Twin volt drivers in sealed box enclosures

[jez]

I wish to use two volt b220ss 8" 4Ohm drivers per enclosure in a sealed box, the manufacturer states that ONE unit can be used in a 15 litre sealed box and that this will give -3dB@50 Hz, could I therefore put two of them in a 30 litre box and still get a correct bass alignment but with greater bass extension?. They will have an amplifier to each unit (before someone tells me that my amp will not like the 2Ohm load!).
The finished article (if I ever find the time!) will be a 3 way active speaker with 4th order Linkwitz-Riley crossovers. I had hoped to build a 2 way but it seems that the freebie Volt drivers are bass only and not suitable for bass/mid use.
I hope to look into the use of plaster of paris for the cabinets as one of the best speakers I ever heard had such cabinets(it was made by Townshend Audio, might of been the Glastonbury?)

[richie00boy]

To use x amount of drivers you simply require x times the volume as with a single driver. You do not gain anything in bass extension only overall SPL. They are really designed for vented box use and will sound better in one.

Those drivers can be used as bass-mid (and are in a lot of PA applications), but you either need to accept the beaming and tone or cross them over pretty low (2kHz or lower). This is feasible with an active system.

Instead of plaster of paris which will be a logistical nightmare -- breaking everytime you move it, why not consider a plywood or MDF carcass with automotive fibreglass surface?

[jez]

The drivers were indeed removed from a set of PA loudspeakers!.
The replacement for this unit (B220.2) is said to be very similar, or so I'm told anyway, and they are specified as being usable to only 1KHz by the manufacturer....
This is the second thread I've started on these units (first one seemed to die out with many questions still unanswered!) and everybody seems to be saying "dont use them in a sealed box", why not?, the manufacturer seems to be saying that this is what they were designed for!. I believe (possibly wrongly!??) that sealed box is the best method of obtaining good bass as it is one of the few methods which do not rely on a resonant system to augment the bass output....
I realise that sealed box gives less extended bass, relative to box size, than most other types (this is why it's rarely seen in domestic loudspeakers these days, people want shoe boxes that appear to give bass!) but I would still like to use this method if possible. Is there more than one "correct" box size that can be used? or is it a case of them being designed for a 15 litre box and -3db@50Hz and thats all I'm going to get unless I go ported?,
I suppose that by going for 2 units in 30 litre and greater SPL possible, I could EQ the output below 50Hz to gain extension?, whats the verdict on that one?

[pinkmouse]

Why don't you just download WinISD and have a play yourself? You will learn much more than by us just answering your questions.

[ShinOBIWAN]

I've had a fair few Volt drivers such as the B2500.1, BM2500.4, R3863 and B250.8. Personally my fav is R3863 but this MUST be crossover low ie. <300hz

A word of warning Volts don't do sealed very well.

IMO they sound flat and boring in such enclosures. Mate them with a well designed vented enclosure and they sound dynamic as well as accurate, quite a bit higher SPL too.

[richie00boy]

The first giveaway that they need a vented box is that Qts is quite low. A good way to determine whether sealed or vented is best is to calaculate the efficiency bandwidth product (EBP), which is simply Fs/Qes.

Have a look at the following page to find out more.

http://www.betteraudio.com/geolemon/boxes/types.htm

As has been said simply download WinISD and have a play. You will learn so much, more so much faster.