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Old 4th August 2008, 02:55 AM   #21
Pano is offline Pano  United States
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I'm in the "your box is too small" group, too.

I've used these drivers a lot and they do like a big box. Not bad on open baffle, if used right.

The Hemp FR8c isn't as bright or shouty as some FR drivers, really.
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Old 4th August 2008, 03:03 AM   #22
cjctan is offline cjctan  Singapore
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Quote:
Originally posted by panomaniac
I'm in the "your box is too small" group, too.

I've used these drivers a lot and they do like a big box. Not bad on open baffle, if used right.

The Hemp FR8c isn't as bright or shouty as some FR drivers, really.

Hi,

I fully understand that the FR8C is totally incompatible with the enclosures that I have made.
There are 2 options for this situation.
i. To build a bigger enclosure for the FR8C
ii. Find a pair of replacement for this enclousre.

I am hoping to find the 2nd solution as I have a problem with space and free time to build them

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Old 4th August 2008, 03:41 AM   #23
ttan98 is offline ttan98  Australia
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Quote:

Hi,

I fully understand that the FR8C is totally incompatible with the enclosures that I have made.
There are 2 options for this situation.
i. To build a bigger enclosure for the FR8C
ii. Find a pair of replacement for this enclousre.

I am hoping to find the 2nd solution as I have a problem with space and free time to build them

[/B]
If you observe the freq. response I posted you will find the the high freq. response is not very good.

I would not use it as a full ranger, you have to supplement it with a tweeter if you want to build another cabinet for it. The bass would be adequate if the cabinet is large enough.

FYI the FR8C I measured comes from Singapore's distributor which you may also have bought them from. It does not measure very well not in accordance with the manu. spec.. It is not the distrisbutor's fault you have to point the finger at the manufacturer.
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Old 5th August 2008, 04:13 AM   #24
Nanook is offline Nanook  Canada
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Default thought I'd weigh in on this one....

because I actually have first hand knowledge of both the Hemp drivers, and the "spiral horns" (theoretically).

4 or 5 years ago, I actually fit the behaviour of the "spiral horns" to a mathematical model, and realized that essentially hanbei's idea was to create a vented box, tune the box to the Fs of the driver, create a "spiral horn" tuned to the driver Fs, and create a "spiral horn" within the vent. This seemed to fit the behaviour of his "design", even though he had/has no real idea of what was /is actually going on. (I know this because I supplied him with the mathematics that was needed to explain it).

The original "spiral horn" idea can be made to work quite nicely, at least in concept. The "angular spiral enclosure" on the other hand seems quite convoluted and overly optimistic. I have no idea how to actually even try to use mathematics to describe its behaviour.

Regarding the FR8c from Hemp Acoustics (Canada), I've had a pair for almost three years. Mine have been modified by planet10 (not ENABLed, but whizzers cut off and FE206 style phase plugs added). The baskets have had Dave's typical "tweak" done to them, and some puzzle coat or other varnish had been painted on.

In this case there seems to be what I would call a more extended and smoother response in the high frequencies, followed by better imaging and virtually no "beaming". Note, these mods are not sanctioned or approved by Hemp Acoustics, and do so at your own risk.

The modded drivers work well in a 20 litre vented box tuned to 42 Hz, planet10 "Demetris" enclosures and very well in "JE Labs style" open baffles. I have never put them in the large BR recommended enclosures , but the enclosures need to be in the 75-85 litre range to work correctly.

hope that helps. Oh and the FR8c drivers need 100+ hours on them to loosen up.


hope that helps

stew
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Old 5th August 2008, 07:18 AM   #25
cjctan is offline cjctan  Singapore
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Quote:
Originally posted by ttan98


If you observe the freq. response I posted you will find the the high freq. response is not very good.

I would not use it as a full ranger, you have to supplement it with a tweeter if you want to build another cabinet for it. The bass would be adequate if the cabinet is large enough.

FYI the FR8C I measured comes from Singapore's distributor which you may also have bought them from. It does not measure very well not in accordance with the manu. spec.. It is not the distrisbutor's fault you have to point the finger at the manufacturer.

Based on my limited hours of listening to these drivers, the HF is still decent and acceptable to me, except for a few shouting.

There is only 1 distributor in Singapore and both of our drivers are form the same source
No pointing of finger here, my failure in this project is due to my insuffient research and ignorance
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Old 5th August 2008, 07:28 AM   #26
cjctan is offline cjctan  Singapore
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Default Re: thought I'd weigh in on this one....

Quote:
Originally posted by Nanook
because I actually have first hand knowledge of both the Hemp drivers, and the "spiral horns" (theoretically).

4 or 5 years ago, I actually fit the behaviour of the "spiral horns" to a mathematical model, and realized that essentially hanbei's idea was to create a vented box, tune the box to the Fs of the driver, create a "spiral horn" tuned to the driver Fs, and create a "spiral horn" within the vent. This seemed to fit the behaviour of his "design", even though he had/has no real idea of what was /is actually going on. (I know this because I supplied him with the mathematics that was needed to explain it).

The original "spiral horn" idea can be made to work quite nicely, at least in concept. The "angular spiral enclosure" on the other hand seems quite convoluted and overly optimistic. I have no idea how to actually even try to use mathematics to describe its behaviour.

Regarding the FR8c from Hemp Acoustics (Canada), I've had a pair for almost three years. Mine have been modified by planet10 (not ENABLed, but whizzers cut off and FE206 style phase plugs added). The baskets have had Dave's typical "tweak" done to them, and some puzzle coat or other varnish had been painted on.

In this case there seems to be what I would call a more extended and smoother response in the high frequencies, followed by better imaging and virtually no "beaming". Note, these mods are not sanctioned or approved by Hemp Acoustics, and do so at your own risk.

The modded drivers work well in a 20 litre vented box tuned to 42 Hz, planet10 "Demetris" enclosures and very well in "JE Labs style" open baffles. I have never put them in the large BR recommended enclosures , but the enclosures need to be in the 75-85 litre range to work correctly.

hope that helps. Oh and the FR8c drivers need 100+ hours on them to loosen up.


hope that helps

stew
Hi Stew,

Thanks for your input.

I have already given up hopes on project until I saw your reply. May I know how did the FR8C sounded in the 20L box, especially the LF?
I am also curious on what improvements to expects after the break-in period of >100hrs?

Is there still any hopes for my Hemps to work in my enclosures?
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Old 5th August 2008, 09:22 AM   #27
Nanook is offline Nanook  Canada
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Default sound of 20 litre enclosures...

was quite enjoyable. Not threadbare or lean sounding. Full-bodied, excellent imaging. They played at least 1/2 octave lower than my Castle Durham 900s, reportedly good to 65 Hz, so I'm guessing at low 40Hz (-3dB point).

If you remove all the plates within your enclosures, and brace the enclosure, then try tuning them to 42Hz (this is what the Aperto is tuned to), I think you will enjoy them. And what do you have to lose? A 56 litre enclosure tuned to 44Hz should require a port that is 68mm in diameter and 59mm long (from linear's LSD pro).

You can do much worse than listening to sreten and panomaniac. Both have proven to provide consistently good advice over the years. By the way, the Demetris are very good with the Hemps installed, and a small amount of BSC applied--the best enclosure I've heard the Hemps in (not including the "JE Labs style" open baffle). Hope that helps.


stew
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Old 5th August 2008, 09:37 AM   #28
Pano is offline Pano  United States
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Default Re: sound of 20 litre enclosures...

Quote:
Originally posted by Nanook
... the Demetris are very good with the Hemps installed...
Yes indeedy-do! The Demetri design seems to be tailor fit for the FR8c. NOT a small box.

I agree with Stew, knock out the spiral baffles and tune the box, you may have a fun speaker. No harm in trying.
As to what driver may work better in that angular spiral box, well..... your guess is as good as mine (maybe better).
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Old 5th August 2008, 09:43 AM   #29
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This is the 1/2 space response of the FR8 in a 20 litre box tuned to 41Hz so 'lean sounding' they will certainly not be, especially with room-gain factored in.

Machining out the internal panels wouldn't be easy, but if you could manage it, & install a vent, at least you could rescue something.

Stew, re the angular spirals, you could model / assume them as a chambered QW cabinet, some of them with some additional mass-loading applied. Exactly what he's hoping to achieve with them though, I don't know.
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Old 6th August 2008, 03:11 AM   #30
fwater is offline fwater  United States
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"...my failure in this project is due to my insuffient research and ignorance"

Join the club! Your statement holds true with my endevors into all fields of speaker building (and I suspect numerous others). Many years ago it was building big subs for cars and failing at first due to lack of understanding the basics. Then it was struggling with crossover design until I became proficient with Jeff Bagby's PCD. Most recently the failures have been trying to defy physics concerning fullrange drivers. In each case I have been saved by building or basing my build on popular and proven designs. Take the advice that you here on this forum and start over with what is recommended. Failure is perfectly acceptable when coupled with willingness to listen and start over, especially when the suggestions are coming from helpfull and wise people such as the ones found here... they've helped me more than once.
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