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PostPosted: Sat Jun 16, 2018 12:13 pm 
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Joined: Tue Oct 20, 2015 4:22 pm
Posts: 92
Location: Waterloo, ON, CA
Does anyone have experience with running 2 fullrange drivers in parallel (or series), one in a sealed enclosure and one in an open baffle?
I searched the internet but could not find much info on this.
Could something like this allow for the openness of open baffle, and better low end of the sealed enclosure, while avoiding frequency cancellation.

My drivers are Philips/norelco 9762m and Philips ad1265, both of them are 12", and have similar specs:

9762m (from 1960s, similar to 5200m, Alnico magnet)
Freq response = 35 - 18,000 Hz
Fs = 40 Hz
Qms = 11.9
Qes = 1.2
Qts = 1.0
VC impedance = 7 Ohms
Max power = 20 watts
weight = 3.5 kg

ad1265 (from 1970s, smaller ceramic magnet)
Freq response = 35 - 18,000 Hz
Fs = 45 Hz
VC impedance = 8 Ohms
Max power = 20 watts
weight = 1.8 kg

I found the frequency response of the drivers, attached here.
(the 9762m is pretty linear between 2000 and 5000 Hz, and the ad1265 is linear between 6000 and 10,000 Hz)

I also attached a sketch of what I intend to do. Bottom driver would be sealed.
Which one do you think is better suited for the sealed enclosure?

Appreciate any input on this topic


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sketch.png
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ad1265.GIF
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9762.jpg
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PostPosted: Sun Jun 17, 2018 6:44 am 
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Location: Not Toronto, ON, CA
What I see is similar to a FAST approach... a full ranger over a sub. Its a common practice with some of the full range DIY guys. I use it with super big 18" open baffle woofers. The FAST using a box woofer is much much much easier to get under the WAF radar I would think too.

My biggest concern would be that there is no mention of a crossover. While multiple bass woofers is a good thing in my book, I don't think having multiple high frequency sources would be the best approach. There may be a loss of coherency and some cancellation etc. For this reason I wouldn't run full range on both drivers.

If it were me, I would pick the best full range driver, and use that OB and then cross the boxed woofer over where the OB woofer rolls off. If you use Tolvan Edge software to simulate your baffle, it should give you a rough idea where the bass will start to roll off. Its a natural function of OB speaker design. That is likely where you want that lower woofer to help out and take over. This allows the OB to play wide range with no crossover in the middle. If you like one driver over the other, one thing to consider is that you can always add a super tweeter (large drivers will beam @ high freq) later if you desire better sparkle. So if one had better midsbut needed some sparkle, it may be the choice for OB because you can add some highs, tweaking mids won't be so easy.

Is there a reason you want to run sealed below? Better bass extension will be had going bass reflex if not mistaken. Edit: I see your woofers have high QTS... my bad. (Good for OB tho)

I could be wrong in the proper way to approach it, but that is what I would do.

Do you have an active EQ or anything? Could make experimenting a little easier in finding a happy point to separate frequencies.

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PostPosted: Sun Jun 17, 2018 7:05 am 
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Location: Toronto, ON, CA
I agree that the driver with the better mids should be OB, but I'm not convinced a sealed box to provide the LF extension is the way to go. Most rock/pop likes visceral bass in the octave roughly 50~100Hz, so I would build a tuned box to fill that region and let the OB fill the bottom end. I would also put at least a choke on the bass driver.

Mort, when you had that setup with the H-frames and Dynacos it had one of most balanced bass repro I'd ever heard. Surprising because it bucks convention. Also puts the mids in the box, which is not what the OP is after, I presume.

I don't know...it's very hard to match a box to an OB, in my experience. Not much more I can add, I'm afraid.

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PostPosted: Sun Jun 17, 2018 8:45 am 
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Joined: Wed Oct 10, 2012 10:07 am
Posts: 246
Location: Repentigny, QC, CA
I do something similar.

Big volume boxes are twin-ported at rear (reflex) and use jbl 12 inch drivers. I employ a TDM active x-over (not in pic).
The f r Visaton drivers are run full range; Fostex s-tweeters in parallel above. Both in OB section of speakers.

Buddies here acknowledge that this set-up works!
My amplification has changed a bit since the image, but these diy speakers will remain.


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PostPosted: Sun Jun 17, 2018 11:47 am 
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Joined: Tue Oct 20, 2015 4:22 pm
Posts: 92
Location: Waterloo, ON, CA
Thanks for the ideas.
I did not mention any crossover because I was thinking that both drivers can be run fullrange. Based on the frequency response of each driver, they seem to complement each other well in the 2 to 10k frequency range, assuming that they are separated well enough such that the midrange frequencies of each driver do not cancel each other.
Reason I mentioned sealed enclosure is that there are designs online for each driver in a sealed enclosure giving good response down to 50 Hz or so. A ported enclosure is also possible.
natedog, are your 12" jbl woofers or fullrange?


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PostPosted: Sun Jun 17, 2018 11:59 am 
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Location: Repentigny, QC, CA
Those jbls are 'wide range', I would say. Go easily and well up to 1kHz.


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PostPosted: Mon Jun 25, 2018 2:55 pm 
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Location: Waterloo, ON, CA
It looks like a dedicated woofer with a fullrange driver is more common.

So I tested the philips ad1265 and the norelco 9762m simultaneously (they are both 8 ohm, so I assume power was distributed fairly evenly between the channels).
What I find:
- I like the soundstange and the vocals of the norelco
- the philips has a better frequency response overall (for example, drums/percussion on some songs are barely noticeable on the norelco)

Is there a simple way to equalize the frequency response on the norelco, so it's not missing important details in the song?


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