Wall mount design / questions

[eddo]

Hey all,

I'm thinking of trying my hand at designing a small wall-mount speaker. This would likely be used for satellites in a 5.1 system, or wherever I need a small set of decent speakers. I like Zaph's "Slimline Wallmount" design, however the Aura driver is out of stock, and I have no interest in using Aura drivers given the history of supply issues.

My inclination is to use the Dayton ND20FB-4 tweeter and RS100S-8 mid crossed over around 3.5kHz, with the drivers spaced as closely as possible.

The main question I have regards BSC. I know that with the wall-mount design there is minimal (if any) baffle step to account for. When designing the crossover, is there any use in simulating the baffle diffraction ripple and applying that to the infinite baffle frequency response? I assume that the small amount of ripple wouldn't even be worth adding to the response before Hilbert transforming to extract the phase, thoughts?

This will be my first attempt at actually designing a decent crossover, I don't expect that it will be perfect (especially given my lack of test equipment) but I'd like it to be as good as possible.

Ed

[jkrutke]

You can't simulate the ripple you will see from a wall mounted enclosure, or at least, there are no tools to do so at this time. You can simulate the baffle but not the wall reflection summing back into the design. You will have to build the enclosure and take measurements, then work with that.

For all budding designers, my first piece of advice is to get a measurement system going. I hope you didn't plan on skipping that step and trying to get into crossover design without it.

[eddo]

Thanks John. I hope to purchase some measurement equipment soon, but have been putting it off due to lack of a decent sound card (have only a laptop presently). Could anyone suggest a decent USB or Firewire sound card with low noise, wide bandwidth etc?

I'll probably be using Speaker Workshop for a while, so it would be great if the sound card was compatible with that.

[Dennis H]

E-MU Tracker USB 2.0.

http://www.emu.com/products/product.asp?category=610&subcategory=611&product=17511

Review of the older E-MU 0202 used with Praxis.

http://www.libinst.com/EMU%200202%20USB.htm

ARTA software: 10% (maybe 15% with the weak dollar) the cost of Praxis and 90% of the functionality.

http://www.fesb.hr/~mateljan/arta/

[eddo]

In case anyone is interested in building Zaph's wallmount design, the Aura drivers are on special at Madisound for $12ea.

At first I thought "cool, now I can build this design," forgetting that the Dayton Neo tweeter is now the ND20FB rather than ND20TB, so the tweeter filter is obviously not compatible. Zaph, is there any chance that this design may one day be updated to accommodate the ND20FB?

I think I'm going to buy some of the NS3's anyway, can't go wrong for $12.

[eddo]

Testing equipment

I''m looking into getting set up with some test equipment sometime in the next couple of months, and going with the equipment below. If anyone has any experience/suggestions with the following choices, it would be appreciated.

Sound interface: Tracker pre USB 2.0 audio interface. I like this option since all I have is a laptop, plus this thing has phantom power for the microphone (so I shouldn't need a separate preamp, right?)
Tracker pre

Microphone: jumping on the bandwagon with the Behringer ECM8000

Design software: Starting with Speaker Workshop, hopefully progressing to Soundeasy

Amplifier: Really not sure, very open to suggestions. The NAD C315BEE seems like a nice setup for a reasonable price. If anyone has a lower cost solution that would be great.

Ed

[ThomasW]

Everything looks fine. I'm not sure why you'd need a separate amp for testing. Most use the main amp or receiver in their system unless they're testing outside or remotely.

You'll want boom mic stand and don't forget a 20' or so mic cord

[eddo]

I have a Yamaha RXV620 receiver, and will probably use that. I think I'll characterize it a bit before using it for testing, I'm curious about the frequency response and distortion specs. Could just look them up, but whats the fun in that? Thats the beauty of working in a physics lab: all the lockin amplifiers, waveform generators, and oscilloscopes a DIYer could ever need. If only I could take the toys home to play with...

[ThomasW]

There are freeware PC based function generators and O-scopes. Obviously the scopes don't have the resolution of a high-end stand alone dual trace unit.

http://www.htguide.com/forum/showthread.php4?t=26544

[eddo]

In case anyone is interested, I just received a batch of the Aurasound NS3-193-8A drivers from Madisound that were on special. After looking more closely at Madisound's site about the NS3 special, I found out that they were being offered cheap since this batch came in with a crappy glue job on the surrounds. There is a bit of translucent white glue around the surround, but a bit of model car paint from the hobby shop makes it barely noticeable. It isn't perfect, but I doubt if anyone will notice unless its pointed out. I'll post some before and after pics later.

I also hooked up a couple to the WT3, the free-air parameters seem to be within spec, and Aura apparently tested them to be within spec as well.

Now I just have to figure out how to handle the tweeter filter to build the "slimline wallmount" design since the Dayton tweeter has been revised.

[eddo]

Images of NS3-193-8A drivers purchased on Madisound's special. Before: glue is apparent around the surround. After: much better after going around it with model car paint and a fine brush. Not perfect, but probably not terribly noticeable to most people.

[jkrutke]

In case anyone is interested in building Zaph's wallmount design, the Aura drivers are on special at Madisound for $12ea.

Yup, you're right, that design is only good with the T version of the tweeter, no longer in production. I need to pull it from the web site.

I intend to do another wallmount someday, probably with different drivers. I'm thinking of the Vifa DQ25SC16 and the MCM 55-3853.

I was surprised that Madisound had the NS3 back in stock, but then I saw it was a special purchase of sloppy glue surround blemishes.

[jkrutke]

Images of NS3-193-8A drivers purchased on Madisound's special. Before: glue is apparent around the surround. After: much better after going around it with model car paint and a fine brush. Not perfect, but probably not terribly noticeable to most people.

You could rear mount them also, with a 1/2" roundover.