Hemp Acoustics FR6.5C

hasselbaink · « **on:** 5 Jul 2007, 07:58 am »

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Just installed a pair of FR6.5C in a 30 by 65 cm test baffle driven by a Trends class T amp (15 W).
http://hempacoustics.com/FR6.5C_-_Hemp_Spec_Sheet_ready.pdf

In my current set up there is a slight dip centered around 7000Hz followed by a gentle lift through out the high frequencies.
You obviously need a larger baffle to get acceptable levels of bass, but the sound is very clear and coherent even without any break-in. Voices are very good so far and the top end is surprisingly natural and relaxed. Compared to my favorite bookshelf speaker (Heybrook Quartet) the hemps do sound less artificial in the high frequencies compounding my dislike for soft dome tweeters. The hemps should have a slightly forward sounding, natural and well behaved presentation.

I will built a larger test baffle later today. In the near future I will get hold of a pair of 15 or 18" drivers that I will hook up with a passive x-over.
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Dmason · « **Reply #1 on:** 5 Jul 2007, 01:55 pm »

Nice. Keep us apprised. A 6.5 inch wideband driver is a good thing, in my experience.

FYI, Tone Tubby, www.abrown.com has a brand new 8 inch HempTone sub driver which looks interesting as well. For a nearfield application, although far from technically ideal, I would imagine this would make an outstanding lower register augmentor, and you could add a small sub for low bass. These would look nice in a nine inch baffle, with 5.5 inch wings. This baffle might give you 160Hz for the mains, and the lower drivers could be low passed with a plate amp, @160Hz, with a 60Hz cut. Active contouring would be essential, but something like that would be interesting, and I am quite sure would work well.

I am finding the 1/2 octave DEQ in Foobar to be excellent.

el`Ol · « **Reply #2 on:** 5 Jul 2007, 03:44 pm »

D OB G recommends low Qts drivers for OBs with passive X-over (see tread "an OB design"). But when I calculate the resulting Qts of the Hemp 15" OB driver (Qts 0.5) with a series resistance of 2 Ohm I only get 0.6 (perfectly alright). Can anybody check this?

zacster · « **Reply #3 on:** 5 Jul 2007, 04:32 pm »

I'm interested in knowing how these sound too. They were a long time coming, as Hemp Acoustics didn't get their act together, and Adire Audio has closed shop. Maybe it is one and the same issue.

I've been looking at Fostex of course for a single driver speaker, and these had caught my eye but there was no info. The 8" was too big, although the 6.5" may also be for what I want. Maybe the 4.5 or 5" fostex are just right after all. These speakers need to NOT appear large for the WAF reasons. I'm still deciding on a box type too, blh, tqwt, ob...The Metronome is appealing as it looks smaller than it is because it is narrow at the top.

hasselbaink · « **Reply #4 on:** 5 Jul 2007, 06:26 pm »

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I need to add a caveat; this is an initial impression of the FR6.5C, not a concluding summary. Due to the small baffles I am using, a portion of the lower register is attenuated or missing. This means that what I hear is somewhat askew. I need a large woofer in order to fully evaluate the hemp's performance. So don't rush off to buy these speakers if money is an issue as they are not inexpensive.

I have a very nice vintage tube amp that is going to drive the speaker and that is the reason I am going the passive route.
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trilateral · « **Reply #5 on:** 5 Jul 2007, 08:31 pm »

There's a coincidence, I've just posted on another forum looking for advice on this driver, having searched to no avail.

I was thinking of crossing it (in foobar) with an Alpha 15 on a 18x36" baffle running off a pair of TA-10.1s. I've put an xbaffle chart up if anyone wants to take a look. Likely to work?

http://www.trilateral.co.uk/OB.jpg

Luigi · « **Reply #6 on:** 6 Jul 2007, 01:38 am »

Im considering similarly, with Visaton B200s. Discovered the Alpha 15A the other day and the Eminence tech reckons this is the one for OB use, with its Qts of 1.26. The Alpha 12A might work okay too, with Qts of 0.77, and sensitivities of 97 and 96 are in the ballpark.
My only real concern is how to implement a low pass crossover. I just have no idea on how to go about this, and what frequency to shoot for. Any suggestions would be welcomed.

markC · « **Reply #7 on:** 6 Jul 2007, 02:09 am »

For a minimal hassle trial, I would run the Eminence woofers from a plate amp and use line level connections out of your pre, (if that's possible with your set-up).
I've been playing with the b200's for a little over a year now, and feel that I'm getting the best sound yet from my current configuration.
My set up is quite different from anything I've read about so far, but it's really working for me. I took my baffles to my friends place last Sunday and set them up on his system, ( which is similar to mine, but his room is quite a bit larger-especially wider). It seems the bigger the room-the bigger the sound.
He has 2 dual 8" driver boxed subs and I have 2 15" driver infinite baffle subs-I like mine better

Now for what is different. I've made a 2-way system with the b200's and the Visiton g25ffl tweeter and set the x-over @ around 2k.
What I'm hearing is a huge, big, fat midrange with an undetectable cross to a very detailed and airy top end. But hey, these are my ears, (oh and my friend's too).

Luigi · « **Reply #8 on:** 6 Jul 2007, 02:43 am »

Hi Mark
My set up is roughly similar. Visaton b200s, with rear facing Fostex tweeters crossed over at about 6500Hz. I take it the Visaton g25ffl is set up to handle a fair bit of midrange itself, which would explain its "fat" nature.

I too have been using a plateamp to drive some 12 inch bass drivers (OB as well) but they do not seem to want to meld that well with the visatons. I was thinking something along the lines of the Alphas would work a bit better. Perhaps it is also because plate amps suck and the one I have is fairly ordinary whereas my main amp is a bit special.
Still, it is the best sound Ive had ever before, despite not being that solid in the bottom end. Perhaps Im overlooking the obvious; I should just buy another pair of the Viastons!

markC · « **Reply #9 on:** 6 Jul 2007, 03:04 am »

{Plate amps suck for sure, that's why I don't let them,(it), go very high in frequency.
One thing that I didn't elabourate on is that my x-over is 3rd order

The tweet definatlely contributes to the midrange, but I feel that it's the b200 that provides that "special" sound of the venue where the music was recorded. Different tracks provide different reverb and I am really enjoying that aspect of my speaks. Taking the highs away from the b200, (blasphemy of course), has really worked for me.

Dmason · « **Reply #10 on:** 6 Jul 2007, 03:19 am »

taking away the lower register from the B200, and tube amp, if that is what is being used, does similar things for the highs.

Apparently the Planet10 phase plugs are no small matter either, from what owners are saying. I believe mxgsr has the plugs in his, if I am not mistaken.

markC · « **Reply #11 on:** 6 Jul 2007, 03:42 am »

Yes, mxgsr does have the phase plugs going on, from what I understand, but I have a bone to pick with him

I would like to relieve some of the bottom end from the b200's, but I don't think passive is a good idea do to phasing, and I'm not quite ready for active eq'ing.

Dmason · « **Reply #12 on:** 6 Jul 2007, 04:05 am »

I dont think nutz and boltz in the way is a good thing for the principle behind wideband drivers. A sonic sandstorm with even the "finest" resistors. You lose the bonus principle of active amplification. This is one HUGE lesson I have learned over the last four or five years. I like the idea of a shunt cap at the amp input, or perhaps at the speaker terminal, and augmentative amplifiers always respond best when fed from the mains taps. Pre out feed I believe is at least partially responsible for the wide belief that plate amps "suck." Obviously some like, totally do, but others, like the BASH amps, and servo feedback, are fantastic, quiet, cold, and not all that expensive. They work best when they are being told what to do by the mains amp. The difference is astonishing, really. Ed Schilling talks about this from time to time, and knows alot about this phenomenon.

I have found that simple actually works really well with the whole mains wideband and augmentative drivers thang, with OB. Now there is Foobar, the apple of my eye. If I can work it, anyone can. The EQ is the icing on the cake: it works VERY well.

Luigi · « **Reply #13 on:** 6 Jul 2007, 09:29 pm »

Hey Mark
I looked up the specs of your tweeter. It suggests sensitivity of around 90db.

How do you get your B200s to work with this? do you pad them down?

I tried three different tweeters (one 93dB and the other "supposedly" 96dB) with the visatons but kept coming back to the Fostex horn loaded tweets (FT17H) because they are similar sensitivity (actually 98.5 I think). I just found any tweeter below about 93dB had essentially next to no output at any given volume setting. Whereas the Fostex are reasonably well matched. That said, I think they need a touch of padding, perhaps a small resistor in the line; have yet to try that, but will soon.

Things are in flux a bit at the moment because I have just inserted the Burson buffer in my set up. Holy toledo, does thing throw a spanner in the works! It's like turbocharging your CD player. Mine had a relatively high output impedance so responded nicely to insertion of a buffer stage in the line. But there is even more treble energy there now than before. So Im waiting for it to run in before doing anything else.

Docere · « **Reply #14 on:** 6 Jul 2007, 09:33 pm »

Hi Dan

>>> I like the idea of a shunt cap at the amp input, or perhaps at the speaker terminal, and augmentative amplifiers always respond best when fed from the mains taps. <<<

I may be missing something, but how do you get the lower freq from the main amp's taps when you hae PLLXOed them out at the amp's input? Am I missing something really obvious?

Cheers
Raymond

markC · « **Reply #15 on:** 6 Jul 2007, 10:00 pm »

luigi, if you look @ the b200's frequency vs. spl graph, (remember I'm crossing to the tweet @2.1k with a baffle step circuit, which knocks it down 3.5 db @ 1k and beyond), the end result is actually less than 90 db. I have to pad the tweet down a couple of db. At 9k and above the tweet is more like 93 db.
AS far as a sand storm, I have but 2 mills resistor in front of the b200. One in the bsc and one in the zobel. The rest of the parts are high quality inductors and caps.

trilateral · « **Reply #16 on:** 14 Jul 2007, 12:04 pm »

Hi hasselbaink,

had any more time to play with the Hemps? Any further opinions on there performance yet?

hasselbaink · « **Reply #17 on:** 17 Jul 2007, 09:07 pm »

Quote from: trilateral on 14 Jul 2007, 12:04 pm

Hi hasselbaink,

had any more time to play with the Hemps? Any further opinions on there performance yet?

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I'll post a picture of my test baffle tomorrow along with further evaluation of the Hemp's.
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hasselbaink · « **Reply #18 on:** 18 Jul 2007, 09:16 pm »

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This is the Hemp in a test baffle with rounded wings. The drivers sound both deeper and more sophisticated with the rounded sides. Before on the naked test baffle there was a little roughness in the lower midrange that seems to be gone now. The bass is obviously deeper, but this driver won't do proper bass without a very large baffle. Listening to Chopin or light jazz it's easy to forget that the bottom octaves are missing. I'll be adding a 15" driver later - stay tuned.
Again, the treble is much better than I anticipated. Maybe I am biased against soft domes, but I think nearly all of them have an artificial and fuzzy sibliance that drives me nuts. An aquaintance of mine who has a TAD horn system, claims that soft domes' main product is distortion. The Hemp treble is more realistic to my ears, than what I'm used to.

Caveat: This is still not a final impression. I can't make a verdict without my trusted tube amp + pre which is undergoing repair at the moment. This means that my turntable is not a part of the equation yet and thus an important and highly revealing piece of equipment is not a part of this ongoing evaluation until later.
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trilateral · « **Reply #19 on:** 19 Jul 2007, 09:27 pm »

Thanks hasselbaink, what was your opinion on the mid range, would you describe it as detailed (bearing in mind your missing components at the moment)? Sorry for pestering, it's just you seem to be the only person in the world with one of these.