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Question about crossover design
Question about crossover design
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Old 29th July 2019, 12:32 PM   #1
johnnyk9 is offline johnnyk9  United States
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Default Question about crossover design

I have a question for someone smarter than myself(everyone) ; )
I have a few Dunlavy SC-1's and plenty replacement drivers for each.
I have recently purchased a few Scanspeak 25W/8565-00 10"drivers and have been considering building cabinets to house a 10" woofer above and below an SC-1 to make it similar to an SC IVa , Or as I already own a Dunlavy built HRCC crossover (driver matching aside) Build an HRCC center channel and I have enough Scanspeak 10" woofers left to build a pair of "pseudo" Dunlavy Alethas, They are similar to an SC-IVa
The difference is an Aletha has a single 10" woofer firing down and a SC-IVa has 2 10" woofers firing forward.
My general question is: would doubling my inductor value and cutting resistor values in half get me in the ballpark of using just 1 woofer instead of two?
I could possibly drive the woofers separately and do my crossovers on the input of the amp.

I know most people are sick of hearing about people attempting to clone Dunlavy speakers due to the fact that the drivers were heavily QC'ed then matched, hand tuned crossovers then again dialed in inside anechoic chamber, but I think I can atleast get close enough for ME.

Thank you for your time
Johnny
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Old 29th July 2019, 12:50 PM   #2
wesayso is offline wesayso  Netherlands
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This thread should really be moved to the Multi-Way part of the forum for more responses.
This part of the forum concentrates on single full range drivers or a combination with a full range (or wide band) driver and a sub (or a tweeter).
The Multi-Way forum is meant for a project like yours.

The crossovers in a genuine Dunlavy is indeed tailored to it's drivers, so it won't do much good to add different drivers and expect it to work. But it can be done, with some care, measurements and input from this forum. Would you be able/willing to take/make measurements? Key factor of the Dunlavy speakers are their first order crossovers, which usually is one of the hardest types to get right.
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Old 29th July 2019, 02:35 PM   #3
AllenB is offline AllenB  Australia
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Question about crossover design
Quote:
Originally Posted by johnnyk9 View Post
due to the fact that the drivers were heavily QC'ed then matched,
Not at all, I'm sure you could.

As you are talking about a lower crossover, you could make some concessions. Baffle effects are on the out. Response discrepancies can be greater. You could use a higher order crossover.
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Old 29th July 2019, 08:02 PM   #4
johnnyk9 is offline johnnyk9  United States
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As far as taking measurements I really don’t have the equipment to take anything meaningful.
Just at a thought exercise, Let’s say 2 of the same woofers in parallel requires 1 50mH inductor to give 6dB roll off at 70 Hz does that mean a single woofer to get same crossover point require a 100mH inductor? Electrically?
Yet acoustically the single woofer downfiring would acoustically would require some more tweaking.
I guess the easy way of thinking of it is making a 3 way a 2.5 way.
Thanks again.

If I knew how to move this thread to another location here I would do it.
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Old 30th July 2019, 06:18 AM   #5
AllenB is offline AllenB  Australia
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Question about crossover design
Quote:
Originally Posted by johnnyk9 View Post
2 of the same woofers in parallel requires 1 50mH inductor to give 6dB roll off at 70 Hz does that mean a single woofer to get same crossover point require a 100mH inductor?
Yes that is right, however the one woofer would be 6dB lower in level.
Quote:
I guess the easy way of thinking of it is making a 3 way a 2.5 way.
A 2.5 way is no different except for the nominal disbursement of the duties of each driver.

You mention 70Hz. Perhaps you are trying to avoid issues in the vocal range. You are also going down into the room controlled region. You could gain benefits without having to cross your main speakers, but the way to do this might be to follow the 'multi-sub' procedure, as long as you stay at lower frequencies.
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Old 31st May 2020, 07:50 PM   #6
johnnyk9 is offline johnnyk9  United States
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I apologize I changed phones and somehow lost this post.
I appreciate the help with this.
I have since started using REW and purchased a mic.
Hoping to build a test inclosure and will do some measurements.
Wow, the prices of big inductance is expensive.
I would go active but do not have electricity where I would need it.
Thanks again.
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Old 31st May 2020, 08:21 PM   #7
GordB is offline GordB  Canada
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johnny, what modelling software are you using?
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Old 1st June 2020, 10:18 AM   #8
system7 is offline system7  United Kingdom
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We had a Dunlavy circuit here recently in all its glory:

Click the image to open in full size.

I just wouldn't fancy that with this scan bass:
Scanspeak 25W/8565-00 Woofer - Classic Range

The original closed box Morel 10" looks much tidier if it's anything like this:
Morel MW-1075 10" Woofer

The Dunlavy SC1 looks quite easy if uses the famous old Vifa 5" polycone.
Dunlavy Audio Labs SC-I loudspeaker | Stereophile.com

That Scan bass needs a steep crossover, IMO. Maybe a notch too. I don't think John Dunlavy would have specified it for his style.

Better as a subwoofer, I'd think. And all that that entails.
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Old 2nd June 2020, 11:46 AM   #9
johnnyk9 is offline johnnyk9  United States
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Yes I remember JD saying in Stereophile that he has a tough time getting the scanspeak woofer to work in his design.
I have never used a modeling software. Can you suggest one to learn?
I have thought to just take the above schematic and just double the mH and cut all resistance in half and go from there, but man those big inductors are expensive!
Thanks again for the great replies.
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Old 2nd June 2020, 12:33 PM   #10
GordB is offline GordB  Canada
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Default I'm no expert

Quote:
Originally Posted by johnnyk9 View Post
Yes I remember JD saying in Stereophile that he has a tough time getting the scanspeak woofer to work in his design.
I have never used a modeling software. Can you suggest one to learn?
I have thought to just take the above schematic and just double the mH and cut all resistance in half and go from there, but man those big inductors are expensive!
Thanks again for the great replies.
Johnny, hang in there. Like I say, I'm no expert but I would suggest you not make a bunch of changes based on a hunch. I, and others here, are using Vituixcad 2. It's a bit of a slog at first but it is very fast, robust and produces usable design very quickly.

You should also learn how to use winisd - the 950 version - for cab design. There's a lot going on with speaker in cabinet impedance and it's interaction with your crossover and you need to have an impedance plot that is as close to accurate as you can get before you buy parts.

One other thing. I suggest you go to erse audio for your speaker building and crossover parts. They have high quality parts at very competitive prices and I was very happy with their service.

Well now I got two things, I guess. Scour the web and see if you can find a design using your drivers. All the heavy lifting would be done ahead of time and you can proceed to building your dream speaker.

Last edited by GordB; 2nd June 2020 at 12:37 PM. Reason: one more question
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