Boston Acoustics RS8 subs need enclosure, help anyone? - diyAudio
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Old 11th January 2004, 03:11 PM   #1
rchua77 is offline rchua77  Singapore
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Default Boston Acoustics RS8 subs need enclosure, help anyone?

Hi all,

I found a pair of old Boston Acoustics Rally RS8 8inch subwoofers in my storeroom. I need help building an enclosure for them. They're both 4ohm each.

Could someone help design an enclosure and the crossovers for them?

Tech Specs
Fs = 34
Qes = 0.42
Qms = 2.55
Qts = 0.36
Vas = 41.0
Re = 3.64
Le = 0.0
Sd = 234
Xmax = 10.2
Pe = 250

Any help would be appreciated most gratefully!
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Old 11th January 2004, 03:32 PM   #2
sreten is offline sreten  United Kingdom
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Some bass alignments :

For both units you'll need around 2cuFt reflex.
Max you can sensibly use is 3cuFt.
The drivers are not particularly suited to sealed box loading,
but you would be OK with a seled box of ~ 1cuFt.

sreten.
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Old 12th January 2004, 09:30 PM   #3
rchua77 is offline rchua77  Singapore
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Hey, thanks for the guidelines. It gave me some ideas.

I tried out some figures for myself and came up with this gain plot. Comments and suggestions to make improvements?

By the way, wats tuning frequency and the vent mach (red/green colour) ?

Thanks!
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Old 12th January 2004, 09:51 PM   #4
sreten is offline sreten  United Kingdom
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50litres at 34Hz sounds reasonable for a box with both drivers.

Tuning frequency in the frequency of the port / vent.


Vent mach is the air speed in the vent. A port 2" diameter and 4"
long has the same frequency as a port 4" diameter and 16" long.
The bigger port has lower airspeed, winISD changes colour if
the port airspeed is too high.

Play around with the diameter of the port under vents.

sreten.
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Old 13th January 2004, 12:36 PM   #5
rchua77 is offline rchua77  Singapore
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Any suggestions for a passive crossover?

I would like to have the subwoofers have an impedance of 8ohms, since they're 4ohms each, a serial connection would seem much safer than a 2ohm load.

What values should I use for the inductor, capacitor and resistor? What kind of layout should I follow?

Thanks!
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Old 13th January 2004, 06:43 PM   #6
sreten is offline sreten  United Kingdom
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A passive croosover is extremely unlikely to work well.

You haven't even mentioned the main pair of speakers.

Get a plate subwoofer amplifier.

sreten.
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Old 14th January 2004, 03:07 AM   #7
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Graph might be a little more visible with light background.
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Old 15th January 2004, 06:28 PM   #8
rchua77 is offline rchua77  Singapore
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Hi everyone again,

I think I've decided to run an active crossover system for the woofers in addition to my bookshelf AE Aegis ONE speakers since the AE has one pair of speaker terminals. Noticed they're alittle low on bass.

I'll bi-amp them with one amp driving the Aegis ONE and another amp driving the BA subs. Sort of like a mix and match 2 way system.

I'm not too sure which enclosure is more suitable for the BA subs, closed or vented. I seem to keep running into ridiculous vent lengths when toying around with the tuning frequency. Anyone know whats a good tuning frequency for the subs ?

Suggestions and recommendations would be appreciated.
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Old 15th January 2004, 07:22 PM   #9
sreten is offline sreten  United Kingdom
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Quote:
Originally posted by rchua77
Hi everyone again,

II'm not too sure which enclosure is more suitable for the BA subs, closed or vented. I seem to keep running into ridiculous vent lengths when toying around with the tuning frequency. Anyone know whats a good tuning frequency for the subs ?

Suggestions and recommendations would be appreciated.

As I've already stated the BA drivers are not suited to sealed
subs. Tuning frequency in a 54 litre box for the pair is 27 Hz
to 38 Hz.

Lets say 30 Hz.
For a 54 litre box = a 8.2cm (~3") diameter and 26cm (~10")
length, or 6.8 (~2.5") diameter and 17 cm (~6.5") length.

I'd suggest 75mm and 213mm.

Note graphs are for a single unit.

sreten.
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