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Old 17th October 2007, 02:58 PM   #1
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Default FR125 as top end in OB

I'm considering an OB MTM design using the CSS FR125 and a pair of soon to be released long throw 7" drivers. I'm looking at probably a simple 12" by 48" baffle.

My concern is that the behaviour of the FR125 on the open baffle will be significantly impacted by the two 7" drivers, particularly near the crossover frequency. Whereas a tweeter would be entirely sealed, the FR125 will (of course) have an open back. Even tweeters, I have heard, encounter anomalies with some OB applications.

To briefly explain why I am looking at this particular design...

1. I enjoy the very natural and open sonic characteristics of an OB design.
2. The 7" drivers should provide strong bass down to around 70 Hz on this baffle (may have to make it larger). They are, however, a little limited in their upper frequency response, which I don't mind if I can use the FR125's.
3. The FR125 has the upper and lower frequency extension I find necessary.
4. I want to keep the design very simple but with excellent results. Ideally, I would like to go with no higher than a 4th order LR xover (preferably 2nd order). Using the FR125 over such a wide bandwidth (400 Hz +) rather than a full 3 way design allows me to keep parts cost and xover complexity to a minimum, while meeting good performance targets. Choosing 400 Hz as the highpass frequency for the FR125 is also beneficial because it prevents the FR125 from running out of usable excursion at lower frequencies.

Thoughts?
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Old 17th October 2007, 06:37 PM   #2
badman is offline badman  United States
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I've been considering 'top range' drivers for my own open baffles for some time now. I'll be starting with Audax PR17OMO and Fostex FT17H, but for a full range, the more I think about it, the fostex ff85k is a near ideal midtweeter. Obviously beaming in the top octave, it also has the (strong magnet) rising response, nevertheless, it's well-behaved (I forget where I saw third party measurements, they looked BETTER, with less smoothing than the fostex curves)
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Old 17th October 2007, 06:57 PM   #3
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Default Re: FR125 as top end in OB

Quote:
Originally posted by DevilDriver
Thoughts?
I think it's a good idea.

7" woofers: Are you talking about the CSS version that replaces the Adire Extremis?
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Old 17th October 2007, 08:30 PM   #4
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Default Re: Re: FR125 as top end in OB

Quote:
Originally posted by Cal Weldon


I think it's a good idea.

7" woofers: Are you talking about the CSS version that replaces the Adire Extremis?

Yes, Bob and I discussed the upcoming SDX7 at good length last night. From the sound of it, it will be an improvement in many respects, but we'll see once I get them in my hands.

I'm glad I'm not totally off my rocker here. The other advantage, in my opinion, to this approach is that by using a single driver for upper midrange and all treble, it should be easier to avoid IMD and overlapping issues in some of the most critical frequencies in a loudspeaker (in my opinion).

There aren't many who seem to have had a go at this, so I suppose I will be the guinea pig as soon as the SDX7's come in.

If anyone else has some ideas on this, it would be appreciated. If not, I shall plug on and keep everyone posted.
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Old 17th October 2007, 08:43 PM   #5
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I think a few have done this and it seems to be getting more popular. If you feel you're not missing anything at the top, I say go for it.

I have something similar in my bedroom right now. Two Extremis in a Scottmoose designed box with a plate amp and planet10 modified Foster 10F3's for the rest. I am happy even with my old ears.
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Old 17th October 2007, 08:48 PM   #6
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If not satisifed with this route, I will eventually transition to something else on the top end...likely a ribbon for the upper two octaves. Still, I find the FR fairly satisfying and the advantages it presents in a system with a goal of stellar but simple performance are worth the shot, in my opinion.

Thanks for your responses, Cal.
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Old 6th November 2007, 06:19 PM   #7
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This seems like a pretty good idea to me - so much so, infact, that I was planning pretty much the same thing as a future project (the difference being that I was planning on current drive).

Crossing over as low as possible seem to me to be the best possible way to cover the audible range - that way one driver can cover the critical (human speech) range and the interference pattern between the two drivers is minimal (the acoustic center of the drivers can be close when compared to the wavelength at the crossover frequency). Coupled with the benefits of a dipole radiation pattern, this should be an interesting project.

Good luck - they should be something good.
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Old 7th November 2007, 01:53 AM   #8
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Below is the new look for the Apex II using the SDX7 woofers.We have had them for a few weeksnow but the land shipment will be coming in room.

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

In the Apex II is the new SDX7 woofer from CSS(more info on this driver in the coming weeks)

Here is a little taste of the over all look of the new driver.

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

For those who ever got a chance to listen to the Apex II with the old Extremis will be shocked at the out put of these new woofers.
They play lower,yes the Apex II dropped a few hz on the tuning. aa As well the drivers are a lot cleaner and a more detailed bottom end due to the cone one these new drivers.

Over all really happy with the new woofers, and they are just that woofers not midrange drivers but a woofer.

We did a HTFR using the FR125S up top of a sidefiring Extremis in a ported design last year.

But this new SDX7 woofer is far better than the Extremis.
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