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-   -   El70 in Pensil? (http://www.diyaudio.com/forums/full-range/173299-el70-pensil.html)

type 9th September 2010 08:57 PM

El70 in Pensil?
 
Will the EL70 work in the Chr70 Pensil design or will it have to be modified?

planet10 9th September 2010 09:01 PM

Probably needs some modification.

dave

type 10th September 2010 03:25 AM

Quote:

Originally Posted by planet10 (Post 2298097)
Probably needs some modification.

dave

Would it just be a matter of damping or will the dimensions be off?

planet10 10th September 2010 03:36 AM

Let's see what Scott has to say.

dave

Scottmoose 10th September 2010 08:35 AM

I'm not doing a Pencil for the EL, but of the existing enclosures, the CHP cabinet will be the most flexible.

type 11th September 2010 01:50 AM

Quote:

Originally Posted by Scottmoose (Post 2298487)
I'm not doing a Pencil for the EL, but of the existing enclosures, the CHP cabinet will be the most flexible.

Ok, thanks Scott. May I ask why not one specifically for the EL70 since they are sister products to the MA drivers?

Also, how would it change the sound if the driver was placed closer to the top of the cabinet? Is there a reason that the driver is placed lower?

Scottmoose 11th September 2010 07:26 AM

Because I designed the Pencils for Mark's range.

Don't do it. You'll screw the alignment up.

GM 11th September 2010 04:10 PM

Quote:

Originally Posted by type (Post 2299315)
Ok, May I ask why not one specifically for the EL70 since they are sister products to the MA drivers?

Also, how would it change the sound if the driver was placed closer to the top of the cabinet? Is there a reason that the driver is placed lower?

If you 'run the numbers' for a T/S max flat vented alignment of these two drivers, you'll see that the EL70 wants to 'feel' a stiffer air mass 'spring' supporting it (smaller cab tuned higher), so while you could put it in the Pensil, it will need more damping in the form of stuffing, but due to the nature of things this will not only yield a different roll off slope, but acoustically mass load the driver enough to alter its mids/lower treble response to one of a perceived 'dullness'.

This is the problem I had when loading them into an existing MLTL of similar dimensions as the Pensil except with a 2" ducted vent that over-damped them somewhat, consequently overemphasizing the driver's inherent sibilance up in its break-up modes BW, something I can't tolerate in any speaker since it painfully changes the pitch of my tinitus.

By the same token, others hearing and/or playback system may be such that this is beneficial, so as always when someone wants to use a driver other than the one a speaker was designed for it boils down to whether they are willing to gamble some time/materials building at least one prototype to see if it can be made to work or a complete new design is required.

High aspect ratio vented cabs once long enough will have closed pipe 1/4WL resonance modes that affect driver loading, so if the driver is at the closed end it will get the maximum loading, ergo the widest resonant BW. Usually a good choice for a (sub)woofer app where its resonant HF BW will be rolled off with an XO, but not so much for a wide BW one since it means more BW to damp.

Moving the driver down the pipe then equates to less damping required if the right spot is found. This point varies based on the pipe's dimensions, so refer to MJK's Classic TL Alignment Tables doc for close enough calculated solutions.

GM

Scottmoose 11th September 2010 04:43 PM

Ouch. I can feel that (re the tinitus). :eek:

The EL in the CHP box will likely need about 3/4lb of dacron evenly distributed through the box (about 0.6lbs./ft^3); how severely that'll mass load the diaphram though I'm not sure. Judging by your experience Greg, probably not ideal.

type 11th September 2010 06:06 PM

My goal was to try to salvage the Pencil cabinets that I started for the CHR-70. I was not crazy about this driver even after the recommended 100+ hours so I sold them. Was hoping to try the EL in these boxes but now I'm not sure.

Either way, I just finished the cabinets and for now I cut the holes smaller and put in my trusty pair of 871s and they sound pretty damn good - better in fact than in the Needles.


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