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This is the reason I would not recommend the AE TD18H in an 8th order BP.
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Even though this might be quite fun once built!!!
This is not optimized in any way. It is a fast and not thought through example of what range of enclosure sizes we are talking about.
If built out of 36 mm birch plywood with lots of bracing (to keep the huge panels reasonably stiff) then I guess we are looking at something quite close to a cubic meter.
A very fun and capable home theater sub if someone has the space and love buying birch plywood in bulk.
it's all about tuning :On left, your 6th. On right, a 8th, same size, same efficiency, same response. Vent velocity all < 20m/s. It is probably not realistic built though.
But again, there's more bandpass effect EDIT : Lp3 can be set 24-36mm (plywood thickness) without that much change
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1/2 Simed as TH so hornresp can show impulse & spectrogram.
EDIT : since i had 10 minutes playing with hornresp
3/4 A front bandpass, with two back reflex chamber...+/- same bandwith, +/- same size, somewhat cleaner and smoother. Max internal port velocity 16m/s. Simed as OD, but can be simed as BPC in hornresp to tweak vent velocities.
Papasteack, can you explain a bit more about "1 high pass, 5 peak eq" on your design?
Graph looks prefect. Bandwith 25/30-100hz possible?
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Hornresp allow to use filter. using filter, in the 25-100 hz, this design can get the same response curve as Circlomanen's. With 1 high pass filter, 5 peak eq. But i prefer a lot without, as it is smoother. It's just a kind a 6th bandpass, using two chambers instead of one on low path, that give more tweaking possibilities, and gives here a nulling effect of a ringing wich is part of the tweaking.
In this 8th order BP we used two 11 cm diameter pvc pipes for each section for a total port area of 169 cm2. This is for a single 12 inch driver with low power handling and a short xmax. We build this 8th order as a joke to prank a friend of my son. It was revenge for all the horrible bassreflex boxes I have got as a birthday gift over the years. Helmholtz sounds so horrible that I wanted to stack as many Helmholtz-resonators and as many ports as possible in a single box.
Even with this low power density 12 inch driver it is easy to hear port chuffing at remarkably low power levels (200 watts or so). You can clearly hear the internal ports even though they somewhat drown out under the noise from the exit ports.
Since this was built as a joke only to prank a friend of my son, we are very pleased with the result, but for serious use I would never use this small ports. Sd/2 is a minimum and this is usable if you use flared ports.
If you want to build an 8th order or 6th order BP with a high power high excursion 18 inch driver, then port cross section area becomes quite important.
Stuffing + flared port.
All about compromise.Big port mean longer means resonnance in low range. Easy to see with parallel bp 6th in honresp choosing the output. Mixed blended in serie-tuned 6th last chamber, but that doesn't mean in doesn't happen. Of course, those resonnance do not dominate response in usable bandwith so the sum doesn't show it that much. Still, if it can be avoided, it's a good thing. It depend the power involved. For higher power, simply use multiple box, it would be more realiable or accept higher frequency roll off - typical compromise done in PA.
Always a good read + little useful dedicated tool : Port Flares - Evaluation of noise
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Here is a 6th order series tuned BP with a DD710D4 that we built for a friend.
This measurement is taken in my living room with the Umik 30 cm from the mouth of the BP.
This large midbass peak works wonders for the punch and attack in the car cabin. The cabin gain profile does smooth out the response a lot. In-car measurements coming tomorrow. The driver is brand new and I guess it get closer to the simulation once the suspensions loosen somewhat. They are very stiff at the moment.
It does sound a bit strange in my livingroom, but it is very impressive and fun in the car, with a much improved balanced sound and a great punch.
Music tends to be very physical and tactile once we start cranking up the volume. With a few kilowatts it becomes quite painful to sit in the car.
This measurement is taken in my living room with the Umik 30 cm from the mouth of the BP.
This large midbass peak works wonders for the punch and attack in the car cabin. The cabin gain profile does smooth out the response a lot. In-car measurements coming tomorrow. The driver is brand new and I guess it get closer to the simulation once the suspensions loosen somewhat. They are very stiff at the moment.
It does sound a bit strange in my livingroom, but it is very impressive and fun in the car, with a much improved balanced sound and a great punch.
Music tends to be very physical and tactile once we start cranking up the volume. With a few kilowatts it becomes quite painful to sit in the car.
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I suddenly found some small traces of energy after dinner so I managed to measure the in car-cabin response.
I dialed down the sensitivity of my microphone input and measured the response at 120 dB (27 Hz) at the driver headrest in order to get a good THD graph at some real spl. I don´t know how much of that measured THD that is actual driver or port distortion and how much is random noise from the interior of the car buzzing and rattling.
Once the car cabin gain curve gets superimposed on the raw near field response it becomes quite clear as to why I like to design my bandpass boxes with a large midbass peak. This TH6-S got a very pronounced midbass peak since I know the car cabin response will add lots of gain below 55 - 60 Hz.
It was not enough. It was the best I could do within the quite constrained max dimensions I had to work within. DSP can take care of the rest.
It does sound great as it is now. I really like the punch and attack, and I goes deep enough for most music - even for an 18 year old basshead like my son.
Lots of fun!!!
I dialed down the sensitivity of my microphone input and measured the response at 120 dB (27 Hz) at the driver headrest in order to get a good THD graph at some real spl. I don´t know how much of that measured THD that is actual driver or port distortion and how much is random noise from the interior of the car buzzing and rattling.
Once the car cabin gain curve gets superimposed on the raw near field response it becomes quite clear as to why I like to design my bandpass boxes with a large midbass peak. This TH6-S got a very pronounced midbass peak since I know the car cabin response will add lots of gain below 55 - 60 Hz.
It was not enough. It was the best I could do within the quite constrained max dimensions I had to work within. DSP can take care of the rest.
It does sound great as it is now. I really like the punch and attack, and I goes deep enough for most music - even for an 18 year old basshead like my son.
Lots of fun!!! Attachments
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