Thread: GR Research Line Force speakers

I thought I'd share my latest DIY speaker project. In this case, there wasn't a ton of DIY work. I had the cabinets made for me, so just had to install the drivers, build the crossovers, and wire everything up. I included some background in case you are interested.

I built a pair of GR-Research NX-Otica speakers a few years ago and was very impressed with their performance given their moderate price ($2800/pr at the time). When I read about the Line Force, I decided I really wanted to build a pair.

The Line Force is an open-baffle line array utilizing six Bohlender-Graebener NEO10 drivers and sixteen NEO3 drivers for each speaker. It was originally developed by GR for Serenity Acoustics. Unfortunately, shortly after the speaker was developed, B-G was acquired by Christie Digital who decided to stop selling their drivers to the OEM market. Since this product and Serenity's other speaker (the Super Seven) were both based on the B-G drivers, they were forced out of business.

GR developed their own NEO3 clone driver (which they use in a number of their kit speakers), but do not yet have a NEO10 replacement. In 2020, Parts Express was still getting an occassional shipment of NEO 10 drivers from B-G, so I back-ordered enough drivers to build these speakers. Five months later (late 2020), PE received their last shipment and I received the drivers.

The cabinets for these speakers are made out of a composite material in order to be stiff and strong enough with all the cutouts for the drivers. Unfortunately, Covid supply chain issues caused a severe shortage of the resin required to make this composite, so it wasn't until late 2021 that the composite material became available. By that time, all the CNC shops that dealt with this material were so backed up that it took another six or so months before I could get the cabinets machined.

I finally got everything necessary to assemble these speakers in late October. The crossovers are built with Miflex copper foil in oil caps, bypassed with Dueland JDM Tinned-Copper bypass caps, Munford foil inductors, and Path resistors. All wiring is Neotech UP-OCC solid core copper in teflon.

These big copper caps take a while to break-in. But I now have about 300 hours on the speakers and over the last couple weeks, the speakers have really started to sound wonderful. They are a relatively easy load (nominally eight ohms droppind to six in the lower frequencies) with approximately 98db/w efficiency. Since they are line arrays, the sound pressure drops off much slower with distance than a point source speaker. So my 300B PSET monoblocks have plenty of power to really make them sing.

They cross over to GR-Research Triple Threat open-baffle servo-controlled subwoofers at about 170Hz.

While the B-G NEO10 drivers are no longer available, Parts Express is selling the GRS-10 driver which is similar and about the same size. Unfortunately it doesn't handle low frequencies as well as the B-G driver, but GR is working on a new crossover to see what they can do.

These speakers took quite a while to get done with all the delays, and were considerably more expensive to build than the NX-Oticas. But I'm thrilled with the results - well worth the wait and cost.

Those look great Jay.

Very nice Jay, those look awesome. Never seen caps the size of artillery shells like that before, cool!

Originally Posted by Barry

Impressive. What terrific looking speakers! Bet they sound great.

You're not done yet hours-wise. The best way to break in big caps and related parts that size is with a cable cooker. It will still take a few hundred hours. Then look out.

Yes, I suspect it will take another 2-300 hours. But they are already sounding superb.

Originally Posted by apdoc2004

I would love to hear these speakers. I do visit the Portland area frequently as I live just a couple of hours from there.

Let me know when you are coming to town and we will set something up.

Originally Posted by Puma Cat

Very cool build, Jay. Your system will pay dividends for your commitment and discipline in sourcing the parts.

Danny really knows what he's doing and is the real deal when it come to speaker design. 👍

Thanks. Nice looking XLS build. Yes, I've been pretty impressed with Danny's designs. I also have a pair of NX-Studios in my bedroom system that sound very nice.

I'm using Kimber Select KS-3035 cables on these speakers right now and am very pleased with them. I think the only cables I would consider switching to at this point is moving up the Kimber line.

When I first got the big copper caps, I was a bit concerned that I wouldn't be able to fit everything on the crossover boards. In the end, it was a tight fit, but they came out nice. When I finished building the first one, I just had to weigh it - came to 22lbs!

I replaced the woofer towers with a new set painted to match my Line Forces. These new towers have four 12" servo drivers per tower. Each tower is driven by a Rythmik HX800 amp, which has two 400W channels with servo feedback. Each channel is connected to two drivers.

The difference compared to the triple towers is pretty subtle, but in-room response is a bit smoother. I have yet to find any music that stresses them in the least.