Bookshelf-Sized CBT array - Constant Directivity through 5,000hz

[RobS]

Interesting speakers, but you are deliberately misleading with your phase response graph.

Your Hook speakers show 30° per division whereas the KEF LS50 is 1° per division. You fudged the scale to make your speakers appear flatter than they are.

 

[somebodyelse]

TEBM46C20N BMR beams relatively high on the upper octave (some real 3rd party measurements of the Tectonic look by far not so nice at the ones of the spec sheet).

Would that be the HiFiCompass tests or did you have another one in mind?

 

[HookAudio]

To everyone that has commented on the scaling of measurements, these will be redone and posted shortly.

Does the 'BMT' in Dayton's driver title mean 'Bending Mode Transducer'?

That's my understanding. The idea for both families of products is to create a reinforced "cone" that remains planar and pistonic throughout its operating range.(edit note: I was wrong here as to the "why" of Dayton's BMT and Tectonic's BMR drivers. They're just both driver families that work well off-axis.)

Interesting design, look forward to measurements. I always felt the best use of the CBT was in home theater or PA where you want wide even coverage, but it's cool to see mature designs doing other things.

One of the special things about the size of the H1 is that they're small enough to make CBT accessible as a center channel. In living with my prototypes and production units, I've actually been shocked how many well-mixed cartoons there thanks to my 3 and 5yo girls. (The Grufalo, Stickman, Snowy Day, and Pete the Cat on Amazon are solid examples).

Maybe I am wrong to imagine the 12 stacked drivers as behaving like one that's now roughly 15" tall and still 5" wide?

You're correct, but the combined driver that they're approximating is slice of a spherical point source rather than a planar driver. One of the reasons for choosing this driver was that I could maximize the surface area of the combined emitter.

Would the beaming be reduced by the 12-driver tall stack?

Yes, because with a CBT, you're always located off-axis and hearing the summed response of multiple drivers. Don Keele demonstrates this in one of his papers by showing measurements of a CBT effectively passing a square wave at a bunch of positions around a room in left, right, front, back of the speaker.

 

[somebodyelse]

That's my understanding. The idea for both families of products is to create a reinforced "cone" that remains planar and pistonic throughout its operating range.

That's certainly not what Tectonic (claim to) do - they're trying to exploit and control the breakup of the disc to get directivity that couldn't be achieved if it remained pistonic at the upper end of the frequency range.
https://www.tectonicaudiolabs.com/w...9/05/Tectonic_BMRWhitePaper_Rev2.0_2019-1.pdf

 

[HookAudio]

That's certainly not what Tectonic (claim to) do - they're trying to exploit and control the breakup of the disc to get directivity that couldn't be achieved if it remained pistonic at the upper end of the frequency range.
https://www.tectonicaudiolabs.com/w...9/05/Tectonic_BMRWhitePaper_Rev2.0_2019-1.pdf

Reading that application note, you're right. I misunderstood the why of what Tectonic is doing here. It's not the driver I ended up implementing, but I should have read deeper before commenting on BMR.

 

[thewas]

Would that be the HiFiCompass tests or did you have another one in mind?

The current issue of German DIY loudspeaker magazine Klang & Ton has measured them too, but due to copyrights I don't want to upload it here.

 

[hex168]

Assuming I'm right about the vertical orientation of the Dayton driver in their off-axis response graph, here's a suggestion for an alternative approach that would have good horizontal dispersion. Unfortunately, it would not look as cool:
Lower drivers: Tectonics TEB46, upper drivers TEBM35. "Upper" and "lower" meaning physical location in the array, no crossover. Purpose of the two different drivers is to implement 6 dB of the required shading via driver sensitivity instead of resistors. Response and dispersion should be similar enough.

 

[HookAudio]

Assuming I'm right about the vertical orientation of the Dayton driver in their off-axis response graph, here's a suggestion for an alternative approach that would have good horizontal dispersion. Unfortunately, it would not look as cool:
Lower drivers: Tectonics TEB46, upper drivers TEBM35. "Upper" and "lower" meaning physical location in the array, no crossover. Purpose of the two different drivers is to implement 6 dB of the required shading via driver sensitivity instead of resistors. Response and dispersion should be similar enough.

I have the Tectonic drivers from when I was trying to pick what to use. There are several problems with them that made the HARB252 a better choice for the H1, but the biggest one is distortion below 400hz for both sizes you mention. Low distortion is one area where the Dayton driver shines.

When I have a chance to pick my head up from the H1 launch, my intention is to use the 3" BMRs in an LX-mini style build with a pair of Peerless 835025 aluminum woofers that I've had for a while.

 

[hex168]

I have the Tectonic drivers from when I was trying to pick what to use. There are several problems with them that made the HARB252 a better choice for the H1, but the biggest one is distortion below 400hz for both sizes you mention. Low distortion is one area where the Dayton driver shines.

When I have a chance to pick my head up from the H1 launch, my intention is to use the 3" BMRs in an LX-mini style build with a pair of Peerless 835025 aluminum woofers that I've had for a while.

Thanks! You are right about the distortion below 400Hz. Glad to hear the Dayton driver does better there.

 

[Richard Berg]

Can these be hung from the ceiling?

As new owner of a large loft-style apartment, I was thinking of installing something like this to get wide, even dispersion across the space, but maybe a clever little planar array is what the doctor ordered.

PS according to GMaps I'm a 9-minute drive from Henry St

 

[HookAudio]

Can these be hung from the ceiling?

As new owner of a large loft-style apartment, I was thinking of installing something like this to get wide, even dispersion across the space, but maybe a clever little planar array is what the doctor ordered.

PS according to GMaps I'm a 9-minute drive from Henry St

Congrats on the new loft!

H1's would be just about perfect dispersion, particularly if we can put them right against the ceiling. Don and I are also working on a complementary OB sub for the H1s.

Where in NYC is are? I'll send a PM.

 

[tifune]

Don and I are also working on a complementary OB sub for the H1s.

Would there be something significantly different about a sub to complement H1's vs. a typical sub?

Have you considered bass extensions like JBL CBT 70J-E ? I suppose that would make placement much less flexible but connectivity much more convenient.

Have you verified any wall mounts yet? Your own or 3rd party

Your Hook speakers show 30° per division whereas the KEF LS50 is 1° per division. You fudged the scale to make your speakers appear flatter than they are.

Would be interested to hear a response to this; I'm not qualified to verify/deny it but an apples:apples comparison would go a long way for us hobbyists.

 

[HookAudio]

Would there be something significantly different about a sub to complement H1's vs. a typical sub?

It's open baffle with integrated DSP and can play from 20hz through 200hz.

Have you considered bass extensions like JBL CBT 70J-E ? I suppose that would make placement much less flexible but connectivity much more convenient.

I hadn't for exactly the reason you list.

Have you verified any wall mounts yet? Your own or 3rd party

Let me get a few 3rd party wall mounts in to test before I recommend one. You're not the first to ask, so going forward, there will be several 1/4-20 (tripod socket thread) holes in the underside of the metal foot of the H1.

Would be interested to hear a response to this; I'm not qualified to verify/deny it but an apples:apples comparison would go a long way for us hobbyists.

Yes, the scaling is flawed and the error is entirely mine. We're re-doing all of the measurements on the site with a proper controlled environment and will be reposting when complete.

 

[Richard Berg]

Yes, the scaling is flawed and the error is entirely mine. We're re-doing all of the measurements on the site with a proper controlled environment and will be reposting when complete.

Update?

 

[HookAudio]

Update?

Hey Richard, updated H1 design and detailed measurements will be posted later this week along with a revamped website. Happy to get together for our planned listening session at some point next week as well.

 

[magic44ken]

In the future, do you plan to add a side woofer to fill the lower bass below 150Hz for those who don't have the space for a sub or don't use a sub for a desktop speaker? Also in a surround setup, movies have lots of content below 150Hz for surround and center speakers. So adding sub to main speaker doesn't solve this issue.

I read that one of con with CBT speaker is that the high frequency drops 10dB which result in a less sparkle high. Does your CBT speaker address this issue?

Thanks

 

[HooStat]

In the future, do you plan to add a side woofer to fill the lower bass below 150Hz for those who don't have the space for a sub or don't use a sub for a desktop speaker? Also in a surround setup, movies have lots of content below 150Hz for surround and center speakers. So adding sub to main speaker doesn't solve this issue.

One can use most subwoofers for content below 150-200 Hz. If you purchase one or two relatively inexpensive ones and place them near the front speakers, there shouldn't be any noticeable localization effects including for the center channel. I suspect that if you run a third sub in the back of the room, you wouldn't be able to notice anything from the surround speakers. But I am not a person who cares much for surround speakers or strives for perfection with with them, so I could be wrong.

 

[HooStat]

Also, if this is true, you can get good response to 100 Hz and that is probably close enough to minimize any localization issues.
From the website:

there is ample headroom for EQ the H1 flat to 100hz without creating issues with distortion

 

[magic44ken]

One can use most subwoofers for content below 150-200 Hz. If you purchase one or two relatively inexpensive ones and place them near the front speakers, there shouldn't be any noticeable localization effects including for the center channel. I suspect that if you run a third sub in the back of the room, you wouldn't be able to notice anything from the surround speakers. But I am not a person who cares much for surround speakers or strives for perfection with with them, so I could be wrong.

That ks for the detail solutions. I have though about it. Unfortunately, my living room doesn't have the space for multiple subs.

You do hear a big different in the surround speakers if it roll off early below 200Hz.

Another consider that I just read is the high frequency drops 10dB compare to the rest of the frequency response that resulted in less sparkle.

We will have to wait for a review.

 

[jtwrace]

@jtwrace
The LS50 measurements were used with his prior permission.

Awesome! Sorry for my comment then.