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-   -   CHR 70A Gen3 Dual Driver for Pensil (http://www.diyaudio.com/forums/markaudio/249666-chr-70a-gen3-dual-driver-pensil.html)

JoeyGS 21st January 2014 03:37 AM

CHR 70A Gen3 Dual Driver for Pensil
 
Hi,

I plan to have a Pensil cabinet using dual CHR70A Gen3 drivers. I need help to direct me where I can find the Pensil plans with 2 CHR70A drivers as I need the dimensions where to exactly locate the drivers.

I will also try bi-amping the drivers or wiring them in series or parallel.

Thanks in advance for your help.

Regards,
JoeyGS

planet10 21st January 2014 04:52 AM

For a Pensil70R twin driver derivative, double the column's cross-section and double the area of the terminus.

If the drivers are on different faces, centre the drivers at Zd, if on the same face, mount as close as faesible such that Zd is midway between the drivers.

dave

JoeyGS 21st January 2014 06:49 AM

Thanks for your response Dave.

Yes I am using the Pensil R70.3 plans. Sorry am not too familiar with the the other terminologies as I am still starting in speaker building.

What is:
column's cross-section
terminus
Zd

I am placing the drivers on both faces. I am maintaining the distance of the top driver from the top of the box as per Pensil R70.3.

Appreciate your help.....

Regards,
JoeyGS

JoeyGS 21st January 2014 07:28 AM

I got the Zd which is 7.125" from the top of the box to the center of the driver (for single driver)

So is it not feasible just to maintain the Pensil R70 baffle dimension with single driver and just add another single driver below the top driver?

planet10 21st January 2014 05:53 PM

Quote:

Originally Posted by JoeyGS (Post 3786714)
So is it not feasible just to maintain the Pensil R70 baffle dimension with single driver and just add another single driver below the top driver?

You willlikely choke off the bass if you do not double the cross-section (WxD).

If you place both drivers on the front, then the average distance of the drivers from the closed end needs to be Zd.

Teminus is the slot at the bottom front.

dave

zman01 21st January 2014 06:07 PM

JoeyGS,

You can check out the Wessex MLTL at Dave's frugal-phile.com website - it's a design for Twin CHR-70. Drivers can be mounted on the narrow side also, making the speaker narrow and deep instead of wide and relatively shallow.

If a bigger cabinet agrees with you, there is the Mercia which should have a bit more low end oomph.

chrisb 21st January 2014 07:44 PM

and don't overlook the Castle microtower!

JoeyGS 22nd January 2014 03:54 AM

Dave,

Thanks for the clarification.

Just saw Mark's thread:

http://www.diyaudio.com/forums/marka...asurments.html

..and thought that the R70.3 plans may work as-is and just add another driver......

Regards,
Joey


Quote:

Originally Posted by planet10 (Post 3787367)
You willlikely choke off the bass if you do not double the cross-section (WxD).

If you place both drivers on the front, then the average distance of the drivers from the closed end needs to be Zd.

Teminus is the slot at the bottom front.

dave


JoeyGS 22nd January 2014 04:44 AM

Thanks zman01 and chrisb:)

chrisb 22nd January 2014 07:46 AM

Joey - the microtowers were designed from the outset (by the same team as Pensils) with dual drivers in the calculus, so no modification to plans should be required.

I've built a total of 3 pairs, including two variants of the Castles. They certainly have a different soundstage presentation than the Pensils - even I imagine in dual driver configuration.


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