[Hallicrafters] RE: Why is the R-42 speaker so expensive?

Sun Sep 30 16:09:32 EDT 2007

The Bass Reflex cabinet does not depend on sound absorbing material for what 
it does. It uses the aprox. 20% of the sound off the back of the speaker 
cone that is wasted, puts it in phase with the sound off the front of the 
speaker and in doing so adds an appreciable gain in the low midrange and 
bass response.

This is accomplished by using a cabinet constructed of a heavy hard wood 
that contains a fixed volume of air, said volume partly determined by the 
size of the speaker cone, and either a certain diameter circular front port 
that puts the cabinet air in phase with the air off the front of the cone or 
a tuneable cylendrical tube mounted in the front cabinet port hole that 
allows the user to manually tune the interior volume to cause equal sound 
phasing. The second method eliminates the need for a cabinet of a specific 
size.

The purpose of a Bass Reflex cabinet is to utilize the wasted sound off the 
back of the cone, not eliminate it by the use of sound absorbing material. 
If you do that, then you end up with an infinite baffle cabinet.

Take your pick; infinite baffle, ducted port or folded horn. They all have 
advantages and disadvantages. Your need determines which is best for you.

Duane Fischer, W8DBF/WPE8CXO
dfischer at usol.com
HHI: Halligan's Hallicrafters International
http://www.w9wze.net
HHRP: Historic Halligan Radio Project
hhrp.w9wze.net

----- Original Message ----- 
From: "jeremy-ca" <km1h at jeremy.mv.com>
To: <lrlayton at cox.net>; "Julian Bunn" <Julian.Bunn at caltech.edu>
Cc: <Hallicrafters at mailman.qth.net>
Sent: Sunday, September 30, 2007 4:45 PM
Subject: Re: [Hallicrafters] RE: Why is the R-42 speaker so expensive?

> Reading thru some bass reflex threads on a few audio forums it appears 
> that the type and quality of the sound absorber makes a big difference. I 
> think I will experiment with some acoustic foam which wasnt even a dream 
> back in 1945-46 when the R-42 came out.
>
> Carl
> KM1H
>
>
> ----- Original Message ----- 
> From: <lrlayton at cox.net>
> To: "Julian Bunn" <Julian.Bunn at caltech.edu>
> Cc: <Hallicrafters at mailman.qth.net>
> Sent: Sunday, September 30, 2007 3:03 PM
> Subject: Re: [Hallicrafters] RE: Why is the R-42 speaker so expensive?
>
>
>> Julian,
>>
>> The R-42 that I have is certainly no open box design, as it is entirely 
>> enclosed at the back. The driver is not really that big (8 inches). The 
>> metal box and back are lined with very thick felt and the grill at the 
>> bottom of the cabinet under the speaker forms a port that is open to the 
>> inside of the enclosure.  That would put it in the bass reflex category.
>>
>> Perhaps you are thinking of the R-46 which is open at the back and has a 
>> 10 inch driver. The R-46 cabinet, which is similar in looks from the 
>> front, is smaller and lighter than the R-42 and does not have near the 
>> amount of bass response.
>>
>> Les Layton
>> Las Vegas, NV
>>
>> ---- Julian Bunn <Julian.Bunn at caltech.edu> wrote:
>>> Yes Bob, you are absolutely correct about speakers in general, but I was
>>> not speaking in general, I was talking specifically about the R-42. The 
>>> R-42
>>> is essentially an open box design.
>>>
>>> Julian
>>>
>>> Bob Young wrote:
>>> > Cabinet design has a huge impact on the sound of a speaker. A bass
>>> > reflex cab is tuned somewhere at or above the resonant frequency of
>>> > the driver inside, they are much more efficient and have much better
>>> > bass response than an open back cab with the same driver. These cabs
>>> > take the back wave of the driver and put it in phase with the front
>>> > wave and release it through a port usually below the speaker in front
>>> > reinforcing the bass. Open back cabs cancel most of the lower bass
>>> > because the back and front waves are out of phase with each other,
>>> > ever listen to a driver that is not in a case, no bass at all due to
>>> > out of phase cancellation. The only draw back to a bass reflex speaker
>>> > is they drop off rapidly below the resonant frequency of the port.
>>> > Sealed speakers sound even better as their drop off is much more
>>> > gradual, but they are less efficient as they pretty much keep the back
>>> > wave right in the cab itself. Many different cab designs. I don't know
>>> > if this is anything to do with the price however.
>>> >
>>> > Bob
>>> > KB1OKL
>>> >
>>> > Message: 4
>>> > Date: Sat, 29 Sep 2007 18:42:17 -0700
>>> > From: Julian Bunn <Julian.Bunn at caltech.edu>
>>> > Subject: Re: [Hallicrafters] Why is the R-42 speaker so expensive?
>>> > To: jeremy-ca <km1h at jeremy.mv.com>
>>> > Cc: hallicrafters at mailman.qth.net
>>> > Message-ID: <46FEFEF9.4020302 at caltech.edu>
>>> > Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>>> >
>>> > I think the sound is good simply by virtue of the size of the driver.
>>> > The cabinet probably has
>>> > minimal or no effect on the acoustics, IMHO.
>>> >
>>> > No idea why they are so expensive ... I picked mine up very reasonably
>>> > from a chap who
>>> > was selling an SX71 and it came with it.
>>> >
>>> > Julian
>>> >
>>> >
>>> > ______________________________________________________________
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>>> > ----
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>>> >
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>> ______________________________________________________________
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>> dfischer at usol.com
>> ----
>> HHI Halligan's Hallicrafters International and www.w9wze.net
>>
>
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> dfischer at usol.com
> ----
> HHI Halligan's Hallicrafters International and www.w9wze.net
>
>
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