hemptone fr8 project questions

skite30 · « **on:** 12 Dec 2008, 10:23 pm »

I have a pair of these, actually they are a pair of early omega models. I am looking for a project and need some advice. I would like to use them open baffle fullrange. They have alot of hours on them but have been sitting unused for several months. They are to my ears too sharp in the upper frequencies. Do they need some time to break back in or is this just the nature of this speaker? I would like to use them with either 2 alpha 15's or the AE IB15 and probabaly a plate amp posssibly rhythmic. If the top end doesn't get better I have thought of possibly cutting off the whizzer or crossing over to a tweeter of some kind. On another note does anyone have any experience with the new hemptone extended range 8 or tone tubby ceramic 8. Can't find any specs for either driver but they both interest me if the fr8's don't work out. I was planning on using a 20 x 38 baffle for this project so if it doesn't work out I would just combine the alpha 15's with a pair of dca4 drivers I have a la MJK's passive OB project for the fe103. I know this has kinda been all over the place but I have been thinking of several different projects and wanted some input.

ttan98 · « **Reply #1 on:** 12 Dec 2008, 11:28 pm »

Hi,

I use to have a Hempcone 8" full ranger similar to yours. I tested it using microphone and s/w and I found a rising response around 8Khz. I suspect your unit has a arising response as well since you detect an irritating highs. At what freq is yours occuring may be different to mine.

You can either add a notch filter(you need to know at what freq it is occurring) or add a high freq. tweeter with the associated filters. You can cross it fairly high(4khz) without problem(I tried it myself) the midrange sounds superb.

I like the sound of the midrange it is because of the hempcone material the woofer is made from.

skite30 · « **Reply #2 on:** 13 Dec 2008, 04:30 am »

I don't have anyway to measure the frequency range this is happening. I thought a seperate tweeter might work but I am willing to try just about anything.

ttan98 · « **Reply #3 on:** 13 Dec 2008, 07:07 am »

without the right measuring instruments it is difficult to locate where the rising response is. In addition to design a LP and HP filters without proper software means you will have to design these filters "blindly". There are a few free filter software floating around and you still need to get a microphone for measuring the FR. A steep learning curve for you.

An alternative is get a digital x-over eg. DCX2496 costs US$250(I have one) or an analog x-over(even cheaper on Ebay) which is cheaper. Biamp the drivers sounds better I can assure you. This approach is easily as you don't need to do any measurements just tweak the knobs on the x-over until it sounds OK.

cheers.

skite30 · « **Reply #4 on:** 13 Dec 2008, 03:22 pm »

I would rather not use a tweeter if posible. Perhaps removing the whizzer instead, any dirrection in this procedure would be welcome. I might just get the er8 or ceramic 8 instead and go from there.

ttan98 · « **Reply #5 on:** 13 Dec 2008, 08:49 pm »

I have no experience with cutting out the whizzer cone, you May ruin the high frequence response.

A few models of full rangers except fostex models and some expensive full rangers experience this rising response, models from Hempcone, Tangband, etc have this problem. If you do not have measuring device then it is difficult to locate the rising freq. I cannot help you after this posting.

nodiak · « **Reply #6 on:** 14 Dec 2008, 01:40 am »

I wouldn't cut off the whizzers if you think you could end up wanting to sell them to further another idea. It may not make as much difference as you want, and is not simple, tho you can do it. However I did cut off the whizzers of a pair of Hemp Acoustics 8" fr's and felt it mellowed the highs a little. I was only going to take off the dustcaps to use phase plugs but the whizzers were attached to them and they came off as well. I was cutting close to the dc's edge is why, and the voice coil could've also been damaged as it was close too. So if you're careful you can do it. It didn't ruin the tone on mine and I can use them, but sometimes I'd like to have them complete just because.
I didn't measure the difference so don't know technically what any was (I only have an older octave analyzer). I also tried some tweeters with them but felt none matched the tone quite well enough to satisfy. Also tried some 15" bass helpers and they helped fill in the bottom and mids so the highs weren't offensive. I felt this was a better solution for this driver than a tweeter at the time. Could like the tweeter better if I tried again. I don't think these audio things are any different than changing tastes in food or any other sensual experience (I find I like alot of different audio gear).
So all I'm putting in is that you have some nice drivers to experiment with and the tweeter and/or helper woofer ideas work. You should search here and at diyaudio for things others have done with them. Tastes vary, and some go more for technical verification and some more by feel. Don't expect miracles, it's just machines playing back recordings made by other machines. Good to go with small changes, maybe jot down some notes so you don't get too lost. It's possible to have some fun with it too

Don

DanH · « **Reply #7 on:** 14 Dec 2008, 03:34 am »

I have the early version of Hemp Acoustics FR8 which appears to be darn similar to the Hemptone FR8 in looks and specs. In my speakers the upper mid-range glare reduced after a long break-in. I think it was over 200 hours. I did cut a felt circle and glue it to the dustcap which helped also. The problem IMHO is a high frequency resonance between the dustcap and the pole piece under it or possibly in the cavity formed by the whizzer.

skite30 · « **Reply #8 on:** 14 Dec 2008, 03:39 am »

That's pretty much what I was looking for I have no experience with these and didn't know if they would loosen up with use or if I needed to try something else. I didn't like the idea of a tweeter or removing the whizzer and thought I would ask for advice. I really like the mids and the tone but I listen to quite a bit female vocals and can't stand sibilant vocal transients. I have a small pair of subs now but would like to try an ob woofer arrangement. I am obviously not real technical and just want to enjoy and have fun with the whole experience. I was hoping someone had some information on the hemptone er8 or tone tubby ceramic 8's I can't fine any specs for those drivers or frequency response plots. I see dmason has had some comments on those 2 drivers but haven't been able to find anything else on them.

nodiak · « **Reply #9 on:** 14 Dec 2008, 04:28 am »

DanH and I likely have the same drivers. And I remember the photo's, specs, and frequency graphs were identical to hemptones at the time, so I suspected (no proof) they were possibly the same drivers, dunno for sure. I can see the felt helping. I have used wool encircled at the base of the whizzer (similar to the "98 cent mod") and phase plugs. Both helped. Haven't tried any coatings, but maybe on just the whizzer could help? Definitely long breakin helps alot, and they need some extra time again after sitting.
skite30's, the dual woofers might work well. Also if you use a seperate plate amp on the woofers you could get away with one, depending on how loud you need to go.
Just a nice tone driver worth the time and effort imo.
Haven't heard reports on the 8 ER, but I think someone at diyaudio was working with TT ceramic 8 guitar speaker.

TerryO · « **Reply #10 on:** 14 Dec 2008, 04:43 am »

Quote from: nodiak on 14 Dec 2008, 04:28 am

DanH and I likely have the same drivers. And I remember the photo's, specs, and frequency graphs were identical to hemptones at the time, so I suspected (no proof) they were possibly the same drivers, dunno for sure. I can see the felt helping. I have used wool encircled at the base of the whizzer (similar to the "98 cent mod") and phase plugs. Both helped. Haven't tried any coatings, but maybe on just the whizzer could help? Definitely long breakin helps alot, and they need some extra time again after sitting.
skite30's, the dual woofers might work well. Also if you use a seperate plate amp on the woofers you could get away with one, depending on how loud you need to go.
Just a nice tone driver worth the time and effort imo.
Haven't heard reports on the 8 ER, but I think someone at diyaudio was working with TT ceramic 8 guitar speaker.

I'm not sure, but if you do a search for Curt Chang, you might find something about the TT ceramic 8 guitar speaker. Curt's been at it a long time, is very knowledgeable and evidently likes the TT ceramic as his mid/treble driver and, IIRC, doesn't feel it needs a tweeter.

Best Regards,
TerryO

nodiak · « **Reply #11 on:** 14 Dec 2008, 05:12 am »

Thanks TerryO. skite30 here's comment from Kurt Chang on his speakers, post 12 in this thread:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=132951&perpage=10&highlight=&pagenumber=2
I tried the neo3pdr's and came to the same conclusion.

Might be more in that forum.

skite30 · « **Reply #12 on:** 14 Dec 2008, 03:35 pm »

These drivers came with what looks to be some sort of styrofoam plug inside of the whizzer. Guess it is acting like a phase plug of some type they sound good off axis and don't beam like some drivers I have tried. I will try the 98 cent tweek on them and give them more time and see if they mellow out a bit. I have a small room and a couple of small subs but would try like to try the alphas or the ib15's instead.
thanks for all the help

panomaniac · « **Reply #13 on:** 15 Dec 2008, 03:49 am »

Try the felt and the wool - they will help. So does break-in.
Then try a series inductor. Something in the range of 0.2mH to 0.5mH. That will tame to rising response and give you a better tonal balance. You want to flatten that rising response.

You may still need a tweeter above about 6~8K. No big deal. Just a cap for x-over..

nodiak · « **Reply #14 on:** 15 Dec 2008, 05:17 am »

panomaniacs idea works, i used a .5mH and then cap (1-2 uF iirc) on tweeter. One tweeter tried was a Scanspeak soft dome (90db) using the waveguide on Zap's site (TMM speaker). Was close but fell a little shy in spl's. Maybe 92dB would be a better fit imo. Lots of possibilities. Maybe you have some tweeters around to try?

skite30 · « **Reply #15 on:** 15 Dec 2008, 10:02 am »

The series inductor would be placed where? The cap would be placed where? The closest thing I have to a tweeter on hand is the david merrill dca4.Sounds like good advice just a matter of learning how to implement it. Thanks

panomaniac · « **Reply #16 on:** 15 Dec 2008, 08:13 pm »

Connected in series with...

I.E. cut into the + line. As tho you took a chunk of wire out of the positive speaker wire and replaced it with the inductor (FR) or cap (tweeter). Simple.

skite30 · « **Reply #17 on:** 15 Dec 2008, 09:07 pm »

Sounds simple enough. Do you have any preference for type or brand of inductor? Air core, iron core, copper in foil etc. Any experience with the hemptone 6.5. Did a search but not much came up.

androuski · « **Reply #18 on:** 15 Dec 2008, 10:25 pm »

I have the same thing in mind for my FR8C, I want to try something between 0,22-0,47mH, and to cross it with a pair of hiquphon OWII I kept from another project, with 2,2 or 2,7µf, my purpose is not to make a high end crossover, but just to tame the 10-12db raising response from 2000hz to 10000hz area...

panomaniac · « **Reply #19 on:** 16 Dec 2008, 12:48 am »

You want an air core for this job. I wouldn't bother with the foil types for this app.
You can get either Solen or Janzten in most countries. They are both very good.
Same for the caps - I love the Janzten Cross-Caps.
Remember that you're if you're running this driver fullrange that you'll want a large gauge inductor.

But any good aircore inductor and good film cap that's available wherever you are.

I have not heard the Hemptone 6.5 but have heard the H.A. 6.5 and like it a lot. I imagine that they are basically the same driver.