Biwiring the monos -

Hi – apologies if this has been asked before but I can’t find mention of it via search function for this forum.

For those biwiring with the BHK monos, does it make a noticeable difference to use one amp per speaker (each mono amp driving one speaker fully) or to use one amp to drive the bass of each speaker and the other to drive the mids/uppers? I suspect the former is generally seen as the normal way but I wondered if anyone has tried the other way?

thanks – these amps are quite exciting from what I can determine. I do notice there’s slightly different rear pictures around (speaker terminal outputs are either separated to the sides or grouped into the center (as shown on the products page here). I presume this is just a slight change from early production?

If I understand the question properly you can only use one mono to power one speaker. They are “mono” amps so if you used one for bass and one for mid/treble you would be getting bass for both speakers from one half the stereo signal and the mid/treble for both speakers from the other half. Would be very odd sounding! To do vertical bi-amping you need two stereo amps (one dedicated to each speaker) or four mono amps (cha-Ching!).

I can see your confusion.

Lets see if we can make this simple.

Think of a system with a single stereo amp.

Lets say that amp has one set of speaker wire binding posts for each channel, left and right.

It is more complicated than this but, picture cutting the amp in half with a saw. Put one half by the right speaker and one half by the left. You now have mono amps. Of course now you need a separate power supply for each channel (one of the benefits and additional expense of mono blocks). But you still just have a single amp for each channel whether it is in one box (stereo) or two (mono).

Here is where the confusion may come in. Some speakers are designed to be bi-wired. One set of binding posts for the woofer/s and one set to a different crossover for the mids and tweeter.

Some manufacturers of stereo amps put two sets of binding post on each channel of the amp to make it easier to bi-wire. Even though there are four sets of binding posts there are just two amplifiers in the box. Cut it in half and you have two mono amps with two sets of binding post each.

Vertically biamping uses FOUR amplifying channels, two on each side. In order to do that with mono blocks you would need four individual boxes.

Does that clear up the confusion, or just muddy the waters?

Doc, I think you made it too simple, as there is nothing there. (I only saw your first post, when I started writing this.)

For the OP, you must use one amp for both high and low signals for one speaker.

What you are asking would only work if you had two stereo amps(2 - channel). You have mono amps (1 - channel).

So you take the right channel pre out and insert that into your amp sitting closest to the right speaker, run both cables from that amp to the right speakers two +/- connectors. Do the same for the left channel.

As to the pictures, I think you are looking at the back of the stereo version. Yes the BHK Mono 300s have two sets of speaker terminals in the center. The BHK 250 has two sets of terminals on each side, for the left and right channels.

The reason your amp has two sets of terminals is so you can biwire a speaker with two separate sets of cables. If you have biwire cables with just two connectors on the amp side and four on the speaker side, just hook up to one pair, red/+ to one of the positive/+ terminals, and black/- to the negative/- terminal.

Either pair will do, as they are both connected the same way inside the amp.

Does the above make sense?

Oops yes, sorry, brain burp. I have a pair of monos that can be used as individual stereo amps so I was projecting from there. Too much excitement over the BHK300s most likely. Thanks for bringing me back to my senses :slight_smile:

Re the amp type – I saw a listing on A’gon today for the 300 monos and the rear pic, which is clearly of the mono model, looks a little different – not clear how to put the pic here but check out this link:


I am sorry it took so long to get all the post/s up.

Unfortunately I have developed a neurologic problem with my right hand (I am right handed) and my rather slow typing skills have degenerated to left hand only typing, so the process of responding is quite lugubrious.

Thank goodness I can still think A LOT faster than I type.

Doc, no need to apologize. I just saw the first post and thought you meant to put in a link, or a chart, or something. I liked the sawing stereo amp in half.

Patrick, I see what you mean, no idea, Paul will probably have to answer that one. Anyone know why there are two different back plates on the BHK 300.

My mono’s have two sets of binding posts - one on either side of each amplifier - Either set work so I assumed that this was to make it easier to connect speaker cables. I now suspect it is an earlier back-plate set-up.

Mine are the same, and mine are relatively recent. Like the picture in the Audiogon link that @patrick47 posted above.

The picture from the product page is not what mine look like.

palerider said Mine are the same, and mine are relatively recent. Like the picture in the Audiogon link that @patrick47 posted above.

The picture from the product page is not what mine look like.

just saw the link picture - my backplate layout is the same as the picture in the link. Same as Palerider.

Maybe it’s the pic on the PSA site that is out of date?

This very concept/question is why I’m planning to buy a pair of 250s and park one next to each of my two speakers. I’ll continue to drive the lower-frequencies (thru 70Hz or less than two octaves of the 10-octave audible band) with one channel and the eight-tenths of the audible band with the other channel. Since I don’t have the amps, I don’t yet know how I’ll drive two channels with one signal cable, but, at worst, I’ll simply use a signal splitter such as the AQ RCA version at the left of the pic. I believe strongly enough in biamping that I modified my Vienna Acoustics Mahlers by snipping the jumper from the inside of the single pair of binding posts to the bass-filter board and then adding a separate 8-1/4g. cable of inexpensive, 16/4, stranded ‘speaker cable’ to that bass board and then all the way out the speaker thru the lower reflex port. Works VERY well.


The multistrand cable is Clear Day six-conductor (per pole) solid-silver stuff; that too sounds excellent.

More on the bass cables.

I buy this 16/4 speakercable at Home Depot; it costs about 43 cents (including salestax) per foot on a 500’ reel*. Of course, doubling the number of electrical conductors increases the AmericanWireGage by 3, so combining two 16s makes a 13, and combing two of those 13s makes a 10. So using two of these 16/4 cables makes a 10g-per-pole cable, which is what I’ve done for my Revel C208 centerchannel speaker. For the Mahlers, I added a third 16/4, splitting its four 16s equally between the cable on the two poles. Using an AWG chart including resistances of conductors and a resistors-in-parallel website, one can then calculate the approximate gage number. Six 16g. conductors turns into c. 8-1/4g. So as not to alter the exterior of the Mahlers, I soldered those cable ends directly to the bass-crossover boards (after snipping the original wire running from the binding posts to the x-over board) and ran them out of the speaker thru the bottom bass-reflex ports. I added a half-inch flexible jacket and terminated it with AudioQuest silver-over-copper 5/16" spades.

  • I bought a reel when I started running four pairs of it ‘all over’ the musicroom for the new surround, rear-surround, ceiling-mid, and ceiling-rear speaker pairs (all ELAC B6s). My SIL is now cabling his surround speakers with that same reel of cable.

Fascinating approach — I used to have a pair of amps that ran in stereo or could be bridged for mono, and ended up preferring the bridged mono set up. Then again, I was not using an active crossover. I like your cable approach however, and at the risk of muddying waters again, can anyone speak to the likely impact of doubling up the speaker cable runs on the monos. What I have in mind is using both sets of terminals on each mono to run a pair of extra cables to each speaker. Note, my speakers are already biwired using speakers cables that are joined at the amp end, separated at the speaker side, so obviously I use one of the mono amps speaker terminals currently. What I am wondering is if anyone has tried driving speakers using two pairs of cables per speaker for each mono amp, using both the mono speaker terminals to feed the same speaker.

Am sure this was mentioned somewhere on the forums as worth trying but I can’t find a specific thread on it. Apologies if it’s a well-worn topic. Jeffrey’s post above, speaking to the use of multiple cables, just got me wondering about this…likely I’ll try it with some affordable extra cable anyway if it’s doable without causing a problem (can’t see how it would be?) but wanted to check for others’ experiences of this type of connection.

Patrick, the vertical bi-amping approach you originally mentioned would work great with a BHK 250 for the highs and a pair of BHK 300s for the lows.

Now listening through the BHK-250 (and enjoying them immensely) and having read reports of the improvements of the 300 monos over the 250 stereo, I suspect IF one was limited to a pair of 300’s and a 250, they might do better with the 300s on the mids-highs and the 250 on the bass. AND if they had separately powered subs, this would likely be an even stronger setup.

Of course, most buying a pair of 300 monos and considering adding a 250 would be better off with another pair of 300 monos for this configuration.

Greg in Mississippi