[tak1313]

I am looking at options for an SW for my Mag 1.6.  Among the options is building an OB H-frame sub.  The problem I'm having in this research is that I have read here and there that the amp used for the GR OB is a Rythmik amp that is modded to account for the cancellations/response in OB format.

When I look at the site, there is no ready "kit," and it seems like the only option is to buy the drivers and amp individually.  So, my question is, is the PEQ amp that is on the website the same as this "modded" amp, or is there actually no "modded" amp, and just the stock amp used?

While I'm at it, other than the potential cost, is there an ACOUSTIC reason to NOT use two drivers (with two amps) in separate parts of the room (to take advantage of better of room modes)?

Thanks for any input - I don't have regular access @ work, so may not be able to respond right away.

[HAL]

If you purchase the servo sub drivers and servo amps from GR-Research, they have the transform circuit installed when you receive them.

[Danny Richie]

When we order amps from Rythmik we specify what they are for. For the open baffle applications a shelving circuit is added to mirror the roll off of an open baffle application to maintain a linear response.

With the open baffle design power levels needed to drive the woofers are chosen to drive the woofers to their limits but not beyond. So one A370PEQ amp is needed for a pair of woofers in an open baffle. Or the HX300 can also be used on a pair of woofers. Amps must also be used in close proximity to the woofers. Spreading them out from one another can cause a delay in the control function. 

[Guy 13]

A warm welcome to AudioCircle Mr. tak1313

Guy 13

[Early B.]

When we order amps from Rythmik we specify what they are for. For the open baffle applications a shelving circuit is added to mirror the roll off of an open baffle application to maintain a linear response.

How can I confirm if my 370PEQ's contain the shelving circuit?

[Danny Richie]

How can I confirm if my 370PEQ's contain the shelving circuit?

If you ordered it to be used with OB woofers then you have it.

[Odal3]

How sensitive is the shelving circuit to different OB designs (H frame vs  .., size, woofer size, etc) if one seek linear output. Is it optimized for a certain design or does it really not matter that much.

 Can the shelving be done in DSP instead (for example with HAL's system)? And if so, what is the preferred option?

[Danny Richie]

H frame and W frame are the same. The same shelving circuit is used. It's built into the amp. It solves the problem. There is no need to look for other options. It is also built into the feedback system. It compares input to movement and makes adjustments to maintain that linear response.

[HAL]

I am using the HX800 servo amps with the shelving circuits and the work extremely well for me.

[tak1313]

With the open baffle design power levels needed to drive the woofers are chosen to drive the woofers to their limits but not beyond. So one A370PEQ amp is needed for a pair of woofers in an open baffle. Or the HX300 can also be used on a pair of woofers. Amps must also be used in close proximity to the woofers. Spreading them out from one another can cause a delay in the control function.

First, thanks for the welcome Guy13  Second, thanks to all for the input. 

Danny, the second part of my question is more about using TWO amps, each one driving a single OB driver in different parts of the room, rather than trying to drive two drivers, each in different locations with one amp.  Is there a reason why two amps, each driving one driver, in different parts of the room is less optimal?

For example, is the shelving also accounting for some kind of acoustic coupling from the close proximity of the drivers that would not be occuring with separated drivers?

[Captainhemo]

Hey, welcome to AC tak1313 

Depending on your room size, you'll likely have exellent resutlts with a pair of either dual or triple  H-frmames, one on either side of the room runing in stereo. One amp would power  each  pair/trio of drivers, so 2 amps in total as you suggest.

You'll find the OB bass loads the room  much more evenly and you  don't get near the  nulls  in certain locations  in the room.  You do get  nulls to the side of the cabinets so  you can place up against a side wall, but they do need to  face the listener. They should be  3' min off the front wall.

As others mentin above,  these  work extremely well and the shelving circuit keeps them playing flat to 20hz !!

jay

[Danny Richie]

Danny, the second part of my question is more about using TWO amps, each one driving a single OB driver in different parts of the room, rather than trying to drive two drivers, each in different locations with one amp.  Is there a reason why two amps, each driving one driver, in different parts of the room is less optimal?

For example, is the shelving also accounting for some kind of acoustic coupling from the close proximity of the drivers that would not be occuring with separated drivers?

One A370 amp is a little too much power for a single woofer in an OB application. You could go with a single HX300 amp though if you don't get real crazy with them.

If driving a stereo pair in open baffle you already don't have anywhere near the room loading effects that you would have from a non-OB sub.

When using a pair of drivers the servo system sees them as a single driver. So there is nothing different that needs to be changed because of the number of drivers. What they are doing acoustically isn't really part of the equation. It is comparing input with movement and making sure they match all the time.

[bdp24]

First, thanks for the welcome Guy13  Second, thanks to all for the input. 

Danny, the second part of my question is more about using TWO amps, each one driving a single OB driver in different parts of the room, rather than trying to drive two drivers, each in different locations with one amp.  Is there a reason why two amps, each driving one driver, in different parts of the room is less optimal?

For example, is the shelving also accounting for some kind of acoustic coupling from the close proximity of the drivers that would not be occuring with separated drivers?

You really want a pair of woofers per side to get enough output for use with your Maggies in a normal or larger sized room. The only thing you give up with the OB sub (in comparison to a normal sealed or ported sub) is output. When you total the cost of the plate amp, woofers, and H-frame, the cost for a second woofer per side is not that much, and well worth it. And then you won't later have to redo your frames. By the way, go for the 8 ohm version of the woofer rather than the 16, to maximize the amplifier power.

If you can swing a pair of subs, you can try different x/o settings with the Maggies, all the way up to about 280-300Hz. Because the subs keep up with the panels, you're not restricted to the normal 100Hz and down. The higher you x/o, the louder and cleaner your Maggies will play! I'm the guy who has been talking about the sub on Audiogon (if that's where you learned of them), crossing over at 180Hz to my Eminent Technology Magnetic-Planar speakers (in place of the stock 8" woofer). Another tip: if you have balanced XLR outputs on your pre-amp, you can get the plate amp in two different versions featuring balanced inputs on XLR's---nice if you need to use long cables.

[bdp24]

I am looking at options for an SW for my Mag 1.6.  Among the options is building an OB H-frame sub.  The problem I'm having in this research is that I have read here and there that the amp used for the GR OB is a Rythmik amp that is modded to account for the cancellations/response in OB format.

When I look at the site, there is no ready "kit," and it seems like the only option is to buy the drivers and amp individually.  So, my question is, is the PEQ amp that is on the website the same as this "modded" amp, or is there actually no "modded" amp, and just the stock amp used?

While I'm at it, other than the potential cost, is there an ACOUSTIC reason to NOT use two drivers (with two amps) in separate parts of the room (to take advantage of better of room modes)?


Thanks for any input - I don't have regular access @ work, so may not be able to respond right away.

What'd I tell ya, Danny ?! Gotta get the OB Sub Kit listed on the site!

[Danny Richie]

What'd I tell ya, Danny ?! Gotta get the OB Sub Kit listed on the site!

It's on my to do list.