Why would they do this??

[admin_exported]

K...just picked up a set of Castle Warwick speakers

From my old catalogue, it looks like these were the first version. So I hooked them up and they actually sound really nice...smooth and natural toned but I did notice a lack of bass output.

I have a set of original Clyde's and they put out more bass and they are in a smaller box!! Hmmmm...

Being the guy that I am, I pulled out the bass driver...what the?? The whole box is packed with foam layering!! Top to bottom!! I pulled out one piece only to find another grey ridged foam which I am assuming is a type of acoustical foam and then below that is another full piece of yellow foam!!

I removed all three pieces and there, screwed to the back of the box is the crossover which is what I expected...I was wanting to replace the caps and solder the wire directly anyway so at least I had a look LOL!!!

But why all the foam?? It's a front ported speaker...shouldn't one piece be enough?? Removing some should at least give me more bass correct??

Hope someone can explain

Thanks kindly!!!

 

[chebby]

Hopefully one of our speaker designer members (Rick from EB or AE Jim) or even Ketan from the WHF staff can answer this. (Ketan designs and builds his own.)

 

[Andrew Everard]

Not terribly likely you'll get an answer from Ketan at the moment, as he's probably just arriving at Heathrow on his way to Japan on an overnight flight...

But I do know some of Castle's speakers did use quite a lot of internal damping; removing too much of it may give more bass, but will also alter the tonal balance of the speakers and make them overly boomy.

 

[chebby]

An old (2001) comment on the Warwicks from another UK mag states...

"The Warwick 3 is warm and friendly sounding. Deep, if at times sluggish
bass and a fine sweet treble. Up against strong competition though."

The older Warwicks were described by Gramophone magazine in 1990...

"I first put the Warwicks Out on 460mm heavy stands in a favourite
listening position in my room, well over a metre from any walls. In this
placement the first and lasting impression was of a performance which
was decidedly bass light, with a declining response from the bright
treble down to the very acceptably delineated midrange followed by a
fairly rapid falling away of the fundamental lower tones"

This was addressed by placing them much nearer the wall and using the grilles to tame brightness.

So it seems the Warwicks varied quite a lot between 'generations' between deep/sluggish bass and bass that was rolled off too soon.

Which version do you have?

 

[Anonymous]

I have the first version...all it says is "Warwick" and according to my old pamphlet, they look the same as in there...the size matches too as these are abot 19" tall!!

As for the treble...not bright at all...very nice but the bass is defintely lacking which surprises me...my smaller Clyde's beat them in that deparment!!!

They were placed about 15" away from the wall too!!

Also, at lower volumes, they lost pretty much everything top and bottom...I was left with only the mids which also surprised me!!

 

[AEJim]

Well the use of wadding (or foam in this case) does vary from manufacturer to manufacturer and speaker to speaker so it's hard to say what is "right".

Usually if the cabinet is well constructed the wadding will serve the purpose of damping internal box reflections and tuning the bass to bass/mid output - the bass/mid region (around 100-500hz) is probably the most crucial area to get right on a speaker so if something is amiss you definitely notice it. In most cases you would use the minimum wadding possible, if you have to pack the speaker full then there is usually a fundamental flaw in the design which would be better altered with the crossover, driver magnet strength - or even a change in cabinet volume.

With that said it seems the use of foam on your particular speaker is rather heavy-handed, is there any chance that this foam was once stuck to the internal cabinet sides/top and has come loose over time (this is a fairly common way of controlling cabinet resonance/reflections)? Any sign of dried glue on it or the cabinet? It could be that the speaker was indeed designed this way of course, or even that somewhere in production somebody got a little overzealous!

As you've already taken the speaker apart there's nothing to stop you playing with the amount of foam inside and tuning it to your taste - make sure both speakers have the same amount! You don't have to go mad either - we tend to tune wadding (like rather fine cotton wool) in amounts as small as 5 grams, tearing off or adding small sheets nothing more than a few inches square until we get the right amount. As I said it's usually more of a fine-tuning method so wouldn't normally make huge differences to the sound, with a denser foam in the amounts you say you have it could well make a sizeable difference though.

 

[Anonymous]

Very interesting points you make there james, i,ve always wondered why speaker manufacturers go to the trouble of designing and building an enclosure then just before installing the drivers, they fill various areas of the cavity with foam, accoustic damping material. Why don,t they write a cad programme that profiles the exact computer generated, tried and tested dimensions inside a solid mdf cabinet that would do away with all the human guess-work, from one production line worker to the other, thus ensuring that each individual speaker is perfectly voiced to it,s partner.

Just a thought John

 

[AEJim]

johnnyjazz:
Very interesting points you make there james, i,ve always wondered why speaker manufacturers go to the trouble of designing and building an enclosure then just before installing the drivers, they fill various areas of the cavity with foam, accoustic damping material. Why don,t they write a cad programme that profiles the exact computer generated, tried and tested dimensions inside a solid mdf cabinet that would do away with all the human guess-work, from one production line worker to the other, thus ensuring that each individual speaker is perfectly voiced to it,s partner.

Just a thought John

It's a very valid argument you make John, and while I can't speak for other manufacturers, we are always trying to find ways to improve upon the structural design and minimize "random" elements. The wadding we put into speakers is all weighed and cut to specific sizes and our staff are trained to insert it in a set way - making sure the product we sell is as close as possible to the original reference samples.

We have had problems with wadding in the past - some may remember our original Aego-T sub being rather a weak link in the system (as pointed out by WHF in their review). When we got the review sample back it turned out that the correct amount of wadding had been put in, but rather than being rolled loosely and placed in the cavity so as to expand and fill the gap, it had in-fact been stapled tightly to the top of the cabinet! Of course much tightening of procedures followed, problem fixed and the system was re-submitted for review with a much more favourable outcome! I'm trying to make sure we don't rush product out for review so quickly in future - that Aego-T was from our initial PP Sample run and was sent because our Marketing Manager at the time was desperate to meet the Awards issue deadline, the PP run normally is where we do all our thorough testing and would have rectified this problem... Anyway, straying off topic somewhat!

The whole need for wadding is all part of the "mystery" of speaker design - there are so many elements that have an effect on the sound. You technically want an inert cabinet yet I remember some concrete ones from the mid-ninety's sounding dire, you want a flat frequency response but this inevitably creates a sound no-one actually likes etc... That said there is always innovation and progression going on with design and you constantly learn and develop new ways to deal with problems (despite the basics remaining the same - just like the combustion engine!). Some new speakers we've been working on use a compressed rubber layer in the MDF to control the cabinet resonance and internal pressure-loading baffles to fix some of the difficulties caused by internal reflections on a large motor bass driver... That speaker still needs wadding to fine-tune though! It's like a filter system for the bass rather than an active tone control.

 

[Anonymous]

Thanks for all the info...that was great!!!

But aside...there was no glue on any of the foam...they were just three sheets.

From what it looks like to me is that there should be a full sheet of yellow foam to go right across the whole back to cover up the crossover. Then below the mid brace, in front of the woofer and the bottom port, the half sheet of grey ridged acoustical foam should go.

I'm thinking the last sheet was the extra LOL!!! Might as well have put a foam plug in the port!! That's what it sounded like!!

My Cylde's only have one sheet of yellow foam running down the back of it's enclosure...hence the better bass sound I guess

Gonna give it a try!!!

Thanks everyone!!