[Telstar]

Hempatics is the name that I gave to my babies

After months of research and hundreds of kb of electronic ink spent on forums and emails, the fullrangers have been chosen and the Hempatics are born.

Day 1
An unexpected ring in the late morning brought the quite unexpected news that my package arrived from the Netherlands in just 4 days. I had hoped to get them before the end of this week, but I wasn't counting on it.

If now you are suspecting the reason of the name, it's now revealed. The FR are a pair of Hemp Acoustics FR8C, production date 6/2007.

The package:


The invoice:


The little boxes:


As you can see, one of the baskets came through the box, but no damage has incurred:


Close-up of the corner where the sourround is slightly scratched (hard to notice):


The babies:

They are sooo cute! And little.

The temporary baffles, made from the cardboard of the inside of the box. It makes for a very handy floor mounting.


Here are the drivers connected with bare DNM wire.
Left one:


and Right one:


Now, its 3 hours that they are burning in, hooked to the ovenly* Firstwatt F3.
They sound, no issues whatsoever. Quieter than I expected, but they are already pleasant.
I will do a first impression listening test tomorrow morning at higher volumes.

[* hope you get the joke, if not oven/heaven.]

[Telstar]

Day 2

Very first impressions ad normal SPL, after about 5h at normal SPL + 7h at very low yesterday.

The rest of the chain in this moment is composed of:
Teac vrds10se (with tent clock)>Muse Model Two>Classè CAP-100 (only as pre or as integrated)>Firstwatt F3. Comparison speakers are my old Linn AV5140. Obviously is my intention to besten them in all parameters.
For simplicity of switching (I do AB very often, the Classé mutes its own amp stage when used this way, which is very handy), the Linns are connected to the power amp stage of the Classé, while the Hemps are connected to the F3. In both cases the preamp is the (very good IMO) preamp stage of the CAP-100. Also note that the F3 is NOT able to drive the crossover of the Linns, and was tested only on the midrange (filtered).

Negs:
First, it definitely needs a bass augmenter. I will measure with simple test tones how low it goes, but it lacks the punch. This is the most apparent deficiency.

Second, air is lacking. This is more disappointing. The F3 is able to deliver SOTA "class A" airy sound and I want it all. I hope finishing the burn-in will be enough, otherwise a supertweeter will be needed.
My hearing is VERY good, I can clearly listen to 17k tones and I'm also sensitive to HF distortion.

Third, Vocals are already of matching quality, plus the tubelike quality of the F3.
It is not truly a merit of the Hemp, but just of the F3, which has in the past be connected to only the midrange driver of my Linns, exibiting tubelike qualities while keeping distortion low (@4 ohms).

Fourth, HF have some harshness, but it is already LESS than yesterday, so I think it will be gone by the end of burn-in. If not completley, I'll use dammar on the voice coil and whizzer.

Positives:
None, so far.
The only advantage being represented by the single driver doing the job of a midbass, midrange and tweeter.

Ok, I can say that the timbre is accurate, and that with some songs I can get already a more "you are there" feeling. But not enough, not even close to my goals.

I'm sure that the source is the bottleneck, and I do plan to replace the DAC and a computer source, but before that I need to be sure that the FR are of sufficiently good quality for my expectations.

Note that the Hemps are playing on the floor, with about 30° inclination upwards, and 30cm to the back wall. I'm not sure how much this influence my impressions. Anyway, I will start building pressed cardboard baffles next week.

PS: Note that this same journal is being posted on diyaudio fullrange forum.

[mcgsxr]

A good start, and once you mount those on baffles, and raise them up to ear height, I will be interested to hear your thoughts.

Thanks for sharing!

[ttan98]

I was able to lay my hands on a pair of Hemp 8FR about 1 year ago, they sound quite good, however there is a minor fault that is it displays a serious  spike(bump, > 3db) at around 8Khz. I suggest you check it out. They may have solved this problem by now.

[Telstar]

A good start, and once you mount those on baffles, and raise them up to ear height, I will be interested to hear your thoughts.

It will be done soon.

BTW I think I have been too critic this morning.

[Telstar]

I was able to lay my hands on a pair of Hemp 8FR about 1 year ago, they sound quite good, however there is a minor fault that is it displays a serious  spike(bump, > 3db) at around 8Khz. I suggest you check it out. They may have solved this problem by now.

They shout a bit, but it may be lack of burn-in Otherwise, it's either that bump still there or they have a changed to a lowtherish curve. Either way, it'll be corrected.
The published specs shows a very smooth response.

[DanH]

The shout moderates some after 100 or so hours of use. I ended up cutting out two small circles of felt and gluing them to the dust cap with Elmer's spray glue, it is supposed to dry tacky instead of hard. I cut the felt so it did not touch any part of the whizzer cone. The driver's qts is to low to produce much bass in an open baffle. I put mine in a large bass reflex cabinet, about 90 liters, and they produce nice bass that way. I ended up adding a super tweeter in parallel with the FR8 to balance out the sound. I was thinking of trying them in a MJ King style open baffle with a Eminence Alpha 15 woofer and a 400hz crossover.

[Telstar]

The shout moderates some after 100 or so hours of use. I ended up cutting out two small circles of felt and gluing them to the dust cap with Elmer's spray glue, it is supposed to dry tacky instead of hard. I cut the felt so it did not touch any part of the whizzer cone.

Interesting. I plan to put dammar on the whizzer and voice coil. I do not feel like having the skills and the time to do ENABLE, but i have saved all details regarding that process on this driver.

And I plan to try different drivers (in the same baffles), in particular a 10" that is not available yet

The driver's qts is to low to produce much bass in an open baffle.

Yes, of course, but it was taken into account. I would have chosen a different driver if i wanted to do without woofers. The FR8C instead has one of the best HF response (comparing for example to the B200) - this way I can do without tweeter.
I'll add woofers soon, but all in OB
I think that the midbass is not lacking, though. Measurements will follow.

[panomaniac]

Very nice!  I think yo're goin gto like this driver.  I've used it in a number of different speaker styles and it's always nice.
Here is my version of the FR8 on OB.

That's a Selenium 15 under it.  The FR8 certainly needs bass support on open baffle.  No matter what baffle style I tried it still needed bass support.

But as an OB midrange, it's very nice. 

[Telstar]

That's a Selenium 15 under it. 

Nice speakers I'll add 12" woofers soon (not chosen if 1 or 2 per side), i cannot fit 15".

The FR8 certainly needs bass support on open baffle.  No matter what baffle style I tried it still needed bass support.
But as an OB midrange, it's very nice. 

Yes, and that's because of the low Qt. Of course it was taken into account.
The midrange seems the best aspect of the fr8c.

I'm finishing the cardboard baffles (2x3mm pressed cardboard glued together - the glue is drying under pressure of many heavy books). I'll post pics and impressions when i mount the drivers, i think tonight or tomorrow.

[Telstar]

Here I am with a due update.

Burn in continues and it's taking long: 90h and counting. In the meanwhile, this morning i added some felts to dampen the backwave, since the speakers are and will remain pretty close to the back walls (around 60cm)

You cant see from the pictures, but the felt layers have been cut with growing size holes. There are 7 layers of felt and only the back of the magnet is open.

At the same time, I moved farther the Linns, leaving the test baffles to touch only a corner (for safety) and almost parallel. This way the backwave does not reflect on the other speakers and thanks to the deep felts, reflects also less onto the back wall.

Results?
The sound is more pleasant, i'd like to raise the volume up, rather than put it down. It's obvious that a 20% of the backwave was bouncing on the Linns, with obvious problems. The felts are useful, on the definitive baffles I will order the wool ones, as recommended by John K. For me they are worth the money.

Other changes after about 90h of burn-in: Some more bass came out, HF are less fatiguing. The shouting remains, especially with some recordings. It has to be noted that these fullrange without XO driven by my F3 are absolutely merciless of poor recordings. This can only improve with the addition of a preamp of the same level of transparency. Dunno instead when will be ready the new source (read a very, very special DAC).

Picture of the 7 layers of felt, from above:


Left speaker with felt:


Right speaker with felt:


Next steps:
1) More burn-in, at least another week, with the current setup, then measurements
2) Second version of test baffle, in mdf this time, with hole for the woofer, and more measurements
3) Adding woofers (trying also side placement and U, VPL shapes) and wool felts, more measurements
4) Definitive baffles made of at least 2 layers of birch plywood and one of mdf.

About woofers, i'm choosing between the Beyma SM100N and the Peerless SLS-315. A behringer dcx2496 or another one that is not available yet will be used to cross and equalize, and a dedicated amp of at least 100W will power them.

[markC]

OB is all about the addition of the back wave in my experience. I don't really understand why your choking it with the felt.
I feel that the "openness" of the sound needs the back of the driver to be able to breath.
Just my thoughts.

[Telstar]

OB is all about the addition of the back wave in my experience. I don't really understand why your choking it with the felt.
I feel that the "openness" of the sound needs the back of the driver to be able to breath.
Just my thoughts.

Because the speakers are too close to the back walls.

I'm burning and listening. I think I put too much felt, i'll use less in the second test baffles, before ordering the woolen one.

[markC]

Will the final versions have to remain too close to the wall?
I've found with mine that they like to have some distance from the back of the speaker to the wall in order to sound they're best. Mine sit about 130cm from the wall. The rears do, however, fire into corner bass traps which are more like 90cm away. It would be good to experiment with placement as much as practicle.

[Telstar]

Will the final versions have to remain too close to the wall?

Yes, unfortunately yes. The max I can have is 70cm (front of the baffle to back wall distance).

I've found with mine that they like to have some distance from the back of the speaker to the wall in order to sound they're best. Mine sit about 130cm from the wall. The rears do, however, fire into corner bass traps which are more like 90cm away. It would be good to experiment with placement as much as practicle.

These test baffles are not stable and i prefer to let em hold onto the linns. The next ones, in mdf will be sturdier and i can move them more for testing.

I feel that a moderate damping is gonna work. I don't think they are sounding as a closed box. But I noticed more air coming out, so you are right that the felt i put is too much.

For bass, there'll be the challenge. Bass cant really be dampened. I have to study some way to place and "baffle" the woofers. Thinking sideway U frames and ripoles.

[markC]

yes, experimentation is more than half the fun for me. Throwing together quick & dirty test baffles until the "right" sound is achieved. Then make some purdy ones.

[Telstar]

Now the biggest problem is the shout. It's not gone and I'm afraid it will never be, unless i filter it.

More to come about woofers and measurements.

[Rudolf]

Now the biggest problem is the shout. It's not gone and I'm afraid it will never be, unless i filter it.

Ask panomaniac how his FR8s shout without the Seleniums below. Me personally would not dare to judge the "shoutiness" of a midrange driver without a decent bass fundament. Have you ever listened to your Linns with the woofers switched off?
 
In my own system the woofers are responsible for everything below 300 Hz. Mids and highs really shout and hiss when I switch off the woofers. I believe that you need very much experience as a driver tester to judge isolated drivers without the context of their broadband integration.

Rudolf

BTW: Your cardboard baffles may be "rigid" for higher frequencies. But they are a weak and bending support below ~ 500 Hz. All your low frequency experience could be meaningless unless you have more rigid baffles.

[Telstar]

Hi Rudolf,

Thanks for chiming in.

Ask panomaniac how his FR8s shout without the Seleniums below. Me personally would not dare to judge the "shoutiness" of a midrange driver without a decent bass fundament. Have you ever listened to your Linns with the woofers switched off?

Yes, I have. Mids (400-4.5k) only powered by the F3, when I was checking/burnign it. No shout. The highs-highs in the Linns are inferior to the Hemps, though.
I can do another test tomorrow, but i'm 99% sure that they dont shout.
It's possible that as you say the lack of bass-bass make it show more.
But I think the Hemps need a notch filter, period.
 

BTW: Your cardboard baffles may be "rigid" for higher frequencies. But they are a weak and bending support below ~ 500 Hz. All your low frequency experience could be meaningless unless you have more rigid baffles.

The midbass is not that bad at all, it lacks lets say under 200 (not measured yet). The timbre is good also with male voices (they dont sound like castrates).

[Rudolf]

Yes, I have. Mids (400-4.5k) only powered by the F3, when I was checking/burnign it. No shout. ...
I can do another test tomorrow, but i'm 99% sure that they dont shout.
...
But I think the Hemps need a notch filter, period.

No need to do another test. Your ears are closer to the delinquent than mine. And the DCX will give you any freedom to test and find the best approach.