fiberglass bookshelfs

[hoboham 10+ year member]

So I have been working on a nice pair of bookshelf speakers for my girlfriends dorm room. i wanted to impress so im going all out.

i picked up a pair of klipsch 6.5-inch IMG woofers, the grey ones

a pair of the Dayton DC28FS-8 1-1/8" Shielded Silk Dome Tweeters

and a pair of Port Tube 1-1/2" ID x 4" L Flared

edit:

13 by 11.5 by 8.5 so

crossed at 2.2k

so far i only have the wood done but id like to see if im headed in the right direction

//content.invisioncic.com/y282845/emoticons/laugh.gif.48439b2acf2cfca21620f01e7f77d1e4.gif

i braced the hell out of these, even got my girlfriend to stand on them .

so next step is glass, maybe some sanding first. but any advice on making this turn out right?

i have 2 small size aluminum fin rollers, brushes, premium 440, ton of chopped mat, and 5 yards of fishman mold fabric.//content.invisioncic.com/y282845/emoticons/crazy.gif.c13912c32de98515d3142759a824dae7.gif

but let me know what you think, its my first real project and i really want this to turn out

Click to read more...

 

[Captin Jack 10+ year member]

those look like they will turn out nice

what kind of airspace do you have going on there

 

[hempy 10+ year member]

I like your organization methods. Looks like my workspace.

I would have rounded over a lot more of the edges, but that's just how I do my stuff usually. I find fine edges are hard to keep fine, and I always wind up spending hours with teh bondo, but those are looking pretty clean as they are.

 

[SubNit 10+ year member]

Looks like your off to a good start, pretty stoked to see how it's going to look when it's all finished. As for advice, stretch the fabric tight so that theres no sagging and just go for it. Judging by your woodworking skills and attention to detail I don't think you'll have a hard time

How do you plan on finishing it? Is this your first glass project?

 

[hoboham 10+ year member]

hey thanks //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

yea its a hell of a mess lol

o and the crossover is at 2.2k

yea they are 13 by 11.5 by 8.5 so .735 cu if it was a rectangle so im assuming less

i think the port comes around 44, kinda low for bookselfs but i won hurt

yea i was planning on it but then i got lazzy lol, and the edges look really nice from tests ive done, especially the triangle shape on the top

 

[hoboham 10+ year member]

yea ill be sure to stretch her out real good lol as always jk

my only concern is attaching the fabric at first. I've seen everything from speed stick to hot glue lol so im not sure

its going to be painted a teal-ish with possibly black carpet on the back and bottom.

yea this is a first but definitely not the last, i bought enough supply's for 3 more at least lol

 

[hempy 10+ year member]

No flush mount on the woofer as planned?

 

[hzsogood 5,000+ posts]

no flush mount? what kind of crossover you using

 

[hzsogood 5,000+ posts]

hey thanks //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gifyea its a hell of a mess lol

o and the crossover is at 2.2k

yea they are 13 by 11.5 by 8.5 so .735 cu if it was a rectangle so im assuming less

i think the port comes around 44, kinda low for bookselfs but i won hurt

yea i was planning on it but then i got lazzy lol, and the edges look really nice from tests ive done, especially the triangle shape on the top

nevermind... f'n computer is lagging

 

[PV Audio 5,000+ posts]

While I can give you points on originality, as far as the actual enclosure performance goes, it's going to be seriously lacking:

1. Do not ever make a hifi speaker out of fiberglass if you can avoid it. It does not damp well enough at all and will almost certainly resonant at higher frequencies. You don't notice this in car audio because your main frequencies are low, but you're reproducing all audio octaves with these speakers and that will resonate. There is a reason why people build enclosure 1.5" thick walled all around. The enclosure is supposed to be an airspace, nothing more. It isn't even supposed to hold the driver in a conventional sense. In fact, people sometimes put floating washers on the mounting holes to isolate the cones from the enclosure itself. Vibration is bad.

2. You're firing your tweeters and midrange at one another. Unless you're doing a Mirage type speaker which uses a omnidirectional dispersion pattern, this is going to be atrocious for imaging. Your tweeter outputs sound spherically, and it is going to diffract all over your woofer's baffle. More importantly. depending on your x-over point, you might end up with some serious beaming issues from your midrange and if your mid and tweet are firing at one another, you're going to get a lot of response holes.

Perhaps you thought that it'd be a good idea to angle the baffle back because you've seen speakers like these:

Notice that they are angled but the tweeter and midrange are at the same angle. Why do people do this? Well, loudspeakers have two things: a zero delay plane or ZDP and an acoustic center. On a normal loudspeaker, with just a simple first order butterworth x-over, you will have a response peak at a few degrees above the on-axis plane (ear level), or a few degrees below if you wired your tweeter/mids out of phase. That causes two things: time delay, and an on axis response that is angled away from the listener. The time delay is because your lower frequency drivers' ZDP is going to be behind the high frequency driver merely due to its size. That causes the response to peak at an angle towards the high frequency driver since the information from it gets to the listener later, and because of the off-axis response tilt, your "zero" plane will be a few degrees below whatever peak there is in output, and thus the on axis response will actually be angled towards the LF driver.

By angling the baffle, you counter-act both of those. You can accomplish the same thing by using a crossover network like a Linkwitz-Riley alignment that accounts for that but otherwise, your speakers need to be resonating from the same ZDP (the exact same plane) and need to have the same acoustic center (where the "center" of the sound appears to be from the loudspeaker). The further apart they are on the baffle vertically, the more angles between the tweeter and midrange and the distance between the two drivers as far as depth (tweeter on baffle, woofer mounted behind baffle for an example), the more issues you'll have.

I'm sorry if that doesn't make sense, but unless you want me to get into crossover theory, then I think that's the best that I can do //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[hoboham 10+ year member]

naw sadly no flush mount i made the rings in such an order that getting the flush mount centered would be impossible //content.invisioncic.com/y282845/emoticons/crap.gif.7f4dd41e3e9b23fbd170a1ee6f65cecc.gif

unless there is a bit that can cut the shape i need, might be

yea that makes sense, ah i wish i would have talked to you earlier, i was focused on static structural support, looks and at least an expectable level of performance.

im not to worried about imaging issues manly because its going to be used in a dorm room, placed were ever it is most convenient.//content.invisioncic.com/y282845/emoticons/crazy.gif.c13912c32de98515d3142759a824dae7.gif and definitely slightly more "show" than "go"

it sucks that the tweeter is going to sound even worse because as it is it really doesn't fit my tastes, but it has me interested to hear more on good imagining techniques. i know from ele that as you go higher in frequency factors once negligible become very important and i have only heard bits and pieces.

so one effect of slanting the hf is to add distance, therefore the phase would lag but in such a way to be in time with the LF, makes sense, but are there any other implications that i am missin?

o i did the Linkwitz-Riley alignment but i couldn't do a Zobel network because i have no parameters on the woofers //content.invisioncic.com/y282845/emoticons/crap.gif.7f4dd41e3e9b23fbd170a1ee6f65cecc.gif

and i wouldn't mind getting into crossover theory i am studying to be a mechanical engineer but my favorite class has been circuit design go figure //content.invisioncic.com/y282845/emoticons/laugh.gif.48439b2acf2cfca21620f01e7f77d1e4.gif

o and i really appreciate the input honestly i would have never considered all of these factors, really glad i posted

 

[Blue Fury 10+ year member]

naw sadly no flush mount i made the rings in such an order that getting the flush mount centered would be impossible //content.invisioncic.com/y282845/emoticons/crap.gif.7f4dd41e3e9b23fbd170a1ee6f65cecc.gifunless there is a bit that can cut the shape i need, might be

yea that makes sense, ah i wish i would have talked to you earlier, i was focused on static structural support, looks and at least an expectable level of performance.

im not to worried about imaging issues manly because its going to be used in a dorm room, placed were ever it is most convenient.//content.invisioncic.com/y282845/emoticons/crazy.gif.c13912c32de98515d3142759a824dae7.gif and definitely slightly more "show" than "go"

it sucks that the tweeter is going to sound even worse because as it is it really doesn't fit my tastes, but it has me interested to hear more on good imagining techniques. i know from ele that as you go higher in frequency factors once negligible become very important and i have only heard bits and pieces.

so one effect of slanting the hf is to add distance, therefore the phase would lag but in such a way to be in time with the LF, makes sense, but are there any other implications that i am missin?

o i did the Linkwitz-Riley alignment but i couldn't do a Zobel network because i have no parameters on the woofers //content.invisioncic.com/y282845/emoticons/crap.gif.7f4dd41e3e9b23fbd170a1ee6f65cecc.gif

and i wouldn't mind getting into crossover theory i am studying to be a mechanical engineer but my favorite class has been circuit design go figure //content.invisioncic.com/y282845/emoticons/laugh.gif.48439b2acf2cfca21620f01e7f77d1e4.gif

o and i really appreciate the input honestly i would have never considered all of these factors, really glad i posted

You're thinking that these need so much consideration in that area. They look nice tho