• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

Selection of "best" drivers for a series of speaker projects

Andrej

Member
Joined
Mar 21, 2021
Messages
94
Likes
129
I used to have a heavily treated listening space, where the directivity of the speaker did not matter much. I now have a very reverberant listening space, so in order to improve the sound I turned to horns/waveguides. Given the cost (to me) and overall performance for the expenditure I used Dayton AMT-Pro https://hificompass.com/en/catalog/speakers/tweeters/dayton-audio-amtpro-4-tweeter-4-ohm with a waveguide (spherical horn, good down to 600Hz or so), and since it performs very well down to below its resonant frequency (about 840Hz), and already having a pair of Seas Excel 8" magnesium drivers, I used those https://hificompass.com/en/speakers/measurements/seas/seas-w22ex001 . First I built a large, conventional, matrix enclosure for them. The sound was fine, but unacceptable in my listening space. I then built a pair (again spherical) horns, with the throat at 5x5 in (actually 13x13 cm), and the mouth at 41x24in. Due to the space limitation, the 41 dimension is oriented vertically. For now I am using the small Hypex plate amp FA123 (125+125+100W), which is more than adequate with sensitivities well over 90dB/W.
For now I am using a small-ish subwoofer, with each coil driven by either L or R channel, under 150Hz. The sound transformation was drastic, as a lot of reverberation effectively disappeared. I am extremely happy with the results:)
However, the horn size is not practical. The next phase (building the center channel speaker, would have a smaller waveguide for the AMT - down to 820Hz - but fully wrapped around to the plane of the radiating element, see the photo of the test build using 3/4" MDF), and the 8" driver could be replaced by a 6-7" driver with the throat at 4x4in and the mouth at about 24x18in (down to 250Hz or so), and if I do a bit of wrap-arround for the long (now to be the wide) dimension, up to 30". If I like it, I might build the L & R speakers to match it. I might also build 5 additional surround speakers (when I finally move and have a new, better, listening space/dedicated media room), where I would use the AMT down to 800Hz, crossing over to a pro style 15" driver capable of going up to 800Hz. I am thinking of a 15" driver to hopefully maintain a narrower dispersion pattern.

The drivers I chose have some of the best distortion figures in the intended frequency range (150-1kHz, 1kHz-15kHz), and the operating bandwidth to make it all work. I am looking for the best possible distortion at up to 110dB/1m, good directivity, and managable cost. The plan is to use hypex plate amps for simplicity and more than adequate performance.

Here is where I need help, as this is the hardest part as a DIY-er - speaker driver selection. Searching the internet, other than specs, has not been fruitful, as so much effort is devoted to either tweeters/small mid-bass units, or huge sub drivers (data-bass, which is where I discovered the BMS 18N862, where Ultimax18 has been terrific, but I have this emotional preference for lighter moving mass unless I need to go below 25Hz, which I would leave to true subs).

1. I would like to use 18" drivers for the current, large horns up to 150-170Hz, 48db/octave LP filtering and DSP equalization. My current favorite is BMS18N862. Is there an better driver you know of for this application (I could go up to 21", but I plan to use those for subwoofers, and if these large horns end up in the living room, I would like to keep the box size somewhat manageable at 6-7ft3). Is there a significantly less expensive driver with almost the same performance as the best available?

2. For the smaller version, (with a mid-horn) I'd like to use 15" drivers, with additional constraints - much smaller boxes, preferably to go down to at least 40Hz (vented boxes), good up to 300Hz. Current favorite is also a BMS, the 15n840v2, but it is also over 10 years old design. I hear that there might be more recent v3 version. Also quite expensive.

3. For the surround speakers, a 15" (but could be smaller if preferable) good up to 800Hz (and I meen good up to the minimum of 1200Hz, and I'd use it up to 800Hz)

4. I m looking for alternatives to the 8" Seas Excel. My current favorite is the Purify midrange https://hificompass.com/en/speakers/measurements/purifi/purifi-ptt65m08-nfa-01a but it is pricey. I am also considering a very low distortion SB Acoustics ceramic driver https://www.erinsaudiocorner.com/driveunits/sbacoustics_sb17cac35-4/ at a quarter of the price.

5. Do you know of any non-compression driver capable of going as low as the Dayton AMT at comparable performance at high-ish volumes?

My preference for the 15" and 18" drivers is for the Pro style (higher efficiency) drivers, but that can be changed, as I'll be using Hypex plate amps allowing for sensitivity matching

I am including some photos to provide context and size perspective. AMT + Excel horns, AMT horns + conventional box, insides of the conventional box and the sub, frequency response of the large horns with the small sub at 106dB/1m, with distortion. No idea where the dip at 1.9kHz is coming from:-( I have not attempted to equalize it). The AMT in a waveguide has a mostly flat frequency response from about 650Hz to 12 kHz, nothing like the raw driver with the lowest sensitivity at resonance rising to the peak at about 11kHz.

Thanks for listening!
 

Attachments

  • 20221226_173416.jpg
    20221226_173416.jpg
    139.8 KB · Views: 207
  • 20221230_211000.jpg
    20221230_211000.jpg
    99.8 KB · Views: 228
  • IMG-20220217-WA0000.jpeg
    IMG-20220217-WA0000.jpeg
    149.6 KB · Views: 234
  • 20211218_134353.jpg
    20211218_134353.jpg
    1.3 MB · Views: 240
  • UlimaxBox.png
    UlimaxBox.png
    50.2 KB · Views: 226
  • FinalHorns.1m.R.dist.prcnt.jpg
    FinalHorns.1m.R.dist.prcnt.jpg
    340 KB · Views: 208
  • FinalHorns.1m.R.jpg
    FinalHorns.1m.R.jpg
    379.5 KB · Views: 229
OP
A

Andrej

Member
Joined
Mar 21, 2021
Messages
94
Likes
129
The new, solid and wrapped around AMT horn (one half) image did not load, so here it is. It needed more cuts to make it smoother and then final sanding, but this was just testing my program for calculating cutting angles and distances from the table saw fence:)
 

Attachments

  • 20230417_113200.jpg
    20230417_113200.jpg
    1.2 MB · Views: 125
OP
A

Andrej

Member
Joined
Mar 21, 2021
Messages
94
Likes
129
Here is the final bit of information on the large horns directivity, showing frequency response at 0, 30 and 60deg, showing a smooth drop in amplitude down to 400Hz.
 

Attachments

  • 0-30-60deg.5ft.dist.R.third.oct.smth.jpg
    0-30-60deg.5ft.dist.R.third.oct.smth.jpg
    316.7 KB · Views: 107
Top Bottom