Amp Recommendation For 2245H Subs

[svollmer]

Hello All,

I've been using a Crown Powerbase III amplifier to run my subs for years, but am looking to make a little change because of some new ancillary equipment. I've been very pleased with the PBIII, but it only accepts unbalanced inputs. I've always had a mild ground hum in my subs and I know it's from the long run of cable from my rack to the amp. I have a new preamp/crossover with balanced outputs for the main and sub channels. I'd like to get a new, but not too expensive, amplifier for the subs.

The current setup is 4 of the 2245H subs (2 for left channel, 2 for right channel) paralleled to 4 ohms per channel. My wish list for the new amp is:

Balanced XLR inputs
High damping factor
Decent power (>400 WPC at 4 Ohms)

I do not need any form of processing or crossover, etc. Just a good high-powered, high damping factor, stereo amp with balanced inputs. Something similar to the good old Crown K2 would be perfect!

Thanks!

[engineerjoe]

There really are a lot of choices. I think the best bang for the dollar would be a used Crown Macro-Tech amp w/ bal input card or even the Micro-tech. If you got the Micro tech series, don't think the inputs aren't balanced. My 2 Crown MT1200 have TRS inputs and are very quiet in my rack. I have only used them in commercial use. I think they'd be ideal to keep cost down. I may test them in the house now that I have a Denon surround receiver with preamp outs. I have balanced input jacks mounted on drilled out blank rack channels to convert the inputs. I used to use the Crown PSAIIs exclusively. Those were work horses that never let me down. Just way too heavy now days. Maybe good here?
There have been posts about fan noise as concerns on certain pro amps. I would house them accordingly.
I now have QSC amps too but haven't really tested them yet. I've heard good things. :D

[svollmer]

Thanks very much; I'll take a look at the specs on those. I did some searching on specs and found the Crown K1 and K2 have a DF of >3,000. My Powerbase III is >1,000. The Crown Studio Reference is >20,000! Holy Cow!

I also looked at some home amps. Adcom GFA-555 II is >800. The GFA-565 monoblocks (I have a few on the shelf) are >1,000. But, the Adcoms do not have balanced inputs.

Still open to more suggestions. :-) Or, maybe someone has a K2 for sale? :)

[BMWCCA]

A bridged-mono Crown PS-400 is rated at 660-WPC at 8-ohms. Don't see a 4-ohm spec in bridged mode, for some reason. Doubt it would be unstable at 4-ohms. Their damping factor is >400. I mention them because you can buy a Crown adapter for them to run balanced inputs, they don't have a fan, and they're quite economical to purchase and incredibly sturdy. I used one in stereo for the LF section of the 4345s.

I also have a Studio Reference-II acquired from Subwoof in a trade for a pair of JBL subs quite some time ago that I've never even powered up. Happy to supply it for you to try before you spend the coin they bring these days. 555-WPC stereo into 4-ohms. Damping factor listed as >20,000, as you have noted. Takes a standard 120v plug but I feared for the wiring in my old house and never tried it. Figured I'd use it with the 250ti pair I've never listened to, either!

Not quite sure how critical the high damping factor really is given the huge disparity among different quality high-powered amps.

Maybe another DC-area listening party at your place? Bring your own amps? :bouncy:

[svollmer]

Thanks Phil! You're always welcome over. Heather and a couple others are coming on the 27th. If you want to stop by, PM me.

Thanks for the advice on amps. The PS-400s sound promising!n

Well, I did a little research late yesterday and learned something new (and a little embarrassing :o:). The PowerBase series can be run balanced with a 1/4" TRS (tip-ring-sleeve) plug! I didn't even think about the possibility until last night. I checked the old manual online and confirmed it. So, I ordered a couple Neutrik NP3X 3-Conductor 1/4-Inch Phone Plugs which should arrive tonight. I'll put those on the amp end of the cables replacing my unbalanced TS plugs and then XLR plugs on the preamp end. Should work just fine, and for a whopping $8.00! :bouncy:

Crown did make an adapter for that series too (MT-XLR)so one could change from phono input to XLR. The manual implies that it should only be installed by a dealer. Have you installed one?

Thanks!

[BMWCCA]

Crown did make an adapter for that series too (MT-XLR)so one could change from phono input to XLR. The manual implies that it should only be installed by a dealer. Have you installed one?

No, the MOD-X or whatever they call the D and PS series adapter just plugs into the multi-pin jack at the back of those amps. I have several adapters I've acquired but haven't had a need for them over the past 20-years!

Thanks for the invite but we'll have all three daughters together in the new house, one who hasn't been here since before construction started and will now see the house I first promised her 31-years ago when she was two and we had just purchased the lot!

Happy Holidays to you all.
:tree:

[engineerjoe]

just for a test, try ground lifting the amp if it's in a grounded outlet. That may cure the hum.

[engineerjoe]

Oh and use a meter to test for any voltage between your neutral and ground on the outlets.
Many houses have bad wiring. Sometimes a good earth ground can be lost as well. Sometimes it stems from a poor wiring job anywhere in the building!

[svollmer]

Happy Holidays Phil; I'm sure it will be great having the whole family together in the new house!

Joe: I lifted the ground years ago and even have the amp plugged into a HumX to no avail. If I unplug the interconnects from the preamp, the hum stops. If I disconnect them from the power amp, the hum stops. So, I assume I'm picking up the hum along the way, which is only about 12 feet and near no power wires or other sources. Weird....

But, I'll definitely try the test with the meter. Maybe it will provide some insight. Thanks!

[dezmond]

Been using a Yorkville ap4040 for a pair of 4645's very happy with it.

[svollmer]

Thanks dezmond. I'll keep that in mind if my new connections don't work out.

[Mr. Widget]

Not to muddy the waters, but if hum is your problem and you want to keep using an unbalanced amp, you can use an isolation transformer. These stereo units from Jensen will not affect your signal in anyway, but will break the ground loop and you will have silence.

https://www.jensen-transformers.com/product/ci-2rr/

A lower cost option that will be fine for a subwoofer and probably good enough for any system that isn't using uber high end equipment is this solution from RDL. It is a single channel unit, so two are required for stereo.

https://www.bhphotovideo.com/c/product/290045-REG/RDL_TX_1A_TX_1A_Balanced_to_Unbalanced.html

Both of these solutions are professional broadcast grade pieces that will provide decades of trouble free service... and they do work!


Widget

[RMC]

Hi Svollmer,

Another less costly option to get rid of hum is the following from Rolls. Also more flexible connection wise. Regards,

Richard

8552785528

[svollmer]

W

[svollmer]

Widget/RMC:

Thank you for the great suggestions; they're very helpful.

I received the Neutrik balanced phono plugs in the mail today (I already have the XLR plugs for the preamp side). I'll try to get them on this weekend and let everyone know if running balanced does the trick. If not, I've got some great options for not having to replace my amp.

Thanks very much much to everyone!

[RMC]

Hi svollmer,

RE "... not having to replace my amp."

You don't replace a good amp for a hum problem. Never (unless you're really at the end of the rope).

Give yourself a nice gift for X-Mas and download a copy of Rane's "Sound system Interconnection", Rane note # 110, last updated 2015, from their technical library. (rane.com, then click Contractors, click Resources at top, choose FAQ & Support, from the Support Options click the second one i.e. link to "Knowledge base". Sorry if its long but Rane has changed over the years, though kept some of their good stuff).

Now you're in the land of those who know and have been at the forefront of settling most of those silly interconnection problems, such as hum. Have not posted directly the info since its copyrighted and I tend to respect that.

Scroll down slowly the Knowledge Base list and stop at the following: Pin 1 Revisited, open it, at bottom of text PDF available; Grounding and Shielding Audio Devices, do same as preceeding; Sound System Interconnection, this is the best and most practical one ever published, open doc and save as PDF at bottom of text. There's one or two others I have but you may not need them.

Keep a copy of Sound System Interconnection under your pillow, on the kitchen table, next to the Johns, wherever, and with all the proper connection schemes clearly illustrated, then former connection nightmares may well suddenly become nice dreams... Merry X-Mas! Regards,

Richard

[svollmer]

Merry Christmas!!!

I finally got the opportunity to install the balanced 1/4" TRS plugs on the amp end and the XLRs on the preamp end of the cables and (drum roll please!), NO HUM!!!! There's a very small "SHHHHHH" sound when close to the woofers, but no buzz or hum. So, my wife and I are thrilled and listened to a bunch of songs last night. Thanks so much to all for the advice and help.

Now for some fun: when searching around on 2245H speakers, I ran across this post from Steve Guttenberg about a PBN Audio speaker that has 2 JBL 12" mids and 2 JBL 2245H woofers. REAL expensive, but pretty cool. I wonder where they source new 2245H woofers?

https://www.youtube.com/watch?v=xZCLL1WsDpQ

Here it is at the PBN site: https://pbnaudio.com/mr-777at/

Check out the pictures on the bottom. If two speakers with 2 x 2245s isn't enough for you, PBN builds subwoofer columns with four 2245's!

Steve

[BMWCCA]

I love the comments from people who say they'd never buy $85,000 speakers with paper cones!

I'd probably never buy a $1,000,000 car with rubber tires, either. But that has nothing to do the the material used.

[Earl K]

I wonder where they source new 2245H woofers?

Thanks for sharing those links.

I suppose that maybe JBL will run a batch of whatever ( models ) as long as their minimum order is met.

I certainly don't like the reddish/purplish tone of the cones ( I'd be looking to dye them back in no time ).

It's great to see such a simplistic design concept can garner such praise ( that's my biggest take-away ).

I also love the fact that the large WMTMW concept works for those listening ( though there are endless numbers of people who can point out the reasons it won't or shouldn't > along the lines of why bumblebees can't fly ).

:)

BTW;
:happyh: :xmas::sleigh:

[Mr. Widget]

Thanks for sharing those links.

I suppose that maybe JBL will run a batch of whatever ( models ) as long as their minimum order is met.

I certainly don't like the reddish/purplish tone of the cones ( I'd be looking to dye them back in no time ).
Yes, thanks for sharing the links, and great news in eliminating your ground loop!

I doubt today’s JBL will agree to do a run of drivers with only 10s of thousands of dollars profit in it. They seem to be focused on larger markets and/or branding projects.

Regarding the purple cones, doesn’t it seem likely they are using JBL frames with aftermarket kits?

...and yes, Happy Holidays!


Widget

[Earl K]

Yes, thanks for sharing the links, and great news in eliminating your ground loop!

I doubt today’s JBL will agree to do a run of drivers with only 10s of thousands of dollars profit in it. They seem to be focused on larger markets and/or branding projects.

Regarding the purple cones, doesn’t it seem likely they are using JBL frames with aftermarket kits? Widget

I suppose that would make more sense.


On the other hand, all the pics that I can find of aftermarket kits show regular charcoal colored cones ( maybe those are just old pics and the purple color we are seeing is what's current ?? ).

https://pbnaudio.com/wp-content/uploads/2019/11/777.frnt_.rear_.bass-410px.jpg

:)