EL70 Bipole Metronome results

[mor2bz]

I have finally finished a project I started long ago. The cabs are
of BB and a truncated brace (2') was employed. I used a very large screw lag with a decorative head threaded into each side of the brace to butt up against the back of the driver. The drivers were installed first without a thick gasket (not the supplied one) to adjust the position of the screws. When the screws were adjusted so that the drivers almost touched the baffles, the drivers were installed with their gaskets. My fears that it would be very hard to connect the drivers physically with the center brace were completely unfounded. I must say that this method with the brace resulted in complete cancellation of tranfer of vibration from the drivers to the box. A very good feature. The drivers were broken
in in sm. sealed boxes before being installed in the large mets.

I am thrilled with the look of these towers; I wish I could say the same
about the sound. I very much wish I had stayed with Fostex drivers, although
I see that they are now downgraded as well as the old Fe xx7 line has been
discontinued (much to my disapointment).

I find the bass to be very much overstated and bloated. I do not like so much bass, and when i have a design that measures flat I find that I have too much. The stated range in the bass is there, but in asking so much of these tiny drivers distortion sets in VERY early on the volume control. I should have known better, expecting so much of such small drivers. There just is no free lunch with loudspeakers. I would take my small fe164 monitors over these any day of the week, even though they are light in the bass. The mids do not have the same quality as the Fostex drivers I have always used. And the highs and the efficiency are nonexistent.

Perhaps ANOTHER 200 hours of break in, more stuffing in the line, and a tweeter would help. But these are never going to replace my fostex-eminence 15 open baffles.. Not in a million years.

[motosapien]

I would not fault the EL70 but perhaps the enclosure. My Coniston^2's sound wonderful with the bass being close to just right. They do improve in the highs after a few hundred hours. I also tapered the highs out of one driver with a 68 uF cap. After listening to them for some months, I switched back to my GR Research N2x's and I prefer the Conistons.

Maybe some aggressive stuffing is in order to tame the bass?

[planet10]

The EL70 can be a bass monster. Unlike most other drivers, the need is to tame to much, as opposed to try to get more (easier to fix too much than too little). More stuffing is the 1st thing to do... the drivers do take a long time to break in, but after the 1st 100 hrs or so, it is the midrange that improves the most. When we 1st started out with these (Mar-Kel70), we gave the edge on midrange finesse to FE127eN in Fonken, but after 500 hrs or so, the differential became much less. The presentations are different, the FE127 being more forward, so that can play a role in which is preferred.

The one customer that i have who has built 3 sets of bipole mets with EL70eN has added helper tweeters to 2 of his pairs (CSS ERT26 aka Mark Audio #3), but i'd get the bass sorted before considering tweeters.

How much stuffing have you got in them? Can you post pictures?

dave

[mor2bz]

Motosapien

what you filtered out of one driver was the lows, not the highs.

[rjbond3rd]

Hi mor2bz,

Why not bleed off some of the bass by "gapping" one of the drivers? Just unscrew and leave a millimeter or two of gap. Maybe insert a small shim under the frame.

By the way, if you hear any bass at all, you must be wired for bipole (rather than dipole).

[planet10]

Originally Posted by mor2bz

Motosapien

what you filtered out of one driver was the lows, not the highs.

That is not so. With drivers wired in series, you filter the highs out of one of the drivers (ie LP filter) by shunting it with a capacitor)



If you look at the diagram, at high frequencies the reactance of the cap across the EL70 goes to zero, so all the HF go thru the cap and not the EL70s. At low frequencies the reactance of the cap becomes very high so all the lows go thru the EL70.

dave

Note: in the end i believe the tweeter was removed.

[planet10]

Originally Posted by rjbond3rd

Why not bleed off some of the bass by "gapping" one of the drivers?

Something i'd only try as a last resort as it would affect the tuning a bit.

By the way, if you hear any bass at all, you must be wired for bipole (rather than dipole).

You'll note that i made that assumption and fixed the title.

dave

[mor2bz]

I didn't realize he had shunted the cap; I assumed a series cap.

I have used a series 1st order in my eminence/fostex OB. So I understand how
it works. I do not notice any problem without a 2nd order circuit to keep
the bass driver from intruding into the midrange.

These speakers were loosely modeled on the James D. open baffle. I figure
mine are even better cuz I crossed them over a little lower, and I use
a slightly less efficient fullranger (fe164 instead of fe167) so the bass is effectively turned up relative to the fullrange.

thanks for all of your comments, and thanks for not turning this into a ******* contest. I have learned much through my attempts and must chalk everything
up to education. There is no free lunch there either.

[chris661]

I was going to say - breaking them in in small sealed boxes will never work.

You need to get the cones moving for the suspension to loosen up. A small sealed box provides more resistance to cone movement, so they won't have loosened up as much as they might have on, say, an open baffle.

Chris

[mor2bz]

they were moving; no problem. I had a SS amp hooked up to them.