Looking For Cab Designer Besides WinISD

[stetto]

Just been looking around...I've had a spare OEM Ampeg/Eminence 15" and a Celestion G10L-35 laying around and would love to build something more portable than my 50DL...WinISD won't calculate multiple driver enclosures and doesn't have the Thiele-Smalle data for the G10L...

Thanks
Eric

[Zaphod B]

Can you get the Theile-Small parameters from the manufacturer? If so, you can just do the math yourself.

[stetto]

Hmmm, good idea, that's what I had to do for the Eminence parameters...Got kinda political with them too, Eminence said they no longer made the the driver, Ampeg said "Sure they do, they just can't release that info on a subcontracted OEM"...So after going through a half dozen departments I found someone at Ampeg who was ecstatic to give me the goods...

Hopefully someone at Celestion has been around long enough to remember a 30 year old speaker...

Eric

[Zaphod B]

You know, from what I've seen of the various types of speaker cabinets over the years, it doesn't look like cabinet designers paid that much attention to the T-S parameters, anyway. I've known people to swap Celestions, Fanes, whatever, into and out of Marshall cabs with decent results in most cases.

Maybe the approach could be to ask what cabinets were using that Celestion 30 years ago, and try to derive some dimensions for the single driver that way.

[stetto]

Well, mine came out of an open-backed Marshall bass practice amp...I've talked to guitarists who've had them in 4x12 enclosures (sealed)...

...My main concern is the disparity in power-handling...The Eminence is rated at 150 watts, I'm assuming that the "35" in the G10L-35 is also a power-handling in watts...I'll have to build a crossover and likely keep the volume pot down...

Eric

[Fletch-X]

Is your OEM a 15729? If so you can get the data for it here http://www.ofgb.org/ Just download the Musicians reference file. Bruce Gavin gives good advice at another board I frequent and has compiled tons of info on drivers. There ought to be more folks like him. Hope this helps you!

Fletch

[stetto]

Hi Fletch!

Guess what---Mine IS a 15729, and I'm the guy who gave Bruce the numbers on it after getting them from Ampeg...Man, you're good, Bruce's database is EX-TENSIVE!!

And you reminded me to go look at it again to see if he's got my Celestion in there too!! Thanks Fletch!

Eric

[stetto]

Hot damn! And there it is....So I build a vented cab for the 15 with a sealed chamber in one corner for the 10...Excellent....

Eric

[stetto]

I spoke too soon--Tho Bruce has the driver listed, he has no data for it...

This, from the Celestion site;

Thiele-small parameters
Thiele Small parameters are useful for controlling the low frequency response of sealed or ported cabinet systems by changing the cabinet internal volume, and port dimensions. However they are of limited use when designing a guitar speaker cabinet.

• Electric guitar speakers do not reproduce 'low' frequencies (the low E string of a lead guitar has a fundamental of 82Hz) and so the frequencies at which Thiele Small parameters have significance are mostly below the operating range.
• Also, the parameters are measured at very small signal levels. Guitar speakers become non linear at very low levels compared to other types of speaker, greatly reducing the significance of Thiele Small parameters in actual speaker use. Using the Thiele Small parameters of a typical guitar speaker, you will find that halving or doubling the cabinet size makes minimal difference to the response.
• They have no relevance to open back cabinets.
• Care should be exercised designing ported (or reflex) cabinets for guitar speakers as the increased cone excursion below the tuning frequency can cause speaker damage.

The cabinet size, shape and construction are of far higher significance than the internal volume. Cabinet design using Thiele Small parameters ignores these most fundamental aspects. Important factors include the material you make the cabinet from, the panel sizes and shapes, how they are joined, how the cabinet is finished, the mounting of the speaker, etc. These, not Thiele Small parameters are the critical factors in the design and ultimately the sound of a guitar speaker cabinet.

Egad, man, haven't they heard the latest Stapp album? Subs are all the rage in guitar tone now, and has been for some years...

Eric

[stetto]

Found a decent resource here http://www.partsexpress.com/webpage....ID=27&wt.svl=1, a lot of home and auto stuff, but a faily comprehensive pro area...I see that Eminence has it's own cab design software...

Eric

[Zaphod B]

Originally Posted by stetto

Well, mine came out of an open-backed Marshall bass practice amp...I've talked to guitarists who've had them in 4x12 enclosures (sealed)...

...My main concern is the disparity in power-handling...The Eminence is rated at 150 watts, I'm assuming that the "35" in the G10L-35 is also a power-handling in watts...I'll have to build a crossover and likely keep the volume pot down...

Eric

...or run them both full-range, and build a resistive power divider network to keep the Celestion protected.

[stetto]

Originally Posted by Zaphod B

...or run them both full-range, and build a resistive power divider network to keep the Celestion protected.

Also an idea...My overwhelming ignorance on the subject (sure, I can build a cab to specs, but I'm not all that well educated on x-over wiring and such) tells me an L-Pad would be the trick on running full range, yes?

Yeah I can solder too, and can read the stripes on a ceramic resistor, just in case it might be that simple...

Eric

[Zaphod B]

Sure, an L-pad would work.

You can buy low-power L-pads at radio Shack, or more power-capable ones from any of the music supply houses.

Don't forget that by running two speakers together, that in itself is a power divider. (Four 30-watt speakers of the same impedance wired together in any configuration will yield a total power rating of 120W.) So your 30W speaker, combined with one other speaker of like impedance, would handle a power input of 60W.

[stetto]

Originally Posted by Zaphod B

Don't forget that by running two speakers together, that in itself is a power divider. (Four 30-watt speakers of the same impedance wired together in any configuration will yield a total power rating of 120W.) So your 30W speaker, combined with one other speaker of like impedance, would handle a power input of 60W.

Roger that, but I'm going to be coupling the 35W Celestion with a 150W Eminence--Yes, both the same impedance, but how would that disperse the power handling? I don't see the Celestion now handling 60 or 70 watts...Dammit, where is my pocket protector when I need it...

Eric

[Zaphod B]

You wire those two together, and the enclosure power rating will be 70W. The Eminence speaker will just be over-rated for the overall enclosure rating. That still might not be enough for the amp you're using, though.

I have a 2 X 12 enclosure with two 65-watt Celestions. I drive the cab with a 100-watt tube amp, and I have driven it hard at times. Never a whimper from the speakers.

[stetto]

Hmm, my amp of choice is an acoustic 370...Crazy with the low end, but still, this project is intended to create a more portable cab for small jams and rehearsals...My Ampeg 50DL works great with the acoustic, but is no fun to lug around...The thing about the acoustic tho, is that it really lets go with an 80 Hz POP! at startup...

My backup is a Behringer Bass VAmp Pro in a rack with a QSC RMX 850...

...I'm going to need to put another Celestion 10" in the equation, ain't I...?

Eric

[Zaphod B]

What is the output of that Acoustic 370?

[stetto]

Around 365 @ 2 Ohms. Obviously I'll be wiring for 8, so the output will be much less, maybe around 120 or so, but it is still ONE LOUD BASS RIG!...

Eric

[Zaphod B]

It's always a risk running an amp with a higher output rating than the cab, but if you are judicious with the volume knob you should be OK.

If you have two 8-ohm speakers, you can wire for either 4 ohms (parallel) or 16 ohms (serial). If you wire for 16 ohms you can keep the output of the amp down to where you won't have to worry about that Celestion too much.

Guitar speakers are pretty robust, anyway, and you won't kill the Celestion if you accidently overdrive it trying to find its limit. You will hear the voice coil bottoming out, and certainly long-term exposure to very high wattage levels will burn up the voice coil. Just be gentle!