diyAudio

diyAudio (https://www.diyaudio.com/forums/index.php)
-   Full Range (https://www.diyaudio.com/forums/full-range/)
-   -   Frugel-Horn Mk3 (https://www.diyaudio.com/forums/full-range/172605-frugel-horn-mk3.html)

Bob Brines 3rd October 2013 12:49 AM

Not having to worry about ever seeing a CNC machine, I use the direct approach. I have THIS circle jig attached to a Bosch 1617 router. The jig is infinitely adjustable with a vernier dial as does the plunge adjustment on the router. I mark out the center hole and a radius of the rabbet on either side of the center. I put a 3/4" straight bit in the router, adjust the cutting radius and have at it. Then I turn the work piece over and do the same for the through hole, this time using a 1/4" spiral bit. Yes, I do a test cut before I commit to the actual work piece.


Bob

chrisb 3rd October 2013 07:07 AM

Bob, of course there are probably several methods to achieve the same results, but note that as a potential first time project for a "complete woodworking novice" the total investment in tools and jigs that any of us might recommend could well be greater than the cost of ordering a kit from a local CNC shop. Flat packs do keep some of us in business :D

Bosch 1617 with plunge base - nice rig, and the vernier depth adjustment would certainly ensure accuracy and ease of operation = $250 - 280?

M-power router jig - actually a pretty cool looking jig, maybe time time for me to update my tool box = $80

While I understand you're not doing ellipses that much any more, when you did, what did you use? Rockler makes a pretty cool jig for circles and ellipses (up to much larger than most of us would use for speakers)

http://www.rockler.com/product.cfm?p...bSelect=Videos


quality 3/4" dual flute plunge bit $40-60? Unless you're not planning on them lasting, cheap bits are false economy at best, particularly when dealing with high density plywood

1/4" spiral bit $20 - 30?

jemraid 3rd October 2013 09:01 AM

Hello C & B,

You are quite right about the tools costing more than the boxes, your bits cost more than the sheet of MDF I used :-)

Cheers - Jim

Bob Brines 3rd October 2013 02:41 PM

Quote:

Originally Posted by chrisb (https://www.diyaudio.com/forums/full-range/172605-frugel-horn-mk3-post3653414.html#post3653414)
Bosch 1617 with plunge base - nice rig, and the vernier depth adjustment would certainly ensure accuracy and ease of operation = $250 - 280?

$208 today at Lowe's

Quote:

While I understand you're not doing ellipses that much any more, when you did, what did you use? Rockler makes a pretty cool jig for circles and ellipses (up to much larger than most of us would use for speakers)
I print out a 1x copy of the ellipse (included in the plans packages) and glue it to a piece of 1/4" of whatever. Jig saw and sand paper (disk) to shape. The print also has the center marked, drilled out 1/8". The pattern is screwed to the back side of the work piece, rough cut with a jig saw (band saw if you have one), and then to the router table. If you choose, you could rough cut the work piece on the router table with a guide ring and a spiral bit. Continuing, finish cut the work piece with a straight pattern bit and then a 3/4" round-over bit. That last item can be a bit expensive if you want a quality bit.

If you are only making one pair of speakers, you might not want to do the pattern, but since I do many speakers, the pattern speeds the process.

Bob

chrisgoeslive 3rd October 2013 10:18 PM

Well what I get from all this is that it is possible to rebate a through hole, with the right equipment and know how. Right now I don't have either of these qualities. What I may do is get the kit from custom cans and then see if I can get someone to rebate the two holes for me. Or alternatively I could simply surface mount the Alpairs, though this is a less preferred option.

Does anyone have any suggestions for a suitable amp to go with these speakers? I have seen suggestions that T-class amps are well suited. I am considering building something from scratch, though I saw recommendations for this amp:-

Class-T-Amp-2020-m-mk2, Autocostruire

also this kit:-

AMP6 T-Amp DIY Class-T Amplifier Kit from 41hz.com

EdKennedy 3rd October 2013 11:41 PM

1 Attachment(s)
I went a different approach to mounting the driver. I simply mounted it on the face of the front. you can then use a cheap portable sabre saw to cut the hole. I then used a rotary rasp bit in a drill to bevel the back side of the hole (Very Important).
To deal with the lack of a rebate, I used a solid piece of plywood for a grille frame and made the thickness around the hole in it flush with the extended speaker bezel.

Now let's bring on the grille vs. no grille debate! :D

Another hint which is buried deep in these forums; Make the top removable. It allows you to adjust the stuffing, or in my case, retighten a terminal post which came loose.

chrisb 4th October 2013 03:40 AM

c g l :

Either of those kits would work fine if you're more comfortable building an electronic project than speaker enclosures - by many accounts the 41Hz are particularly great performers.

Of course I could get all snarky and suggest that nothing less than a tube amp would to the Alpairs justice, but that's just not true.

What I will say is that I've tried a few Class-T amps (commercial) chip amps (AudioSector gain clones, etc) and over the years, and for bang for the buck, something like the little Topping TP30 is quite a sweet little unit. Bob is even more enthusiastic about his higher powered TP60, and that's a good enough recommendation for me to eventually try one of those myself - a guy can't have too many amps - as long as they're not all the size of a Jolida 302 etc.

As for rebating of the Alpairs or for that matter any wide dispersion full range driver with a thick mounting flange being "optional" - I'd differ with that. At the very least, perhaps the custom cans boys could cut a separate piece of 9mm or so material with a hole to fit the driver flange that could be laminated on the the front of the baffle - you could even make it a "feature" . You'd just need to decide whether to use the extra bezel ring on A7s or not. FWIW, I don't on the 7s myself, and would be surprised if I could hear the difference - other folks might.

cbiern 4th October 2013 04:13 PM

Quote:

Originally Posted by Bob Brines (https://www.diyaudio.com/forums/full-range/172605-frugel-horn-mk3-post3651972.html#post3651972)
Well, you will always find a use for the rest of the 18mm sheet!

I tend to use 12mm material, which makes the problem worse. I just double the baffle or portion of the baffle, giving me 24mm material. Using 15mm material, I would double the area behind the driver. As long as you chamfer the driver hole, all will be well. laminating two 15's is a lot easier than laminating a 15 and a 5.

Bob

Will adding a piece behind the baffle mess with the cabinet volume sort of like adding stuffing that you are not able to remove or adjust?

chrisgoeslive 4th October 2013 04:18 PM

Quote:

Originally Posted by EdKennedy (https://www.diyaudio.com/forums/full-range/172605-frugel-horn-mk3-post3654183.html#post3654183)
I went a different approach to mounting the driver. I simply mounted it on the face of the front. you can then use a cheap portable sabre saw to cut the hole. I then used a rotary rasp bit in a drill to bevel the back side of the hole (Very Important).
To deal with the lack of a rebate, I used a solid piece of plywood for a grille frame and made the thickness around the hole in it flush with the extended speaker bezel.

Now let's bring on the grille vs. no grille debate! :D

Another hint which is buried deep in these forums; Make the top removable. It allows you to adjust the stuffing, or in my case, retighten a terminal post which came loose.


Nice job on those speakers - what finish have you used on the cabinets is it veneered?

chrisb 4th October 2013 05:25 PM

Quote:

Originally Posted by cbiern (https://www.diyaudio.com/forums/full-range/172605-frugel-horn-mk3-post3654827.html#post3654827)
Will adding a piece behind the baffle mess with the cabinet volume sort of like adding stuffing that you are not able to remove or adjust?


if the thickness and length of panel I envision Bob is suggesting and I've used myself (i.e. no more than 1/2" and full width, but extending only a couple of inches below the through hole), not significantly enough to impact - excess stuffing placed directly behind a driver such as the Alpair 7 or CHR70 would likely have a more deleterious effect

edit; yet another addendum - with 18mm - 3/4" baffles, I don't personally use anything thicker than 9mm 3/8" for those extra rear plates - but others might want to


All times are GMT. The time now is 08:11 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2021 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 17.65%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2021 DragonByte Technologies Ltd.
Copyright ©1999-2021 diyAudio

Wiki