Suitable midrange cone, for bandpass mid in Unity horn. - Page 48 - diyAudio
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Old 26th January 2012, 09:40 PM   #471
keto is offline keto  Mexico
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This is a very cool thread.

There are a few interesting-looking mid drivers right now on ebay, including that discontinued Jamo one, a pair of Magnavox's with alnico magnets and an interesting looking Yamaha one.

The Fs=491 mid from Misco is available with no apparent minimum.

Assuming Sheldon's corner mounting, why not use a high-power 2" dome midrange? They seem to come with either Fs=800 (Hi-Vi) or Fs=400 (Morel).

http://gallery.AudioAsylum.com/cgi/u...&w=1056&h=1063

I have the original Danley/Lambdacoustics 300hz horn (w/BMS 4550), and am moving from the passive speaker-level filter to individual SET amps on each pass-band. I'll be doing some measurements soon, to see how to proceed. The mids will probably be a simple first-order band-pass. The tweeters' filter is sure to be interesting :-)

¡viva la unity/synergy! --keto

Last edited by keto; 26th January 2012 at 09:46 PM. Reason: image didn't work
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Old 27th January 2012, 05:11 PM   #472
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Quote:
Originally Posted by paulspencer View Post
<snip>
So, as a thought experiment, phase plugs

Click the image to open in full size.

Red Spade Audio: Synergy mid driver mounting and phase plugs

Do you see a problem here? We either eliminate the required bandpass chamber, or we try to add it back and end up with re-creating the problem we were trying to fix!

With a compression driver we are covering more than 4 octaves. With the Synergy mid, it's about 2.5. We don't need a phase plug and it removes one of the main features of the Synergy midrange!
Paul,

Work has been bananas for the past few weeks, and I haven't had a chance to upload any pix of my 'phase plugged' Unity.

The phase plugs I am using aren't remotely as small as what is in your illustration; in fact the phase plugs go about 2" into the horn.

Click the image to open in full size.
Picture something like this, but with the midrange throat located about 3" away from the apex of the horn.

The results I am getting are quite good. For instance, the high frequencies went so high that a couple times I had to double check and see if my compression driver was connected!

I wish I had some measurements; I haven't had time.

I wouldn't be surprised to find that the Pyle midranges are going to 4500hz, give or take half an octave. (with the phase plugs.)

Click the image to open in full size.
Click the image to open in full size.

I'm a bit tempted to try a midrange like the Dayton RS75. The RS75 has some interesting advantages in a design like mine. In my current configuration, I have a wooden phase plug suspended a fraction of an inch in front of the Pyle. With the RS75, I can eliminate the wooden phase plug, and simply use the solid aluminum phase plug that's built into the woofer.

Another advantage of the RS75 is that the aluminum phase plug reduces the surface area of the cone. So the RS75 is a 3" driver, but due to the phase plug, the surface area is closer to something like a 2" driver.

In a horn, the small surface area of the driver helps 'smooth' out the frequency response. (Since the horn mouth is undersized, the smaller the driver is, the smoother the horn response is, generally.)

In your post, you said that I'm "eliminating the bandpass chamber."

That's not true; I'm simply making it extraordinarily small. Plus, I'm still getting a 'notch' due to reflection off the throat.

I'm not saying that my solution is the best, just that I'm juggling things a bit differently. Danley sells designs that are high power and quite large. My designs are ultra-optimized for a tiny footprint. I've even considered using 1" woofers.

As I see it, the only price you pay with smaller drivers is a reduction in efficiency and power handling. And we have efficiency to burn, which makes micro drivers compelling. Plus, small drivers allow me to make the horn much smaller.

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Old 28th January 2012, 02:32 PM   #473
MSeddon is offline MSeddon  Australia
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Hi Patrick,
I wonder if you could use a sealed chamber like this one to easily close the back of one of these mid domes and make ourselves our own Synergy mid range driver.

Click the image to open in full size.
SEAS K2851 1.7 Liter Chamber for D75MX41, D7608/9200: Madisound Speaker Store

Madisound claim they are perfect for this 3" dome:
Click the image to open in full size.
ScanSpeak Discovery D7608/9200-10 3" Dome Midrange (D75MX41): Madisound Speaker Store

Maybe there is a similar product for the cheaper Daytons.

Cheers,
Mike
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Old 28th January 2012, 07:29 PM   #474
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Quote:
Originally Posted by Patrick Bateman View Post
My designs are ultra-optimized for a tiny footprint. I've even considered using 1" woofers.

As I see it, the only price you pay with smaller drivers is a reduction in efficiency and power handling. And we have efficiency to burn, which makes micro drivers compelling. Plus, small drivers allow me to make the horn much smaller.
Small horns have a high cutoff, 1" "woofers" would be working as sealed or ported below Fc, no "efficiency to burn" unless you use dozens per horn.

Pattern control to around 400 Hz or so requires a large horn, having pattern control that low is a desirable feature lost with a small horn.
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Old 6th February 2012, 04:01 AM   #475
keto is offline keto  Mexico
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Here are 1/3rd, 1/6th and 1/12th octave smoothed SPL response on the original Danley/Lambda Unity mids.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

Any suggestions for modding the horns, for a smoother response?

Thanks! --keto
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Old 6th February 2012, 08:04 AM   #476
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Quote:
Originally Posted by weltersys View Post
Small horns have a high cutoff, 1" "woofers" would be working as sealed or ported below Fc, no "efficiency to burn" unless you use dozens per horn.

Pattern control to around 400 Hz or so requires a large horn, having pattern control that low is a desirable feature lost with a small horn.
I should have noted, all of my ultra-small horns use boundaries to extend the curve. The ones I've made for the home are designed to be put in a corner, and the ones I've built for a car use the dash and/or windshield to extend two or three sides of the horn.
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Old 6th February 2012, 08:07 AM   #477
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Parts Express is selling some neodymium drivers from Pyle that look promising:

Click the image to open in full size.

The good:
- they're under $50
- they have an accordian surround, which tends to lower MMS and makes the front chamber on a Unity a bit easier

The bad:
- you'll have to seal off the back
- the driver diameter is too large to use with many compression drivers... this would be a good candidate for a Unity with a 1.5" throat

Here's the T/S, as measured by a forum member at diyma:

Vas Delta Mass completed: Wed Sep 08 21:13:01 2010
Drive level 100.000 % [ 3.271 mA]
;------------------------------------------------------------------
Re = 3.6804 ohms
Fs = 109.4246 Hz
Zmax = 39.8873 ohms
Qes = 0.5804
Qms = 5.7097
Qts = 0.5268
Le = 0.4773 mH (at 1 kHz)
Diam = 203.2000 mm ( 8.0000 in )
Sd =32429.2779 mm^2( 50.2655 in^2)
Vas = 14.8566 L ( 0.5247 ft^3)
BL = 9.6306 N/A
Mms = 21.2730 g
Cms = 99.4446 uM/N
Kms =10055.8535 N/M
Rms = 2.5616 R mechanical
Efficiency = 3.1514 %
Sensitivity= 97.0030 dB @1W/1m
Sensitivity= 100.3749 dB @2.83Vrms/1m
Krm = 15.969E-06 ohms Freq dependent resistance
Erm = 1.262E+00 Rem=Krm*(2*pi*f)^Erm
Kxm = 5.837E-03 Henries Freq dependent reactance
Exm = 734.591E-03 Xem=Kxm*(2*pi*f)^Exm
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Old 6th February 2012, 09:37 AM   #478
MSeddon is offline MSeddon  Australia
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Hi,
A couple of questions for any Synergy Akabak guru's out there:
1. I have noticed in many of the Synergy scripts out there that people have added a small rear chamber to the script to cater for the closed back drivers. e.g.:
Code:
Enclosure 'Mid Rear Chamber A' Node=60 Vb=1.8L Lb=5cm
I am wondering if these should be included in the scripts given that the drivers' T/S parameters have already been measured with the effects of the rear chamber present.

Do you think this needs to be in the script? I assume not.

2. Regarding the wiring of multiple drivers (parallel/series). In HornResp this is easy as you can specify the number of Parallel and Series drivers (for example the wiring of the 4 midrange is 2 groups connected in parallel both containing two drivers in series).

How do you do this in Akabak as it is important to be able to determine power handling?

Thanks,
Mike
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Old 6th February 2012, 04:39 PM   #479
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Hi Keto

Hey I found one of the old Lambda Unity horns in a pile of old stuff this weekend. We used the same wood parts back then but Nick filed his corners in with bondo (nice job too) but that made our version and his behave slightly differently. Since I base the crossovers on the measured responses, what I could help with, would not been much help with your horn.
As the horn you have is the one that Lambda supplied and I found one here, I can put a 4550 on the one I found and measure it and maybe help with a suggestion for a crossover.

Fwiw, the mid measurements look (to me) like they might be noise limited.
I don’t recognize the software off hand but I would suggest trying a couple things.
First, sequence based systems in spite of claims can be very susceptible to noise.
Noise intrusion can make sharp features like those between 100 and 200 Hz as well as sharp peaks in systems which cannot easily produce them (such as a system with an acoustic low pass filter). I would suggest a couple things;

Average a number of measurements until one can see a clean response to say -30dB down from the flat part on the low corner side.

A typical appearance for noise is to produce a deep notch below the low corner and then appears as free bass response. Do the measurement so that the mic to speaker distance is at least 1/3 of the distance to any reflection. Have the microphone far enough away from the speaker so that you are not in the mouth bubble (at least 3X to 5X the mouth size). What happens in front of a speaker is a little more complicated than assumed if one wants accurate measurements.
A view of that problem;
http://community.klipsch.com/forums/...alloonData.pdf

Lastly, some smoothing is desirable as ones ears have a “critical bandwidth” which is approximately 1/5 or 1/6 octave wide thus 1/6 or 1/10 octave smoothing shows more than what you can hear under the best case.
Best,
Tom
Fwiw Mike, we did use a sealed back cover like the one you show (but not having the cylindrical section) on our first Unity speakers in the way old days. That works just fine but soft domes are not usually a good bet because they are not a piston above some point (a damped traveling wave in the dome) while a hard dome would be fine (as long as it’s breakup is well above the acoustic low pass corner).
Good stuff guys, your letting what you measure point the direction.
Best,
Tom Danley
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Old 6th February 2012, 05:02 PM   #480
keto is offline keto  Mexico
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Hi Tom,

Thanks a million.

I'm using an Earthworks M30, Fuzz Measure and MOTU Traveler via Firewire to a MacBook Pro.

Before I go outside to do the new measurements, here's my first shot of the BMS 4550.

Click the image to open in full size.

--keto
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