Efficient Paper Coned Drivers

roddyama

diyAudio Moderator Emeritus
2002-01-19 9:25 am
Michigan
Hi Jack,

The JBL LE10A is about 4db down @ 50Hz in a 2cu.ft. closed box. The sensitivity is about 90db/Wm. You can usually find them on eBay for around $120/pr. They have paper cones but they do come with foam surrounds. I run 2 per side and have been keeping an eye open for where I can get rubber surrounds for them. I haven't had any luck yet. The soft butyl rubber should lower the fs (and therefore the f3), but I don't know by how much.

Rodd Yamas***a
 
HiFi World DIY supp 24 in Oct 96 used an Audax PR240MO 10 inch paper coned driver in a sealed 50 litre cabinet. This gave a Q of 1.1 and a 2dB bass lift. The measured -6dB was at 42 Hz.

70litres would give a Q of 1.0 and a bass lift of only 1dB with a -6 at 40Hz.

Due to rising response and cone break up this driver needed a special filter to notch out a 3k peak of +5dB. This was a 10uF cap in parallel with a 0.315mH inductor (0.71mm wire air cored).

After killing the peak they applied a 2nd order filter with 2.85mH (1mm wire ferrite core) and 12uf.

(the EQ filter is connected directly in series with the driver while the 2nd order filter is fitted to the IP terminals as per normal)

This setup gave an output measured at 93dB/w.

Hope this helps, not sure if the driver is still available but by all reports it's fast and gives what you want.

Drew
 

Brett

Member
2002-01-07 6:02 pm
Re: efficient paper cones

Jack Thomas said:
I wonder why some OEM doesn't see the hole in available drivers worldwide for this product?

My guess is that you can get more bass from the same box size with a vented box, so that's what most drivers are designed for. Also paper cones are considered very 'old tech', so you can't appeal to the technically ignorant with advertising that shouts <i>kevlar</i> or <i>carbon fibre</i>. For DR speakers, plain paper cones and sealed boxes usually sound the best ime.

Good luck with your project.
 

RichardN

Member
2002-09-26 12:37 pm
UK
And the peerless 830668

Gets to 50Hz in an enclosure of 40litres or more. Efficiency is 88.6dB for 2.83V.

The question of what Q you are aiming at is almost more important than the cutoff frequency. If you can live with Q less than 0.7 and use the bass lift of your room to counterbalance bass droop, then a whole raft of drivers that are normally used for ported alignments comes into play.
 
That elusive 90dB driver

Thanks, Richard, and others, for your input. I'm shooting between .5 and .7 for the box load. So far, of the speakers mentioned, none have the sensitivity required, and most also do not have rubber surrounds. I think i'm gonna settle on a Vifa Pl26
-09-08. It's got everything but the sensitivity, and as you mention, room gain may give me the extra dB or two that I'm looking for. Anyway, if nothing turns up in the next few days, I'm moving on and hoping the driver integrates with the others already boxed and waiting. Thanks again for the input. I'm using a four way series design (the first three are in a separate box sitting on top of the box waiting for the other driver I've been looking for. I'm using a Morel MDT30, crossed at 2700Hz to a Seas CB17RCY/P, which in turn, strangely enough, is crossed to an Audax HM210GO at 270Hz. The combination sounds better than I'd anticipated, and I have to say that I haven't heard anything sound as good (without deep base, of course) in most of the audition rooms I've been in recently. Hopefully, the additional driver will give me the extra slam needed to register the realism in Welli's Victory as well as other works. Anyway, best of luck to you guys.