Burhoe Inspired Room Flooder

Dedicated to those large boxes at one end of the room
chris661
Shed dweller
Posts: 2556
Joined: Mon Feb 22, 2010 7:29 am
Location: Sheffield

#61 Re: Burhoe Inspired Room Flooder

Post by chris661 »

Hi Steve,

Unfortunate about the tweeters. Any chance of sending them off to be repaired?
For what it's worth, it might be worth trying a staggered crossover, where you use the cap to set the initial rolloff, and then add a larger-than-textbook inductor. That'd give you a crossover that's first order for a while, and then transitions to 2nd order further down, which will help with tweeter protection.

Hindsight's 20-20, though, eh?

Chris
User avatar
IslandPink
Amstrad Tower of Power
Posts: 10041
Joined: Tue May 29, 2007 7:01 pm
Location: Denbigh, N.Wales

#62 Re: Burhoe Inspired Room Flooder

Post by IslandPink »

Bad news - & ditto what Chris says re. 1st steepening to 2nd-order - works for me.
"Once you find out ... the Circumstances ; then you can go out"
User avatar
Scottmoose
Needs to get out more
Posts: 1802
Joined: Sat Sep 08, 2007 11:03 am
Contact:

#63 Re: Burhoe Inspired Room Flooder

Post by Scottmoose »

You already know my view Steve, but I've already received shedloads of personal abuse for it from certain parties. So the furthest I'll go is to say

a/ This is precisely why I've noted on many occasions my preference for low Q 2nd order filters (Bessel, Linkwitz or a variation thereof as Chris & Mark mention, all of which provide you with an initial near-1st order rolloff around the corner frequency but more electrical protection & reduced excursion in the stopband) with dome tweeters, especially those that do not use ferrofluid. And

b/ I'm very sorry you've been hit by this. Burning out tweeters = a pain in the bank account. I'll see if I've got any spare tweeters in my store; if I have, you're more than welcome to them gratis, but I have a feeling I sold my last pair a few months back.
'"That'll do," comes the cry of the perfectionist down the ages.' (James May The Reassembler)
Website www.wodendesign.com
Community sites www.frugal-horn.com & www.frugal-phile.com
Cressy Snr
Amstrad Tower of Power
Posts: 10552
Joined: Wed May 30, 2007 12:25 am
Location: South Yorks.

#64 Re: Burhoe Inspired Room Flooder

Post by Cressy Snr »

Yes chaps,
Never had the problem before, but there's always a first time.
The first time is the last time for me.

No worries about the tweeters Scott, but thanks for the offer. I've got another pair of SBs at our Ants place, so not a total disaster, but I wasn't going to put them in the flooders. It was asking for trouble. I've put a pair of cheapo cones in there instead; once bitten and all that.

The ten-incher project will have a steeper crossover.
Sgt. Baker started talkin’ with a Bullhorn in his hand.
simon
Thermionic Monk Status
Posts: 5600
Joined: Thu May 24, 2007 11:22 am
Location: People's Republic of South Yorkshire

#65 Re: Burhoe Inspired Room Flooder

Post by simon »

Bummer Steve. These things are sent to try, but it's made me think about my own tweeters filling in at the top. I probably roll them off high enough not to be a real issue, but it's certainly made me think.

So how would I size the cap and inductor? Size the cap as a simple first order, but how to size the L?

There's probably enough info in Scott's post to be able to work it out but is there a simple rule of thumb for dummies?
Cressy Snr
Amstrad Tower of Power
Posts: 10552
Joined: Wed May 30, 2007 12:25 am
Location: South Yorks.

#66 Re: Burhoe Inspired Room Flooder

Post by Cressy Snr »

simon wrote: Tue Mar 27, 2018 6:35 pm Bummer Steve. These things are sent to try, but it's made me think about my own tweeters filling in at the top. I probably roll them off high enough not to be a real issue, but it's certainly made me think.

So how would I size the cap and inductor? Size the cap as a simple first order, but how to size the L?

There's probably enough info in Scott's post to be able to work it out but is there a simple rule of thumb for dummies?
You can get something that will get you into the right ballpark here Simon:
https://www.diyaudioandvideo.com/Tables ... /2ndOrder/
Sgt. Baker started talkin’ with a Bullhorn in his hand.
simon
Thermionic Monk Status
Posts: 5600
Joined: Thu May 24, 2007 11:22 am
Location: People's Republic of South Yorkshire

#67 Re: Burhoe Inspired Room Flooder

Post by simon »

Thanks Steve. Isn't that a second order though? I can work that out, I'm just not sure how the C and L are sized to give the gentle C roll off followed by the steeper L second order type roll off.
Cressy Snr
Amstrad Tower of Power
Posts: 10552
Joined: Wed May 30, 2007 12:25 am
Location: South Yorks.

#68 Re: Burhoe Inspired Room Flooder

Post by Cressy Snr »

I've no idea about how much to oversize the L either.
Sgt. Baker started talkin’ with a Bullhorn in his hand.
chris661
Shed dweller
Posts: 2556
Joined: Mon Feb 22, 2010 7:29 am
Location: Sheffield

#69 Re: Burhoe Inspired Room Flooder

Post by chris661 »

Since it's just for a bit more attenuation of the out-of-band signals, I'd use the 2nd order crossover filter, and set the frequency for an octave below where your cap is starting to roll off.

It's not a textbook alignment, but I'd expect that to do fine.

If you did want some textbook numbers, Bessel crossovers roll off very gently at first, so you could use an online calculator for those.

Either way, with the steeper crossover in place, I'd expect some midrange "hash" to reduce/disappear as the tweeter is having a much easier life at higher levels.


Usual terms and conditions - the online calculators are expecting a perfect 8ohm resistor, and your tweeter might be anything but. How the crossover integrates with the acoustic response is something else again.
If you'd like to play around a little, XSim is free software that lets you draw up crossovers and see the final response, as well as the slope for each driver. There's the option to input your own measurements for each drive unit, too.

Chris
simon
Thermionic Monk Status
Posts: 5600
Joined: Thu May 24, 2007 11:22 am
Location: People's Republic of South Yorkshire

#70 Re: Burhoe Inspired Room Flooder

Post by simon »

Thanks Chris, that makes sense. I'll have a look at XSim too.
Post Reply