I need some help. I just finished building a new 3 way speaker, but the bass is . . . underwhelming.
I'm using a Dayton SD215A-88 in a 36.8L BR cabinet tuned at 31Hz (QB3 alignment). Using this port (area = 26.4cm2) WinISD calculated the port length to be 18.1cm, so that's what I started with. Unfortunately, the bass is not what I expected it to be. So I measured the port and driver responses (nearfield) and summed them, with the port response attenuated -7.2dB to compensate for the surface area difference compared to the driver. I did this for the port length calculated by WinISD (~18.1cm), and also for 16.0 and 13.5cm. This didn't improve things. It seems it's not a port tuning issue, but rather lacking performance from the driver.
I attached the REW file containing the measurements for three different port lengths. Does anyone have a clue why the bass is rolling off so soon?
This is the summed response (driver+port) for the WinISD calculated port length. There's a huge dip in the critical area.
I'm using a Dayton SD215A-88 in a 36.8L BR cabinet tuned at 31Hz (QB3 alignment). Using this port (area = 26.4cm2) WinISD calculated the port length to be 18.1cm, so that's what I started with. Unfortunately, the bass is not what I expected it to be. So I measured the port and driver responses (nearfield) and summed them, with the port response attenuated -7.2dB to compensate for the surface area difference compared to the driver. I did this for the port length calculated by WinISD (~18.1cm), and also for 16.0 and 13.5cm. This didn't improve things. It seems it's not a port tuning issue, but rather lacking performance from the driver.
I attached the REW file containing the measurements for three different port lengths. Does anyone have a clue why the bass is rolling off so soon?
This is the summed response (driver+port) for the WinISD calculated port length. There's a huge dip in the critical area.
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2” diameter vent. Tuning looks good, as does the vent.
So i would suspect that maybe you haven’t gotten the rest of the system right. Or the room and placement are really bad.
Given the low sensivity, mids will need to be about 82-83 dB.
dave
So i would suspect that maybe you haven’t gotten the rest of the system right. Or the room and placement are really bad.
Given the low sensivity, mids will need to be about 82-83 dB.
dave
Loading your winISD file I noticed the port you use will hit the recommended highest vent mach (17ms) at 14 watts.
Try using a pair of them 40.4cm long to get the vent mach below 17ms at 40 watts, which will power the driver to xmax at approx 43Hz.
Also you might need a highpass filter around 28Hz to control cone excursion below tuning frequency.
edit. try measuring outside away from walls groundplane to see if its a measurement issue.
Try using a pair of them 40.4cm long to get the vent mach below 17ms at 40 watts, which will power the driver to xmax at approx 43Hz.
Also you might need a highpass filter around 28Hz to control cone excursion below tuning frequency.
edit. try measuring outside away from walls groundplane to see if its a measurement issue.
The rest of the system isn't much. A Hypex Ncore based amplifier (NC252MP), with a Topping E30 DAC and a Pi4 with Volumio as the source. For measurements the source is replaced for a Behringer UMC22 audio interface. Thus far I've only done nearfield measurements, which should rule out room or placement issues. A farfield full range measurement would not make a lot of sense, as it's a relatively small room which will cause lots of reflections. But even with the added room gain my ears tell me there's something wrong with the bass.
You're right, I should have used a larger diameter port. Will remember to check for that in the next build. But chuffing noise is not my main concern right now.
I had a similar response with the dip above tuning on a pair of beyma 15's/ I concluded the TS parameters were out compared to the published ones so ended up tuning 10Hz higher to lose the dip.
I'm assuming you have checked the box / seals on any speaker connectors etc to make sure there are no air leaks ? Also most bass drivers have a natural roll off below ~100Hz which is not accounted for in winISD. (spec sheet shows a 10dB drop from 80Hz to 20Hz on your driver)
I'm assuming you have checked the box / seals on any speaker connectors etc to make sure there are no air leaks ? Also most bass drivers have a natural roll off below ~100Hz which is not accounted for in winISD. (spec sheet shows a 10dB drop from 80Hz to 20Hz on your driver)
Ah, okay. There's a Dayton RS125 for the mids and a SB Acoustics SB19ST for the highs. I can supply the VituixCad file if needed. Here's a pic of the system (the Denon amp isn't in use anymore).
Hmm, 344/2/~43Hz = 4 m, so got any parallel walls/whatever as down low these major peaks, dips are room related and if so, then move the speaker.
What is your X over to the mid and what crossover do you use? It could be the series inductor in the crossover combined with the second impedance peak that cause the peaking at about 100Hz. Should be fixed with a LCR circuit to flatten that second peak.
This is the crossover. All 2nd order. XO points were 370 and 2.2kHz. Crossover was designed using individual driver measurements (quasi-anechoic). I already noticed an early roll-off of the bass from the raw driver measurements, but didn't pay too much attention to that, as my focus was mainly on getting a linear-ish FR.
I attached my VitiuxCad file including individual driver measurements.
I attached my VitiuxCad file including individual driver measurements.
I don't know much about TL's, but here's a Sketchup dwawing of the speaker with a side panel removed.
The cabinet is airtight (apart from the port ofcourse). I know WinISD only shows the acoustic rolloff of the cabinet, and doesn't take the driver's actual FR into account.
I'm still puzzled about the huge dip between 30 and 70Hz. It should roll off gradually, not dip 13dB from 70 to 45dB and then rise 8dB again towards 30Hz.