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Old 30th July 2008, 06:52 AM   #1
cjctan is offline cjctan  Singapore
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Default Hemp Acoustics FR8C in Angular Spiral Enclosure

Hi All,

I have completed a pair of angular spiral enclosures and mounted with Hemp Acoustics FR8C.

Listen to it after run-in for 8 hours and I am still a bit dissapointed by the low frequencies and some shouting heard for high frquencies.

I would appreciate if anyone can give me some pointers on how to improve the sound?
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Old 30th July 2008, 08:15 AM   #2
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http://www.hempacoustics.com/FR8C_-_...heet_ready.pdf

hard to see but I see a 5-10db climb past 700hz.......

shout seems to be a climb in midrange output...............

sort of like baffle step (bass seems gone compared to mids/highs).................

here are some comments on shout
"the drive unit itself is heavily modified with a unique phase plug and whizzer cone which removes the ’shout’ that Lowthers can typically display "

================================================== =====================

Tannoy Mercury M2 loudspeakers
As expected, the macro-dynamics performance of the mid-high range is better, though I won't suggest to drive this speaker far too loud or it'll start to shout

================================================== =====================

Visaton BG20
"it may need baffle step compensation, and with this driver, some form of EQ to tame the mids 'shout'/drooping HF response as already noted.
================================================== ====================

As good a job as Rethm did of reducing the infamous Lowther shout --- an upper midrange peak in the driver's frequency response
================================================== ======================

The phase plugs should fix it...my 206 sounded aweful with nothing there, very shouty. your phase plug looks neat.
================================================== =====================

I did some more listening. As somebody said before, here in this thread without dust cup they somehow shout.
So now I painted them with one layer of dammar and put those phase plugs from the picture in.
================================================== ======================

I'd even read that shout can be caused by a bad enclosure......
Story on decware is you get a cheap transistor radio, set to voice at volume you listen at (from where you sit).........place radio in speaker box, then install speaker. What you hear is what is happening in the box then mixing / modulating the driver gettong back into the environment instead of vanishing into a black hole...........
some refer to it as "boxy sound" where midrange resonates in the box...........................

I dont see much damping in those boxes.................

Parallel walls are bad, and same dimensions (width = depth) is bad too.

or if you have speaker away from front wall, do you have any baffle step compensation ?

a 10 band equalizer could be a great friend for you.

and a whizzer would be nice also.

Oh, I just noticed you only have 8hrs on them, maybe sound will improve (more detail as surround/spider stretch a bit).

Oh, I also see the cone is only 9grams.....................
That is a very thin cone.

An enclosure than better disperses the back wave would be a good place to start.

Norman
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Old 30th July 2008, 09:52 AM   #3
Piek is offline Piek  Europe
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If that "Horn" is just working in the lower frequencies, not increasing response till 800Hz I would try to listen at 15 degree or use 6,8Ohm+4,7uF+0,47mH parallel connected in serial to the driver. But that will be "trial an error" maybe.


-Micha
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Old 30th July 2008, 09:55 AM   #4
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Default Re: Hemp Acoustics FR8C in Angular Spiral Enclosure

Quote:
Originally posted by cjctan
Hi All,

I have completed a pair of angular spiral enclosures and mounted with Hemp Acoustics FR8C.

Listen to it after run-in for 8 hours and I am still a bit dissapointed by the low frequencies and some shouting heard for high frquencies.

I would appreciate if anyone can give me some pointers on how to improve the sound?

Well, I don't know about anyone else, but I'm not all that surprised.

Re the LF, you provide no dimensions, but from the picture, that box is very unlikely to have sufficient volume to provide much LF gain. Solution is a bigger box, or a subwoofer. Also, unless they're hard up against a wall, you'll probably be loosing quite a bit through baffle-step loss -some Eq, either active or a passive BSC circuit will help a bit there.

Re the HF, the FR8c is no shrinking violet at the top end -it does have a rising response, like many FR units, so you can either toe it in heavily, Eq it flat, or insert a shelving filter to take things down a bit to your taste.

FWIW, give the drivers a few more hours to loosen up, but you should already have about 95% of the end performance.
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Old 30th July 2008, 12:39 PM   #5
cjctan is offline cjctan  Singapore
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Hi Norman,

Thank you for your reply and information!


" I dont see much damping in those boxes................."
I did not put any damping other than a piece of 5mm cork sheet on the back wall above the steps (around the back of the driver)


" Parallel walls are bad, and same dimensions (width = depth) is bad too. "
WOW! You are spot on! the width is equal to depth
which I just bindly followed the plans


" or if you have speaker away from front wall, do you have any baffle step compensation ? "
Currently no baffle step compensation. I guess i will google more on this topic.

" Oh, I just noticed you only have 8hrs on them, maybe sound will improve (more detail as surround/spider stretch a bit). "
I am keeping my fingers crossed and hope that the sound will improved, however, it needs a drastic and dramatic improvement

" An enclosure than better disperses the back wave would be a good place to start."
The back wall is already fixed onto the cabinet as the picture was taken before I sealed the back wall Therefore the current listening experience is from a pair of fully enclosured boxes.
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Old 30th July 2008, 12:39 PM   #6
cjctan is offline cjctan  Singapore
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Quote:
Originally posted by Piek
If that "Horn" is just working in the lower frequencies, not increasing response till 800Hz I would try to listen at 15 degree or use 6,8Ohm+4,7uF+0,47mH parallel connected in serial to the driver. But that will be "trial an error" maybe.


-Micha
Hi Micha, Thanks for your reply.

I am using this pair as my main speakers and do not intend to add any sub due to space constraints.......
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Old 30th July 2008, 12:39 PM   #7
cjctan is offline cjctan  Singapore
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Default Re: Re: Hemp Acoustics FR8C in Angular Spiral Enclosure

Quote:
Originally posted by Scottmoose



Well, I don't know about anyone else, but I'm not all that surprised.

Re the LF, you provide no dimensions, but from the picture, that box is very unlikely to have sufficient volume to provide much LF gain. Solution is a bigger box, or a subwoofer. Also, unless they're hard up against a wall, you'll probably be loosing quite a bit through baffle-step loss -some Eq, either active or a passive BSC circuit will help a bit there.

Re the HF, the FR8c is no shrinking violet at the top end -it does have a rising response, like many FR units, so you can either toe it in heavily, Eq it flat, or insert a shelving filter to take things down a bit to your taste.

FWIW, give the drivers a few more hours to loosen up, but you should already have about 95% of the end performance.

Hi Scottmoose, Thanks for your reply!

The dimension of the cabinet is 550mm (Height) x 320mm (width) x 320mm (depth) and I am using a 3/4" marine plywood.

I guess i will search more information on BSC circuit and try it out. May I know what is a "shelfing filter"?

I understand the new drivers needs some break-in time. As what you have said, I am expecting the sound to be close to its full potential at this point of time, therefore I am disappointed by how it sounded now.
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Old 30th July 2008, 12:54 PM   #8
ttan98 is offline ttan98  Australia
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Default Re: Hemp Acoustics FR8C in Angular Spiral Enclosure

Quote:
Originally posted by cjctan
Hi All,

I have completed a pair of angular spiral enclosures and mounted with Hemp Acoustics FR8C.

Listen to it after run-in for 8 hours and I am still a bit dissapointed by the low frequencies and some shouting heard for high frquencies.

I would appreciate if anyone can give me some pointers on how to improve the sound?

I would appreciate if anyone can give me some pointers on how to improve the sound? [/B][/QUOTE]


Hi,

I got a pair on loan from a friend, this is what I found, see attached photo. Please note the following:

1. driver mounted on an OB.
2. the FR is quite different from published FR from
manufacturer
3. I use this driver as mid range below 3.5Khz
sound good,due the Hempcone.
4. I won't use it as a full ranger, esp the top-end is erratic.
5. Costs more than the Fostex 167E or 207E


Hope this photo helps to explain what you found.
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Old 30th July 2008, 01:36 PM   #9
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Hmm. I make that 56.32 litres assuming those dimensions are internal, however a goodly portion of that volume will also be taken up by the internal panels. Nowhere near enough IMO for this unit. Where did the plans come from? I might be able to take a proper look at it to see what's happening (although I've got a fairly good idea as-is).

FWIW, the parallel cab. walls in this box won't be as much of an issue as it would be, in, say, a BR, given the convoluted path the airflow takes.
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Old 30th July 2008, 02:20 PM   #10
cjctan is offline cjctan  Singapore
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Default Re: Re: Hemp Acoustics FR8C in Angular Spiral Enclosure

Quote:
Originally posted by ttan98



I would appreciate if anyone can give me some pointers on how to improve the sound?

Hi,

I got a pair on loan from a friend, this is what I found, see attached photo. Please note the following:

1. driver mounted on an OB.
2. the FR is quite different from published FR from
manufacturer
3. I use this driver as mid range below 3.5Khz
sound good,due the Hempcone.
4. I won't use it as a full ranger, esp the top-end is erratic.
5. Costs more than the Fostex 167E or 207E


Hope this photo helps to explain what you found. [/B][/QUOTE]

Hi, Thanks for the information.

Is the driver that you have from Hemptone?
In fact, I have read that the Hemp will sound very nice in OB design. I am using it in a small room which does not allow me to use OB design.

I guess I have chosen the wrong driver for my 1st pair of FR speakers
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