Stromberg-Carlson 15" Coaxial

[thetubeguy1954]

I have a pair of vintage Stromberg-Carlson Slimline 15" Co-axial speakers. They are said to almost rival the Tannoy Reds. Can anyone here help me with suggestions for an enclosure? I have had most of the measurements already taken by my friend, so tell me what you need to know and I'll supply the required info. I've attached some photos to hopefully help.

[planet10]

Fs, Qts, Vas minimum.

Re, Bl, Qes would be helpful as well

dave

[thetubeguy1954]

Thanks for responding to my post. Forgive me for not answering sooner, but I couldn't find the paper with the measurements until now. Here's ALL the measurements I have:

fs = 24.56 hz
Vas = 16.3 ft
Qe = 0.693
Cms = 0.6594mm/N
no = 0.951%
Qt = 0.563
Re = 8.2 Ohms
Bl = 10.782T-m
Qm = 2.995
Mms = 63.684 g
SPLref = 91.8 dB


This is EVERY measurement that's on the paper given to after my friend tested the Stromberg-Carlsons. Please know that I know NOTHING about the significance of these measurements. Are they suitable for open baffle designs? If not perhaps you could suggest an enclosure?

I've attached a closer look at the "horn"?

[Nappylady]

WinISD recommends a sealed enclosure with an internal volume of 29 cubic feet. Yikes!

I'd try dipole first...

[planet10]

Qt = 0.563

This is high enuff to make it suitable for an open baffle -- and given the huge Vas, an open baffle is probably going to be the least intrusive "box" for it....

dave

[Vortex]

Inputting known data and calculating the rest which was needed (an ohmic resistance you could still measure I think) BassBox Pro came to the following values:

Mechanical Parameters

Fs: 24,56 Hz
Qms: 2,995
Vas: 16,3 cu.ft
Cms: 0,657 mm/N (or 0,115 in/lb)
Mms: 63,68 g (2,246 oz)
Rms: 3,295 kg/s (7,264 lb/s)
Xmax -> I entered a value of 5 mm (0,197 in) just myself, i think for a 15" fullrange Xmax could be around that...
Xmech (calculated from Xmax): 7,5 mm (0,295 in)
Dia, Sd, Vd all calculated by the program and as you can see, inaccurate (it's more like a 12" woofer, not a 15" one).
Dia: 299,3 mm (11,78 in)
Sd: 703,5 sq. cm (109 sq. in)
Vd: 0,352 liters (21,48 cu. in)

Electrical Parameters

Qes: 0,693
Re (calculated, please measure it, easy): 8,198 ohms
Le -> I don't have a freq. generator/counter so I couldn't measure it and cannot be calculated by the program
Z: 8 Ohms (I entered it manually, after looking at 8,198 Re), calculated it would be 9,838 Ohms
BL: 10,78 Tm
Pe: 100 watts (maximum electrical input power.. I don't think this fullrange would stand out more than 100W RMS or even less.. so I entered 100 Watts manually)


Electromechanical Parameters

Qts: 0,563
no: 0,951 %
1-W SPL: 91,8 db (calculted)
2.8-V SPL: 91,88 db (calculated)



Although some basic input parameters are missing from which good others could be calculated (like Le), I think, these parameters are not really correct, but anyway, useful for just to give you a basic idea of designing a box.

In a reflex box with one port, the SPL-curve is quite nice flat at an average of the flat region at about 112 db (wow!!??) ..

But I think, still more measurements would be needed in order to obtain really useful data.

Try to measure with a multimeter the Ohmic resistance of the speaker (simply measure the speaker's resistance at the two terminals) and if your friend can still help you, a quite accurate impedance curve wouldn't be bad OR try to measure Le some other way..

Then you could also get much more accurate results.


One more notice to the calculated values: if basic values are correct and ready, calculated values will be correct too, I think. As I was entered some basic parameters of the Thiele-Smalls of some quality speakers, I noticed that the calculated values were exactly the same what the manufacturer wrote in the datasheets.

Problems were only there, where the manufacturer was lying (cheating) at some values, like some 97 db speakers which came out finally (according to other parameters) to 91 db and so on.. but these were really bad drivers, we always designed a box according to factory parameters, but the result wasn't satisfying...

So this posting of me should only be a basic start point for you, nothing else.

[thetubeguy1954]

I do have the impedance curve that one of you asked for. My friend who did the measurements assures me they are quite accurate. He seemed impressed with the speakers. The man who sold the Stromberg-Carlsons to me told me that he owns the Tannoy RED, SILVER, BLACK, and various Stephens, Altecs & Jensen coaxials. In his opinion the Strombergs are only bettered by the Tannoy REDS overall. I plan on using these with my Mastersound Reference 845 amplifier. As I know ABSOLUTELY NOTHING about speaker measurements. May I ask what's the general opinion of them? Does this speaker "appear" to be of a high enough quality to be used with my highend SET? And does the person who said try dipole think they would work in something like the plexiglass dipole shown in another thread here?

Thanks everyone. Your help is VERY appreciated,

[planet10]

Originally posted by thetubeguy1954
May I ask what's the general opinion of them? Does this speaker "appear" to be of a high enough quality to be used with my highend SET? And does the person who said try dipole think they would work in something like the plexiglass dipole shown in another thread here?

The numbers don't really say anything about how the speaker will work with a SET (except that at about 92 dB, the 845s should have no problem driving them loudness wise). The flatness of the impedance curve will tell you much more.

Yes these would work in any of the clear baffles people have shown... the bigger it is the lower in the bass they will go... and there is not much that can keep up with an OB in terms of the box just getting out of the way of the speaker.

With the large Vas of the speaker, any reasonable conventional box, is going to be HUGE, so this presents a rare opportunity where the OB should be less obtrusive than anything else.

dave

PS: i've never seen or heard a set of these, but all comments i've seen have been very positive.

[thetubeguy1954]

I want to thank EVERYONE who responded. In case this matters I asked my friend and he says the tests were performed using the Liberty Audiosuite program and the test was a LAUD. The impedance curve is actually quite flat from 10 to 100Hz. It rises slowly from 8 ohms, starting at 12Hz until reaching a peak of Z=32.49 at (approx 22Hz) it then slowly goes back to the flat line impedance of 8 ohms reaching it at 35Hz and remaining there virtually flat out to 100Hz. I think I will try one of the plexiglass baffles. My initial plans call for 3'W X 5' H with the tweeter of the coax being at ear level when sitting on my couch. Do these measurements seem like a good starting point? Any suggestions?

[planet10]

Any suggestions?

Just don't put the driver dead centre

dave