Back Loaded Horn Speaker Build. No Happy Ending (Yet).

[FireGuruMN]

I was always doubtful about the amount of bass I would get from an 8" driver. But this project was more about the learning experience and getting some wood work going in my life again. I'm pretty sure that the interior volume is irrelevant to this sort of speaker design. It's all about bringing the sound around to the front to get every little bit of bass that you can get.

What software are you using to do the modeling?

I've just been getting into REW measurements and room design. I need to buy a better calibrated microphone. I pretty sure the one I have is ok for comparing one speaker to the next but it is not good for providing absolute readings since I do not have a calibration file for it. Seems like all the USB mics are backordered lately. Too much Covid shutting down manufacturing I would guess. I might get that parts-express speaker measurement tool at the same time. That does impedance sweeps I believe.

I was just Googling speakers made from concrete. Not that would be a mess. . .But it would certainly remove some of the form factor limits that flat sheets of wood put onto speaker design. I gotta quite letting my mind wander, it does not always come back lately.

 

[kevintomb]

I was always doubtful about the amount of bass I would get from an 8" driver. But this project was more about the learning experience and getting some wood work going in my life again. I'm pretty sure that the interior volume is irrelevant to this sort of speaker design. It's all about bringing the sound around to the front to get every little bit of bass that you can get.

What software are you using to do the modeling?

I've just been getting into REW measurements and room design. I need to buy a better calibrated microphone. I pretty sure the one I have is ok for comparing one speaker to the next but it is not good for providing absolute readings since I do not have a calibration file for it. Seems like all the USB mics are backordered lately. Too much Covid shutting down manufacturing I would guess. I might get that parts-express speaker measurement tool at the same time. That does impedance sweeps I believe.

I was just Googling speakers made from concrete. Not that would be a mess. . .But it would certainly remove some of the form factor limits that flat sheets of wood put onto speaker design. I gotta quite letting my mind wander, it does not always come back lately.

I use Box port design II for my modeling.

Interior volume is still very relevant, as combined with the Vas, Qts, and Fs measurements will determine bass. There is not way around to get free bass.
There may be cancellations due to the design that are actually reducing the bass overall. I am not familiar enough with this type of design to say, if the Qts measurement will work great or not.

The speakers you used (Tang Band) DO have a fairly large Vas measurement, and that always implies a speaker that will work better in a fairly box. But the small Qts value counteracts a large Vas number, but will limit bass.

Your box building it top notch. That is my weak point always. Maybe I lack patience.
I am more about the modeling and planning phase I think.

 

[kevintomb]

@Pete B

Hey I know you are also from the Parts express forum, if you have time, can you look this thread over and see what you think?

he is using a tang band 8" full range.

Fs 42 Hz
Qts .27
Vas 94.45 liters

I am not familiar enough with this box type, but modeled it as vented and the low Qts limits bass a good bit obviously.

 

[FireGuruMN]

I get 3.33 cu ft (94.2 liters [edited, forgot to hit paste in google conversion ).for the volume if I did the calcs right. That's the interior rectangle minus the triangle at the bottom minus all the internal structures. It does include the volume at the bottom that is really open to the room because of the huge "port" at the bottom. It does not account for padding or the fill behind the driver.

 

[kevintomb]

I get 3.33 cu ft (28.3 liters).for the volume if I did the calcs right. That's the interior rectangle minus the triangle at the bottom minus all the internal structures. It does include the volume at the bottom that is really open to the room because of the huge "port" at the bottom. It does not account for padding or the fill behind the driver.

3.33 cu ft, would be about 95 liters.

28 liters is about one cubic foot.

 

[Pete B]

[edit]
I can deal with needing an EQ curve even though the reviews of this driver and enclosure indicated it would have really good bass. Maybe it's just a personal preference in the sound I like. I have many other speakers that I am happy with that do not need an EQ like that.
Second: Once I get the low end sounding good, the vocals and high frequencies drop out every time a bass note comes through. This is very evident on Ed Sheeran Afire Love. (sorry, it's just a good test song). As soon as the bass notes are gone everything sounds wonderful again. What's going on there? Is the driver not capable of generating bass and mid-range at the same time?
I've got no problem adding a separate woofer and crossover if that is what it takes. I just need these to sound good. I'd wanted them to be a demonstration piece for how impressive an 8" driver could sound but maybe I need to get past that.

Help.

I'll post this and maybe by the time I get through the build steps I will have an answer.

This type of design has no logic behind it. You are listening to the front of the driver, fine, then
the design boosts up the mid bass through the back loaded horn. If that adds 10 dB of gain then
those frequencies covered by the horn are boosted way too much. You'd be much better off
making the box a vented design.
My guess on the bass - mid issue is that the bass is driving the woofer beyond its very short
Xmax - the bass sounds fine because we tolerate a lot of bass distortion with no issue. The
voice coil driven (mostly) out of the gap makes the midrange efficiency drop.

The design is completely flawed and I'm pleased that you are hearing it correctly and not
clouding your perception with a dream of them sounding good.

Also direct radiators require baffle step to sound balanced in most listening rooms and this
design doesn't have any. Try placing them in the corners once you figure out how to get
bass out of them.
I don't build designs like this so I don't think I can help you more.

 

[FireGuruMN]

3.33 cu ft, would be about 95 liters.

Edited.

Try placing them in the corners

The corners in that room are are filled with JBL 4435's and they don't move. I might try these in a different room though. Someday I'm going to put those tang band drivers on a blank sheet of plywood and see how they sound without any sort of enclosure at all. Not really an "open baffle" speaker, just a hunk of plywood. I can say for sure that putting them in these enclosures sound better than hearing them in open air. I had them playing while I installed them and it was cool to hear the sound explode as they hit the enclosure.

I did get these plans off the Parts Express website. So if they are a bogus design maybe that should be taken down. . .But they do sound good now. . .Just ridiculous to have 135 pound speakers without much bass.

 

[kevintomb]

Edited.


The corners in that room are are filled with JBL 4435's and they don't move. I might try these in a different room though. Someday I'm going to put those tang band drivers on a blank sheet of plywood and see how they sound without any sort of enclosure at all. Not really an "open baffle" speaker, just a hunk of plywood. I can say for sure that putting them in these enclosures sound better than hearing them in open air. I had them playing while I installed them and it was cool to hear the sound explode as they hit the enclosure.

I did get these plans off the Parts Express website. So if they are a bogus design maybe that should be taken down. . .But they do sound good now. . .Just ridiculous to have 135 pound speakers without much bass.

I am not sure it is truly a bogus design, but most of the bottom part, is really not contributing to the bass that matters. It appears to be a short bass horn, but that would limit it in what frequencies it boosts.

Sort of "Voice of the theatre" look/performance in a way.
They would do okay as bass reflex in that big a box, but would still be lacking deep bass wise I think.

 

[lcheetec]

Well, isn't this interesting:
View attachment 1874655
It's like seeing double. I attached the complete PDF also.
This came from the Fostex website and it has numerous design features very similar to to the Tang Bang design that I built.
It also has some interesting advice about damping:
View attachment 1874656

I also attached the plans I found for the Dallas II. Now that looks like a lot of thought (or processing time) went into the design:
View attachment 1874658
I gotta build that one and see how it sounds. I think I will double up on 1/2" baltic-birch plywood to get a 1" thickness. There is just something nice about working with that thickness. Of course I will have to make adjustments in the design to keep the audio pathway the same width all the way down the pipe. More AutoCAD work. I might even try putting some of that damping goo in between the sheets of 1/2" plywood. But I am TOTALLY done with MDF. I think I've been getting headaches from the off-gassing of the glue. Yuch. Even though something else will probably kill me (probably my wife) before that does, I'm done with MDF.
It's going to be no fun cutting all those angles. I might have to find a better tool. Maybe one of those power miter boxes with the rails for super long extensions. Or a radial arm saw? Or a sliding bed for my table saw? So many tools.

And I was going to spend the summer building wood cases for all my receivers. Wonder if I will ever get around to that. Might have to put a heater in the garage.

It's funny, when I read all your posts (really enjoyed the adventure, BTW), then saw this.

It was like someone out a mirror on my own journey. Let me explain.

After completing the Siegfried Linkwitz LXmini design, and being quite happy with it, I went on to designs that had more wood in them, like the Voigt TQWP design (which was so-so, probably due to the inexpensive driver I used), and then the designed-for-Fostex-FE206EN Back Loaded Horn you've just discovered.

It wasn't quite a smooth build, as I used 18mm instead of the recommended 1" (25mm) furniture ply. So I had the pieces not fitting in some places, and shifted stuff just a wee bit (3mm here, and there) so that everything lines up in the end.

Well, the result was better than I expected! They are decent down to below 40Hz (REW measured), and probably almost 30 in-room. I've got a pair LXSub4's left over from the LXmini design, so I am running them with the Fostex BLH build, for below where I cross them over (36, I think). The cello and double-bass region is sweet, and for oomph when I'm doing a movie, I've also got an SVS sub, but I mostly leave that off.

The interesting part is, I never used the Fostex 8" drivers the cabinet was designed for. On a recommendation of a friend, I used the... Tang Band W8-2145, and I believe that's where the good comes from. I also didn't want to spend as much money for the Fostex's.

During the holidays, I found the SUG1-19 design from Tang Band and that's how I came across your post.

Funny!

 

[erzhj67ijz]

im truly out of words reading or better, whitnessing this. im building speakers for more than 20y and this must be the worst ive ever seen.
telling by the ridiculous deranged actions this guy is taking, he is clearly a psychopath and should get arrested. ive never seen anything
like it. unbelievable. at first i thought, this foe should get another hobby, when i saw later with what brutal aggression this subject smashed and grizzled
holes and dents into the cabinet, i knew, hes a danger to general public. a psychopath. im from germany, and this is beyond anything.oh boy...

 

[Poultrygeist]

I enjoyed the same Tang Bands in OB's. Great looking with quality construction with a nice refined sound. But I found them a little too polite for my tastes. Sold them after buying the in-your-face Lowther DX3's. As I recall the TB's were bass shy on their own even in huge folding baffles.

 

[kevintomb]

I enjoyed the same Tang Bands in OB's. Great looking with quality construction with a nice refined sound. But I found them a little too polite for my tastes. Sold them after buying the in-your-face Lowther DX3's. As I recall the TB's were bass shy on their own even in huge folding baffles.

View attachment 2214116

I get why some like the Dipole speaker sound, but find the implementation of many of these often ignore proper design, and do nothing to compensate for the "Dipole Peak" that occurs when front and back sound waves combine and create a big bump in the response in the range of a few hundred Hertz.

So they kinda fix one thing, but create a new issue.

 

[halkaloogie]

im truly out of words reading or better, whitnessing this. im building speakers for more than 20y and this must be the worst ive ever seen.
telling by the ridiculous deranged actions this guy is taking, he is clearly a psychopath and should get arrested. ive never seen anything
like it. unbelievable. at first i thought, this foe should get another hobby, when i saw later with what brutal aggression this subject smashed and grizzled
holes and dents into the cabinet, i knew, hes a danger to general public. a psychopath. im from germany, and this is beyond anything.oh boy...

First post and coming out swinging.

 

[rothwellaudio]

im truly out of words reading or better, whitnessing this. im building speakers for more than 20y and this must be the worst ive ever seen.
telling by the ridiculous deranged actions this guy is taking, he is clearly a psychopath and should get arrested. ive never seen anything
like it. unbelievable. at first i thought, this foe should get another hobby, when i saw later with what brutal aggression this subject smashed and grizzled
holes and dents into the cabinet, i knew, hes a danger to general public. a psychopath. im from germany, and this is beyond anything.oh boy...

Don't sit on the fence - tell us what you really think.

 

[Poultrygeist]

I get why some like the Dipole speaker sound, but find the implementation of many of these often ignore proper design, and do nothing to compensate for the "Dipole Peak" that occurs when front and back sound waves combine and create a big bump in the response in the range of a few hundred Hertz.

So they kinda fix one thing, but create a new issue.

Every design is a compromise. Whether it's a TB, Fostex or Lowther these drivers require an extensive break in period. Many Fostex drivers get returned before they're properly broken in.

 

[Nixxuz]

im truly out of words reading or better, whitnessing this. im building speakers for more than 20y and this must be the worst ive ever seen.
telling by the ridiculous deranged actions this guy is taking, he is clearly a psychopath and should get arrested. ive never seen anything
like it. unbelievable. at first i thought, this foe should get another hobby, when i saw later with what brutal aggression this subject smashed and grizzled
holes and dents into the cabinet, i knew, hes a danger to general public. a psychopath. im from germany, and this is beyond anything.oh boy...

I'm not sure where you are from has anything to do with manners. The finished results looked fine to me, and apparently sound fine to the OP.

 

[Poultrygeist]

I built these MLTL speakers and was shocked at how plentiful the bass was. I think others have used the TB's in these with good results. Far easier to build than BL horns.

http://www.quarter-wave.com/Project04/Enclosure_Design.html

 

[BilboBaggins]

im truly out of words reading or better, whitnessing this. im building speakers for more than 20y and this must be the worst ive ever seen.
telling by the ridiculous deranged actions this guy is taking, he is clearly a psychopath and should get arrested. ive never seen anything
like it. unbelievable. at first i thought, this foe should get another hobby, when i saw later with what brutal aggression this subject smashed and grizzled
holes and dents into the cabinet, i knew, hes a danger to general public. a psychopath. im from germany, and this is beyond anything.oh boy...

You made me laugh with this statement!

I read it as tongue in cheek, although it appears a few don't read it the same way. I enjoyed this thread, and true, it is an exercise in hacking, but the OP made impressive steps to get things better. The thing is, when you play with something of this nature, you will rarely get good results right off the bat. There is a learning curve, and experimentation. I'm sure the OP is moving on to better things. But I also see that this is in the OPs nature. Looking forward to seeing and reading about more.

Cheers!

 

[grindstone]

Backhorns with widerange drivers aren't so much a project as an intermittent sub-hobby. Thanks to the OP who built, measured, and posted everything!