EEVblog #1162 - Little British Monitors

[b_force]

At the end of the discussion, I don't really care if it is a pure a transmission line or bass reflex or a mix between the two.
That is just nitpicking about the details. You can make wonderful design with either of both approaches, or completely fail as well.

It doesn't make a speaker a million times better and it certainly doesn't make the speaker worth around 350 bucks for a self made kit with jellybean parts and a bad PCB design.

[AmmoJammo]

It doesn't make a speaker a million times better and it certainly doesn't make the speaker worth around 350 bucks for a self made kit with jellybean parts and a bad PCB design.

For something as "entry level" and consumer grade as these, I would have used an off the shelf class D amplifier, with Bluetooth module built in, and simply run a single full range driver, without the added complexity of active crossovers and bi-amping... especially seeing its using a pretty low end automotive amplifier chip...

Perhaps I should launch a Kickstarter campaign...

[bsdphk]

It is not just a matter of nomenclature or preference, there is a big difference in how it works and what follows.

For instance BR has high efficiency whereas TL are inefficient, basically: does the port help or hinder the woofer.

(That is another datapoint here: 4x50W amplifier for 2x1800cm³ internal volume is horribly inefficient.)

In the end the best way to teil is to listen: TL has a tight and controlled bass whereas BR is loose and resonant.

[b_force]

It doesn't make a speaker a million times better and it certainly doesn't make the speaker worth around 350 bucks for a self made kit with jellybean parts and a bad PCB design.

For something as "entry level" and consumer grade as these, I would have used an off the shelf class D amplifier, with Bluetooth module built in, and simply run a single full range driver, without the added complexity of active crossovers and bi-amping... especially seeing its using a pretty low end automotive amplifier chip...

Perhaps I should launch a Kickstarter campaign...

And ask $250 for it 

I would have done many things different.
Don't get me wrong, I admire this kid for being all excited about his fancy ideas (I give him the benefit of the doubt).
But the whole design looks, feels and smell just like an hobby project.
Absolutely nothing wrong at all with hobby projects, but selling that for 350 bucks feels VERY wrong to me.

I have seen kids his age doing much much better.

[AmmoJammo]

(That is another datapoint here: 4x50W amplifier for 2x1800cm³ internal volume is horribly inefficient.)

The 4x50 is an optimistic, unrealistic figure.

The part mentioned somewhere (I can't find it now) suggested 4x35watts at 1% THD, if run off 18volts. I don't know what supply voltage he's using...

I would have done many things different.
Don't get me wrong, I admire this kid for being all excited about his fancy ideas (I give him the benefit of the doubt).
But the whole design looks, feels and smell just like an hobby project.
Absolutely nothing wrong at all with hobby projects, but selling that for 350 bucks feels VERY wrong to me.

I have seen kids his age doing much much better.

It's a fantastic project!
I good step into both reading, understanding, and implementing datasheets, along with PCB design and layout, as well as speaker enclosure design and construction.

It's the exact type of project I'd suggest to people who wanted something to design and build (although using electronics kit(s) while I was working in an electronics component/kit retail store...

[bsdphk]

At the end of the discussion, I don't really care if it is a pure a transmission line or bass reflex or a mix between the two.
That is just nitpicking about the details. You can make wonderful design with either of both approaches, or completely fail as well.

It doesn't make a speaker a million times better and it certainly doesn't make the speaker worth around 350 bucks for a self made kit with jellybean parts and a bad PCB design.

100% agreement there.

While I do admire squeezing a TL design into that tiny size, and would love to listen to them, to see how well he did it, I'm not paying 400 quid for the privilege.

[b_force]

In the end the best way to teil is to listen: TL has a tight and controlled bass whereas BR is loose and resonant.

I was already afraid of this comment.

Basically it comes down that you never designed a proper BR design.
They all have their pros and cons, even closed designs, dipole and cardioid.

When designed properly and more importantly USED properly, they can all sound much better than anything else.
When there is a mismatched, the result is getting tons of myths on the internet about nude elves, snake oil and such.

[b_force]

(That is another datapoint here: 4x50W amplifier for 2x1800cm³ internal volume is horribly inefficient.)

The 4x50 is an optimistic, unrealistic figure.

The part mentioned somewhere (I can't find it now) suggested 4x35watts at 1% THD, if run off 18volts. I don't know what supply voltage he's using...

From Marco Reps video I understand that he is using a TDA7850 amplifier chip.

That thing is ancient, and definitely not something to be proud off in an "high-end" design.
For the tweeters you don't need that much power anyway.
But since he is using some kind of awkward fullrange driver that is only capable of a few watts, that number is already a lot less lower.
The Dayton ND91-4 can only do 30W in RMS and (although not stated in the datasheet) 60W in peak (crest factor 8 or 12 normally)

The whole point is, nowadays Class-D amplifiers perform better in noise and THD plus you don't need such a big and ugly (wrongly mounted) heatsink.

[bsdphk]

Basically it comes down that you never designed a proper BR design.
They all have their pros and cons, even closed designs, dipole and cardioid.

Again: 100% agreement (And for the record: I coined the concept "Audio-homeopathy" :-)

But there is a physical difference between BR and TL, and it largely amounts to TL using/wasting electrical power to improve the pulse-response in the bass domain.

And given that TL is hard to design, demands a lot from the woofer, have low efficiency, they are justifiably rare.

But good TL's, like the Rauna Njord, make it all worth while.

[b_force]

Basically it comes down that you never designed a proper BR design.
They all have their pros and cons, even closed designs, dipole and cardioid.

Again: 100% agreement (And for the record: I coined the concept "Audio-homeopathy" :-)

But there is a physical difference between BR and TL, and it largely amounts to TL using/wasting electrical power to improve the pulse-response in the bass domain.

And given that TL is hard to design, demands a lot from the woofer, have low efficiency, they are justifiably rare.

But good TL's, like the Rauna Njord, make it all worth while.

I guess yeah.
Although, if you're looking for efficiency I would rather suggest a horn.

The thing is though, nowadays (sub)woofers are made so much better than 40 years back.
But even more is amplifier power that is dirt cheap and small.
So generally I just advice a multi-subwoofer closed system for the lower-end because that also tackles all the standing waves in your room
(Floyd Toole: Sound Reproduction if you want to read more on that)

Even for the high SPL professional audio speakers it is mostly just BR for convenience.

I have designed and made some nice TL speakers in the past, but to be very honest; it's to much work, effort en problems in the end compared to a WELL designed BR speaker.
One thing that is absolutely noticeable are the standing waves and other crap in a TL design.
Like I said, nothing comes for free.

[NiHaoMike]

I have seen powered speakers where each speaker has it's own volume control, making balancing possible.

That makes it a bit cumbersome to adjust the volume in that the balance would also have to be readjusted.

[b_force]

I have seen powered speakers where each speaker has it's own volume control, making balancing possible.

That makes it a bit cumbersome to adjust the volume in that the balance would also have to be readjusted.

Most monitor speakers are designed to use with a computer, so that is just simply adjusting a setting in your audio settings.
For the 1% that uses these things for their home-audio (and even thinks about adjusting it), meh, can't be bothered.

A lef-right control with just one (passive) potentiometer adds some margin of error anyway in neutral mode.

[bsdphk]

The thing is though, nowadays (sub)woofers are made so much better than 40 years back.
But even more is amplifier power that is dirt cheap and small.
[...]
I have designed and made some nice TL speakers in the past, but to be very honest; it's to much work, effort en problems in the end compared to a WELL designed BR speaker.
One thing that is absolutely noticeable are the standing waves and other crap in a TL design.
Like I said, nothing comes for free.

Again, 100% agreement.

My only complaint were the people who dismissed this as not being a TL design or who as Dave not even knew that at a TL design "is a thing".

I think the right way to think about this speaker is a working 1:2 scale model of an Austin Mini: Possibly an impressive feat, not very useful or relevant for transportation :-)

[b_force]

My only complaint were the people who dismissed this as not being a TL design or who as Dave not even knew that at a TL design "is a thing".

Well, my complained to Dave in general is that if it's not something like scopes or something, it's just a quick peak and nothing more else.

He didn't even give any information about which IC's were being used.
For the record, TL074, or in other words; the cheapest of the cheapest.
I never use these things in any modern and new design anymore unless it needs to be cheap as chips.
They are even being sold as (quote) general purpose opamps.

All together it says a lot about the design.

[Bud]

This is a great project and we need more people like him to resurrect kitting to help kids and others to learn electronics. This one is particularly good because it is not a throwaway kit, you get a working useable device in the end. And there is a Lot of efforts required to make kits, the smartasses here in this thread just have no clue  what it takes.

[AmmoJammo]

This is a great project and we need more people like him to resurrect kitting to help kids and others to learn electronics. This one is particularly good because it is not a throwaway kit, you get a working useable device in the end. And there is a Lot of efforts required to make kits, the smartasses here in this thread just have no clue  what it takes.

What the industry needs to get more interest from kids (and adults) in hobby and DIY electronics, and assembly, is affordable kits.

This is not the project for that...

[Fungus]

a bass-reflex design of the same outher dimensions, would at least pretend that the double- and electric bass were invented.

Even if it pretends they're single-stringed instruments that can only play one note.

[floobydust]

Who else is offering a kit similar to this? It looks like a fun project and a bit high in price for my tastes especially crossing over the Atlantic. Perhaps the loudspeakers and electronics could be split out as two kits.

Of course you can improve the design to absolute perfection.
I've had poor results with shelf-type vents (air) doing two 90 degree bends. Also with the vent's foam filling, it might act like a Variovent. I don't know if it has active EQ seeing the steep 50Hz rolloff.

[b_force]

Who else is offering a kit similar to this? It looks like a fun project and a bit high in price for my tastes especially crossing over the Atlantic. Perhaps the loudspeakers and electronics could be split out as two kits.

Of course you can improve the design to absolute perfection.
I've had poor results with shelf-type vents (air) doing two 90 degree bends. Also with the vent's foam filling, it might act like a Variovent. I don't know if it has active EQ seeing the steep 50Hz rolloff.

I used to make kits and plans all the time on forums, but eventually it's just always a lot of work.

Nowadays it's easier just to come up with something yourself

[akimmet]

I can't see why they would not be classified as transmission-line speakers?

TL speakers are a rarity, which is probably why Dave seems to wonder if it is even "a thing", and it is certainly both unusual and probably hard to get right in such a small enclosure.

Their rarity is due to not many woofers having what it takes (see below) and because there is (still!) no way to create a good TL design, except trial and error.

The best-selling TL speaker design ever was probably Bo Hanssons "Rauna Njord", which were made from concrete and therefore weigh 35kg each. (https://vintagehifiproducts.wordpress.com/2014/06/19/rauna-of-sweden-the-story-continues/)

TL designs often have high cross-over frequency.  The physical requirements of a bass unit to drive a transmission line are almost the same as for full-tone units in horn-enclosures, and if you have a full-tone unit as bass anyway, you can get the cross-over out of the midrange by pushing it up, instead of down.  The Rauna Njord's cross-over is 3.5 kHz and the tweeter is mounted coaxially on the lower of the two bass units.

TL designs and some horns can be used with current-drive, where the amplifier delivers a current rather than a voltage proportional to the signal.  At least in theory this is better, because the magnetic field in the speakers coil depends on the current, not the voltage.  In practice it takes a lot of experimentation.  See also Nelson Pass' F1 and his writings about it.

Yes, TL speakers are more difficult to model and design. That is why most end up avoiding this route, and go directly to bass-reflex or sealed designs.
Folded horn, and tapped horn are some other uncommonly used bass enclosure designs.

I had no idea Bo Hansson had his name put on speaker designs. I do enjoy his albums, El-Ahrariah is one of my favorites.

[edy]

Great video! I have always been interested in various speakers. The second last ones I found curb-side were Kenwoods and it was only after several years that I realized one had a blown tweeter. Of course, I couldn't tell because both main speakers were ok and the one tweeter that did work seemed to cover for both.

Then I lucked out and found a pair of JM Labs Chorus 715 which apparently are now Focal. The pair of towers also came with a center unit called the Chorus CC 700. In the image below, it is what you see on the left side of the picture (not the speakers on the right side of the photo stacked on each other, which appears to be a large woofer SW700 and surround SR700):



I always wondered how these fare in the speaker world, and how Focal is compared to JM Lab as far as quality, materials go. These things are supposed to be made in France. Perhaps Focal switched over manufacturing to China? I also still can't figure out why someone dumped these on the curb (no obvious performance issues, although the color is awful in that orange-wood).

I see a pair of 715's advertised here for $300:

https://marche.quebecaudio.com/occasions/index.php/annonces/jmlab-chorus-715/

And the center speaker was sold for not much either:

http://kahlaudio.com/products/focal-jmlab-chorus-cc700-center-speaker-current-model-lots-of-positive-reviews-650-msrp/

Probably lower-end in terms of "audiophile" quality, but better speakers than I have ever actually owned? Maybe the previous owner chucked them because these are considered not good enough for their audiophile system? I don't even know what you would consider a "good" pair of speakers cost range to be. Sadly I am plugging only the pair of 715's in to my garbage tuner which only has 2-channel left/right stereo out, there is no surround output and therefore I can't even use the CC 700! Perhaps someone will curb-dump a 5.1 channel surround tuner amp. 

[In Vacuo Veritas]

For that price you can buy commercial "PC monitors" that are quite good, surprisingly so.

[mc172]

I can't believe how expensive these are. I got a very good pair of KEF 104/2s for about £350 recently!

[AmmoJammo]

..so... its not a transmission line...

makes the whole thing a bit more questionable...

[Bud]

I can't believe how expensive these are. I got a very good pair of KEF 104/2s for about £350 recently!

Were your KEFs also made in a garage/home by a single person?