• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

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

My very first gut reaction is that you need more damping material inside the cabinet, and at key transition points. You will have to insert, close the box, measure, open the box, modify, rinse and repeat. You have a lot of transitions. Each one will change the characteristics of the system.

My second reaction is, I don't think that felt liner is doing much. It's too thin to be useful. Need a thicker felt. or bituminous foam on those long runs.

Need more time to let this sink in, but those are my initial reactions.
 
Ok. Lunch break. Geeking out a little more I remembered something a realtor told me once, location, location, location.
Previously the speakers were out in front of my 4435's. That is where a lot of test speakers end up because 4435's don't move.
I had the new speakers angled in with the faces pretty pointing directly at my listening position. From recent experiences with Magnepans I tried flattening out the angle and making them square with the room. That really really helped the highend harshness. It really brought the high end to an enjoyable level.
Now to fix the low end I moved my subwoofers out of the way (no I don't need subs with 4435's, they are just for LFE when watching movies).
I slid the new speakers into that position right next to the 4435's and as close to the wall as possible. There are a bunch of cables back there so it was still about 2" out.
Here are the new sweep results:
upload_2020-5-19_12-32-53.png
Green line=jbl
Red=tang bang
Observations:
  • 4435's have more low end. Really more low end that any speaker deserves IMHO. At least in my house. Its fun having everything rattle at around 40hz when I do a sweep.
  • But look at the improvement in the low end on the Tangs with them against the wall. Woohoo. This is without any DSP or such in place. Just straight from REW.
  • But even more interesting is the mid to high. Every peak and trough matches up between the two speakers. That's either my room or my test equipment (or amplifiers? no, not amps) making those roller coaster rails.
  • So back to playing music, I was able to lower the EQ low end boost such that I only raise the low end by 3 db for it to sound good to me. Previously it was 8db and that was causing issues with reflections or something. That problem is gone now. Or at least diminished enough that I cannot notice it.
  • So I might have to reevaluate my test equipment and then start thinking about room treatments if making these graphs look pretty is important to me. Maybe it's not important. If it sounds good then it is good. Gotta remember that always.

rothwellaudio said:
I think I'd be devastated
Click to expand...
Heck, I spend an entire summer and countless dollars building a treehouse that I spend most of my time alone in now. Wifey is not into it. Maybe that was the plan all along? Hammock and noise cancelling headphones and I'm in heaven.
upload_2020-5-19_12-48-55.png
Like I said, nuts is nuts. Gotta go all in.

I'm happy enough with the sound of these speakers at this point that I will go ahead and finish the grills and put on the veneer once the pieces show up.

More to follow.
 
baco99 said:
I don't think that felt liner is doing much.
Click to expand...
Agreed. It was a concern from the start but I don't think there is much I can do about it now. I can get to some areas through the bass port but not enough to matter. An access hold in the back would allow me to put different materials in the first bend. That might be the most important section. I will consider that before applying veneer. Imagine how much I will curse when I cut the speaker wire. And I know I will cut the wire. . .

Next question where do I find the proper material?
 
It would be interesting to see what the frequency response of the TangBand would be mounted in a flat baffle - the bigger the better. If you have a scrap piece of plywood, mount it somewhat assymetrically near the center, prop it up and measure away. You may be surprised at the bass, especilly if you have the long side on the ground, but the experiment I'm suggesting is to see if those peaks and troughs are inherent in the driver's response - you hope not, but it would be good to know for sure. You may decide its worth doing two for stereo.
 
Comparatively, all of these make the Ethyl Merman's look smooth as butter. Thanks for posting! :bigok:

The JBL "veil" (i.e., depressions in the lower midrange and upper-most midrange) is readily apparent and what I have been dealing with/battling for years, The Mermans are so much smoother through this area (as well as over the rest of the band) though the 4435s go a bit lower. Still, I don't get such a big dip below 70 Hz from the 2241s in the Mermans giving them a better sense of "punch."

BTW, I assume that each plot is for just one speaker being played and not the pair. If this is for a pair measured in the room, one would expect to see far more peaks and dips than for a single.

index.php
 
Last edited:
Nat said:
...the experiment I'm suggesting is to see if those peaks and troughs are inherent in the driver's response - you hope not, but it would be good to know for sure.
Click to expand...
I'm pretty sure those peaks and troughs are transmission line reflections.
 
rothwellaudio said:
I'm pretty sure those peaks and troughs are transmission line reflections.
Click to expand...

Yep, it's behaving like an undamped transmission line.
Standing waves.
And in that respect there is a fine line here in terms of definition.
Perhaps these cabinets qualify as what Martin King would call an "expanding transmission line"?
 
My plan on the tree house (of course) but she had her girl friends over and they convinced her it was the coolest thing ever (after a bottle of wine).

But guys:
The JBL 4435's (green line) showed the same bumps above 700hz so I was going with some sort of room or measurement problem. Maybe I'll take them to the tree house and do some open air measurements for the neighbors. . .
 
I would stuff the first 1/3 of the line with low density polyurethane foam about 66% starting right behind the driver..
The next 1/3 of the line around 40-50% stuffed.
The last 1/3 of the line around 20% stuffed.
Place the foam in the line not up against the side walls.
 
JimPA said:
I would stuff the first 1/3 of the line with low density polyurethane foam about 66% starting right behind the driver..
The next 1/3 of the line around 40-50% stuffed.
The last 1/3 of the line around 20% stuffed.
Place the foam in the line not up against the side walls.
Click to expand...
I agree, some stuffing is required, but the cabinets are all glued-up and there's no access to the insides. Personally, I think I'd try stuffing the mouth of the horn - just because it's accessible - to turn the cabinets into a kind of aperiodic vent design.
 
rothwellaudio said:
I agree, some stuffing is required, but the cabinets are all glued-up and there's no access to the insides. Personally, I think I'd try stuffing the mouth of the horn - just because it's accessible - to turn the cabinets into a kind of aperiodic vent design.
Click to expand...


I was thinking similarly, just add a baffle to the throat and make it behave more like a ported enclosure. Or even just seal it up.
 
There is a significant amount of poly-fill in the cavity right behind the driver. I can pretty easily add more in the very top section of the snake and the last couple of bends that are accessible through the bottom port. I could also cut a hole in the board at the top of the bottom port and stuff those cavities. That would only leave a couple of sections untreated.
This must be how my surgeon felt when he replace my shoulder through a 2" incision. I still can't figure out how they do that. I'm sure there are youtube videos but I'm probably better off not knowing.:yikes:

Will poly-fill have the same effect as low density polyurethane? :dunno: It's easier to work with and I have some on hand.

Out of the box thinking:
Blow in cellulose insulation like they do in walls and ceilings of houses! But not as densely of course. I really have to stop letting my mind wander...it doesn't always come back lately.:D

But honestly they do sound really good with the proper placement now. With the single driver the sound stage is awesome.:thumbsup: I can place every instrument in Van Morrison "Moondance" and my son even noticed the sound stage (I have no idea what song he was playing, Wrong century for me). But I did notice some drop outs of high frequencies playing Johnny Cash "Hurt" towards the end of the song where the strong bass comes in.

I did try stuffing a blanket into the port but it was not under scientifically controlled conditions. My son was curious how much bass was coming out down there.

Regardless, Thanks for the tangible solution.

I have a couple of words I have to Google now. . .
 
Over lunch I stuffed some poly fill in one of the speakers and an A/B comparison with the other. All the low end was gone from the one where I added the poly fill. That's the end of poly fill in the line for me.

So if less poly fill equals more bass I figured I could remove the fill from behind the driver. I left it in the area below the driver. Ding-Ding: More bass. They even sound ok with no EQ at all now. The sound BETTER with EQ so I left it in but that is a personal preference. The reflections are probably still there but the are not noticeable. I think some of the harshness in the upper mid range is gone also. Wish there was a way to predict all this without experimentation.

Being a geek I pulled the drivers out while music was playing. There is an incredible difference between the driver in open air and in the enclosure. Obviously. But it was [almost] thrilling to hear the difference when it is just a single driver and all the frequencies explode as soon as it hits the enclosure.

These are rapidly becoming my favorite speakers-of-the-week. I go through a lot of speakers. The speakers I like stay in rotation longer. These might not ever leave. Except that they block the projector screen. Darn. Maybe the living room. . .

Anyone got a design for a notch filter at 1,400 hz? Like -2db or so?

Once again thanks all.

More to follow once magnets and veneer arrive. I think I will order a new USB mic also. One with a calibration file for REW.
 
rothwellaudio said:
I agree, some stuffing is required, but the cabinets are all glued-up and there's no access to the insides. Personally, I think I'd try stuffing the mouth of the horn - just because it's accessible - to turn the cabinets into a kind of aperiodic vent design.
Click to expand...

In a transmission line the area behind the driver is the most critical when it comes to a damping material.

With a small enclosure the OP could get the foam inside the enclosure especially behind the driver.

FireGuruMN said:
Over lunch I stuffed some poly fill in one of the speakers and an A/B comparison with the other. All the low end was gone from the one where I added the poly fill. That's the end of poly fill in the line for me.

So if less poly fill equals more bass I figured I could remove the fill from behind the driver. I left it in the area below the driver. Ding-Ding: More bass. They even sound ok with no EQ at all now. The sound BETTER with EQ so I left it in but that is a personal preference. The reflections are probably still there but the are not noticeable. I think some of the harshness in the upper mid range is gone also. Wish there was a way to predict all this without experimentation.

Being a geek I pulled the drivers out while music was playing. There is an incredible difference between the driver in open air and in the enclosure. Obviously. But it was [almost] thrilling to hear the difference when it is just a single driver and all the frequencies explode as soon as it hits the enclosure.

These are rapidly becoming my favorite speakers-of-the-week. I go through a lot of speakers. The speakers I like stay in rotation longer. These might not ever leave. Except that they block the projector screen. Darn. Maybe the living room. . .

Anyone got a design for a notch filter at 1,400 hz? Like -2db or so?

Once again thanks all.


More to follow once magnets and veneer arrive. I think I will order a new USB mic also. One with a calibration file for REW.
Click to expand...

Foam is superior to poly fill in transmission lines.
index.php
index.php
index.php
 
That's the issue JimPA ... this is supposed to be a back-loaded horn. Without a linear taper the pressure wave is stalling in the first section (my guess). The straight sections don't promote a good impedance match to the atmosphere at the mouth. The pressure wave should gradually expand to work effectively. I've see this design before from other driver companies with reported issues. The "Dallas II" is an improved design, which by coincidence, did away with the straight runs in favor of a linear taper. These should only need the fabric damping on the tunnel panels with some poly in the cavity behind/below the driver.
 
Well, isn't this interesting:
upload_2020-5-22_7-40-56.png
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:
upload_2020-5-22_7-43-57.png

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:
upload_2020-5-22_7-46-5.png
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.
 

Attachments

Make a sled for the table saw FireGuruMN. You'll use it on a lot of projects. Basic design has a strip fit to the miter gauge slot and a 1/2" bb panel attached to the strip. Easy and accurate.
 
You must log in or register to reply here.
Back
Top Bottom