Baffle Offset again.

[JoshK]

Hi Jon, Thomas, et al,

I have been pondering, thinking, sketching, etc. I really like the baffle offset idea and argument for the tweeter and the midbasses being offset instead of centered to reduce diffraction affects. However, I was interested in your take on this argument for why one should keep the tweeter & mids inline vertical and offset together?

Basically it is argued that keeping the tweeter & mid inline vertically creates better vertical polar response and well as horizontal polar response. I wonder if it then causes problems with c-t-c spacing. At the 1400hz xo point in the Arvo Pärt, I think you said the free space was 11".

Of course there is nothing like building a bunch of different baffles and testing for myself.

Cheers,
Josh

[JonMarsh]

Hi Jon, Thomas, et al,


Of course there is nothing like building a bunch of different baffles and testing for myself.

Cheers,
Josh

There you go- do it the hard way, like we usually do!


Seriously, with the tweeter crossover frequencies I usually use, the difference in off axis response due to the offset of the tweeter on the panel is pretty muc a non-starter. But controlling/distributing the diffraction and baffle step issues are important where ever you choose to cross.

HOWEVER, I'm always open to persuasion... just don't think it's an issue worth spending a lot of time on right now, in comparison to all the other things that need to be done...

OTOH, I'm still wonding how Darren came up with his version of the RS180/RS28a MTM crossover with it's big dip in the presence range on axis- haven't gotten around to modeling it yet, though I've got all the data dumped to the laptop.

Yesterday I was comign across references from an MS guy who posts on AVS Forum, taking his 2 month sabbatical he's qualified for after working 7 years at Micro$oft; and another acquaintance I know at Intel who took a six month Sabbatical last year.... think of what I could get done with speakers and other projects with six months off!?!??!?!?!


~Jon

[JoshK]

It isn't worth fussin about, but just wondered if you had a strong opinion/rationale on the matter.

I understand and feel the same way with your work schedule. At the ripe age of 29 (for two weeks anyway) I find myself the head of research for a large global investment management fund. I became where I am by default partly because my boss quit and other coworkers moved on. We should be 4 but are currently 1, me. So work is a bear sometimes. Add to this I am renovating my 1900 century home solely myself and doing numerous DIY projects (mostly electronic) and I feel much the same as you. I cannot get time to finish the projects I started and am always coming up with new ideas to try and fill up my non-existant time.

[JonMarsh]

Sounds very familiar, except I've got a bit over 20 years on you, and probably not as much energy!

~Jon

[Marzen]

.... with the tweeter crossover frequencies I usually use, the difference in off axis response due to the offset of the tweeter on the panel is pretty muc a non-starter. But controlling/distributing the diffraction and baffle step issues are important where ever you choose to cross.
~Jon

What a timely thread this is; what with me having some difficulties with finding specific ref's to edge diffraction and tweeter offsets. If someone could point me in the right direction for:
1) A good reference book for the 'little' details I need answered during design.
All of the basics seem well covered in several books. Without prior experience in designing speakers or even listening to several different types of alignments it's like trying to explain the color green to the blind. Below are some recent questions.
2) With offset tweeters, does it reside on the outside or inside edge of the baffle in relation to your seating position? (I'm going to guess the inside edge)
3) How do you determine precedence with power band response vs. off axis response? (Usage/preference/happy medium)

Cheers,
Marz
PS - after 2 hrs here, my brain feels like it ate to much!

[Paul W]

Reading the documentation for Paul Verdone's BDS spreadsheet provides some good insight. The spreadsheet itself is also very helpful for modeling specific implementations.

http://www.pvconsultants.com/audio/frdgroup.htm

There is another really great writeup somewhere on the net, I just don't remember where...Google is your friend!

[Paul W]

Here's Paul discussing innies vs outies...

http://www.madisound.com/cgi-bin/discuss.cgi?read=351274

[JonMarsh]

Thanks for chipping in, Paul. You pointed him just where I would have-

BDS has been a very useful part of my toolbox for many years, now. My hat's off to Paul Verdone- he made a very valuable contribution to the DIY community.

~Jon

[Marzen]

Big thanks guys. I like getting links for those answers that require a little more detail. I feel bad 'cause I wrote off the FRD after buying Sound Easy. Now I find I really like the little stand alone programs like BDS for quick answers. I could REALLY use a book of equations though; I'm more used to that & I may have to fly to Taiwan & could use that with SE on the laptop to make the flight more bearable (Wen Lie!). How is Dickason for a ref writer?
OT - I brought home a projector & screen to test my new hdtv cat5 extender this weekend. Preseason Browns game tonight! For you football fans - keep your fingers crossed that CBS invested in better NFL surround sound than the muddy, overly compressed mess that was last season. Perhaps they could sub it out to Fox Sports.
PS - Google is NOT my friend, it's more of a buddy. If it was a REAL friend it wouldn't give me so many different answers to the same question. It needs a quantize & verify string :a> C'mon! - 25,000 hits for BAFFLE DIFFRACTION? Anyway, time to make cheese dip for me & the welpen.

[dlr]

Baffle diffraction

25,000 hits for BAFFLE DIFFRACTION? Anyway, time to make cheese dip for me & the welpen.

If you're interested in diffraction reduction, you may find a couple of things at my site interesting. No equations, however.

There's the article called "Understanding Diffraction" by Andy Unruh that covers the basics and there are a couple of sections on using felt to control it.

If you're interested in offset baffles (not lateral, but horizontal on the Z-axis), you may also find an article on this in the June issue of audioXpress.

I always offset laterally as well, as Jon said, it's important. There's no substitution for reduction as part of the design. "Fixing" it in the crossover is a distant second IMO.

dlr

[Marzen]

Thanks for the additional info. Couple more questions now tho:
1) where can I pickup audioexpress? Borders, etc?
2) where's your site dlr? I'll take you up on that offer.
3) I'll keep searching for Andy's article, I was interested in another post by Jon on using felt.

Thanks again,
Marz

[dlr]

audioXpress has it

Thanks for the additional info. Couple more questions now tho:
1) where can I pickup audioexpress? Borders, etc?
2) where's your site dlr? I'll take you up on that offer.
3) I'll keep searching for Andy's article, I was interested in another post by Jon on using felt.

Thanks again,
Marz

I've never purchased it in a bookstore, though I'm sure some do carry it. You should be able to buy it as a back issue at the audioXpress.com web site.

I forget that my site doesn't show by default here. Go to:

https://www.speakerdesign.net

Regards,

Dave

[JonMarsh]

You can find AudioXpress in some, but not all, Borders. That's where I used to buy it "off the rack".

[Marzen]

Reprinted from Dave's site:
"I am an experimenter more than anything. I like to find out what makes something work (or not work, as the case may be). This has extended to speakers. I am at the point of doing design, from measurements to construction to final tweaking, but I still like to go back to taking something apart to see how it works..."

WOW! You're 10 steps ahead of me. I had planned on doing a similiar site to document what I've learned with spkr design. Gather & post info that pertains to what I'm working on, etc. Your opening paragraph above is even similar to mine. You're like my brotha from a different mutha. Thanks for sharing!

Marz

[dlr]

Do it

WOW! You're 10 steps ahead of me. I had planned on doing a similiar site to document what I've learned with spkr design. Gather & post info that pertains to what I'm working on, etc. Your opening paragraph above is even similar to mine. You're like my brotha from a different mutha. Thanks for sharing!

Marz

The more the merrier, as the saying goes. I also like "Just do it.". The only better 3 word sentence I can recall was from an engineering manager when he was made aware of a problem in the plant in which I worked. "Well...fix it!".

So, do it.

dlr

[Marzen]

So, do it.
dlr

Ok, I done did it, or at least got started. Amidst the swirling vortex of chaos that I call my life here's what I've got so far. Note I had to learn MS Frontpage to do this: http://akins.no-ip.info/
Note to self: I should take lessons on effective time management. I don't know how you guys find the time? Here's my short list for August:
1) finalize adoption - fly to Florida 3 days. Done
2) baby's 1st b-day party - Done
3) source laminate flooring from China. Done
4) repair broken garage door torsional springs. Pending
5) calculate new oven ramps for lead & lead free parts. Pending
6) German club Oktoberfest. Done (hic)
7) cut down tree & reroute phone line. Done
8) plumb a ng gas line to the grill. Done
I'm gonna need to bolt the fridge to the wall due to the growing 'to do' list.

Cheers,
Marz

[dlr]

I can't get the link to work

http://68.71.100.49:8080/Speakers.htm

The link has a problem. I deleted the 8080 and it still won't work.

[Marzen]

sorry, I'll try it from work. 8080 is my web server port. It resolves for me now, although there may have been some problems during the day as I use a vpn tunnel from work to access files Otherwise, http://akins.no-ip.info/ should take you to the home page.

[JoshK]

It worked for me three times over two days.

[Dennis H]

Works for me.