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-   -   Hemp FR8 full range drivers (http://www.diyaudio.com/forums/full-range/91061-hemp-fr8-full-range-drivers.html)

ttan98 26th November 2006 09:51 AM

Hemp FR8 full range drivers
 
After a brief search on this site I could not find any info on the the performance of this full range speakers.

anyone has any info even better direct experience with:

1. How does it perform in comparison with Fostex 206/7?

2. Any info on what type of cabinets that suit this speakers best?

thanks

lousymusician 26th November 2006 02:33 PM

Despite there having been quite a bit of buzz over the FR8's, it seems like there are not too many of us that actually own a pair. I know that dmason has raved about his pair of Omega Loudspeakers Hemps both here and on other forums (fora?), but Omega uses a version of the FR8 that is tweaked to their spec's. I don't know how much they differ from the DIY version. I suspect that the difference is significant. Dan has posted his pair for sale after losing a listening room, so apparently despite his enthusiasm they never took over the #1 spot in his home.

Another DIY member, Nodiak, posted about trying to add phase plugs to his pair (the whizzers came off with the dust caps), but hasn't posted on them since.

I have my pair in simple BR cabinets, 82 liters volume, 4" dia x 4" long flared ports, and I sit relatively close to them in a smallish room (11 x 14'). So far, I have found them to sound like the FR graph on Hemps Acoustics' spec sheet - the highs are too hot. This didn't smooth out as much as I had hoped during break in, and toe in is not enough to bring the treble in line. The 'turn-'em-up-and-listen-from-the-next-room' test confirmed that the basic balance is tipped up too much for my taste. I put them into the living room HT system for a while, and while the highs were smoother when listening from a greater distance, the balance was still too tipped up.

To try to tame the highs I'm using a treble shelf network inspired by the Visaton open bafle thread on The Audio Circles board, currently a 0.1 mH coil + 13 Ohm resistor in parallel (no Zobel). A pretty aggressive filter, but 8 Ohms were not enough. There is also a litte wool fluff tucked in between the cone and the whizzer, which makes a small but audlble difference. I've probably lost too much sparkle at the very top end, but the overall balance is much better, voices are more natural, and I don't miss the extreme highs much.

My mono-buttocked network falls short of full baffle step correction. The midrange balance is best with the boxes against the back wall, but this gives a lumpier bass response in my room. I keep moving them around searching for the best compromise location. I'm sure the FR can be improved with a better network, but I don't have good measurement tools and there's not even a published impedance curve for the FR8 so I'm pretty much flying blind for now.

I'm not done working with them yet. At their best the FR8's do a lot of good things. The bass can be strong and well defined, dynamics are good, there's plenty of detail. If phase plugs can be successfully fitted I think they'd help. I wouldn't be surprised if a little cone or whizzer damping (dammar or Mod Podge) would help too, but again I don't really know enough about what I'm doing to want to make drastic irreversable mods to the drivers.

According to the Hemp Acoustics website, a new version of the FR8 with an improved cone is coming. They say, "In the analyses of our full range FR8DIY the peak exhibited in the midband at around 3-4K was significantly reduced as well the lower treble area around 7-10K is now far more linear, not to mention the high frequencies are more perceivable without being shrill or fatiguing." The graph they show of the difference still shows a significant HF rise, but I'd guess the new version would be worth waiting for.

As to the optimum enclosure, both the Metronome and Scottmoose's Bruce double horn ('Spawn of Frugel Horn') look interesting. If I get a better handle on the basic FR balance of the driver I'd have a hard time choosing which to build. My instincts tell me that Bruce might have the edge in dynamic punch, the Metronome maybe a little suaver midrange, but that's just me projecting my biases. AFAIK, neither one has been built yet for the Hemps.

I've never heard the Fostex so I can't help with a comparison. I hope someone else can chime in on this!

tinitus 26th November 2006 02:53 PM

Hi,

No experience with the driver, but are you sure cabinet is optimal

Have you worked with internal dampening/"stuffing"

From what I have heard it should be very good up to around 1500-2000hz, so personally I would give it a small ribbon

Jim G 26th November 2006 04:01 PM

Hemp FR8
 
Mine are in BIB with none of the problems described by Lousymusician. Balance was good almost from right out of the box. I gave the whizzer 2 light coats of dammar. Mid range in particular is sweet. I also have the Fostex 206e in a horn and found with it problems similar to those described by lousymusician (highs too hot)
With long breakin and various tweaks it got to be OK but nowhere near as good as the Hemp 8 in BIB. I think alot of guys are scared off looking at the sims for BIB. DON'T BE actual response is as smooth as you would want. I have battled the rising response of alot of the Fostex drivers and I'm happy NOT to have to with the Hemp. Jim G

lousymusician 26th November 2006 06:49 PM

Quote:

Originally posted by tinitus
Hi,

No experience with the driver, but are you sure cabinet is optimal

Have you worked with internal dampening/"stuffing"

From what I have heard it should be very good up to around 1500-2000hz, so personally I would give it a small ribbon


Not sure at all that the cabinet is optimized. Too much stuffing killed the bass, so for now I've left a layer of poly batting covering the side wall opposite the port, and the bottom of the enclosure. I have damped the driver basket with Mortite (can't find the sort of ductseal other folks have used around here, the duct sealing products I can find locally are nearly runny, and meant to set up after application). The back wall is partially lined with wavy foam strips (made for installing corrugated fibergalss roofing) to make a diffusive surface. Front and back walls are braced with criss-crossed 1 x 3 battens.

For reference, wiring is Cat 5, 4 pairs of solid wire in parallel. Amps are either a modified ST70 (Curcio driver board and regulated PS) with passive Alps pot, and a 6 watt Tripath amp (TA2020 from Autoconstruire, awaiting modification) with its own on board volume pot.

The problems I hear are above the 1000 Hz range; the published FR shows peaks at 3000 and 9000 that are 10 dB above the 200 - 1000 Hz range. That correlates with what I'm hearing.

Jim G,

Coating the whizzer with dammar has been on my mind. How much effect did that have?

No way I have room for Hemp BIB's in this room, but I have enjoyed my much smaller pair with FR125's. An entirely different sound than the Hemps, the 125's wound up rather bass-heavy and somewhat 'dark' as opposed to the Hemps bright presentation.

Bill

Jim G 26th November 2006 07:49 PM

Hemp 8
 
Bill
I feel that coating the whizzer made a real difference for the good. I also have open cell foam between the whizzer and cone ( 98 cent tweak) I didn't hesitate to try dammar because the whizzer is paper and not the hemp material that the main cone is. Some people have made negative comments about the whizzer. To my ears it works quite well. I like the tone quality of the hemp cone so much that I'm not tempted to do anything to it. I would like to experiment with the Hemp 8 on open baffle. I've read that an open baffle suitable hemp is in the pipeline.
I never figured that my wife would accept the BIB's ( they are big and a lot of different speakers have been through here) After she heard them she said "I think we will have to keep these"

nodiak 28th November 2006 05:45 AM

After removing the whizzers from the Hemp 8's I played them on ob a couple weeks with the Hawthorne Augie for bass, as of course they have basically none on their own (on ob). Very rich full output. Didn't really catch on they lacked highs until compared to FE108ez.
Then rotated CSS125's and FE108ez's each in 10L sealed (cabs were available) to mate with Vifa M22 in 40L vented (ala Dickinson in LCB). The variety has helped me get a better idea what each offers.
Last 2 nights it's Hemp's with M22 bass, they like each other. (GM kindly worked up a mltl for M22, anxious to get that built, should be deeper and a little dryer which sounds good to me).
At this time I don't have a tube amp or even tube pre to go with LM3875 gc integrated, my main amp now. So that isn't fair for the Fostex, barely ok for the Hemp's, but the FR125 seems pretty at home. That's the order I'd put them in for "brightness" and clarity factors vs. "warmth".
But I agree the Hemps have midrange tone and some sweetness. WIthout the whizzers (I guess?) the highest treble is gone and I've been tempted to go with that and work in a tweeter like the BG Neo 3. But i need to learn what replacing the whizzer would do. Been thinking of Dammaring the whizzer first, think I'll take Jim G's lead and do that. The phase plugs are made for the FE167's and are a bit small. Maybe with pp's and without whiz I'm getting a decent midwoofer. Going to get some Redwood whizzers made by a friend (Dude! Hemp and Redwood, oh yah!) Got some honk, even on ob, but I hear stories of up to 300 hours of break in needed. I'll put them in a 40 L cab (what's immed. available) for awhile to hear their fullrange. Jim G, can you recommend bib cab design? I'm game for that.
The 108's are extraordinarily clear and open and I need to get them in bib or metronone or ? to hear some low end from them, to fill things out. And, their designed for tube gear right? I mean they must be, cause with the gc it's too clinical.
FR125's are kinda freaky with so much bass, can't hear the rest as well. Going to xo out the bass and mate with M22 this week so can get a better feel for their mids and highs. At this point they seem the least satisfying -too dark, but I'm sure there's a remedy, open to ideas. The low spl's are a problem for matching to bass drivers. The dipole version must be great tho. BIB's for these huh, have a link?
The new Hemps sound like an improvement, tho these have alot to offer. Just need to try things, bsc sounds like a wise move too. Will try the 98 cent tweak.
BTW, room is ~ 300 ft2, but narrow - 11.5 x 26.5 .
Don

Jim G 28th November 2006 04:52 PM

BIB design
 
Don, I went with design on Godzilla's BIB site ( 200 sq in version) If you haven't waded through the Terry Cains BIB thread all you want to know is there along with links to more than one design for hemp 8. Thanks to GM and Scottmoose designs for hemp 8 most fostex incl. 108 are available . Thanks also to MJK's software. If you have corners available BIB doesn't seem too huge. JimG

VadimB 28th November 2006 07:46 PM

Hemp 8 in a BLH
 
I have recently completed a BLH design for this driver. The project is available on www.e-speakers.com . Scroll a little down to "Vadim Horn Project".
There is a link there to an info package.
In the package you may find all the measurements: impedance, T/S parameters and FR. The FR correction filter is also included.
They do need some break-in. I have measured them brand new and after about 50 hours, and otput above 15 kHz increased by a wopping 5 dB.
My pair does not have hot hights. If anything, they drop down above 14-15 kHz. What is hot is from 1 to 10 kHz.
I do not have the new cones yet, but should get them when they are available.

VadimB

planet10 28th November 2006 08:00 PM

Re: Hemp FR8
 
Quote:

Originally posted by Jim G
I gave the whizzer 2 light coats of dammar... I also have the Fostex 206e in a horn and found with it problems similar to those described by lousymusician (highs too hot)
Jim,

I still owe you some cash for those 2 CDs you got me (and the one i hope you got). Would you like a set of 206e plugs in lei of cash?

I've not even seen a set of hempsters, but i have had good luck with dammar on whizzer cones.

as to phase plugs on the hemp drivers, hemp acoustics has a set of my plugs in hand and are playing.

dave


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