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Old 24th August 2013, 09:54 PM   #1
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Exclamation Which is the best 7" mid/woofer around?

Hi,

I have built a 16 liter vented speaker using the Scanspeak 8545k and the 9300 tweeter. I have been struggling for years to get the crossover satisfactory, and now I have basically given up. I want to find a nice sounding mid/woofer without any need for crossofer wizardry. I am not the guy who designed the Wilson Watt5 or the Proac 2.5 (evidently). I'm just an average audio geezer who wants to make my speakers sound OK.

My question to you guys: Which 7" mid/woofer is the best around for a small vented box? Money is not an issue. :-)


The history is this... I worked with passive crossover back and forth and came up with a pretty nice and balanced design. I abandoned it, though, due to the harsch midrange. I have instead built my own active 24dB cossovers with state of the art op amps. My latest endeavour has been to build my own measurement microphone. SPL measurements look more or less OK (hard to judge due to room acoustics), but the speakers are still as harsch as ever. They only allow me to play soft acoustic music. If I put on a rock record I just want to go hang myself in one of my ripoff-over-prized-speaker-cables.

The 8545k has a 3-4dB bump around 500-1000 Hz which I have of course attenuated with different types of notch filters over the years. I have also, of course, compensated for the difference in driver sensitivity. Now that I have active crossovers, phase problems can be ruled out.

Well, there you have it... I want a new mid/woofer. Which one should I go for?
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Old 24th August 2013, 10:57 PM   #2
Jay1111 is offline Jay1111  United States
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What software are you using for crossover design? Anyway, this driver is hard to beat

SB Acoustics :: 6 1/2'' SATORI MW16P-8
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Old 24th August 2013, 11:43 PM   #3
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scanspeak 8531G
SB Satori
Tang Band W6-1721 (needs a larger box unless sealed)
Peerless nomex

Last edited by Bill poster; 24th August 2013 at 11:48 PM.
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Old 24th August 2013, 11:49 PM   #4
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Look for a driver (any driver) that is free of peaking in the 1~5 kHz region; these are very rare, but do exist. The measurements posted from the manufacturer are not to be trusted unless they were made on a IEC or larger flat baffle; you are not interested in replicating the diffraction patterns of the particular small box that was used to measure the speaker, but want to see the real response of the driver mounted on a flat plane.

Of course, your box will not be a flat plane, but it can use large-radii curved edges, at least on the left and right sides (2" or greater radii suggested). This not only simplifies the crossover design, but makes the driver sound better. (It's bad practice to try and solve a time-domain problem like diffraction with frequency-based equalization, as in the crossover.)

If your driver is flat and the box has low diffraction, you'll be surprised how little coloration the overall system has. You can preview the sound of the driver by listening to it full-range with no crossover at all; if it sounds bad, get rid of it, since even the most complex crossover can only disguise, but not eliminate, the inherent sonic character of the driver.

If listening to the driver full-range reveals a smooth, but slightly dull, sound, that's what you want. The tweeter is there to take care of sparkle. If the driver sounds harsh with no crossover, get rid of it, no matter how good it measures or how many rave reviews you've seen on the Internet.

My experience with notch filters is they are only advisable as a last resort. They can get rid of annoying and irritating peaks, true, but the resulting filtered sound can be dull and drab, with an odd absence of tonal color in the region that's being filtered-out. My guess is what's happening is that there's still a substantial increase in IM distortion in the region being filtered, and this is audible as a shift in tonal color in the filter region. By contrast, drivers that don't need extensive filtering usually have tonal colors are bright and vivid over the working range of the driver, and the crossover is simpler too.

Last edited by Lynn Olson; 25th August 2013 at 12:02 AM.
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Old 25th August 2013, 12:06 AM   #5
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Quote:
Originally Posted by karha096 View Post
"Now that I have active crossovers, phase problems can be ruled out."
*groan*

High order crossovers have phase shift, active or not.
Active crossovers are not a magic bullet.
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Old 25th August 2013, 12:38 AM   #6
ScottG is offline ScottG  United States
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Quote:
Originally Posted by karha096 View Post
..but the speakers are still as harsh as ever..

Well, there you have it... I want a new mid/woofer. Which one should I go for?
Avoid paper and hard materials and composites..

Look to a *good* poly woofer.

At the high-end (price) there are the Audio Technology drivers (poly with mineral-loading), which can be custom made to your needs. Also, there is the previously mentioned Tang Band W6-1721, and the at lower end the Peerless 830874.

Dynaudio, Morel, and Dynavox also produce poly woofers, but their Voice Coil diameter tends to be overly large which usually produces a cavity resonance with a "peak" in the treble response (..it's the 3" VC's you need to be wary of, 2" is usually OK).

Frankly the Tang Band sounds about right for your needs at a decent price. Of course any given driver might not be what you need with respect to your cabinet volume, so you'll need to do some modeling.

At a slightly larger size look to the Vifa 8" poly which is now re-branded as the ScanSpeak Classic P21WO20.



Remember that with a small baffle the response will need to be corrected, both for pressure-loss below the baffle's support region, and pressure gain near where it peaks due to multiple edge-sources of diffraction.

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Last edited by ScottG; 25th August 2013 at 12:52 AM.
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Old 25th August 2013, 01:34 AM   #7
ScottG is offline ScottG  United States
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Note: others like HiVi and Max Fidelity also makes poly woofers like Dynaudio.



Another driver to consider however is the Seas P18RNX/P
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Old 25th August 2013, 03:16 AM   #8
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How about a Hivi 6.8?
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Old 25th August 2013, 03:21 AM   #9
ScottG is offline ScottG  United States
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Originally Posted by rhubarb9999 View Post
How about a Hivi 6.8?
That's one of the 3" VC drivers based on the Dynaudio design..

You can see the resonance/peak in response near 3 kHz:

http://www.parts-express.com/pdf/297-444g.pdf


This one manages to push the resonance up higher and suppress it a bit more than usual:

http://www.parts-express.com/pedocs/...8ft-manual.pdf

Hopefully this newer model has better non-linear performance than older models..

http://www.parts-express.com/pe/show...number=297-101
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Last edited by ScottG; 25th August 2013 at 03:34 AM.
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Old 25th August 2013, 04:06 AM   #10
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I'm aware of only one 6-7" woofer that I'd use above 1khz, it's that one
The Madisound Speaker Store
Another option is to get a small mid driver and make a three way.
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