room measurements is an unusual amount of gain below 80Hz. Normally the lower range is flat. Here is another one measured in my listening room.



And my room consistently had a bump at 24Hz.

If your response were flattened out down low then your actual -6db down point would be in the 200Hz region.

And that is not a resonance spike that you are getting at 200Hz. That is a room peak.

And there has never been a 25Hz-240Hz control. Numbers printed on the amp are electrical reference points not a -6db down crossing over points. So the actually crossover point is typically much higher than the setting on the knobs.

You can also use the EQ function to pull down the lower end and flatten out your response.

Also, your aren't trying to measure both the left and right channels at the same time are you?

[emailtim]

You haven't eliminated your room from the equation. What I see in your room measurements is an unusual amount of gain below 80Hz. Normally the lower range is flat. Here is another one measured in my listening room.



And my room consistently had a bump at 24Hz.

If your response were flattened out down low then your actual -6db down point would be in the 200Hz region.

And that is not a resonance spike that you are getting at 200Hz. That is a room peak.

And there has never been a 25Hz-240Hz control. Numbers printed on the amp are electrical reference points not a -6db down crossing over points. So the actually crossover point is typically much higher than the setting on the knobs.

You can also use the EQ function to pull down the lower end and flatten out your response.

Also, your aren't trying to measure both the left and right channels at the same time are you?

Only trying to measure 1 channel at a time to eliminate stereo sum/cancelling.  "R" stands for Right in the measurements.

Also get similar behavior when measuring in the garage with 16' ceilings and completely different room dimensions.

I don't get the 200Hz spike from my main dipoles.  Can do further testing on this.

"You can also use the EQ function to pull down the lower end and flatten out your response."

Why would I want to do that when the subs are virtually flat running full range with no DSP ???  Sounds like using DSP to fix DSP.

One thing I didn't point out.  I did not level match the ICE amp and the Servo Amp.  The ICE has no gain other than the main volume control.  The Servo amp is set to @ 12 O'Clock (plus main volume control) so output levels are different in these tests.

[Danny Richie]

What you are getting looks more like a near field response.

Here is a near field response of the output of the 8" open baffle servo subs.



Here is a near field response of the 12" OB servo subs showing differences in damping settings.



Here is a near field response of the 12" OB servo subs showing differences in extension filters.



Note that the rising response in the lower end is necessary to mirror image the roll off that you get with an open baffle. If you move away from the woofer to a listening position then it produces a flat response.

And here is the same measurement on the same woofer with a non-servo amp (green line).



Here is the same near field measurements shows different crossover settings on a sealed box servo sub. Note the the near field is flat and of coarse so is the in room response.



So how far away are you from the woofers?

You also get some gain above 100Hz in the OB configuration.

[emailtim]

...

So how far away are you from the woofers?

You also get some gain above 100Hz in the OB configuration.

Center of H-Frame Subs are 4.5' from the front wall. 
- 4.5' is @ 3/4 wavelength of 200Hz so could explain the peak.

Microphone is facing up with 90 degree calibration file, 9 foot from the center of the subs.
 
Room is 14' 4" wide, 8' ceiling with multiple depths opening in the back to other rooms.

H-Frame has standard 13" x 13" x 6.5" internal cavities with all 1.5" thick frame.

SW low shelf is 8dB 30Hz Q=2 in blue plot.

[mlundy57]

These test measurements are for a single triple-12 OB/Dipole sub, not to introduce stereo sums/cancellations into the mix.

I bought the 370 amp for the 16Ohm 12" OB/Dipole speakers.  It has a board labeled "SW12-16V2" on the back of it which I assume is the OB/Dipole version as requested.

Is there any other way to identify the specific OB/Dipole versus Sealed versions ?

It’s my understanding from Brian that the OB circuits are specific to the driver being used. If you are using different drivers then the amp was originally set up for, you need to contact Brian at Rythmik. He can send you new shelving circuits for the new drivers. They’re easy to change out. I’ve done it before.

[Danny Richie]

It’s my understanding from Brian that the OB circuits are specific to the driver being used. If you are using different drivers then the amp was originally set up for, you need to contact Brian at Rythmik. He can send you new shelving circuits for the new drivers. They’re easy to change out. I’ve done it before.

No, the amps are just specific as to OB or non-OB.

[Danny Richie]

emailtim, you might try a near field measurement like the ones I posted to see if they match mine.

[emailtim]

emailtim, you might try a near field measurement like the ones I posted to see if they match mine.

I can try that to see what it does.  When I previously measured near field in the garage, it was also flat [14-40]Hz. You said you were surprised it was doing that then and it didn't change that behavior moving it into the house at normal distances.

[mlundy57]

No, the amps are just specific as to OB or non-OB.

Awhile back I picked up two A370PEQ amps that had been used with Hawthorn Augies. Brian told me the amps wouldn’t work properly with the GR drivers without some modifications. I don’t remember what all the modifications were but one was to replace a cap.

[Danny Richie]

Awhile back I picked up two A370PEQ amps that had been used with Hawthorn Augies. Brian told me the amps wouldn’t work properly with the GR drivers without some modifications. I don’t remember what all the modifications were but one was to replace a cap.

Those Augies were non-servo. So it might have been a non-servo version of the amp.