Burhoe Inspired Room Flooder

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karatestu
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Re: Burhoe Inspired Room Flooder

Unread post by karatestu »

Hi Steve,

I will be in a similar situation to you when i have built the final cabinets and moved them into my living room at home. Room is 12ft x 14ft and they will have to be at each side of a bay window. Not ideal but that is what i have to work with. Mine will have to go up against the wall as well :roll: but then i have read the doc saying cubes are best up to the wall because of the Allison effect. My speakers are different though with the main bass drivers being forward firing at floor level.

No going back to P&S i agree so i will do my best with the situation i have. At least we can pull them out for important listening sessions - you know the ones, when wife is out or away and beer & takeaway calls :guiness;

Stu
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SteveTheShadow
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Re: Burhoe Inspired Room Flooder

Unread post by SteveTheShadow »

Right!
Since building that "NVA Inside" amplifier with souped up power supply, I've had some great sounds in my room over the past week.
It got me asking a basic question about my room flooders: why are you persisting on using damping inside the cabinets?

Whilst visiting Hull with them a few weeks ago, myself and a speaker designing mate of mine, were trying to make our minds up as to what I had actually built, concerning the cabinet itself. Was it a transmission line or was it a horn? Up to that moment, I'd always thought I had built an expanding transmission line cabinet.

The conversation went something like this:

Transmission lines work on the progressive absorbtion of the rear radiation of a lousdpeaker cone and normally get narrower, the further away they get from the driver. You can have one that expands, or can you? Now a the horn gets wider, the further away from the driver it gets. Horns are not damped, transmission lines are, and need to be in order to work as they are supposed to.

Now my flooders get wider as they go towards the exit, which is blocked, except for a port that loads the driver, so are they horns? Not if the mouth is blocked. Yes but they expand like a horn does, so just because the mouth is blocked up, that doesn't make them "not" horns does it?
Well the driver is mounted half way along said horn, so they are quarter wave expanding resonators or something?
We went on for a while and eventually decided that a decision had to be made on what these bloody things actually are.

What a load of graph waving theoretical :Bllocks: I hear you say and feck all to do with music.

BUT..... deciding what I had got here was quite an important process, as to damp, or not to damp, depended on the outcome of the "transmission line or horn" question. We can all take the damping out of our boxes and steel line them, but transmission lines don't work like that; they need progressive damping, so in my case the distinction is important.

So....I decided to remove complexity and say that they are horns, but terminated by a port, because they expand towards the exit. Horns expand, transmission lines contract, simple as that, my lines expand, therefore horn...end of.

Transmission lines, you damp them, horns, you don't, so why do my cabinets have stuffing in them, now I've decided they are horns?

So let's go with the "they are some kind of horn" theory and un-damp the buggers then.

A quick session with screwdriver, remove the bass/mid unit and yank out the stuffing and......yep....they are definitely some kind of horn hybrid. Awesome! :dance:

What a difference! Combined with the "NVA Inside" amplifier, these flooders sing their little hearts out. Even more music, even less hi-fi

I love it when a question gets answered like this.

My Burhoe/Allison/Dunn/Steve/ omnis, are horn hybrids, not transmission line hybrids :dance:
Last edited by SteveTheShadow on Sat Mar 17, 2018 1:16 pm, edited 1 time in total.
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Re: Burhoe Inspired Room Flooder

Unread post by Dr Bunsen Honeydew »

The ONLY answer to any hi-fi question is music.

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Re: Burhoe Inspired Room Flooder

Unread post by SteveTheShadow »

Dr Bunsen Honeydew wrote: Sat Mar 17, 2018 1:14 pm The ONLY answer to any hi-fi question is music.
Aye, but it needed to be answered in my case. I have been labouring under the weight of a theory book and it took a bit of lateral thinking to sort out what was what.
In the end the theory book offered no answer, so was thrown out the window and a decision was made.

More music came out, so the decision to undamp was the right one.

That's my story and I'm sticking to it. ;)

You're right of course; music was the final arbiter in the end.
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Re: Burhoe Inspired Room Flooder

Unread post by Dr Bunsen Honeydew »

Throw the book away - play music, try different things and *believe the music*.

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Re: Burhoe Inspired Room Flooder

Unread post by SteveTheShadow »

Just took the tweeters down by half an ohm.

I had, over the couple of months I'd had these speakers, noticed a slight discontinuity between the bass/mid and tweeter; not enough to be a serious issue and only there on certain records. Taking the tweeter level down just a tad cured the glitch.

One really has to be careful when doing stuff like this, that it does not get overdone, as the danger is that you kill the space where the music operates. I think I have judged it about right as it has pulled the image right into focus. Before, there was a slight sense of the there being two drivers, ie, the treble unit was, for want of a better term, "aurally visible" when looked at. This usually means that your tweeter is too loud.

That has gone and as a consequence, the music is more "simply there" playing. Don't get me wrong, the fault was very subtle, but once noticed, it was identifiable.

Once the more obvious wrinkles have been ironed out, any new speaker design takes a lot of living with before the more subtle faults make themselves known. Anyway, I think I have managed to home in on the problem area and deal successfully with it.
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