New diy open baffle project: 3-way with AMT

Jump to Latest
H

Herbie70

Member
Joined 2022
#1
Hi all,

after reading about open baffle designs and projects across the internet for several weeks I am coming closer to an idea what I would like to build myself.
Sine I have only built a few diy kits myself decades ago I hope I get some help in designing my speakers. I do not have any experience with that so far.

Inspirations came from: the pure audio project, spatial audio, GR research, blue plane acoustic, supravox and others.
My first idea was to go for 2* 15" woofer + wideband driver (e.g. Tangband...) but I have changed directions.

My idea is to go for a 3-way system using an AMT as tweeter. Soomething similar to the Spatial Europe mc series no 8: https://spatialeurope.de/portfolio-item/mc-series-no-8-en/

I dont want to play around with DSP or equalizers, I hope to get good results with just passive XO.
My first choice of drivers would be Supravox 215 (or maybe 165) for the mids, a Mundorf AMT (AMT23D6.1-R) with homemade waveguide. A reference design on the Supravox homepage suggest th 285 as woofer but I wonder if there is a good combination utilizing a 15" such as the Spatial Europe speaker.
I also looked into Acoustic Elegance drivers but hesitate because of the very high shipping costs to Switzerland where I live.

On further "requirement" is moderate baflle size, again the Spatial Europe mc no 8 would be just right, as well as the reference design on the Supravox homepage. The intention is that it should not dominate the living room, so about 45x120 cm is on the upper end of acceptable sizes.

For the beginning I hope to get some advice on finding matching speaker drivers, I have set myself a budget of max. 1500 EUR/CHF for drivers per speaker.

Open for inputs! I know that some software exists to simulate different speaker positions and baffle geometries, I plan to do some experiments with these software packages to better understand the implications different options....
 
#2
Question regarding sensitivity match:
I did some more reading (Martin King OB Design paper and other ressources) and come to the conclusion that matching the (Mundorf) AMT's
which have sensitivites of around 88-93 dB (except one very expensive model) with the highly efficient Supravox drivers might be counter-productive. Is this correct? It seems that sensitivity-wise the AE drivers seem to be a better match. I have not looked into other AMT's yet, meybe the Beyma 150 fits better with Supravox?
 
#3
Herbie70 said:
Question regarding sensitivity match:
I did some more reading (Martin King OB Design paper and other ressources) and come to the conclusion that matching the (Mundorf) AMT's
which have sensitivites of around 88-93 dB (except one very expensive model) with the highly efficient Supravox drivers might be counter-productive. Is this correct? It seems that sensitivity-wise the AE drivers seem to be a better match. I have not looked into other AMT's yet, meybe the Beyma 150 fits better with Supravox?
Click to expand...
In addition to that: The AMT's with 92/93 dB have 6 Ohms. Is it adviasable to use additional resistors to match with resistance of typicall 4 or 8 Ohms with mid/bass drivers?
 
#4
If your amp is a good design the 6 ohm tweeter won’t be an issue. Look into actual ESS AMT drivers from the ESS company itself. They are dipoles that are more efficient and can cross over lower than most AMT drivers. They are less expensive too even with shipping.
 
#5
I did a DIY 3-way open baffle speaker about 7 yeas ago. A photo of my speakers is shown at:

https://midwestaudio.club/wp-content/gallery/mwaf-2015/DS34813.jpg

The 15 inch low frequency driver is the Eminence Kappalite 3015LF neo driver, the midrange is the Faital PRO 10PR300 which has a 10 inch diameter, and the tweeter is a horn loaded AMT Hawthorne Audio Model 700 driver. Hawthorne Audio went out of business about 5 years ago so sadly this AMT is no longer available. Both of the cone drivers have neodymium magnets so they should have better dipolar performance on a flat baffle. The plastic horn on the tweeter enhances the forward radiation but it has an open back rear without horn loading for rear radiation. The bass performance of the Eminence 3015LF is improved by the open back 'enclosure' cabinet which increases the front to back distance for better performance output for bass frequencies. This cabinet supports the front baffle which is solid maple.

Finally, the dimensions of these speakers is 104 cm H, 46 cm W, and 46 cm D. While the bass 'enclosure' is a 46 cm cube, the width of the front baffle narrows from 46 cm wide and to a 23 cm width at the top of the baffle. The baffle is 2.5 cm thick.

The crossovers for this speaker is 180 Hz bass/mid and 700 Hz mid/tweeter. I use a DEQX DSP for 48 dB per octave crossover slopes. The DEQX corrects for the amplitude vs. frequency as well as time corrections. Learn more at:

https://www.deqx.com/technical/
I still have these speakers and their performance is ideal.
Jim
 
Last edited:
#7
Jim Griffin said:
I did a DIY 3-way open baffle speaker about 7 yeas ago. A photo of my speakers is shown at:

https://midwestaudio.club/wp-content/gallery/mwaf-2015/DS34813.jpg

The 15 inch low frequency driver is the Eminence Kappalite 3015LF neo driver, the midrange is the Faital PRO 10PR300 which has a 10 inch diameter, and the tweeter is a horn loaded AMT Hawthorne Audio Model 700 driver. Hawthorne Audio went out of business about 5 years ago so sadly this AMT is no longer available. Both of the cone drivers have neodymium magnets so they should have better dipolar performance on a flat baffle. The plastic horn on the tweeter enhances the forward radiation but it has an open back rear without horn loading for rear radiation. The bass performance of the Eminence 3015LF is improved by the open back 'enclosure' cabinet which increases the front to back distance for better performance output for bass frequencies. This cabinet supports the front baffle which is solid maple.

Finally, the dimensions of these speakers is 104 cm H, 46 cm W, and 46 cm D. While the bass 'enclosure' is a 46 cm cube, the width of the front baffle narrows from 46 cm wide and to a 23 cm width at the top of the baffle. The baffle is 2.5 cm thick.

The crossovers for this speaker is 180 Hz bass/mid and 700 Hz mid/tweeter. I use a DEQX DSP for 48 dB per octave crossover slopes. The DEQX corrects for the amplitude vs. frequency as well as time corrections. Learn more at:

https://www.deqx.com/technical/
I still have these speakers and their performance is ideal.
Jim
Click to expand...
Great design, thanks for sharing! Do you know the specs of the AMT you used? I cannot find them on the internet. I would like to better understand how you matched those with the mid and sub parameters.
 
#8
Herbie70 said:
In addition to that: The AMT's with 92/93 dB have 6 Ohms. Is it adviasable to use additional resistors to match with resistance of typicall 4 or 8 Ohms with mid/bass drivers?
Click to expand...
I still want to understald better the implications of mixing drivers with different impendances. Is there a ressource on the internet that explains this in depth? After all, there is no problem in mixing them maybe, when other specs match?
 
Last edited:
#9
A slot loaded U frame open baffle is compact and gives great bass efficiency. Couple that with an AMT in a wave guide and a midrange and you have something special.

https://www.diyaudio.com/community/threads/cheap-and-fast-ob-literally.249984/

I’m making one out of wood because it was so good sounding I have to revisit it. I’ll use a planar tweeter in a waveguide and a high sensitivity 5in to 6.5in midrange.
 
#10
What about this combination for AMT and mid-woofer:
Tweeter: AMT23D6.1-R (88dB, 8Omhs)
Mid: Audio Technology FLEXUNITS 6 A 77 20 06 SD Woofer (88.5dB, 8 Ohms)
Woofer: tbd 12" or 15" with about 95dB and high Qts (this could be one from AE or Supravox)
What other parameters do I need to check so that this will be a good match?

For the waveguide I would like to build something like that, just from wood:
https://www.selmoni-speakers.ch/waveguide-technologie/index.html
 
Last edited:
#15
Herbie70 said:
What about this combination for AMT and mid-woofer:
Tweeter: AMT23D6.1-R (88dB, 8Omhs)
Mid: Audio Technology FLEXUNITS 6 A 77 20 06 SD Woofer (88.5dB, 8 Ohms)
Woofer: tbd 12" or 15" with about 95dB and high Qts (this could be one from AE or Supravox)
What other parameters do I need to check so that this will be a good match?

For the waveguide I would like to build something like that, just from wood:
https://www.selmoni-speakers.ch/waveguide-technologie/index.html
Click to expand...

Another combination I like is the following as I just realized, that the AE dipole10 driver would matche the sensitivity of the AMT very well, and even the diploe12 is pretty close. So I could start with a "no-XO" approach first, only cap for tweeter?

Tweeter: AMT23D6.1-R (88dB, 8Omhs)
Mid: Acoustic Elegance Dipole10 (87dB, 8Ohms)
Woofer: tbd

Question: As I am still struggling a bit the driver specs: The AE is a double coil driver. Is the sensitivity of 87dB the one with both coild in parallel?
 
You must log in or register to reply here.
Top Bottom