Large DIY sub required on a budget

[Sastusbulbas]

Hi all,

I have a large Yamaha driving Cerwin Vega V-152 PA speakers,103db sensitivity, 8ohm, 600w power handling with a 15" mid/bass driver, bass drops off around 50hz-40hz.

A couple of small home AV subs have been tried in this system, it is used in a large 60-80ft room, but I feel I have to build something cheap and cheerful to keep up with the CV's.

I have building materials such as 1" chipboard, 18mm mdf, cable, fixings, dampening and such.

What I need is a driver choice, optimum size cabinet, sealed or ported, and amplification and low pass filter/crossover.

I was initially thinking of something similar to the JBL 18" theater series sub enclosures around 225 litres ported with a basic 18" driver, with a passive filter and bridged budget Alesis or such.

I have also been offered a 12" fusion car sub with a ported carpered cabinet with green trim?

Can anyone recommend a bass driver of sufficient speed sensitivity an LF extension to compliment the CV's budget around £100 - £200?

Would a car sub be sufficient? and am I better with a sub panel amp or a PA amp and pasive EQ, the electronics can always be upgraded later so I guess the driver and cabinet design are most important?

Cheers,
Steve

[cixelsid]

One of Bill's plans will work for you

http://www.billfitzmaurice.com/

[Sastusbulbas]

Well I am currently looking at the Fitzmaurice and Rythmik sites

[jbell]

BFM FLH's in 2pi space have a typical 'rising' response. Meaning that 40hz is -13db down from 100hz. They must be inside in a corner, or use a lot of them to flatten out the response.

The tapped horn threads may have the info you are looking for.

[littlemike]

Missing two fundamental bits of information here:
How low do you want to go?
How loud do you want to be?

Most of the PA type tapped horn designs also roll off below 40 Hz, but have serious impact from 40-120 Hz. The home theater type tapped horns play lower (in some cases below 20 Hz), but rely on proper placement to get the best performance (they generally sound a lot better in a proper corner).

Some car subs work very well in tapped horns, as do some PA drivers. Bigger woofers are not always better in tapped horns. Additionally, obtaining good results with a DIY tapped horn is totally contingent on accurate measurements, accurate modeling, and accurate construction.

[Sastusbulbas]

I would like to match my main speakers, which have a sensitivity of 103db. They have 15" mid/bass units.

I would like to get a very low and even response, box size is not much of an issue.

I am currently thinking of a Fitzmaurice THT design with a UK sourced driver with these specs (though initially it will be temporarily housed in an appropriate ported enclosure)

Adire Tempest 15" (5 litre displacement)
* Nom: 2 x 8 Ohm
* Power: 750 W
* Fs: 18.8 Hz
* Qms: 6.7
* Qes: 0.4
* Qts: 0.39
* Vas: 317L
* Sd: 779 cm^2
* Xmax: 16.4mm
* Re: 3.5 Ohms
* Le: 2.9 mH
* BL: 14.2
* Mms: 195 grams
* SPL: 89.1 dB @ 1W, 1m

Another option may be a Wembley Loudspeaker BL-600 18" driver, in a large ported enclosure I guess?

Usable Frequency: 20-hz-2khz
Power Handling(cont. RMS): 600watts
Power Handling(Peak Average): 800watts
Nominal Impedances offered: 4/8/16 ohms
D.C. resistances: 2.8/5.2/11 ohms
Sensitivity (AV 1watt/1m): 100db
Sensitivity(Peak Usable): 106db
Qts: 0.24
Q. Max: 19mm
Vd.: 814cc
Vas.: 0.53m x 3
Magnet Assemblies: 9.7kg(21.4lb)
Voice coil material: Copper HML
Voice coil former: Aluminium
Voice coil sizes: 77mm x 25mm
3" x 1"
4 layer
Chassis: Cast aluminium
Net weight: 13kg(35lb)
Shipping weight: 16kg(35lb)
M.M.D.: 140grms
B.L. Factor: 21 tesla

I am now thinking of a BK Electronics plate amp,
http://www.bkelec.com/Modules/bsbpv500.htm

The room is around 60ft by 80ft

[jbell]

I've built the THT - it's a good box, put it in a corner. But it is big... be warned. You should consider some provision for handles, just for moving it into place. Without it, it's a 2 man job to move, not due to weight, but just due to size, and nothing to grab on to.

BFM member Wisounds built 8 of them, and chose to make the driver access panel on the front, which ended up being a REALLY good thing. Without the panel on, it's more sensitive in the music range (40hz on up) and with the panel on, it's lower total output, but flatter down to it's 23hz horn length for HT LFE. Having that option to 'tune' the cabinet is a big plus.

Without the panel, it's almost a scoop, tapped horn, or some kind of hybrid cabinet.

[bubblersound]

Without the panel on, it's more sensitive in the music range (40hz on up) and with the panel on, it's lower total output, but flatter down to it's 23hz horn length for HT LFE. Having that option to 'tune' the cabinet is a big plus.
Without the panel, it's almost a scoop, tapped horn, or some kind of hybrid cabinet.

This is why I use my Labhorns without the access panels. Keep in mind the panels are on the side and not all that close to the horn mouth. I will add that it affects the upper bass response. I haven't figured out what category this type of enclosure falls under. I've made some adjustments since the first build, but that's a whole new topic.

[GM]

Originally posted by Sastusbulbas
I would like to match my main speakers, which have a sensitivity of 103db. They have 15" mid/bass units.

I would like to get a very low and even response, box size is not much of an issue.

Adire Tempest 15"

To go low at ~103 dB either requires a HUGE cab or many drivers and semi-huge cab. Anyway, the Tempest will in theory get you close enough backed up against (or built into) a (false) wall once damped and maybe with some EQ if damping plus XO point/slope doesn't get it flat enough for you in-room, but it's at the expense of being ~2494 L (net):

GM

[GM]

Originally posted by bubblersound

I haven't figured out what category this type of enclosure falls under.

Technically, it's a BLH and depending on how it's oriented to a wall/floor or corner boundary could make it a TH.

GM