Some Assistance if you please

[Kujo]

Hi,

My boss' wife got sick of his speakers and so he was giving them away. Not to look a gift horse in the mouth I though i might take them off his hands as something to play with.

On first inspection they seemed reasonable enough. 4 way system with 15", 4", 2.5" and 2" drivers. The boxes were made by Peterson Speaker Laboratories. The specifications listed on the box are:
BD Series BD15
Freq Range: 35Hz - 20kHz
Sensitivity: 92dB
Power Handling Capacity: 250W

I got them home and the first thing I did was take the drivers out to have a look at what they were. In this process i noticed that the enclosure itself was made of chip board and not well braced. There was also with no baffling inside at all which I found surprising.

Anyway the point of all this is while the drivers are marked I suspect these are quite old (as in mid 1980's) and I have not been able to find any information on their specs. The markings are:
15”: BJD FH-1540, 8 Ohm, Taiwan
4”: BD TM-4001, 8 Ohm, Taiwan
2.5”: BD 66FT38A2, 8 Ohm, Taiwan
2”: BD A80A60DM-02HT, 8 Ohm, Taiwan

I was wondering what the best approach is to characterising these drivers. My key concern is the individual power rating. Is there a sensible way to reverse engineer a safe operating level from the overall 250W number above? Has anyone an idea on how to approach this?

I welcome any advice you can provide.

Thanks

Kujo

[jerome69]

Hi !

Did you listen to the speaker ? What do you think ?

Some photo will talk more to us ...

The Box is Bass Reflex ? if yes I think the baffling is not important.
You can buy a cup for the 4"

Bracing the box and add damping could be a good improvement.

Could you do a schematic of the crossover ?

Cheers.

[Kujo]

Thanks Jerome.

I'll do up a schematic and try and organize pictures.

Might take a couple of days.

Kujo

[sreten]

Hi,

I'd take that power rating with a pinch of salt. For an idea of power
ratings for each driver look up similar cheap drivers at parts express.

Sensibly use them with just about any domestic amplifier under 100W.

Typically such speakers work better with the port sealed off, or detuned
by lining the port with 1/2" thick open cell foam (3diax length peices).

I assume the midrange is closed back, and cannot use a cup.

rgds, sreten.

[Kujo]

Thanks for that idea on the power ratings Sreten i did not think to do that.
The boxes are sealed units not bass reflex.
The midrange is indeed a closed back unit.

I was not particularly fussed on the boxed anyway and was looking to see if the drivers were worth using in a different fashion.

Kujo

[Moondog55]

Chuck em in the bin
There was a time when Petersen were OK but not for the last 20 years'
Cheap boxes and even cheaper generic drivers with simple XOs
I know I made the mistake many years ago of buying a pair; keep them for parties where all you need is noise; they are OK for that
Bass isn't bad but that sealed back midrange is a POS and suffers from very bad reflections internally and the FR is as ragged as a mountain range with huge swings.

[Kujo]

Hey Moondog55.

Thanks for the advice. I suspected as much. There just wasnt any real hint of quality.

Perhaps they are best used as an active load for amplifier testing.

Thanks everyone for your assistance.

Kujo

[PeteMcK]

maybe the woofers are OK for OB experiments if they are High Q (have a relatively small magnet)?

[Kujo]

Hi PeteMcK,

I'll put a picture of them up over the weekend as i have not seen enough 15" woofers to tell if the magnet is small or not.

Kujo

[sreten]

Originally Posted by Kujo

I was not particularly fussed on the boxed anyway and was looking
to see if the drivers were worth using in a different fashion.

Kujo

Hi,

Post details of the crossovers, though I'm not expecting much.

It may be possible to improve them somewhat. The other alternative
is if the bass unit is is half decent and they aren't boom boxes is to
ditch the rest of the drivers and use them as the bass end of a two
box 3-way, probably work quite well with an AV amp for HT.

rgds, sreten.