Help me select new drivers for an Ampeg V4 cab!

Glad to help if I can.

It's important to know the internal volume of the cabinet to match the driver to the cab. What volume did you use, and did you measure it directly or find that spec listed somewhere?

Also can you list just for the record:

stock speaker make and model
number of speakers

I'd assume it's got 4 Eminence speakers but I could be wrong.

Is this a really old sealed 4x12 cabinet?

I think they either came with 25 watt CTS 12s or Altecs (depending on how you ordered it).

Back in the '70s Ampeg made a big (really big) ported 4x12 called the V2. I think I modeled one of those with Delta 12LFs and it looked good (IIRC).

Hookus said:

Yep, old sealed V-4. Outside dimensions are 27x30x14. Don't know what is inside, never took a speaker out.

Click to expand...

I remembered that a few years ago, a similar subject came up on The Bottom Line (although the OP was looking for a 2x12 to match an Ampeg V-4 head). Here's a report on the outcome:

"Subject: Ampeg dream realized (long gear post)

A couple weeks ago I came to TBL dreaming out loud about assembling a cab to match my old Ampeg V-4B head, which I "unretired" for a weekly blues jam we're now hosting; a "Mini-SVT" using 2-12's. Something smaller than the old V-4 bass cabs, which were a true roadie's nightmare in their day. I got some good suggestions from you, and thanks in particular to help from fellow TBL'er Bill B***, it was much easier to realize than I expected.

Bill suggested that there might be some "unloved" V-4 guitar cabs living in obscurity, having passed out of fashion, and he even sent a link to a picture of just the thing I had in mind. It's sized similar to the smaller 2X15 cabs some of us grew up with.He suggested that w/some rebaffling it might work well for bass. This one in particular had been on E-Bay at $199 to start and got nary a bid. When I contacted the seller he was eager to
move it out at a very reasonable priceand happy to keep the '76 CTS 30 watt guitar speakers it was loaded with, considering them the better end of the deal.W/out the speakers it was not as much of a beast to ship and was on my porch within a week. It turns out that '76 is also the vintage of my amp, so not only do they look like litter mates, but they even look a bit like
they've been through hard-knock school together. And like other '70's Ampeg gear, it's built like a tank w/heavy birch plywood.

Bill also recommended Eminence Delta LF's as drivers, and steered me to Avatar Cabinets. The 12" Deltas are very rugged and their response fairly flat from about 45 Hz to about 3k, w/a nice little peak at 3k, which works for me. Avatar's price was great and their responsiveness excellent.

As Bill had suggested, I worked w/a number of the free speaker cabinet design tools on the web to decide whether and how to port the cabinet. It was a bit of a crash course for me, but w/lucky results. It turns out that theinternal volume of V-4 enclosure is large enough accommodate the Delta LF driver specs in a sealed cabinet w/a -3db frequency of right around 58 Hz. Given the gradual low end roll-off of a sealed enclosure below that, it seemed worth a try for starters, rather than various porting schemes, all of which seemed to involve one trade-off or another. in order to achieve low end from smaller boxes.So I installed the drivers in the 10 o'clock and 4 o'clock holes, and covered the 2 o'clock and 8 o'clock holes w/some
1/4" lexan countersunk and screwed in place; no baffle mods at all.

I was a little worried about adequate volume and low end w/the
sealed box, but was pleasantly surprised with the results. The box is even and punchy right down to low-B, very clean in fact, and tremendously powerful. A/B'd with my Eden 210 XLT, the house shook noticeably more at the same amp volume. It's a beast! Which of course is it's downside, too. W/68 lbs. of cabinet and 26 lbs. of speakers, it's definitely not a "compact" (nor is the V-4 head, for that matter). Put in perspective,
though, it's about the size and weight of a heavy-duty 4X10, and I think it probably covers most of the same sonic territory. Without a crossover and tweeter it's probably better for blues than for tap-n-clankin', though there's plenty of room left over for such devices if one wanted to get creative w/design. All in all, a very fun and effective "vintage" cabinet for right around $300 plus just a little sweat equity."

From this, it seems that the V4 is too small for four 12s (and the Delta 12LFs are specially designed for small cabinets) but works well with two.

Drivers : (4) EMINENCE DELTA 12 LF

Vas : 3.132
Qts : 0.53
Fs : 41.77
SPL : 98.00


Box type : Closed
Box size : 5.3 ft^3 volume
Outside dimensions: 27"x30"x14"

SPL assumes total power @ 400w
.............Relative......................
Freq..........Gain.........SPL
[Hz]..........[dB]........[dB]
30.00......-15.53......114.51
35.00......-12.70......117.34
40.00......-10.23......119.81
45.00......-8.07........121.97
50.00......-6.19........123.85
55.00......-4.55........125.49
60.00......-3.17........126.87
65.00......-2.03........128.01
70.00......-1.13........128.91
75.00......-0.43........129.61
80.00.......0.08........130.12
85.00.......0.45........130.49
90.00.......0.69........130.74
95.00.......0.85........130.90
100.00......0.95........130.99
--
Generated with WinISD[0.44] freeware (C) Juha Hartikainen
You can download your own copy from : Link Removed

hbarcat said:

Box type : Closed
Box size : 5.3 ft^3 volume
Outside dimensions: 27"x30"x14

Click to expand...

I don't know if the program somehow determines the internal volume of the cabinet...but the internal dimensions are more like 4.8 cu. ft (25.5 by 28.5 by 11.5 in.) before you subtract the volume displaced by the four speakers (magnet assembly, cone volume, etc.).

The box is made from 3/4 in. plywood so you loose 1.5 inches on height and width. The baffle and rear panel are also made from 3/4 in. plywood plus the baffle is recessed at least 1 in. (so I removed 2.5 in from the stated depth).

I was saying the fbarcat modeled the response with too large of a cabinet volume. Once the true volume of the enclosure is known (aka 4.8 cu. ft - 4x volume displaced by each speaker), the calculations can be repeated.