HELP - 4X10 Rear Loaded Horn

Hi Folks,

Giving up on the idea of a 4 driver TL for bass guitar use, I have set about designing a rear loaded horn. It is not a subwoofer, but I thought this would be the best subforum to post this.

Design goals are as loud and low as I can get without exceeding ~350l (constructed box volume) in a full range enclosure.
Screenshot 2023-05-29 181837.png


I have a problem modelling the rear chamber (red section in the above photo)

With VTC set at he right value and ATC set at zero, I get a response I like

Screenshot 2023-05-29 182158.png


Screenshot 2023-05-29 182303.png


My problem arises when using any value other than zero for ATC. It doesn't matter whether I set the figure at 0.01 or 99999, I get the same response, which looks quite a bit different. I would have thought tweaking ATC should change the response.

Screenshot 2023-05-29 182516.png


Screenshot 2023-05-29 182612.png







Perhaps the correct way to model this is as an OD, but can someone explain why the value of ATC changes nothing once it's over zero? The same happens with VRC and LRC.

Also, I'm very open to suggestions for design improvement. This application is not hifi, so a smooth response is not required. I'm trying to keep the constructed box volume below 350l, and the drivers are intended to be run full range. I don't need excellent performance in the 30hz range, but some loading down there is very desirable.


My hornresp file is attached
 

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There might be some posts on effect of throat chamber volume/shape. MJK at his quarter-wave site has detailed discussion papers including guidance on and reasons for coupling chamber sizing in a BLH. Hornresp loudspeaker wizard allows simulations that almost in real time, displays the spl impact at the horn mouth/driver/combined of the chamber volume. Listening will be the real judge. If you set the “path” distance in the loudspeaker wizard the response will look smoother.
 
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GM

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Joined 2003
In the example below, which is the correct measurement of Ltc the green or blue dimension?
Neither in that you have to adjust all the bends, termination per this bend computation (71.4 cm, attached)......BTW, at a glance your HR sim needs to be ~ completely redone, hence the inability to add a low pass filter, so first switch to offset driver (OD), then switch the 214 cm spec with the 27.80 cm to get the drivers to the end of the pipe and then you'll likely find that you'll have to redo the horn construction to add one of any (if any) worthwhile use due to its high CR IIRC. :(

edit: driver for my records? '10DNA' returned nothing audio related
 
@GM The 27.8 section at S2 relates to the second last bend in the horn (circled below), not the segment that the drivers are in.

Screenshot 2023-05-31 085621.png



Are you suggesting that I should model this without a throat chamber, and instead modelling as an offset driver horn?

If I do this, do I need to model Vtc at all?

Screenshot 2023-05-31 095221.png



This adds ~50cm to the horn length, and presumably, I model the location of the drivers at the midpoint of the two sets (~25cm from the start).

Doing to gives me this, which is much less pretty than modelling with a throat chamber and a shorter horn. Still useable, but the dip at 100hz is not great for bass guitar.



Screenshot 2023-05-31 094610.png




Screenshot 2023-05-31 094432.png


The drivers are from a commercial bass guitar cabinet (DNA) and have been measured with DATS v3,


As from compression ratio it currently sits a whisker under 2:1 - I was of the view that this as not at all high.

I have attached the Hornresp file for the OD model. Feedback is very welcome. I would especially like to know how I would tweak the design to get a response per the throat chamber model, rather than the OD model.
 

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Still useable, but the dip at 100hz is not great for bass guitar.

Feedback is very welcome.
The dips at 200, 300, 420, 550 and above are also not great for bass guitar.
The big peaks around 160 Hz and 200Hz often are where room resonance occurs, I've found excess in that range sounds "muddy" on stage or in low ceiling venues.

A bass reflex of similar size would have about 4dB more output at 30Hz, sounding over twice as loud down at the low B, and smooth rising response above, close to the same average sensitivity other than the octave from 160 to 320Hz.
DNA Bass reflex.png


At 40 volts (around 200 watts into "8 ohms") the BR would keep up to a loud drum set, and have way more low end than an Ampeg 8x10".
DNA 40 volts.png

It would do better regarding your design goal of "as loud and low without exceeding ~350l (constructed box volume)" than the back loaded horn, and its weight would be about a sheet of plywood less ;)

Art
 
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Thanks @weltersys !

I had considered a large bass reflex, but had written the idea off due to poor power handling. While you are quite right that 200w into a large bass reflex 4x10 will keep up with a loud drummer, I already have several cabs that will do that :). I was really wanting to do something different and more efficient than a regular bass reflex.

I hadn't considered the peaks and troughs above 200hz, as I had assumed that the folds in the horn would filter much of these highest frequency resonances out. I know JBL quoted that their 4530 and 4520 speakers essentially became direct radiators above 150hz. Has this not been your experience?

One more comment on your bass reflex proposal is that it is very much limited to 200w, and comparing maximum spl curves between it and a BLH, it's only around 35hz where the BR becomes louder. I don't need louder, and probably won't use louder in a live setting, but half the fun is "having louder" if I want it.
 
in ~210 liters external bulk you could make a Karlson style box - it should have good "hit"if not dig loud down low. Here's a rough sim of a K15 sized Acoustic Control 115BK with 4-Delta 10A in 2pi /40v. You could adjust K15's dimensions to accommodate the 4x10 baffle.

Which 10s do you have or intend for the project? - OH I see - - up at the start of the thread
 

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The dips at 200, 300, 420, 550 and above are also not great for bass guitar.
The big peaks around 160 Hz and 200Hz often are where room resonance occurs, I've found excess in that range sounds "muddy" on stage or in low ceiling venues.

A bass reflex of similar size would have about 4dB more output at 30Hz, sounding over twice as loud down at the low B, and smooth rising response above, close to the same average sensitivity other than the octave from 160 to 320Hz.
View attachment 1179371

At 40 volts (around 200 watts into "8 ohms") the BR would keep up to a loud drum set, and have way more low end than an Ampeg 8x10".
View attachment 1179372
It would do better regarding your design goal of "as loud and low without exceeding ~350l (constructed box volume)" than the back loaded horn, and its weight would be about a sheet of plywood less ;)

Art


Thank you again for your advice, Art.


I've made some revisions to the back loaded horn, essentially making it a series of stepped sections to aid in construction simplicity.

Screenshot 2023-06-01 190115.png


Screenshot 2023-06-01 185331.png
Screenshot 2023-06-01 185527.png







And here's a maximum SPL comparison between a large bass reflex and this current iteration. While sensitivity gain might not be significant, power handling/max spl seems to be.

1.jpg


This box (whichever way I go, and that might be a simple bass reflex yet) with be powered using a module bought from Aliexpress that has 31 fully parametric eq bands, so nasty peaks can be dealt with, troughs not so much.

I'd like to go with a rear loaded horn if I can get it to work. There's a cool factor that comes with it, but my concern remains the nulls at ~250hz and up. I would be interested to know whether these appear in practice.

There is, of course a reasonable likelihood that I haven't modelled everything quite correctly yet
 
it’s roughly the volume of an Ampeg 8x10, which is an extremely common bass cab.
They're not all that common at all. In 40y of playing bass and running my own PAs, I've only seen a few in use, and unless you're young, strong and fit, loading one in and out will be a major PITA. And back. Horrible dull sounding things.

I'm not seeing the point at all in the TL loaded 4x10. If you must have a TL, use a 15 or 18 and cross to something higher. None of the combing with a 4x10 either.
 
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@Brett we must move in different circles as an SVT with a fridge has been the provided backline for me for a number of gigs over the last 25 years. Very common on large/outdoor stages, too.

Your memory of loading them might be a little scratchy, as I think they’re a fair bit easier than a 4x10 or other smaller cabs. Tilt back wheels let’s you drag them around very easily and when it comes to loading, the skids on the back of them means you can lay them over, pick up the bottom and slide them in. The height is a real advantage here. They aren’t great with long staircases, though.

As for why a 4x10 back loaded horn, I have the drivers and as an exercise in audio engineering, I want to see how I can get the most out of them, without exceeding the physical volume of an 8x10, which I consider the ubiquitous big stage bass cab.