Thanks guys. Jim, I'm looking at other drivers and noting their good parameters - I'll send you my spreadsheet. Those larger than the SB that have polymer frames, I can trim on my table saw using a jig - done that before. I don't mind the SB cost - I just want performance that won't require big EQ - like Minidsp. Maybe I'm dreaming...
Hank, If you can afford the SBs, I would certainly go that way and cut to the chase. But I will review your spreadsheet for any gem we haven't seen. xrk971 had some positive comments on the SB65s and others have praised them. My main complaint about the SB65s are the plastic frame requires care but most small drivers like these suffer similar concerns.
I Jim, I'll PM you from home later - been busy with dress rehearsal, concert and new rehearsal last night. Actually, I've built lots of speakers with polymer frame drivers and really like them. If done right (right glass fiber fill, etc) the frames are very strong and don't ring like the cheaper small stamped steel frame drivers.
Jim:
Great work, as always. From the one photo, it looks like you did not flush mount. So you just cut round holes and mounted? The square frame of those little drivers makes it a lot easier to place them in an array vs a pin cushion frame. Any EQ yet. Also, what kind of x-over are you doing to the woofer and at what frequency?
Great work, as always. From the one photo, it looks like you did not flush mount. So you just cut round holes and mounted? The square frame of those little drivers makes it a lot easier to place them in an array vs a pin cushion frame. Any EQ yet. Also, what kind of x-over are you doing to the woofer and at what frequency?
The drivers are not flush mounted in my array. The trade I considered was whether the flush mounting (into 0.5 inch thick material with a 1/8th inch driver flange) was worthwhile considering the closeness to the side edges of the box.
The need for 0.5" thick material is such that a 36 degrees arc is possible without kerf cuts or more complex construction. Essentially the baffle can be laid out and cut on straight material and then mated with curved cut side panels which are glued with the aid of holding clamps.
I am finishing dedicated 12 inch active sub boxes in the next few weeks. I will be using DSP plate amplifiers with an anticipated crossover to the towers at 125 Hz. My current configuration uses my old passive 10" subs from an earlier project crossed over with a receiver sub out feed to separate amplifiers. No EQ yet but I will reconsider once I hear the final configuration.
The need for 0.5" thick material is such that a 36 degrees arc is possible without kerf cuts or more complex construction. Essentially the baffle can be laid out and cut on straight material and then mated with curved cut side panels which are glued with the aid of holding clamps.
I am finishing dedicated 12 inch active sub boxes in the next few weeks. I will be using DSP plate amplifiers with an anticipated crossover to the towers at 125 Hz. My current configuration uses my old passive 10" subs from an earlier project crossed over with a receiver sub out feed to separate amplifiers. No EQ yet but I will reconsider once I hear the final configuration.
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Is Visaton FR7 good for this project?
The Fs is kindof high..
Visaton FR 7-4 2-1/2" Full-Range Driver 4 Ohm
Thanks!
The Fs is kindof high..
Visaton FR 7-4 2-1/2" Full-Range Driver 4 Ohm
Thanks!
Answers to recent questions:
Regarding curved front and rear baffles:
The front and rear baffles of my array are curved pieces of 0.5 inch thick MDF. This thickness permits the MDF to be curved over the 36 degrees arc of the CBT. Thus kerfing the material or other extreme handling techniques are not needed. The baffle hole cutting and such are done before it is curved in place. The side panels are cut with dimensions for the 36 degrees arc. Then the baffle and rear panels are glued and clamped/held by the side panels to effect the curved cabinet structure.
Regarding the weighting network:
I will submit a weighting network diagram in a future post.
Regarding the Visaton FR7:
This driver has several shortcomings vs. the SB Acoustics SB65 driver. You noted that the Fs is high which would raise the crossover from sub woofers or woofers. The frequency response is rough--sags in upper mid-range and lower treble regions--while the treble rolls off over the upper octave. These frequency issues necessitate EQ'ing. Also the Visaton driver has lower Xmax than the SB65.
The Visaton driver could be used if you intend to create a lower cost array with less performance than the SB65 array.
Regarding curved front and rear baffles:
The front and rear baffles of my array are curved pieces of 0.5 inch thick MDF. This thickness permits the MDF to be curved over the 36 degrees arc of the CBT. Thus kerfing the material or other extreme handling techniques are not needed. The baffle hole cutting and such are done before it is curved in place. The side panels are cut with dimensions for the 36 degrees arc. Then the baffle and rear panels are glued and clamped/held by the side panels to effect the curved cabinet structure.
Regarding the weighting network:
I will submit a weighting network diagram in a future post.
Regarding the Visaton FR7:
This driver has several shortcomings vs. the SB Acoustics SB65 driver. You noted that the Fs is high which would raise the crossover from sub woofers or woofers. The frequency response is rough--sags in upper mid-range and lower treble regions--while the treble rolls off over the upper octave. These frequency issues necessitate EQ'ing. Also the Visaton driver has lower Xmax than the SB65.
The Visaton driver could be used if you intend to create a lower cost array with less performance than the SB65 array.
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It's enraging. It's probably the best full range driver under $50, but I'm reluctant to buy another one because I've destroyed half of mine. Some of my frames cracked, and I found out the hard way that if you solder the connections the heat melts the frame instantly.
Peerless sells a really nice aluminum full range driver, and I have sixteen of those, and every last one has fallen apart. Most of them died because the surround dried up and cracked.
It's gotten to the point where I've just switched back to paper cone midranges because most of the aluminum ones seem to commit Hari Kari.
For some reason, the AuraSound titanium drivers don't exhibit any of these issues. I have fifteen year old AuraSound Whispers that look nearly as good as the ones I've bought this year.
I've probably evaluated about twenty different midranges for various Unity Horn projects. Here are some favs:
- The SB Acoustics 2.5" is just about unbeatable at the price. As noted in another post, I stopped buying them because they keep breaking.
- If cost is no object, AudioFrog sells a midrange similar to the SB but the AF is much more sturdy. It's an aluminum frame iirc.
- The AuraSound whisper is a killer driver, but it's ridiculously large voice coil rolls off the highs. (2" voice coil on a 2" driver!)
- Peerless sells a bunch of 2" drivers. Many are very similar. For instance, they have two models that look virtually identical, but one has lower inductance and more extended highs. So read the spec sheet carefully. Tectonic Elements TEBM35C10-4 Miniature BMR(R) Driver | Medley's Musings
This driver needs to get more love. It has nearly as much displacement as the AuraSound, but more extended highs because the voice coil is smaller. Best of all, the neo motor allows for some insanely compact CTC spacing. And it's really cheap.
If I were going to build a CBT I'd probably go for the Peerless 2" with the rising response (It's a paper cone model and I'm too lazy to look up the part number) or I'd use the Tectonics. The AuraSound is nice but it's difficult to pack them tightly in a curve array because they're so bulky. And the AuraSound treble isn't as good as the Tectonics.
Yes, the SB Acoustics SB65 can be a pesky little critter if you don't treat them right while making all of those connections.
While you can solder the various connections between connecting wires and driver terminals, I chose to use crimp connections for the drivers (Parts Express # 095-286 and 095-287) to the wiring harnesses. I assembled the wiring harnesses before feeding it though the enclosures. The polarized crimps also help maintain the polarity of each connection between the wiring harness and the drivers.
These crimp connections must be used with care as too much pressure can easily smash one of the SB65 drivers. I used my needle nose pliers to hold the speaker's terminal landing area while carefully inserting the female crimps over the spade connections. On some of the female crimps, I enlarged their opening a bit to enable smoother connection. I did crush two drivers before I got the hang of it so 48 out of 50 units were successful.
Bottom line is to use care and you will be successful. Any of the drivers you mention are tiny units so much care is needed in the assembly process.
While you can solder the various connections between connecting wires and driver terminals, I chose to use crimp connections for the drivers (Parts Express # 095-286 and 095-287) to the wiring harnesses. I assembled the wiring harnesses before feeding it though the enclosures. The polarized crimps also help maintain the polarity of each connection between the wiring harness and the drivers.
These crimp connections must be used with care as too much pressure can easily smash one of the SB65 drivers. I used my needle nose pliers to hold the speaker's terminal landing area while carefully inserting the female crimps over the spade connections. On some of the female crimps, I enlarged their opening a bit to enable smoother connection. I did crush two drivers before I got the hang of it so 48 out of 50 units were successful.
Bottom line is to use care and you will be successful. Any of the drivers you mention are tiny units so much care is needed in the assembly process.
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This Tectonic 65mm square frame driver looks interesting:
http://www.tectonicelements.com/wp-content/uploads/2014/04/TEL-DS-TEBM36S12-4A.pdf
FR drops off at the very top end, but good X mech max and low end.
http://www.tectonicelements.com/wp-content/uploads/2014/04/TEL-DS-TEBM36S12-4A.pdf
FR drops off at the very top end, but good X mech max and low end.
Hank,
On the Tectonic 65mm unit the best part is that it fits the size so that the 2.625 inches c-t-c distance is OK. Beyond that the frequency response is a mess above about 3.5 kHz. The 7-8 dB dip at 4.7 kHz is hard to deal with and would be hard to mitigate. Finally the more than 10 dB dip between 15-20 kHz will hurt. The balanced mode drivers have inherent dips in their response so I figure that the 4.7 kHz dip is the result of that effect while the larger dip near 20 kHz is just its roll-off as frequency increases.
I don't know what the Tectonic driver cost but given the relative cost of their 75 mm driver, it likely would be $10 or slightly under.
In my mind the SB65 is still the driver to use for this application. The beauty of the SB65 is that its frequency is relative flat across the band with a rising high end which counteracts the normal frequency roll off when drivers are arrayed.
On the Tectonic 65mm unit the best part is that it fits the size so that the 2.625 inches c-t-c distance is OK. Beyond that the frequency response is a mess above about 3.5 kHz. The 7-8 dB dip at 4.7 kHz is hard to deal with and would be hard to mitigate. Finally the more than 10 dB dip between 15-20 kHz will hurt. The balanced mode drivers have inherent dips in their response so I figure that the 4.7 kHz dip is the result of that effect while the larger dip near 20 kHz is just its roll-off as frequency increases.
I don't know what the Tectonic driver cost but given the relative cost of their 75 mm driver, it likely would be $10 or slightly under.
In my mind the SB65 is still the driver to use for this application. The beauty of the SB65 is that its frequency is relative flat across the band with a rising high end which counteracts the normal frequency roll off when drivers are arrayed.
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I don't disagree with your assessment; I'd go a step further and say the SB65 is arguably superior to what's in the PE CBT Epique.
But the lil' BMR is an interesting candidate. It's a feb dB hotter in the top octave.
It is ridiculously small. The diameter is about the same as a 2" driver, but the depth and the shape of the motor make it friendly to mounting in a curved array.
But SB65 is almost unbeatable in it's class.
Thanks Patrick for the input.
Yes, the Parts Express ND64-16 (PE #295-519) is the driver you get with the Epique CBT24. It has a rough frequency response in the upper two octaves and its sensitivity is 80.2 dB @2.83 V/1m. The SB65 beats it in most everything you can imagine which is why I chose it for my Modified CBT24 project.
I Googled the photo you posted and it came up with the Tectonic Elements TEBM35C10-4 which is Parts Express #297-216. It has a very smooth response albeit with a gentle falling slope across the band. Its polar plots are to die for. I could fuss over a few more specs such as its 10 watts power handling or its 80 dB @1W, 1m sensitivity. But it would be the perfect 2 inch class driver for a MiniMe CBT or other small speaker. I did notice that several P-E buyers expressed issues that made them swap for different drivers but having the right driver for their application is sometimes critical.
I'm sticking with the SB65 for my Modified CBT24 plus I like how it sounds in my listening room.
Yes, the Parts Express ND64-16 (PE #295-519) is the driver you get with the Epique CBT24. It has a rough frequency response in the upper two octaves and its sensitivity is 80.2 dB @2.83 V/1m. The SB65 beats it in most everything you can imagine which is why I chose it for my Modified CBT24 project.
I Googled the photo you posted and it came up with the Tectonic Elements TEBM35C10-4 which is Parts Express #297-216. It has a very smooth response albeit with a gentle falling slope across the band. Its polar plots are to die for. I could fuss over a few more specs such as its 10 watts power handling or its 80 dB @1W, 1m sensitivity. But it would be the perfect 2 inch class driver for a MiniMe CBT or other small speaker. I did notice that several P-E buyers expressed issues that made them swap for different drivers but having the right driver for their application is sometimes critical.
I'm sticking with the SB65 for my Modified CBT24 plus I like how it sounds in my listening room.
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I bought 4 of those little tectonic round 2" drivers.
Indeed, they are light and tiny! I'm having difficulties sourcing screws that are small enough to fit the holes!
I initially tried one in a tiny OB. Didn't work too well. Then, I put one in a sealed bottom, with the mini OB on top, and again, not too great. Maybe it's their wide dispersion pattern that interferes with OB.
Finally, I used all four in a mini sealed array and finally, they sounded great!
Sweet sound, nicely balanced. They are not loud, but offer a nice presentation.
As others mentioned, distortion comes up quickly lower than 300Hz, but it might be able to go lower when used in a full on array of 25 (or 36!) which would reduce distortion, and help with the sound pressure they might reach.
The only sad part is they cost $14 each over here.
Indeed, they are light and tiny! I'm having difficulties sourcing screws that are small enough to fit the holes!
I initially tried one in a tiny OB. Didn't work too well. Then, I put one in a sealed bottom, with the mini OB on top, and again, not too great. Maybe it's their wide dispersion pattern that interferes with OB.
Finally, I used all four in a mini sealed array and finally, they sounded great!
Sweet sound, nicely balanced. They are not loud, but offer a nice presentation.
As others mentioned, distortion comes up quickly lower than 300Hz, but it might be able to go lower when used in a full on array of 25 (or 36!) which would reduce distortion, and help with the sound pressure they might reach.
The only sad part is they cost $14 each over here.
Modified CBT24 Arrays Win 2018 MWAF Open Unlimited Class
Good news to report about the Modified CBT24 development. I entered my prototype arrays in the open unlimited class in the 2018 Midwest Audiofest (MWAF) in Dayton, Ohio and they captured first place in the class among 8 entries. You can read about the MWAF speaker design competition at:
Midwest Audiofest
Of note the three judges are well known in the loudspeaker industry--Jerry McNutt of Eminence, Peter Noerbaek of PBN Audio, and Vance Dickason. On the arrays the judges commented on their huge and engaging sound, nice vocals, and good detail. Two judges commented about the ‘nice execution' of a CBTs. For my efforts I won $250 Parts Express gift in P-E credit and a first place medal.
For the competition I essentially brought along my CBT24 system from home. A couple of months ago I changed to a different subwoofer. I am currently using a Eminence Lab12 driver inside a 2 cubic feet sealed box. The Dayton Audio SPA250 subwoofer plate amplifier with bass boost powers the woofer.
As at home a Marantz NR1602 receiver amplifies the tower arrays and crosses over to the sub. Thus the receiver and subwoofer are used in a 2.1 way configuration. The subwoofer signal from the receiver provides the plate amplifier input. The receiver settings establish the crossover frequency at 120 Hz. In my home listening room the Audyssey MultEQ auto calibration capability of the receiver is activated to equalize the system. Eight measurements are made in the room to complete the equalization.
I'll have more to report in the future about MWAF and other changes I plan for the subwoofer portion of the Modified CBT24.
Good news to report about the Modified CBT24 development. I entered my prototype arrays in the open unlimited class in the 2018 Midwest Audiofest (MWAF) in Dayton, Ohio and they captured first place in the class among 8 entries. You can read about the MWAF speaker design competition at:
Midwest Audiofest
Of note the three judges are well known in the loudspeaker industry--Jerry McNutt of Eminence, Peter Noerbaek of PBN Audio, and Vance Dickason. On the arrays the judges commented on their huge and engaging sound, nice vocals, and good detail. Two judges commented about the ‘nice execution' of a CBTs. For my efforts I won $250 Parts Express gift in P-E credit and a first place medal.
For the competition I essentially brought along my CBT24 system from home. A couple of months ago I changed to a different subwoofer. I am currently using a Eminence Lab12 driver inside a 2 cubic feet sealed box. The Dayton Audio SPA250 subwoofer plate amplifier with bass boost powers the woofer.
As at home a Marantz NR1602 receiver amplifies the tower arrays and crosses over to the sub. Thus the receiver and subwoofer are used in a 2.1 way configuration. The subwoofer signal from the receiver provides the plate amplifier input. The receiver settings establish the crossover frequency at 120 Hz. In my home listening room the Audyssey MultEQ auto calibration capability of the receiver is activated to equalize the system. Eight measurements are made in the room to complete the equalization.
I'll have more to report in the future about MWAF and other changes I plan for the subwoofer portion of the Modified CBT24.
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