Precision Devices PD.2450 in OB, or alternatives ?

[grimskullcrushe]

Hi,
anyone tried PD.2450 in open baffle? I heard about PD.2150 OB but it has much lower Qts comparing to the bigger brother, so the bigger should cope pretty well...
Regards,
JW

 

[tinitus]

if you want to keep it to dipole topic, and attract more attention, we could put the word OB into your thread title ?

or maybe widen it a bit more to make room for other big woofers ?


moderation

 

[grimskullcrushe]

Yes, sure word OB can be added to the title. Thanks.
Generally I am focused on PD 21" or 24" woofers and maybe Eighteensound 21LW1400. Others I rather do not consider.

 

[63781]

It should work very well

There's nothing wrong with the Beyma 21PW1400Fe either....

 

[grimskullcrushe]

I wonder if two PD.2450 would be better for home-music use than eight 12" which I use now:
http://www.stx.pl/uploads/images/W.STX.12.2.150.8.F.S.MC.parametry.jpg
The problem now is to get a proper sound pressure while listening quite loud, these 12 inches' need to play with huge excursion which lead to noticeable distortion...

 

[63781]

Two 24" woofers is approx the same cone area as eight 12". You will gain nothing.

It is more effective to just increase the baffle size than go brute-force with cone area. Doubling the effective path length gives you 6 dB better efficiency and max SPL.

But anyhow... you need massive cone area if you want to play loud at low frequencies. Trust me - I have sixteen 21" in large H-baffles, and it's not sufficient at 20 Hz....

 

[grimskullcrushe]

StigErik, I know your system, it's one of my favourites! I am aware that Sd is similar however PD has larger Xmax and therefore it should pump larger volumes of air with lower distortion. I don't want to increase the size of my H-baffles since it will colour the sound. Maybe the solution is to utilize more H-baffles with same loudspeakers I have now? Advantage of these woofers is very low price which is however a result of a steel frame...

 

[63781]

Where is your XO point between the woofers and the rest ?

 

[grimskullcrushe]

Now I am driving 8 woofers from two Marantz amps, so there are two XO points: 120 Hz, and about 40 Hz.

 

[63781]

That's really low, so much larger baffles will not be a problem. The dipole peak and/or quarter wave resonance of the H-baffle will occur above XO even if you double the baffle size.

 

[zmyrna]

those 12" you have are low Fs but also a bit excursion limited.
on an H baffle, single 21" should be enough for home audio.
from a price vs cone area perspective, two stacked 18" per side is even better.

 

[63781]

I agree that a single 21" per side in a fairly large U-baffle is enough for music at moderate levels.

If SPL is a concern, building a U-baffle will increase the efficiency by almost 6 dB compared to an H-baffle.

 

[zmyrna]

some of the distortion you are hearing can be the resonance of the h frames you have.
before spending more $$$, why don't you try to improve what you have in hand?
- as a start, you can try stig's bicycle tire tube method under your h frames
- you can add a horizontal brace between side walls
- and add some mass (sand bag, concrete/marble slab etc.)
- you can also try magnet mounting or swinging the drivers if you are not too attached to your H frames

 

[63781]

A brace between the sides helps a lot, the same goes for a brace around the opening edge of the baffle on both front and rear. Here's how I did it on my baffles.

 

[tinitus]

FaitalPRO | LF Loudspeakers | 18HW1070

apart from being 18" it has identical specs

 

[zmyrna]

I went for Faital Pro 18FH500
slightly less xmax but also much lighter cone

 

[tinitus]

I went for Faital Pro 18FH500
slightly less xmax but also much lighter cone

yes, it was on my mind too
its got only one spider, giving it the lower Fs, depite the lighter cone 😉
not sure its still produced

edit...btw, is it good ?

 

[zmyrna]

I got a good deal on 18FH500 Nd.
For home use, 18FH510 Fe should be just as good (and cheaper).
510 has a stronger frame too.

 

[grimskullcrushe]

My H-bafles are on loudspeaker legs, so the "tire tube method" is impossible to use... Nevertheless these legs helped A LOT!
So, since I have what have, I start to convince myself to:
- increase the amount of these H-baffles with the same speakers I have
- dampen the steel frames of these woofers (with bitumen mat or/and duct seal, which I already tried in other system)
- make a brace between the sides (which I was also thinking of before)

I also think about adding some damping mass to these baffles but I did not figure how to do it acoustically good and WAF good (which BTW is really high 🙂 ).
And, since loudspeakers are steel frame, I think it is not good idea to make them baffleless (swinging or magnet mounting). Being attached to the magnet the diaphragm, with help of the upper suspension, would "move" the frame and even increase the distortions. What do you think?
BTW. Thanks for the help!

 

[zmyrna]

18" Faitals delivered today.
all i can say is they are very light for a 18" driver.
very well made though.
i will use them with a 12" Faital mid and B&G neo8s tweeter in a 3 way swinging nude dipole project.
sorry for the hijack grimskull...
i think it is time for you to order some grill cloth for WAF