Hi, Everything I've built has used a CD to reach down to small mids between 700-1000Hz, ...or using the CD to reach all the way to large mid-lows between 500-700Hz.
I can't begin to picture/ imagine how a mid could span up to 4000Hz... What are you using above the mids, mounted at the horn's apex?
None so blind as those that cannot see.
I have an answer already. I created the models, equalized the 19 cm model a little and adjusted drive for near Xmax at the low end. I then used the same EQ settings and drive level on the 35 cm model; 36 cm because the schematic view suggested I couldn't go any further, likely wrong about that. In HR, you can run a model, right click in the graph window and capture current results, then run a 2nd model and compare (tools menu).
I did that and saw that the only change in output was that the reflection null moved to a lower frequency; no changing loading or extension at the low end.
I have an answer already. I created the models, equalized the 19 cm model a little and adjusted drive for near Xmax at the low end. I then used the same EQ settings and drive level on the 35 cm model; 36 cm because the schematic view suggested I couldn't go any further, likely wrong about that. In HR, you can run a model, right click in the graph window and capture current results, then run a 2nd model and compare (tools menu).
I did that and saw that the only change in output was that the reflection null moved to a lower frequency; no changing loading or extension at the low end.
I should offer some disclaimers. Its been a few years since I was seriously modelling synergy horns, so I may have screwed something up.
I paid no attention to Vrc, the rear chamber volume. You probably can't get 34L inside the horn cab. This doesn't limit your extension but does increase the amount of power you will need to get it.
I did give a momentary thought to Vtc, the air trapped between the woofer cone and the horn wall so I think those params are reasonable. If I look at the raw output, rather than the EQed and LPFed, I see reason to see if trapping more are would give more acoustic low pass filtering
Lp, the thickness of the horn wall didn't seem to be critical, 1-2 cm seemed to work fine. I probably wouldn't be saying this if we were modelling mids that needed to reach above 1 khz.
I paid no attention to Vrc, the rear chamber volume. You probably can't get 34L inside the horn cab. This doesn't limit your extension but does increase the amount of power you will need to get it.
I did give a momentary thought to Vtc, the air trapped between the woofer cone and the horn wall so I think those params are reasonable. If I look at the raw output, rather than the EQed and LPFed, I see reason to see if trapping more are would give more acoustic low pass filtering
Lp, the thickness of the horn wall didn't seem to be critical, 1-2 cm seemed to work fine. I probably wouldn't be saying this if we were modelling mids that needed to reach above 1 khz.
I tried increasing Vtc from 900 to 1800 but, if anything, that increased the response level beyond the notch.
What seems to have the most and beneficial effect is reducing the effective port length well below 1 cm but that might not be practical, given the large hole area. You could try "frustrum"ing the port holes
And one more caveat: the port area isn't sufficient for 130 db output level. Seems to be good for about 118 db or so. At that level, you have a lot of excursion remaining to extend the low end.
What seems to have the most and beneficial effect is reducing the effective port length well below 1 cm but that might not be practical, given the large hole area. You could try "frustrum"ing the port holes
And one more caveat: the port area isn't sufficient for 130 db output level. Seems to be good for about 118 db or so. At that level, you have a lot of excursion remaining to extend the low end.
I'm working on something similar to a DSL J7/8. Multiple stacked short horns feeding into a large horn. Mids and highs are both in the short horn. Faital Pro HF108R for the highs (1") and Beyma 6MCF200Nd on mids (6.5") with Beyma 10MC700Nd for lows (10") on the large horn. Each mid taps into two short horns basically so the mouth so it's close enough for 1/4 wavelength of 4000Hz.
Cool, thx. I'm going to study how you input the ports, and give a HR a spin again. Been a long time since I used it to model a meh, too.
Rear chamber on the 12"s is pretty small, being in the top and bottom cavities wedged between horn walls, and with top and bottom "lids" nearly touching motors.
Actual volume is in my notes somewhere ???......
I steeply high-pass the 12"s no lower than 100Hz.
Using same driver in syn10's, I found 110-120Hz worked well. Maybe that was due to ports being limited at higher SPL?
12mm horn walls / port lengths is the limit, can't go any less.
I've quit fooling with trapped volume between cone and horn wall on anything, small mids including. Simply not work all the work ime.
Now that I can't get any Baltic Birch to work with, simulations are looking more enticing....
Hi Mark, I'm a novice when it comes to DIY audio - I didn't study physics or any related subjects at any level - so apologies if I'm not catching something obvious or if my use of terminology is off.
I have been reading through many MEH threads over the years and was wondering as it doesn't seem to be touched on too much when making MEH speakers, why isn't there a large and low tuned (LLT) cabinet below the already large horn to extend frequency response to make it full range? As I understand it the MEH is front loading the drivers to some frequency, which is determined by the horn mouth size which can be impractical to do the full frequency range by just front loading them so why not rear load them with a LLT to make up for the shortfall?
I think in this thread you touched on some difficulty with the shape of the cabinet directly behind your bass drivers resulting in standing waves when you discussed porting for the rear loaded response, is this the main difficulty with this configuration or is it something else?
I have been reading through many MEH threads over the years and was wondering as it doesn't seem to be touched on too much when making MEH speakers, why isn't there a large and low tuned (LLT) cabinet below the already large horn to extend frequency response to make it full range? As I understand it the MEH is front loading the drivers to some frequency, which is determined by the horn mouth size which can be impractical to do the full frequency range by just front loading them so why not rear load them with a LLT to make up for the shortfall?
I think in this thread you touched on some difficulty with the shape of the cabinet directly behind your bass drivers resulting in standing waves when you discussed porting for the rear loaded response, is this the main difficulty with this configuration or is it something else?
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@RobertChicken most synergy/unity/MEH boxes are full range "enough" meaning that they reach low enough to be used as a main speaker in a PA that has its own subs. Adding anything exterior to the horn means that the directivity is lost. Any bass bin wouldn't be part of the synergy happening. So even if it's built as one giant box, it's no longer acting like a synergy horn. It'll only ever be a horn + the additional LLT.
The big thing with an MEH is that everything is perfectly in phase because it's all horn-loaded together with each set of drivers being within 1/4 to 1/3 wavelength of each other. Adding anything that isn't in the MEH directly will cause a phase shift at some distance and it won't be an MEH.
The big thing with an MEH is that everything is perfectly in phase because it's all horn-loaded together with each set of drivers being within 1/4 to 1/3 wavelength of each other. Adding anything that isn't in the MEH directly will cause a phase shift at some distance and it won't be an MEH.
I think I get it, any loading of the drivers and porting of the MEH and its enclosure needs to occur within the MEH in order to prevent phase issues.
Thanks for clearing that up.
Hi RobertC, I'm not picturing exactly what you mean.
Do you mean a second large horn box below the MEH? Or incorporating large low tuned drivers into the MEH?
And not sure what you mean by the MEH is front loading the drivers...?
My take on a MEH is that the horn loading gains of drivers placed in/on the horn, are more of a secondary advantage, than the primary advantage of closing down inter driver spacings. And I think the horn is about a constant directivity design.
Most MEH's for home audio hope to be smallish in size and weight....which necessarily precludes large heavy boxes.
I think designing them, knowing a sub is mandatory makes practical sense.
With syn11, where I've tried to put a sub into the MEH by adding a pair of 18"s onto the horn, it's become pretty clear to me subs are subs...no beating Hoffman's iron law. The 18"s need box volume and ports just like any other reflex sub....which makes the dang entire MEH crazy big to do right.
So if you meant a second large horn box below the MEH, I say go for it!
If you meant incorporating large low tuned drivers into the MEH, I'd say study the Danley boxes, their drivers and ports .....but know you will still need a sub.
Hope that was understandable...
Yes, loading isn't the goal of the waveguide. The size holds the same radiation angle over a range. (Maybe that's what @RobertChicken meant, but the situation will be different to the back horn kind of loading.)
If you let the lower bass spill around the waveguide, it's not so different than a rear horn or a separate similarly sized box underneath.
If you let the lower bass spill around the waveguide, it's not so different than a rear horn or a separate similarly sized box underneath.
So as I see it there is the MEH itself, and an enclosure around it but typically these don't extend below the MEH, so my thinking as to provide volume for the subs in your Syn11 would be to make the enclosure for the horn bigger like my attached pic (it's a side view). And as I understand it from what others have explained above if that does work, the enclosure would only be ported through the MEH to prevent phase issues. Wouldn't this provide the enclosure volume you need?
Yes, that is both a practical and cost consideration, but given the already large footprint of your Syn11 and something like @ncbluetj B.A.S.H, why not extend the cabinet below the MEH and pop some castor wheels on it?
I may be mixing up terms in that case, I thought if a drivers front is faced into a horn it is: front loaded, but I guess in the case of an MEH that isn't the goal as @AllenB has stated even if it is visually similar.
I think I understand that separate and well placed/integrated subs help provide a cohesive listening experience for a given room but if you already have multiple midbass drivers or subs as part of your MEH why not make full use of them?
I know some people hold the view of a stereo system not including a sub being "right" or "pure" and I wouldn't necessarily agree with that but for me in a smaller room with say a MEH that used 2 12" midbass drivers (along with the CD and mids) I could see adding more volume to it as a reasonable tradeoff for gaining bass and not needing to add a sub in a limited space.
Yes, much appreciated
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It is front loaded per se. It's just that the discussion of loading isn't relevant to the mouth size in the way you were referring. That's a matter of directivity.
By the way, it's the same for an MEH as a regular horn/waveguide.
I was just going through the PDF of the Synergy Calc V5, and noticed that, I'm sure I also read a thread on that build at some point but I suspect I wasn't making sense of it at the time.
Yeah, I need to do more reading on the topic, I kind of understand these concepts at face value but once it comes down to the technical understanding of it I do get lost but I guess there are plenty of resources to help as I go along.