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Discussion Starter · #1 ·
Considering swapping my 172s in the front doors of a Porsche 911 (991 generation) for a pair of GS8ND2 with a view that they're easy to give some real power with a small class-D amp using dual 2ohm chans, and they might give me a few more hz low frequency extension in a car without a sub.

I'd be looking to run a pair off 4 channels in a Helix V Twelve

Value any first hand experience people may have. Inspiration is hearing a B&W McLaren system that employed a similar solution in OEM config.
 

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Considering swapping my 172s in the front doors of a Porsche 911 (991 generation) for a pair of GS8ND2 with a view that they're easy to give some real power with a small class-D amp using dual 2ohm chans, and they might give me a few more hz low frequency extension in a car without a sub.

I'd be looking to run a pair off 4 channels in a Helix V Twelve

Value any first hand experience people may have. Inspiration is hearing a B&W McLaren system that employed a similar solution in OEM config.
AS much as I'd love for you to buy a pair of GS8ND2, I think the performance is going to be so similar that you won't hear much of a difference if you can provide similar power. If the real issue is that your amp choice can't be bridged and you need the dual 2 ohm coils, then getting a little louder with that amplifier might be a reason to switch.
 

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Cheers for the honest reply Andy

Which model would you recommend for differential rear fill?
For differential rear fill, there isn't going to be a lot of info--any coaxial is sufficient.

FWIW, I don't suggest differential for the back. Send it regular stereo, adjust the level up so you hear the rear, then delay (something like 12-20mS) until the image is solidly in the front.
 

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For differential rear fill, there isn't going to be a lot of info--any coaxial is sufficient.

FWIW, I don't suggest differential for the back. Send it regular stereo, adjust the level up so you hear the rear, then delay (something like 12-20mS) until the image is solidly in the front.
Andy, what would you suggest as the bandpass for the stereo rear fill?
 

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No bandpass. No lower than 100Hz. So, 100Hz high pass only (or higher if the speaker is small).
Thanks. I generally land on a HPF @ ~160Hz, and my "go-to" for rear fill are the inexpensive little Pioneer TS-A878 3.5" coaxials (or whatever fits the location). They never play that loud so the 160Hz HP is never an issue. I will sometimes put a LPF on them...usually between 4-6kHz depending on their location/proximity/aiming to the listening position. In real/live venues with longish reflections the high-frequencies naturally roll off as the HF energy is dissipated and are much lower in amplitude.

Used your GB25 similarly in a previous setup (before the GS25 were available) simply for their easy fitment, though they were overkill for the task. Currently using your GS42 as rear fill in the GF's car and have presets with and without the delay & level for occasions with rear passengers, and they do well in either mode. 👍

Happy Holidays, everyone!
 

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Discussion Starter · #8 ·
Ok great info Andy, oh and thank you for your excellent tuning guides, was useful to have a solid workflow.

I'll install a small 2 channel amp for the 172 and reuse the existing channels for the rears.

Cheers
 

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For differential rear fill, there isn't going to be a lot of info--any coaxial is sufficient.

FWIW, I don't suggest differential for the back. Send it regular stereo, adjust the level up so you hear the rear, then delay (something like 12-20mS) until the image is solidly in the front.
Could you explain a bit why? Just preference or is there a more technical reason?
I'm just asking because there are many discussions on differential fill, bandpassing, etc. but a lot of that info is quite a few years old now.
 

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Could you explain a bit why? Just preference or is there a more technical reason?
I'm just asking because there are many discussions on differential fill, bandpassing, etc. but a lot of that info is quite a few years old now.
I like regular stereo in the back turned down and delayed better. It's isn't so "phasy" sounding and doesn't change the frequency response so much. Works the same on just about all music. I also don't think that bandpassing in the back is necessary.

but, it's the back. It really isn't all that critical. There isn't really a "correct" if you aren't using some piece of software designed to do a specific thing.
 

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Discussion Starter · #11 ·
Was in the back of my own car yesterday (pub lunch, girls drove back). While differential rear fill on low can add some ambience and it sounds just like speakers out of phase when you're in the back.
 

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I like regular stereo in the back turned down and delayed better. It's isn't so "phasy" sounding and doesn't change the frequency response so much. Works the same on just about all music. I also don't think that bandpassing in the back is necessary.

but, it's the back. It really isn't all that critical. There isn't really a "correct" if you aren't using some piece of software designed to do a specific thing.
If I am understanding your earlier post, you’re saying it’s not ideal for the rear door speakers in a car such as an SUV (Jeep Cherokee TH) to have them playing frequencies below 100hz?

And that having coaxials back there is all good? And would having the same size speakers in the rear doors as the front doors be not ideal, but having a size smaller than the front door speakers be ideal?


How to add delay to the rear speakers if using the factory HU wiring (Like if using a Kicker Key 200.4 bi-amped for the front stage that already has time delay)?

Is it possible to delay them 12-20ms without using a DSP?
 
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