Gilmore - hows it done?

I just got off the phone with a friend that heard a pair of Gilmores and hes in love. I did some research and it appears that they have gotten great reviews and aside from the cost, seem to be very straightforward.

Four woofers, one ribbon and a passive xo, all mounted on a piece of Corian. How can they perform so well without all the normal electronic equalizing and biamping etc and also be 90db efficient?? And shouldnt these be clonable?



2004-10-15 9:38 am
It's also VERY hard to believe that they can keep that low end response very loud. The woofer is going to be excursion limited very early that low, compared to the 120+ dbs they say it can do.

They use very high q woofers which allows you to sort of get away with not having an eq. There's and old Carver dipole that does the same thing. Talking about a Qts of around 2.0 or greater. No idea how well it works.

I dont believe Ive ever seen a bass driver with that high of a qts. Ive heard the Amazing Loudspeaker years ago at the CES and very pretty impressed at the time. I would assume that high qts drivers are a custom build and arent readily available. And it looks like a B-G planar, similar to the Carver concept, is what is used. So it looks like those 12" woofers are key to the operation of the thing. If it truely sounds that good, it sure is a KISS design.

At 17Hz (and well higher in frequency too) with no enclosure to trap the back wave, those cones will be really pumping at extreme excursions! I doubt that really loud levels can be achieved down low with so much dipole cancellation, no matter how high the Qts is, and there's bound to be large harmonic production and compression going on. You can't fool Mother Nature.

These speakers may sound great despite these limitations - I don't know since I haven't heard them. And, yes, the balloons are very nice.
I picked up a recent copy of Absolute Sound (I think) because it had an article on the Gilmores. I was hoping to find out what a "planar dynamic hybrid woofer" was.

The article was pretty light on details with few pictures and was pretty much a fluff piece. However, the reviewer very politely pointed out that the ribbon had a ragged response that Gilmore was still trying to fix.

If I remember correctly, the ribbon is really a planar magnetic tweeter.

The Glacier site is devoid of any detail save Corian samples. No crossover specs listed. I'm just scratching the surface of dipoles but it seems that you could use a passive 6dB/oct low pass at or just above the woofers' Fs to deal with dipole cancellation and a second low pass to crossover to the ribbon. This same concept models well using Brian Steele's dipole workseet.

I think all the superlatives that people pour onto this speaker should be attributed to Carver (and Bohlender), Selmer, Linkwitz, and others who have championed the benefits of dipoles along with JBL, Dr. Jim Griffin, and others who have developed better understanding line arrays.
Found a little bit of info on the crossover from Positive Feedback:

Our crossover is a two-way, fourth-order Linkwitz-Reiley design.

Carver, Apogee mentioned multiple times.

Lots of mispellings in that article.

Yes, its not a new idea but seems that its well implemented if all the specs are for real. I checked B-G and 88db is what they get out of their drivers. So Im not sure how he manages to gain 3db. Im thinking that a RD50 and 4 Peerless 12" XLS would be a good approximation.But Ive read that the B-Gs really sound their best if not crossed too low. Over 500hz was mentioned. Not sure how a high excursion woofer sounds up there.

Im still most interested in the fact that no active xo or equilizing is used. And 91.5db