Hello everyone.
Sorry for my english.
To fully use a good class D +900w amp i own with the DSP and averything already set, i'd like to build a new compact subwoofer with 2 4ohm drivers. I tried to find some 15" 2ohm or 4+4 or 1+1ohm drivers but i haven't found any with the good characteristics yet (at a good price at least).
The best i have made with decently priced drivers is with 2 fountek fw322-4. I've tried a simulation with many different types of enclosures and the DBR (double bass reflex) enclosure showed interesting results (serie-tuned 6th order bandpass boxes were showing good results too but i couldn't fit the 2 drivers correctly without making some very weird abstract architecture designs).
The problem is that the results in hornresp seem weird as the first port was giving better results when larger and shorter - so it could become just like part of the inner walls of the enclosure (and then become like a simple bass reflex).
I have found a way to have a good result with a smaller port but i still have some doubts if my enclosure plans would be corresponding to the hornresp simulation as changing the first port size a little makes the result seem incoherent.
Would the first port really act like a port or just like the continuity of the first chamber ?
(The two drivers are on each side and the second port is on the front of the speaker, maybe it'll cause some issues but i'd like to know if this enclosure would work like a double bass reflex first)
Depth is probably not Lc in hornresp but the depth from the front to the back of the speaker.
Here is the hornresp record:
I already thank you for reading.
Sorry for my english.
To fully use a good class D +900w amp i own with the DSP and averything already set, i'd like to build a new compact subwoofer with 2 4ohm drivers. I tried to find some 15" 2ohm or 4+4 or 1+1ohm drivers but i haven't found any with the good characteristics yet (at a good price at least).
The best i have made with decently priced drivers is with 2 fountek fw322-4. I've tried a simulation with many different types of enclosures and the DBR (double bass reflex) enclosure showed interesting results (serie-tuned 6th order bandpass boxes were showing good results too but i couldn't fit the 2 drivers correctly without making some very weird abstract architecture designs).
The problem is that the results in hornresp seem weird as the first port was giving better results when larger and shorter - so it could become just like part of the inner walls of the enclosure (and then become like a simple bass reflex).
I have found a way to have a good result with a smaller port but i still have some doubts if my enclosure plans would be corresponding to the hornresp simulation as changing the first port size a little makes the result seem incoherent.
Would the first port really act like a port or just like the continuity of the first chamber ?
(The two drivers are on each side and the second port is on the front of the speaker, maybe it'll cause some issues but i'd like to know if this enclosure would work like a double bass reflex first)
Depth is probably not Lc in hornresp but the depth from the front to the back of the speaker.
Here is the hornresp record:
I already thank you for reading.
First (interior) port probably only acts as helmholtz resonator at quite high frequency.
Nested helmholtz resonators are complex because nothing can be seen as isolated. I suppose you will have to build a test enclosure after simulating with hornresp to get exact results.
Edit: i would go with a classic bass reflex or even a closed box, if you just use it as hifi subwoofer. Or a tapped horn... what will you use it for?
Nested helmholtz resonators are complex because nothing can be seen as isolated. I suppose you will have to build a test enclosure after simulating with hornresp to get exact results.
Edit: i would go with a classic bass reflex or even a closed box, if you just use it as hifi subwoofer. Or a tapped horn... what will you use it for?
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I'm thinking this too but then how is it possible for it to have such a big influence on the low frequencies in the simulation when i change its length and area (not by much) ?
Thanks. The influence is big when we change a significant amount though but not enough to act like resonator for low frequencies.
What is impressive is the difference between a BR and a DBR (BR has a slightly larger internal volume):
The driver power graph also shows almost 100w more with the DBR at tuning frequency than with the BR (same voltage).
But now i'm thinking about a potential hornresp issue as the driver movement is at 0 on the displacement graph at tuning frequency with the DBR enclosure (instead of 2-3mm with other designs).
What is impressive is the difference between a BR and a DBR (BR has a slightly larger internal volume):
The driver power graph also shows almost 100w more with the DBR at tuning frequency than with the BR (same voltage).
But now i'm thinking about a potential hornresp issue as the driver movement is at 0 on the displacement graph at tuning frequency with the DBR enclosure (instead of 2-3mm with other designs).
At a glance, DBR should have same net Vb as BR and all three ports are the same, so seems like a good place to at least start 😉: https://www.diyaudio.com/community/threads/dcr-double-chamber-reflex.362387/
Not sure i understand. Isn't DBR the 2 ports design ? The 3 ports design is an aperiodic bi-chamber right ?
And the necessity of having the same port tunes is also the same for the DBR design ? (that would mean that the DBR design as simulated in hornresp just wouldn't work...)
And the necessity of having the same port tunes is also the same for the DBR design ? (that would mean that the DBR design as simulated in hornresp just wouldn't work...)
As the drawing shows, there's two versions of DBRs and have only used HR's two vent Wizard and otherwise way behind in researching/using all the new ones. Re aperiodic DBR, hadn't thought about it, but both DBR alignments meet the definition, so probably should amend the listings to reflect it. 👍 😎
Far as vented cabinets in general
Small cabinets around 1 cubic feet to 1.5 cubic feet
or 28 to 40 liters
Tuning is more likely to jump quickly with small port length
changes.
Looking at the drawing, woofer chambers are
24 and 37 liters so in a model and real life tuning will
be more sensitive to port length.
And with shared wall ports and correction factor
that needs to be accounted for. Probably recommend
round ports for the build.
Far as Double Bass Reflex.
Far as I can tell the overall response wont be
much different than a bass reflex.
One benefit is the upper woofer chamber can be
slightly smaller than a normal reflex. Which
slightly improves power handling.
The tradeoff for slightly more power handling.
Is the second chamber is usually larger to get same response as a standard reflex.
So the overall
cabinet will be larger to get the same response.
Impedance curve will be close to the same as reflex.
With a very small 3rd hump in the upper impedance
Not so sure, maybe I missed something.
2x 12" woofers in 37 liters? seems very small.
Would be hardly enough for one 12" speaker.
Small cabinets around 1 cubic feet to 1.5 cubic feet
or 28 to 40 liters
Tuning is more likely to jump quickly with small port length
changes.
Looking at the drawing, woofer chambers are
24 and 37 liters so in a model and real life tuning will
be more sensitive to port length.
And with shared wall ports and correction factor
that needs to be accounted for. Probably recommend
round ports for the build.
Far as Double Bass Reflex.
Far as I can tell the overall response wont be
much different than a bass reflex.
One benefit is the upper woofer chamber can be
slightly smaller than a normal reflex. Which
slightly improves power handling.
The tradeoff for slightly more power handling.
Is the second chamber is usually larger to get same response as a standard reflex.
So the overall
cabinet will be larger to get the same response.
Impedance curve will be close to the same as reflex.
With a very small 3rd hump in the upper impedance
Not so sure, maybe I missed something.
2x 12" woofers in 37 liters? seems very small.
Would be hardly enough for one 12" speaker.
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Set QL to Lossless in the bass reflex design for zero displacement at the tuning frequency.
as David McBean (author of hornresp) pointed out you can increase the QL of bass reflex to lossless to get comparable results for DBR and BR.
as far as I understand this also means that the double bass reflex wizard does not account for helmholtz resonator losses.
I tried to simulate a (lossless) bass reflex alignment (blue) to match the DBR box (red):
the main differences here are above 150 Hz, probably (and preferrably, for DBR) outside the usable bandwith.
my bass reflex simulation uses the same total volume as your DBR box (72,5 liters) but a longer port (37 cm lenght, 269 cm2 cross section).
here is the driver power for BR (blue) and DBR (red):
as I wrote above: I would rather use a bass reflex alignment unless there is a big benefit from DBR (which is not the case now, the response is quite uneven).
also keep in mind that the DBR wizard is not entirely realistic as it does not account for losses.
P.S. note that the QL value is not saved with the hornresp record so you need to re-adjust it if you change records.
The QL value will be saved as from the next update:
https://www.diyaudio.com/community/threads/hornresp.119854/page-700#post-7468324
Wow, thank you for your help (and sorry i'm late).
Now i've another question: would this hornresp lossless QL calculation also apply for series bandpass enclosures (the results are also above the other designs) ?
Now i've another question: would this hornresp lossless QL calculation also apply for series bandpass enclosures (the results are also above the other designs) ?
I haven't looked into it, but presumably it would. There are no plans to implement the feature though.
Ok thanks so when i design everything i'll compare with a BR box with similar response with the QL set to lossless (same for horn designs as there is no QL information ?) and then i estimate the potential losses.
Thank you.
Thank you.
System losses are assumed to be zero unless an acoustically lined rear chamber, absorbent filling material or bass reflex loudspeaker is specified.
Bass reflex losses are taken into account using the QL quality factor parameter.
Thank you for making things clearer.
No losses for horn designs even if the cabinet isn't made of concrete ?
A cubo design (throat chamber) also has losses i imagine (if not i son't understand why as it looks like an exponential BR port covering the the driver with the speaker reversed).
No losses for horn designs even if the cabinet isn't made of concrete ?
A cubo design (throat chamber) also has losses i imagine (if not i son't understand why as it looks like an exponential BR port covering the the driver with the speaker reversed).
There will be losses if absorbent filling material is specified.
A throat chamber can be dimensioned to act as an acoustic low pass filter.
Ok so i thought any non-sealed speaker with a chamber would act somehow partly like a BR box (so also with losses). But i can't even figure out if a BR box which is as deep as the thickness of its slot port would act like a TL so i think i still have some things to learn...
Anyway for my project i found some 12HP1030 for 180€ each and the best result i found is around 1-2db more than the DBR graph with a 88l internal volume TL.
But that may be another future topic if i have more questions.
Anyway for my project i found some 12HP1030 for 180€ each and the best result i found is around 1-2db more than the DBR graph with a 88l internal volume TL.
But that may be another future topic if i have more questions.