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Old 31st July 2014, 06:30 AM   #1
beanbag is offline beanbag  United States
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Default Little woofer tower for little panel?

Hello folks,

I am considering getting one of the ER Audio mini electrostat panels, or maybe some other small electrostat panel (if you can name one) for use as desktop speakers. These panels about about 18 inches tall, and I figure that instead of making them even taller by putting a woofer underneath, why not make a mini woofer tower on the side.

In this case, I might use a bunch of little 4" speakers and put them in a vertical array off to the side. I only need this to play down to 80 Hz, since I can cross over to a sub.

One idea was an open baffle, but I think I simply don't have any more room to the side. The speaker will already be up against the edges of my two LCD monitors, and I could probably only have the total speaker system be 12" wide or so. I don't know if it "counts" to have the electrostat panel or monitor be a "baffle" on one side. On the other side, I suppose I could have the baffle extending backwards? But in general it seems I don't have enough room to make baffles to support 80 Hz.

How about a sealed vs ported box? Front or rear port?

Or maybe just have one larger woofer after all, but where could be another space-saving place to put it, besides directly below the panel? (It would make the speaker overall too tall.

Thanks

Last edited by beanbag; 31st July 2014 at 07:11 AM.
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Old 31st July 2014, 07:09 AM   #2
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I've built two bass towers to complement my Acoustat panels. I use four Dayton Audio RS180-4 7" drivers in each tower. The Dayton drivers are pretty cheap considering the build quality and the low distortion (and they look great ). The towers use an U-shape and about 8x30x9" (WxHxD). They operate in the range 40-250 Hz and in this range they have enough max SPL for my living room which is about 180 ft2. Here are some pictures and measurements.

If you're going to XO to subs at 80 Hz and use at close range, two 7" drivers in each tower will give you more than enough SPL. The towers would then be about the same height as the mini panel. Going with a smaller woofer means you could make a slimmer tower but you will lose max SPL because of the lower effective driver area. I would then chose a driver with higher xmax like the Tang Band W6-1139SIF for example. Note that you might need a digital EQ like the miniDSP or similar to fix the frequency response of the open baffle (see measurements in my photo gallery above). So bi-amping and active XO is recommended.

A sealed box would give you higher max SPL of course, but also a different radiation pattern compared to the mini panel. The OB towers integrate beautifully with the panels as they have a similar radiation pattern in the XO region. The sealed boxes will also be much larger if you're using the same number of drivers. I wouldn't even consider a ported box if you XO to subs at 80 Hz. Linkwitz has lots of information about OB speakers, including an Excel sheet for calculating max SPL of an OB speaker.

Btw, I'm really interested to hear what you think of the mini panels as I've considered getting a pair myself.

Last edited by phazer99; 31st July 2014 at 07:38 AM.
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Old 31st July 2014, 10:04 AM   #3
Calvin is offline Calvin  Germany
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Hi,

OB woofers mate the better, the lower the Xover frequency.
Its not easy to achieve a decently flat amplitude response with OBs as they tend to exhibit a comb-filter response with rising frequencies.
I'd rather use the array of small drivers in CB, as this assures not only the highest prescision at lower frequencies but also the more compact casing.
As desktop speaker You probabely are quite restricted regarding depth and width of the casing.

jauu
Calvin
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Old 31st July 2014, 10:26 AM   #4
beanbag is offline beanbag  United States
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What's CB?
Narrower width is better.
In terms of depth, the speakers will be about 18" from the front face to the back wall.
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Old 31st July 2014, 08:24 PM   #5
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Probably CB is closed box = sealed box.

Sometimes (like today) on craigslist one sees old Janszen models that use square ESL sections. Perhaps those can be re-purposed?
Attached Images
File Type: jpg Janszen Z-412HP.jpg (15.8 KB, 245 views)
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Old 1st August 2014, 06:55 AM   #6
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Hi There !!

I used a 5.25" CB woofer for use with my 9.75" tall desktop DIY ESL and the two worked together seamlessly!!

I could not locate either driver in any of the material I had sampled on them, They just worked as a whole like there was only one driver.

The First FR chart shows the interaction of the two drivers as measured from my listening position as showed in the First picture.

The next 3 FR charts are more precision measurements I did with less room reflections and are calibrated in true SPL levels at a nominal 95db or so at 1 meter.

If I run this at a more normal lower level of 85db (nearfield at 2' to 3') then the bass response becomes much flatter and more extended.

This was about the maximum that I can get out of the one little woofer, and if I had maybe 3 or 4 of them it would suit this little panel quite nicely as it would do in excess of +105db all by itself.

At this level (95db) the woofer was at its Xmax mechanical limit for the lowest frequency's (40-60Hz) but it still sounded clear and non-distorted.

Kick drums and Bass guitars did sound amazing, very clean and punchy even though I thought that the cone was going to come lose and fly out at me!!!

I was measuring somewhere around 1cm of p-p excursion and maybe slightly more by a few mm or so on the very same tests that I made these FR charts.

FWIW

jer
Attached Images
File Type: jpg old esl.jpg (128.7 KB, 233 views)
File Type: jpg fr4.jpg (71.9 KB, 234 views)
File Type: jpg fr1.jpg (88.1 KB, 231 views)
File Type: jpg fr2.jpg (85.5 KB, 230 views)
File Type: jpg fr3.jpg (84.6 KB, 29 views)

Last edited by geraldfryjr; 1st August 2014 at 07:20 AM.
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Old 5th August 2014, 04:04 AM   #7
a.wayne is offline a.wayne  United States
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Gerald ,

That looks like something to give an x-wife ,electrocute much .




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Old 5th August 2014, 11:34 PM   #8
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Ahhhhh,ha,ha,ha,ha,ha,ha,ha!!!!!!

Ya, Well.........I did get nailed by a full 10Kv from my power supply off of that red wire on the top of the woofer box that day!!!!

That is the one feeding the diaphragm and I am quite lucky to be able to be typing this today!!!! He,he,he,he

I was reaching across the top to re-position it and I was busy watching the SPL meter and some how in that situation I manged to graze upon the open connection of the twisted wire ends!!!!

Any other time I can handle the panel without getting shocked, but I guess I missed the panel and caught the wire........Eeeeeeeeeouwie!!!





jer
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Old 6th August 2014, 07:58 AM   #9
Calvin is offline Calvin  Germany
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Hi,

reminds me of that 80s song text.... Hes fresh .... exited ... by Kool+TheGangStats
Nono, Im really happy that You only got zapped and not Babycued.

jauu
Calvin
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Old 6th August 2014, 09:55 AM   #10
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He,he,he.....Thanks Calvin !!

Not to go off topic but for those reading this, I have been zapped before from this supply.

But, Not at full output as it can deliver about 30 to 40 watts (input power) continuously at 13.6Kv and I didn't have a current limiting resistor hooked up!!

This is was a perfect example of why you should have one hand in your pocket when working with such voltages, and, I do this religiously and with reverence when working with such voltages.

Or else the fun stops!!!!

Voltages such as these come out of the step-up transformers too and I have been bitten by them as well!!

So this instance is not just pertaining to the just the Bias Supplies.

I did feel the charge go down the side of my body and not across my chest.......Thankfully!!

But that did knock me back a bit!!

FWIW

jer
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