Floorstand, 2 way, very low crossover(+with waveguide)

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A

Alexnick

Member
Joined 2005
Hi,

As I've seen on my previous post about Amphion Argon2, I'm wondering if
it is possible to do something pretty close, but as a floorstand!

So my idea is to take a good 8" speaker, put it in a 30-50Liter enclosure
and cross it as low as possible, with an waveguide tweeter!
I want a low F3(as low as possible, but without compromising the TRANSIENT
RESPONSE).


The are some problems though:
Choosing the right speakers to suit this design
Choosing the correct xover frequency
Harmonics coming through the port
Choosing the port position(front-firing, down-firing, rear-firing)
to achieve a compromise between bass response and harmonics coming
out through the port
Doppler distorsions that appear when there is a high xover point
Woofer's harmonic distorsions when going to upper frequency limit
Woofer's low frequency response
Woofer's off-axis response at high frequencies
Tweeter's low frequency response
Tweeter's harmonic distorsions when going to lower frequency limit
Calculating the horn dimensions

I'll write later the problems that I forgot to mention here!

First, I need some suggestions, for the speakers that would be suited
for the project!



Please write here every link that you think it might be helpful!
 
D

Dumbass

Member
Joined 2003
For the enclosure, I would go for a mass-loaded (i.e. vented) transmission line. You'll want a driver that has moderate Qts (.4 to .5-ish) and, of course, low Fs. Hi-Vi has a number of 8" drivers (partsexpress.com) that look promising.

To get some idea for how large the enclosure will be (1) do calcs for an alpha-TL from Rich Schultz's article and (2) model the enclosure as a simple bass reflex. Then fiddle with Martin King's worksheets and end up somewhere between (1) and (2).

http://www.t-linespeakers.org/readme1st.html
 
Timn8ter

Timn8ter

Member
Joined 2003
You're asking a lot from a tweeter to run that wide of a frequency range. Tweeters of that quality are not inexpensive. Additionally you'll need to use very steep crossovers if you're trying to take the tweeter all the way to the bottom of it's useful range. 200 Euro for 2 tweets, 2 woofs and crossovers, etc.? That's a tough one. Perhaps a BG ribbon with a woofer?
 
A

azrix

Member
Joined 2004
Pretty much any 7" or 8" woofer (even a few 10"ers) will work with the 1k-1.5k crossover frequency that most waveguides can give you. A bigger problem is the waveguide. Do you have a plan for that? Cutting a waveguide out of a piece of wood, like Amphion does, is not trivial and neither is the shape of the waveguide. There are a few waveguides available retail, but I don't know how easy they'd be for you to get a hold of. Once you do have a good waveguide and tweeter, the crossover needed to get the frequency response close to flat is much more complex than if you hadn't use a waveguide. You could get drivers for a decent three way with your budget. That's probably what I'd be looking at.

http://www.zaphaudio.com/hornconversion.html has some info.
 
M

mgoedeke

Member
Joined 2002
Why not go with a device which will actually work properly in a wavegudie in the first place? If the taxes are only so high for Europe, Bulgaria produces some quality comrpession drivers, BMS amongst them where Seas et al will have no chance against on a waveguide.

I myself am embarking on on a waveguide project, but for a 12" driver crossed around 1.2khz (forget about a dome tweeter having any chance there) and the woodwork seems like the biggest challenge for me atm. A solid solid piece of hardwood will warp and crack if you don't really know what you're doing and laminated kiln-dried wood is likely the best bet I recon.
 
Notax

Notax

Member
Joined 2004
Alexnick said:
Come on guys!
Any suggestions for the 8" and the tweeter?
Let's say you had 200 Euros(excluding the 40% taxes that I have to pay to get the speakers) what would you buy?
Click to expand...


Monacor SPH-200KE and DT-28N.

36-42 liter, BR

X-over: 6/12 dB
bass (in fase) - 1,8 mH
tweeter (in contra fase) - atenuation; paralel 6,8 Ohm, in order 5,6 Ohm, in order 6 uF, paralel 0.39 mH

good luck ;)
 
Ed LaFontaine

Ed LaFontaine

Member
Joined 2004
I'm with AJinFLA on this:
http://www.seas.no/seas_line/tweeters/H1212.pdf
Click to expand...
You need the metal dome.

I also agree on the midbass he suggests. An alternate to the SEAS midbass he cites would be the PE RS180. The SEAS would be more economical for you due to shipping and customs. Maybe better quality. The reverse holds true for those of us across the water.
Posted by asrix: Cutting a waveguide out of a piece of wood, like Amphion does, is not trivial and neither is the shape of the waveguide
Click to expand...
I agree here. Let's do it in spite of this. I can make your waveguides on my lathe. I can also shape the 30 ppi foam "refractive phase plug". You may have an alternate approach.

See my thread: http://www.diyaudio.com/forums/showthread.php?s=&threadid=41178
for formulas. There needs to be a routine developed that will plot full scale profiles from entered data: throat size, cut-off frequency, desired transition radius from waveguide to baffle, etc. Once the profile is graphically described we can get on to making them.

Yee Ha!
 
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