Cabinet for BMS 18N862

Frode

Member
2003-05-04 8:49 am
Bergen
I'm planning to use 4 of these drivers to fill in below a pair of Danley SH50. I have 4 ch of Hypex UCD400ST(400W) amps that I would like to power them with, but this can of course be changed. Room size is ~3900ft^3(110m^3) and the SH50s are driven by a 20W/ch amp. Any cabinet suggestions?

BMS 18N862

Frode
 
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  • BMS 18N862, VB = 178.1 L, FB = 22.9 Hz.jpg
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  • BMS 18N862, VB = 178.1 L, FB = 22.9 Hz (2) F3=33 Hz, max.SPL@1.00 m, 1x128.5 dB, 2x131.5 dB, 3x1.jpg
    BMS 18N862, VB = 178.1 L, FB = 22.9 Hz (2) F3=33 Hz, max.SPL@1.00 m, 1x128.5 dB, 2x131.5 dB, 3x1.jpg
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Frode

Member
2003-05-04 8:49 am
Bergen
Frode,

1.What is the largest cabinet size acceptable?
2.How low in frequency response are you looking for?
3.How loud do you want the LF to be?
4.Are you planning to use digital processing for the crossover?

Art

1. This is a bit difficult to answer. I've simulated cabinets in the 5-10cu.ft range, while I don't think the DTS-20 with more than 18cu.ft is too big. It depends on the shape of the box.

2. I think 20-25Hz would be enough.

3. Most of my listening is at low levels. I once measured SPL in listening position, and it was below 90dB. Maybe 100dB is my upper limit. How much headroom do the subs need above this? 10dB? 20dB?

4. Yes, I use Audiolense software.

Frode
 
1. This is a bit difficult to answer. I've simulated cabinets in the 5-10cu.ft range, while I don't think the DTS-20 with more than 18cu.ft is too big. It depends on the shape of the box.

2. I think 20-25Hz would be enough.

3. Most of my listening is at low levels. I once measured SPL in listening position, and it was below 90dB. Maybe 100dB is my upper limit. How much headroom do the subs need above this? 10dB? 20dB?

4. Yes, I use Audiolense software.

Frode
If you are not into loud and "loudness contoured" bass, I'd think 110 dB would be plenty.

Since your SPL needs are modest, but your power is limited (in comparison to what the BMS18N862 can handle), I'd suggest a pair of bass reflex subs tuned to 20- 25 Hz. You could make them the same footprint as the SH-50, or rectangular with the same frontal area for aesthetics.

Using a "V" loading will get the acoustic center very close to the SH-50 at the crossover point, and allow the frontal area to be the same width as the SH-50.

I'd also suggest the port be tapered each end. You will need to experiment with the size and depth as it will vary somewhat from a simulation using a non-tapered port.

The sketch below shows top, front and side views of my suggested cabinet design.

The cabinet will be undersized, so will roll off in the low end, but in room response may not need much EQ to bring it flat to an F3 of 20- 25 Hz.

I am curious why have you chosen such expensive, large cone high displacement drivers when your SPL and extension requirements could be easily met with drivers a fraction of the size and cost using smaller cabinets?

Art
 

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Frode

Member
2003-05-04 8:49 am
Bergen
I am curious why have you chosen such expensive, large cone high displacement drivers when your SPL and extension requirements could be easily met with drivers a fraction of the size and cost using smaller cabinets?

Art

Well, I'm not quite sure of my own requirements and I don't want the drivers to be the limiting factor(of course, they always are in a way).

I bought the 4 ohm version of the driver, and it seems like the parameters are a bit different, see attached file.

Frode
 

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  • 18N862-4 TS.pdf
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Your parameters come attached to the driver correct? So they should be actually their measurements or a standard that where taken in the factory?!

With small experience I have factory parameters are the standard (for one year version) and then you can have some (new) drivers that are all different in their universe but close to a deviation percentage from their set master parameters. So all measurements taken from them are all different. Some manufacturers have very tight restrictions or different brands for the same loudspeaker driver. It all is reflected in the price just like matched pairs.
 

Tytte71

Member
2010-10-17 9:55 am
Hi Frode. If you already have ordered the drivers, then there is not much left to discuss :) They are great drivers. For your purpose tho, it seems like a little overkill both compared to the selected Hypex amps and your need for loud bass.

On the other hand the drivers will only utilize its stroke area where they are more or less flat linear. With 400W of amps on each of them you will be able to play 114dB@20Hz or 120dB@30Hz - 4pi + room gain in sealed cabinets of 75l netto. BTW, same cabinets that I have used for my 4x862 ...they can be used with 1400W@20Hz in 75l sealed cabinet without exceeding datasheet xmax.

However, Vance Dickason at Voice Coil Magazine Klippel tested a pre-release 8ohm version of the driver in feb.2012 and concluded:
Displacement limiting numbers calculated by the Klippel analyzer for the BMS 18N862-8 were XBl @ 70% (Bl decreasing to 70% of its maximum value) was 15.9 mm and for XC @ 50% (compliance decreasing to 50% of its maximum value) was 14.3 mm, which means that for the BMS 18N862-8, the compliance is the limiting factor for the prescribed distortion level of 20% for using this driver as a subwoofer. Again, as with the BMS 15N850V2, data this good is about as good as it gets. Plaudits and Kudos to the engineers at BMS!​
Since the Klippel measurements where done on early model drivers and the T/S parameters have changed a lot to the production model, there can also have been made changes to the suspension or motor system... I don't know.

Anyway a great driver and 4 of them in sealed cabinets will most probably be plenty with your current setup:)
 

Crafty

Member
2008-10-17 5:47 pm
IMG_1475s.jpg
[/IMG][/IMG]Hi Frode,

I have just completed a single reflex cabinet for the BMS18N860 which has the same chassis and motor- 862 has more linear surround. I ended up with a 200 litre net volume, tuned 24hz with 3 x 104mm diameter ports flared inside and out. The ports ended up approx 75mm shorter than modelled at 465mm long. Tuning frequency was checked by impedance measurement and signal generated by Smaart live.

It took quite some time to break the driver in but it sounds superb, vey clean and very low. Great for hi fi and cinema use. I don't think the UCD400's will do these drivers justice. I am driving mine with an MC2 MC1250 - a very beefy class A/B. Currently driving it from one channel 850w @8R which approximately corresponds to the subs excursion limits around 20hz when used for cinema LFE. If used for music it would be better bridged! don't skimp on the bracing!
 
BMS 18N860 vs. BMS 18N862

Crafty, nice project, congratulations.
The BMS 18N860 has a better low extension than driver BMS 18N862, lower extension simulated F3@30Hz and better output@20Hz ~2/3dB, w/ideal box +25L than BMS 18N862 and max.SPL@1.00 m, 1x127 dB. They are in fact very similar as you said. :)
 

Frode

Member
2003-05-04 8:49 am
Bergen
Hey Frode !! Can you please tell me!
What is the largest cabinet size acceptable?

office furniture Florida

I guess around 10 cu.ft per driver, but I'm open for bigger suggestions.


After some delivery issues I ended up with the 8 ohm version, they'll arrive tomorrow. I've also decided to look for other amps than the Hypex, but I might start with them.

Frode
 
I guess around 10 cu.ft per driver, but I'm open for bigger suggestions.


After some delivery issues I ended up with the 8 ohm version, they'll arrive tomorrow. I've also decided to look for other amps than the Hypex, but I might start with them.

Frode
The four channels of Hypex should still be enough at 8 ohms for your listening level needs.
You could probably bridge mono two sides in to 4 ohm load for 6 dB more headroom as long as they have a large heat sink area, and you don't lean on them with EDM all night ;).

Art
 
Excellent Driver, in a 250-275 L enclosure with a tuning around 27 Hz it will surely deliver the Bass that you expect. Its of course not the cheapest driver on the market, but I would consider it between the 5 best 18"Drivers on the market for this kind of use. Sadly BMS finished the 18N860, that was a bit better for subwoofer applications! But to be honest, the Hypex modules that you have are surely okay, but do you drive a Ferrari with normal unleaded fuel? A friend of me has the same BMS driver in use, 250L tuned to 27,5 Hz, but they are fired by a old Macrotech 5000. Boy that kicks a....! :)
 

Crafty

Member
2008-10-17 5:47 pm
Thanks Djim; the performance of this driver / box has exceeded my expectations. The quality of the bass is difficult to describe but its transient performance and extension are both as good as I have heard to date.

I can highly recommend it to anyone wanting an extremely capable hi fi / cinema sub if your wife / girlfriend will let you!