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Multi-Way Conventional loudspeakers with crossovers

Acoustic vent for midrange driver
Acoustic vent for midrange driver
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Old 22nd May 2020, 11:39 AM   #1
MrGecco is offline MrGecco  Norway
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Default Acoustic vent for midrange driver

Hello

Looking at the possibility to use the Seas W12CY003 as the midrange. Thinking about using a 6,4 litre-ish sealed cabinet for it. However I've seen some other mid range drivers with acoustic vents. Would there been a benefit to use a acoustic vent on the Seas? And would it affect the enclosure size?
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Old 23rd May 2020, 04:41 PM   #2
Inductor is offline Inductor  Portugal
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The size of enclosure is very much similar. BR has a port to add to NET volume and it's a long port so to say. It would make also a nice OB (open B). A BR would be more powerful with 30W for Xmax. Sealed less than 5W for Xmax. They cross nice @100Hz (+/-) neading further adjustments. (Figs. sealed vs. ported)
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Last edited by Inductor; 23rd May 2020 at 04:46 PM.
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Old 23rd May 2020, 06:08 PM   #3
MrGecco is offline MrGecco  Norway
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Sorry, I am not sure I'm following you. I was thinking about acoustic vents. They're similar to BR obviously. As far as I know, acoustic vents doesn't extent the frequency extension in the low end, because of the port stuffing. The frequency extension isn't important anyway as there will be low bass drives on the speaker as well. Should AVs be sized the same as BRs?
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Old 23rd May 2020, 06:31 PM   #4
GM is offline GM  United States
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IME, the pioneer's conclusion that the vent can't be too close to the driver is the best way, so 'gap' the driver from the mounting hole and if you need a stronger 'leak' [paper thin often suffices, so have used mechanic's 'feeler' gauges], then do the stuffing 'thing' using open cell foam, carpet felt or similar for an adjustable density 'gasket'.

BR patent: US1869178A - Sound translating device
- Google Patents


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Old 23rd May 2020, 06:59 PM   #5
weltersys is offline weltersys  United States
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MrGecco, you may be trying to get more information about "Aperiodic Vents", which serve a different purpose than bass reflex vents.

My first thought from your post was you were interested in Vented Mid Range, and brought back memories of the Electro-Voice VMR from the 1970s, a 6" cone with an integral vented enclosure, covering 600 Hz to 4kHz.
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Old 23rd May 2020, 09:01 PM   #6
Galu is offline Galu  Scotland
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Aperiodic vents have the action of reducing the Q of a driver's resonant frequency as well as permitting a smaller enclosure.

However, I assume that a midrange driver would not be allowed to operate near its resonant frequency (thanks to the band pass crossover) and that an aperiodic vent would be of no consequence.
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Old 23rd May 2020, 09:43 PM   #7
MrGecco is offline MrGecco  Norway
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Thanks for all the answears

Aperiodic vents might be what I'm talking about. From what I remember the idea was basically a BR with a stuffed port. I thought a ported enclosure would always have a tuning frequency, and therefore not be considered an aperiodic vent. I suppose the stuffing makes it apreodic?

Regardless, would an aperiodic vent be fitting for midrange frequency usage? As far as I understand they allow smaller enclosure sizes and better transient response but slightly higher f3.

At the end of the day I'm out after a small enclosure with good/best transient response.
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Old 23rd May 2020, 10:00 PM   #8
Galu is offline Galu  Scotland
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An aperiodic event is beneficial to a woofer since it flattens the bass resonance peak.

By lowering the Q of the peak, it improves the transient response at bass frequencies.

However, as I said above, you would not be operating a mid driver at its resonant frequency.

Here's some information on the aperiodic vent which you may not have seen.

Aperiodic Closed Box Loudspeakers
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Old Yesterday, 12:00 AM   #9
GM is offline GM  United States
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Quote:
Originally Posted by MrGecco View Post
Thanks for all the answears

Aperiodic vents might be what I'm talking about. From what I remember the idea was basically a BR with a stuffed port. I thought a ported enclosure would always have a tuning frequency, and therefore not be considered an aperiodic vent. I suppose the stuffing makes it apreodic?

Regardless, would an aperiodic vent be fitting for midrange frequency usage? As far as I understand they allow smaller enclosure sizes and better transient response but slightly higher f3.

At the end of the day I'm out after a small enclosure with good/best transient response.
You're welcome!

Depends on what type/how much stuffing one uses.

Right, it's what I've used it for, so headed in the right direction.

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Old Yesterday, 07:16 PM   #10
oldspkrguy is offline oldspkrguy  United States
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Quote:
Originally Posted by MrGecco View Post
Hello

Looking at the possibility to use the Seas W12CY003 as the midrange. Thinking about using a 6,4 litre-ish sealed cabinet for it. However I've seen some other mid range drivers with acoustic vents. Would there been a benefit to use a acoustic vent on the Seas? And would it affect the enclosure size?
I am getting ready to use the Scan Speak "Flow Resistors" (similar to the Dynaudio "VarioVents"). These are not for tuning like a Bass Reflex/vented box; they are mostly used for woofers in a closed box that is too small making the Q too high (ie boomy bass). A closed box rolls off the lows at 2nd order (12 dB/octave); a vented box rolls off the lows at 4th order (24 dB per octave) and an "APERIODIC" vent type closed box rolls off the lows at 3rd order (18 dB per octave). For use on a midrange driver well above resonance; you probably won't gain any advantage because these are primarily used to lower the impedance peak of a woofer. If you are using a LARGE midrange without a X/O on the low end for some reason; then these flow resistors could help.
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