What's the difference between a Rel t/9 & T/9i?

db, before proceeding with either sub please read the posts by member taww in the following thread, especially the first of his posts dated 4-2-2018, that post beginning with "I have an AX-7e with a REL T-9 and it sounds great, but has some serious caveats...."

https://forum.audiogon.com/discussions/subwoofer-for-ayre-ax-7e

Regards,
-- Al

Thanks, Al. That post by taww and your first 4/1/18 post in that thread have given me pause about using any sub with the A7e. I was planning to connect the left and right speakers to L+L-R+R- block of the KEF 10b, but now I worry about damaging the A7e.

The current setup is balanced analog from an Ayre Codex in DAC mode to the A7e that drives a pair of KEF LS50s. I don’t perceive a need for a sub, given that the setup renders jazz bass very well, and I mostly listen to jazz and chamber music in the living room.

In another setup Ayre QX-5/20, KX-5/20, VX-5/20 drive KEF Reference 1s augmented by a pair of Velodyne HGS-15s with SMS-1 bass management. That can satisfy my lust for pipe organ recitals.

Is it safe to try the 10b if I connect only the left or right speaker? That is, connect to the L+L- or R+R- input of the block but not both. I had planned to add a second 10b if I liked the sound.

I suppose I could return the 10b to KEF.

db

I was planning to connect the left and right speakers to L+L-R+R- block of the KEF 10b, but now I worry about damaging the A7e.

Yes, that would definitely be a no-no.

Is it safe to try the 10b if I connect only the left or right speaker? That is, connect to the L+L- or R+R- input of the block but not both. I had planned to add a second 10b if I liked the sound.

As you’ve seen in the other thread what is probably the greatest concern in connecting a sub to the Ayre amp (either directly or via connections to the speakers) occurs if the two negative inputs of a single sub were to be connected to the two negative outputs of the amp. Depending on the design of the sub chances are that would result in the full amplitude signals on the amp’s negative output terminals for the two channels being shorted together.

However as taww and I explained you shouldn’t connect **either** of the negative input terminals of the sub to a negative output terminal of the amp anyway. (Doing that for one channel **might** work ok, depending on the internal grounding configuration of the sub, but it would violate the cautionary note in the amp’s manual that I quoted in the other thread and might degrade sonics or even cause damage). You would want to connect both negative input terminals of the sub to the amp’s chassis. It would then be safe to connect one positive input of the sub to the amp’s positive output terminal for one channel (or to the corresponding terminal on the speaker), and the other positive input of the sub to the amp’s positive output terminal for the other channel (or to the corresponding terminal on the other speaker). The single sub would then sum the signals for the two channels together, as is desirable when only one sub is used.

Connected in that manner the one remaining issue that is likely to arise would be, as taww explained, that when the amp is turned off the sub is likely to hum.

Good luck. Regards,
-- Al

Thanks, Al.  I'll try to return the unused 10b to KEF.  I'm happy with the sound of the Ayre A7e driving LS50s without sub augmentation.

Ayre stuff is tricky.  I inserted a supposedly balanced Bryston 10B high-pass filter between the KX-5/20 and VX-5/20 even though Charles Hanson had admonished me not to do it.  Of course he was right, some to the Ayre magic was lost and the sound deteriorated.  I removed the Bryston filter after hearing the result.

db

Hi db, both the T/9 and the T/9i can be connected to the Ayre A7e using the High Level input, though since the A7e is a balanced amplifier you will want to be careful to not connect the black wire of the REL’s high level cable to one of the negative speaker output terminals. Instead, the black wire can be left “floating”, or disconnected and with tape covering the copper end of the wire. If you experience hum, then the black wire can be connected to a chassis screw. Another option is to run an RCA cable from an unused output on the A7e to the .1/LFE input on the REL, then turn the .1/LFE Level control to minimum, which will provide a ground connection between the two. There is an article on the REL website which provides diagrams and a video for connecting high level to differential amplifiers like the A7e (https://rel.net/how-to-connect-a-rel-to-a-balanced-amp/).

As Al and users in the other thread mentioned, the other issue is that the A7e breaks connection with it’s output terminals when it is powered off. This is fine for your loudspeakers, but it causes the REL to hum if it is powered on and connected high level but the A7e is powered off. The best solution is to either leave both the REL and the A7e powered on at all times, or to power off the REL prior to powering off the A7e.

To answer your original question, both the T/9 and the T/9i are fairly similar, and their published specs are almost identical. The T/9i does have an improved filter and driver design, which gives it a more linear output when compared to the T/9, though both options will work great and pair very well with your LS50s.

My HT setup uses a Bryston SP3 processor, NAD M22 and C-268 amps, with six KEF LS50s.  One of its Velodyne HGS-10s needs repair, so I think I'll substitute the KEF 10b for it.  

Given how little traffic there is on the LA freeways now, I'm tempted to make the drive from Montecito (AKA Santa Barbara) to LA to drop off the 10 and a 15 for repair.  George Meyer claims to be open for business.  His shop repaired the other 10 and 15 last year.  I've used the HGS models with SMS-1 bass management for decades.

Hello, 
This might sound obvious, but can you talk to the manufacturers and let them tell you how to sort this out. I believe I saw a YouTube video about being careful using the Neutrek connection with certain amps. Something about putting too much load on the amp. From OCD Hifi guy- Warning about this connection. This guy is very smart when it come to hooking up multiple amps and speakers. The thread will continue and you will see what they are talking about. 

At least for REL subwoofers, the high level input is designed with a significantly high impedance so it will not place any current load on the amplifier. You do need to be careful when connecting the high level cable to different amplifier types, though this is because of the different grounding practices of the different amp designs. As long as you follow the correct high level connection method for your amplifier type (class a/b, class d, balanced/differential amplifiers, etc.) there is no risk of damaging the amplifier by connecting a subwoofer high level. REL's service department can provide specific high level connection instructions if you do not know what class your amplifier is.