Aperto cabinet design for Hemp FR8C - diyAudio
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Old 24th August 2007, 06:40 PM   #1
rpfunk is offline rpfunk  United States
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Default Aperto cabinet design for Hemp FR8C

I have been struggling with a decision for my first speaker project. I finished putting together the k-502 Tube amp kit from Antique Electronic Supply. Since it is only an 8 watts and is my first speaker (and tube amp) project I wanted something fairly simple and inexpensive to build. I listen to mostly rock and need some bass to the speaker. From what I have read on previous posts the Hemp FR8C has more bass than the Fostex does. Anyway the Hemp website has a bookshelf speaker design that looks like it would work well for me but the port is in the back.
http://www.hempacoustics.com/kits.php (Aperto design)
Is there a problem with moving the port to the front since I will have to place the speakers close to a wall? I know that I will loose some bass by not building a bigger cabinet but the the way the room is laid out I would have trouble putting the speakers on the floor. The room is about 13' x 17'. Buy the way this is great sight and have enjoyed many hours browsing.

Thanks
Robert
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Old 24th August 2007, 09:39 PM   #2
pjanda1 is offline pjanda1  United States
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I think the FR8C would be a great speaker for you. Moving the port to the front will pose no problem. If you can stand a bigger bookshelf than the Aperto, you'll reap benefits. If the maximum dimensions you can tolerate/place exceed the Aperto in volume, you can play around with speaker calculation programs (folks here can help too) and get the correct port size. When you think about dimensions, I'd recommend the biggest (widest) baffle you can tolerate. I had my Hemps in a bigger (but still not floor standing) vented box for awhile. I found that getting it pretty close to the wall (and the wide-ish baffles I used) greatly help the midbass if you aren't going to use baffle step compensation.

While you're in the planning stages, think about budgeting for nice plywood (like Baltic Birch). It sounds good, is nicer to work with than MDF, needs a little less bracing and finishes decently with little effort.

Finally, I think the Hemps in a bookshelf and you're little amp will sound great. However, don't expect to acheive anything close to concert level SPL's with a fullrange bass reflex and 8 wpc. If you want something loud and efficient, you'll need to look at a much bigger cabinet (like a back horn or BIB). I just offer this as you listed your main listening preference as rock. Most of the time I listen around 85-88 db, and the Hemp BR had no trouble with that.

pj
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Old 25th August 2007, 02:51 AM   #3
Nanook is offline Nanook  Canada
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Default Aperto

is a good design. I use the Hemp Acoustics FR8c drivers in a 20 litre box.

No deep bass, but very ncie sounding. Haven't measured, but I think -3dB in the 40ish Hz range.

It moves right along. I think if you need more bass, a BIB or similar may be required.

edit: did a quick model to verify the design. In my case, I get -3dB at 42 Hz, with a rear facing vent. When I get set up for measurements, then I can verify.
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Old 25th August 2007, 09:05 AM   #4
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I did an MLTL with this driver for a friend on another board a week back, if this is any interest. Not being able to drive a CAD programme to save my life, I modified one of MJKs drawings (hope you don't mind Martin). The depth dimension hasn't come out too well: it should read 14in (all dimensions internal).
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Old 25th August 2007, 09:06 AM   #5
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MathCad predicted response for above enclosure:
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Old 25th August 2007, 11:39 AM   #6
pjanda1 is offline pjanda1  United States
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Nice, but I'm having trouble reading the depth. Is that 24"?

pj
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Old 25th August 2007, 12:17 PM   #7
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Depth is 14in; all dimensions given are internal. I noticed it'd come out blurred for some reason just after posting, so I edited it to clarify that size. You must've had the bad luck to catch it right before I did. Sorry about that.
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Old 25th August 2007, 05:24 PM   #8
rpfunk is offline rpfunk  United States
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Now those are some quick responses. I thought it would take a couple of days at least.

pjanda1 - I'll have seen several references to the speaker applications that you mentioned and will spend some time on scaling up the speakers as much as I can now that I know I can put the port in the front. When I jumped into this DIY audio thing I figured out I would start out small and work my way up (the reason for the 8 watt PP amp inexpensive kit). I'm glad you mentioned the Baltic Birch, I was leaning in that direction.

Nanook - I read your reviews on the Hemps and Fonkens a couple of weeks ago and was very impressed with both articles. Your reviews set me down the Hemp FR8C road and gave me a starting point after many hours of browsing the forums. The Apeto is so well documented on the Hemp site it gives me a good base to start with.

Thanks to both of you for the info. Finally I will be able to get started!
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Old 27th August 2007, 10:29 PM   #9
Nanook is offline Nanook  Canada
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Default reviews...

Yes, I do write for
Affordable$$Audio , I'm stew nelless

I spent quite a bit of time with the Fonkens and am completely impressed with them. I'm also impressed at the reasonnable amount of money the modded drivers from planet10 -hifi are.
The FR8c are mine own, and I had since had mr planet10 himself do some surgery to them (not sanctioned by Hemp Acoustics, nor approved). I feel there is an improvement to the drivers themselves.

I am happy that you found the articles helpfull, I never really know if anyone reads mystuff because it can get preachy ("from the puilpit"), and I am pretty opinionated.
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Old 27th August 2007, 11:14 PM   #10
rpfunk is offline rpfunk  United States
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Scottmoose - Thanks for the design. I measured the space I have and I just can't get a speaker that tall into the space I have. For now I think I am going to have to lose some bass and use a smaller enclosure. The problem is that I have a projection TV taking up 1/3 of the wall and a fireplace and built in bookshelf taking up the rest. The room is far from ideal. I have been remodeling so I am planning on building a bigger enclosure in the future and moving everything to another room.

Thanks
Robert
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