sealed fr125s - stuffing and filters - diyAudio
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Old 21st February 2007, 09:14 PM   #1
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Default sealed fr125s - stuffing and filters

Hi Everyone,

I am building a pair of sealed enclosures for a pair of fr125s - basically the 7L reflex box, 3/4" baltic birch, no port. This is my first loudspeaker project (aside from a car subwoofer.) So I've got a couple of questions:

1. Stuffing: I am most concerned with the back wave reflecting off the back of the cabinet and returning delayed through the cone. I can't cut angles, (a router is the only tool I have out here) - what do I do to prevent this? Current plan is to use pillow stuffing, fairly tightly compressed along the walls, with looser stuffing below the brace in the bottom of the cabinet, and some empty space immediately behind the driver. Will this be sufficient? Should I line the walls with carpet pad instead?

2. Filters: there are some filters floating around for the 7L reflex box: a broad 'notch' around 1500hz, and a narrower notch around 7000hz. Will these work with the sealed enclosure as well?

Appreciate any advice!
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Old 22nd February 2007, 06:29 AM   #2
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Hi,

try this filter for a closed box (with 6dB high-pass). It is in German and "a / b / c / d" are the filter values. The designer is "cyburgs" from Austria - some of you might know him. The plan is free for private use, commercial use only on request!

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Thorsten
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Old 26th February 2007, 10:46 PM   #3
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Thank you validator.

I finished the enclosures this past weekend (except for the roundover on the baffles and trimming the baffle and back flush with the rest of the box. They sound pretty good right now without any filters, but I'm wondering if they could be improved.

I notice that Cyburgs design has a 7" baffle - mine is based on the CSS design, only they are left sealed right now. Similar displacement, but 6.5" baffle width. This would push the baffle step up to a higher frequency, right? Will the filters still work?

Will the notch filter in cyburgs design work for a narrower baffle? Does the notch require the 470uF cap as well, or is that just to extend f3?

Attached some pictures; one of the speakers, one of my workshop. My wife did permit me to glue up the boxes in the apartment, but any of the messy stuff had to be done outside. Thankfully, temperatures have been a little warmer lately.

Stuffed the bottom half of the enclosure and back wall with a poly-fil product that looks like insulation (its sold in sheets) - this made life pretty easy.

Any tips for finishing baltic birch? I like the look of them now, but I think they might look nice in a dark walnut or something similar...
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Old 26th February 2007, 10:48 PM   #4
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And my workshop.
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Old 27th February 2007, 05:23 PM   #5
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Andrew,

Great work!

I like your workshop. Very similar to mine! I face north, so sometimes it gets a bit nippy. However, occasionally I can see the Northern Lights!

How do you like them? I'd love to hear them. I am very pleased with the FE127E.

Cheers,
Gio.
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Old 27th February 2007, 07:54 PM   #6
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Hi Gio,

The speakers sound pleasant, but I think they can be improved. I have a pair of commercial speakers that I compared them to - my goal was (and still is) to match or better their performance.

I think there may be an opportunity to improve the sound with filters, adding a port to the box, or adding a tweeter. My next project is going to be a measurement microphone, so I can identify areas that can be improved.

Is your offer for a mini meet still open? I'll send you an e-mail.
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Old 28th February 2007, 12:40 AM   #7
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Filters can be tough. Sometimes I find that while they may give you a flat response, you can loose that full range magic.

I have a couple of tweeters and a bunch of caps you can try.
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Old 28th February 2007, 01:08 AM   #8
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I have FR125S' in a 7L box. I found that sealed they sounded constipated. I believe most of the recommendations are for a 10-14L sealed box. I've never heard that size, but I wasn't happy with the 7L sealed.

I don't know about that big filter on the FR125S. Pretty much ruins the directness of a full-ranger? I haven't heard mine with a filter. I just use them a foot from the wall, so I don't need BSC. If you're going to add a tweeter, again you'll spoil the full-range quality IMO.

If you don't want to try a larger box, I suggest you try a stuffed port. That's what I'm using now, and I love the sound, as long as you don't get carried away with the volume.
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Old 28th February 2007, 03:32 AM   #9
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Thanks for the advice. I have some ports and foam plugs that I could install; might be worth a try.

Did some more listening tonight. Certain music sounds great on these speakers - anything simple and well recorded. Once there are more than three instruments, echo, or complex sounds, everything seems to blur together. But simple music sounds pretty good.

My commercial speakers seem to be a lot more forgiving of lower quality recordings.
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Old 3rd March 2007, 02:56 PM   #10
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Default Port Tube

I'm going to install the port tube that came with the kit this weekend. It's the CSS flared port - looks something like this:

Click the image to open in full size.

I'm a little confused by the flanges at the back of the port. The flanges are 3/4" long - same as the wall material that I'm using. Should I cut the hole to the OD of the flange, or to the OD of the pipe, and then cut slots into the wood for the flanges to seat in?
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