8" woofer suggestions

[MunkeyQ]

Originally Posted by forr

I've got a Volt .pdf notice about it.

fs = 27 Hz
Qt = 0.24
Vas = 52 liters
Sd = 190 cm²
Xmax = +/- 5.25 m

You can find description here :

Volt Loudspeakers - About Us

Go to "Loudspeakers", then to "Studio", then to "B220.2"

About everybody speaking about Volt drivers is absolutely fan of them. However discussions about them are rare.
.

Thanks, but this isn't the B220.2 - it's the BM220.2, which is a completely different animal...looks very different too. The B prefix means it's optimised for bass usage below 1khz whereas the BM designates it as a bass/midrange driver.

I've been talking with someone who contacted Volt about a recone kit for the BM220.2 a couple years ago; they said to use the one for the BM220.8, so they must be very similar. Haven't got a reply from Volt yet though...

[The Space Egg Corp]

Originally Posted by MunkeyQ

EQ is needed on any constant directivity waveguide as the high frequencies are rolled off at about 3dB per octave (largely dependant on w/guide design though) about 2.5khz or so to maintain pattern control. It needs a lift to keep the response flat...the Econowave crossover does this with a passive low shelf filter, but it's better in many ways to do it with an active parametric EQ. That's what my Driverack's doing. There's a very good explanation of CD EQ on the Peavey site, but I can't seem to find it.

For example, here's my latest measurement of the CDX1-1745 on HPR122i waveguide, gated and smoothed with no EQ applied. Note how at 10k, it's 13dB down.


Still working on the EQ in LspCAD, haven't come up with anything truly satisfactory yet.

I use an Audix TR40 (cheapish mic) with an ART preamp and FuzzMeasure as a basic computer based RTA setup. The TR40 is reasonably flat from 800hz til 14khz, which is the region I mainly need it for. You pay more for a better mic which is flat from 10hz upwards...money I can't afford!

Some of the high end pro graphic EQs are very good, much more transparent than the majority of the consumer offerings. Rane, Ashly, Klark-Technik etc. all make some excellent EQs which can be had for about £200-300 used. Considering a Klark costs just over £1k new, it's not too bad. Rane's Constant Q series are especially nice IMO...much easier to cleanly cut a band. To be honest, the Behringer DCX sounds just as good as the DBX Driverack, don't be put off by the Berry namebadge on the front!

I'll consider doubling up the walls if there's enough wood. These seem to demand a well-damped cabinet!

Thanks again for the help. Your cabinet volume and port sizes would be rather helpful!

Hi again MQ

Yeah, that wall thickening did the biz on my TL's.
I dont even think it's about resonances of anything like that.
I think it really helps for a speaker with a V8 muscle driver like the Volt to simply have some weight behind it, not about resonance in my opinion.

People rattle on (no pun intended) about resonances, but have you ever tried hitting a lump of MDF with a hammer ? It's hardly the best material to make a glockenspiel out of !

I have an early 90's vintage Berry compresor here at Space Egg.
I paid £300 quid for the darn ting back den.
Fine piece of kit, I does exactly what it says on the tin.
Simply 'compresses' that's it, no character, no vintage special effects, just good solid compression up to pretty high ratios.
Hit the 'Auto' button if you can't be bothered to twiddle & 90% of the time works a dream.
Popped the hood on it one day to check it's pedigre, full of original DBX comp. chips etc. Basicaly a DBX clone.
LED's on it drive me nuts, as they bleed into the next door LED, just needs black paint around the LED's to shade them (Mmmm...must get round to doing that some time).

The Berry measurement mic is not a good recording mike, which makes me wonder about it.
I think if I had £300 quid to burn on a measurement mic I'd go for the bottom of the range Josephson, they make some real cool mics.

Still not sure about this constant directivity EQ.
My main concern is 'on-axis' real world listening.
Moving away from centre gives you mono anyhow, forget about what freq.
The less HF I have bouncing around at the sides the better IMO.
Not sure how it effects these JBL waveguides I have.

Have you seen the Karlson-Coupler waveguide 'tubes', very interesting.
Karlson worked with NASA on acoustics during the early space program.
A space age dude !

Cheers

Simon

[The Space Egg Corp]

Just found my mate Stanley, and we're checking out the precise cab. dims.
Full report to follow............................

[The Space Egg Corp]

Originally Posted by MunkeyQ

I'll consider doubling up the walls if there's enough wood. These seem to demand a well-damped cabinet!

Thanks again for the help. Your cabinet volume and port sizes would be rather helpful!

Hi MQ

Stanley and I just sorted out the cabinet dimensions for you.

507 x 342 x 267 external size

477 x 312 x 237 internal size

(yes made out of 15mm MDF, not 18mm as previously stated)

The 'front' is the 507 x 267 dimension

PORT - 220mm long, 2.5" internal diameter plastic drainpipe of some sort, epoxyed in place.

Port was mounted central, below woof & 20mm from inside cab wall, does not chug or wheeze.

BRACES - 3 internal braces along the 267mm dimension, each 15mm x 75mm

One brace on front between woof & tweet, 2 braces unevenly spaced on back, centred on diameter of Volt magnet.

Generous bitumen foam pad sandwiches on cabinet walls.

Cabinet stuffed generously with BAF etc. (totaly filled up, but not compressed).

These cabinet proportions 'work', you may have to re-proportion with that large waveguide.
Personaly I like the 1:1.6:2.5 ratios if pos, or at least 'uneven' for safety.
Some think this is rubbish, I hope they enjoy listening to the standing waves in their cabinets !

Cheers

Simon

[perempe20]

I'm planning to build a 2-way with good sensitivity for both music and movies. I want to use Vifa XT25 with a 8"/10" waveguide and a woofer (same size as the waveguide). Is this concept good? What woofer shall I use?

[The Space Egg Corp]

Originally Posted by MunkeyQ

Thanks, but this isn't the B220.2 - it's the BM220.2, which is a completely different animal...looks very different too. The B prefix means it's optimised for bass usage below 1khz whereas the BM designates it as a bass/midrange driver.

I've been talking with someone who contacted Volt about a recone kit for the BM220.2 a couple years ago; they said to use the one for the BM220.8, so they must be very similar. Haven't got a reply from Volt yet though...

Hi MQ

How's u doon wiv dem Volt's o yo's ?

Cheers

Simon

[The Space Egg Corp]

Originally Posted by MunkeyQ

Thanks, but this isn't the B220.2 - it's the BM220.2, which is a completely different animal...looks very different too. The B prefix means it's optimised for bass usage below 1khz whereas the BM designates it as a bass/midrange driver.

I've been talking with someone who contacted Volt about a recone kit for the BM220.2 a couple years ago; they said to use the one for the BM220.8, so they must be very similar. Haven't got a reply from Volt yet though...

Hi MQ

Progress ?

Simon