Re: [Harp-L] H Dustcap

[MARK BURNESS <markwjburness@xxxxxxxxxxxxxx>]

Dan,

You are adding 2+2 and getting 5 somewhat.

Dustcaps are just one component/factor, you are overlooking SPL (efficiency), 
resonant frequency, frequency curves, live listening tests etc.

I play a 1/3W amp through a 4x8" cab loaded with bass speakers out of a Traynor 
cab...the wattage handling of the speakers is many, many magnitudes more than 
that the amp can produce (the amp produces hundredths of the W the speakers will 
handle)....there is no loss of articulation. You never match amp wattage to 
speaker wattage, because tube amps are rated at clean output and are often 
played beyond their clean W rating, speakers therefore are typically rated for a 
minimum of twice the tube amp wattage (often you will see speakers with a "tube 
& "SS" rating the SS rating being more than the tube rating for this reason). In 
the 50's they used low wattage speakers...because that's pretty well all they 
had available at a reasonable price, some amps were strangled by tiny output 
transformers so that they couldn't make a lot of bass, allowing the use of low 
rated speakers that would outlast the warranty period.

The 4x10" Fender Bassman did not use bass specific speakers.

Bass specific & PA speakers can work very well in some amp cabs used for harp, 
other times when overused, they can make the tone flat & overly dark (a guitar 
speaker may be designed to reproduce from 80Hz upwards to 6KHz or 7KHz, bass 
speakers more often cover the range of 50Hz to 3KHz-4KHz, this has a pronounced 
effect on high end/detail). It is better to think in terms of specific speaker 
models rather than focus on largely arbitrary features like dustcaps & 
"bass/guitar" designations. In a multispeaker array it is obviously possible & 
often desirable to mix speaker type for a more complex tone.

The size of the dust cap will also be relative to the size of the voice coil, a 
speaker with a 2" voice coil will obviously have a bigger dustcap than a speaker 
with a 1" voice coil. More efficient speakers use larger voice coils & have 
bigger dustcaps than less efficient speakers, irrespective of intended use.

Very efficient speakers with very large voice coils & magnets can be overkill, 
increasing feedback. Conversely, particularly innefficient speakers (for a given 
size & voice coil) offer no advantage in reducing feedback & will reduce the 
volume, kill the tone of your amp.

Speakers are always chosen by builders & designers principly for their tone...it 
doesn't matter what the manufacturer designed it for, if it sounds good, use it.


________________________________
From: David Brown <nonidesign@xxxxxxxxx>
To: Dan Hazen <bluesmandan76@xxxxxxxxx>
Cc: harp-l@xxxxxxxxxx
Sent: Thursday, 17 November, 2011 21:16:15
Subject: Re: [Harp-L] H Dustcap

I think you also have to check the ohm rating of the speakers you have in
the cab to match it to the particular output of the amp.




On Thu, Nov 17, 2011 at 10:49 AM, Dan Hazen <bluesmandan76@xxxxxxxxx> wrote:

> >From what I understand, and based on my correspondence with Weber reps,
> the
> H dustcap is simply a larger dustcap (not as big as those on bass speakers,
> but larger than typical guitar speakers) designed to reduce treble
> frequencies, thus reducing feedback.
>
> For comparison:
>
> My Sonny Jr has speakers with large dustcaps.
>
> I did a little experiment a few minutes ago... I took my Marshall Class 5,
> which is far too trebly to use for harmonica, and I plugged it into my 4x10
> bass cabinet. It did reduce feedback.
>
> My Harpgear 2 does not have a large dustcap, but it has a funny looking
> raised dustcap (like a button or a thick poker chip) and it appears to be
> doped all around the dustcap, I would guess to give the same
> treble-reducing effect. I plugged the Harpgear into the bass cab, too, and
> it didn't really help it much... but I can play the HG2 very loud without
> feedback... it did however thicken up the sound of the Harpgear, and give a
> whompier bottom end. (Is 'whompier' even a word?)
>
> And then there's my Peavey Pignose. I took the guts of a Pignose Hog 20 and
> stuck them in a Peavey combo (40 watt Express 112, I think), b/c the
> Peavey's power section had gone bad, and I hated the Pignose speaker.
> Worked really well. The Peavey speaker happens to have a huge dustcap,
> almost 4 inches.
>
> I would think that you could tame a particularly feedback prone amp by
> plugging it into a bass cabinet. The trick would be matching the wattage of
> the bass cab with that of the amp... bass cabs are usually rated very high,
> whereas harp amps are usually fairly low watt amps, and if the amp is too
> low for the speakers, then articulation and sensitivity will suffer... You
> probably don't want to plug a 5 watt amp into a 400 watt cabinet. HOWEVER,
> that inefficiency MIGHT be an added help against feedback.... I think. I
> don't have a billion cabs lying around where I could try every combination,
> but I think that's the way it would go.
>
> I'm actually surprised that more guys aren't doing this sort of thing,
> using harp/guitar heads with bass cabinets, as it really does give a great
> thick bottom end to your sound... and after all, the working standard for
> harp amps is the Bassman, which was, obviously, originally designed as a
> bass amplifier.
>