Stradivari v/s OB

[navin]

I have been wondering about a new speaker system. The short list was:

1. Full range floor stander: 95db at 50Hz and response to 35hz.
2. Driver budget: $1500
3. high WAF
4. Room is about 280 sq. ft. (27m2) with a 9ft (2.8m) ceiling.

Looking at this backwards I first decided to tackle WAF. One idea was to build a OB or a Strad clone so that the speaker could be pushed against the wall when NOT is use.

Next I drew u[ a list of max dimensions:
Height: 46"
Width: 20"
Depth: 7"

The material used to build this speaker will be 18mm MDF coated with 3-4mm of resin bonded fiberglass on the inside. The FRP makes the MDF panel very stiff.

If this was used to build a box a la Strad, this technique would make for a stiff cabinet (as stiff as 30mm MDF but lighter than 25mm MDF), is easy to build, and the fiberglass seals all holes making the cabinet.

Initially I was thinking purely OB (see Please recommend a 15" woofer for a dipole) untill I stumbled across the Poor Man's Strad here http://www.troelsgravesen.dk/PMS-EXCEL.htm. I also read Troels's Dipole Study on the same webiste. Then I saw that Troels was working on something more interesting. What he calls a CNO here http://www.troelsgravesen.dk/CNO.htm

Now I figured I would replace the W22 in the PMS strad with 2 W18NX woofers and the W15 with the M15 and since I happen to have a pair of Scan Speak revelator tweeters (9900) lying around I could build a a clone of the PMS instead of m OB.

Both speakers would have simialr dimensions.

The OB would have 2 Augie 15", 1 Supravox 165-64 or Visaton B200, and 1 ribbon tweeter (Aurum Cantus or Fountek or similar).

The PMS clone would ahve 2 7" Seas woofers, 1 5" Seas mid (not the woofer), and the 2905-9900.

What would be pros and consof each design?

the other reason (other than WAF) for this project was that after living with bass reflex (JBL 2245l) and Sealed box systems (Audio Concpets DV12) I am gettign tired of the BOOM mostly from room resonance. If I placed either of my earlier speakers to reduce BOOM they'd sit in the almost the middle of the room.

[navin]

150+ views and still no reply...I guess my question was not very clear.

I am planning to build a new speaker that has better WAF than my exisiting pair (sealed box of 130 liters for each sub + MTM using ScanSpeak 18W8546 and 9900).

To make the speakers less obtrusive I was thinking of a thin dipole that could be pushed against the wall and stored there when not in use (since I only listen to music on weekends).

For this dipole I had shortlisted using 2 15" Augies woofers, 1 6-8" midrange (supravox 165-64 and Visaton B200 being 2 contenders) and a ribbon tweeter (a la Fountek 3.0 or Aurum Cantus G2si) mounted on a 20" wide baffle (with a 6" "wing" or "lip") that was about 46" tall.

Then I came across the Stradivari clone (link in post above) and figured that such a speaker would have the same dimensions as the Dipole (46"x20"x7). Using 2 7" woofers instead of the 9" woofer used would allow me to use the woofers higher and use a 5" midrnage instead of the 5" mid-woofer used. Using a midrange instead of a midbass would allow me to cross the tweeter higher and with a lower order crossover.

Since I have a pair of Scan Speak 2905-9900 free I could use them instead of teh SEAS tweeter or could use the SEAS tweeter without Ferro Fluid.

Q1: Has anyone built the Stradivari clone here http://www.troelsgravesen.dk/PMS-EXCEL.htm ?

Q2: Does this design come close to a dipole in sound? Some people claim this.

The Strad clone would use a smaller midrange (5") which should have better dispersion than the widerange intended to be used in the OB desgin. Is this assumption correct?

Building the OB requires less woodworkig skill but if the design fails the drivers are usless for anything else. If the Strad clone fails I can use the design in a conventional box (typical tower speaker).

[cuibono]

hmmmm, I was wondering about the exact same comparison. I guess not too many people have built the Poor Mans Strads...

Sorry I can't be of help. But I have decided to build an OB over the PMS.

[ttan98]

Navin,

If I am not mistaken you were looking at Hawthorn speakers at one stage, what happen? Change your mind?

[navin]

Originally posted by ttan98

If I am not mistaken you were looking at Hawthorn speakers at one stage, what happen? Change your mind?

Just part of my research. My object is to reduce the bass boom in my room and yet have bass.

From what I have understood OB's stand the best chance to reduce bass boom. I am been very interested in Darrell and Diana's work with the Sterling Silver Iris 15" Coax and Augies.

That would be my reference for now (even though that means pushing my driver budget to about $2000; i save due lack of cabinetry). I was just wondering if the Strad's could match the OB in lack of boom. The OB's need a lot more room behind (than the Strad) them to work.

So I was thinking instead of one 22cm woofer using 2 x W18NX001 for bass; some 40-45 liter liter cabinets and the M15CH002 for mid mated to either a SEAS or Scanspeak tweeter.

My speaker's width has to be equal too or less than 20" and depth equal to or less than 6" (ok I might be able to sneak it to 7") and height should be less than 46" (44" would be better). They will flank a wall hung LCD TV. The advantage the PMS/Strad design has over the OB is that even when stacked against the wall it will still operate fairly well (the OB's back wave would mean tht it has to be pulled about 2 feet out when in operation).

I have not really changed my mind. But I have not made it up yet.

Amplification also is another area of contention. I am building (rather slowly) a pair of EL34 PP amps. Each amp is in reality a stereo amp but using a design made by another diyaudio member (Wayne) found here
http://www.diyaudio.com/forums/attac...amp=1136905599
http://www.diyaudio.com/forums/attac...amp=1100080737
EL34 schematic confusion

I could use these to drive the bass and mid/tweeter sections of the PMS or use them to drive the Hawthorne coax (one channel for the mid and one for the radian tweeter) and press an old 200W Carver amp to drive the Hawthorne Augies.

[ttan98]

OB and box speakers have very different sound I am sure you know that.

If you have space go for OB and less space then go for box.

I am building both and experiment with the their sound quality, the budget for OB can be very low, look at the system from Martin King costs about $400, I am fairly confident the sound will be good to very good. You don't have to spend $2000.

cheers.

[augerpro]

You mention a reason for doing this is to get better bass, not just a BOOM. Have considered analyzing your room with say, ARTA, to find out if you have a particularly bad room mode and then eq it out?

[navin]

Originally posted by ttan98
I am building both and experiment with the their sound quality, the budget for OB can be very low, look at the system from Martin King costs about $400, I am fairly confident the sound will be good to very good. You don't have to spend $2000.

You are right

1. the number of drivers I can improt without them being considered "commercial quantities" is limited so I try to find good drivers

2. time invested should produce good returns hence I stick to time-tested systems with just a little room for experimentation.

Originally posted by augerpro
You mention a reason for doing this is to get better bass, not just a BOOM. Have considered analyzing your room with say, ARTA, to find out if you have a particularly bad room mode and then eq it out?

Yes. I did. the room is very square (16.5 x 16 x 9.25) and hence the nodes are severe. I am trying to use the shrotest possible signal path and trying to use natural cancellations instead of parametric equallisers.