Enclosure for high Qts driver

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hurdy_gurdyman

Enclosure for high Qts driver
« on: 27 Jan 2019, 03:47 am »
I have a pair of vintage 12 inch coaxial drivers with a Qts of about 1.2-1.4and fs of 60 Hz. I was using open baffles in my old home, where there was plenty of space to let them bloom. I recently moved to a much smaller place and the speakers no longer give a great image. I would like to know what kind of enclosures to investigate that might work with these drivers?  :scratch: I have room for moderately big enclosures, but can't even think about some the size of old Bozak Concert Grands.

Dave  :green:

FullRangeMan

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Re: Enclosure for high Qts driver
« Reply #1 on: 27 Jan 2019, 03:50 am »
Bass Reflex always will work, what is the min and max litrage for this driver?

hurdy_gurdyman

Re: Enclosure for high Qts driver
« Reply #2 on: 27 Jan 2019, 04:10 am »
Here are all the specs I found online:

EV LT-12
Fs= 60 Hz
Zmax= 26.155 ohms
Re= 5.830
Zdb3= 13.655
F1= 54.653 Hz
F2= 72.865 Hz
Qms= 7.717
Qes= 1.720
Qts= 1.407
Le= 0.1396 mH
Sd= 591.023 sq cm
Cms= 0.2736 mm/N
Mms= 0.02571 kg
BL= 5.732 Tm
n0= 1.63633%
Vas= 135.172 liters
SPL= 94.157 dBSPL 1W/1M

hurdy_gurdyman

Re: Enclosure for high Qts driver
« Reply #3 on: 27 Jan 2019, 04:16 am »
I was also wondering if these would be suitable for a TQWT. I built one of those years ago for the Pioneer BOFU fullrange driver and liked how well it performed with a cheap driver.

Dave :green:

JohnR

Re: Enclosure for high Qts driver
« Reply #4 on: 27 Jan 2019, 04:20 am »
No idea about the TQWT but this is 6 cuft sealed modeled in Unibox:




hurdy_gurdyman

Re: Enclosure for high Qts driver
« Reply #5 on: 27 Jan 2019, 04:30 am »
Thanks, John. I hadn't thought about a sealed box. 6 cubic feet is a good sized bax. I wonder if using a smaller box and adding a sub might not be a better solution for a smaller room. I'll have to ponder this a while. :scratch:

Dave :green:

Folsom

Re: Enclosure for high Qts driver
« Reply #6 on: 27 Jan 2019, 04:31 am »
Bass Reflex always will work, what is the min and max litrage for this driver?

I strongly disagree. With QTS that high an aperiodic vent is probably the best. You also don't want a high feedback amplifier. I'd probably stuff enclosure with lots of polyfill to try and damp it a little. I wouldn't worry about making the enclosure well braced, in fact slightly flexy walls might be better.

Don't expect a lot of bass. What model are these speakers? I recently ran into the same QTS area for a vintage speaker. It was in a ported box and sounded like butt. Put some rags into the tube to make it aperiodic and it sounded ok. Didn't have polyfill to check...

hurdy_gurdyman

Re: Enclosure for high Qts driver
« Reply #7 on: 27 Jan 2019, 04:39 am »
The speakers are Electro-Voice LT-12 coaxials. I have a soft spot for vintage EV speakers. Have a soft spot for vintage Altec, too, but have an EV sized budget.

I've never made an aperiodic enclosure before. It could be an interesting experiment. Is there a way to calculate the size of enclosure?

Dave :green:

Folsom

Re: Enclosure for high Qts driver
« Reply #8 on: 27 Jan 2019, 05:07 am »
Vent size is based on the box size. Find a sealed size that seems appealing, then add the "vents".

You can use these. But you can also make your own following about the same vent to cubic foot ratio. You can make the holes smaller, too.

You can cut strips of some fabrics, and wind them into a spiral, and insert them into holes. You want to make it so you can breath through it but it would take a long time to exhale. I guess you could buy one vent, see what it's like, then make your own, too.

hurdy_gurdyman

Re: Enclosure for high Qts driver
« Reply #9 on: 27 Jan 2019, 05:17 am »
What effect does the size of the box have? I wouldn't want to use one too small that would rob bass extension.

Dave

Folsom

Re: Enclosure for high Qts driver
« Reply #10 on: 27 Jan 2019, 05:46 am »
It's pretty much like what a sealed box has. Build for that size then do your magic.

JohnR

Re: Enclosure for high Qts driver
« Reply #11 on: 27 Jan 2019, 06:11 am »
The smaller the box, the bigger and higher the hump in the graph I posted before (for sealed). I think for this driver you will need a large box regardless. If it were me I'd probably try some strategies with the existing OBs like putting damping around/behind etc before going to the trouble of building a large box that may not work out.

pis99

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Re: Enclosure for high Qts driver
« Reply #12 on: 27 Jan 2019, 12:39 pm »
How about an Onken Enclosure design? I have this design with my 15" vintage coaxial drivers and couldn't be happier. The best thing is that you can stuff the vents to your liking. You can calculate the enclosure size from below link.

http://www.mh-audio.nl/onken_br.asp

What effect does the size of the box have? I wouldn't want to use one too small that would rob bass extension.

Dave

roscoe65

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Re: Enclosure for high Qts driver
« Reply #13 on: 27 Jan 2019, 01:25 pm »
Vent size is based on the box size. Find a sealed size that seems appealing, then add the "vents".

You can use these. But you can also make your own following about the same vent to cubic foot ratio. You can make the holes smaller, too.

You can cut strips of some fabrics, and wind them into a spiral, and insert them into holes. You want to make it so you can breath through it but it would take a long time to exhale. I guess you could buy one vent, see what it's like, then make your own, too.

I’m late to the party but I will add my agreement with Folsom.  I own a pair of 12” Goodmans Triaxiom alnico drivers that have a high Qts.  TNT Audio successfully put these in a BLH adapted from the Coral Beta 10.  However, the Goodmans factory recommended one of two enclosures:

1.  Vented (big ducted vent) enclosure of 10,200 cubic inches (about 6 cubic feet).
2.  Aperiodic enclosure of 7,800 cubit inches (4.5 cu ft).  This uses the Goodmans ARU (Auxiliary Resistance Unit - a 10” x 10” aperiodic vent).  This enclosure is reputed to have tremendous bass.

Coincidently, I also own a number of Altec 414A/C 12” drivers.  These (and the Goodmans) are among the best wide range drivers ever made.  I note that the ideal enclosure volume for the Goodmans (4.5 cu ft, aperiodic) is the same ideal volume for the Altec (4.5 cu ft, vented).  I could build one enclosure for both drivers and simply swap baffles and drivers.  I would also guess this enclosure wold also work with the EV drivers.

If it were me, I would build a 4.5 cubic foot enclosure.  I would start with a vented enclosure with two ducts tuned to 40hz.  I would then start stuffing the ports with resistive material until you get the tuning right.  You may ultimately end up completely stuffing the port ending up with a sealed enclosure.

You may not need a subwoofer(s) with this speaker, but will likely want one.  My Altecs only get to 50hz or so.  These wide-range, high-efficiency 12” drivers can do a lot but can’t do everything.  Used as direct radiators, they tend to be limited in bass.  I consider a “fast-sounding” (Rhythmik in my case) subwoofer or two eliminates the effort to get more bass from these drivers.

hurdy_gurdyman

Re: Enclosure for high Qts driver
« Reply #14 on: 27 Jan 2019, 03:07 pm »
Thanks everyone for the info. I may try putting batting or something behind my small OB's and see how it works before building a large box. I already have a decent sub system using an H-frame 15" driver. But it's large, too. I live in a mobile home with a 13' x 15' living room. Not much space for big speakers, but I do like the sound these drivers can make. I'll try taming the back wave of the OB's first.

Dave  :green:

FullRangeMan

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Re: Enclosure for high Qts driver
« Reply #15 on: 27 Jan 2019, 05:07 pm »
With a VAS 135L a BR enclosure will no be too big.
Aperiodic are suited to small enclosures simulate a big box that seems is the case.

Folsom

Re: Enclosure for high Qts driver
« Reply #16 on: 27 Jan 2019, 05:41 pm »
With a VAS 135L a BR enclosure will no be too big.
Aperiodic are suited to small enclosures simulate a big box that seems is the case.

I don't consider aperiodic to be a means of shrinking boxes, not in the least. And it has literally nothing to do with the fact they sound very different (and good). But I consider ported to be a way of needing to grow box size.

Aperiodic helps control Q, which is a big problem when you driver basically has no damping (high QTS) and you're trying to put in a box instead of a 4x8 sheet of plywood.

planet10

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Re: Enclosure for high Qts driver
« Reply #17 on: 27 Jan 2019, 08:00 pm »
When one has a driver of such high Qts he only suitable enclosures are OB (where the dipole effect reduces the effective Q, or an aperiodic box.

Any box with a hole in it that i smeant to enhance the bass is going in exactly the wrong direction.

The "damped hole” in an aperiodic box is intended to try to reduce the Q, reduce the bass hump as the driver rolls off. There are a number of approaches to an aperiodic box. In this case, i would suggest a box as large as possible and then start putting holes in the back (or as one diyer with 15” Audio Nirvana did, no back at all). The nature and placement of damping is critical. The big box should be heavily damped, and the holes in the back also damped (i most often use open cel foam for this).

dave

hurdy_gurdyman

Re: Enclosure for high Qts driver
« Reply #18 on: 27 Jan 2019, 08:45 pm »
When one has a driver of such high Qts he only suitable enclosures are OB (where the dipole effect reduces the effective Q, or an aperiodic box.

Any box with a hole in it that i smeant to enhance the bass is going in exactly the wrong direction.

The "damped hole” in an aperiodic box is intended to try to reduce the Q, reduce the bass hump as the driver rolls off. There are a number of approaches to an aperiodic box. In this case, i would suggest a box as large as possible and then start putting holes in the back (or as one diyer with 15” Audio Nirvana did, no back at all). The nature and placement of damping is critical. The big box should be heavily damped, and the holes in the back also damped (i most often use open cel foam for this).

dave
Dave,

Maybe a stuffed box with pegboard on the back? Is there a minimum box size requirement? A pair of 6 cu ft boxes in my little living room is going to be crowded.

I'm using OB now, but because my equipment cabinets are right behind the speakers, the sound stage suffers. I'm considering trying absorptive material stretched behind the drivers on the OB's. This could maybe minimize the rear wave and cause less disruption and let the sound stage open up more. OB-aperiotic. This is all a new area for me.  :scratch:

Dave :green:

planet10

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Re: Enclosure for high Qts driver
« Reply #19 on: 27 Jan 2019, 08:53 pm »
WAF is important. That is why i said “as large as possible”. Pegboard has the holes, but might have resonance issues.

Have a look for baffle… that has some good suggestions for a backless (or large percentage holes), box pushing hard towards aperiodic.

dave